Optometry Essentials Study Guide a Resource for Student and Pre-Registration Optometrists

Optometry Essentials Study Guide A resource for student and pre-registration optometrists

2021-22 Optometry Essentials Study Guide

Introduction

Specsavers' Optometry Essentials is the go-to guide for student and pre-reg optometrists – wherever you work.

Focused on the College of Optometrists’ Scheme for Registration and your future evolution as a professional, it is the product of decades’ worth of study notes and insight from students, supervisors, assessors, examiners, practising optometrists and educators.

Designed to complement your academic studies and practical work in-store, this comprehensive handbook provides the foundations you need to be successful in your assessments and in your career as a frontline eyecare practitioner.

As well as up-to-the-minute clinical, practical and professional guidance, there are handy hints, reflective activities, and links to other useful resources and websites.

By sharing our experience and expertise, we hope to make your training period as positive and productive as possible – and help you become the best practitioner you can be.

Because that’s good for you. It’s good for the profession. And it’s good for patients.

How to navigate around Optometry Essentials

This navigable guide is organised into three sections and nine chapters. When viewed on-screen, click on any heading or sub-heading in the table of contents to go straight to that section. To go back, click on one of the headings at the top of the page e.g. < Binocular vision

Section A Section B Section C

Professional Clinical case Optical appliances assessment and management of and refractive record keeping ocular conditions management

> Patient records and communication > Binocular vision > Visual impairment > Clinical refraction > Ocular disease and abnormality > Contact lenses > Ophthalmic investigative techniques > Use of diagnostic and therapeutic drugs > Spectacles and protective eyeware

Your pre-registration period with Specsavers

As the leading employer of pre-reg optometrists in the UK and Ireland, we are dedicated to helping you succeed in your pre-registration period (PRP) and beyond. Accept one of our 500 pre-reg placements, and you’ll receive the individual support of a practitioner-owned optical practice with the opportunities and professionalism you’d expect from a global company. Super supervision As well as being recognised by the College of Optometrists, our supervisors undergo in-house professional development to hone their coaching and mentoring skills. You’ll also benefit from working with a highly trained store team, and regular contact from our dedicated pre-reg team. Speak volumes Joining a community of hundreds of other Specsavers pre-reg optometrists means you'll never feel like you’re on your own. Plus, with access to the UK’s largest and most varied customer base, you’ll have no problem achieving your portfolio requirements for patient numbers. Interactive learning As well as your in-store induction and day-to-day learning, you’ll benefit from our unique optometrist development programmes focused on career, ambition and achievement, starting with our Pre-Reg Academy. You’ll also have access to our world-class CET programme and clinical conference events. PRE-REG EXCEL ASCEND ACADEMY career • ambition • achievement career • ambition • achievement HIGHER Excel – an interactive CET career • ambition • achievement Pre-reg Academy – a accredited workshop, which comprehensive series of Ascend Higher – a 3-point celebrates your achievement residential and on-line CET accredited workshop for at the end of the Scheme for courses across the year, led GOC registered Registration. After this and delivered by expert optometrists. This is devoted course you’ll be able to tutors, clinicians, assessors entirely to you and your transition confidently into and examiners. Preparing continual development after the next stage of your you for every stage of your qualification. career as a registered assessment and OSCE to optometrist. help you achieve and demonstrate continuing conscious competence. You’ll benefit from shared experiences every step of the way.

...continued

Straight to the top

Every Specsavers store is locally owned and led by its directors, usually an optometrist and a dispensing optician or retailer. Which means you get to know the directors personally – the optometrist director may even be your supervisor. Online professional network

You can participate in clinical conversations and connect with thousands of experienced optometrists via our unique online network on Yammer. Easily accessible on your phone or tablet, there’s even a group just for pre-reg and newly qualified optometrists. Embracing technology

Specsavers has lead the way in bringing hospital grade equipment to the high street with the rollout of optical coherence tomography (OCT) in every store and a comprehensive training programme to back it up. Which means you will have the very best diagnostic equipment at your fingertips. Advancing optometry services

We're also actively engaging with every enhanced services scheme available across the UK and working with ophthalmology through investment in partnerships with ophthalmology providers such as Newmedica. As soon as you are qualified, you can be accredited to work in enhanced services. Indeed, you will be doing your Level 1 WOPEC accreditations as part of the PRP. Continuous development

With so many development opportunities open to you, it’s an exciting time to be a Specsavers optometrist.

Study for higher qualifications. Become a supervisor or WOPEC assessor. Work in a Newmedica specialist eye clinic. Volunteer for a charity. Or begin the pathway to own your own store as a joint venture partner – an opportunity unique to Specsavers. Do any or all of the above. The choice is yours. Let’s talk...

Got any questions? Looking for opportunities with Specsavers?

Contact our pre-reg team. We’d love to hear from you.

Email: [email protected] Web: jobs.specsavers.co.uk

Section A

Professional assessment and record keeping

> Patient records and communication > Clinical refraction > Ophthalmic investigative techniques

< Patient records and communication

Patient records and communication

1. Core topics...... 7

2. Introduction...... 7

3. Key issues: completing patient records in practice...... 8 3.1 Symptoms and history...... 8 3.2 Ocular examination...... 9 3.3 Supplementary tests and examinations...... 10 3.4 Prescription advice...... 10 3.5 Clinical decisions/advice given/dispensing details...... 10 3.6 Follow-up...... 11

4. Key issues: law...... 11 4.1 NHS funded examinations...... 12 4.2 Private eye examinations...... 12 4.3 Referral criteria...... 12 4.4 Driving standards...... 12

5. Key issues: communication...... 13 5.1 Taking a medical history ...... 13 5.2 Approach to clarify symptoms...... 13 5.3 Explaining your findings ...... 14 5.4 Patient resources...... 14

< Patient records and communication

1. Core topics

• Patient records • Law • Communication

2. Introduction

Clinical records are an essential part of all clinicians' practice. They provide a record of what the patient said, what tests were performed, what was found, your conclusions, advice and what the patient consented to. This record enables continuity of care, aids another optometrist to take over the care of the case and provides evidence in case of a complaint or legal action. First and foremost, the clinical record is there to help the clinician and the patient, whilst always remembering it is a document which carries many unique legal obligations.

You must seek a patient’s permission for the use of their records for assessments. You should stress that any information will be anonymous and treated in the utmost confidence. This verbal consent must be annotated on the patient’s record (for computerised records, this should be noted in the same place every time e.g. Advice given/Action taken box). The patient does not need to sign. Gaining consent is particularly important for student optometrists and pre-registration optometrists under the supervision of a qualified optometrist.

Tip: Know what you would do in the scenario where a patient does not give you consent.

The records that you present to your assessor must be genuine patient records. There have been instances in the optical press of trainees creating false evidence for their assessments. Such activity would lead to a College and GOC investigation.

Under no circumstances should anyone attempt to change, amend or add to the records. Such action would be taken very seriously and may be reported to the GOC.

The College has the right to recall any of the patient records completed by the trainee during the pre-reg period. As such, it is imperative that you complete each and every patient record with care and consideration, in order to: a. satisfy the College should they wish to review some of your records b. ensure your documentation would withstand legal scrutiny Consent

• Consent should be recorded on the clinical record where appropriate. • In order for consent to be valid it must be given voluntarily, by an appropriately informed person who has the capacity to consent. • You must respect the rights of patients to be fully involved in decisions about their care. • You must obtain consent from patients who have capacity before starting the examination. • You must work on the presumption that every adult patient has the capacity to make decisions about their care, and to decide whether to agree to, or refuse, an examination, investigation or treatment. If you do not believe a patient has capacity for a particular decision you should record it on the record card.

< Patient records and communication

• There are two types of consent: explicit and implied. Patients can give explicit consent orally or in writing. They may imply consent by their behaviour, such as resting their chin on the chin rest after you have explained the procedure.

• Obtaining valid consent is part of an ongoing discussion; it is continuous. The patient has the right to withdraw consent at any point.

• If a patient does not have capacity but attends with someone who has legal authority to make decisions on their behalf, you should record the evidence you have seen and the name and contact details of that person on the record card.

• You are unable to complete a sight test for a patient who refuses to consent to you completing a clinical record of their sight test. 3. Key issues: completing patient records in practice

3.1 Symptoms and history

The clinical record must include the date and patient identifiable details, which would normally include the patient’s name, date of birth, address and contact information. You may allocate a unique identifiable number to each record. You should not include superfluous information on the record card. The record card should be clear, comprehensive and easily understood by another practitioner in the future, which means the record card needs to be legible, ideally typed in a uniform practice template.

You would normally include the following information. (This list is not exhaustive.)

• Reason for their visit

• The appointment type: is it for a sight test or another kind of enhanced service, clinical consultation or supplementary assessment?

• All symptoms, using the words as described by the patient and their duration

• Their ocular health; whether the patient has ever attended an eye clinic or had eye surgery

• Current general health, including conditions such as diabetes or systemic hypertension

• A list of current medications, eye drops and supplements used

• Family ocular and general history

• Summary of the patient's visual requirements, occupation and leisure activities which require optical consideration

• Information about driving, including type of licence (i.e. private vehicle, HGV, motorcycle etc) and whether spectacle correction is required for driving

• Date of the last sight test, and any key recommendations from that, if it is the first time the patient has visited your practice

• Previous and current optical appliances used

• Whether the person is affected by headaches or migraines (use LOFTSEA mnemonic if needed)

• Whether they are affected by any ocular symptoms such as sore eyes, diplopia, flashes of light, visual aura, afterimages or floaters. (If they do, their onset, duration, triggers and nature)

< Patient records and communication

3.2 Ocular examination

Record the results of all of the tests completed so that your findings and methodology are clear. As a minimum this would normally include:

• Unaided vision

• Vision with each pair of current spectacles worn

• Results from ocular motor balance for distance and near, recording the method and further assessments

• Slit lamp findings for every structure assessed for each eye

• Ophthalmoscopy findings with every structure assessed for each eye

• State how the assessment was conducted and whether a mydriatic was used.

• Include diagrams, photographs, OCT’s and imaging as required. (these form part of the clinical record even if stored elsewhere)

• Diagnostic drugs: record the name, time instilled, expiry date and batch number (complete College leaflet with relevent details of drugs used and note this has been given to the patient)

• Optional findings where clinically indicated

• IOP readings

• Visual fields examination (Ideally the output printout/ PDF. Alternatively, full results, type of test, correction worn, reliability observations and indices)

• Other imaging

• Pupil reactions

• Ocular motility

• Near point of convergence

• Amplitude of accommodation

• Colour vision test

• Stereopsis test results

Refraction results (both subjective and objective)

• Final subjective refraction

• Where appropriate, record back vertex distance and understand the significance of a change.

• Record pinhole acuity where appropriate.

• Note all binocular balancing amendments and know their significance.

• Where appropriate, record a +1.00DS blur and understand the implications of the result.

• Distance visual acuity at each relevant stage

• Reading addition with VA and working distance as indicated

• Oculomotor balance where clinically indicated

< Patient records and communication

• Fixation disparity where clinically indicated

• A final spectacle prescription given, along with your recommendations for its use and any other relevant notes for dispensing. 3.3 Supplementary tests and examinations

When the following are used, record and understand the significance of the results:

• Tonometry. In addition to the measurements and average, note the instrument used, any drops used and time of day.

• Visual field assessment. Attach the records.

• Slit lamp assessment. Include a note of any specific drugs or preparations. Understand the details of viewing and illuminating techniques.

• Colour vision assessment. Record the test used and the lighting conditions as well as the results.

• Cycloplegic examination. Records should include reason for using cycloplegia, the drops used, their concentration, the number of drops instilled, pre- and post-cycloplegic data and final prescription. You should also record the time of instillation and the time when the tests were carried out. Don’t forget to record drug details and test results in red if it is a paper record. 3.4 Prescription advice

Record details of the distance/intermediate/near correction advised. 3.5 Clinical decision/advice given/ dispensing details

A) Clinical decisions

1. Refractive findings

These must be consistent with other record details, and any reasons for amending the findings should be given. Document any reasons for either changing or not changing spectacles, as appropriate.

2. Referral

The information recorded should be complete and in the required form. Ensure the information in the referral/notification is accurate and consistent with the record. Each letter should be typed or completed using a local template; you must tell your patient why they are being referred and how quickly you have requested for them to be seen. You should give them a copy of your referral letter, at the time of the referral. You must have consent from your patient to send a referral; if they refuse consent you must respect their decision. Each referral letter should broadly contain the following information:

• Patient name, date of birth, and contact details

• The reason for referral and to which specialty clinic they need to be directed

• The level of urgency: routine, urgent or emergency same day.

• Duration of the patient’s symptoms

• Relevant clinical information on examination

• Relevant family history or other risk factors

• Your name and contact details

< Patient records and communication

Generally emergency referrals are only required where the patient’s sight or life are at risk without an immediate intervention. Where possible try and speak with the on-call ophthalmologist or a more experienced colleague before making an emergency same day referral.

A list of conditions considered emergency referrals can be found here

3. Alternative management

Where alternative arrangements are to be offered, ensure that these are well documented, e.g. contact lens fitting, orthoptic training. Where any alternative management is not supported by evidence you must inform the patient so they make an informed decision as to whether to consent to your recommended treatment.

B) Advice

Your comments must be clear, concise and unambiguous. Advice must be consistent with the original presenting problem, and appropriate to the patient’s hobbies or occupation. Remember to consider contact lenses, when appropriate, as an alternative to spectacles.

C) Dispensing

Ensure the dispensing details are accurate and consistent. Know your dispensing options and if no dispensing is advised, understand the implications. Know your legal responsibilities when dispensing.

Refer to the relevant section in the College of Optometrists guidance for professional practice. Don't forget that the College of Optometrists' members-only app also contains the guidance for professional practice.

3.6 Follow-up

Wherever possible include follow-up information, e.g. results of referral or early retest. 4. Key issues: law

You must have a basic understanding of general law as it affects professional practice, e.g. consent, capacity, medicines, confidentiality, data protection, medical records, and the Opticians Act to name but a few. In addition, you should be aware of the various commercial regulations and laws relating to advertising contracts, negligence, consumer protection and producing goods.

There are variations in both the law and the NHS contract in England, Scotland, Wales and Northern Ireland. It is important you refer to guidance appropriate to where you are practising.

See the GOC Standards of practice

See The College of Optometrists guidance for professional practice.

< Patient records and communication

4.1 NHS funded examinations

Make sure you find out what the NHS funds by way of consultations where you are working, e.g. General Ophthalmic Services sight tests in England, Wales and NI, and NHS eye examinations in Scotland. Compare and contrast this to enhanced optical services such as Eye Health Examination Wales, LOCSU commissioned services in England and the equivalent in Northern Ireland or supplementary tests in Scotland. The contracts for these services would specify what the consultations should contain, patient eligibility, frequency, recall and management outcomes. 4.2 Private eye examinations

Private consultations are always an option where an NHS commissioned service does not exist. The content of private examinations is down to the clinician's judgment and the application of guidance. Find out which services are available as private eye examinations or clinical services in your place of work. Examples may include emergency presentations for minor eye conditions, dry eye consultations, misdirected eye-lash removal for trichiasis etc. 4.3 Referral criteria

Be aware of the difference between private and NHS arrangements: you are contracted to comply with the terms of service for NHS work, but you do not have to comply with NHS terms for private patients. The GOC requirements prevail for private patients. In essence, your responsibilities in both situations are the same, but the NHS is a contractual requirement and the GOC is a legal requirement. Note that you cannot ignore your legal obligation in fulfilment of a contractual obligation.

Know the referral/notification requirements under your terms of service with the NHS. 4.4 Driving standards

The law requires that all licensed drivers meet the following eyesight requirements (including drivers aided by prescribed glasses or contact lenses):

• In good daylight, able to read the registration mark fixed to a vehicle registered under current standards

• At a distance of 20 metres with letters and numbers 79 mm high by 50 mm wide on a car registered since 1 September 2001.

• The visual acuity must be at least Snellen 6/12 with both eyes open or in the only eye if monocular.

The law also requires all drivers to have a minimum field of vision: The minimum field of vision for Group 1 driving is defined in the legislation:

• A field of at least 120° on the horizontal measured using a target equivalent to the white Goldmann III4e settings.

• The extension should be at least 50° left and right. In addition, there should be no significant defect in the binocular field that encroaches within 20° of the fixation above or below the horizontal meridian.

Group 2 bus and lorry drivers require a higher standard of visual acuity in addition:

• A visual acuity (using corrective contact lenses where needed) of at least:

• Snellen 6/7.5 (Snellen decimal 0.8) in the better eye and Snellen 6/60 (Snellen decimal 0.1) in the poorer eye

< Patient records and communication

• If glasses are worn to meet the minimum standards, they should have a corrective power not exceeding +8 dioptres in any meridian of either lens

For further information for medical professionals when assessing drivers with visual disorders, visit the government website: https://www.gov.uk/guidance/visual-disorders-assessing-fitness-to-drive

For advice about what to do if a driver continues to drive against your advice visit the College of Optometrists' guidance website. 5. Key issues: communication

5.1 Taking a medical history

Communication is the cornerstone of our interaction with patients and is essential to the current practice of optometry. The importance of good communication in our work with patients cannot be underestimated. An effective exchange between practitioner and patient helps us understand what the patient thinks or how they feel so that we may understand them better.

An open question is typically used to start the case history as this invites the patient to tell you about their problems with their vision. Bear in mind that patients often have relatively little knowledge about the eyes and eye disease. This can make it difficult to articulate their experiences and gauge if a change in their eyes really constitutes a problem which needs to be reported right at the outset of the consultation. Rather than opening with “What is the problem with your eyes?” consider asking patients what they notice or feel about their vision; this acknowledges that the patient’s experience may be entirely subjective and limited in expertise. “Are you concerned about your eyes or vision at the moment?” avoids this but may prompt a yes/no response which requires a further question. If the patient has requested an urgent appointment, you can assume that the patient has perceived there is an issue to be addressed and so once you have introduced yourself, opening with “How can we help today?” does three things: it recognises that there is a concern, it indicates straight away to the patient your intentions are to assist them and finally it invites the patient to tell you why they have sought an appointment. 5.2 Approach to clarify symptoms

Once the patient has offered the reason why they are attending, a series of follow-up questions are required to expand on the presenting symptoms and take a wider medical history.

When posing follow-up questions, practitioners can broadly take two approaches. The first is a list-based approach whereby a series of questions is posed matching the order of either the practitioner's mental list or taken from the patient record. This will ensure all of the questions are asked but patients may be confused, perceiving them as a series of unconnected and perhaps disjointed questions. We have all undoubtedly used this format at some point; “Do you have headaches?” followed by “Do you get double vision?” would be common questions.

The second approach is to connect the questions using interlinking words. “Tell me about your general health?” followed by “Okay then, and do you have headaches?” This subtle yet important difference gives the impression that the various questions are building up an overall picture of the patient's status and that the patient is central to that process by witnessing it in action. In a more complex way, questions can build on the patient’s previous answer. Questioning in this way also takes on more of a conversational tone, putting the patient more at ease, encouraging further dialogue and giving opportunities to display empathy but does takes considerably more skill to ensure all aspects are covered.

< Patient records and communication

LOFTSEA approach to systematically explore a specific symptom Location – Which eye is affected? Is the headache located in a particular area of the head? Where in the vision do you see the flashing lights? Onset – How did you first notice the blurred vision? How long have you had this irritation? When did the double vision start? Frequency – How often does the eye water? How often do you have these headaches? Any particular time of day? Every day? Once a week? Type/severity – When you see double, are the images side by side or one above the other? Did the blurry vision seem to happen all of a sudden or come on gradually? Self-treatment and its effectiveness – Does anything relieve the irritation /pain? Effect on Px – Has the eye pain awoken you from sleep? How have you coped with the blurred vision? Have you seen your GP about the headaches? Associated or secondary Sx – Is anything else happening at the moment? How are you feeling otherwise? Do you have any other symptoms you are concerned about?

5.3 Explaining your findings

Once you have completed your examination it is absolutely essential to clarify in your mind your recommendations and course of action before discussion with the patient. Calmness and confidence when explaining your findings will transfer to the patient. Use jargon-free explanations and allow plenty of opportunity for the patient to ask questions. 5.4 Patient resources

It is always useful to provide patients with written literature to support your findings and recommendations. Trusted links and online resources can also be shared. Patients will increasingly investigate their health online; providing links to trusted sources will help ensure they have access to the most helpful and reliable information.

< Patient records and communication

Handy Activities Reflective Exercises

• Watch the College webinar on consent • Audit five of your record cards against in practice the Quality in Optometry audit tool.

• Read the Acuity article on writing a • Video record a practice eye good referral letter examination with a work colleague on your phone, watch it and appraise your • Read the ProFile magazine training on communication skills. communication skills • Role play asking questions about a • Watch the College webinar on work colleague's headaches. Did you completing referrals cover all of the LOFTSEA points? • Create a list of useful links of trusted • Complete store training on how to information on a variety of common share clinical information with another topics that you can share with your practice patients when clinically indicated • Complete the College of Optometrists' • Download the College of Optometrists' audit training on retinal photography guidance app and review the section on record keeping, consent and • Practise completing an eye examination confidentiality with a colleague on a blank sheet of paper. How easy was it? Did you miss • Download the 'NHS safeguarding guide' out any sections? available as an app. It contains all the information you may need to refer to and the local contact details of every child and adult safeguarding team in England.

< Clinical refraction

Clinical refraction

1. Introduction...... 17 1.1 Assessment as a pre-reg...... 17 1.2 Preparation...... 17

2. Core topics...... 18

3. Key issues: route eye examinations...... 19 3.1 History and symptons...... 19 3.2 Preliminary examination...... 19 3.2.1 Unaided acuity...... 19 3.2.2 Cover tests...... 19 3.2.3 Gross perimetry...... 20 3.2.4 Pupillary distances...... 20 3.2.5 Ocular motility...... 20 3.2.6 Pupil reactions...... 20 3.3 Retinoscopy...... 21

3.4 Subjective...... 22

3.4.1 Fan and block...... 22

3.4.2 Cross cyl and duochrome...... 22

3.5 Distance oculomotor balance...... 23

3.6 Near vision assessment...... 23

3.6.1 Presbyopes...... 23

3.6.2 VDU users...... 24

3.7 Slit lamp examination and ophthalmoscopy...... 24

3.7.1 External eye and ocular adnexa...... 24

3.7.2 Media...... 24

3.7.3 Fundus...... 24

3.8 Supplementary tests...... 25

3.9 Final prescription and advice...... 25

< Clinical refraction

1. Introduction

1.1 Assessment as a pre-reg

As part of the College of Optometrists' Scheme for Registration you will have to perform a full routine eye examination assessment at stage 2 during which you should expect to examine one presbyopic patient who will be provided by the College. As you read this section, it is worth reflecting on how stage 1 and stage 2 assessment in the Scheme for Registration sounds like it differs from any similar assessment you might have had as an undergraduate. 1.2 Preparation

Remember patient safety and continuous competence are your priorities. Have you been utilising all your skills and maintaining your competency between assessment events? Are you fit to practise independently? Can you carry out appropriate tests and draw the relevant conclusions from the results? Reflect on this: would the examiner be happy to employ you or have you as a colleague in practice and in their absence?

< Clinical refraction

2. Core topics

• History and symptoms

• Preliminary examination

• Visual acuity unaided

• Pupillary distances

• Retinoscopy

• Subjective refraction for distance and relevant near add(s)

• Acuities for distance and near

• Oculomotor balance for distance and near, e.g. cover test and fixation disparity tests

• Ocular motility

• Pupil reactions

• Anterior segment and posterior segment examination

• Fundus images

• Tonometry

• Gross perimetry and visual fields

• Final spectacle prescription, overall management advice and routine recall recommended

< Clinical refraction

3. Key issues: routine eye examinations

3.1 History and symptoms

A full and detailed history and symptoms is the As a bare minimum, history and symptoms important beginning of a patient consultation. At must cover: the end of history and symptoms conversation, • reason for visit you should have a good idea of the patient’s • visual symptoms (visions distance and reason for visit, any symptomatic problems, near) any visual disturbances (flashing their probable refractive error (are they a lights, diplopia, etc) hyperope/myope/presbyope?), known ocular and general health issues, their exposure to • ocular history (Rx present, past, when relevant risk factors and the specific issues to be worn, effectiveness) addressed in your examination. The information • general health (medication, name, dose, from this conversation should all be recorded duration of treatment) accurately as discussed elsewhere in this guide. • family ocular history Remember to include questions on any smoking, contact lens wear, occupation, visual needs at • family general health work and outside of work, exposure to UV light, • occupation current/recent spectacle wear and lens type (single vision, bifocals, varifocals, etc.) which may • driver or not influence your final prescription. Also make a • specific visual requirements mental note of the patient’s race and age, as your knowledge of risk factors associated with either can influence any comments you may make on further investigation, e.g. suggesting pressures and fields on people of Afro-Caribbean origin at an earlier age than usual. 3.2 Preliminary examination

This could include: visions, cover tests, perimetry by confrontation, interpupillary distances, pupil reactions and ocular motility.

3.2.1 Unaided acuity

Ensure that you completely cover the non-seeing eye with an occluder.

• Record monocular and binocular unaided acuity; if the acuity is less than 6/60, move the patient closer to the distance vision chart and then seat them and move on to a near acuity as below

• It is also a good idea to check the near visions; if the patient can see small print at near in the presence of poor distance acuity this will imply that they are myopic and measuring the furthest near point that they can read N5 will enable you to have an insight into the prescription.

NB If the monocular vision is better than the binocular vision, suspect a binocular vision problem.

3.2.2 Cover tests

Use an appropriate accommodative target, which can be seen by the eye with the worse vision.

• Do a cover/uncover test to determine the presence of a phoria or tropia, then an alternating cover test to determine the magnitude of the movement.

(A rule of thumb for estimating movement is 1mm of movement is equivalent to approximately 7 degrees).

< Clinical refraction

• If you see a phoria, note the speed and quality of the recovery movement as this gives an indication of whether or not the phoria is compensated.

Remember that cover test is more meaningful if carried out with the patient's appropriate refractive correction (contact lenses or specs) in place so you could always be more efficient and effective by doing it after refraction rather than as a preliminary test on an unaided patient.

3.2.3 Gross perimetry

Gross perimetry describes both confrontation (comparing your monocular field with the patient) or assessing peripheral fields involving moving the target in an arc centred on the patients eye 33 cm from the patient, when used correctly, can be a very sensitive test and a useful skill to have. It is no longer necessary to perform this in the routine eye examination. If, however, the patient reports symptoms which suggest that this test would be useful, then its inclusion would be indicated.

Give clear instructions to the patient; ask them to maintain their fixation on your fixed target (finger or eye).

• Ask them to tell you when they are first aware of the second target and if it ever disappears as you bring the target to the centre of the field. The second target should be an appropriately mounted hatpin/wand.

• Always come from non-seeing to seeing, maintaining an arc at approximately 33cm from the patient.

Perform at least eight of these arcs to assess the principal meridians. It is tempting to omit this section, but where else in your routine do you assess peripheral fields? The normal field for a 5mm diameter white target at 33cm is 100˚ temporal, 80˚ inferior, 60˚ nasal and 60˚ superior.

3.2.4 Pupillary distances

Measure and record distance, near and, if appropriate, intermediate pupillary distances. Take care to avoid errors due to parallax.

3.2.5 Ocular motility

Use a pen torch with an exposed bulb so that the corneal reflexes can clearly be seen at the limits of ocular excursions.

• Initially observe the corneal reflexes in the primary gaze direction for symmetry: the Hirschberg reflex.

• Then perform a normal motility test. Instruct the patient carefully, e.g. ‘I want to check the muscles that move your eyes around, so please keep your head still and follow the light. Please tell me if the light goes double, or if you experience any pain or discomfort.’

• Use either the H pattern or the Union Jack pattern to check motility and watch the corneal reflexes to observe objectively any slip. Watch out for the common ‘A and V’ syndromes and don’t take the torch out too far (you are assessing motility, not perimetry). At 40cm, a 20 to 25cm excursion is considered sufficient to locate muscle over- or under-actions.

• If diplopia occurs, investigate with appropriate cover tests to identify the affected muscle.

The affected eye always sees the furthest image.

The muscle actions can be worked out from figure 1.

< Clinical refraction

Right eye Left eye

SR IO IO SR

Key: LR MR MR LR SR superior rectus LR lateral rectus SO superior oblique IO inferior oblique IR SO SO IR IR inferior rectus MR medial rectus

Figure 1

3.2.6 Pupil reactions

• Initially examine the pupils in slightly reduced illumination. Are they round, equal in size, of a size consistent with the patient’s age?

• Measure the pupil diameter, then check direct and consensual reflexes.

• Instruct the patient to fixate a distant target, then bring a strong light source (pen torch or ophthalmoscope) from below the patient to shine directly into the eye - this avoids stimulating the near response.

• Check direct and consensual reflex three times for each eye; there should be no signs of fatigue.

• Perform a swinging flashlight test to check for an afferent pupillary defect.

• Check the near pupil reflex by getting the patient to change fixation from distance to near and observing the pupil reactions.

• Grade all pupil responses and record. 3.3 Retinoscopy

Fit the trial frame to the patient comfortably and set the correct PD. Explain the purpose of the test to the patient and direct their attention to a non-accommodative distant target, e.g. a distant spot light or the green side of the duochrome.

• Insert appropriate lenses for your working distance and ensure that both eyes are fogged (to prevent accommodation).

• If your cover test revealed a tropia, occlude the eye you are not working on to ensure fixation.

• Be careful to perform retinoscopy on axis and remind your patient to keep looking at the target (this also helps them keep their eyes open - quite difficult if it’s the end of the day!).

• If you are uncertain on small negative cylinders, consider raising the collar on a streak retinoscope to reverse the movement (it is easier to see with movements than against).

The assessor will want to check your retinoscopy, so your retinoscopy should be accurate to within +/- 1.00 DS and +/- 1.00 DC with an axis orientation appropriate to the degree of astigmatism, i.e. lots of room for axis error on small cylinders.

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3.4 Subjective

You will have plenty of notes from university and videos online that you have referred to in the past.

Here are a few more top tips:

• Take acuities from your retinosopy results and perform a quick plus one blur test on each eye. From this you should have a good idea of the prescription and know if you just need to refine your results with cross cylinder, duochrome and further plus one tests, or if you are way off the mark and need a complete rethink.

• If the latter is the case, think logically.

• From the visions, was the patient myopic, hypermetropic or astigmatic?

• How does this fit in with your retinoscopy result?

• Can you salvage something from it, or should you just go for best sphere and block and fan?

• If poor acuity is only found in one eye, consider performing a pin hole test just to see what you are aiming at. Ask the patient if this eye has always been worse than the other eye - you may have missed a small tropia on cover test.

3.4.1 Fan and block

Fan and block is a underrated test for getting out of difficulties or for ruling out astigmatism where none was found on retinoscopy. The basics of the technique are:

1. Find the best sphere and estimate the cylindrical part of the prescription (use the rule that one line of the chart is equivalent to 0.50DC).

2. Fog the patient by +0.50DS plus half the estimated cylinder. Identify the darkest lines on the fan chart and equalise the limbs of the ‘V’ by rotation when pointing at the darkest lines.

3. Check that the block in line with the ‘V’ has the darkest lines. Double check the blur by adding more plus and checking that the clarity of the blocks doesn’t swap. If it does, your cylinder axis is 90° out!

4. Add negative cylinders at the indicated axis to equalise the clarity of the blocks. Check by adding slightly too much cylinder and getting the clarity of the blocks to switch.

5. Gradually remove the fogging sphere to give the best acuity.

NB Block and fan doesn’t work with positive cylinders, so please stick to negative cyls. It also makes fitting contact lenses easier too.

3.4.2 Cross cyl and duochrome

If you use cross cyl and duochrome to refine your retinoscopy results, remember that duochrome only works on about 70% of the population. It is less useful with high myopes and presbyopes, where the yellowing of the lens will tend to give a red bias, so always bear in mind your plus one results. If cross cyl seems to be going round in circles, use a +/- 0.50 cross cyl to accentuate the differences.

Having achieved maximum acuity for both eyes, record acuities, plus one and duochrome results for your final prescriptions, to support them. Then attempt to balance the eyes (assuming you haven’t done a binocular refraction and that the acuities are approximately equal). The most common technique used is a form of the Humphriss method. Then offer a binocular addition, remembering the aim of refraction is to give the most plus/least minus consistent with best acuity.

< Clinical refraction

3.5 Distance oculomotor balance

With your final distance prescription in place, consider which method of assessing muscle balance is appropriate. If your patient has no symptoms of muscle balance problems, do you need to do associated and partial dissociation tests or will just one test suffice? Do not attempt to measure associated muscle balance in patients who have a manifest strabismus (tropia). 3.6 Near vision assessment

Adjust the trial frame to the near centration distance.

• Measure amplitudes of accommodation monocularly and binocularly, using the RAF rule.

• Remember to use supplementary lenses for presbyopes to place the reading on the more accurate part of the scale.

• The amplitudes should be equal in both eyes; if not, consider your distance prescription and/or pathology.

• This is also a good time to measure the near point of convergence, noting each distance in cm for blur, break, recovery.

3.6.1 Presbyopes

Presbyopes may give a much higher than expected amplitude of accommodation, due to miotic pupils giving greater depth of focus. An approximate table of amplitudes and additions follows (table 1): note that the addition given will vary with the task required and the acuity of the patient, i.e. someone with VAs of 6/12 will require a higher add than someone with VAs of 6/5 to read N5, given that both patients are the same age. If the patient has low acuity, explain a little bit about the effects of illumination levels on acuities and consider a higher than usual add, bearing in mind the restrictions of a short working distance.

Age Expected amplitude (DS) Near addition (DS) 20 11 0

30 8 0

40 5.5 0 - 0.50

45 4.5 0 - 1.00

50 2 1.00 - 1.75

55 1 1.50 - 2.25

65 0 2.00 - 3.00 Table 1

• Measure the patient’s working distance and insert the appropriate reading addition (always remember to adjust the centration to near if using a trial frame).

• Check the range and the near VA and record.

• If time permits, you could consider a near duochrome test to reinforce your conclusions but remember presbyopes may have a red bias due to yellowing of the lens.

• Now assess the near oculomotor balance with the prescription in place; the same factors apply as to distance muscle balance. You can use cover test and speed of recovery but to demonstrate the range of your skills you should have available a near Mallett unit which can measure associated phoria and determine binocular stability. Other tools include Maddox wing and possibly a Friedmann triangle unit; use whichever you feel is required. © 2021 Specsavers Ltd 23 < Section A Professional assessment and record keeping

< Clinical refraction

3.6.2 VDU users If the patient is a VDU user, you should consider the need for an intermediate add and intermediate muscle balance test. 3.7 Slit lamp examination and ophthalmoscopy A full ophthalmoscopic examination must be carried out and full notes made. Remember to record your observations accurately. Anything not recorded may as well not have been done. 3.7.1 External eye and ocular adnexa Using the slit lamp you should assess the cornea, lids, lashes, palpebral and bulbar conjunctiva (everting the eyelids as required). Make notes, using grading scales that you are familiar with. 3.7.2 Media Examine the cornea, tear film, and anterior chamber and iris. • Grade the anterior chamber depth, e.g. by Van Herick • If using a direct ophthalmoscope, rack down through to the plus lens power to assess the clarity of the crystalline lens by observing via combination of direct and retro-illumination from the red fundal reflex; this enables you to home in on any areas of opacification. • If using a slit lamp use the slit beam to create a section through the lens. Using a small conical beam through the pupil and on-axis can allow you to inspect with retro-illumination too. • Locate and draw opacities noted. • If using a direct ophthalmoscope, begin from e,g, a plus 10 lens to rack through the lens powers to approach the patient’s refractive error which should allow you to view the vitreous and then the retina. • Using low to medium magnification on a slit lamp, focus through the vitreous, noting any floaters, their location and size as you ask the patient to move the eyes up and down, left and right to create movement of any floaters. 3.73 Fundus Regardless of whether you are using a direct or an indirect method, the steps are similar for a routine examination of the fundus. First ask the patient to fixate a suitable target that will prevent them from converging their eyes and then locate the disc. • Assess the disc colour, cupping, vessel displacement, clarity of margins, presence of pigmentation, noting presence of peri-papillary atrophy, splinter haemorrhage or myopic crescent. The high magnification as viewed with a direct ophthalmoscope is particularly helpful for looking for signs of spontaneous venous pulsation which is present in 80% of normal eyes and can be a reassuring sign to find when you are trying to rule out suspicion of papilloedema in a disc with blurred margins. • Trace the vessels out from the disc noting calibre, crossings and tortuosity. • Ask the patient to gently look in the eight cardinal gaze directions to observe the peripheral fundus, recording any features of note. • If using a direct ophthalmoscope, select the macular stop and yellow filter and ask the patient to look at your light so you can observe the macular area, noting quality of foveal reflex. • When using a slit lamp with Volk BIO start with 10x magnification and turn the rheostat down so that the illumination does not cause too many distracting reflections on the cornea. Since the field of view is greater than with a direct ophthalmoscope it is possible to scan larger areas and make comparisons of colour change. As a binocular technique it provides better depth perception and it is possible to see more detail by simply increasing the magnification setting on the observation column. Read more about slit lamp techniques on page 36

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3.8 Supplementary tests Consider recommending further tests on a vocational basis, e.g. stereoscopic tests for forklift truck drivers, or colour vision analysis for people working in textiles. Did your examination reveal anything else which would lead you to make a referral? Consult the latest guidelines from the College of Optometrists. You would be expected to: 1. Refer patients who need medical advice or specialist treatment. 2. Not refer patients who may have ‘departures from normality’, which do not need advice or treatment. 3. Formally notify GPs of signs and symptoms suggesting systemic conditions which they need to investigate 4. Inform the GP that you are managing a minor ocular condition that you have identified. 3.9 Final prescription and advice At the end of your routine eye examination you should: • Record your final prescription with back vertex distance where appropriate • Discuss your findings with the patient and advise them • when to wear the spectacles • any adaptation problems they may encounter • when to return for further examination • If the patient drives, tell them if the spectacles are required for driving • Record all advice given.

Assessment Tips

• Attend the assessment visit with a smart clinical appearance. • Have all your personal equipment ready in working condition, fitted with new batteries, etc. • Think logically. • Do not allow yourself to become flustered. • Remember that this is supposed to represent your normal clinical routine, so don’t try to impress by performing esoteric tests with which you are not comfortable. • Even though this is an artificial situation, try to communicate with the patient as you would in practice. Communication skills are assessed and an integral part of overall competency. For example, make sure anxiety doesn’t make you rush the patient. Give them time to answer your questions. • Try to establish a rapport with the patient; this demonstrates that you are in control of the situation and are capable of communicating with people on a one-to-one basis. • The most common reason for failure is not completing the examination on time. Practise beforehand with an exam routine sheet and time yourself. • Retinoscopy is another common cause of failure. Poor retinoscopy results are often due to being off-axis or the working distance not relating to the working lens used. Check working distance occasionally while performing retinoscopy. • Underline any significant points in the H&S and in the examination so you remember to address them in your final summary to the patient.

< Clinical refraction

Handy Hints

• Keep a tape measure in your consulting room to use for measuring intermediate additions • Use larger lens power bracket for people who are indecisive or have a reduced visual acuity. • Try a no pause policy. If a patient pauses or struggles to say which of two trial lenses is better, consider it a ‘the same’ response. • Ensure the patient does not squint (as in, screw up their eyelids) because this will give an unwanted pinhole effect. • Control accommodation throughout the refraction. If in doubt check with the +1.00-blur test • At the end of the refraction try and refine it using a real life target, while you are training. • If a patient is inconsistent or unreliable, don’t get frustrated; use larger steps or fall back onto your objective findings. • Remember to compensate distance Rx for projected chart in a 3 metre testing room or when using a space saver chart in a short form room. • Don’t tinker - commit to your new refraction with confidence. • Oblique axes are typically symmetrical, if they are not, double check your finding and the previous prescription. • Remember high myopes find the duochrome test more difficult, so it may not be reliable. • Double check any large changes in cyl or axis and discuss with your supervisor before prescribing • When refracting children, ensure your do not ‘over-minus’. To do this add +0.25DS to each eye and determine whether the child's ability to read the chart is the same. If it is unchanged, continue to remove minus binocularly until the visual acuity is affected. This will help reduce the likelihood that a child may be over-minused. • If a child is being inconsistent, try using a plano (+0.00) to see if it makes an improvement. This can also be used to demonstrate malingering to parents if necessary. • Handwriting. Keep it clear to avoid incorrect prescriptions being issued. • If you don’t already have a copy, the book Clinical Procedures in Primary Eye Care by David Elliott is both comprehensive and concise.

< Clinical refraction

Reflective Exercises

• Watch three different optometrists perform a subjective refraction. How does each practitioner vary their technique and why?

• Test yourself when performing retinoscopy; mark your provisional result against the auto-refractor findings.

• When performing a refraction on a high prescription, try using a Halberg clip. Is it helpful?

• How reliable is duochrome on high prescriptions? Make a note when people find it difficult; which alternative method did you use instead?

• Perform an audit of re-tests. How often did the prescription need to be modified? What were the common causes of error?

Reflective Exercises

One method you could use to practise your history and symptoms appraisal is to get together with other pre-reg trainees and play the old esoteric game of ‘guess the patient from the history and symptoms’. One person plays the patient and answers questions from the others; the ‘patient’ has to give ordered answers so at the end the questioners can make a reasoned guess at the patient’s refraction. For example, if the history is of someone in their early twenties who has no problems with their near vision, but who has found seeing overheads in lectures becoming gradually more difficult for the last six months, they are likely to be slightly myopic. Similarly, a 50-year-old who has no visual problems and can see clearly at distance and near, but has presented for routine examination, may be anisometropic - one eye being myopic and used for near vision, the other eye being emmotropic and used for distance vision. Alternatively, the patient may have miotic pupils giving increased depth of focus. Add variety to the game by bringing in pathology, such as the ocular effects of systemic medication. Think about presenting symptoms, e.g. try to define various headache types by their symptoms, such as differential diagnosis of frontal headaches; • if worse when reading it may be convergence insufficiency • if worse when bending the head forwards, it may be caused by sinus problems • if worse on waking might be tension headache which is a primary cause of headache • if associated with blurred/double vision or jaw claudication might be secondary due to temporal arteritis • if associated with nausea, vomiting and increased sensitivity to light or sound it might be migraine • if as above and preceded by a visual disturbance resembling flashing zig-zag pattern that grows over the course of 20 minutes it might be migraine with visual aura

< Ophthalmic investigative techniques

Ophthalmic investigative techniques

1. Core theoretical topics...... 30

2. Core practical topics...... 30

3. Key issues: tonometry...... 30 3.1 Indications for tonometry...... 30 3.2 Applanation tonometry...... 31 3.2.1 Imbert Fick law...... 31 3.2.2 Diameter/area applanated...... 31 3.2.3 Goldmann and Perkins tonometers...... 31 3.2.4 Non-contact tonometry (NCT)...... 32 3.2.5 Pulsair...... 32 3.2.6 OBF tonometry...... 32 3.2.7 iCare rebound tonometer...... 32 3.3 IOP: when to refer...... 33 3.4 Factors that affect the accuracy of IOP measurement...... 34

4. Key issues: slit lamp...... 34 4.1 Indications for slit lamp examination...... 34 4.2 Common filters...... 35 4.3 Supplementary techniques...... 35 4.3.1 Fundus viewing lenses...... 35 4.3.2 Pachymetry...... 36 4.3.3 Aesthesiometry...... 37 4.3.4 Gonioscopy...... 37 4.3.5 Photograpy and digital imaging systems...... 37 4.3.6 Tear assessment...... 37 4.4 Slit lamp routine...... 37 4.5 Methods of illumination...... 38 4.5.1 Diffuse illumination...... 38 4.5.2 Direct focal illumination...... 38 4.5.3 Indirect illumination...... 40

< Ophthalmic investigative techniques

4.5.4 Sclerotic scatter (split limbal)...... 41 4.5.5 Retro-illumination...... 41 4.5.6 Specular reflection...... 42 4.5.7 Tangential illumination...... 43

5. Key issues: visual fields...... 43 5.1 Indications for visual fields examination...... 43 5.2 Terminology...... 44 5.3 Advantages and disadvantages of kinetic and static techniques...... 45 5.4 Instruments and techniques commonly used...... 45 5.5 Characteristics of visual field loss that should be investigated...... 46 5.6 Information that should be recorded on a visual field chart...... 47 5.7 Relevant anatomy...... 47

6. Key issues: colour vision...... 49 6.1 When to examine colour vision...... 49 6.2 Congenital colour deficiency...... 49 6.3 Acquired colour deficiency...... 49 6.3.1 Characteristics of congenital and acquired colour deficiency...... 50 6.4 Common tests for colour vision defects...... 50 6.4.1 Pseudoisochromatic plates...... 50 6.4.2 Hue discrimination tests...... 50 6.4.3 Anomaloscopes...... 51 6.4.4 Lantern tests (Giles-Archer, Holmes-Wright, Edridge-Green)...... 51 6.5 Contrast sensitivity...... 51 6.5.1 Uses of contrast sensitivity measurements...... 51 6.5.2 Methods of measuring contrast sensitivity...... 52 6.6 Ultrasonography...... 52 6.7 Fluorescein angiography...... 53

7. Key issues: OCT...... 53

< Ophthalmic investigative techniques

1. Core theoretical topics

• Awareness of indications for tonometry, visual field and slit lamp examination.

• Familiarity with instruments currently available and examination techniques, their limitations and comparative performances, especially the instruments used regularly in practice.

• Knowledge of relevant anatomy and physiology, and their relation to observations.

• Demonstration of a logical response to results, taking into account the practitioner’s legal and professional responsibilities, with particular reference to referral for medical investigation.

2. Core practical topics

• Competence with the main techniques sufficient to produce valid results and understanding of the findings, which may include the interpretation of specimen visual field defects and other records of clinical investigations.

• Calibration and disinfection of tonometers, as appropriate, measurement of pressure, checking corneal integrity and interpretation of results.

• Demonstration of the methods of illumination on the slit lamp, and demonstration of the most appropriate methods to investigate anterior chamber anomalies.

• Control of the examination of the patient.

• Contact tonometry is assessed by direct observation in practice during Stage 1, visit 3. 3. Key issues: tonometry

3.1 Indications for tonometry

• You should use your professional judgment to determine if tonometry is clinically appropriate. Follow local protocols and include for all patients at risk of glaucoma.

• African/Caribbean ethnic group.

• Family history of glaucoma, particularly siblings.

• On ophthalmoscopy, cupping >0.5, or >0.2 difference between the eyes.

• Central retinal vein occlusion (=100-day glaucoma).

• Steroid use (high-dose and long-term, topically or systemically).

• Diabetes.

• Hypertension.

• Suspicious fields, particularly paracentral or arcuate scotomas.

• Before and after dilation, especially if the patient has narrow anterior chamber angles.

• To aid differential diagnosis of red eye.

• Haloes, especially coloured, around lights (indicates corneal oedema).

• IOP referral refinement scheme

< Ophthalmic investigative techniques

3.2 Applanation tonometry

3.2.1 Imbert Fick law

Applanation is the most widely used method of tonometry as it is generally more accurate, repeatable and less traumatic than indentation tonometry. The technique is based on the Imbert Fick law:

Intra-ocular pressure (IOP) = tonometer force (g)/applanated area (mm2)

This law states when a weight W(g) is applies to applanate an area, A (mm2), of a perfectly spherical container with an infinitely thin and elastic flexible membrane then the pressure inside the container P(mmHg) is equal to the W/A.

This relationship holds only for a spherical container with an infinitely thin membrane, which is flexible, elastic and dry, and when an increase in applanation does not increase IOP. The cornea is thick, wet and has some rigidity but, with careful design, the tonometer approximates the Imbert Fick law over the normal IOP range.

3.2.2 Diameter/area applanated

Goldmann found that an applanation diameter of 3.06mm was required to applanate an area of 7.354 mm2, which satisfied the criteria:

• Negligible fluid displaced (0.5μl), so drainage does not need to be considered. Therefore accurate repeatable measurements are achieved, and there is no ‘massaging effect’ (as is caused by the Schiotz).

• At 3-4mm diameter the surface tension is cancelled by corneal rigidity plus tear compression, therefore force = IOP

• If 3.06mm diameter is used: force (g) x 10 = pressure (mmHg).

• Using a split prism gave a more accurate Vernier-type measurement.

• If the astigmatism exceeds 3DC, the axis of the prism must be set at 43° to the flattest meridian to ensure an area of 7.354mm2 is applanated. This is achieved by aligning the minus cyl axis with the red mark on the cone holder.

The Perkins tonometer is based on the same principle, but is more portable, and can be used with the patient seated or lying down.

3.2.3 Goldmann and Perkins tonometers

The Goldmann/Perkins procedure is as follows:

• Inform the patient of the procedure.

• Examine corneal integrity by slit lamp.

• Wash hands and instil anaesthetic. Commonly used anaesthetic options include Minims oxybuprocaine hydrochloride 0.4%, Minims proxymetacaine hydrochloride 0.5%, Minims lidocaine hydrochloride 4% combined with fluorescein sodium 0.25%.

• Insert disposable probe without contaminating the tip and align the cone, making any adjustments for astigmatism.

• Check for anaesthesia with the wetted fluoret or tissue.

< Ophthalmic investigative techniques

• Instil the fluorescein if not already combined with the anaesthetic Minim. • Position the patient comfortably with the head supported; ensure they have a fixation point. • Record all readings, the instrument used and the time of day. • Check for abrasions by slit lamp. 3.2.4 Non-contact tonometry (NCT) There are now a variety of table-mounted NCTs, e.g. Topcon CT20, NIDEK NT-2000 and XPert Plus. Ensure you are familiar with the instrument you use in practice. 3.2.5 Pulsair Light passing through a target image is projected onto the patient’s cornea. The cornea reflects the image back through the optical system and is diverted by the beam splitter via a ‘contrast lens’ onto a set of three photodetectors. Part of the light also forms an image for operator alignment. Only when correctly aligned will more of the image fall onto the two outer diodes. The air pulse then applanates the cornea. The internal pressure transducer samples the pulse when the applanated cornea reflects more light onto the central diode (contrast reversal). The resultant pressure is displayed in mmHg. The Pulsair procedure is as follows: • Inform the patient about the procedure. • Check the 30+ and subflex are off. • Press ‘set/reset’. • Demonstrate the pulse of air to the patient. • Check calibration. • Press ‘set/reset’. • At 20mm, the patient can fix red light. • Take four readings R&L (need to reset after 30s). • The subflex may need to be turned on for irregular or scarred corneas, and for dry eyes. • Record all readings, instrument used and the time of day. 3.2.6 OBF tonometry The ocular blood flow tonometer can either be hand held or slit lamp mounted. The disposable probe is placed on an anaesthetised cornea. The instrument searches for satisfactory wave forms, and produces a pulsatile ocular blood flow reading (POBF), average IOP, pulse amplitude, pulse volume and pulse rate. POBF is a measure of choroidal circulation. 3.2.7 iCare rebound tonometer An iCare tonometer is a portable, handheld device used to measure IOP by assessing the deceleration and rebound time of a small, lightweight, disposable probe, which makes brief contact with the cornea. It can be used without local anaesthesia. The probes are disposable and must be changed for each patient, but can be used for both eyes assuming there is no eye infection. Each model has a built‑in adjustable forehead support and is supplied with single‑patient use probes, a spare probe base and a container for cleaning the probe base (recommended every 3–6 months).

< Ophthalmic investigative techniques

The iCare is used as follows: • Switch it on by pressing the 'measurement' or 'main' button. • Inset a new single‑patient use probe into the probe base and press the button to activate the probe. • Position the patient appropriately according to the tonometer in use: standing or sitting for all devices, or supine for iCare PRO only. • The patient needs to looks straight ahead and the tonometer should be brought close to the eye with the probe perpendicular to the centre of the cornea. • The forehead support should be positioned against the forehead. The distance between the tip of the probe and the cornea should be 3–8 mm depending a little on which model of I-care is being used. • The forehead support can be moved by turning the adjustment wheel to ensure the probe is correctly positioned. • The probe moves to the cornea and back during every measurement and a short beep sounds after each measurement has been taken. • The IOP reading is based on 6 individual readings (1 measurement sequence, which takes about 2 seconds). • Press the 'measurement' button to perform 1 individual IOP measurement. Each device calculates the final IOP measurement by discarding the highest and lowest readings and displaying the average of the remaining 4 readings. 3.3 IOP: when to refer This section is particularly important Criteria do vary slightly from one referral centre to another, but you need to think about your own referral criteria. • IOP should never be considered in isolation. To decide whether to refer, you must have plotted accurate fields and carried out disc assessment, and general eye examination. • Average IOP=15mmHg (standard deviation = 3mmHg), thus in 67% of the population IOP=12-18 mmHg and in 95% of the population IOP=9-21 mmHg. • Many people with ‘normal’ pressures have glaucoma. In such patients the optic discs change with time, and more accurately plotted fields help in diagnosis. In line with NICE guidelines, it is recommended that all patients with intraocular pressure of over 24mm Hg be referred to an ophthalmologist, • A pressure difference of 5mmHg or more is unlikely to be normal, unless it can be explained by a drainage operation, etc. The pressures should be re-checked with field, disc and general eye examination, and if the difference is consistently 5mmHg or more discuss with your supervisor and look closely at other related findings • IOP<5mmHg may indicate trauma or retinal detachment, especially if it is only low in one eye. NB The quoted measurements are based on average pressures taken with an applanation tonometer. A non-contact tonometer should be accurate as long as enough readings are taken with the patient in the correct posture and assuming the patient is relaxed.

< Ophthalmic investigative techniques

3.4 Factors that affect the accuracy of IOP measurement

• Arterial pulsation.

• Stress and apprehension can cause a large increase.

• Blinking can cause a large increase, due to the eye retracting and pressure from the lids.

• Exercise can increase IOP by up to 50%.

• Unstable tear film.

• There may be diurnal variation of up to 5mmHg. With open-angle glaucoma, this can be up to 13mmHg.

• Extra-ocular muscles under tension can cause up to 10mmHg increase, so ensure the patient is fixating in the primary position.

• Accommodation can decrease IOP by 2-3mmHg.

• Postural changes, e.g. inverted poses during yoga, can cause IOP to rise 4. Key issues: slit lamp

4.1 Indications for slit lamp examination

• New/all patients.

• Contact lens patients (preliminary investigation and all aftercare visits).

• Differential diagnosis of red eye.

• Foreign body detection and removal (know the techniques and procedure).

• Lacrimation (check lid position, puncta and tear film).

• Dry ‘gritty’ eyes (measure tear break-up time, volume and staining).

• Unexplained poor visual acuity (corneal dystrophies, degenerations or nuclear lens changes).

• To check the anterior chamber angle before dilating (Van Herick).

• Tonometry (before and after applanation tonometry to check corneal integrity).

• When supplementary lenses are required (e.g. Volk or gonioscopy lenses). 4.2 Common filters

Illumination filters • Normal (bright light). • Heat absorption (infra-red filter). • 50% neutral density filter. • Red-free (green). • Cobalt blue

< Ophthalmic investigative techniques

Viewing filters • Yellow (in front of the observation system to reduce the blue light), e.g. Wratten 12 for use when looking at fluorescein • Red (in front of the observation system), e.g. Wratten 24 to observe lissamine green staining more easily, as it will appear black against a red background.

Applications and benefits are shown in table 2. 4.3 Supplementary techniques

4.3.1 Fundus viewing lenses

The slit lamp can only focus as far as the anterior vitreous due to the refractive power of the cornea and lens, and also because the slit lamp is a microscopic system. To view the fundus, either neutralise corneal power or form an aerial image:

• Corneal power is neutralised by a high minus lens (Hruby, -55DS) or contact lens (e.g. Goldmann 4 mirror fundus viewing lens). The Hruby lens forms a narrow field, virtual erect image of the fundus. The image of the retina is near the corneal plane.

• A high plus lens (such as a Volk lens) forms an aerial image which can be focused by the microscope. Volk lenses, e.g. 60D, 78D, 90D and Superfield NC, form a real inverted aerial image between the lens and the slit lamp viewing system. This is similar to an indirect ophthalmoscope (hence the name biomicroscopic indirect ophthalmoscopy).

NB The main advantages of using these lenses to view the fundus are:

• Stereoscopic view facilitating the observation of detachment, disc cupping and raised lesions such as tumours.

• Better field of view when compared to approximately 8 degrees seen with the direct ophthalmoscope. Therefore less likely to miss an abnormality.

• Not dependent on refractive error therefore much better for high myopes.

• Much sharper view of the fundus in the presence of cataract and vitreous opacities.

See table 3.

< Ophthalmic investigative techniques

Filter Applications Benefits Normal Standard viewing Halogen light source has good colour rendering properties Heat-absorption To absorb infra-red Improves comfort 50% neutral density To reduce intensity of light - useful Does not affect colour rendering for photophobic patients Red-free With Volk lens examination to view haemorrhages and vessel integrity at the fundus For cornea to view new vessels Improves contrast Cobalt blue Examination of epithelium, TBUT and contact lens fit assessment Following fluorescein instillation Useful to see Fleischer's ring in Reduces veiling glare while keratoconus facilitating observation of fluorescence Yellow (adjacent to observer) With cobalt blue filter Improves contrast, by removing blue light reflected from the eye Diffuser (normally other side of Standard viewing for better colour Gives better colour rendering, mirror) or a tissue over mirror rendering without bleaching Useful enables measurement of true in red eye examination extent of red eye Table 2 Applications and benefits of slit lamp filters

Description Magnification Field of view (˚) Working distance Particular uses Static Dynamic from cornea (mm) 60D 31mm 1.15 68/81 13.0 Disc and Macula 78D 31mm 0.93 81/97 8.0 General Purpose 90D 21.5mm 0.76 74/89 7.0 Wide Field Super 66 stereo 1.0 80/88 11.0 Enhanced Stereo SuperPupil XL 0.45 103/124 4.0 Undilated Wide Field SuperField NC 0.76 95/116 7.0 Wider Field than 90D SuperZoom 78/90 0.96/0.78 82/101 7.0 Combination Zoom SuperVitreoFundus 0.57 103/124 4.0 Small Pupil Table 3 Fundus viewing lenses

4.3.2 Pachymetry

Pachymetry measures the thickness of the cornea. Central corneal thickness has been found to affect the measurement of intraocular pressure and thin corneas are linked with increased risk of developing glaucoma. Instrumentation options include hand held ultrasonic pachymeters, e.g. Pachmate but it can also be measured utilising an additional dedicated attachment to OCT. You should follow manufacturers' instructions according to the tool you have. Measurements are not clinically comparable between instruments so only make comparisons over time using the same instrument.

< Ophthalmic investigative techniques

4.3.3 Aesthesiometry

This measures corneal sensitivity (corneal touch threshold). Cochet-Bonnet apparatus is most widely used. The pressure on a nylon filament (0.12mm and 0.05mm diameter) is gradually increased until it bends, observed by slit lamp. Six to eight contacts are made, and if the patient feels less than half, the length of the filament is progressively reduced by 5mm until more than half are felt - this is the corneal touch threshold. The shorter the filament the greater is the pressure required to bend it.

Aesthesiometry is usually performed on the inferior cornea above the limbus. The humidity has to be controlled because it affects the filament. Corneal sensitivity increases during the day.

4.3.4 Gonioscopy

This is used to examine the iridic angle. A direct view of the iridic angle is not normally possible with the slit lamp because:

• The scleral shelf overhangs at the limbus.

• Light from the angle is reflected back into the eye (total internal reflection).

To get an accurate assessment of the angle, the cornea must be neutralised. NB The Van Herick technique only gives an estimate of the angle, as the trabecular meshwork cannot be seen.

The contact lens part of the gonio lens neutralises the corneal power and the mirrors reflect the illumination and observation systems into the angle.

4.3.5 Photography and digital imaging systems

Various photographic attachments can be added to help record eye conditions, from 35mm cameras, Polaroid cameras to video cameras that can be mounted and connected to a normal VCR or computer image grabber.

4.3.6 Tear assessment

The Tearscope Plus can be mounted on a slit lamp to allow non-invasive investigation of the tear film (pre-ocular and pre-lens). Keratoscope-type grid inserts can be used to check for corneal distortion. Observing the interference patterns of the tear fim using your specular reflection slit lamp technique and high magnification will also give valuable information about the tear quality. 4.4 Slit lamp routine

• Wash your hands.

• Ask the patient if they are comfortable.

• Adjust the interpupillary distance and eyepiece focus, using the focusing rod.

• Ensure the slit lamp is coupled.

• Explain to the patient simply what you are going to do.

• Adjust chair height if necessary.

• Adjust the chin rest - the outer canthus should be level with the eye guide marker.

• Give the patient something on which to fixate.

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4.5 Methods of illumination

4.5.1 Diffuse illumination

Figure 2

Use the widest beam of light and direct it obliquely at the anterior segment of the eye. Use low magnification initially. Ideally use the ground glass diffuser sometimes found on the other side of the reflecting mirror.

Uses

• Gives good overall view of the eye.

• Facilitates determination of the extent of a scar or vascularisation.

• Main technique for examination of the lids, lashes, caruncle and bulbar vessels.

4.5.2 Direct focal illumination

Figure 3

Here, the beam of light and the microscope are focused on the same area. There are three types:

A) Optic section

• Use low magnification at first to focus correctly then, with the narrowest beam (almost closed), increase the illumination and magnification, and view obliquely. The largest possible angle between the illumination and observation (up to 90°) gives the best results.

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Uses:

• To determine the depth of a foreign body or an abnormality in the cornea.

• To estimate the depth of the angle (Van Herick technique, see below).

• To identify distortions of the corneal contours.

• To examine the lens.

• To estimate the anterior chamber angle (Van Herick, Shaffer).

NB Using the Van Herick technique, the angle is estimated rather than measured. For a more accurate assessment of the angle itself, a gonioscope must be used.

For the Van Herick technique, set the illuminating beam to optic section and illuminate normal to the limbus. The angle between the microscope and the illuminating beam should be 60°. Move the slit beam from the sclera onto the cornea at the limbus until an optic section of the cornea is just visible. Stop and compare width of the aqueous interval with corneal thickness.

If the aqueous interval is narrower than a quarter of the corneal thickness in the nasal, temporal, inferior and superior angles (the slit beam should remain vertical to check the inferior and superior angles) then it is considered a narrow angle, capable of closure. The patient should be asked about the symptoms of closed-angle glaucoma. If they have had symptoms then they should be referred.

B) Parallelepiped

Figure 4

Use a moderately wide beam of light directed at the cornea; focus on the illuminated block of corneal tissue. The slit width should be approximately the same as the corneal thickness (0.5-1mm) if simultaneous viewing of the corneal surface and section is desired. Use 16-25x magnification for general viewing. Increase the illumination and magnification for greater detail.

Uses:

• Gives the ability to see surface irregularity and depth of a lesion.

• The best technique for corneal examination, nerves, striae folds, etc.

• To examine the endothelium.

NB viewing the endothelial cells via specular reflection is a monocular technique so don't expect a stereoscopic view (more on this later).

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C) Conical beam

Figure 5

This is used mainly to detect flares or cells in the anterior chamber. Direct the light, using a small circular aperture, through the pupil (do not illuminate any of the iris). All the room lights should be OFF. Focus the microscope on the aqueous, use high magnification and gently rock the illumination arm. The aqueous should be optically empty and contain no cells or protein to give rise to aqueous flare (Tyndall’s phenomenon). Flare indicates recent or active inflammation and needs to be referred urgently.

Uses:

• Detecting aqueous flare (protein, in inflammation).

• Detecting aqueous cells (red blood cells, white blood cells).

4.5.3 Indirect illumination

Figure 6

The microscope is focused sharply on an area immediately adjacent to the illuminated position. Focus on the interesting feature, uncouple, then move the beam slightly to one side. NB When the microscope is coupled, the illuminated area does not fill the whole field of view, therefore the structures adjacent to the illuminated patch are seen in indirect illumination (this is how it is normally done in practice).

Uses:

• Moving from direct to indirect aids detection of fine blood vessels, endothelial folds, etc.

• Good for studying the iris.

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4.5.4 Sclerotic scatter (split limbal)

Figure 7

This is a form of indirect illumination. A moderately broad beam of light is focused at the limbus; the cornea is viewed with or without the microscope. The room lights must be OFF. Using magnification requires you to focus on the cornea using direct illumination, then uncouple the beam and direct it so that it straddles the limbus. The light should be totally internally reflected by the cornea, but scattered by the sclera, resulting in a bright ring. Any corneal irregularities should show up as a brighter area.

Uses:

• To observe any disturbance of the normal corneal transparency, scars, etc.

• Check for corneal oedema (best without magnification, view from several angles).

4.5.5 Retro-illumination

Figure 8

This technique is used for studying anterior structures in reflected light from deeper structures, such as the iris, lens or retina. If the microscope can be focused independently then it can be focused on an area in front of the illumination. Otherwise the beam has to be uncoupled and offset to one side, to illuminate a posterior structure.

A) Direct retro-illumination

The object is viewed in the direct pathway of the reflected light (position 1 on figure 8).

B) Indirect retro-illumination

The retro-illuminated object is observed against a non-illuminated background (position 2 on figure 8).

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Uses:

• Excellent for studying corneal vessels, epithelial oedema, vacuoles, striae, etc.

NB Direct, indirect and retro-illumination are often all seen in the field of view when performing a normal slit lamp examination, and should not be thought of as separate special techniques that need to be set up independently.

4.5.6 Specular reflection

The beam and microscope are positioned so that the angle of incident light equals the angle of reflection, passing through one of the oculars. For example:

A) Specular reflection off the tear film

Adjust the angles between the beam and microscope until the dazzling pre-corneal fluid is seen. Used to check the tear film, epithelial elevations and depressions.

B) Specular reflection off the corneal endothelium

Figure 9

Using direct focal illumination (parallelepiped):

• Position the illumination system temporally.

• Look through the microscope and locate the bright reflection from the bulb.

• Move the beam until the bright reflection of the bulb is just adjacent (temporally) to the parallelepiped.

• Move the microscope until the endothelium is in focus (back of the parallelepiped).

• Adjust the angle slightly until the endothelial mosaic is seen in one of the oculars.

• At least 40x magnification is required (only a small portion of the bulb filament).

• Remember this is a monocular technique and you will only see the specular reflection in one eye piece.

Uses:

• To study endothelial dystrophy, endothelial cell loss, blebs, polymegathism, etc.

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4.5.7 Tangential illumination

Figure 10

This is a method of examining the cornea and iris, using very oblique illumination. With the patient looking straight ahead, set the illumination beam at approximately 90°, usually temporally.

Uses:

• Shows iris tumours, freckles, corneal nerves, Fleischer’s ring etc. 5. Key issues: visual fields

5.1 Indications for visual fields examination

You should use your professional judgment to determine whether a visual fields test is clinically indicated. Where available follow local protocol. Common indications include:

• New patients/all patients.

• Glaucoma patients and those with a family history of glaucoma.

• History of positive scotoma (patient reports some visual field loss).

• Recent onset headaches.

• To assess the activity and prognosis of disease.

• Localisation of the disease process.

• If the patient finds it difficult to locate steps, or misses part of the letter chart.

• Acquired colour vision changes (central fields - including Amsler).

• If the patient is taking certain medications, such as quinine.

• DVLA driving assessment.

The extent of the normal visual field is:

60° superior

60° nasal 100° temporal

75° inferior

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Sensitivity is not the same across the visual field. An isopter is a line joining points of equal sensitivity. These contour lines can be mapped to form an island of vision which moves up or down depending on the state of adaptation of the eye. The background intensity must therefore be kept under control to make the results 5.2 Terminology

A) Relative/absolute visual field

A relative visual field is the extent of the field with any facial obstructions in the way, e.g. prominent nose or brow. An absolute visual field is the total field with any obstructions removed by tilting or turning the head (keeping the same fixation point).

B) Relative/absolute scotoma

A relative scotoma is a reduction in sensitivity of that part of the retina, so that the stimulus can only be seen at a higher stimulus intensity than the surrounding retina. An absolute scotoma is an area of the retina that is unable to detect a stimulus of any intensity, e.g. blind spot.

C) Positive/negative scotoma

A scotoma is positive when the patient is aware of an area of blindness and negative when they are not.

D) Sensitivity/specificity

Sensitivity is the ability to detect abnormalities. Specificity is the ability to detect only abnormals.

To illustrate, an instrument can be 100% sensitive and ‘fails’ all the abnormals, but often it fails some normals as well. If an instrument is 100% specific then it only fails abnormals, but some abnormals may pass. Therefore an ideal instrument should be 100% specific and 100% sensitive.

E) Kinetic perimetry

A stimulus of a given size and intensity is moved across the visual field to establish its limits and those of any scotoma.

F) Static perimetry

A stationary test object of variable test value is used. There may be multiple or single stimuli.

G) Isopter

Contour line on a field plot representing equal retinal sensitivity to the target.

H) Threshold

The absolute threshold is the minimum luminance of a source at which the observer is aware of it.

The differential threshold is the minimum difference (in brightness, colour saturation or hue) between two stimuli that gives rise to a perceived difference.

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5.3 Advantages and disadvantages of kinetic and static techniques

Advantages of kinetic techniques Disadvantages of kinetic techniques More control over examination - can check any area, at Time consuming, poor for screening. any speed. Flexibility allows examiner to adjust exam to suit Flexibility makes it difficult to replicate results. Less patient. sensitive, relies on patient too much - inattention results in normal field. Requires thorough training. Advantages of static techniques Disadvantages of static techniques Less sensitive to operator variability. Field screening is Less flexible. rapid technique. Supra-threshold exam relies on a good threshold. Data can be used for numerical analysis. Full threshold techniques can be time-consuming and difficult for the patient. 5.4 Instruments and techniques commonly used

You need to know in detail about the ‘gold standard’ Humphrey, confrontation tests as well as the perimeter you use in practice.

A) Amsler charts or grids Flat book, central 10° from fixation, 30cm distance; most commonly used is the 1° squares. This is a good technique for assessing macular function. The patient is asked to report any areas missing (scotomas) or distorted (metamorphopsia). It is simple, quick and very sensitive. B) Gross perimetry This is often the only way to assess peripheral fields in a practice. It can be performed in three different ways: • True confrontation, where the examiner compares his visual field to the patient’s in a frontoparallel plane, equidistant from patient and examiner. • Facial outline or hand perimeter arc technique. This is the best gross field technique to ensure the full extent of the field is assessed. The target is brought from non-seeing to seeing in an arc about 33cm from the patient (closer in facial outline). • Supra-threshold comparison test. A supra-threshold white or coloured target is presented in the four quadrants and the patient is asked whether it appears brighter, dimmer or different in any position. This test can be more sensitive than other confrontation tests for chiasmal hemianopic defects. C) Bjerrum screen Flat, central 25° from fixation, 1m or 2m distance. Background illuminance = 75.3lux. Uses 1 to 10mm white or coloured targets against a black screen. D) Henson 3000, 3200 Flat, central 25° from fixation, 33cm distance. Background luminance = 0.25cd/m2. Number of stimuli = 26, 66 or 132 supra-threshold at 5,8,12dB above threshold. Full threshold uses 52 locations in a 6° matrix. (3200 able to add extra points and save to disc.) E) Henson Pro 3500, Pro 5000 Bowl, 72º from fixation, 25cm distance. Background luminance = 3.15cd/m2 (10 asb) Angular subtense 0.5º (equivalent to Goldmann III). Stimuli can be presented in a 3º matrix to 24º, then 6º matrix to 60º. Fixation monitor by Heijl - Krakau technique in full threshold programs (Pro 5000 also has a CCD camera to monitor fixation).

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F) Henson 7000 SAP white-on-white testing Single and multiple stimulus suprathreshold screening 26 and 68 point suprathreshold test patterns (extendable in-test) Customisable strategies – add and re-test locations in-test Solid state electronics for durability and portability 5kg G) Humphrey Field Analyser III Bowl, 90º from fixation, 30cm distance. Background luminance 31.5 asb. Various screening and threshold strategies available. SATPA compares results to age normal and glaucoma databases. SITA alters the program during the test depending on the result. H) Dicon TKS4000 Bowl, 50° from fixation, 33.3cm distance. Background luminance = 10cd/m2 (31.5asb). Fixation target can be moved to anywhere within the tested field. Number of stimuli = 40 or 76 within the central 30°, or 72 for full field. Can be used as multiple presentation supra-threshold, or single-stimulus full threshold. Contains a voice synthesiser and recognition system. I) Fincham Sutcliffe screener Flat, 25° from fixation, 1m distance. Background luminance not provided. Number of stimuli = 67, Stimulus size increases to the periphery. J) Goldmann bowl perimeter Bowl, 90° from fixation, 30cm distance. Background luminance = 10cd/m2. Six stimuli of different sizes (0,I,II,III,IV,V). Filters 4e - 1a are used to attenuate the 1000 asb brightest intensity. Recorded as, for example, ll- 3d. It is used as a manual perimeter with a stylus connected to a projector, and therefore is designed primarily as a kinetic perimeter, though it can be used in a pseudostatic mode. K) Dicon LD400 Flat screen, 30cm distance. Background luminance = 10.02cd/m2. Blind spot location is checked at intervals during the test procedure using a stimulus much higher than threshold (Heijl-Krakau method). Can be used with ‘field-view’ software, which enables data to be stored and compared with previous tests. Includes kinetic fixation and digital voice synthesis. Uses multiple-point or single-stimulus presentation. Number of stimuli = 40, or 80 for central 30° field, 48 for central 10° field, and 72 or 120 for full field (60°) L) Henson 9000 SAP white-on-white testing Customisable single and multiple stimulus suprathreshold screening tests 26, 68 and 136 point suprathreshold screening patterns (extendable in-test) 10-2, 24-2 and 30-2 threshold test patterns (extendable in-test) 60° (monocular) / 160° (binocular) testing range ZATA threshold test using prior patient data. 5.5 Characteristics of visual field loss that should be investigated • Position • Size • Shape • Intensity (depth) • Uniformity • Margins (steep/sloping) • Onset/course • Unilateral or bilateral 46 © 2021 Specsavers Ltd < Section A Professional assessment and record keeping

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5.6 Information that should be recorded on a visual field chart

• Which eye affected • Examiner (especially if kinetic) • Name • Date • Target/isopter/threshold • Prescription used • Visual acuities • Pupil size • Reliability indicator score 5.7 Relevant anatomy

Figure 11 Nerve fibre distribution on the retina

Figure 12 The visual pathway and associated lesions with field defects

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Figure 13 Anatomy of the optic nerve

Figure 14 Blood supply

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6. Key issues: colour vision

6.1 When to examine colour vision

• All new patients.

• Children at school entry age, for advice on colour recognition.

• Children at 11 - 14 years, for advice relevant to prospective careers.

• Any patient reporting changes to their colour vision, monocular or binocular.

• Patients taking drugs known to cause colour vision changes.

• As an aid to diagnosing or monitoring pathology. 6.2 Congenital colour deficiency

Congenital colour deficiency shows X-linked chromosomal inheritance. This gives rise to the distribution of red/green congenital colour deficiency.

Frequency Deficiency in men in women Protanopia (red blindness) 1% 0.01% Protanomalous trichromatism (red weakness) 1% 0.03% Deutranopia (green defect) 1% 0.03% Deutranomalous trichromatism (green weakness) 5% 0.35% Total 8% 0.4%

When a child is found to have congenitally defective colour vision, the child and parent should be advised and given some idea how common it is. This can also include advice on how it may affect the child at school and their choice of career if the child is old enough. Colour vision requirements and tests used for a number of occupations can be found in the Association of Optometrists website. 6.3 Acquired colour deficiency

Acquired defects in colour perception can occur during life as a result of ocular pathology, intracranial injury or drugs toxicity. If age-related blue defects are included, the incidence of acquired deficiency is probably higher than the incidence of congenital defects. Acquired colour deficiency can be monocular, therefore may need to test one eye at a time to identify.

6.3.1 Characteristics of congenital and acquired colour deficiency

Congenital Acquired Present at birth Onset after birth Easy to classify Difficult to classify Does not change over time Type and severity changes over time Affects both eyes equally Monocular differences in severity Visual acuity unaffected Acuity is often reduced Visual fields are normal Field defects frequently occur, colour defects may occur sectorally in the eye Higher incidence in males Equal incidence in males and females Mainly deuteranopia or protanopia Mainly tritanopia

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6.4 Common tests for colour vision defects

6.4.1 Pseudoisochromatic plates

A) Ishihara

Careful use of different coloured dots, which are along the confusion loci of the defective, results in transformation or disappearance of the number.

• Performed at 2/3m distance or arm’s length.

• The most efficient test for screening red-green colour deficiency.

• Does not detect tritan defects.

The full version contains 38 plates: Plate 1 Demonstration: seen by all observers, detects malingerers. Plates 2 - 9 Transformation designs: a different number is seen by people with colour deficiency Plates 10 - 17 Vanishing designs: the number cannot be seen by people with colour deficiency. Plates 18 - 21 Hidden digit designs: the number cannot be seen by normal trichromats, but can be seen by people with colour deficiency. Not as efficient as other plates. Plates 22 - 25 Classification plates: vanishing designs to distinguish protan and deutan defects (the number that is seen either less clearly or not at all indicates the deficiency). Plates 26 - 38 Used for non-verbal patients. Failing more than four plates indicates a colour vision deficiency but, when used to give advice on careers, the test must be carried out under the correct lighting conditions. If the result is borderline, the test must be repeated.

6.4.2 Hue discrimination tests A) Farnsworth dichotomous D15 test The standard D15 test divides people into two groups:

i) Colour normal and mild anomalous trichromacy

ii) Moderate and severe colour deficiency

About 5% of men fail the D15 test. A single error of two steps or more constitutes a failure. A circular diagram is used to record the results. Isochromatic errors give rise to lines crossing the circle and help distinguish the type of colour deficiency in congenital protan, deutan or tritan anomalies.

B) The City University test (TCU test)

Derived from the D15, the TCU comprises booklets containing ten plates with a central colour and four peripheral colours. The peripheral colour most similar to the central colour must be selected. The test detects a red-green colour deficiency in about 5% of men, but is poor at classifying the defect.

The City University Colour Vision Test (Third Edition) consists of two parts which may be used in sequence or separately. Part One (screening/selection) screens for either protan/deutan (PD) or tritan defects. Part Two (detection/section) consists of a selection of plates previously used in the Second Edition. As the screening plates in Part One have not been validated in a refereed journal, there is no measure of their sensitivity and specificity. Thus the test’s pass/fail criteria must be considered within this context.

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C) Farnsworth-Munsell 100 hue test

Consists of four sets of 21 Munsell colours (originally there were 100). Takes around 20 minutes to complete.

• Not a reliable screening test.

• The total error score gives an indication of hue discrimination.

• The type of defect is identified from graphical representation of the results.

• Good for monitoring acquired defects as it spans the whole colour circle.

6.4.3 Anomaloscopes

The Nagel anomaloscope is the instrument of choice. Monochromatic yellow on one half of the field is matched with various proportions of monochromatic red and green.

• The best method of classifying colour vision anomalies.

• The only test which distinguishes between anomalous trichromats and dichromats.

6.4.4 Lantern tests (Giles-Archer, Holmes-Wright, Edridge-Green, CAM)

The lantern tests are valuable indicators of vocational practical performance. They are often required by the armed forces, merchant navy and Civil Aviation Authority. The tests indicate recognition and colour naming using coloured signals of varying sizes. A single error results in failure.

Errors on the Giles-Archer lantern test are:

• Any misnaming of red

• Any misnaming of green

• Yellow called either red or green

• Inability to distinguish red at large aperture 6.5 Contrast sensitivity

Contrast sensitivity measurement tests ability to recognise targets at different contrast levels. This gives more information about the patient’s vision in daily life, not just at the 90%+ contrast found on most consulting room visual acuity charts.

6.5.1 Uses of contrast sensitivity measurements

• Additional information about patient’s visual function. For example, two patients with cataract may have the same high contrast visual acuity as each other, but one may have poor contrast sensitivity across the whole range of spatial frequencies, affecting their ability to work and therefore may need earlier referral for surgical treatment.

• Early indication of pathology, e.g. optic neuritis.

• Better than visual acuity as an indicator of glare disability, e.g. cataract, corneal oedema, old deposited contact lenses.

• As a guide to low vision aid success. Contrast threshold measurements on the Pelli-Robson give an indication of the possible success of low vision aids and indicate likely strategies for reading rehabilitation.

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6.5.2 Methods of measuring contrast sensitivity

A) Arden grating plates

This is performed at 50cm distance, and is a collection of seven fixed spatial frequency photographs of sine wave grating. The contrast varies up the plate (0.2 - 6.4 cycles/deg), and the patient reports when they can see the grating.

NB Since this is criterion dependent it is not reliable. It is not a forced-choice method.

B) Vistech charts

This is a large board containing five rows of nine circles, progressively reducing in contrast. It is performed at 3m distance. There is only one circle for each contrast level,

1.5 - 18 cycles/deg, at a certain spatial frequency. Stripes within the circles are orientated vertically, sloping left or sloping right. There is some criterion dependency, therefore it is not strictly a forced- choice method, i.e. the patient can say ‘left’, ‘right’, ‘vertical’ or ‘blank’.

C) Cambridge low contrast gratings

Two plates are shown at a distance of 6m. Pages are presented in pairs. The patient’s score is the lowest contrast grating correctly identified. Contrast levels vary by 4 cycles/deg. This is a forced- choice method - the pattern is on the top or bottom.

D) Low contrast letter charts

Regan low contrast acuity charts are used at 3m distance. There are three charts - representing 96%, 11%, and 4% contrast. It presents a familiar format to the patient, eight letters per line. They keep identifying letters until four or more are incorrect (forced choice).The result is calculated and recorded. This test gives three readings on the contrast sensitivity function curve (x axis).

The Pelli-Robson low contrast sensitivity letter chart is fairly familiar test format as the patient is required to read the letters they can see, and can be used at 1m or 3m distance. There are eight rows of letters, in two groups of three letters per line, each group decreasing in contrast. When two or three letters in a group are identified incorrectly, the contrast level corresponding to the previous group is recorded (at 1m, 1-5 cycles/deg, at 3m 3-5 cycles/deg). 6.6 Ultrasonography

A transducer emits high-frequency sound waves that detect the reflections from tissue interfaces. A scan ultrasonography is a one dimensional image that is used to obtain accurate measurements within the eye. Used in calculating the intraocular implant power.

B scan ultrasonography is built up from a series of A scans obtained dynamically, and provides an image of the intraocular contents, even if the media is opaque. Used to aid diagnosis of space- occupying lesions, vitreous opacities and retinal detachment.

See figure 15.

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Figure 15 Ultrasonography 6.7 Fluorescein angiography

In this procedure, 5ml of 10-20% fluorescein solution is injected into the antecubital vein in the arm. It is then carried in the blood in its free form and also bound to albumen. 15 to 20 seconds later it appears in the eye. Blue light (480nm) excites the fluorescein molecules to a higher energy level to emit light of a longer wavelength (530nm). Using the appropriate filters ensures a good view of the dye though the arterial then venous systems in the choroidal and retinal circulations. Serial photographs are taken for later study. Pathological changes within vessels are demonstrated by their effect on the vascular circulation and breakdown of the inner (retinal circulation) or outer (choroidal circulation) blood- retinal barriers. These changes are shown by delay or lack of filling of blood vessels and areas of hypo or hyperfluorescence. 7. Key issues: OCT

OCT is a medical imaging technique that is now comprehensively used by ophthalmologists and optometrists to acquire high resolution images of the anterior segment and retina. This section is an introduction only; there is a wider portfolio of learning that is available to optometrists through our learning management system, iLearn, which Specsavers employees can log in to via www.specsaverspeople.com.

Optical coherence tomography (OCT) is a non-invasive medical imaging technique that uses light to capture high resolution, three dimensional images from within the optical biological tissue. It enables sub-surface images of translucent or opaque materials to be obtained at a resolution equivalent to a low-power microscope. OCT is an echo technique, similar to ultrasound imaging, and can therefore also be thought of as an optical ultrasound, as the imaging reflections from within the tissue provide cross-sectional images.

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In an OCT image, the ten distinct retinal layers can be identified

1. Inner limiting membrane basement membrane elaborated by Müller cells 2. Retinal nerve fibre layer (RNFL) axons of the ganglion cell nuclei 3. Ganglion cell layer nuclei of ganglion cells, the axons of which become the optic nerve fibres for messages and some displaced amacrine cells 4. Inner plexiform layer the synapse between the bipolar cell axons and the dendrites of the ganglion and amacrine cells 5. Inner nuclear layer the nuclei and surrounding cell bodies of the amacrine cells, bipolar cells and horizontal cells 6. Outer plexiform layer projections of rods and cones ending in the rod spherule and cone pedicle, respectively 7. Outer nuclear layer cell bodies of rods and cones 8. External limiting membrane layer that separates the inner segment portions of the photoreceptors from their cell nucleus 9. Photoreceptor layer layer of rod cells and cone cells 10. Retinal pigment epithelium single layer of cuboidal cells

Image presentation

Figure 16 B scan section macular organisation

It is possible to view OCT images with different colour schemes.

For clinical use, black-on-white and white-on-black are most commonly used as this provides the most clinically effective contrast and clarity.

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Macula scan

Figure 17 Macula scan

Thickness map

Retinal thickness maps (Figure 18) can be generated to provide quantitative data around a specific area of interest. These are displayed as colour maps. The warmer colours are indicative of increased retinal thickness, while cooler colours represent thinner areas. A thickness map can be useful in identifying the degree of diffuse thickening of the retina. OCT imaging techniques can be used to generate thickness maps of a three-layer complex consisting of: • Nerve fibre layer • Ganglion cell layer • Inner plexiform layer This then allows the assessment of numerous non-glaucomatous optic neuropathies to be made.

Figure 18 Thickness map

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RNFL scan

The RNFL is the anatomical structure affected in glaucoma. It is a relatively highly scattering layer compared to the vitreous and the subjacent retinal structures. Due to the cylindrical nature of the nerve fibres, the strength of the backscattered signal from the RNFL is expected to be strongly dependent on the incident angle of the light. The RNFL scan is a circular scan centred on the optic nerve head. It allows the shape of the optic nerve head to be imaged and the RNFL thickness to be assessed. The scan first displays the RNFL thickness profile at the temporal region, then the superior region, then the nasal region, then the inferior region and finally back to the temporal region referred to by the abbreviation TSNIT.

Figure 19 Retinal nerve fibre layer scan and TSNIT map

OCT is a medical imaging technique that is now comprehensively used by ophthalmologists and optometrists to acquire high resolution images of the anterior segment and retina. Due to its cross- sectional capabilities, OCT can deliver a direct method of assessing axonal integrity in multiple sclerosis and glaucoma. OCT is also an appropriate method to assess macular degeneration and is considered to be the new standard for the assessment of diabetic macular oedema. Furthermore, recent advancements in OCT devices have been developed to also perform angiography; this has led to the use of OCTs to assess retinal microvasculature pathology in diseases such as glaucoma and diabetic retinopathy.

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Handy Hints

• Find the manuals and calibration log for each instrument you would use over the course of a sight test

• Check the illumination that you would use for performing colour vision assessments. Is it correct?

• Read online web learning material on slit lamp assessment

• Write out a draft slit lamp illumination and operational routine that you can follow in each contact lens assessment

• Watch videos for each slit lamp illumination online.

Such as https://www.youtube.com/watch?v=riUS0nMy7P8 from GCU or

https://www.jnjvisioncare.co.uk/slit-lamp-techniques/slit-lamp-overview which is another useful video guide from Johnson and johnson on slit-lamp techniques

• Practise Goldmann tonometry: perform it five times in a week and compare your results against the pre-test NCT

• Download the College of Optometrists' glaucoma NICE guideline member briefing

Reflective Exercises

• Complete an audit of your team’s visual fields quality and present the results at a team meeting. Teach a member of the team how to use the instrument

• Complete and keep notes on performing three different protocols on your visual fields instrument

• Calibrate a Goldmann tonometer and think about how smoothly and logically you would appear to be to an observer.

• Practise every slit lamp illumination method over the course of the day for five days and reflect on whether any of the techniques are becoming more effective for viewing things you previously could not see.

• Complete the online OCT training package on iLearn, and attempt the online assessment

• Compare two different powered indirect lenses (Volk lenses) during a dilated and undilated assessment. How did they compare?

• Ask each optometrist in your practice to share with you their opinion on what their favourite Volk indirect lenses are. In which situations would they use each one?

• Consider and list which techniques you would use to help with the diagnosis of a range of different anterior and posterior eye conditions. Try them out to see if you can make the examination process flow smoothly.

< Ophthalmic investigative techniques

Section B

Clinical case management of ocular conditions

> Binocular vision > Ocular disease and abnormality > Use of diagnostic and therapeutic drugs

< Binocular vision

Binocular vision

1. General information...... 61 1.1 Preparation...... 61

2. Core theoretical topics...... 61

3. Core practical topics...... 61

4. The theory...... 61 4.1. Normal binocular vision and relevant anatomy...... 61 4.2. Stereopsis...... 62 4.3. Development of binocular vision, visual activity and refractive error...... 62 4.4. Abnormalities of binocular vision and their causes...... 62 4.5. Differentiation between various types of heterophoria and heterotropia...... 63 4.6. Investigation of binocular vision anomalies...... 63 4.6.1. Cover test...... 65 4.6.2. Ocular motility test...... 67

5. Diagnosis of heterophoria...... 69

6. Heterophoria...... 71 6.1. Concomitant (comitant) deviations...... 71 6.2. Incomitant strabismus...... 72 6.2.1. Differential diagnosis between congenital and acquired palsy in adults...... 72 6.2.2. Congenital mechanical strabismus...... 72 6.2.3. Acquired strabismus...... 73 6.2.4. Neurogenic strabismus...... 73

7. Convergence insufficiency...... 75 7.1. Definition...... 75 7.2. Measurement...... 75 7.2.1. Measuring near point of convergence...... 75 7.2.2. Measuring jump convergence...... 75 7.3. Treatment...... 76

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1. General information

1.1. Preparation This module can only supplement and not replace vital practical experience, whether in practice, hospital or with a local orthoptist. Note for pre-registration optometrists: you must make time for discussion with your supervisor, ideally on a weekly basis. This need only be for half an hour per week to discuss the basics, such as prism prescribing, ‘what if‘ scenarios presented within clinical practice, using clinical tests, writing referral letters and anything else that comes to light. 2. Core theoretical topics

• Normal binocular vision and relevant anatomy • Stereopsis • Development of binocular vision, visual acuity and refractive error • Differentiation of various types of heterophoria and heterotropia • Investigation of anomalies of binocular vision • Abnormalities of binocular vision and their cause • Selection of suitable (and unsuitable) cases for treatment by refractive and orthoptic means • Identification of cases in which a medical or surgical opinion should be sought 3. Core practical topics

• History and symptoms • Cover test • Motility test • Heterophoria assessment • Heterotropia (squint) assessment • Conclusions and recommendations 4. The theory

Make sure you are able to explain and discuss the following: 4.1 Normal binocular vision and relevant anatomy Binocular vision is the ability of the two eyes to work together simultaneously such that each eye contributes to a single percept. The ultimate goal of this similar percept is stereopsis which is a hyperacuity dependent on the two ocular inputs at cortical level. For binocular vision to occur without any symptoms, a number of contributing factors take effect. Three are vital: 1) Anatomy of the eyes 2) Motor system that allows for eye movements 3) Sensory system by which the brain receives and combines the information of the two eyes into a single percept. It is important to have a basic knowledge of the anatomy of the eye, orbit and extra-ocular muscles, including knowledge of the innervation and blood supply. © 2021 Specsavers Ltd 61 < Section B Clinical case management of ocular conditions

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The information is beyond the scope of this document but a good reference for this is: Pickwell’s Binocular Vision Anomalies 4.2 Stereopsis Stereopsis, which in laymans terms is known as depth perception, is based on the horizontal retinal image disparity between the two eyes. Stereoacuity is a threshold measure of the acute nature of this depth perception, providing an indication of the highest level of sensory binocularity for the person. A low level of stereoacuity can be associated with vision disorders including strabismus, amblyopia and significant refractive error. The measurement of stereopsis is therefore used clinically to help detect vision anomalies and for monitoring sensory binocularity. Random-dot stereotests are more effective than contour or line stereotesting for detecting vision anomalies. 4.3 Development of binocular vision, visual acuity and refractive error You should know the developmental status of the binocular vision system at birth, six months, one and three years old. Consider the visual acuity along with the development of fusion, vergence and the fixation system. You need to know how visual acuity would normally develop from birth to age 8. You should be able to explain periods of visual plasticity, the amblyogenic effect from visual deprivation of pattern stimuli and the natural history of amblyopia if identified and treated. Visual acuity measured can vary depending on the type of test used, i.e. evidence exists of 6/6 at six months by visual evoked potential (VEP) but not until later by more conventional methods. We no longer believe that 6/6 is attained at five years of age! You should know the natural history of refractive error change with age and the typical refractive error at birth, one year and beyond, and hence the significance of abnormal refractive errors at each age. For example, a prescription of + 5.00DS R&L at the age of three years is clinically significant whereas + 2.00DS is not necessarily so. Anisometropia and astigmatism greater than 1D are also significant at this age. 4.4 Abnormalities of binocular vision and their causes

Tip for revision:

Why not research and create a table for each of the following: a) What age range does each of the following develop? Visual acuity, eye movements e.g. fix and follow, saccades, smooth pursuit movements, accommodation, convergence, binocular functions: bifoveal fixation, fusion and stereopsis and colour vision b) Factors that influence or place risk for normal visual development e.g. birth history c) Clinical tests suitable for measuring visual acuity for different age groups e.g. Cardiff acuity cards have a vanishing Figure 20 A typical distribution of distance optotype and are generally suitable for heterophoria. More individuals are not infants up to the age of 3. orthophoric than one would expect.

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Abnormalities of binocular vision can be categorised into: a) Heterophoria b) Heterotropia which can be congenital, acquired, neurogenic, mechanical, related to accommodation.

Tip for revision:

• There are many different types of heterotropia. Why not research each type and its cause?

• Also consider how you would differentiate between one form and another e.g. differential diagnosis between neurogenic and mechanical.

4.5 Differentiation between various types of heterophoria and heterotropia

A heterophoria is a dissociation of the eyes from their normal position controlled by various factors such as accommodation and fusional vergence whereas a heterotropia is a manifest deviation with a variety of causes.

For heterophoria always consider: a) Direction of movement - only detectable with a cover test. b) Size - small, medium, large (you may measure size with clinical techniques such as: prism cover test, Mallet unit, Maddox rod). Consider change in size according to the distance of fixation i.e. near, distance, VDU work. c) Speed of recovery - vitally important as it is a good indicator of the degree of compensation. A quick, smooth recovery on cover test means the phoria is well compensated.

For heterotropia consider: a) Direction of movement b) Incomitancy - i.e. does the size increase in a certain direction of gaze? c) Congenital or acquired d) Neurogenic or mechanical e) Relationship with accommodation, especially important in congenital deviations. f) Presenting symptoms with heterotropia 4.6 Investigation of binocular vision anomalies

History & symptoms is vital for any good clinical investigation and diagnosis.

History & symptoms in terms of binocular vision can be used to inform your examination, since you will not do all possible tests at your disposal. So, identify risk factors/ when it possibly started/ cause or nature of condition. Ask the patient if the doubling is horizontal or vertical (or both) and does it go away if one eye is closed/occluded. Let the patient guide your assessment.

Never assume the patient knows what normal vision is?/ what blur is? - perhaps diagrams or demonstrations of what these entities are may help e.g. a chart with levels of blur.

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For both adults and children start by asking:

Reason for visit - for children ask parents do they have any concerns or worries?

Need to know if possible:

Age of onset of presenting signs/ symptoms Who noticed them Frequency Time of occurrence Speed of onset Constancy or otherwise General health of patient when first noticed Previous ocular investigation and treatment. By whom? When? Compliance?

General health information: systemic conditions such as: diabetes, hypertension, cholesterol and any other conditions? Especially important for acquired conditions.

Family history: of strabismus/ amblyopia/ other problems/ high Rx.

Age of onset The earlier you intervene the better. If you determine the exact age of a BV problem - then you know how long binocular cortical stimulation has been present for - the longer the better, especially in terms of prognosis. (So the longer the management has been in effect the better for the patient)

Remember there are some obvious scenarios to look out for: 1. Esotropia/esophoria presents 2-5years, typically 3 years. 2. Exotropia/exophoria presents around 5-7 years.

Esotropes/phores tend to present first since: around 3-4months the accommodative system is used far more expertly and at the age of 3-4years noted when they are first reading books etc.

There are various other clinical binocular vision tests that can be performed.

OBJECTIVE binocular vision tests SUBJECTIVE binocular vision tests • Cover-uncover and cover test • Fixation disparity test • Ocular motility • Stereo tests: • Motility with cover test > Randot and Titmus fly • Pupil reflexes - Hirschberg and Krimsky test > TNO • 4 prism base out test > Lang • Dynamic retinoscopy > Frisby test • Prism cover test. • Maddox rod • Maddox wing • Fusional reserves • Near point of convergence • Amplitude of accommodation.

Table 4 Summary of some of the objective and subjective clinical tests used in clinical practice.

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Tip for revision:

For each objective and subjective test research - 1) How to perform the clinical test. Consider: a) Target required b) Working distance to perform test c) Do you require spectacle correction? d) Technique to perform e) Instructions to give the patient. 2) Consider how a particular technique will help with diagnosis Examples are 4.6.1 Cover test and 4.6.2 Ocular motility

4.6.1 Cover test

The rationale behind the cover test.

The eyes become dissociated when one eye is covered, while the other eye is fixating. Sensory fusion is prevented so that fusional reflex cannot stimulate fusional vergence.

The eye under the cover moves to its passive position.

Therefore, the presence of a latent deviation (phoria) can be detected. If the person usually wears glasses then these should be worn during the test.

There are two types of cover test:- a) Cover-uncover is a unilateral cover test b) Alternating cover test: this test prevents association of the eyes and may produce a larger looking deviation the longer it is done.

Note: The binocular vision system is thought of as being divergent from the resting position when viewing a distance object and convergent for near. This is why on average a normal heterophoria is a small degree of esophoria at distance and exophoria at near.

Targets: Patient fixates on a letter one line above the VA of the worst eye. Use a spotlight if VA worse than 6/18 in one eye.

Set-up and performing: Keep the explanations simple - ‘this test allows me to determine how well your eye muscles are working together’ …. ‘all I want you to do is look at this target - if it appears to move, please follow it with your eyes’. Usually px wears appropriate correction (unaided, habitual, optimal).

Cover/uncover test: Allows binocular fusion when eyes are uncovered. Can distinguish between tropias and phorias.

Alternating cover test: Prevents binocular fusion as eyes are only briefly uncovered. Cannot distinguish between a tropia and phoria. Reveals the total tropia and phoria - usually when the px is tired or stressed. Reveals intermittent tropias (phorias that break down into a tropia)

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Questions and answers: 1. What must you record when performing a cover test? • Whether Rx is worn or not. • Testing distance - 1m, 1/3m, 6m etc. • Whether there is a compensatory head posture • Whether the target was a light or accommodative target. • The deviation type: phoria/tropia (which eye) • Size: small, moderate, large • Recovery rate/grade. 2. Why is it important to use a light and an accommodative target for children? To determine whether there is an accommodative element to the deviation e.g. the deviation is larger for an accommodative target than light.

Figure 21 Cover test movement in right convergent squint (esotropia). Upper: Right convergent squint. Middle: Opaque occluder causes right eye to take up fixation. Both eyes move in the same direction. Lower: On removal of occluder, both eyes move to the left as the left eye takes up fixation. Rule of thumb for estimation of size of squint: Movement small, but seen on careful cover test = 5-10∆. Easy to see on cover test, but cosmetically acceptable = 10-20∆. Large movement on cover test, cosmetically obvious = 20-30∆.

< Binocular vision

Figure 22 Cover test movement in esophoria. Upper: No manifest deviation. Middle: Opaque occluder causes left eye to move inwards. Lower: On removal of occluder, left eye recovers to straight ahead position. Unlike the cover test in squint (Figure 21), the results are usually symmetrical on covering the other eye.

4.6.2 Ocular motility test

Assessment of the smooth pursuit system

Observe the movement of the eyes carefully and for assessment purposes be prepared to describe or record accurately what you have seen.

• You must know your muscle actions (Figure 23).

• You must give clear instructions; do not rely upon the patient seeing double.

• You should track out until the eyes stop moving. This occurs around 45° in all directions. You can go as far out to the perimetry as required!

• Monocular motility sometimes helps your assessment e.g. detection between acquired and neurogenic strabismus.

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Set-up and performing:

• Pen torch held at 50cm from the patient especially important in young patients to avoid inducing effect of accommodation • Head of patient must be kept stationary. • Instruct the patient to observe the pen torch and follow through as moved keeping head stationary. • Remove the patient's spectacles to avoid unnecessary reflections. • Remember: ask the patient to report pain/ discomfort/ diplopia.

Questions and answers:

1. How would you tell if there is a muscle weakness? If the deviation remains the same in all directions of gaze the deviation is said to be comitant i.e. nil muscle weakness. If the deviation changes in any position of gaze the deviation is said to be incomitant and there is likely to be an associated muscle problem.

2. How would you tell if there is a palsied muscle? If a muscle or group of muscles are palsied the affected eye ‘underacts’ in the relevant direction of gaze. Different methods that may be used to assess ocular motility abnormalities: > Subjective responses - widest seperation of images in a particular direction/or line of gaze of palsied muscle. > Underacting eye - furthest image seen - this disappears on cover. > Corneal reflexes - some asymmetry in a particular gaze direction - palsied muscle. > Alternating cover test - largest deviation in line of gaze of the palsied muscle.

3. By looking at the corneal reflexes how would you tell if there is an over-action or underaction of the muscle? Over-action - reflex in opposite direction to movement. Under-action - reflex in same direction as movement.

Figure 23 The muscles that have their maximum effect in the different directions of gaze.

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5. Diagnosis of heterophoria

Many optometric procedures include the careful taking of symptoms and have been proposed as useful methods of diagnosing whether a heterophoria is decompensated.

Symptoms Blurred vision Double vision Visual perception difficulty Distorted vision Difficulty with stereopsis Monocular comfort Binocular factors Difficulty changing focus Headaches Aching eyes Asthenopic factors Sore eyes General irritation Note: these symptoms can also be caused by other factors or conditions. Reference for above symptoms summary Pickwell's Binocular Vision Anomalies

An assessment of compensation of heterophoria requires several investigative tests: • cover test • fixation disparity tests • dissociated heterophoria tests (Maddox rod/wing) • stereotest • suppression tests • near point of convergence • (possibly) fusional reserves

Management of heterophoria: generally six lines of action are taken: 1. Removing the cause of decompensation. 2. Refractive management. 3. Giving eye exercises 4. Prescribing prism 5. Referral to another practitioner. 6. Monitoring if nothing to manage.

Note: the simple approach of management is to determine the cause of decompensation and eliminating or treating the cause e.g. illness.

Esophoria Exophoria Convergence excess Divergence excess Divergence weakness Convergence weakness Mixed Non-specific Other causes: Other causes: • Anatomical • Wide PDs • High Rx = hypermetropia • Refractive (presbyopia, myopia) • AC/A ratio = high • Weak convergent fusional reserves. • Weak divergent fusional reserves • Age. Table 5 Summary of causes of esophoria and exophoria

< Binocular vision

Refraction The relationship between a phoria and the spectacle prescription. With refractive correction we need to be particularly careful as blur can cause fusion to be more difficult. Sometimes correcting small amounts of refractive error can dramatically improve binocular functions. When it comes to anisometropia this may produce intraocular differences such as aniseikonia which means differences in accommodation (especially when under-corrected) and lead to blurring - which can drive decompensated phorias. We need a balance between the two eyes and a clear image in case of refractive management. The goal is to reduce modification over time, reviewing 3-4months.

Esophoria Exophoria Symptoms: a) Divergence weakness Less marked than esophoria • Distance difficulties • Frontal headaches after prolonged • Worse end of day use of eyes b) Convergence excess • Ocular fatigue • Frontal headaches • Sometimes intermittent diplopia • Ocular fatigue • Symptoms more related to near work • Distance focus reduced after prolonged near work. Refractive correction: Esophoria and hyperopia: Exophoria and myopia: Max plus ➞ relax accommodation, Min plus. So you want them a bit more therefore, compensates for esophoria minus so they can accommodate over due to convergence - accommodation that to correct exophoria. Esophoria @ near and hyperopia: Hyperopia + exophoria: Multifocals or bifocals - as extra plus Partial correction, since full correction will blur the distance = relax accommodation - making Esophoria and myopia: exophoria worse Less minus possible. Since too much or minus = drive of accommodation and • Full correction + prisims or exercises hence esophoria • Partial corrections + prisms or exercises • Full correction with negative add Eye exercises: Develop divergent reserves and/or Develop convergent fusional reserves. if Rx correct - review in 1 positive relative accommodation. Develop a correct appreciation of month. If symptoms still Positive relative accommodation - the physiological diplopia. present, consider orthoptic measure of the ability to stimulate Treat any suppression that has been exercises. accommodation - whilst maintaining demonstrated. Works best in younger clear, binocular single vision Negative relative accommodation. patients 12-35yrs when Establish distance correction: symptoms marked (due to • Ask patient to view small letters on a motivation). card @ 40cm from the eye. If exercises given review - • Add lenses -0.25DS increments (drives every 3-4 weeks. ---- accommodation) until blurry. • Patient is trying to accommodate over small steps to keep convergence set @ 40cm by diverging for every -0.25DS increment. • In essence train divergence system since they are accommodating without converging. Prism correction usually prescribed as a result of: • illness • lack of time Base OUT Base IN • age • type of heterophoria • e.g. hyper Referral to a more expert binocular vision practitioner

Table 6 Summary of management of esophoria and exoporia.

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6. Heterotropia

Heterotropia (tropia) is a manifest deviation. It can be concomitant or incomitant. 6.1 Concomitant (comitant) deviations:

Concomitant (comitant) deviations require management if:

• They are causing problems

• They are likely to deteriorate if left untreated

• Cosmetically apparent and causing psychological problems e.g. reduced self-esteem or self- confidence.

The investigation and management of comitant strabismus include sensory and motor factors.

Note: patients who have not achieved a form of sensory adaptation to their strabismus, generally because of age (i.e. too old) will have diplopia. The main adaptations that occur in the visual sensory mechanisms are: suppression, abnormal retinal correspondence (ARC), harmonious anomalous retinal correspondence (HARC), eccentric fixation and amblyopia.

Exercise: make your own notes on the following:

• Why do suppression, ARC and HARC occur?.

• Types of amblyopia.

If treatment is required for concomitant strabismus, then sensory factors i.e. suppression, HARC, amblyopia, eccentric fixation are generally treated first. In some cases treatment of the sensory factors will resolve the motor deviation. However, in other cases refractive correction or fusional reserve exercises may be required to treat the motor deviation. Remember: know your level of competency in practice and refer if required.

Investigation usually with:

History and symptoms OXO - Mallett unit Worth dots Monocular covering Cover test Motility Post-operative diplopia test - especially important for patients with diplopia or suppression Assessment of the risk of intractable diplopia.

Management notes:

If the practitoner finds prismatic or spherical correction overcomes diplopia - this should be prescribed. Large angle strabismus may require surgical intervention. Prior to surgical intervention a trial botulinum toxin injection can be performed.

Generally cases of concomitant strabismus do not have a pathological cause and are managed within practice.

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6.2 Incomitant strabismus

The angle of deviation changes according to the position of gaze and which eye is fixating. Generally, if the patient fixates with the affected eye the secondary deviation in the unaffected eye is larger than that of the affected eye. Incomitant deviations can be: congenital, acquired, mechanical or neurogenic. Investigation techniques used for diagnosis: Cover test Ocular motility test - check for change in the size of deviation with gaze. Visual acuity Compensatory head posture Stereopsis and suppression testing - TNO, Worth dots, OXO targets Fusional reserves

Muscle sequelae 1) Primary palsy i.e. underaction of the affected muscle 2) Secondary over-action i.e. over-action of the contralateral synergist (Herring’s Law) 3) Over-action of ipsilateral antagonist (Sherrington’s law) 4) Secondary inhibitional palsy of contralateral antagonist (Hering's law) 1) & 2) occur at the onset of a palsy 3) & 4) generally take time to develop

6.2.1 Differential diagnosis between congenital and acquired palsy in adults

Congenital Acquired • Generally no symptoms • Symptoms present e.g. diplopia, headaches, • Unaware of when deviation started clumsiness, asthenopia • Have a compensatory head position (CHP) • Patient or family aware of exact date of problem • Have full muscle sequelae • CHP may be present • Deviation increases without compensatory head • Normal fusional reserves posture • Ptosis - dependent on type of palsy • Photographic records show CHP • Associated with systemic problems e.g. diabetes, • Expanded vertical fusional reserves HBP, trauma, multiple sclerosis, tumour. • Suppression may be present

6.2.2 Congenital mechanical strabismus A type of strabismus caused by something within the orbit restricting eye movements rather than a lack of innervation to nerves. Therefore, something within the orbit interferes with contraction, relaxation or otherwise free movement of the eyes. Generally detected within the first few years of life. Duane’s syndrome Cause: abnormal branch of the 3rd nerve innervating the lateral rectus muscle as a result of hypoplasia or aplasia of the 6th nerve. People affected by Duane’s syndrome have a restricted ability to move the affected eye outward (abduction) and/or inward (adduction). There are three forms of Duane’s syndrome, designated types one, two, and three. The types vary in which eye movements are most severely restricted (inward,

< Binocular vision

outward, or both). Type one is characterised by very restricted abduction and normal to mildly restricted adduction. The palpebral fissure narrows and the eyeball retracts into the orbit with adduction. One or both eyes may be affected. Most cases are sporadic; about 10% are inherited. Treatment may include glasses or contact lenses for vision correction, eye patches, or surgery. A suggested revision exercise is to make a table of the difference between the three different types of Duane’s syndrome. Brown's classification of Duane's syndrome: 1) Type A: Limitation on abduction > adduction, globe retraction of adduction and widening of the palpebral aperture on abduction. Head turn to the affected side. 2) Type B: Limitation on abduction, no effects on adduction. Globe retraction on adduction and widening of the palpebral aperture on abduction. Head turn generally present to the affected side. 3) Type C: Limitation more marked on adduction than abduction, globe retraction on adduction, and rarely on abduction. Head turn generally present - away from the affected side. Type A and B - affected eye is esotropic. Type C - affected eye is exotropic. Management: Detected for the first time - refer (can be associated with coloboma, Klippel-Feil syndrome, Cleft’s etc.) If no problems present and patient/parents aware of diagnosis - monitor.

Brown’s syndrome. A common congenital mechanical strabismus. Cause: generally as a result of inflammation or trauma to the trochlear region. Characteristics: • Limitation of elevation on adduction but normal depression. • Generally unilateral • Head turn away from the affected side. • Chin elevation and tilt to affected side may be present. Management: Refer if suspected for the first time. At hospital they may: monitor, possible intra-sheath tenotomy, possible recession contralateral superior rectus. Exercise: Research other congenital mechanical strabismus.

6.2.3. Acquired strabismus

Exercise: Make your own notes on the cause, characteristics, management and differential diagnosis of:

• Blow-out fractures

• Thyroid eye disease

6.2.4. Neurogenic strabismus

A neurogenic strabismus is caused by a lack of innervation to the nerves supplying the extra-ocular muscles.

There are three main palsies to remember: 3rd (oculomotor) nerve, 4th (adducens) nerve and 6th (trochlear) nerve.

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Outlined below are possible causes for each nerve palsy

3rd nerve 4th nerve 6th nerve Aneurysm of the circle of Willis Diabetes Multiple sclerosis Craniopharyngiomas Raised intracranial pressure Trauma Pituitary tumour Trauma Hypertension Vascular accidents Whiplash Severe head injury Giant cell arteritis - generally causes isolated palsy Herpes zoster ophthalmicus Diabetes Meningitis and encephalitis

3rd cranial nerve palsy

Features: Exotropic, hypertropic and inturned with a dilated pupil. Ptosis may be present. The upper and lower divisions may be affected separately.

Upper: Superior rectus Levator palpebrae superioris

Lower: Medial rectus, inferior rectus and inferior oblique affected. Sphincter pupillae and ciliary muscle affected.

4th cranial nerve palsy

Innervates the superior oblique muscles Congenital or acquired form

Features: Consider what the superior oblique muscle does and its muscle sequelae.

6th cranial nerve palsy

Innervates the lateral rectus muscle Usually acquired

Features: Esotropia - greatest on distance fixation. Face turn to the affected side.

Muscle sequelae: • Over-action of the contralateral medial rectus. • Contracture of the ipsilateral medial rectus. • Secondary inhibitional palsy of the contralateral lateral rectus.

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Investigations for neurogenic palsies - at hospital eye service: The aim is to determine the cause of the neurogenic palsy, therefore link the findings from the history & symptoms with other systemic and binocular vision tests: • Blood pressure assessment • Blood clotting • Blood constituent assessment • Blood sugar level checks • CT scans • MRI scans • X-rays • Motility • Stereopsis • Visual acuity assessment - monocular and binocular.

Treatment: • Alleviating the symptoms and restoring binocular single vision can be achieved with: prisms, teaching CHP, occlusion therapy, surgery and many other techniques. • Surgery - generally performed once deviation has been stable for six months. • Aim of surgery is generally to weaken the overacting muscles. 7. Convergence insufficiency

7.1 Definition

Convergence insufficiency (CI) can be described as an inability to obtain or maintain sufficient convergence for comfortable binocular vision for near targets. Convergence of both eyes occurs when fixating on near objects and is particularly important at normal reading distances. The act of convergence describes the motor element performed by the extraocular muscles to bring the eyes' visual axes together when viewing close objects to maintain bifoveal fixation.

CI can be an isolated finding or can occur alongside convergence weakness (exophoria or exotropia) and other neurological or mechanical issues. It affects about 5% of children over 6 years old and up to 13% of over 60 year olds. 7.2 Measurement

The two main ways to measure convergence are a) the near point of convergence and b) jump convergence.

7.2.1 Measuring near point of convergence

Bring a target from 50cm or a point where there is no diplopia towards patient’s nose at a speed 1–2cm per second. Ask the patient to report blur point and diplopia, watching for any eye turn (break point) or both eyes turning out. Gradually recede the target until monocular vision is achieved again (recovery). Measure the blur, break, and recovery in centimetres.

7.2.2 Measuring jump convergence

Hold two objects, one at 15cm and one at 50cm. Watch for fixation alternating between the two targets. Repeat 3–4 times. Movements should be smooth. The nearer target can also be bought closer to the nose and the closest distance recorded.

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7.3 Treatment

Before commencing treatment, the condition should be fully explained to the patient (and parent where applicable). The course of treatment should be discussed and agreed to gain maximum engagement and potential success with awareness that it can recur.

The most common types of CI treatment are listed below:

1) Pencil push up exercises — ‘pen to nose’ treatment is a commonly prescribed treatment for CI. It is easy to understand and demonstrate with minimal equipment and cost. The use of an accommodative target is recommended to exert the best accommodative convergence. A pen torch can be uncomfortable at closer distances and difficult to maintain fusion. One programme would be to perform the exercise 5 minutes per day for 5 days a week, recommending a 5 minute break from any near task afterwards. The patient should be made aware that the eyes may feel more tired immediately after the exercise.

The main problem with the pen to nose push up exercise arises when the patient does not easily notice physiological diplopia once their convergence breaks. Advise patient to have two pens, one held stationary further from the pen being moved closer, this way, they can be trained to appreciate physiological diplopia of the more distant object as an anti-supression check.

2) Dot card — this is a card which consists of a line with dots drawn at regular intervals. The patient is instructed to place the card such that one end of the line is at the level of the nose and to fixate on the dot furthest away at the end of the card. The line will appear in physiological diplopia and appear to bisect the dot like a ‘V’ (unless there is suppression). They are then instructed to focus on the next dot on the line towards them again and should now see an ‘X’ going through the dot. This is continued until they can see the dot closest to them at 5cm. An example of a leaflet is available at:

http://www.swbh.nhs.uk/wp-content/uploads/2012/07/Dot-card-exercise-ML4720.pdf

3) Orthoptic exercises with stereograms e.g. 3 cats. These exercise relative positive fusional ranges and involve holding the stereogram at arm’s length and focusing on a pen in front of the card. The aim is to focus on the pen which is gradually brought towards the nose whilst viewing the cats in physiological diplopia. An example leaflet can be found at:

http://www.northdevonhealth.nhs.uk/wp-content/uploads/2009/10/stereograms_convergence_ exercise.pdf

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Handy Hints

• Cover test is always easier to perform with patient's existing glasses on than it is with a trial frame.

• Cover test not worth doing with a phoropter. Always perform cover test with relevant refraction in a trial frame or glasses.

• Always check stereopsis early on during a consultation in young children as it's a fun test for them.

• The presence of high levels of stereoacuity in a child can be really helpful information about the relative visual development of the two eyes.

• Convergence insufficiency can be managed by an optometrist and saves unnecessary referrals to secondary care.

Reflective Exercises

• What is the pre-school vision screening policy in your locality? Is it carried out by orthoptists? Is there also an enhanced service whereby community optometrists participate in cycloplegic refraction and fundus examinations of those who fail the screening?

• Children who are struggling at school might happen to also have uncorrected refractive or BV problems. Which clinical tests can you routinely include to make sure you investigate fully to offer the right advice and avoid vision getting in the way of their performance?

• Numerous research studies have shown that non-strabismic amblyopia in a person with uncorrected refraction often improves in the early days with glasses alone. Cycloplegic refraction is an important tool to ensure that accurate retinoscopy can be carried out in young children. If you carry out a cycloplegic refraction in a child under 7 suspected of amblyopia, but refer to an orthoptist without issuing glasses, what would the risks to the visual development be?

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Ocular disease and abnormality

1. Introduction...... 81 1.1. The nature of ocular pathology...... 81 1.2. Assessment...... 81

2. Core theoretical topics...... 81

3. Core practical topics...... 81

4. Eyelids and lashes...... 82 4.1. Trichiasis...... 82 4.2. Distichiasis...... 82 4.3. Entropion...... 83 4.4. Ectropion...... 83 4.5. Chalazion...... 84 4.6. Hordeolum...... 84 4.7. Blepharitis ...... 85

5. The lacrimal apparatus...... 86 5.1. Epiphora...... 86 5.2. Dry eye...... 86 5.3. Dacryocystitis ...... 86

6. The conjunctiva...... 87 6.1. Subconjunctival haemorrhage ...... 87 6.2. Pingueculae...... 88 6.3. Pterygium...... 88 6.4. Bacterial conjunctivitis ...... 89 6.5. Adenoviral conjunctivitis ...... 89 6.6. Herpes simplex primary blepharokeratoconjunctivitis ...... 89 6.7. Adult Inclusion conjunctivitis ...... 90 6.8. Allergic conjunctivitis ...... 90 6.9. Vernal keratoconjunctivitis ...... 92 6.10. Benign conjunctival naevus ...... 93

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6.11. Limbal dermoid cyst ...... 93 6.12. Pyogenic granuloma ...... 94 6.13. Squamous cell carcinoma...... 95

7. Sclera...... 95 7.1. Episcleritis...... 95 7.2. Scleritis...... 95

8. Cornea...... 96 8.1. Superficial punctate keratitis ...... 96 8.2. Bacterial keratitis ...... 96 8.3. Viral keratitis...... 96 8.4. Acanthamoebal keratitis ...... 96 8.5. Radiation keratitis ...... 97 8.6. Cogan microcystic dystrophy ...... 97 8.7. Lattice dystrophy ...... 97 8.8. Granular dystrophy ...... 97 8.9. Macular dystrophy ...... 98 8.10. Fuchs' endothelial dystrophy ...... 98 8.11. Keratoconus ...... 98

9. Uveal tract...... 99 9.1. Acute anterior uveitis ...... 99 9.2. Chronic anterior uveitis ...... 100 9.3. Posterior uveitis ...... 100

10. Key issues: cataracts...... 100 10.1. Anterior/posterior capsular cataracts ...... 100 10.2. Anterior/posterior sub-capsular cataracts ...... 101 10.3. Anterior/posterior cortical cataracts ...... 101 10.4. Nuclear cataracts ...... 101

11. Anterior eye questions...... 101

12. Vitreous...... 106 12.1. Posterior vitreous detachment ...... 106 12.2. Vitreous haemorrhage ...... 106 12.3. Asteroid hyalosis ...... 107

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13. Vascular retinopathies and the retina...... 107 13.1. Diabetic retinopathy ...... 107 13.2. Hypertensive retinopathy ...... 108 13.3. Branched retinal vein occlusion ...... 109 13.4. Central retinal vein occlusion ...... 110 13.5. Branched retinal artery occlusion ...... 110 13.6. Central retinal artery occlusion ...... 111 13.7. Age-related maculopathy ...... 111 13.8. Retinal detachment ...... 112 13.9. Retinoschisis...... 113

14. Glaucoma...... 114 14.1. Primary open-angle glaucoma (POAG)...... 114 14.2. Normal tension glaucoma (NTG)...... 115 14.3. Ocular hypertension...... 115 14.4. Primary angle closure glaucoma...... 116 14.5. Secondary glaucomas...... 116 14.5.1. Pigmentary glaucoma...... 116 14.5.2. Pseudoexfoliation glaucoma...... 117 14.5.3. Inflammatory uveitic glaucoma...... 117

15. Neuro-ophthalmology...... 118 15.1. Retrobulbar neuritis...... 118 15.2. Arteritic ischaemic optic neuropathy (AION)...... 119 15.3. Non-arteritic ischaemic optic neuropathy (NAION)...... 119 15.4. Papilloedema...... 120

16. Key issues: pupils...... 120 16.1. Marcus-Gunn pupil ...... 120 16.2. Holmes-Adie pupil ...... 121 16.3. Argyll-Robertson pupil ...... 121 16.4. Pupillodilator dysfunction (Horner’s syndrome) ...... 121

17. Posterior eye disease questions and answers...... 123

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1. Introduction

1.1.The nature of ocular pathology

The detection of disease and/or abnormality in the eye, ocular adnexa or any other part of the visual system is of crucial importance in the work of the practising optometrist.

Entering the optometric profession is like taking up residence in a new country. At first everything seems strange and new. There may be a new language to be learned, but with time and effort, fluency can be achieved. The resident then has to become familiar with the geography of the country as well as the indigenous customs. Initially, their knowledge will only encompass broad concepts but, with time, the fine detail is acquired.

So it is too with ocular pathology. It has a specific language to describe disease processes in parts of the visual system that may be unfamiliar. In order to make sense of this, you need a sound knowledge of the anatomy and physiology of the eye and visual system. 1.2.Assessment

Competency Group 6 Ocular Disease and the 19 statements that make up this group are assessed throughout the pre-reg period during assessor visits and during the final OSCE.

There are many ocular pathology textbooks available. You will need to refer to them alongside this guide. It is useful to have access to a couple of different ocular pathology text books to support your learning. Popular ocular pathology text books include:

Clinical Ophthalmology : A Systematic Approach Brad Bowling and Jack J. Kanski

Synopsis of Clinical Ophthalmology Jack J. Kanski and Brad Bowling

Oxford Handbook of Ophthalmology Alastair Denniston and Philip Murray

Wills eye manual Gerstenblith and Rabinowitz 2. Core theoretical topics

• Anatomy of the eye, orbit, ocular adnexa, and intra-cranial visual apparatus. • Physiology of the eye with emphasis on aqueous production, circulation and drainage. • Vascular supply to the eye and associated structures. • Neural supply to the eye and associated structures. 3. Core practical topics

• Direct and indirect ophthalmoscopy, including Volk lenses with the slit lamp. • Tonometry. • Visual fields. • Stains used to detect ocular abnormality. • Swinging flashlight test to detect afferent pupillary defects

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4. Eyelids and lashes

4.1 Trichiasis

Description: Inward misdirection of the eyelashes.

Causes: • Trauma. • Loss of eyelid elasticity • Epiblepharon

Differential diagnosis: Ectropion, entropion.

Management: • Ocular lubricants - dependent on symptoms. • Referral where vision is being affected, management may be: • Electrolysis • Cryosurgery

Prognosis: Good.

Signs Symptoms • The eyelashes point inwards towards the cornea • foreign body sensation. None in some cases. • Often accompanies chronic blepharoconjunctivitis, • Redness. Pannus, corneal involvement • Mild photophobia • Itchiness Note: Symptoms may vary from person to person.

4.2 Distichiasis

Description: New lashes grow in front of the orifices of the meibomian glands. May not cause any problems, but may give rise to trichiasis and corneal damage,

Causes: • Congenital. • Acquired: blepharitis, MGD, chemical injuries, Steven-Johnson syndrome.

Differential diagnosis: Ectropion, entropion.

Management: • Ocular lubricants - dependent on symptoms. • Referral where vision is being affected, hospital management may be: • Electrolysis • Cryosurgery

Prognosis: Good if prompt treatment initiated prior to corneal

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Signs Symptoms • Lash growth • Moderate foreign body sensation. • Blepharitis • Redness. • MGD • Mild photophobia • Itchiness • Irritation • Corneal scarring • Watering • Chemosis

4.3 Entropion

Description: The margin of the lower eyelid turns inwards producing a trichiasis

Causes: • Senile lid laxity changes • Scar tissue causing the eyelid to pull to the globe • Present at birth

Differential diagnosis: Ectropion, entropion, distichiasis.

Management: • Ocular lubricants - to help with symptoms of FBS and corneal desiccation. • Referral dependent on the extent of corneal involvement.

Prognosis: Good if prompt treatment Otherwise corneal ulceration. scarring and pannus formation.

Signs Symptoms • Eyelid that turns inwards • Foreign body sensation (irritation) • Irregular vertical FB tracts noted on the cornea. • Lid spasms • Excess lacrimation Entropion guideline 4.4 Ectropion

Description: The margin of the lower eyelid turns outwards.

Causes: • Rarely congenital • Usually acquired and age-related, e.g.: - Facial palsy - Stroke

Differential diagnosis: Ectropion, entropion, distichiasis.

Management: • Ocular lubricants - dependent on symptoms. • Eyelid hygiene • Referral dependent on corneal involvement.

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Prognosis: Can lead to corneal abrasions, ulcers and scarring

Signs Symptoms • Lower eyelid turns or sags outwards. • Epiphora - due to the malposition of the punctum. • Red eye • Irritation • Lower corneal desiccation (or SPEE) • Dryness • Burning sensation • Decreased vision Ectropion guideline 4.5 Chalazion

Description: Chronic granulomatous lesion that causes blockage of the accessory tear glands. - Internal - affecting the meibomian glands - External -affecting glands of Zeis.

Causes: • Rosacea • Acne • Poor hygiene • Blepharitis

Differential diagnosis: Hordeolum

Management: • Warm compresses • Eyelid hygiene • Referral: Surgery - excision of the nodule if large.

Prognosis: Good but recurrent

Signs Symptoms • Swelling of the eyelids • Painless • Hard, firm, round or elongated mass - usually • Mild irritation extends outwards toward the eyelid margin (external) • Watering - may be recurrent • Can remain within the tarsal plate (internal) Chalazion guideline 4.6 Hordeolum

Description: Acute staphylococcal infection of the meibomian gland (internal) or eyelash and corresponding glands of Zeis and Moll (external)

Causes: • Rosacea • Acne • Poor hygiene • Blepharitis

Differential diagnosis: Chalazion

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Management: • Warm compresses • Topical antibiotics • Referral if preseptal cellulitis is present. Oral antibiotics

Prognosis: May result in secondary preseptal cellulitis.

Signs Symptoms • Acute presentation • Pain • Localised inflammation and tenderness. • Epiphora • Oedema and erythema. • Burning. Hordeolum guideline 4.7 Blepharitis

Description: Bilateral and symmetrical condition.

Causes: • Staphylococcal bacteria - present within the natural flora of the eyelids. The staphylococcus bacteria produce toxins which can be irritant to the eyelids.

Types of blepharitis: 1. Anterior seborrhoeic - common in younger patients - as a result of excessive lipid production, therefore scales appear greasy and soft on the base of eyelashes. Patients with this type of blepharitis usually have other skin conditions. 2. Anterior staphylococcal anterior blepharitis - usually present with hard, brittle, yellow scales on the base of the eyelashes. 3. Posterior blepharitis - exhibits yellow plugs along the eyelid margins where the meibomian glands are situated. Carefully note any notches in the eye lid margin are commonly due to meibomium gland drop-out. Associated with oil or foam in tear film.

Common symptoms: Generally symptoms are worst in the mornings. Grittiness, itchy eyes, burning, redness of the eyelids (hyperaemia), occasionally sticky eyelids on waking. Patients may frequently complain of watery eyes, especially outside in windy weather. Commonly due to evaporative nature of inadequate lipid layer. Symptoms are of chronic nature — which is important to highlight to your patients.

Management: Patients must be made aware of the chronic nature of the condition - therefore, treatment is ongoing. It may take 4-6weeks for a significant improvement to be seen. Patients can be educated with College or AOP leaflets

Generally: a) Warm compresses using a flannel/ eye bag - studies show for 7-10mins per eye. b) Eyelid wipe to remove excess oils c) Ocular lubricants - to combat symptoms of dry eye.

Prognosis: May be associated with hordeola, chalazia, tear film instability, conjunctivitis, keratitis, marginal keratitis - if management not followed.

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5. The lacrimal apparatus

This consists of the lacrimal gland, the accessory lacrimal glands of Krause and Wolfring, the lacrimal puncta, the canaliculi, the lacrimal sac, and the nasolacrimal duct.

5.1 Epiphora

Definition, signs and symptoms: • Overflow of tears across the lower lid margin and down the face.

Aetiology: • Sometimes blockage of the lacrimal drainage pathway. • Sometimes malposition of the lower punctum due to ectropion. • Developmental: in the newborn, failure of the drainage pathway to canalise. The problem may resolve spontaneously after a few months.

Treatment: • For blockage: syringing of the lacrimal drainage pathway. • Surgical intervention if syringing is unsuccessful. • For malposition of punctum: surgery. • For the developmental condition, if canalisation does not occur spontaneously: surgery.

5.2 Dry eye

Definition, signs and symptoms: • Sometimes inadequate tear secretion (indicated by Schirmer’s test). • Frequently inadequate wetting of the cornea, due to a deficiency in the mucin layer of the precorneal tear film (indicated by the tear break-up time (TBUT) and Rose Bengal stain). • Patients complain of a foreign body sensation and dryness of the eyes.

Aetiology: • Particularly common in middle-aged women. • Has been associated with some of the collagen diseases.

Treatment: • Artificial tears. • Rarely punctal plugs. Dry eyes guideline

5.3 Dacryocystitis

Definition, signs and symptoms: • Inflammation of the lacrimal sac. • Patients present with pain, epiphora (see 5.1) and local inflammation.

Treatment: • Warm compresses. • Topical and sometimes systemic antibiotics

Acute dacryocystitis guideline

Chronic dacryocystitis guideline

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6. The conjunctiva

When examining the conjunctiva consider conjunctival changes in the following categories.

Hyperaemia/conjunctival haemorrhages can indicate a series of complications from non-serious (dry eyes) to sinister (infectious conjunctivitis). The landmark of uveitis is peri-limbal hyperaemia.

Inflammation • Oedema • Papillae - vascular structures usually present in the upper fornix. Less prominent than follicular response. • Membranes and pseudomembranes - form when fibrous or inflammatory exudates are secreted by micro-organisms permeate in the conjunctival epithelium. They are adherent to the underlying tissue - therefore, prone peeling and bleeding . Generally pseudomembranes appear in adenovirus, vernal and gonococci conjunctivitis - can be removed by peeling. • Follicles - minute lymph follicles with accessory vascularisation. More common in the inferior fornix. Common in: viral, chlamydial and toxic origin. • Pyogenic granuloma

Pigmentation e.g. ethnic melanoma

Degenerative e.g. pingueculae/pterygium

Lumps/bumps

6.1 Subconjunctival haemorrhage.

Description: localised haemorrhage of a blood vessel or a group of vessels as a result of various factors.

Cause: • Idiopathic • Trauma • Hypertension • Increased venous pressure (e.g. coughing, sneezing, or straining) • Blood disorders (rare) • HIV/AIDS

Differential diagnosis: Conjunctivitis, Kaposi’s sarcoma.

Management: Take an accurate history & symptoms Reassurance - self-resolving Cold compresses - usually 2-3x/day for 7-10mins Referral - if recurrent or other findings Monitor blood pressure - esp. if recurrent.

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Prognosis: Good

Signs Symptoms • Localised or diffuse hyperaemia (remember: to • No symptoms grade) • Watering • FBS - dependent on cause. • Other symptoms may vary dependent on cause. Subconjunctival haemorrhage guideline 6.2 Pingueculae

Description: a degenerative conjunctival lesion

Cause: • Longterm UV exposure • Welding • Chronic irritation as a result of wind or dust. • Contact lens wear

Differential diagnosis: • Pterygium • Dermoid cyst • Episcleritis • Conjunctivitis

Management: • Ocular lubricants • UV protection advice - e.g. brimmed hat, sunglasses • Cold compresses

Prognosis: Chronic condition.

Signs Symptoms • Small yellow lesion - more common nasally • Asymptotic • Bilateral • FBS • Photophobia and irritation - if inflamed (pingueculitis) Pingueculae guideline 6.3 Pterygium

Description: a degenerative fibrovascular growth - generally extending from the bulbar conjunctiva towards the cornea.

Cause: • Longterm UV exposure • Age • Climate - dryness

Differential diagnosis: Pingueculae Cornea pannus

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Management: • Monitor and give patient advice • Ocular lubricants - for relief of symptoms • Referral - if visual axis affected, VA drop or induced astigmatism or cosmetically unacceptable.

Prognosis: Chronic condition

Signs Symptoms • Bilateral • Asymptotic • Scarred and thickened bulbar conjunctiva • FBS • Later stages - corneal thinning and stromal lamellae. • Photophobia and irritation - if inflamed • Later stages if cornea affected - epithelial iron deposits. Pterygium guideline 6.4 Bacterial conjunctivitis

Description: Inflammation of the conjunctiva as a result of bacterial contamination. Common in childhood. Recurrent infections as a result of: poor hygiene or lacrimal sac abnormalities

Cause: • Gram positive or negative bacilli • Staphylococcus aureus - most common • Streptococcus • Staphylococcus epidermidis, Streptococcus pneumoniae or Haemophilus influenzae

Differential diagnosis: Viral conjunctivitis Chlamydial conjunctivitis

Management: • Antibiotic treatment e.g. chloramphenicol or folic acid drops/ointment. • Eyelid hygiene - daily 2x/day. • Patient advice: • Self-resolving in 1-2weeks • Avoid eye rubbing for cross-contamination • Usually starts in one eye - may spread to another. • If makeup used - stop and discard. • Referral if not resolved - swab test - i.e. for lab identification.

Prognosis: Good with prompt management

Signs Symptoms • Mild hyperaemia • Eyelids sticking together • Mucopurulent discharge - worse in the mornings. • Papillae - esp upper palpebral conjuntiva. • Grittiness. • Inflammation of conjunctiva • Burning. Bacterial conjunctivitis

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6.5 Adenoviral conjunctivitis

Description: Inflammation of the conjunctiva as a result of viral contamination. Transmitted by respiratory or ocular secretions.

Cause: Adenovirus

Differential diagnosis: Gonococcal conjunctivitis Herpes simplex conjunctivitis

Management: • Self-resolving • Patient advice: • Avoid cross contamination • Ensure separate towels, bedding etc - highly contagious • Avoid attending work - ask GP to write sick note • Referral urgent within 1 week: Topical steroids may be used if not self-resolved

Prognosis: Self-resolving in 2-3 weeks

Signs Symptoms • Mild hyperaemia • Watering • Watery discharge • Discomfort and photophobia. • Follicles - esp. on lower conjunctival fornix. • Punctate epitheliopathy • Stromal infiltrates may form if not resolved - affecting VA Adenoviral conjunctivitis guideline 6.6 Herpes simplex primary blepharokeratoconjunctivitis

Description: Generally present in children. Initial infection presents at the mucocutaneous junctions of the lips. Latency within the trigeminal nerve Acute or recurrent conjunctivitis.

Cause: • Herpes simplex virus • From mother to child • From sexual partner.

Differential diagnosis: Adenoviral conjunctivitis

Management: • Cold compresses • Oral antiviral therapy - referral to GP.

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Signs Symptoms • Mild hyperaemia • Watering • Watery discharge • Discomfort and photophobia • Follicles - esp. on lower conjunctival fornix • Low grade fever • Skin lesions • Generalised illness. • Pre-auricular lymphadenopathy • Corneal stain - dendritic ulcer

6.7 Adult inclusion conjunctivitis

Description: Conjunctival inflammation caused by Chlamydia trachomatis.

Cause: Sexually transmitted

Differential diagnosis: • Gonococcal conjunctivitis • Allergic conjunctivitis • Viral conjunctivitis • Bacterial conjunctivitis

Management: • Referral to ophthalmology • Referral to Gynaecology • Topic antibiotic - prophylactic • Referral to GP

Prognosis: Dependent on management.

Signs Symptoms • Mild hyperaemia • Watering • Swollen eyelids • Discomfort and photophobia. • Chemosis - conjunctival • FBS • Follicles - inferior fornix. • Mucoid discharge • Enlarged lymph nodes • Uniocular or binocular presentation

Adult inclusion conjunctivitis 6.8 Allergic conjunctivitis

Description: 1) Seasonal allergic conjunctivitis (SAC) 2) Perennial allergic conjunctivitis (PAC)

Cause: • Pollen • Creams • Eye makeup/ eye products • Idiopathic

Differential diagnosis: GPC

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Management: • Non-pharmaceutical: cold compresses, artificial tears • Pharmaceutical treatment (referral to SP or IP optom) • Mast cell stabilisers • Anti-histamines • Dual action medications • Vasoconstrictors.

Prognosis: Good for SAC

Signs Symptoms • Mild hyperaemia • Itching • Eyelid swelling and chemosis • Burning • Stringy mucus discharge - esp. perennial • Watery eyes conjunctivitis • FBS • Photophobia.

Allergic conjunctivitis guideline 6.9 Vernal keratoconjunctivitis

Description: Chronic condition - as a result of some form of atopy e.g. acne, rosacea, eczema Usually first presentation in childhood. Peak at puberty. More common in male > female

Cause: • Atopy e.g. acne, rosacea, eczema • Positive family history.

Differential diagnosis: SAC PAC

Management: Referral to ophthalmology - urgent within 1 week Mast cell stabilisers (prophylactic) Anti-histamines Referral to SP or IP optometrist or hospital eye services: patient may be prescribed steroids Prognosis: Recurrent.

Signs Symptoms • Large papillae located around limbus and palpebral • Intense itching conjunctiva • Burning • Ropy mucus discharge • Watery eyes • Potential corneal involvement • FBS • Photophobia. • Possible pain.

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6.10 Benign conjunctival naevus

Description: Present at birth Sharply demarcated pigmented lesion - brown in colour

Cause: Congenital

Differential diagnosis: Malignant melanoma.

Management: • Monitor • Patient awareness • UV exposure protection

Prognosis: None. May develop malignancy

Signs Symptoms • Juxta-limbus - sharply demarcated pigmented lesion • None • Flat or slightly raised Benign conjunctival naevus 6.11 Limbal dermoid cyst

Description: Fleshy, defined cyst

Cause: Congenital benign tumour

Differential diagnosis: Pingueculae Conjunctival papilloma

Management: Monitor Ocular lubricants - dry eye/irritation

Prognosis: None

Signs Symptoms • Inferior temporal location - generally. • Dry eyes • Colour - yellow/grey/pink/brown • Cosmetic problems • Irritation

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6.12 Pyogenic granuloma

Description: Fibrovascular tissue growth as a result of a wound healing process.

Cause: Present generally after: strabismus surgery or pterygium surgery.

Differential diagnosis: Tumours Dermoid cyst

Management: Ocular lubricants Monitoring

Prognosis: Good

Signs Symptoms • Oval shaped mass - adherent to underlying sclera. • Dry eyes • More common in lower conjunctival fornix. • Irritation • Corneal dellen • Irregular astigmatism

6.13 Squamous cell carcinoma

Description: Elevated pink, fleshy mass Variants - nodular and diffuse.

Cause: • UV exposure • Age • Associated with leukoplakia (irritation of tongue and mouth)

Differential diagnosis: Pingueculae Pterygium

Management: • Refer to eye department - routine. • For diagnosis - use a cotton bud to move conjunctiva - if no movement of lesion then sign of malignancy.

Prognosis: Good if early detection and intervention. If intraocular penetration it may lead to iris involvement and potential glaucoma. Signs Symptoms • Pink and fleshy mass - from limbus to cornea. • Dry eyes • Hyperaemia • Irritation • Chemosis • Photophobia • Irregular astigmatism

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7. Sclera

7.1 Episcleritis

Description: inflammation of the episclera (loose connective tissue) located between the conjunctiva and sclera.

Cause: • Systemic inflammatory disease - arthritis • Gout • Collagen vascular disease

Differential diagnosis: Scleritis

Management: • Topical lubricants • Cold compresses • If recurrent and persistent - referral to GP for systemic check

Signs Symptoms • Hyperaemia • Dry eyes • Unilateral presentaton • Irritation • Nodular or diffuse. • 2.5% Phenylephrine blanches the redness.

Episcleritis guideline 7.2 Scleritis

Description: Bilateral inflammation of the sclera

Cause: • Rheumatoid arthritis • Sarcoidosis • Syphilis • Systemic erythematosus lupus

Differential diagnosis: Scleritis

Management: • Referral to eye department - EMERGENCY

Prognosis: Dependent on cause

Signs Symptoms • Hyperaemia • Pain - moderate to severe • Ora serrata involvement - if posterior scleritis • Deep ache • Watering • Gradual onset • Recurrent episodes Scleritis guideline

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8. Cornea

The cornea consists of five layers and, due to its exposed location, is a common site for trauma and infection. 8.1 Superficial punctate keratitis • Areas of fine punctate lesions on the epithelium, which stain with fluorescein. • Presenting symptoms vary: usually pain or foreign body sensation, lacrimation, hyperaemia. • Can be associated with infection, a toxic or immunological response or mechanical (contact lens) trauma. 8.2 Bacterial keratitis Signs and symptoms, epidemiology • Presenting symptoms usually are pain, lacrimation and hyperaemia. • The infected area of the cornea usually stains well with fluorescein. • Optical section with the slit lamp usually indicates epithelial involvement, though an infection can penetrate deeper into the stroma. • Prevalence may be on the increase due to the increase in contact lens wear in the population, particularly soft contact lenses. 8.3 Viral keratitis Aetiology, signs and symptoms • Two principal viral agents: herpes simplex and herpes zoster.

Herpes simplex infection • This causes classic dendritic ulcer, staining well with fluorescein. • Presenting symptoms are pain, hyperaemia and lacrimation. Herpes simplex keratitis guideline

Herpes zoster infection This causes: • Superficial punctate keratitis which can persist for months. • Sometimes dendritic-like ulcer, which can be distinguished from the classic form by the shape of the dendrite, which has tapered ends rather than the classic ‘end-bulb’. • Greater pain than herpes simplex ocular infection. • Systemic infection causes shingles, and the likelihood of ocular involvment is higher if Hutchinson’s sign (involvement of the nasal tip) is present. Herpes zoster ophthalmicus guideline 8.4 Acanthamoebal keratitis Symptoms and epidemiology • Presenting symptoms are extreme pain and the production of a deep ulcer. • The infective organism is found in water, so soft contact lens wearers who go against advice to make up their own saline using tap water are prone to the condition (this is now rare - see contact lenses module for further information). • Acanthamoeba can persist in the stroma, in trophozoite and encysted states, making therapy protracted and difficult.

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8.5 Radiation keratitis

Symptoms, aetiology and epidemiology • Commonly the result of UV radiation. • Presenting symptoms are the sensation of ‘grittiness’ in the eye, lacrimation, discomfort, and a punctate keratitis. • Those at risk include welders and winter sports enthusiasts who use inadequate eye protection. 8.6 Cogan microcystic dystrophy

Description: Map-dot dystrophy

Presentation: usually noted in the second decade of life. 10% develop recurrent corneal erosions

Cause: Thickening of the epithelial basement membrane and fibrous protein deposition between the Bowman’s layer and epithelium. Recurrent corneal epithelial erosion guideline 8.7 Lattice dystrophy

Description: bilateral affecting the stromal layer of the cornea.

Presentation: typically linear deposits (amyloid deposits) Type I - onset in the first decade of life Type II - onset in middle age. Type III - onset is usually in the fourth decade. Usually require keratoplasty - due to progression. 8.8 Granular dystrophy

Description: Bilateral stromal dystrophy

Presentation: appear as ‘crumb like’ white confluent lesions. Type I - early onset typically in the 1st decade of life. Type II - onset within the fourth or fifth decade of life. Type III - late onset - seen typically with lattice lines too. Associated with recurrent corneal erosions. Inheritance pattern - autosomal dominant - therefore important to advise patients.

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8.9 Macular dystrophy

Description: Stromal dystrophy - autosomal recessive inheritance.

Presentation: usually in the 1st or 2nd decade of life. Grey or white decal and dense opacities Corneal keratoplasty is generally required. 8.10 Fuchs' endothelial dystrophy

Description: Bilateral endothelial dystrophy hereditary autosomal dominant.

Presentation: generally 6th or 7th decade of life. Signs of corneal oedema - typically central guttae.

Look out for: dry eye symptoms, vision fluctuations - worse in the morning.

Fuchs endothelial corneal dystrophy guideline 8.11 Keratoconus

Definition: A progressive corneal condition that results in a change of corneal curvature leading to irregular astigmatism and progressive vision reduction

Cause: • Hereditary • Atopy • Excessive eye rubbing

Signs: • Cone shaped topography of the cornea • Early sign is a distorted scissors-type reflex - seen with both retinoscopy and ophthalmoscopy. • Vogt’s lines on the cornea • Munson’s sign - on downwards gaze • Iron deposits - Fleischer’s ring may appear on the base of the cone.

Symptoms: Progressive blurring Dry eye symptoms e.g. burning, itching, FBS.

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Differential diagnosis: • Pellucid marginal degeneration Tip: • Keratoglobus Ensure on each recall • Terrien’s marginal degeneration fluorescein examination Management: with slit-lamp • Initial correction with spectacles biomicroscopy is • Referral routinely for diagnosis via a corneal specialist recorded for the patient. • Ensure a 6-month review for eyes - if spectacle Rx stable and Regular keratometry or patient has no symptoms can put on 12/12 recall ensuring you topography should be advise patient to report sooner if any problems. performed • Contact lenses: soft, RGP, piggy back lenses - for later stages. • Eventually corneal transplant referral dependent on corneal involvement • Ocular lubricants preservative free for dry eye like symptoms 9. Uveal tract

The uvea comprises the iris, ciliary body and pars plana and the posterior region of the choroid. 9.1 Acute anterior uveitis

Description: Inflammation of the iris (iritis) and ciliary body (iridocyclitis)

Cause: Trauma Arthritis Sarcoidosis Spondylitis

Differential diagnosis: Acute onset angle closure Fuchs'

Management: Emergency referral to eye casualty

Prognosis: Dependent on cause.

Signs Symptoms • Hyperaemia - most severe in circum-limbal region. • Pain - severe or can be described as a deep ache • Lacrimation • Watering • Slit-lamp examination = cells and flare. • Acute onset • Keratic precipitates. • Adhesion of the iris to the anterior surface of the lens may occur (posterior synechiae) Acute anterior uveitis guideline

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9.2 Chronic uveitis

Definition: Chronic inflammation of the iris and/ or ciliary body. • Insidious acute attacks which may last 3-4months. • Minimal pain • Less hyperaemia • Sometimes vision may be affected. • Slit-lamp shows - cells and flare. • Pupil may be regular or irregular in appearance. - sluggish light reflexes 9.3 Posterior uveitis

Generally when no obvious retinal inflammation is noted. Sometimes cells and debris observed in the vitreous cavity.

Can be caused by: Harada’s disease, lymphoma, ocular histoplasmosis, sympathetic ophthalmia, retinal vasculitis.

10. Key issues: Cataracts

The term cataracts covers any opacity of the lens. Different types are classified by their location in the lens or cause.

Common symptoms: • Blurred vision • Glare esp. with night driving. • Myopic shift in Rx • Some alteration in blue colour perception due to a yellowing of the lens. Christmas tree cataract • Occasional monocular diplopia, due to beam. • Can also cause distortion of the optical image. 10.1 Anterior/posterior capsular cataracts

Located in the anterior/ posterior capsule of the lens. Appearance by slit lamp suggests a thin layer of frost on a window.

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10.2 Anterior/ posterior sub-capsular cataracts

Located in the lens substance immediately adjacent to the anterior/posterior lens capsule. Posterior sub-capsular cataracts are particularly serious because of their proximity to the posterior nodal point of the eye. 10.3 Anterior/posterior cortical cataracts

Located between the sub-capsular region and the lens nucleus. Senile cataracts tend to be of this type, often forming initially in the lower nasal quadrant of the lens. 10.4 Nuclear cataracts

Located in the lens nucleus. Can make the eye substantially more myopic, even before the nucleus opacifies. In sclerosis of the Tip: nucleus, slit-lamp examination shows quite a dense nucleus which Ensure you grade the is becoming yellowish brown. This discolouration alters colour level of cataracts on perception by absorbing blue light. examination. Treatment: There are several Surgical removal and implantation of an intraocular lens, a grading scales available, procedure which is now both routine and very successful in the e.g. Lens Opacities vast majority of cases. Often carried out by a small-incision Classification System III surgery, which gives minimal disruption and reduces the risk of post-surgical astigmatism. 11. Anterior eye disease

Questions and answers:

When presented with anterior eye scenarios in general practice, symptoms described by the patient will lead to the correct diagnosis most of the time and will help you distinguish between urgent and non-urgent cases.

A logical approach to clinical examination will help with management. The following are of paramount importance for any presentation of anterior red eyes:

• History taking. • Visual acuity assessment • Slit-lamp examination - both anterior and posterior • Fluorescein examination • Assessment of pupil reactions • Intraocular pressure assessment

Other tests may be required dependent on clinical presentation.

1. A 14 year old Caucasian male attends your practice with bilateral red eye. Upon further questioning he reports the following symptoms: itchiness, ropy discharge, FBS.

a) State your provisional diagnosis from the information provided.

b) What clinical techniques would you use to examine this patient?

c) What is your management?

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Answers:

a) Vernal conjunctivitis - consider age, race and symptoms.

b) Visual acuity assessment, slit-lamp examination of the anterior eye with fluorescein and white light. a) State slit-lamp techniques - diffuse illumination (eyelids and adnexa assessment), Optic section, conical beam - for anterior chamber assessment of cells and flare. b) Lid eversion - assessment of palpebral conjunctiva. c) Media assessment of lens and vitreous d) Dilated Volk examination e) Pupil reactions assessment.

c) Referral to eye department: mast-cell stabilisers, antihistamines, steroids may be given for the treatment.

2. 10 year old Alexander attends your practice with his father, who has noticed his eyes keep going red.

a) Elicit a complete history and symptoms assessment.

b) Consider the age of the child and state your differential diagnosis.

Answers:

a) History and symptoms - information must be taken from father and child. Follow the LOFTSEA method for questioning. • Reason for visit - red eye. • Onset - acute or gradual - open question to parent: ‘when did you first notice the red eye?’ • Frequency - constant or intermittent. • ‘Are the eyes constantly red or is the redness intermittent?’ Further questions on this as follows: • ‘Have you noted a pattern? - worse in the morning or evenings? worse with certain activities e.g. swimming? • Location: One or both eyes affected? • Severity: can you grade the redness: mild/ moderate/severe? sectoral? • Associated symptoms: pain/ itchy eyes/ headaches/ blurred vision/ diplopia/ flashes or floaters. • Open question to parent: has your child complained of anything with the redness? • General health: recent colds or flu? Allergies? Asthma or eczema? • Have there been any changes to face products? • Are there pets? • Ocular history: previous episodes of red eyes? Any HES visits? • For completion: FOH/FGH/hobbies - e.g. certain activities, swimming, garden games

b) Diagnosis based on age: allergic conjunctivitis, dry eyes, seasonal allergy e.g. hay fever - causing red eyes, trauma.

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3. A 68 year old female complains of watery eyes during her routine examination. The watering is worse in the mornings alongside crusting of the eyelids; this has become worse gradually over 2 years. Ocular examination shows crusty lashes, irregular lid margins, large irregular tear prism and rapid tear break up time in both eyes. The tear drainage puncta are all normal looking and are in line with the globe. What would your management and advice be to the patient?

Answers: • Consider age • Consider symptoms • Blepharitis diagnosis Management and advice • Explain the chronic nature of condition to the patient. • Explain it may take 4-6weeks for significant improvement of symptoms. • Patient to use warm compress for 10mins/eye • Followed by eyelid hygiene - eyelid wipes • Ocular lubricants - to combat symptoms of dry eyes.

4. A 45 year old female presents with an acute unilateral red eye. She has no symptoms. Clinical picture as follows:

a) What can cause this clinical presentation? b) What would your management be?

Answers: a) Causes of subconjunctival haemorrhage: a) Trauma b) HIV/AIDS c) Blood disorders d) Medication: warfarin, aspirin, other blood thinners e) Increased venous pressure (e,g, coughing, sneezing, or straining) f) Hypertension g) Idiopathic. © 2021 Specsavers Ltd 103 < Section B Clinical case management of ocular conditions

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b) Management: a) Complete H&S b) Reassurance to patient - generally self-resolving in 1-2weeks. c) Cold compresses - for 10mins/eye - 2-3x/day for 1week. d) Ocular lubricants for FBS - if cause of trauma, FB in eye. e) Monitor blood pressure esp. if recurrent.

5. 50 year old Mrs. Smith presents with a unilateral red eye.

Read the history and symptoms provided below and answer the following questions:

a) State your provisional diagnosis

b) What clinical investigative techniques would you use to examine Mrs. Smith?

c) What would your management be?

History and symptoms:

RFV - unilateral red eye Noted initially 4 days ago, gradually worse - right eye affected. No discharge. Eyes watering. Mild redness sectoral inferior temporally. Pain - deep boring ache. No itchiness. Mild photophobia. No flashes. No headaches. No floaters. No diplopia. Vision ok - px wears varifocals full time. General health: rheumatoid arthritis - diagnosed 4 years ago. Medication: methotrexate 10mg taken 1x/week for the past 3 years. Ocular history: no hospital visits. No ocular conditions reported. Red eye presentation not occurred previously. FOHx: & FGHx: no relevant issues Driver - yes Occupation - admin VDU use - 6-8hrs/day Hobbies: yoga, family, socialising.

Answers:

a) Consider: gradual onset sectoral redness, unilateral, painful eye. Hx: of arthritis Diagnosis: scleritis DD: uveitis, episcleritis

b) Clinical investigations: a) Visual acuity assessment b) Pupil reactions c) Intraocular pressure assessment d) Fluorescein anterior assessment on slit lamp e) Van Herick’s assessment. f) Lid eversion g) Assessment of the anterior chamber for cells and flare. h) Posterior eye assessment with slit-lamp Volk.

c) Refer to eye department - emergency. Systemic steroids may be given.

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6. Mr AB presents for an eye examination with a confluent red eye and reduced vision.

H&S reveals he takes corticosteroids post herpes virus attack 6months ago.

Intraocular pressures measure 34mmHg RE and 24mmHg LE

The right eye has significant hyperaemia and neovascularisation around the iris.

Right eye anterior photo shown below:

a) What is your likely diagnosis?

b) Upon clinical examination what other features do you expect to see?

c) What would your referral routine be?

Answers: a) Uveitis - consider IOP + medication: corticosteroids - risk of inflammation and ACG b) Other clinical features: a) Posterior anterior synechiae (if associated with angle closure)

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12. Vitreous

Many patients present to the optometrist with symptoms of floaters, and it is essential we determine the difference between benign and more sinister causes. A thorough and complete H&S is essential.

Key questions to ask patients presenting with floaters: 1) Onset - acute or longstanding? 2) Has the patient noted a change in size, shape or number of floaters? 3) Are the floaters associated with flashes? 4) Are the floaters coloured? 5) Associated with shadows? 12.1 Posterior vitreous detachment (PVD)

Age-related liquefaction of the vitreous resulting in the detachment of the vitreous from the retinal surface. High chance of retinal breaks.

Management: Generally no further action If retinal tear present - then refer Risk of RD is greatest within first 6 weeks. If PVD present with blood refer to eye casualty same day (unless px diabetic with known proliferative changes) 12.2 Vitreous haemorrhage

Can be a result of many factors: • Retinal tear • Proliferative diabetic retinopathy • Venous occlusions • Subretinal neovascular membrane Noted as darker opacities within the vitreous during slit-lamp microscopy.

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12.3 Asteroid hyalosis

Calcium deposits seen in the vitreous with slit-lamp examination Patient may have no symptoms. If the extent of calcium deposits affects VA - refer for vitrectomy

Signs Symptoms • Movement of the vitreous • Floaters - sudden onset described as: smoking ring, • Floating opacities flies, insects, dots. • Large calcium opacities (in asteroid hyalosis) • Flashes - occasionally - as a result of traction. • Weiss ring • Shadows in the vision or veil in the vision if • Schaffer's sign - if associated with retinal tear. associated with retinal detachment.

13. Vascular retinopathies and the retina

13.1 Diabetic retinopathy

New vessels at the disc R3 retinopathy requiring urgent referral. Description: Capillary occlusion and leakage lead to progressive retinal damage. Microvascular occlusion - leads to ischaemia - detected as: cotton wool spots, capillary closures, AV shunts, neovascularisation. Microvascular leakage - occurs as a result of the breakdown of the blood-retinal barrier - detected as: retinal haemorrhages, retinal exudates/oedema. © 2021 Specsavers Ltd 107 < Section B Clinical case management of ocular conditions

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Cause: • Duration of diabetes • Hypertension • Diabetes • Glycaemic control reduced

Differential diagnosis: • Hypertensive retinopathy • Diabetic papillopathy • CRVO

Management: • Monitor every 2 years. • Diabetic retinal screening programme annual review. • Patient may have: intravitreal injection, laser photocoagulation, pan retinal laser dependent on retinal ischaemia. • Letter of notification if any changes noted at routine sight test.

Prognosis: Dependent on stage of DR changes.

Diabetic eye screening programme grading definitions

Signs Symptoms • Background diabetic retinopathy - micro-cysts, • None haemorrhages, exudates, cotton wool spots. • Reduced central vision if maculopathy involved. • Pre-proliferative retinopathy - venous irregularities • Floaters sudden onset - if vitreous haemorrhage. (bleeding, looping, duplication), Multiple retinal • Reduction of VA haemorrhages, IRMA, multiple cotton wool spots. • Hyperopic shift in Rx. • Proliferative - neovascularisation, vitreous haemorrhage, fibrous tissue formation. • Exudates within 1 DD of macula - sign of maculopathy

13.2 Hypertensive retinopathy

Description: Arteriosclerosis (thickening and hardening of blood vessels) over many years results in the progressive retinopathy (i.e. leakage and occlusion of blood vessels causing retinal damage)

Cause: • Hypertension • Pulmonary artery disease • Vascular conditions

Differential diagnosis: Diabetic retinopathy CRVO

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Management: Urgent referral if blood pressure is abnormally high - refer as emergency!

Prognosis: Dependent on prompt action.

Signs Symptoms • Arteriolar narrowing • Patient may have Hx of: • Arteriosclerosis changes - exaggeration of light headaches, blurred vision, fluctuating vision, reflex, nicking, venous compression. palpitations. • Nerve fibre haemorrhages - flame shaped. • Cotton wool spots • Macular star • Tortuosity of blood vessels • Dilated veins.

13.3 Branched retinal vein occlusion

Description: Thrombus at the AV crossings results in compression of the vein.

Cause: as described above. • Arteriosclerosis • Diabetes • Hypertension • Other vascular conditions

Differential diagnosis: Hypertensive retinopathy BRAO

Management: Urgent within 1 week referral If associated with oedema - laser treatment and intravitreal injections.

Prognosis: Good dependent on prompt management.

Signs Symptoms • Flame/ dot/ blot haemorrhages in one quadrant • Blurred vision - sudden - if macular area affected. • Macular oedema - dependent on proximity of • Previous Hx of amaurosis fugax attacks. occlusion. • TIA Hx • Cotton wool spots • Stroke Hx • Neovas/vitreous haemorrhage • Rarely neovascular glaucoma.

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13.4 Central retinal vein occlusion

Description: Thrombus within the lamina cribrosa region causes a compression of the central retinal vein.

Cause: • Hypertension • Hyperlipidaemia • Diabetes • Hyperviscosity of the blood • Smoking • POAG • Rarer causes.

Differential diagnosis: CRAO Hypertensive retinopathy

Management: Refer as emergency

Signs Symptoms • Flame/dot/blot haemorrhages in one quadrant • Sudden loss of vision • Macular oedema - dependent on proximity of • Blurred vision occlusion. • Distortion - due to macular oedema. • Cotton wool spots • Neovas/ vitreous haemorrhage • Rarely neovascular glaucoma.

13.5 Branched retinal artery occlusion

Description: Emboli within a branch of arteries causing an occlusion.

Cause: • Hypertension • Hyperlipidaemia • Diabetes • Giant cell arteritis

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Management: • URGENT referral - if macular area affected EMERGENCY - As the foveal circulation needs to improve. • Systemic checks • Blood tests e.g. erythrocyte segmentation rate and C-reactive protein tests.

Signs Symptoms • Areas of retinal ischaemia • Unilateral vision loss • Narrowing of arterioles and venules • Previous episodes of: amaurosis fugax attacks. • Oedema • TIA/stroke. • Look out for areas of pallor in dilated Volk assessment.

13.6 Central retinal artery occlusion

Description: The occlusion of the central retinal artery - which is the principal supply to the retina.

Cause: • Giant cell arteritis • Collagen vascular diseases • Hypertension • Diabetes

Management: • Ocular massage - to lower IOP • Increase blood flow and dislodge emboli • Anterior chamber paracentesis.

Signs Symptoms • Reduced VA 3/60 to hand movements - central vision • Sudden, severe and unilateral painless vision loss may be preserved in 20% of cases. • Amaurosis fugax attacks • RAPD • if associated with GCA - patient may complain of: • Emboli within the retina may be visible jaw claudication, • Retinal pallor. • Cherry-red spot

13.7 Age-related maculopathy

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NICE guidance of AMD

NICE classification of AMD

Two forms: dry and wet

Wet type: aetiology, signs and symptoms • Central serous detachment of the retina due to leakage from new vessels which have formed from the choroid and passed through breaks in Bruch’s membrane. • Patients experience visual distortion, best identified with the Amsler grid. • Sometimes marked deterioration of vision, progressing to difficulty with hand movements within weeks.

Dry type: aetiology, signs and symptoms • Usually starts as a collection of drusen at the macula, then pigment begins to show at the macula. • Over a period of years, slow deterioration of visual acuity, particularly near vision. • Eventually the patient will require low vision aids.

Classification of AMD (from NICE 2018) Normal eyes • No signs of age-related macular degeneration (AMD) • Small ('hard') drusen (less than 63 micrometres) only Early AMD Low risk of progression: medium drusen (63 micrometres or more and less than 125 micrometres) or pigmentary abnormalities Medium risk of progression: large drusen (125 micrometres or more) or reticular drusen or medium drusen with pigmentary abnormalities High risk of progression: large drusen (125 micrometres or more) with pigmentary abnormalities or reticular drusen with pigmentary abnormalities or vitelliform lesion without significant visual loss (best-corrected acuity better than 6/18) or atrophy smaller than 175 micrometres and not involving the fovea Late AMD (indeterminate) Retinal pigment epithelial (RPE) degeneration and dysfunction (presence of degenerative AMD changes with subretinal or intraretinal fluid in the absence of neovascularisation) Serous pigment epithelial detachment (PED) without neovascularisation Late AMD (wet active) Classic choroidal neovascularisation (CNV) Occult (fibrovascular PED and serous PED with neovascularisation) Mixed (predominantly or minimally classic CNV with occult CNV) Retinal angiomatous proliferation (RAP) Polypoidal choroidal vasculopathy (PCV) Late AMD (dry) Geographic atrophy (in the absence of neovascular AMD) Significant visual loss (6/18 or worse) associated with: dense or confluent drusenor advanced pigmentary changes and/or atrophy or vitelliform lesion Late AMD (wet inactive) Fibrous scar Sub-foveal atrophy or fibrosis secondary to an RPE tear Atrophy (absence or thinning of RPE and/or retina) Cystic degeneration (persistent intraretinal fluid or tubulations unresponsive to treatment) NB Eyes may still develop or have a recurrence of late AMD (wet active)

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13.8 Retinal detachment

Definition: A separation of the neurosensory retina from the underlying retinal pigment epithelium.

Cause: • Trauma • High refractive error • PVD Generally as a result of fluid passing through the break and separating retinal layers

Management: EMERGENCY referral - if affecting macular area URGENT (within 1 week referral) - if macula area not affected Note: ensure you check your local protocol MECS/EOS accredited optometrists - dilated fundus exam.

Signs Symptoms • Fundus surface on Volk assessment looks • Floaters distorted and the blood columns darken suddenly as • Flashing lights the blood vessels pass from the normal area of • ‘Curtain’ across the visual field detachment.

13.9 Retinoschisis

Definition: A splitting of the neurosensory retina.

Aetiology, signs and symptoms: • Usually occurs in elderly patients. • The result of peripheral retinal cysts coalescing to form larger and larger cysts. • Resembles retinal detachment, but schisis produces an absolute and irreversible scotoma, because it breaks the visual pathway. • Unlike detachment, this is not an ocular emergency.

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14. Glaucoma

Glaucoma or glaucomatous optic neuropathy is a progressive condition affecting the optic nerve head. Characteristic loss of the neuroretinal rim tissue occurs with specific functional defects detectable by visual field testing. Studies show intraocular pressure seems to play a significant role.

There are primary and secondary glaucomas.

The diagnostic triad, i.e. intraocular pressure measurement, optic nerve head examination and visual field assessment, can help with detection and management of the condition.

There are key optic nerve signs of glaucomatous optic neuropathy 1) Vertical elongation of the physiological cup 2) Loss of the neuroretinal rim - characteristic in the supratemporal and infra-temporal rim 3) Appearance of haemorrhages - drance or splinter. 4) Peripapillary atrophy 5) Bayonetting of blood vessels. 6) Nasal shift in blood vessels. 14.1 Primary open-angle glaucoma (POAG)

Description: A progressive optic neuropathy in which the anterior chamber drainage angle is open.

Cause: High intraocular pressure Ischaemia

Risk factors: • Age • Myopia > 4D • Hypertension • Cardiovascular and cerebrovascular condition • Race • Thin corneas • Diabetes • POAG in fellow eye • NIAON in fellow eye.

Management: Early detection and review are important. Annual eye examinations for: positive family Hx - only 1st degree relatives. Topical treatment. Laser treatment

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Signs Symptoms • IOP>21mmHg diurnal variation • Asymptomatic • Increase in the vertical CD ratio • Later stages tunnel vision • Thinning and notching of the NRR • Appearance of drance and splinter haemorrhages. • RAPD in advanced and asymmetric cases • Defects of the visual field characteristic of the horizontal midline.

14.2 Normal tension glaucoma (NTG)

Description: A primary open angle glaucoma variant where the IOP is within normal limits

Cause: Studies show a link between: Raynaud’s disease, migraines, vasospasm, nocturnal hypotension.

Differential diagnosis: POAG Other secondary glaucomas Optic atrophy

Management: A treatment regimen should be instituted for those patients where progress in disease has been early demonstrated. Treatment aimed to lower IOP by medical or surgical means and reduction of IOP of the order of 30% may be needed to halt progression.

Signs Symptoms • IOP within normal range. • Asymptomatic • Gonioscopy reveals open angles • Optic disc changes same as POAG

14.3 Ocular hypertension

Description: Patients who have IOP >24mmHg (NICE guidelines) with normal optic discs and visual fields; however, these patients need close monitoring.

Management: Assess the central corneal thickness. Assess IOP, fields and optic nerve closely - every 4 months, 6 months or yearly - dependent on risk of glaucomatous optic neuropathy development. Other risk factors considered: age, family Hx, IOP level, CCT

Signs Symptoms • IOP persistently elevated • None • Normal anterior chamber appearance

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14.4 Primary angle closure glaucoma

Description: A group of conditions where there is irido-trabecular adhesion or apposition.

Note there are different forms: Acute angle closure Intermittent angle closure (where symptoms are mild) that can lead to chronic angle-closure glaucoma, which can cause: • Disc cupping • VF damage • IOP >21mmhg • Gonioscopy shows areas of apposition.

Cause/risk factor: • Positive family history • Age over 40-50 years • Women • Chinese ethnicity • High hyperopia • Short axial length

Differential diagnosis: Uveitis Traumatic ACG

Signs Symptoms • Elevated top • Decreased vision • Conjunctival injection • Haloes around light • Corneal epithelial and stromal oedema • Headaches • Shallow or flat anterior chamber. • Pain • Mid-dilated pupil with absence of reactivity • Nausea or vomiting. • Hyperaemia.

14.5 Secondary glaucomas

Represents a group of conditions with a wide range of causes and clinical manifestations that result in glaucomatous optic neuropathy (GON). The secondary GONs are open-angle, closed-angle glaucoma or congenital type.

14.5.1 Pigmentary glaucoma

Description: Represents an association between pigment dispersion syndrome and glaucomatous optic neuropathy

Open-angle type.

Mechanism: Rubbing of the lens zonules and iris pigment epithelium releases pigment - which deposits onto the trabecular meshwork leading to blockage and IOP fluctuations.

Clinical picture: Young male Caucasian decent Myopic

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Signs • Mid-peripheral iris transillumination defects • Krukenberg spindles • Wide open angles • Sampolesi’s line - with gonioscopy • IOP fluctuations.

14.5.2 Pseudoexfoliation glaucoma

Description: Ocular manifestation of an inflammatory systemic disorder. Flakes and sheets of exfoliative material can present on anterior eye structures.

The common sites of deposition being: • Lens • Ciliary body • Iris pigment.

Common in: Danish, Scandinavian, Greek origin: males > females

Clinical features: • Translucent deposits on the anterior lens capsule (bull’s eye effect) • Atrophy and transillumination of iris sphincter. • Nuclear cataracts • Pigment on corneal endothelium • Higher IOP

14.5.3 Inflammatory uveitic glaucoma

Description: When recurrent episodes of uveitis result in glaucomatous optic neuropathy. IOP is higher than average. Visual field defects and optic nerve damage occur.

Associated with: • Herpes uveitis • Keratouveitis • Fuchs' iridocyclitis • Juvenile arthritis • Toxoplasmosis • Sarcoidosis

Prognosis: Dependent on management.

Signs Symptoms • Inflammatory cell deposition on trabecular • Unilateral red eye meshwork - after episodes of uveitis • Painful • Posterior anterior synechiae may be present. • Photophobic • Neovascularisation may be present if associated with • Lacrimation ischaemia. • Anterior chamber cells and flare.

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15. Neuro-ophthalmology

It is important for all optometrists to look out for signs and symptoms related to neurological conditions For any neuro-ophthalmic presentation in optometry the following clinical tests are of paramount importance: • History and symptoms - ask about headaches, visual symptoms e.g. diplopia, flashes, floaters, sudden vision loss. • Visual acuity assessment • Pupil reactions • Stereoacuity • Goldmann perimetry equivalent e.g. SITA fast programme on Humphrey's • Amsler assessment • Colour vision assessment. • Ocular motility • Dilated anterior and posterior slit-lamp examination. 15.1 Retrobulbar neuritis

Description: Inflammation of the optic nerve due to some demyelinating disease.

Cause: Tuberculosis Syphilis Multiple sclerosis Viral infections

Differential diagnosis: Anterior Ischaemic optic neuropathy Papilloedema Non-arteritic ischaemic optic neuropathy.

Management: Urgent within 1 week referral

Prognosis: Good but risk of recurrence

Signs Symptoms • RAPD • Blurred vision • Vision loss • Pain on eye movement. • Central scotoma on visual fields • Red desaturation • Blurred disc margins • Swollen veins

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15.2 Arteritic ischaemic optic neuropathy (AION)

Description: Inflammation of the optic nerve as a result of ischaemia.

Risk factors: Hypertension Smoking Diabetes Stroke Sleep apnoea Anaemia

Differential diagnosis: NAION Papilloedema

Management: Emergency referral

Signs Symptoms • Pallor of the optic disc • Systemic - headache, pain in the neck and temples, • Peripapillary haemorrhages Loss of weight, fatigue, scalp tenderness. • Temporal artery thick and pulsating • Ocular - sudden, profound and permanent. Vision loss is preceded by amaurosis fugax attacks.

15.3 Non-arteritic ischaemic optic neuropathy (NAION)

Description: Inflammation of the optic nerve as a result of ischaemia - not related to inflammation of arteries.

Cause: Drop in blood pressure Increased blood viscosity Reduced blood flow around the optic nerve.

Risk factors: Same as AION

Management: Emergency referral

Signs Symptoms • Altitudinal hemianopia - on visual fields • Vision loss suffer but not severe and painless. • Diminished colour vision • Fundus with pallor. • Fellow eye has smaller or absent cup.

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15.4 Papilloedema

Description: Inflammation of the optic nerve as a result of raised intracranial pressure

Cause: • Brain tumour • Meningitis • Hydrocephalus • Pseudotumour cerebri.

Differential diagnosis: • AION • Diabetic papillopathy

For all conditions it is important to consider the local protocols

Signs • Mechanical - elevation of ONH, blurring of disc margins, filling of the physiological cup, oedema of the RNFL. • Vascular - loss of SVP, venous engorgement, haemorrhages adjacent to optic disc.

16. Key issues: pupils

16.1 Marcus-Gunn pupil

Definition and signs: • Direct reflex is absent or reduced. • Consensual reflex is normal. • Check with swinging flashlight test: • light in affected eye - little or no response. • light in normal eye - normal response and consensual reflex constricts pupil of affected eye. • light back into affected eye - pupil dilates

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16.2 Holmes-Adie pupil

Definition, signs and symptoms: • Idiopathic condition which mainly affects young women. • Tends to be unilateral. • Pupil tends to be dilated with absent or poor light reflexes. • Constriction is slow with prolonged accommodation, and redilation is also slow. • Very dramatic constriction is produced with 0.10% pilocarpine which is the basis for a clinical test for Adie’s pupil. • Tendon ‘jerk’ reflexes may be absent 16.3 Argyll-Robertson pupil

Signs and symptoms: • Bilateral condition in which both pupils are small. • Poor or absent response to direct light but good response to near stimulation. • Has been seen in diabetes, but is strong evidence of neurosyphilis. 16.4 Pupillodilator dysfunction (Horner’s syndrome)

Definition, signs and symptoms: • Triad of signs: ptosis, miosis, and (if lesion is below superior cervical ganglion) anhydrosis on the same side. The affected pupil is miosed but still retains the light and near reflexes.

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Testing Pupils: This is an important part of every eye examination; sight- and life-threatening disorders can be detected using a few simple techniques and tests.

Step 1: Check for the presence of anisocoria. Anisocoria = a difference between the size of the pupils. Methods: Use a direct ophthalmoscope • Have a low powered lens in view • Illuminate the pupils roughly 20cm away. If anisocoria is detected you must test in different illumination conditions. a) to allow you to detect the abnormal pupil b) to allow you to perform a differential diagnosis on the efferent defect that would have caused this. Note: Anisocoria increase in dim light = sympathetic problem Anisocoria increase in bright light = parasympathetic problem

Step 2: Check the light reaction Ask the patient to look at a non-accommodative target at 6m. First check direct and then consensual light reflex. You want to perform this at least 3x to see if the pupil is reacting properly. After RE move onto the LE.

Step 3: Check the near reflex (this step should only be performed if pupil reactions are abnormal) Give the patient a target @ near (e.g. budgie stick line above the worst eye VA) Distance target e.g. line above the VA of the worst eye. Patient looks at the ‘near target’ then ‘distance target’ = assess the pupil size change. Note: You can get situations where the light reflex is abnormal but the near reflex is normal. Known as: near-light dissociation. Causes: Viral infections (Adie’s tonic pupil) Damage to the pre-tectal area (Parinaud’s syndrome) Damage to the rostral mid-brain (Argyll-Robertson pupil)

Step 4: The swinging-flashlight test Essentially shine the light on one eye for 3-4 secs, then quickly swing across to the other eye. Repear 3-4 times. RAPD response: An eye with an RAPD will dilate even when direct light is shining upon it. This is because the consensual response to dilate is stronger than the direct response to constrict from the afferent pathway. Note: if there is an equal input to brain from afferent pathway in each eye you will not get an RAPD. It is a relative difference between the input from the two eyes that can lead to responses. It is an afferent pathway defect.

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17. Posterior eye disease questions and answers

1. A 54 year old female presents for an eye exam reporting her near vision has become worse gradually since her last eye exam.

Fundus examination shows the following for both eyes

a) State your diagnosis.

b) What would your management be?

Answers: a) Epiretinal membrane b) Assess the visual acuity and Amsler: a) Generally monitor patients in 1 year's time b) Advise patients on flashes and floaters c) Give College or AOP leaflet on flashes and floaters. d) Hand patient an Amsler chart for regular monitor - at least 1x in 2 weeks. e) If VA reduced on ocular examination with distortion - vitrectomy can be performed - refer as urgent within 2 weeks.

2. A 65 year old female complains her vision has become gradually worse, especially for close work. Her spectacles do not seem to help. She is diabetic.

Her prescription today is below: RE +4.50/-0.25x90 VA 6/20 LE +2.50/-0.25x100 VA 6/6

Near add +3.00 RE N12 LE N6

a) What is your diagnosis?

b) What clinical investigations would you perform to confirm your diagnosis?

c) What will your management involve?

Answers: a) Wet macular changes b) Amsler test, IOP, OCT examination. c) Refer URGENT within 2 weeks or AMD fast track. a) Treatment options: laser photocoagulation, anti-VEGFs, single and combination treatment.

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3. 65 year old Mr. Smith presents for a routine examination after 4 years. No symptoms reported. He suffers from Raynaud’s syndrome and high blood pressure. Medications taken are ramipril 10mg daily. Slit-lamp Volk examination shows the following:

a) State your differential diagnosis. b) What clinical tests would you perform? c) Describe the optic nerve head features.

Answers: a) NTG, POAG. b) IOP, fields, OCT. c) Judging from the position of vessels and true edge of disc, right CD ratio estimated to be 0.8 and left CD ratio 0.9. Both optic discs show superior and inferior rim thinning and some bayonetting of vessels. Neither follows the ISNT rule.

4. A 32 year old female presents complaining of blurred vision for the left eye noted first 1 week ago and pain on movement of the eyes. She has never experienced this before. General health is OK; however, she has been feeling tired over the last 6months especially after drinking hot beverages. a) State your diagnosis. b) What other clinical tests would you need to perform to confirm the diagnosis?

Answers: a) Retrobulbar neuritis, optic neuritis, change in Rx, cataracts b) Visual acuity assessment, pupil reactions, slit-lamp biomicroscopy, OCT, visual fields assessment, ocular motility assessment.

< Ocular disease and abnormality

Handy Hints

• When examining a patient's eyes with a slit lamp or ophthalmoscope, if you find something that isn't physiological, avoid immediately jumping to a diagnosis.

• Always begin by describing what you see as this will ensure that you don't miss anything (equivalent to showing your working/thought process).

• Then create a differential diagnosis list of what it might be, ranking in order of likelihood based on what you know of history, symptoms and the other clinical findings.

• Always bear in mind what is known in the medical profession as red flags. Essentially red flags are signs and symptoms found in the patient history and clinical examination that may tie a disorder to a serious pathology. These are findings which indicate that there is imminent threat to sight or threat to life. The concept of red flags is very important to be aware of in primary care and findings should be acted upon with the relevant level of urgency.

• Remember that there are many conditions that will either self-resolve or can be managed by an optometrist. Find out what you can do within your scope of practice that helps build the trust in your professionalism and avoids unnecessary referrals to secondary care.

Reflective Exercises

1. Keep an ongoing diary of each pathology you see in practice. Record whether the presentation was textbook or has atypical features. Make notes on the pathology from two different ocular pathology text books.

2. Arrange to sit in a diabetic retinopathy grading clinic. Practise grading each patient you see: R0, R1, R2 or R3

3. When you examine a patient with diagnosed glaucoma try and predict the location and degree of field loss present

4. Complete the local minor eye conditions pathway training, so you can be ready to help your supervisor manage a wide range of examinations

< Use of diagnostic and therapeutic drugs

Use of diagnostic and therapeutic drugs

1. General information...... 128

2. Core theoretical topics...... 128

3. Core practical topics...... 128

4. Key issues: definitions and designations...... 129 4.1 The Human Medicines Act and use and supply of pharmaceuticals by optometrists...... 129 4.2 Independent prescribing and additional supply optometrists...... 130

5. Key issues: diagnostic drugs...... 130 5.1 The place of diagnostic drug use in optometric practice...... 130 5.2 The ophthalmic pharmaceutical...... 135 5.2.1 General characteristics (presentation)...... 135 5.2.2 Ingredients of ophthalmic pharmaceuticals (including contact lens solutions)...... 135 5.2.3 General properties of eye drops...... 135 5.2.4 Practical guidelines on use of eye drops, gels and ointments...... 136 5.3 Diagnostic drugs for optometric use...... 137 5.3.1 Saline solutions for irrigation...... 137 5.3.2 Topical ocular dyes and stains...... 137 5.3.3 Topical ocular anaesthetics...... 137 5.3.4 Viscous eye drops for gonioscopy...... 138 5.3.5 Drugs to dilate a pupil (mydriatics)...... 138 5.3.6 Drugs to relax the accommodation (cycloplegics)...... 139

6. Key issues: therapeutic drugs...... 140 6.1 The place of therapeutic drug use in optometric practice...... 140 6.2 Therapeutic drugs that can be used by optometrists...... 140 6.2.1 Eyewashes and astringents...... 140 6.2.2 Lid hygiene products...... 140 6.2.3 Artificial tears or contact lens rewetting solutions...... 141 6.2.4 Ocular lubricants...... 141 6.2.5 Ocular antihistamines...... 143 6.2.6 Ophthalmic anti-infectives...... 143

< Use of diagnostic and therapeutic drugs

7. Key issues: contact lens solutions...... 144 7.1 General properties...... 144 7.2 Soft lens solutions...... 144 7.3 Rigid lens solutions...... 145 7.4 Protein removing products...... 145 7.5 Rewetting drops...... 145

8. Essential reading...... 145

< Use of diagnostic and therapeutic drugs

1. General information This module obviously cannot cover the entire syllabus in detail. Other sources of information must be consulted; these could include: • The Electronic Medicines Compendium is freely accessible online and searchable, holding information about all UK licensed medicines in two formats: Summary of Product Characteristics (SPC) which is useful for professionals and the Patient Information Leaflet (PIL) which is written in more lay terms suitable for patients. https://www.medicines.org.uk/emc • The British National Formulary (BNF) and MIMS, available online and from bookshops (or maybe a recent old edition from your local GP). A BNF is a useful source for the yellow card scheme for reporting ocular adverse drug reactions (ADRs) to systemic medications or topical ocular pharmaceutics. • Technical literature and papers from manufacturers of contact lens solutions. • The Optometrists’ Formulary, available from the College; available online and within the College App. • Your undergraduate notes. 2. Core theoretical topics

• The difference between diagnostic and therapeutic pharmaceuticals and when each could be used • The unique characteristics of an ophthalmic pharmaceutical - Which drugs are available to you. - Why you use them and how to select the most appropriate. - Any possible side effects. - Interactions with any systemic medication and ocular effects of systemic medications. - Contra-indications from an ocular and systemic viewpoint. - Systemic effects following topical ocular presentation. - Details of preparations and reasons for that formulation. - Allergic responses, general and drug related. - Awareness of drugs used in ocular therapy; emergency and general practice. • The range of diagnostic drugs available to optometrists in The Medicines Act • The laws regulating the use and supply of pharmaceuticals by optometrists • Types of pharmaceutical and their use - Chemicals used as ophthalmic dyes and stains - Drugs used as topical ocular anaesthetics - Drugs used to dilate the pupil - Drugs used to relax the accommodation - Drugs used to relieve dry eye symptoms - Drugs used to relieve slight redness of the eye due to irritation (ophthalmic decongestants and antihistamines) - Drugs used to prevent or reduce the chance of bacterial conjunctivitis or mild keratitis developing (ophthalmic antibacterials and broad-spectrum antibiotics) 3. Core practical topics

• The identification and checking of ophthalmic pharmaceuticals • The assessment of a patient prior to use of diagnostic or therapeutic drugs • The administration of ophthalmic pharmaceuticals • The assessment of the effects of diagnostic and therapeutic drugs on the eye • Appropriate patient counselling and aftercare 128 © 2021 Specsavers Ltd < Section B Clinical case management of ocular conditions

< Use of diagnostic and therapeutic drugs

4. Key Issues: definitions and designations

4.1 The Human Medicines Act and use and supply of pharmaceuticals by optometrists

Pharmaceuticals have a small symbol on them to designate their category of use: GSL (General Sales List), P (Pharmacy) or POM (Prescription Only Medicines).

SL/GSL pharmaceuticals are available to the public at large without any special consultation; non- medicinal and cosmetic products have the same availability. An ‘SL’ or ‘GSL’ marking will not generally be found on these types of product. Within this category are numerous contact lens-related products and a number of non-medicinal eye moisurisers. Classified as medical devices in the UK by the MHRA, these currently carry “CE” markings.

P medicines are generally available to the public at large but are supplied or sold only after a specific request to a registered pharmacist or other designated professional. Optometrists may use and supply P medicines in the course of their professional practice. A ‘P’ marking will appear on these products.

POM products are for professional use or are made available to the public at large only via prescription. Optometrists may use designated POM products. A ‘POM’ marking will appear on all of these pharmaceuticals.

No pharmaceutical should be used on the eye when there is a known allergy to the drug, or to any of the other ingredients of the pharmaceutical (excipients eg the buffers, preservatives, stabilisers, etc).

Medical prescriber - a person with a medical degree, such as a consultant ophthalmologist, dentist, GP or hospital doctor.

Non-medical prescriber - a person who has a special exemption to prescribe certain medicines as part of their professional practice. Non-medical prescribers can include nurses, optometrists, pharmacists, physiotherapists, podiatrists and therapeutic radiographers. The Human Medicines Act and its updates specifies which medicines may be used, which may be supplied and which may be prescribed. There are normally specific lists of medicines and rules for each registered professional.

Legal classification of licensed medicines:

• Prescription only medicines require a prescription to be written by an approved prescriber. They are subject to the additional requirement that they are sold or supplied with an appropriate practitioner’s prescription. A drug is off-licensed or ‘off-label’ when it is a licensed drug prescribed for a purpose for which it is not its described purpose. This is different to unlicensed, when the drug has not been approved for any purpose. Optometrists cannot prescribe unlicensed medicines.

• Pharmacy medicine can only be sold through a registered pharmacy under the personal supervision of a pharmacist.

• General sales list medicines can be sold in general shops as well as through pharmacies, often in small quantities. All of the products are sold in the manufacturer’s original packs.

• Over the counter medicine is a generic term that covers both general sales list and pharmacy medicine. Where the same drug is available in more than one legal classification, the licensed indications for its use may differ.

• Medical devices: Some ocular lubricants and contact lens comfort drops may be marketed as medical devices.

< Use of diagnostic and therapeutic drugs

4.2 Independent prescribing and additional supply optometrists

Only optometrists with a minimum of two years post-registration experience can complete the extra training needed to be ‘independent prescribing’ or ‘additional supply’ optometrists. In order to gain the necessary acreditation the optometrist needs to undertake a post-graduate course accredited by the GOC and the National Prescribing Centre.

Further information can also be obtained from the GOC and the College formulary.

Patient Group Directions (supply or administration)

A Patient Group Direction (PGD) is a written instruction for the supply or administration of medicines to groups of patients who may not be individually identified before presentation for treatment. It is not a form of prescribing and there is no specific training that health professionals or optometrists must undertake before they are able to work under a Patient Group Direction. However, certain requirements apply to the use of Patient Group Directions. Any optometrists may be part of a scheme where they are able to use or supply medicines subject to the PGD instructions. There will be a named clinical lead, normally a GP or ophthalmologist; you must ensure you have had suitable training and understand the nature of the PGD before using or supplying drugs by this mechanism.

An example: A group of local optometrists have been trained to perform post-operative cataract assessments. They are required to supply a bottle of a NSAID/ topical anti-infective to each patient to use for a month post surgery. An IP optometrist could issue such a prescription by virtue of their prescribing status; however all other optometrists could not. A PGD would enable all optometrists as part of the scheme to supply the required medications subject to the conditions set out in the PGD, under the clinical governance of the clinical lead, a medical prescriber. 5. Key issues: diagnostic drugs

5.1 The place of diagnostic drug use in optometric practice

A comprehensive examination of the external eye and refractive error cannot be done without at least considering the use of diagnostic drugs.

Fluorescein dye is required for any biomicroscopic examination of the ocular surface in any patient complaining of dry eye, allergies, contact lens wear-associated discomfort or intolerance, or any other condition where a change in the ocular surface is suspected. Accurate fitting of rigid gas permeable contact lenses also requires the use of fluorescein, while a special fluorescein derivative can be used for soft contact lenses. Use of fluorescein would be a normal part of contact lens aftercare assessment.

< Use of diagnostic and therapeutic drugs

Table 7 Ophthalmic preparations classified as pharmacy medicines: common examples

Drug category Drug Products containing drug Antihistamines Antazoline Otrivine-Antistin eye drops Azelastine Aller-eze eye drops Antimicrobials Chloramphenicol Boots Pharmacy antibiotic eye drops Galpharmvision antibiotic eye drops for conjunctivitis Numark chloramphenicol 0.5% eye drops Optrex Infected Eyes eye drops Dibrompropamidine isetionate Brolene, Golden Eye ointment Propamidine isetionate Brolene, Golden Eye drops Astringents Distilled witch hazel Optrex Sore Eyes eye drops Zinc sulphate Zinc sulphate eye drops BPC Mast cell stabilisers Lodoxamide Alomide allergy eye drops Sodium cromoglicate Boots Hayfever Relief allergy eye drops Clarityn allergy eye drops Dominion Pharma Hayfever eye drops Hay-Crom Hayfever eye drops Lloyds Hayfever Allergy eye drops Optrex Allergy eye drops Pollenase eye drops Vivicrom eye drops Ocular lubricants Carbomer 980 (polyacrylic acid) GelTears, Liposic, Viscotears Carbomer 974 (polyacrylic acid) Liquivisc Carmellose Celluvisc Dextran 70 Tears Naturale Hydroxyethylcellulose Minims Artificial Tears Hypromellose Artelac, Isopto Alkaline, Isopto Plain, Tears Naturale, Hypromellose eye drops Liquid paraffin Lacri-Lube, Lubri-Tears, Simple eye ointment BP Polyvinyl alcohol Liquifilm Tears, Liquifilm Tears preservative-free, SNO Tears Povidone Oculotect Sodium chloride Minims Saline Stains Fluorescein Minims Fluorescein Sodium Rose Bengal Minims Rose Bengal Sympathomimetics Naphazoline Optrex Red Eyes eye drops Phenylephrine Minims Phenylephrine Hydrochloride Xylometazoline Otrivine-Antistin eye drops

< Use of diagnostic and therapeutic drugs

Table 8 Common ocular preparations available to optometrists with relevant qualifications AS or IP

Drug/drug Available as: Brand name(s) Contains: Preservative Indication (and combination posology where appropriate) for P medicine Antibacterials (at entry level, use and supply for bacterial conjunctivitis only) Chloramphenicol Eye drops 5ml, Chloromycetin Chloramphenicol Phenylmercuric Treatment of 10ml and generic 0.5% acetate acute bacterial (POM) conjunctivitis, age 2 years Eye drops 10ml Boots Pharmacy Chloramphenicol Phenylmercuric and above, one antibiotic 0.5% acetate drop every 2h eye drops, for the first 48h Galpharmvision and 4-hourly antibiotic thereafter eye drops for conjunctivitis, Numark chloramphenicol 0.5% eye drops, Optrex Infected Eyes (P) Single-dose eye Minims Chloramphenicol None drops 0.5ml chloramphenicol 0.5% Eye ointment 4g Chloromycetin Chloramphenicol None and generic 1% (POM) Fusidic acid Eye drops 5g Fucithalmic Fusidic acid 1% Benzalkonium N/A chloride Antiallergics: antihistamines (use and supply for seasonal allergic conjunctivitis only) Emedastine Eye drops 5ml Emadine Emedastine Benzalkonium N/A 0.05% chloride Antiallergics: mast cell stabilisers (use and supply for seasonal allergic conjunctivitis only: Refer to IP optometrist or GP to prescribe any POM) Lodoxamide Eye drops 10ml Alomide (POM) Lodoxamide Benzalkonium Treatment 0.1% chloride of allergic conjunctivitis Eye drops 5ml Alomide Allergy Lodoxamide Benzalkonium in adults and (P) 0.1% chloride children over 4 years Nedocromil Eye drops 5ml Rapitil (POM) Nedocromil Benzalkonium N/A sodium 2% chloride DISCONTINUED 2018

continued overleaf

< Use of diagnostic and therapeutic drugs

Drug/drug Available as: Brand name(s) Contains: Preservative Indication (and combination posology where appropriate) for P medicine Sodium Eye drops 13.5ml Hay-Crom Sodium Benzalkonium Treatment of cromoglicate aqueous, cromoglicate 2% chloride acute seasonal Opticrom and perennial aqueous, allergic Vividrin and conjunctivitis generics (POM) Eye drops 5ml, Boots Hayfever Sodium Benzalkonium 10ml Relief, Clariteyes, cromoglicate 2% chloride Opticrom allergy, Optrex allergy, and Vivicrom (P and POM availble) Antiallergics: drugs with antihistamine and mast cell-stabilising activity (refer to IP optometrist or GP to prescribe) Azelastine Eye drops 8ml Optilast (POM) Azelastine Benzalkonium Treatment of hydrochloride Eye drops 6ml Aller-eze (P) hydrochloride chloride seasonal and 0.05% Benzalkonium perennial allergic Azelastine chloride conjunctivitis hydrochloride in adults and 0.05% children over 12 years Ketotifen Eye drops 5ml Zaditen (POM) Ketotifen 0.025% Benzalkonium N/A chloride Olopatadine Eye drops 5ml Opatanol (POM) Olopatadine 0.1% Benzalkonium N/A chloride Antiallergics: non-steroidal anti-inflammatory drugs (refer to IP optometrist or GP to prescribe) Diclofenac Eye drops 5ml Voltarol Ophtha Diclofenac 0.1% Benzalkonium N/A multi-dose chloride Single-dose eye Voltarol Ophtha Diclofenac 0.1% None drops 0.3ml Drugs used in the treatment of dry eye (use or supply) Acetylcysteine Eye drops 10ml Ilube (POM) Acetylcysteine Benzalkonium N/A 5% chloride Hypromellose 0.35% Carmellose Eye drops, Celluvisc Carmellose none N/A sodium solution, unit sodium 0.5% dose

In cases of moderate-to-severe dry eye, evaluation of the corneal and conjunctival surface is best supplemented with an evaluation after lisamine green staining. Check the GOC website for the current legal status of lissamine green.

For the measurement of intra-ocular pressure, applanation methods are the ‘gold standard’ against which any non-contact tonometry (NCT) reading can be checked if borderline or abnormal. Such applanation tonometry requires the use of a topical anaesthetic.

Eye examinations, especially in diabetics may involve pupil dilatation with a mydriatic.

To follow up any uncertainty in refraction with a cycloplegic refraction (especially in children) cyclopentolate is available for use by all optometrists. Atropine can only be used by AS or IP optometrists. © 2021 Specsavers Ltd 133 < Section B Clinical case management of ocular conditions

< Use of diagnostic and therapeutic drugs

Table 9 Drugs that can be used by optometrists

Registered optometrists Provided it is in the course of your professional practice, as a registered optometrist, you may use, sell or supply the following medicinal products to a patient: • all medicinal products on a GSL • all P medicines, such as the following: • Antazoline (up to 1%) • Azelastine hydrochloride (up to 0.1% for the treatment of the signs and symptoms of allergic conjunctivitis • Dibromopropamidine isethionate • Fluorescein sodium • Levocabastine* (up to 0.05% for the symptomatic treatment of seasonal allergic conjunctivitis)* • Lodoxamide (up to 0.1% for ocular signs and symptoms of allergic conjunctivitis • Phenylephrine hydrochloride • Propamidine isethionate • Sodium cromoglicate (only for the treatment of acute seasonal allergic conjunctivitis or perennial allergic conjunctivitis and subject to a maximum strength of 2% for eye drops or 4% for eye ointment; products containing this substance are also subject to restrictions on maximum quantity which may be sold or supplied as a P medicine, i.e. not more than 10ml for eye drops and 5 g for eye ointment) • Various tear supplements and ocular lubricants • Xylometazoline hydrochloride. Optometrists may use the following in the course of their professional practice: • Cyclopentolate hydrochloride* • Fusidic acid* • Tropicamide*. (*These may also be supplied by writing a signed order) • Benoxinate (oxybuprocaine) • Proparacaine (proxymetacaine) • Lidocaine (lignocaine) Provided it is in the course of your professional practice and in an emergency, as a registered optometrist, you may sell or supply POMs which are not for parenteral administration and that: • are eye drops and contain not more than 0.5% chloramphenicol or • are eye ointments and contain not more than 1% chloramphenicol • contain the following substances: o Cyclopentolate hydrochloride o Fusidic acid o Tropicamide. The following are Prescription-only medicines available to therapeutic optometrists with the Additional Supply qualification • Acetylcysteine • Atropine sulfate • Azelastine hydrochloride • Diclofenac sodium • Emedastine • Ketotifen • Lodoxamide • Nedocromil sodium • Olopatadine • Pilocarpine hydrochloride • Pilocarpine nitrate

< Use of diagnostic and therapeutic drugs

5.2 The ophthalmic pharmaceutical

The following should be considered:

5.2.1 General characteristics (presentation)

• Sterile and prepared by a registered pharmaceutical company.

• Specific expiration date stamped on the pharmaceutical (eg 01/2019) after which they should not be used.

• Diagnostic drugs are supplied in small plastic ampoules (Minims) for single use only, as individual wafers for single use (dyes and stains), or in larger (25 ml) plastic ampoules for single use only (salines).

• Therapeutic drugs can be supplied in small plastic ampoules (Minims) for single use only, or in 2.5-15ml bottles for repeated (multiple) use.

• All multi-use pharmaceuticals should be disposed of within one month of being opened for use (unless designated otherwise).

5.2.2 Ingredients of ophthalmic pharmaceuticals

(including contact lens solutions)

• A vehicle (solution) of saline, or saline buffered with chemicals such as phosphate buffer, or borate buffer; the label may also state that alkali (NaOH) or acid (HCl) has been added to adjust the pH.

• An active chemical or drug whose concentration is usually defined in terms of the amount per 100 ml, eg 0.5% is 0.5g/100 ml.

• Eye drops will often contain chemicals designed to increase the viscosity; these may be referred to as viscolisers or polymers (eg hypromellose, hydroxyethylcellulose, polyvinyl alcohol, Carbomer).

• If intended for repeated use, they will contain chemicals to reduce microbial growth, identified as preservatives (eg benzalkonium chloride, cetrimide, polidronium), unless specifically designated as ‘preservative-free’.

• Chemicals that should stabilise the active ingredient may be included or to buffer the solution to be more like the pH of tear film.

• Ophthalmic paper wafers are impregnated with a chemical (eg fluorescein).

5.2.3 General properties of eye drops

• Designed to be non-toxic.

• Designed to be compatible with the tear film in terms of pH and osmolality (tonicity) but will generally disrupt the tear film for several minutes (after which they may improve tear film stability).

• Designed to be relatively comfortable, but will often elicit a stinging sensation. This may be listed as an adverse drug reaction (ADR) but is almost invariably short-lived (transient).

• Any ingredient in an eye drop can cause an allergic reaction. The chance of progressive sensitisation to a drug, a viscoliser, a preservative or a stabiliser is likely to increase with repeated exposure; contact lens wearers are thus more likely to develop allergies to ingredients of contact lens care solutions.

< Use of diagnostic and therapeutic drugs

5.2.4 Practical guidelines on use of eye drops, gels and ointments

Ophthalmic pharmaceuticals are sterile* on presentation and will only remain so if they are not contaminated by inappropriate handling and use.

Eye drops

With the patient sitting comfortably, ask them to tilt their head back slightly, open their eyes and look up. The lower lid can then be gently pulled down (see Figure 24) and a single eye drop instilled into the pouch of the lower cul-de-sac. The tip of the eyedropper should be at least 1 cm from the surface of the eye. After instillation, the lower lid should be released, the eyelids closed (ask the patient to close their eyes) and the eyelids held lightly closed for 30 to 60 seconds which can help reduce the quantity of drug that enters systemic absorption via the punctal drainage.

Figure 24 Instillation of eye drops (Video)

Figure 25 Application of ointment

Ophthalmic gels and ointments

Follow the same procedure as for eye drops, but extrude a 1cm ribbon of gel or ointment along the inner side of the eyelid (Figure 25). The eyelids should then be closed, whereupon eye movements will help disperse the gel or ointment across the ocular surface.

* ‘Sterile’ compared with ‘disinfected’. Disinfection reduces the number of most infective agents. Sterilisation, in contrast, kills all infective agents (including bacterial spores and viruses).

< Use of diagnostic and therapeutic drugs

5.3. Diagnostic drugs for optometric use

5.3.1 Saline solutions for irrigation

Saline solutions for irrigation are provided in small (10-25ml) plastic ampoules for single use. Saline solutions are indicated to irrigate the eye to facilitate examination and to remove excess dyes and stains. They should be discarded after use.

5.3.2 Topical ocular dyes and stains

Fluorescein sodium ophthalmic wafers For single use only. Apply the yellow end of the wafer to the bulbar conjunctiva for a second or two to transfer dye. The wafer can be wetted with a single drop of sterile saline or artificial tears prior to application. Ask the patient to blink several times, then examine the ocular surface by biomicroscopy. CE marked as per medical device

Fluorescein sodium 1% eye drops Available in unit dose container for single use only. Instil single drop into lower cul-de-sac and ask the patient to close their eyes for several seconds. Enables assessment of tear film meniscus and nasolacrimal drainage. The eyes are best irrigated with saline after test is completed. P classification

Top Tip:

Check the GOC website to confirm the legal status of fluorescein sodium

Rose Bengal Discontinued in the UK

Lissamine green Lissamine green is an organic dye that is synthetically produced. Administered using a sterile saline moistened lissmine green impregnated strip. Best viewed with white light and is primarily useful for staining dead or damaged conjunctival cells, especially tarsal conjunctiva on lid margin and mucous strands. It is not useful for examining the cornea as it does not contrast well against the background of the iris in white light. Fluorescein is therefore the dye of choice for examining corneal integrity. CE marked as per medical device.

Top Tip:

Check the GOC website to confirm the legal status of lissamine green

5.3.3 Topical ocular anaesthetics

Practical guidelines Patients must always be advised when you need to use this type of drug. You should also advise them not to rub their eyes, nor reinsert contact lenses, for 30 minutes after they have left your consulting room.

For use of all anaesthetics, instil one drop into lower cul-de-sac and ask the patient to close their eyes for at least 15 seconds, after which they may blink. Wait three to five minutes to allow anaesthetic action to develop before proceeding with eye examination, tonometry, foreign body removal, etc.

< Use of diagnostic and therapeutic drugs

If applanation tonometry is performed, be sure to note the time it was done and the instrument used. Anaesthetics are classified according to their potential for causing allergies; cross-reactivity is not expected between groups. Four anaesthetics are available depending on use and need.

Oxybuprocaine 0.4% Available in unit dose container for single use only. A para-aminobenzoic acid ester. Refrigeration will improve stability, but is not required.

Proxymetacaine 0.5% Available in unit dose container for single use only. A meta-aminobenzoic acid ester. Must be refrigerated.

Tetracaine 0.5% Available in unit dose container for single use only. A para-aminobenzoic acid ester. For use when slightly longer lasting anaesthesia is required. Refrigeration will improve stability, but is not required.

Lidocaine 4% with fluorescein 0.25% Available in unit dose container for single use only. A benzoic acid amide. Helpful alternative to use when patients are allergic to aminobenzoic acid esters and when extended anaesthesia with fluorescein is needed. Refrigeration will improve stability, but is not required.

5.3.4 Viscous eye drops for gonioscopy

As an aid to the placement of a gonioscopy lens, and to facilitate its use, a viscous artificial tear product (eg containing 1% hypromellose or carboxymethylcellulose) is generally superior to saline. A drop or two should be applied to the lens surface prior to insertion.

5.3.5 Drugs to dilate a pupil (mydriatics)

General properties and use Mydriatics are required to enable an adequate examination of the inside of the eye and to produce a relative dilation of the pupil from that pupil diameter which would be adopted under moderate-to- high intensity illumination. At least a 6mm pupil is required for many instruments, and the larger the b et te r.

Patients should be informed that you intend to dilate their pupil, and the after-effects described, as these may have an impact on what they intend to do after the examination. Extra caution is advised if a patient intends driving a motor vehicle within 4-6 hours of a mydriatic being used.

Pupil dilation will generally take at least 20 to 30 minutes to occur and this requires special scheduling of patients. More than one eye drop may be required to dilate the pupil and this should be scheduled, rather than instilling eye drops in quick succession.

The use of a mydriatic is contra-indicated in routine optometric practice for patients with • A dislocation (subluxation) of the crystalline lens or an intraocular lens (IOL). • An iris-supported IOL in place.

A full medication history is essential prior to the use of any mydriatic because a patient may be taking medications that would either contra-indicate the use of a mydriatic, or could necessitate special attention and additional counselling.

Pupil dilation can cause some degree of discomfort (photophobia) and decrease in vision (primarily due to glare or cycloplegic effects) and patients should be advised of this; sunglasses can help relieve the discomfort. A patient should be instructed not to drive until they feel safe to do so, normally once the effects of the drops have subsided. Patients should be given an information leaflet

< Use of diagnostic and therapeutic drugs

Tropicamide as a mydriatic Tropicamide eye drops should be the first choice for a mydriatic.

Tropicamide 0.5 or 1% eye drops are available in unit dose container for single use only. The Minims containers are stamped TRO 0.5 or 1.0 and are unpreserved. Store at room temperature. There are no listed medical contra-indications (C/I) specific for the use of tropicamide eye drops, other than a known allergy.

Specific precautions (S/P) relate to concurrent use of any medication that could dilate a pupil, eg direct or indirect-acting sympathomimetics or serotonergic drugs, or drugs with parasympatholytic actions.

A single drop of tropicamide 0.5% should produce 2 to 3 mm dilation, but the magnitude of the dilation can be expected to increase either by using the 1% concentration or increasing the number of drops.

More than one drop of tropicamide should be considered for much older patients or patients with very darkly pigmented irides. Additional drops should be instilled at intervals of at least three minutes.

A patient can be told that their pupil should return to normal size within four to six hours following use of just one drop of 0.5% tropicamide. With larger doses, up to 18 hours may be required for full recovery. Tropicamide eye drops can also have some cycloplegic effects.

Phenylephrine-tropicamide eye drops as a mydriatic Phenylephrine is of little use as a mydriatic for the optometric consulting room when used on its own., but can be very usefully combined with tropicamide in some patients whose pupils are difficult to dilate. This combination is increasingly advocated where maximum dilation is required, such as when assessing the peripheral retina. It is up to your professional judgement to determine which mydriatics are clinically indicated.

A phenylephrine-tropicamide mediated pupil dilation requires the use of a phenylephrine eye drop followed by a tropicamide eye drop.

Phenylephrine 2.5% is available in unit dose containers for single use only. The containers are stamped PHE 2.5 and are unpreserved. Store in a cool dark place; refrigeration will enhance their stability.

Phenylephrine exists in a 10% concentration but this carries much higher risk of adverse systemic reactions (without much more mydriasis than 2.5%), therefore it is not recommended. The use of phenylephrine eye drops in routine optometric practice is contra-indicated in patients with: • Known cardiac disorders. • Marked systemic hypertension (>150/90mmHg blood pressure). • Any history of aneurysms or stroke. • Concurrent usage of medications for major cardiac or high blood pressure problems.

Specific precautions (S/P) for the use of phenylephrine 2.5% eye drops in routine optometric practice include their use in patients: • With severe hyperthyroid disorders. • With advanced diabetes. • On any medications that could result in a systemic sympathetic effect. These medications include the indirect-acting sympathomimetics and serotonergics.

A single drop of phenylephrine 2.5% followed five minutes later by a drop of tropicamide 0.5% or 1% should produce at least 3 to 4 mm pupil dilation, even in older patients or patients with very darkly pigmented irides. Two more drops could be instilled if little response has occurred after 15 minutes.

< Use of diagnostic and therapeutic drugs

A patient can be told that their pupil should return to its normal size within six to eight hours; some cycloplegic effect can also be expected.

5.3.6 Drugs to relax the accommodation (cycloplegics)

General properties and use Cycloplegics are needed to obtain a reliable measure of a patient’s (usually a child’s) refractive error where retinoscopy or trial lens procedures are inconsistent, or a patient is unable to co-operate with retinoscopy and/or subjective techniques.

It is essential that the accommodation is relaxed as far as possible (ie less than 2D residual accommodation).

Patients (or the accompanying responsible adults) must be informed that you intend to perform a cycloplegic refraction and given a description of the after-effects, as these may have an impact on what they intend to do after the examination.

Achieving adequate cycloplegia will generally take 30 minutes and this requires special scheduling of patients. More than one eye drop may be required to relax the accommodation and this should be scheduled, to avoid instilling eye drops in quick succession.

The use of a cycloplegic drug is contra-indicated, in routine optometric practice, on all patients for whom the use of a mydriatic is contra-indicated. This is because the cycloplegic drugs will also cause substantial pupil dilation.

A full medication history is essential prior to the use of any mydriatic because a patient may be taking medications that would either contra-indicate the use of a cycloplegic-mydriatic, or could necessitate your giving special attention and additional counselling to the patient.

Cycloplegia can cause some degree of discomfort (photophobia) and decrease in vision, due to glare and substantial change of near point vision. Patients (or the accompanying responsible adults) should be advised of this.

Cyclopentolate as a cycloplegic It is an anticholinergic agent. Cyclopentolate 0.5% or 1% eye drops are available in unit dose for single use only. The containers are stamped CYC 0.5 or 1.0 and are unpreserved. Store at room temperature.

There are no listed medical C/I specific for the use of cyclopentolate eye drops, other than a known allergy.

S/P for the use of cyclopentolate eye drops relate to concurrent use of any medication that could relax the accommodation and dilate the pupil (eg drugs with parasympatholytic actions).

An accepted dose for cycloplegia is that equivalent to a single drop of cyclopentolate 1%, which should sufficiently relax the accommodation.

The magnitude of the effect can be expected to increase by increasing the number of drops; do not overdose.

More than one drop of cyclopentolate should be considered for patients with very darkly pigmented irides. The second and subsequent drops should be instilled at intervals of at least three minutes.

A patient or parent/guardian can be told that some near vision (with appropriate correction if appropriate) should return within four to six hours following the standard dose; the pupil however may stay dilated for 18 to 24 hours.

< Use of diagnostic and therapeutic drugs

6. Key issues: therapeutic drugs

6.1 The place of therapeutic drug use in optometric practice

Some patients may present with mild-to-moderate symptoms and an examination will indicate they are suffering from some form of ocular irritation associated with borderline dry eyes, workplace- or lifestyle-related, environment, seasonal allergies, mild lid margin disease, or bacterial conjunctivitis. Some of these conditions may be considered an emergency on the basis that they will worsen if not promptly treated (Optometrists’ Formulary).

Alternatively, a patient may experience an adverse event during an eye examination for which some form of remedy is applicable. The optometrist is also allowed by law to use, and in very special cases supply, a number of ophthalmic pharmaceuticals for such an event.

It should be assumed that the optometrist using and supplying any therapeutic ophthalmic pharmaceutical accepts responsibility for the well-being of the patient, at least pending referral. 6.2 Therapeutic drugs that can be used by optometrists

Table 10 Therapeutic drugs that can be used by optometrists

• Eyewashes and astringents • Artificial tear products • Ophthalmic lubricants • Topical ocular decongestants • Topical antihistamines • Topical mast cell stabilisers • Topical anti-infectives • Broad spectrum ocular antibiotics

6.2.1 Eyewashes and astringents

General properties and use These are indicated for occasional use by symptomatic patients with seasonal (allergic) conjunctivitis and similar conditions. They are best used with an eyecup, which should be used by a single individual.

They are available as small (20ml) plastic ampoules which contain sterile saline (0.9% NaCl unbuffered) or with ingredients such as witch hazel or plant petal extracts as GSL products or P medicines.

Astringent eye drops are also available as 10ml multi-use bottles containing sterile saline, witch hazel extracts or zinc sulphate 0.25%.

They should not to be confused with large volume (500 or 100ml) bottles of borate-buffered saline marketed as emergency eye wash products (for use when chemicals have accidentally come into contact with the eye).

6.2.2 Lid hygiene products

General properties and use Lid hygiene products are indicated for occasional use by patients with recurrent mild conditions affecting the eyelid margin (blepharitis). They are available as kits with a bottle of surfactants, with lid cleaning pads or as single-use sachets.

Commercial products are designed to replace the use of 1:1 diluted baby shampoo or 3% bicarbonate of soda used as ‘lid scrubs’.

< Use of diagnostic and therapeutic drugs

6.2.3 Artificial tears or contact lens rewetting solutions

Indicated for occasional to moderate use (ie two to six times per day) for patients in need of symptomatic relief (tired, dry eyes etc) after an eye examination, or for patients presenting with mild symptomatology indicative of eye irritation arising from overwork, eye strain, poor environment, borderline dry eye, etc. with or without contact lens wear.

They are available in unit dose containers for single use only as saline or artificial tears (unpreserved) and in a range of 10 or 15ml bottles for multiple use (some containing preservatives). Store all products at room temperature.

S/P relating to the use of artificial tears: check whether a patient has used such products before. When questioned, they would be likely to advise you of any prior adverse reaction that could be due to an allergy to these types of eye drop.

Symptoms may not be constant but more related to the use of systemic medications that could have a direct or indirect effect on the tear film.

Concurrent use of such medications should therefore be considered along with the proposed regimen for use of the eye drops.

Contact lenses, especially soft lenses, should be removed prior to instillation of the artificial tears but can be replaced again within a couple of minutes; specific products labelled as rewetting solutions are designed to be used with contact lenses in situ.

6.2.4 Ocular lubricants

Ocular lubricants are indicated for moderate use for patients presenting with signs and symptoms indicative of a true dry eye condition.

They are available in single dose units (SDUs containing 0.18% sodium hyaluronate) or in filtered bottles for multiple use, or containing hypromellose and preservatives, which can cause toxicity type reaction if used more than four times a day or in susceptible eyes as 10g tubes which contain a viscous ‘eye drop’ (Carbomer polymers) or as smaller (3 to 5g) tubes of unmedicated ointments. Store all products at room temperature.

S/P relating to the use of ocular lubricants: check whether a patient has used such products before. When questioned, they would be likely to advise you of any prior adverse reaction that could be due to an allergy to these types of eye drop.

Viscous eye drops can be used up to six times per day. Gels or ointments can be used as a night-time supplement (applied just before bedtime) to daily use of artificial tears or ocular lubricants or simply used on their own three to four times per day.

An ophthalmic ointment is best applied as a short ribbon along the eyelid margin. Patients should be advised that lubricants, gels or ointments can sometimes be a little uncomfortable on application and temporarily reduce vision.

See the clinical management guide on this dry eye

< Use of diagnostic and therapeutic drugs

6.2.5 Ocular antihistamines

Ocular antihistamines are indicated for occasional to moderate use (two to four times per day) for patients presenting with mild symptoms indicating an ocular irritation, concurrent with low grade signs that should be responsive to the action of an antihistamine-decongestant (conjunctival vasodilation, lacrimation, etc.), and where the history indicates an allergic component (eg hay fever).

They are available in 3ml or 10ml bottles for multiple use and contain a dilute, preservative-included, solution of an antihistamine drug or a combination of an antihistamine drug with an alpha-adrenergic drug.

The use of such eye drops containing antihistamines with alpha-adrenergic drugs is contra-indicated in narrow angle glaucoma.

S/P for the use of the combination eye drops in routine optometric practice include their use in patients with: • Known cardiac disorders. • Marked systemic hypertension (>150/90mmHg blood pressure). • Any history of aneurysm or stroke. • Severe hyperthyroid disorders. • Diabetes. • Concurrent usage of medications for major cardiac or high blood pressure problems. • Concurrent usage of any medications that could result in a systemic sympathetic effect (including the indirect-acting sympathomimetics and serotonergics.

Restrictions on the use in children apply, which may be for those younger than 12 years. Contact lenses, especially soft lenses, should be removed prior to instillation of ocular antihistamine eye drops but can be replaced again within a few minutes.

In recurrent presentations, consideration can be given to the use of sodium cromoglicate 2% eye drops which are available as a P medicine in a 5ml or 10ml bottle. This antihistamine blocks histamine release (rather than blocking a histamine receptor) and needs to be used on a regular basis (eg four times a day) for as long as there is an expected exposure to the allergen(s).

See the clinical management guide on this allergic conjunctivitis

6.2.6 Ophthalmic anti-infectives

Broad spectrum antibiotic (chloramphenicol) A POM This is indicated for short-term use to treat bacterial conjunctivitis or where an eye is considered at definite risk of bacterial infection as a result of an event (fingernail abrasion, etc.) or procedure (eg foreign body removal) that has compromised the integrity of the corneal or conjunctival epithelium. This drug is not for long-term use, or for use where there is a history of recurrent eye infection.

Available as unit dose containers for single use only; the containers are marked CHL 0.5 and should be stored in a refrigerator.

Contra-indications to the use of chloramphenicol would be a known allergy to the drug (or any other ingredient of the pharmaceutical) or development of any other recognised ADR that could be attributed to hypersensitivity (eg a unique toxic reaction associated with aplastic anaemia). Should any local hypersensitivity reaction develop, the eye drops should be promptly discontinued and the patient referred.

< Use of diagnostic and therapeutic drugs

Narrow spectrum antibiotic fusidic acid A POM indicated for the topical treatment of bacterial conjunctivitis where the organism is known to be sensitive to the antibiotic. Available as Fucithalmic 1% w/w Viscous Eye Drops. For all ages: one fusidic acid drop to be instilled into the eye twice daily. Treatment should be continued for at least 48 hours after the eye returns to normal, which should happen within 7 days.

See the clinical management guide on this bacterial conjunctivitis

General purpose anti-infective eye drops Propamidine isetionate is an aromatic diamidine bacteriostatic disinfectant which is active against Gram-positive non-spore forming organisms, but less active against Gram-negative bacteria and spore forming organisms. It also has antifungal properties. It may be used topically for the treatment of minor eye infections such as conjunctivitis and blepharitis.It is available in 10ml bottles with a P classification for multiple use containing a dilute, preservative-included, solution of propamidine.

There are no listed medical contra-indications specific for the use of propamidine eye drops, other than a known allergy.

Since it is specifically useful in the treatment of acanthamoeba keratitis, which is a rare but extremely serious infection that is only managed within the specialist setting, there is less of a place for it in community eyecare. 7. Key issues: contact lens solutions

7.1 General properties

Contact lens solutions should be stable and non-toxic to the eye. Those which are toxic, such as hydrogen peroxide and other cleaners, should never be introduced directly into the eye.

Contact lens solutions should also be inert, comfortable when introduced into the eye and have a suitable tonicity and pH - between 7.2 and 7.6. They should have a reasonable shelf life and opened container life.

The packaging of a contact lens solution should be of a reasonable volume and be clearly labelled with usage instructions and the expiry date. Both the solution and the packaging must be sterile; the nozzle of the container must also be of a design to minimise risk of contamination. 7.2 Soft lens solutions

The main purpose of soft contact lens solutions is to clean and disinfect the lenses so they are safe and comfortable to wear. The solution system selected must be appropriate for the lens type and the replacement frequency of the lenses provided.

Multi-purpose solutions are adequate for frequent replacement lenses. They have both cleaning and antimicrobial actions and are generally preserved with high molecular weight ‘designer’ preservatives, eg Polyquad, Dymed, etc.

Other chemical systems available are based on hydrogen peroxide, chlorine release systems (eg halzone, Aerotab) or chlorhexidine.

Surfactant cleaners, either preserved or non-preserved, are available to use in conjunction with these systems. Students should be familiar with all the care systems they prescribe and know the chemistry behind them. They should also be aware of all commercially available systems, so they can provide appropriate advice to patients.

< Use of diagnostic and therapeutic drugs

7.3 Rigid lens solutions

These cleaning solutions must clean, disinfect and condition the lenses for wear. Rigid contact lens materials are hydrophobic, so the lens must be wetted in order to prevent discomfort when it is inserted. Rigid lenses do not absorb the cleaning solutions as much as soft lenses, so less soaking solution is transferred into the eye. Hence there are far fewer problems with preservative sensitivity in rigid contact lens wearers.

Surfactant cleaners can be used with rigid lenses and some have their action augmented by polymeric beads (eg Bausch & Lomb cleaner).

The wetting and soaking solutions have a disinfecting action and some help to condition the lenses by applying a negative surface charge to aid the lens wettability. 7.4 Protein removing products

Protein removers can be used with both soft and rigid lenses. Most are papain based, but some patients develop a papain sensitivity. Several products are now available without papain, eg Clen-Zym (pancreatin) and Ultrazyme (subtilisin A). Amiclair, which also contains lipase and two proteases, removes lipid, mucin and protein. 7.5 Rewetting drops

A large number of commercial products designated as contact lens rewetting drops are available for use while a contact lens is in place. These should reduce symptoms associated with lens desiccation. 8. Essential reading The Optometrists’ Formulary, (College of Optometrists). Contains details of many ophthalmic pharmaceuticals used in the UK, with specific notes on the types of products that can be used by optometrists.

< Use of diagnostic and therapeutic drugs

Handy Hints Reflective Exercises

• Ensure you have copies of the drug • Record how quickly your patients dilate patient information leaflets for each over your first month in practice. medication you use in practice. Is there a lot of variation?

• Check they are in date and remember • Arrange to speak with your local to record the expiry and batch pharmacist. Discuss which brands of over number on the counter therapeutics are available. Make a note so you know which brands • Register to use BNF online and generics are available to your • Download the College App so you can patients access the formulary and CMGs from • Speak with your supervisor about which your phone. drops they commonly use for dilation • Complete a monthly check of your • Discuss with your fellow optometrists practice therapeutics. What do you the checks they make pre and post stock? Which drugs do you get dilation. Are there differences in through the fastest? practice?

• Prepare a signed order template

• How do you dispose of used medicines and Minims? Review the practice's clinical waste procedures.

Section C

Optical appliances and refractive management

> Visual impairment > Contact lenses > Spectacles and protective eyeware

< Visual impairment

Visual impairment

1. Introduction...... 151 1.1. Definitions...... 151 1.2. Assessment...... 151

2. Core considerations...... 151

3. Core practical topics...... 152

4. Visual impairment competency table...... 152

5. Core revision topics – theory...... 153 5.1 Legal definitions of visual impairment and blindness...... 153 5.2 Registration process...... 153 5.3 Common causes of visual impairment within various age groups...... 153 5.4 Optics of low vision aids and the magnification level attainable...... 153 5.5 Non-optical devices and their availability...... 153

6. Core revision topics – practical...... 154 6.1 Modifications to routine examination to allow for impaired vision...... 154 6.2 Demonstrate how to use a low vision aid...... 154 6.3 Explain the use of specialised test charts...... 154 6.4 Explain the benefits of different types of lighting and glare avoidance...... 154 6.5 Explain eccentric viewing and steady eye strategy techniques...... 154

7. Key issues: visual impairment and its management...... 155 7.1 Legal definitions of visual impairment and blindness...... 155 7.1.1 Sight impairment...... 155 7.2 Registration process...... 155 7.2.1 Registration...... 155 7.2.2 Form CVI...... 155 7.3 Common causes and prevalence of visual impairment within various age groups...... 156 7.3.1 Prevalence by age...... 156 7.3.2 Major causes of severe visual impairment (blindness)...... 156

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7.4 Diagnosed condition – effects on the visual system and tests required...... 157 7.4.1 Corneal pathology...... 157 7.4.2 Cataract...... 158 7.4.3 Age-related macular degeneration...... 159 7.4.4 Diabetic retinopathy...... 160 7.4.5 Glaucoma...... 160 7.4.6 Retinitis pigmentosa and other hereditary retinal disorders...... 161 7.4.7 Optic atrophy...... 162 7.4.8 Hemianopia...... 163 7.5 Impairment, disability and handicap...... 164 8. Key issues: optics of low-vision aids and the magnification level attainable...... 164 8.1 Classification...... 164 8.2 Vergence of light...... 164 8.3 Magnification...... 165 8.4 Determining and prescribing magnification for a near task...... 166 8.4.1 The low vision routine...... 166 8.4.2 Using the charts...... 166 8.4.3 Predicting the required level of magnification...... 167 8.5 Relation between predicted and achieved magnification level...... 167 8.6 Field of view...... 167 8.7 Non optical devices and availability...... 167 8.7.1 Typoscope...... 168 8.7.2 Highlighter pen...... 168 8.7.3 Signature template...... 168 8.7.4 Large print text...... 168 8.7.5 Bookstand...... 168 8.7.6 Talking Book Service (RNIB)...... 168 8.8 Modifications to routine examination appropriate for impaired vision...... 168 8.8.1 Asking the relevant questions in history and symptoms...... 168 8.8.2 Taking appropriate vision measurements...... 169 8.8.3 Using bracketing technique and large increments in power and axis in retinoscopy, and subjective procedures...... 169 8.8.4 Understanding the advantages and difficulties in performing opthalmoscopy at the end of the routine...... 169

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8.9 Demonstrate use of a low-vision aid...... 169 8.9.1 Hand magnifier...... 169 8.9.2 Stand magnifier...... 170 8.9.3 Telescope...... 170 8.9.4 Spectacle-mounted aid...... 170 8.9.5 Video magnifiers and CCTV systems...... 170 8.10 Explain the use of specialised test charts...... 171 8.10.1 logMAR charts: how they are designed...... 171 8.10.2 Amsler chart...... 173 8.10.3 Bailey-Lovie near charts...... 174 8.10.4 Maclure charts...... 174 8.10.5 Keeler A series charts...... 174 8.11 Explain the benefits of different types of lighting...... 175 8.11.1 Daylight...... 175 8.11.2 Artificial light...... 175 8.11.3 Types of lamp...... 175 8.12 Glare avoidance...... 175 8.13 Explain eccentric viewing and steady eye strategy...... 176 8.13.1 Assessing eccentric viewing...... 176 8.13.2 Instructions for eccentric viewing...... 176 8.13.3 Instructions for steady eye strategy...... 176 8.13.4 Emotional support...... 176 8.14 Summary of low-vision routine...... 176

< Visual impairment

1. Introduction

1.1 Definitions

There were thought to be approximately 2.07 million visually impaired people (VIP) in the UK in 2017, when defined as a visual acuity of less than 6/12 (WHO definition of low vision - visual acuity less than 6/18). This is predicted to rise to nearly four million by 2050. If 6/6 and N5 are taken to represent the standards for normal vision, then any level below these can be thought of as visual impairment. There are however many formal definitions of visual impairment. In the UK the statutory definition of blindness, as defined in the 1920 Blind Persons Act and the following National Assistance Act, states that a person is ‘so blind as to be unable to perform work for which eyesight is essential'. Despite logMAR charts being commonplace in a hospital setting the guideline used by ophthalmologists for visual impairment certification is still based on Snellen acuity. Definitions are discussed in more detail later. 1.2 Assessment

At a minimum, practitioners should know how and when to refer VIPs to low vision services or local-authority or third sector sensory service teams. Vision, of course, consists of more than just standards of acuity, and a person can have visual impairment and a high level of central acuity.

Other features of vision that need to be considered during the assessment of the visually impaired patient are binocularity, accommodation, visual fields, colour vision, the ability to distinguish contrast, the effect of illumination and glare, and detection and location of objects. In other words, the assessment of a VIP must include all parts of a general optometric consultation and focus also on visual task analysis (i.e. understanding the patient's visual needs).

A structured visual impairment evaluation has to be designed for each visually impaired patient depending on the cause of their failing sight and their expectations. The patient’s diagnosis should modify your approach, and it will affect their response to a low-vision aid and to training. It is normally not sufficient for an optometrist to supply an optical aid (low-vision aid), since visual rehabilitation of the patient and liaison with other professionals, eg nurses, educators, mobility and rehabilitation officers, are also required. Co-ordination between workers is required in order to give the appropriate level of service at the appropriate time. Some practices may be part of a community based low vision service supporting VIPs in practice. Many visually impaired people do not register with their Local Health Authority even though they are eligible.

Often the ophthalmologist will register a patient only when all active treatment has finished and they are about to be discharged. It is thought many VIPs do not receive adequate help at the most important time. The optometrist can help signpost local services and support groups to anyone affected by sight loss, regardless of whether they are registered or not. 2. Core considerations

• Legal definitions of visual impairment and blindness.

• Registration process - forms LVI and CVI.

• Common causes and prevalence of visual impairment within various age groups.

• Optics of low-vision aids and the magnification level attainable.

• The availability of non-optical devices and services for the visually impaired.

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3. Core practical topics

You should be able to explain the following:

• Modifications to routine examination for impaired vision.

• Use of specialised test charts.

• Use of a low-vision aid.

• The benefits of different types of lighting, management of glare and knowledge of non-optical aids.

• Eccentric viewing and steady eye strategy techniques.

Exercise

Research the difference between registration and certification.

4. Visual impairment competency table

In the College of Optometrists' Scheme for Registration you would be expected to demonstrate the following competencies at Stage 1 visit 2

Professional Conduct 2.2.1 Is able to manage all patients including those who have additional clinical or social needs.

PR Respects and cares for all patients and their carers in a caring, patient, sensitive and appropriate manner. Has knowledge of the Disability and Equality Act (2010) and ensures the patient environment is safe, inviting and user friendly in terms of access and facilities for all patients. Has an awareness of different types of disabilities and patients with additional needs. Understands the criteria and process for RVI/CVI registration, the use of the LVL and the difference between certification and registration. Additional guidance: Able to explain how they have changed their routine to accommodate a particular patient's needs.

7.1.5 Assesses patients with impaired visual function and understands the use of specialist charts for distance and near vision and the effects of lighting, contrast and glare.

Assesses vision and adapts refraction routine depending on circumstances, for example, age, amblyopia, visual impairment. Is realistic in their expectations for the patient. Understands the use and scoring of specialist charts, e.g. Pelli Robson, logMAR to assess vision/VA and contrast sensitivity. Understands the benefits of lighting and the adverse affects of lighting/glare

PR ...... PR ......

< Visual impairment

5. Core revision topics - theory

5.1 Legal definitions of visual impairment and blindness

• Know the criteria used to determine eligibility for registration as visually impaired or blind within the UK. 5.2 Registration process

Demonstrate knowledge of the following:

• Who can refer for registration and who can sign the registration form.

• The CVI 2005 form (Certificate of Vision Impairment), which replaced the BD8.

• Referral letter templates – Referral of Vision Impairment (RVI) and Low Vision Leaflet (LVL).

• Notes to accompany these forms (search for ‘sight loss’ under Policy and Guidance at http//:www.gov.uk). 5.3 Common causes of visual impairment within various age groups

• Be aware of the numbers involved as a percentage of the total visually impaired population.

• Have an understanding of the underlying cause(s) of visual impairment.

• Know how the visual system is affected and the tests required when examining the visually impaired.

• Be able to assess the impairment, disability, or handicap. 5.4 Optics of low vision aids and the magnification level attainable

• Know the classification system for low-vision aids.

• Understand the path of light through the aid to the eye and the lenses used in the structure of the aid, eg the Galilean telescope.

• Know which type of spectacle correction should be used in conjunction with the low-vision aid.

• Be able to calculate the magnification required to read a particular size of print.

• Be able to relate the amount of magnification required to the amount achievable.

• Understand the field-of-view attainable through the various low-vision aids. 5.5 Non-optical devices and their availability

• Know a few examples of non-optical aids.

• Know where these can be bought, hired or borrowed.

• Know some examples of services specifically organised for visual impaired people.

• Understand the benefit of using contrast, sound and touch to supplement the reduced visual input.

< Visual impairment

6. Core revision topics - practical

6.1 Modifications to routine examination to allow for impaired vision

• Ask relevant questions in history and symptoms.

• Take appropriate vision measurements.

• Use bracketing technique and large increments in power and axis in retinoscopy and subjective procedures.

• Understand the advantages of and difficulties in performing ophthalmoscopy at the end of the routine. 6.2 Demonstrate how to use a low-vision aid

• Be able to explain to a patient how to handle the aid to maximum effect.

• Be able to show how to clean and maintain the aid.

• Be able to explain its use in relation to current spectacles. 6.3 Explain the use of specialised test charts

• Know which charts are readily available for distance and near visual assessment.

• Know the uses and benefits of logMAR charts (e.g. Bailey-Lovie).

• Be able to explain their use to the patient.

• Be able to explain how the results of one type of test chart relate to those of another. 6.4 Explain the benefits of different types of lighting and glare avoidance

• Know the available types of auxiliary lighting.

• Explain the advantages and disadvantages of each.

• Explain how a visually impaired person can cope with situations of glare.

• Understand how much lighting is needed for specific tasks and with which pathological/ physiological condition e.g oculocutaneous albinism (less), macular degeneration (more). 6.5 Explain eccentric viewing and steady eye strategy techniques

• Show how to assess the direction of view in order to maximise vision.

• Instruct the patient how, when and why to use eccentric viewing.

• Instruct the patient how, when and why to use steady eye strategy.

< Visual impairment

7. Key issues: visual impairment and its management

7.1 Legal definitions of sight impairment and blindness

7.1.1 Sight impairment

Definition

A patient is ‘substantially and permanently handicapped by defective vision caused by congenital defect or illness or injury.’

Actual guidelines

Generally, to be certified asseverely sight impaired (blind), a person’s sight has to fall into one of the following categories, while wearing any glasses or contact lenses that may be needed:

• Visual acuity of less than 3 / 60 with a full visual field.

• Visual acuity between 3 / 60 and 6 / 60 with a severe reduction of field of vision, such as tunnel vision.

• Visual acuity of 6 / 60 or above but with a very reduced field of vision, especially if a lot of sight is missing in the lower part of the field.

To be certified assight impaired (partially sighted) your sight has to fall into one of the following categories, while wearing any glasses or contact lenses that you may need:

• Visual acuity of 3 / 60 to 6 / 60 with a full field of vision.

• Visual acuity of up to 6 / 24 with a moderate reduction of field of vision or with a central part of vision that is cloudy or blurry.

• Visual acuity of 6 / 18 or even better if a large part of your field of vision, for example a whole half of your vision, is missing or a lot of your peripheral vision is missing 7.2 Registration process

Certification is completed by the consultant ophthalmologist. The patient is either certified as severely sight impaired (blind) or sight impaired (partially sighted). Registration is the process by which the patient is added to their Local Health Authority’s (LHA) register of visually impaired people.

7.2.1 Registration

The aim of the registration process is to enable visually impaired patients to receive help from social services and other benefits, such as free eye tests. Only the senior ophthalmologist to whom the patient is referred may sign the CVI (Certificate of Visual Impairment). Check your local protocols for referring a patient to be considered for registration.

7.2.2 Form CVI

The CVI comprises three parts:

1. To be completed by the patient (or representative). Patient consent for use of their personal information.

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2. To be completed by the consultant ophthalmologist. Patient's details such as: – Name – Date of birth – Address and visual function, including: – Field of vision – Visual acuity – Cause of vision impairment

3. To be completed by eye clinic staff in consultation with the patient. General factors, including: – Whether the patient lives alone – Patient's level of mobility – Any additional disability such as hearing loss

Further information on the CVI can be obtained on the Department of Health Website: www.gov.uk 7.3 Common causes and prevalence of visual impairment within various age groups

7.3.1 Prevalence by age

By far the majority of partially sighted and blind registrations are among people aged at least 75 years. Table 11 shows typical age groups for industrialised countries, where age-related maculopathy, diabetic retinopathy, inherited retinal disorders and congenital anomalies are the main causes of blindness.

The major causes of blindness in developing countries are cataract, trachoma, glaucoma and xerophthalmia.

Table 11 Estimated number of adults living with sight loss by age group (2018)

Working age Total older Older people Older people Older people Area people aged people aged aged 65-74 aged 75-84 aged 85+ 18-64 65+ ENGLAND 343,000 356,000 476,000 562,000 1,394,000

Table 12 Estimated number of people UK living with:

Drusen, an early stage age-related macular degeneration (2018) 2790000 Late stage age-related macular degeneration (2018) 610000 Late stage dry age-related macular degeneration (2018) 432000 Late stage wet age-related macular degeneration (2018) 210000 Cataract (2018) 677000 Glaucoma (2018) 675000 People living with ocular hypertension in people aged 30+ (2018) 1340000 Diabetes (2018) 4190000 Severe diabetic retinopathy (2018) 121000 Background diabetic retinopathy (2018) 1310000

RNIB 2018 Data set

Thus, the main diseases which lead to blindness in developed countries are located in the posterior segment and those in developing countries are diseases of the anterior segment.

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7.3.2 Major causes of severe visual impairment (blindness)

The largest single cause of blindness in England and Wales is degeneration of the macula and posterior pole (114 registrations per 100,000). Glaucoma (12.8 registrations per 100,000), cataract, optic atrophy and diabetic retinopathy are equal third in prevalence (2.9 registrations per 100,000). Although not so common, corneal pathology, retinitis pigmentosa (grouped in hereditary retinal disorders) and hemianopic defects are also discussed in the exam.

The parts of the visual system involved in the disease dictate the visual symptoms and will determine the appropriate help given to the visually impaired person. Therefore, you can consider cataract and corneal pathology as having similar visual characteristics and care options, likewise macular degeneration and diabetic retinopathy, and glaucoma and retinitis pigmentosa as pairs of conditions. However, you must always be ready for a combination of causes, for example a patient with retinitis pigmentosa who subsequently develops cataracts will be in a much worse situation once the second condition has developed. 7.4 Diagnosed condition - effects on the visual system and tests required

7.4.1 Corneal pathology

Prevalence Total 1.4% and increases with age.

Affected region Cornea.

Visual acuity Variable distance and near acuity.

High contrast acuity Severe loss.

Low contrast acuity Reduced, especially at high spatial frequencies.

Visual fields Not affected peripherally, sometimes central distortion.

Colour vision Everything looks greyer so colour vision is depressed, though it remains at ‘normal’ levels.

Binocular vision Usually the pathology is bilateral, so some binocularity may be present.

Other Moderate sensitivity to glare.

Tests to use • High and low contrast letter charts eg, Bailey-Lovie. • Increase illumination when testing at near, and use a typoscope.

Low-vision aids • Increase illumination and magnification. • Use large print. • Use a typoscope (reading slit). • Absorptive (tinted) lenses. • Use colour contrast.

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Training Best use of light and avoidance of glare.

Prognosis Slow progression. Some cases can be treated by corneal grafting. Accurate visual tasks become impossible. Mobility usually remains good.

7.4.2 Cataract

Affected region Lens.

Visual acuity Reduced distance acuity in general, followed by reduced near acuity.

High contrast acuity Mild loss.

Low contrast acuity Marked loss.

Visual fields Not affected, but dimmer picture makes life problematic.

Colour vision Everything looks greyer, so colour vision is depressed, and there is loss of blue sensitivity.

Binocular vision Lost, as one eye often progresses at a faster rate.

Other Moderate discomfort with glare, with marked visual loss

Tests to use • High and low contrast letter charts eg, Bailey-Lovie. • Increase illumination when testing at near, unless opacity is central, and use a typoscope.

Low-vision aids • Increase illumination and reading add or magnification. • Use large print. • Use a typoscope (reading slit). • Use absorptive (tinted) lenses. • Use colour contrast.

Training Best use of light and avoidance of glare.

Prognosis Slow progression. Normally treatable, except in cases where the procedure would be life-threatening. Accurate visual tasks become progressively more difficult. Mobility usually remains good.

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7.4.3 Age-related macular degeneration

Prevalence The prevalence of late AMD in the UK amongst those aged 50 years or more is 2.4%. This increases to 4.8% in people aged 65 years or more, and 12.2% in people aged 80 years or more. The same study found the prevalence of geographic atrophy to be 1.3−6.7%, and the prevalence of neovascular AMD to be 1.2−6.3%. Estimates indicate that around 39,800 people develop neovascular AMD in the UK each year; given a total UK population of 60 million, this equates to 663 new cases per million per year.

Affected region Macular and posterior pole.

Visual acuity NICE 2018 NG82 Reduced central acuity with good peripheral vision.

High contrast acuity Moderate loss.

Low contrast acuity Moderate loss.

Visual fields Central distortion and metamorphosia which can become absolute scotoma. Peripheral fields unaffected.

Colour vision Poor. There may be aurora because of scrambled signals.

Binocular vision Lost, as one eye often progresses at a faster rate.

Other Severe discomfort with glare, with moderate visual loss. When oedema is present, more plus is required subjectively than is found on retinoscopy. 1 mm oedema = 3D hypermetropia.

Tests to use • Increase illumination when testing at near. • Use Amsler chart to find the best area to use for seeing. • Use Bailey-Lovie near charts so the context of print cannot be guessed.

Low-vision aids • Increase magnification and illumination as disease advances. • Use large print. • Use a typoscope (reading slit). • Use absorptive (tinted) lenses.

Training Eccentric viewing. Steady eye strategy.

Prognosis Steadily progressive and untreatable if it is the dry type. Progression is rapid if it is the wet type. The wet type may benefit from laser treatment. Accurate visual tasks become impossible. Mobility is usually good.

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7.4.4 Diabetic retinopathy

Prevalence Total 3.4%, and increases with age.

Affected region Posterior segment. Retina only at first, and vitreous in later stages.

Visual acuity Blurred, and sometimes loss of vision in affected areas.

High contrast acuity Moderate loss.

Low contrast acuity Moderate loss.

Visual fields Patchy loss and distortion of field in affected regions, and mild loss in lasered areas.

Colour vision Early blue defect if macula affected.

Binocular vision Can eventually be lost.

Other Marked discomfort with glare, with marked visual loss if retinal oedema is present.

Tests to use • High and low contrast letter charts, eg Bailey-Lovie. • Use Amsler chart to find the best area to use for seeing. • Use Bailey-Lovie near charts so that context of print cannot be guessed.

Low-vision aids • Increase magnification and illumination as disease advances. • Use large print. • Use a typoscope (reading slit). • Absorptive (tinted) lenses.

Training Consider eccentric viewing. Consider steady eye strategy.

Prognosis Alternating periods of rapid deterioration and stability. Progressive and treatable, the earlier the b et te r. Accurate visual tasks become impossible. Mobility depends on field loss.

7.4.5 Glaucoma

Prevalence Total 8.4%%, and increases with increasing age after 65 years.

Affected region Retina - optic nerve.

Visual acuity Reduced acuity and difficulty in focusing.

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High contrast acuity Good in early stages.

Low contrast acuity Overall reduction.

Visual fields Patchy loss which becomes gross and spares central vision.

Colour vision Early blue vision defect.

Binocular vision Lost as visual field is restricted.

Other Night vision poor in later stages.

Tests to use Full visual field plotting so that mobility can be assessed.

Low-vision aids • Keep magnification as low as possible to utilise remaining field and consider minifying devices. • CCTV with learned scanning skills. • Increase illumination. • Use absorptive (tinted) lenses.

Training Mobility training. Scanning, spotting and tracking.

Prognosis Progressive if untreated; may be unresponsive to treatment. Poor mobility. Performance of visual tasks becomes slower due to restricted visual field.

7.4.6 Retinitis pigmentosa and other hereditary retinal disorders

Prevalence Total 5.5%, and decreases with age.

Affected region Rods in retina.

Visual acuity Good central acuity with poor peripheral vision.

High contrast acuity Good in early stages.

Low contrast acuity Overall reduction.

Visual fields Peripheral ring scotoma which progresses inwards.

Colour vision Early blue vision defect.

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Binocular vision Lost as field constricts.

Other Night vision very poor. Severe discomfort in glare with moderate visual loss.

Tests to use • Full visual field plotting. • Dark adaptation.

Low-vision aids • Keep magnification as low as possible to utilise remaining field. • CCTV with white print on black (reversed contrast). • Use absorptive lenses - brown or red.

Training Mobility training.

Prognosis Slowly progressive and untreatable. Mobility usually poor. Performance of visual tasks becomes slower due to restricted visual field.

Table 13 The Coil Hi Power range of illuminated stand magnifiers. The image is focused at the focal point so the emergent light is parallel and distance spectacles should be worn.

Magnifier Magnification Equivalent Power Emergent Vergence Coil 5226 6X +18.77 -1.00 Coil 5228 8X +28.00 Plano Coil 5210 10X +30.50 Plano Coil 5212 12X +35.90 Plano

7.4.7 Optic atrophy

Prevalence Total 4.2%, and decreases with age.

Affected region Optic nerve head.

Visual acuity Reduced acuity.

High contrast acuity Moderate loss.

Low contrast acuity Moderate loss.

Visual fields Central or peripheral, depending on cause.

Colour vision Normal.

Binocular vision Often strabismus and nystagmus are present.

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Other Nystagmus worsens with fear and excitement, so give patient time to settle down before visual assessment.

Tests to use • Motility test to check speed and amplitude of nystagmus in different directions of gaze. • Bailey-Lovie near charts and Maclure charts.

Low-vision aids Increase magnification.

Training Use the line of sight that gives least eye movement if nystagmus is present. Steady eye strategy.

Prognosis Static and untreatable. Mobility usually good.

7.4.8 Hemianopia

Prevalence One of several conditions that constitute the remaining 9.7% of cases.

Affected region Visual pathway - actual site of lesion needs to be identified.

Visual acuity No acuity on affected side, reading ability affected.

High contrast acuity Complete loss in affected area.

Low contrast acuity Complete loss in affected area.

Visual fields Loss of half the field of vision - can be superior, inferior, nasal or temporal.

Colour vision Normal.

Binocular vision *Lost.

Other Decreased night vision.

Tests to use Peripheral visual fields.

Low-vision aids • Increase illumination. • Use prisms/mirrors.

*Note for hemianopia, when macular vision is affected BV is lost. When macular vision is intact BV is reduced.

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Training Rehabilitation. Learn to turn head and scan.

Prognosis Static and untreatable. Mobility poor. 7.5 Impairment, disability and handicap

The terms impairment, disability and handicap were first described and defined in a World Health Organization document, the ICIDH, the International Classification of Impairment, Disability and Health, in 1980. This has more recently been superseded by the ICF in 2001, the International Classification of Functioning, Disability and Health.

An impairment is the effect on part of the visual system eg, reduced reading vision.

The disability arising from that impairment is the reduction or loss of the patient’s ability to perform a specific task, eg to read or write.

If the patient feels that this is interfering with their daily living, then the disability is defined as a handicap, eg loss of privacy with mail and social reading, loss of employment. 8. Key issues: optics of low-vision aids and the magnification level attainable

8.1 Classification

Low-vision aids can be grouped according to type. The generally accepted types are hand magnifiers, stand magnifiers, spectacle-mounted and head-borne magnifiers, near vision telescopes, distance vision telescopes, and video magnifiers (including CCTV systems). Optometrists should remember high addition reading spectacles can offer a useful alternative to a magnifier, especially in the early days of a progressive disease. 8.2 Vergence of light

It is important to understand the vergence or emergent light coming from a low-vision aid to the eye because it governs the spectacle prescription required when the aid is in use. Optical ray diagrams are typical for each group of aids, but some do not follow these rules eg, Coil Hi Power stand illuminated magnifiers (see table 13).

Table 14 Effect on expected magnification when the separation of eye and magnifier varies, while the object to magnifier distance remains constant. Example is a 6x hand held magnifier, which is a +24D lens, used with the object situated within the focal point of the magnifier.

Separation (cm) 0 5 10 15 20 25 Combined power (D) 2 7.0 23.4 19.8 16.2 12.6 9.0 Magnification (x) 6.75 5.85 4.95 4.05 3.15 2.25

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Table 15 Effects on field of view when magnification is altered, while the lens to eye separation and the lens diameter remain constant.

Lens power (D) Magnification Field-of-view (cm) +10 2.5x 12.0 +14 3.5x 8.6 +20 5x 6.0 +24 6x 5.0

Table 16 Effect of diameter and separation on field-of-view for +24D or 6x magnifying lens.

Diameter (mm) 60 16.7 5.0 2.0 1.7 1.3 50 13.9 4.2 2.1 1.4 1.0 40 11.1 3.3 1.7 1.1 <1.0 Separation (cm) 1.5 5 10 15 20

Figure 26 Coil 6x stand magnifiers, with two differences: a) the right hand one is internally illuminated; b) the emergent light is virtually parallel in the right hand magnifier so the distance prescription should be worn. In contrast, the light diverges in the left hand magnifier so reading spectacles or accommodation, if active, is required.

If the emergent light from a low-vision system is divergent, then either the eye must accommodate or reading spectacles must be worn (Figure 26). If the emergent light is parallel, accommodation will be relaxed and the patient’s distance correction (if appropriate) must be used. 8.3 Magnification

Magnification (M) is a misleading term as manufacturers do not agree on its definition. In theory, magnification is the equivalent power divided by four (M = Fe/4). The British Standard states M = 3Fe/20 + 1.

European manufacturers tend to use M = Fe/4 + 1. This can be termed accommodative magnification, because it arises from the finding that the eye must accommodate 4D in order to see at 25cm.

Alternatively, a +4D lens must be used if accommodation is reduced.

Thus: M = Fe+4 = Fe + 1

4 4

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8.4 Determining and prescribing magnification for a near task

What is magnification?

There are several ways to describe and to calculate magnification. Magnification is merely the comparison of the old object distance to the new object distance. For example, if we cannot see the number plate of a car we move up closer to it. Here the retinal image size will increase by a factor of 2. This is termed relative distance magnification.

Magnification (M) = ______Old object distance New object distance

When establishing near magnification required for a low vision device, by convention we call the old object distance 25 cm. This now sets that standard by which all other distances are compared. For example, if a patient brings the object into a close 5 cm working distance, then the retinal image size is 5 x larger than it was when it had been held at 25 cm:

Magnification (M) =__ 25 = x5 5

In the example above, a +20D lens with a focal length of 5 cm will be needed to focus the image on the retina. By setting the ‘old working distance’ to 25 cm, then magnification can be expressed as,

M = F/4

Thus, a +4D lens with the 25 cm focal length is termed ‘unit magnification’. Each successive addition of another 4 dioptres adds another unit of magnification.

8.4.1 The low vision routine

A well-established, methodical routine gives a good foundation upon which the rest of the consultation is based. 1. Begin by establishing the patient’s baseline near acuity with a +4.00D addition at 25 cm. (25 cm being the focal length of the +4.00D lens). 2. If the level of VA is less than what the patient needs to achieve the desired task, then increase the addition in the trial frame methodically, in either +4.00D or +2.00D steps, until the desired acuity is met. 3. When the desired near visual acuity is met, the magnification of the high reading addition so demonstrated (where M=F/4), will give the practitioner a starting point magnification with which to demonstrate the device of choice, such as a hand magnifier.

8.4.2 Using the charts

There is a direct mathematical relationship between letter size notations on the Times New Roman Faculty of Ophthalmologists reading chart: • N12 is half the size of N24 • N6 is half the size of N12 • N9 is twice the size of N4.5 Therefore it follows that if a patient sees N10 with current spectacles then approximately 2x magnification is required to see N5.

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8.4.3 Predicting the required level of magnification

An alternative method to assess the magnification required for a specific task: • Place a +4.00D addition into a trial frame. • Use a reading chart at 25 cm. • Record the best level of near acuity with the 1x magnification. • Measure the height of a lower case letter (with no ‘limbs’) that the patient wishes to be able to see. • Compare this to standard charts and determine near acuity level. • The magnification required equals best level acuity with 1x magnification divided by required acuity.

Example 1 Best level of near acuity with the 1x magnification is N36. Desired acuity is for print with a lower case letter height of 3.2 mm. This equals N18 or large print book size. Therefore, predicted magnification is N36/N18 = 2x. The last two methods are quick and useful for patients with relatively good distance and near acuities, but for all new patients, a well constructed routine is essential. 8.5 Relation between predicted and achieved magnification level

The relation between the magnification required (predicted) and the amount achievable will depend on whether the emergent light is parallel or divergent.

If the emergent light is parallel and the object is at the focal point of the magnifier, then M=Fe/4.

This rule applies no matter how far from the eye the magnifier is held.

If the emergent light is made divergent by placing the object closer than the focal point, then the eye has to accommodate or reading spectacles must be worn, and this alters the magnification expected.

The magnifier and reading add (or accommodation of the eye) act in concert and may give higher magnification than predicted if the magnifier is close to the eye. There will be lower magnification if the magnifier is relatively far from the eye.

Table 13 demonstrates the alteration in expected magnification as the separation of eye and magnifier varies. 8.6 Field of view

Three factors can alter the field of view when looking through a low-vision aid: the degree of magnification, the diameter of the lens, and the distance between eye and magnifier.

Table 14 shows the field of view for a 60 mm diameter lens held at 5 cm from the eye.

The higher the magnification, the smaller is the field of view.

Table 15 illustrates the effect of changing diameter and intervening distance. The larger the diameter of the lens, the greater is the field of view.

The greater the distance between the eye and magnifier, the smaller is the field of view. 8.7 Non-optical devices and availability

There are some excellent sources of information you should consult, notably the In Touch Handbook which was last published in 1996, and the RNIB publication You and Your Sight - Living with a Sight Problem. Below are a few ideas to get you thinking.

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8.7.1 Typoscope

Any matt black card with an aperture cut in it is called a typoscope. They are easy to make, and are used as ‘windows’ to reduce glare off the paper. They keep the reader on the correct line, and can also be used as a writing guide.

8.7.2 Highlighter pen

These pens are useful for increasing the size and contrast of written words.

8.7.3 Signature template

This is a plastic guide to place over the item to be signed eg, a cheque or pension book. The user can write inside the cut out area.

8.7.4 Large print text

Newspapers, magazines, library books, bills, bank statements, knitting patterns etc. are available in large print versions.

Figure 27 Bookstand. Note the tinted eye shields catalogue on the stand.

8.7.5 Bookstand

They are invaluable in preventing back strain when the working distance is short, or when the person has difficulty holding both the reading material and a low-vision aid. Bookstands are readily obtainable from computer shops and stationers, and are relatively inexpensive.

8.7.6 Talking Book Service (RNIB)

Talking books can be supplied to people with a visual disability. The Talking Book Service provides a wide variety of books that are produced on either non-standardised CDM Rom (DAISY books) or taped cassettes. The RNIB also supplies the specialised equipment on which the books may be played. An annual fee gives unlimited use of the service. 8.8 Modifications to routine examination appropriate for impaired vision

8.8.1 Asking the relevant questions in history and symptoms (Table 16)

The majority of low-vision practitioners would say that this is the most important aspect of the assessment. If the optometrist does not know how the partially sighted patient feels about their situation or what they expect from the visit, then the consultation will be of little value. History and symptoms often take a long time to cover, and this time can be put to good use for patient assessment. The two questions that can be useful are “Which is your better eye?” and “What tasks would you like to do that your poor vision is stopping you from doing at the moment?”

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List the patient’s needs, and work in that order of priority when assessing the aids. If you have a patient who knows his better eye and wants to do everything, then they are resigned to their fate and will co-operate with you - although they may want more than you are able to give them. Never promise miracles - just say that you will do your best.

Table 16 Types of relevant questions

Question Aspects to consider When did your sight deteriorate? Is it congenital, acquired, static, dynamic? Where have you been for help? Have they visited hospital or social services? Who have you seen? Have they seen their optometrist, GP, ophthalmologist, social worker? Why have you come? Have they difficulties with education, work, retirement, daily living? What do you expect? Do they want a general improvement or to be able to do something specific eg, pick a race winner? Which is your better eye? Usually they are starting to work things out for themselves, if they know the answer to this.

8.8.2 Taking appropriate vision measurements

The test chart must be closer than 6m to the low-vision patient. They should be able to see at least three or four lines on the chart. Measure their vision with spectacles, again after retinoscopy, and their final visual acuity. Testing unaided vision is likely to be disheartening to the partially sighted patient.

8.8.3 Using bracketing technique and large increments in power and axis in retinoscopy, and subjective procedures

If visual acuity is less than 6/18, ±0.25D steps are not appreciated by the patient. The lower the level of sight, the larger the increments required in order to elicit a response. You should consider using ±2.00D steps. The same applies to the size of cross-cylinder (±1.00 cross cyl is not unusual). Remember to allow the patient a longer response time and to allow for over-plussing due to the shorter test distance. A 1m test distance generally gives +1.00D more on the distance prescription. If acuity in the two eyes differs by more than two lines, do not attempt binocular aids. Use higher levels of illumination and try higher reading adds than you would for a normally sighted patient.

8.8.4 Understanding the advantages and difficulties in performing ophthalmoscopy at the end of the routine

When ophthalmoscopy will cause disability glare and problems with light adaptation, it is better to leave ophthalmoscopy until the end of the examination. However, this means that you must ask the right questions and rely on receiving good answers from the patient regarding the cause of their loss of sight. 8.9 Demonstrate use of a low-vision aid

8.9.1 Hand magnifier

Place the object at focal point of lens and wear distance spectacles. Explain that by keeping a constant distance between magnifier and object, the separation of eye and magnifier will not affect the level of magnification.

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Figure 28 Coil 6x stand magnifier (left) and 3x hand magnifier (right) with an old fifty pence piece to indicate size. 8.9.2 Stand magnifier

Figure 29 Coil Hi-Power range of illuminated stand magnifiers with a transformer attached to the 12x magnifier. Note the increase in lens diameter and the increase in separation from the working plane from the 12x to the 6x magnifier. Their magnifications are, from left to right, 12x, 10x and 6x respectively.

Place stand on text and move the magnifier over the print. If it has internal illumination, show the patient where the light switch is, and how to change the batteries and bulbs.

8.9.3 Telescope

Figure 30 Eschenbach spectacle mounted 3x Galilean telescope - these are very useful for tasks such as watching television. The focus of the telescope can be adjusted for different viewing distances.

Focus the telescope for the distance being tested and show how altering the focus adjuster changes the clarity of the image.

8.9.4 Spectacle-mounted aid

Figure 31 Eschenbach spectacle-mounted flip clip 4x magnifier or loupe. The working distance is quite close at about 6cm.

Demonstrate precisely where the object should be held. Emphasise the importance of lighting the object.

8.9.5 Video magnifiers and CCTV systems

Ensure the patient understands the controls and what the device can do for them, eg reverse contrast, moving the x-y platform, altering the magnification and even writing under the camera.

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8.10 Explain the use of specialised test charts

Note that the standard N-notation reading charts have levels of acuity which relate to everyday text. Banner headlines = N36 Large print books = N18 Newspaper print = N8

8.10.1 logMAR charts: how they are designed

Table 17 Snellen vs logMAR comparison

Snellen Charts logMAR Image

Letter size Irregular letter size progression. Logarithmic letter size progression. progression Each additional line read is an improvement by This means each additional line read is a different amount of resolution ability. Snellen an equal increase in the detection of the used an imperial size change based around a minimum angle of resolution. 6-meter testing distance. 6/6, 6.12 etc Number of letters This varies on each line, starting with one at The same number of letter on each line, five. on each line the top to seven at the bottom. This makes the chart less easy to memorise This means the chart is easy to memorise and more effective for those with lower and not reliable for those with low vision visual acuity Optotype design 1968 British standard 5x4 Sloan letters 5x5 Letters used Letters of different legibility may be used. Only lines of equal legibility may be used. Some charts use any combination of letters, Only non-serif letters some in serif, some non-serif. (C D K H N Z O R S V) British standard letters This means that each line is equally difficult (D E F H N P R U V Z) to guess This means some lines may be easier to guess than others Letter spacing The letter spacing varies on each line. The spacing of the letters is proportionately The tighter the letters are spaced the equal, and spacing between each row is greater the crowding effect. equal. The chart is less affected by crowding variation, although the first and last letter on each line are subject to less crowding, so may be easier to guess. Scoring No standardised scoring. The fraction may As each line is uniform each letter can be be reported as 6/6-3 or 6/7.5+2, scored at 0.02, each line 0.1. With no consistency between each line, it A reduced ability to read five letters is difficult to use the results in a meaningful anywhere on the chart can be considered a way for understanding disease progression linear drop in vision . Design Type Traditionally internally illuminated and wall Traditionally internally illuminated on a mounted. Now commonly used projected wheeled stand with one chart for the right or on a computerised display with letter eye and one for the left. Now commonly shuffling. used on a computerised display with letter shuffling.

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The chart has the same number of letters per row, a constant size ratio between the lines and between the letters. The letters are all of equal legibility. How to score logMAR Letter by letter scoring is the recommended method. Adding units of 0.02 for each letter requires some arithmetic and when combined with the fact that acuities better than 0.00 (6/6) are negative numbers this can seem counterintuitive. As such initially it is recommended you use a formula; however with practice many practitioners do complete this in their head. logMAR VA score = 1.1 – (0.02 x number of letters read) There are fifty-five letters on the chart up to and including 0.00 line (6/6) so with 0.02 per letter that results in the logMAR result of 0.00. 0.00= 1.1-(0.02x55) If a number of letters over 55 are correctly read a negative score will indicate a visual acuity of better than the 0.00 line, such as -0.10 or -0.20 (6/5 or 6/4). To complete the measurement, you need to record the number of letters correctly read. Score missed letters as incorrect and do not allow second attempts; remember to use a consistent termination rule such as four incorrect answers. Table 18 has three worked examples.

Table 18 Letter by letter logMAR scoring

Chart Information Formula Final Score Correctly read Incorrectly read recorded 31 letters read 1.1 – (0.02 x 31) 0.48

56 letters read 1.1 – (0.02 x 56) -0.02

8 letters read 1.1 – (0.02 x 8) 0.94

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Contrast sensitivity charts Where visual acuity is the measurement of spatial resolution, the smallest gap a person can detect using black letters on a white background, contrast sensitivity is the ability of an eye to detect the threshold between the visible and invisible. Contrast sensitivity provides information about a person’s vision that is in addition to their visual acuity; it is a complementary measurement. Where visual acuity is about the minimum angle of resolution that a person can see, contrast sensitivity is concerned with determining the lightest possible shade of grey that a person can distinguish from white, measured at low spatial frequency sensitivities. The need for such a measure arose around the same time as the Snellen chart in the 1880s, and commercially available charts have been available since the 1920s in the UK. Figure 32 Pelli-Robson contrast sensitivity chart 8.10.2 Amsler chart

Figure 33 Amsler No.2 chart (right) and recording chart (left).

Remember to use extra illumination and the appropriate reading lens. Use the No. 2 chart, which has a diagonal cross and centre spot, and ask the patient to view the centre of the cross. Record whether they report seeing the centre spot. Ask the patient which is the clearest section out of the two triangles at the side, and repeat this for those at the top and bottom. Record the worst areas, and then direct the patient to look towards these so that the best part of the central retina is being used for accurate vision.

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8.10.3 Bailey-Lovie near charts

Figure 34 Bailey-Lovie reading chart - random words are presented on each line.

These are helpful when assessing central defects because the charts consist of words rather than sentences. Therefore, lack of context means the words cannot be guessed. The charts start at N80 rather than N48, which can encourage the visually impaired as they do not feel they are so far different from normal.

8.10.4 Maclure charts

Figure 35 Maclure reading type for children - N18 to N48 grade four level (7-8 year old) is shown.

These children’s graded reading charts are extremely useful for low-vision assessment because of the short words. The Maclure reading chart is often used for patients whose recognition of the written word has declined after suffering a stroke.

8.10.5 Keeler A Series charts

These charts are numbered 1 to 20, where 1 is the smallest and 20 the largest size of print, and each interval represents 1.25x magnification step. The procedure to estimate the magnification required is the same as for other near charts, that is, use a +4.00D lens at 25cm and record the best Keeler A acuity level. Then record the desired size to be read, but calculate the step difference.

Example 2 Best level of near acuity with the 1x magnification is A12 (N24) Desired acuity is for print of size A7 (N8) There are five steps between A12 and A7 @ 1.25x Therefore, predicted magnification is (1.25)5 = 3.05x (approx. 3x)

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8.11 Explain the benefits of different types of lighting

Levels of lighting need to be increased as the eye becomes older, eg a 60-year-old patient will require 3x as much light as a 20-year-old patient to perform the same task. When an eye defect is present, the importance of extra illumination significantly increases. There are some exceptions to this, most notably central cataracts, where increasing the illumination and decreasing the pupil diameter has a detrimental effect on vision. A well-lit environment not only maximises the partially sighted person’s vision but makes the environment safer for them.

8.11.1 Daylight

Daylight is often not fully utilised. Furniture should be positioned correctly to make use of daylight, and curtains fully opened. Daylight can be filtered by thin net curtains, and reflected light will be greater off light-coloured walls. Unwanted reflections from windows and television screens should be avoided. Colour contrast can be used to highlight obstacles, eg use dark chairs on a light carpet.

8.11.2 Artificial light

Electric lighting needs to be bright and even throughout the whole house so that adaptation effects are minimal. Supplementary lighting should be used in task areas such as the reading chair, telephone, eating area, kitchen worktop, bedhead, bathroom mirror and front door. The influence of shadows and glare must be considered when positioning the supplementary lighting.

8.11.3 Types of lamp

• Tungsten. Incandescent filament, widely available. Wide variety of wattage (25-150W). May have a frosted or clear finish but generates excessive heat when used close to the body. • Fluorescent. Available in a wide range of colours and wattage. Colour rendering is improved if the warm type is used. Fluorescent lighting is about five times cheaper to run than filament lamps, lasts about eight times as long, but is more expensive to buy because of the control gear required for fitting. • Halogen. This lighting is very bright, but may cause glare. 8.12 Glare avoidance

Discomfort glare is experienced by everyone, eg watching television in a dimly lit room or using a computer with its screen setting too bright. It is annoying and tiring but does not cause any loss of vision.

Disability glare reduces vision near to the glare source, eg car headlights that are misaligned and dazzle oncoming drivers. Bright sunny days cause visual problems for those suffering from age- related macular degeneration, cataract and retinitis pigmentosa. Among others, significant glare sources are reflections from highly polished surfaces, screens and water. To help the low-vision patient avoid disability glare, you might advise they do the following: • Use blinds or thin net curtains to filter direct sunlight. • Use frosted light bulbs and shades on lamps. • Diffuse rather than reflect light by covering polished surfaces (walls, floors and furniture) with a matt finish. • Position lamps so the bulb is not visible. • Place kitchen lights under wall cupboards. • Wear absorptive (tinted) lenses. • Wear a hat or visor.

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8.13 Explain eccentric viewing and steady eye strategy

8.13.1 Assessing eccentric viewing Use an Amsler chart as described above. Ask the patient to look in the direction which should produce the clearest vision. Sometimes it is easier to try facial recognition first, and then proceed to reading practice.

8.13.2 Instructions for eccentric viewing Once the principle has been appreciated, it is useful to provide written instructions and reading charts to practise. Monitor progress and give frequent encouragement in the early learning stages.

8.13.3 Instructions for steady eye strategy It is often easier to use eccentric viewing with steady eye strategy. This means that the eye remains in a constant direction of gaze whilst the patient moves the printed text. This is the opposite practice to that used in normal reading, but when it is mastered, it can be quicker than using eccentric viewing alone.

8.13.4 Emotional support Acquired sight loss has a significant impact on emotional health. People often go through a period of adjustment to their visual loss. Although a period of depression is to be expected as part of the normal process of bereavement and acceptance on losing sight, it has been shown recently that 43% of adults attending low-vision clinics in the UK had significant depressive symptoms and that of these, 75% were receiving no ongoing treatment. It is useful to ask the following questions: • During the last month, have you felt down, depressed or hopeless? • During the last month, have you felt little interest or pleasure in doing things? • During the last month have you wanted to end your life? If a VIP answers yes, they should be referred for emotional support or counselling. You may wish to give them the details of a helpline to contact. 8.14 Summary of low-vision routine Table 19 Procedures at each visit

Low vision Considerations First visit • base-line refraction • patient requirements • prescribing spectacles • general social factors Assessment of aids • optical devices tried • assess practical barriers to use • electronic devices • accessibility features on devices and home electronics • may or may not dispense • offer information about social care service for non-optical support e.g. rehabilitation officer for visual impairment • provide information about relevant local or national charity for accessing wider support network Dispensing aid(s) • instructions on use - verbal and written • maintenance of aid • demonstration of how to use Follow-up • ensure instructions being followed • reassess achievements • additional requirements Recheck • coping with aid(s) • change in sight • new requirements • any new devices that have come on market

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Handy Hints Reflective Exercises

• Keep an adjustable Anglepoise lamp One and hand magnifier in your consulting • Demonstrate to a person with sight loss room so it is quick and easy to how to best use a magnifying glass demonstrate to patients • Demonstrate to a person how to • Discuss the benefits of accessibility correctly position a light settings on smart phones and tablets • Demonstrate how to use the • Check the electronic chart in your accessibility features on your phone. room and see if it has a logMAR option With their permission contact them a week later. Ask them whether your • Many electronic test charts have a demonstration was useful simulated contrast sensitivity chart function. Check yours to see if you can Two use it in your next low vision Do you know how to refer a person for a assessment Certificate of Visual Impairment in your local area? Find out and write a primer • Keep a list of local patient support for your staff handbook pack. groups to hand Three • Find out if there is a rehabilitation officer for visual impairment (ROVI) in Sit in on a low vision clinic at a local low your locality vision service. What is the most helpful advice support workers give?

Useful Links: Framework for Low vision eye care pathways RNIB Sight loss data tool State of the Nation Eye Health 2017: A Year in Review by RNIB & Specsavers The Royal College of Ophthalmologists has information on certifying people as visually impaired. College of Optometrists Guidance for professional practice: Assessing and managing patients with low vision Further Reading: Low-vision rehabilitation needs of visually impaired people Sensory services: supporting low-vision patients Patient support services: Diabetes UK Guide Dogs International Glaucoma Association Look Macular Society Partially Sighted Society RNIB

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Contact lenses

1. Core theoretical topics...... 180

2. Core practical topics...... 180

3. Contact lens essentials...... 180 3.1. Spectacle prescription...... 180 3.2. History and symptoms...... 181 3.3. Slit-lamp examination ...... 182 3.4. Tear film assessment...... 182 3.5. Keratometry ...... 182 3.6. Contact lenses in situ...... 182 3.7. Examination of eyes post-removal...... 183 3.8. Communication of the trial results to the patient ...... 183 3.9. Instructions of lens insertion and removal...... 183

4. Contact lens design and materials...... 185 4.1. Material...... 185 4.2. Geometry...... 186

5. Complications of contact lens wear...... 186 5.1. Superficial punctate epitheliopathy (SPE)...... 186 5.2. Superior arcuate staining (SEALS)...... 187 5.3. Inferior arcuate staining (smile staining)...... 187 5.4. Corneal infiltrates...... 187 5.5. Acute corneal oedema...... 187 5.6. Corneal microcysts (chronic corneal oedema)...... 188 5.7. Mechanical/foreign body staining...... 188 5.8. Three and nine o’clock staining...... 188 5.9. Dimple veiling/air bubbles under the lens...... 189 5.10. Limbal hyperaemia...... 189 5.11. Red eye reaction...... 189 5.12. Bulbar conjunctival staining...... 190 5.13. Dry eye symptoms...... 190 5.14. Giant papillary conjunctivitis (GPC)...... 190 5.15. Contact lens associated red eye (CLARE)...... 190

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5.16. Superior limbic keratitis (SLK)...... 191 5.17. Contact lens peripheral ulcer (CLPU)...... 191 5.18. Microbial keratitis...... 192 5.19. Deposits...... 192 6. Laws and regulations relating to contact lenses and care products...... 193 6.1. Opticians Act of 1989...... 193 6.2. Amendment of Opticians Act (2005)...... 193 6.2.1. Fitting of contact lenses...... 193 6.2.2. Supply of contact lenses...... 194

7. Tips for the practical assessments...... 194 7.1. Assessment of soft lenses...... 194 7.2. Assessment of rigid lens fit...... 195 7.3. Slit lamp use in relation to contact lens practice...... 195 7.4. Specifications for a contact lens order...... 196 7.4.1. Rigid lenses...... 196 7.4.2. Soft lenses...... 196

8. Scenario based questions...... 196

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1. Core theoretical topics

• Indications and contra-indications to contact lens wear

• Lens selection

• Patient advice and instructions

• Complications of contact lens wear

• Lens modifications 2. Core practical topics

• Pre-fitting assessment

• Lens insertion and removal

• Assessment of lens fit

• Slit lamp usage

• Aftercare 3. Contact lens essentials

3.1 Spectacle prescription

A valid endorsed spectacle prescription, where the eye test has been performed no more than 2 years prior to the initial contact lens fit assessment.

The prescription allows for the: a) assessment of visual acuity with habitual prescription. b) selection of the initial contact lens power.

If the spectacle prescription in any one meridian is above 4.00D use the back vertex distance formula or a BVD calculator.

CL Rx = F/1-dF, where:

F - spectacle lens power in dioptres d - back vertex distance in metres

Astigmatism - consider asking yourself the following questions: a) Does the spectacle astigmatism correspond to the corneal astigmatism? b) If not, how much residual astigmatism would there be with soft and rigid lenses?

The amount of residual astigmatism acceptable with contact lens wear is dependent on several factors:

Spherical Rx - low myopes are less tolerant of uncorrected astigmatism.

Axis of astigmatism - uncorrected against-the-rule astigmatism is more problematic than with-the- rule. Oblique axis is more problematic than with-the-rule.

Since there are lots of toric lenses for astigmatism available on the market, it is best to offer the patient the options, with clear explanation of the difference, so that they can make an informed choice

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A rough guide is provided below for lens choice:

≥0.75DC RGP / Spherical soft 1.00-3.00DC RGP / Toric soft >3.00DC (corneal) Toric RGP / Toric soft >1.00DC (internal) Toric soft

Spherical refraction: For hyperopes and moderate to high myopes, ensure that the lens design supplies adequate oxygen. If presbyopic consider the effect of contact lenses on accommodation - myopes will find accommodation harder with contact lenses; hyperopes will find it easier. 3.2 History and symptoms

Crucial for a good contact lens fit. a) Determine the patient’s motivation for contact lens wear Generally using an open question to the patient about motivation for lens wear is important. Reasons might be e.g. cosmetic, sports, therapeutic, medical, abnormal corneal topography, anisometropia, high Rx, b) Has the patient worn contact lenses previously? If so gain complete detail on lens type and the reason for discontinuation. c) Ocular history: a) Ask about: red/sore eyes/dryness/diplopia/headaches/pain and follow-up questions as appropriate. b) Any Hospital Eye Service (HES) visits c) Any infections d) Previous trauma or surgery. d) General health: a) Any general health conditions e.g. diabetes, under-active or over-active thyroid, rheumatoid arthritis or anything else? b) Do you smoke at all? c) Asthma, allergies or eczema? e) Medication: name, dose, use? f) Occupation: complete visual task analysis g) Hobbies.

A complete history and symptoms assessment is important to rule out any contraindications the patient may have to contact lens wear.

• Visual e.g. low Rx, Lens availability, prisms.

• Occupational e.g. where legal constraints apply.

• Medical e.g. allergies, diabetic corneal changes, thyroid disease.

• Dryness - poor tear volume or quality of tears, poor blinking, dry environment.

• Environment e.g. dust, fumes, altitude.

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3.3 Slit-lamp examination

A complete slit-lamp examination is required to:

• Confirm the norm of ocular tissues.

• Discover any conditions that would prevent contact lens wear.

• Record for the future any other abnormalities.

• Observe skin conditions - brow and hair conditions, lumps and bumps.

• Check the eyelids and eyelashes - lid eversion for initial fit assessment is vital.

• Check the position of the palpebral aperture and eyelid tension.

• Irregularities e.g. styes, blepharitis, MGD.

• Check the cornea and limbus - including fluorescein assessment 3.4 Tear film assessment

This can be performed with slit-lamp examination but other techniques can also be used, e.g. keratometer, keratograph tearscope, Schirmer's strip.

Tear examination will help determine type of lens to use for initial fit and success of CL wear. 3.5 Keratometry

Soft lenses: BOZR - 0.60 -1.0mm flatter than the average keratometry curvature (limited use in soft lens parameters, but base-line data important for comparative purposes with time). Some manufacturers provide guidelines.

RGP lenses: a) Select BOZR to match the flattest K (for astigmatism generally up to 1.50DC). b) Some guidelines say 1/3 steeper than flattest K (for astigmatism up to 2.00DC) - for an alignment fit. c) Astigmatism >2.00DC Flattest and steepest meridian selection on K’s.

Examples of lens selection will be highlighted in scenario questions. 3.6 Contact lenses in situ

Select and check lenses in situ

Ask about the comfort and vision

Consider sending patient outside for a walk or real world experience; of course this is dependent on lens type e.g. RGP, multifocal, monovision, toric lenses.

Bring patient back and seek feedback: • ‘Are the lenses comfortable?’ • ‘How was the vision?’ • ‘Did you like being able to see without specs?’ • ‘Anything you struggled with?’

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3.7 Examination of eyes post-removal

• Take lenses out

• Look for any adverse effects on the eye.

• Instil fluorescein = must record

• Increase illumination and vary magnification.

• Use additional Wratten filter #12 which is yellow if you can as this maximises view of fluorescence (positioning the yellow barrier filter in the path of the returning light and not in the path of the incident light)

• Grade any changes

• Evert the eyelids; must record appearance of tarsal conjunctiva 3.8 Communication of the trial results to the patient

Decide with the patient which lenses to order, ensuring the patient is aware of the price.

Explain the rest of the process to the patient.

Make the next appointment if necessary,

Record clearly which lenses are to be ordered. Order the lenses. 3.9 Instructions of lens insertion and removal

Ensure you demonstrate to the patient how to insert and remove contact lenses

Observe the patient perform insertion and removal at least twice independently before they take the lenses.

Ensure the patient understands the following:

• Importance of washing and drying hands.

• Importance of no swimming with certain contact lens types.

• No tap water should be used in contact with lenses

• Importance of lens case hygiene.

• Importance of case replacement.

• How to use the solution provided.

• Importance of no sleep/ nap with lenses (dependent on lens type but applies to the vast majority you will deal with).

• Importance of lens removal in case of: allergies, red eyes, discomfort, irritation, cold and seasonal changes.

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Appropriate care systems:

Clearly, any of a range of care systems can be recommended to patients, but give thought to your own chosen systems, particularly with respect to:

• Reasons for selecting the system(s) - advantages.

• Active constituents and their functions.

• Limitations of your chosen system, such as adverse reaction rate, antimicrobial efficacy, convenience.

• Special precautionary advice to patients, such as advising rub and rinse on removal with multipurpose systems.

• Signs and symptoms of solution intolerance with your system(s). In the case of most multipurpose systems, this usually involves symmetrical, bilateral, widespread superficial punctate keratitis. There may also be some mild limbal hyperaemia and symptoms of burning and stinging, although often asymptomatic.

Wearing times

Take into account previous history, tolerance shown during fitting etc. but as a guide:

RGPs: Start with 4-6 hours increasing 2-4 hours per day. Soft lenses: Start with 6-8 hours increasing 4 hours per day.

Replacement schedule (soft lenses)

Determine whether unplanned, three-monthly, monthly, bi-weekly, weekly or daily, taking into account the following:

• Previous experience with respect to spoilation and breakage rates.

• Full/part-time usage - daily disposable use may be more practical for part-time wearers.

• Cost implications.

• Previous contact lens wearing experience, eg papillary conjunctivitis or other deposit-related problems.

• Patient preference.

Special precautions

• Cosmetics - advise insertion of lenses before application of make-up and removal of lenses before removal of make-up. Take care to avoid using old contaminated eye make-up. Take care to avoid transfer of skin moisturisers to lens surface (affects wettability and can irritate cornea).

• Monovision - allow 3 weeks for full adaptation. Take care to avoid driving especially at night during adaptation period and subsequently if vision is disrupted.

• Disinfection - for part-time soft contact lens wearers.

• Extended wear - advise removal of lenses if symptoms appear. Give out-of-hours telephone number.

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4. Contact lens design and materials

4.1 Material

A) Rigid lenses

Fluorosilicone acrylate RGP materials tend to be more wettable and less susceptible to protein deposition than silicone acrylate materials.

Higher DK RGP means increased deposition, more susceptible to scratches, thicker lenses and lower modulus, therefore, poorer correction of astigmatism.

Although PMMA might still be used to manufacture rigid lens trial sets, they have little place in modern contact lens practice because of their inadequate oxygen permeability (Dk effectively zero).

B) Soft lenses

PolyHEMA is: • Durable • Relatively deposit resistant • But provides inadequate oxygen permeability for most patients.

PolyHEMA lenses are unsuitable for both plus and moderate to high minus prescriptions.

High water content materials are often subdivided into ionic and non-ionic materials.

Ionic materials (eg etafilcon, methafilcon) tend to: • Attract protein • Be pH sensitive • Show significant dehydration

Non-ionic materials (eg Nelfilcon A and Omafilcon A) tend to: • Have the highest water contents (>60%) • Attract lipids • Shrink on the eye due to temperature sensitivity

Materials such as omafilcon do not fit precisely into either category.

C) Silicone hydrogel lenses (eg narafilcon, comfilcon, balafilcon, lotrafilcon)

Materials with: • Low water content (24 - 35%) • High oxygen permeability (Dk>100) • Stiffer than conventional hydrogel materials

Because these materials are inherently hydrophobic, they incorporate surface treatments to render them wettable.

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4.2 Geometry

A) RGP lenses

The most common rigid design used in this country is a tricurve back surface design. Bicurve designs are occasionally used with smaller designs (<8.40mm) while tetracurve designs are sometimes used with larger designs (>9.50mm).

Aspheric designs are often used with branded, stock designs (eg Quantum, Conflex) as opposed to custom designs. The perceived advantages of aspheric designs are: • Thinness • Comfort due to smooth back surface • Aspheric optics (but this also gives induced astigmatism on decentration).

B) Soft lenses

The geometry of soft lens designs tends to be set by the manufacturer, often with little or no range of choice for a given design. Therefore, if one particular design does not provide a satisfactory fit, it is often necessary to resort to an alternative design. 5. Complications of contact lens wear

These are outlined in rough order of prevalence. 5.1 Superficial punctate epitheliopathy (SPE)

A generalised non-specific staining or punctate disruption of the corneal epithelium. Seen in 35% of non-contact lens patients. Staining in contact lens wearers may result from a variety of causes including:

• Mechanical effects

• Exposure (disruption of the tear film)

• Hypoxia

• Allergic/toxic reactions

• Overwear

• Deposits

• Systemic disease

Symptoms: Symptoms are not always present but depend on severity. In rigid lens wearers, diagnosis must differentiate from dimple staining caused by air bubbles.

Management Depends on cause and severity: • Remove lens for the rest of the day. • New lenses, if deposited. • Change to lens with higher oxygen transmission if other signs of oedema are present. • Change to thicker or more dehydration-resistant lens if cause is desiccation. • Reduce wearing time.

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5.2 Superior arcuate staining (SEALS)

Confluent area of staining approximately 1mm from superior limbus, associated with soft contact lens we a r.

Due to mechanical pressure from a relatively thick or inflexible or steep soft lens. Diagnosis must differentiate SEALS from superior limbic keratitis. Symptoms of lens awareness after several hours of wear and sometimes on lens removal.

Management One of the following: • Replace with new lens of same type (if lens is old or deposited). • Refit with thinner, more flexible (high water) lens. • Refit with flatter lens. • Refit with lower modulus lens 5.3 Inferior arcuate staining (smile staining)

Localised disruption of the epithelial surface as a result of desiccation, especially with thin, high water soft lenses. Tear film is poor, or may be associated with incomplete blinking. Patients may experience symptoms of grittiness late in the wearing period leading to reduced wear time.

Management: • Change to thicker or more dehydration resistant lens, if due to desiccation. • Lens lubricants 5.4 Corneal infiltrates.

Accumulation of inflammatory cells, seen as a single or multiple white spots in the corneal epithelium or stroma. Produced by reaction to viral infection, chemical toxicity, denaturation, cellular debris or an allergic response to solution preservative.

Tip: Ensure it does not stain with fluorescein

Management • Cease lens wear until infiltrates resolve and remove the cause - e.g. change care system. 5.5 Acute corneal oedema

Increased hydration of corneal stroma due to hypoxia. Visible as corneal haze by indirect slit lamp. Most prevalent with PMMA and low water content soft lenses.

Signs • Corneal haze (visible by indirect illumination). • Corneal (stroma) striae. • Endothelial folds.

Note: Differentiate from Fuchs'/corneal disease

Symptoms May include: • Possibly none. • Burning sensation. • Photophobia. • Spectacle blur.

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Management • Reduce wearing time. • Cease extended wear. • Change to a lens with higher oxygen transmission. 5.6 Corneal microcysts (chronic corneal oedema)

Small, translucent irregular dots distributed in an annulus in the corneal mid-periphery. Associated with soft lenses, especially extended wear. Primarily the result of chronic corneal hypoxia. Microcyst numbers may fluctuate during lens wear, and may temporarily increase following cessation of lens wear. Patient may complain of minor irritation.

Management • Change to a lens of higher oxygen transmission. • If the result of extended wear, reduce the number of nights or change to daily wear. 5.7 Mechanical/foreign body staining

Epithelial linear disruption caused by a foreign body under the lens or mechanical damage because of a damaged lens, clumsy insertion, etc. more common with hard or RGP lenses. Pain is relieved by removing foreign body or damaged lens.

Management • Refit with soft lenses. • Optimise edge clearance. • Treat tear deficiency. • Encourage lateral eye movements and improve blink efficiency. 5.8 Three and nine o’clock staining

Disruption of the epithelial surface in the 3 and 9 o'clock positions, caused by incomplete blinking (and hence localised drying) and/ or tear film breakdown in RGP wear. Chronic condition which can progress to scarring and vascularisation of the cornea,

Causes: • Bad or thick edge design. • Edge clearance too large or too small. • Total diameter minimal or excessive. • Incomplete/ insufficient blinking.

Management: • Refit with soft lenses. • Optimise edge clearance. • Treat tear deficiency • Encourage lateral eye movements and improve blink efficiency.

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5.9 Dimple veiling/air bubbles under the lens.

Indentations of the epithelium caused by pressure of trapped air bubbles under a rigid lens. May occur in all lenses but more prevalent in steep lenses, poor fitting hard lenses, and following sub-aqua diving. Patients may experience mild lens irritation. Diagnosis must differentiate this from true corneal staining.

Management • Modify lens fit and in severe cases cease lens wear until staining resolves. 5.10 Limbal hyperaemia

Engorged limbal vessels are associated with hypoxia. Common in most soft lens wearers and to some extent in all lens types. Diagnosis must differentiate from corneal infection.

Causes • Poor lens fit. • Hypoxia. • Allergic reactions. • Toxic solution reactions.

Management

Depending on cause and severity: • Cease lens wear until condition resolves. • Remove stimulus. • Reduce wearing time. • Improve peripheral oxygenation - high oxygen transmission soft lens or RGP lens. 5.11 Red eye reaction

Injection of conjunctival blood vessels in association with acute anterior eye reaction. If bilateral, may be either a toxic or a hypersensitivity reaction. Consider corneal condition if unilateral. Common in extended wear. Diagnosis must differentiate from conjunctivitis, keratitis, uveitis and angle-closure glaucoma.

Causes • Solution reaction/allergy. • Oedema/hypoxia. • Dry eye. • Environmental. • Poor health due to influenza, throat infection, substance abuse, etc.

Symptoms • Discomfort. • Burning/itching. • Increased contact lens intolerance.

Management • Identify cause. • Cease lens wear then refit. • Change from extended wear to daily wear.

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5.12 Bulbar conjunctival staining

Common in contact lens wearers (50% >Grade 1 ) and present with dry eye conditions, poor blinking and due to mechanical trauma of the lens periphery on the conjunctiva. When associated with dry eye, itchiness and contact lens intolerance may be experienced.

Management • Change lens design. • Change lens fit. • Blinking exercises 5.13 Dry eye symptoms

Dry eye symptoms result from poor tear quality which leads to increased lens spoilation. May be due to reduced aqueous, meibomian gland dysfunction or a reduction in the lipid layer.

Management • Replace old lenses. • Use preservative-free contact lens rewetting drops. • Change lens material to dehydration-resistant material. • Reduce wearing time. • Consider mini scleral lenses. 5.14 Giant papillary conjunctivitis (GPC)

Also known as contact lens-associated papillary conjunctivitis (CLAPC). An allergic reaction of the superior conjunctival tarsal plate and is characterised by papillae >1mm diameter. The papillae are collections of lymphocytes and plasma cells. Main causes are wear of old and deposited lenses and solution allergy. Itching (especially on lens removal), lens awareness and excess.

Management • Replace old lenses. • Encourage regular enzymatic cleaning. • Refit with daily disposable lenses or RGP lenses. • Reduce wearing time. 5.15 Contact lens associated red eye (CLARE)

Sudden overnight onset of unilateral redness with symptoms of pain and discomfort associated with overnight use of lenses. Diagnosis must differentiate from conjunctivitis, keratitis, uveitis and ACG.

Causes • Overnight contact lens wear. • Bacterial toxins.

Symptoms • Discomfort. • Burning/itching. • Increased contact lens intolerance.

Signs • Faint infiltrates without significant staining. • Infiltrates usually peripheral to mid-peripheral. • Moderate to severe limbal and bulbar hyperaemia.

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Management • Cease lens wear. • Replace all lenses. • Change from extended to daily wear. 5.16 Superior limbic keratitis (SLK)

Superior limbic inflammation of the cornea. Occurs with soft lenses and is sometimes a response to hypoxia, an allergic response or reaction to thiomersal.

Note: can be linked to significant blepharitis and meibomian gland dysfunction.

Signs • Superficial punctate keratitis. • Subepithelial infiltrates. • Infiltrates. • Unilateral or bilateral presentation. • Pannus may develop to involve the whole cornea.

Symptoms • Stinging or burning on lens insertion.

Management • Change solution. • Increase lens oxygen transmission. • Reduce wearing times. 5.17 Contact lens peripheral ulcer (CLPU)

An ulcer is defined as a full thickness break in the epithelium and, in the cornea, is accompanied by an underlying infiltrate. Ulcers may be sterile or infected. Diagnosis must differentiate from microbial keratitis and infiltrative keratitis.

Symptoms • None, or • Pain. • Foreign body sensation. • Redness. • Tearing.

Signs • Small (<2mm) focal infiltrate in periphery or midperiphery. • Moderate limbal and bulbar hyperaemia especially in region of infiltrate.

Causes • Uncertain but probably mechanical trauma plus bacterial antigens e.g. blepharitis/ MGD

Management • Although probably sterile, treat as if microbial keratitis, ie cease lens wear immediately and refer immediately.

Prognosis • Full recovery leaving scar for at least 6 months.

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5.18 Microbial keratitis

Presents as an epithelial break penetrating into the stroma surrounded by oedema and infiltrates. In contrast to a sterile ulcer there is usually lid oedema, severe conjunctival redness and an anterior chamber reaction. With an amoebal infection there may be a ring infiltrate. Diagnosis must differentiate from infiltrates caused by bacterial, viral, fungal or amoebal infection of disrupted epithelium

Predisposing factors • Trauma. • Pre-existing ocular surface disease (eg dry eye). • Use of contaminated care products. • Diabetes. • Smoking. • Contact lens wear.

Symptoms • Acute, moderate to severe pain. • Foreign body sensation. • Red eye. • Puffy eyelids. • Tearing. • Photophobia. • Reduced vision if on visual axis.

Management • Cease lens wear immediately. • Prompt medical treatment - topical antibiotic and often hospitalisation. • Future lens wear only with caution and restricted. • Replace all lenses, cases and lens care products before resuming lens wear.

Prognosis • Peripheral - full recovery leaving scar. • Central - possible visual disturbance depending on scar position. 5.19 Deposits

A) Protein

Sheets of denatured protein show up as an uneven haze on the lens surface. Very common with high water, ionic lenses (Group IV). Patient may complain of itchiness and increased lens awareness.

Management Any of the following, as appropriate: • New lenses. • Change lens material. • Increase replacement frequency. • Change care product. • Use protein removal tablets.

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B) Lipid Top Tips: More common with high water, non-ionic lenses (Group II). Symptoms may include decreased When presented with complications of comfort and vision. contact lens wear at an aftercare, for management consider the following: Management Any of the following, as appropriate: 1. Intervention • New lenses. • Change the lens • Change lens material. • Change the cleaning regimen • Increase replacement frequency. • Therapeutic or referral • Increase surfactant cleaning. 2. Modification C) Fungal growth • Alter the wearing time • Review current habits and routines Fungus growing in the lens matrix often occurs • Advise accordingly with intermittent wear and poor hygiene. 3. Combination of points 1. and 2. D) Make-up

This may cause increased contact lens intolerance, reduced vision and dry eye symptoms. 6. Laws and regulations relating to contact lenses and care products.

6.1 Opticians Act of 1989

Under the GOC rules of 1988, any newly qualified optometrist is entitled to fit lenses. Dispensing opticians are required to take a supplementary examination. Optometrists who qualified before 1960 may not fit contact lenses without further certification. Licensing of contact lens solutions became obligatory in January 1980. From June 1998, within the EC, only CE marked contact lenses may be supplied. There are two exceptions to this:

1. Lenses supplied to a prescription from a qualified practitioner, and

2. Lenses to be used as part of a clinical trial.

The Opticians Act of 1989 was amended in 2005. The current laws and regulations relating to contact lenses and care products are as discussed below. 6.2 Amendment to Opticians Act (2005)

6.2.1 Fitting of contact lenses

Only an OMP, optometrist or contact lens optician can fit contact lenses. The fitter must, on completion of the fitting, provide the patient with a signed written specification. This must include an expiry date. A contact lens can only be fitted if,

• The practitioner has a signed, written prescription from a sight test conducted within a 2-year period.

• The fitting process begins before any re-examination date that has been specified in the prescription.

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6.2.2. Supply of contact lenses

Any person can sell a contact lens to an adult provided they have a valid specification and satisfy specified conditions. The conditions are as follows: • The seller must have the original specification. • If they do not have the original, they must have a copy, which they then verify with the person who provided it. • The seller must have an order, which contains the specification, which is verified with the person who provided the specification. • The sale must be made before the expiry date. • The seller is under the general direction of an OMP, OO or CLO. • The seller must make arrangements for aftercare. 7. Tips for the practical assessments

Information for pre-registration students who are undertaking assessment at stage one of the Scheme for Registration (this is periodically reviewed by the College and may change between visits).

Visit 1: Ability to perform keratometry, insert and remove lenses and discuss RGP and soft lens teaches.

Visit 2: RGP fitting, RGP and soft lens aftercare and complications.

Visit 3: Soft lens fitting.

Stage 2: Soft lens fit and aftercare practical assessment. 7.1 Assessment of soft lenses

Do not merely describe the fit as ‘tight’ or ‘loose’ and can only be assessed with sufficient magnification provided by a slit-lamp. Assess each aspect of lens performance, as follows:

• Comfort Well-fitting soft lenses are usually comfortable enough to be indiscernible. Therefore, suspect the fit of any lens that the patient is able to feel. Tip: ask patient to rate ‘how the lenses feel on eye’ out of 5.

• Corneal coverage The lens should show full corneal coverage in all directions of gaze and show overlap of the visible cornea by at least half a millimeter.

• Centration Some decentration is acceptable but be prepared to comment on this.

• Movement The lens should show some movement on blink and version. Assess tightness/looseness by the ‘push-up’ moving the lens upwards by placing a finger or thumb on the lower lid and gently moving upwards. If necessary, ask the patient to look slightly upward. A well-fitting lens will show free movement on push-up and prompt return. A tight lens will be difficult to dislodge and slow to return. A loose lens will move very freely and tend to drop quickly when the lid is moved downwards.

• Edge fit By slit lamp examination, ensure the lens does not show edge stand-off or scleral indentation (less common).

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7.2 Assessment of rigid lens fit

Do not rely on a Burton lamp other than to make a cursory evaluation. Use white light as well as blue light. Assess each aspect of the lens fit, not merely whether it is steep or flat, as follows:

• Comfort With a new wearer some discomfort is to be expected; however the patient’s response can be helpful - eg irritation of both top and bottom lid could indicate lowriding fit or large diameter.

• Centration Assess with white light using normal head position. Is there lid attachment? Is the fit intra-palpebral?

• Movement Does the lens move excessively on blink and version? Will the movement affect vision? If movement is excessive, might it be due to excessive lacrimation? How quickly does the lens centre?

• Central fit Ensure correct fluorescein concentration. Excessive fluorescein will give the appearance of steep fit; low concentration due to tearing may give a false impression of aligned fit. Assess with fluorescein and blue light with the lens centred on the cornea - if necessary manipulate the lens into the central position using the lids.

• Peripheral fit Assess with the patient looking to the side, or manipulate the lens to a three or nine o’clock position. Ensure by peripheral fluorescein pattern that edge clearance is neither too large nor too small. Be prepared to say how you would modify the specification or the existing lens to achieve satisfactory fit. Be able to justify your assessment of fit with reference to basic rigid lens optical principles. 7.3 Slit-lamp use in relation to contact lens practice

Gain enough practice to be as confident using a slit lamp as you are an ophthalmoscope.

• Devise a routine that ensures you undertake a comprehensive examination without inadvertently missing anything.

• Familiarise yourself with the controls prior to using the instrument, in particular: the slit width, illumination and filter controls and the decoupling mechanism.

• Use two hands to control the slit lamp - one for the joystick, one for the illumination system so that both can be constantly adjusted.

• For lens examination, use low magnification and a broad beam, but take care not to dazzle the patient.

If you are not familiar with using the slit lamp for examining contact lens fit, PRACTISE.

The following methods of illumination are relevant to contact lens practice:

• Indirect illumination - corneal oedema (corneal haze), corneal infiltrates, microcysts.

• Direct illumination - stromal striae, endothelial folds.

• Retro-illumination - vascularisation, corneal opacities.

• Specular reflection - corneal endothelium.

• Sclerotic-scatter - central corneal oedema from PMMA lens wear.

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7.4 Specifications for a contact lens order

You should know generic international standards, especially for the lenses you prescribe in practice.

7.4.1 Rigid lenses

Be prepared to write a full RGP specification, eg: C3: 7.80;7.80/ 8.60;8.60/ 10.50;9.20 BVP -3.00D

Remember that a full specification could include the following: • Material • Tint • Blending • Engraving • Centre thickness • Front optic zone diameter

7.4.2 Soft lenses

For most lenses this involves: BOZR / total diameter / BVP.

For frequent replacement lenses, specify also the quantity and replacement period. 8. Scenario based questions

Question 1:

A 20year old female is interested in contact lenses. She is starting her first office based job.

a) What clinical tests would you need to perform to determine your first choice lens?

b) If her prescription is as follows: RE: -2.00 DS LE: -2.00/-1.50x170

Discuss what lens type you would use as initial fit (hint: think about material, modality, spherical or toric, RGP or SOFT)

Answer:

a) Complete history & symptoms assessment. • Full slit-lamp examination of the anterior eye with fluorescein assessment. • HVID and VPA assessment. • Keratometry - baseline measure.

b) For students to consider Question 2:

A 36 year old male has the following prescription. Order your first choice RGP lens.

RE -2.25/-3.00 x10 LE -2.75/-4.00 x175

Manual keratometry readings are: RE 7.94@6/7.29@96 LE 7.91@176/ 7.13@86

HVID = 11.0mm

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Answer:

For any toric RGP consider each meridian

Diameter: We have the HVID of 11mm - order at least 2mm less therefore 9.0mm

Always refer to the manufacturers' guide for lens diameter availability.

Lens powers: RE -2.25D at 10degrees and -5.25D at 100degrees Steepest meridian power: -5.00D (BVD calculated 12mm) Flattest meridian power: -2.25D

LE: -2.75D at 175 degrees and -6.75D at 85 degrees

Steepest meridian power: -6.25D Flattest meridian power: -2.75D

Base curves: RE: keratometry reading as follows - 7.94@6/ 7.29@96

Consider ordering 1/3 steeper or on K’s for each meridian

So: Steepest meridian: 7.30mm Flattest meridian: 7.95mm

LE: keratometry reading as follows - 7.91@176/7.13@86

So: Steepest meridian: 7.15mm Flattest meridian: 7.90mm Question 3:

Mrs Smith wears monthly contact lenses (Proclear lenses), general wear time is 12 hrs/ day for 7/7 days. She explains her eyes go extremely red towards the end of the day and are uncomfortable. a) What clinical investigations would you like to perform for appropriate management? b) What other lens options does Mrs Smith have?

(Are there any further questions you would ask the patient? Is there any other information you would need to consider about the lenses prior to management?)

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Question 4:

A 28 year old female presents for a contact lens aftercare complaining her vision is not as good with her contact lenses. Read the record card provided and discuss your management plan for this patient.

RE LE H&S Finding her vision esp for near worse Finding her vision esp for near worse with lens wear. LE > RE feels worse with lens wear. LE > RE feels worse

Comfort rated 2/5 Comfort rated 2/5

Mild redness end of day, OK with lens Mild redness end of day, OK with lens removal and rest of eyes. removal and rest of eyes.

WT 5x/week from 7:00am to 6:00pm. WT 5x/week from 7:00am to 6:00pm.

No discharge. No pain. mild FBS with No discharge. No pain. mild FBS with lenses lenses No other problems reported. No other problems reported.

Wears monthly lenses Wears monthly lenses Uses Synergi solution. Uses Synergi solution. Distance VA 6/6 6/6 Near VA N5 N5 Fit characteristics Centration central 1.5mm N/T/S/I Centration central 1.5mm N/T/S/I

MOB: 0.50mm MOB: 0.50mm

Lag - 25% Lag - 25% Sag - 50% Sag - 50%

Push-up - quick accurate recovery Push-up - quick accurate recovery

Toric marking @ 5 o’clock moves Toric marking @ 5 o’clock moves anticlockwise on blink 10 degrees clockwise on blink 10 degrees Brand name PROCLEAR toric lenses PROCLEAR toric lenses Rx -1.75/-3.25 x 90 -1.00/-2.75 x 100 Ocular examination Healthy No corneal staining Healthy; no corneal staining

Mild hyperaemia grd 1 bulbar and Mild hyperaemia grd 1 bulbar and palpebral conjunctiva palpebral conjunctiva

No other problems noted No other problems noted

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Question 5:

A 46 year old female RGP wearer presents for an aftercare appointment. Read the record card provided and discuss your management plan.

RE LE H&S Px has noticed over the last 2 months Px has noticed over the last 2 months she has reduced the amount of hrs she she has reduced the amount of hrs she wears her CLs wears her CLs WT 8:00am to 3:00pm- takes out at WT 8:00am to 3:00pm- takes out at work as experiences soreness, FBS, work as experiences soreness, FBS, irritation with lenses — gradually irritation with lenses — gradually worse. worse. RE>LEaffected RE> LE affected CL wearer for 15 years RGP only. CL wearer for 15 years RGP only. No pain, No discharge, no other No pain, No discharge, no other problems reported problems reported GH: Good. GH: Good. No allergies. No smoker. No other No allergies. No smoker. No other problems. No meds taken problems. No meds taken Occupation: warehouse operative Occupation: warehouse operative Distance VA 6/7.5 6/6 Near VA N5 N5 Fit characteristics Centration — slightly inferior Centration — central MOB: 1.5 - 2.0 mm MOB: 1.5 - 2.0 mm Lag - 50% Lag - 50% Brand name BOSTON XO material BOSTON XO material Rx -5.00/-0.75x180 -4.50DS Ocular examination Cornea — 3 and 9 o’clock staining Healthy; No corneal staining Mild hyperaemia grd 1 bulbar and Mild hyperaemia grd 1 bulbar and palpebral conjunctiva palpebral conjunctiva No other problems noted No other problems noted

Handy Hints Reflective Exercises

• Make sure you learn as much as possible from hands • Do you discuss and on experience with contact lenses, especially in terms routinely offer contact of learning insertion and removal techniques. lenses to your patients attending for a sight • Get to know the fitting sets available to you in test? practice in terms of material, power range, base curve diameter and handling. • How many adverts for contact lenses do you • Make your own list of top tips from any optometrists see online, in magazines, and contact lens fitters you know who may well be fancy dress shops and able to give you some helpful light-bulb moments. on social media? • Practise explaining how to care for lenses: the dos • What are the risks and don'ts. Either do this with a friend who can associated with the provide their own critique of what and how you public accessing contact performed or video record yourself, play it back and lenses from the above reflect on what you have said. sources?

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Spectacles and protective eyeware

1. Core theoretical topics...... 203

2. Core practical topics...... 203

3. Key issues: practical tips for dispensing...... 203 3.1 Order writing...... 203 3.2 Occupational dispensing...... 204 3.3 Dispensing for children...... 204 3.4 Lens thickness...... 204 3.5 Differential vertical prism...... 204

4. Key issues: lens materials...... 205 4.1 Crown glass...... 205 4.2 High index glass...... 205 4.3 Toughened glass...... 205 4.4 CR39 (ophthalmic hard resin)...... 206 4.5 Polycarbonate...... 206 4.6 High Index plastic...... 206 4.7 Summary...... 206

5. Key issues: lens powers...... 207 5.1 Terminology...... 207 5.2 British standard tolerances...... 208 5.3 Back vertex distance...... 209 5.4 Voucher values...... 209 5.5 Ophthalmic prisms...... 210 5.6 Prismatic effects of lenses...... 210 5.7 Relative prismatic effect...... 210

6. Key issues: aberrations and lens forms...... 210 6.1 General aberrations...... 210 6.2 Chromatic aberration...... 211 6.3 Distortion...... 211

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6.4 Oblique astigmatism...... 211 6.5 General lens forms...... 211 6.6 Best lens form...... 212 6.7 Aspherics...... 212 6.8 Lenticulars...... 213

7. Key issues: lens coatings and tints...... 213 7.1 UV filters...... 213 7.2 Anti-reflection coatings...... 214 7.3 Hard coats...... 215 7.4 Tint description...... 215 7.5 Fixed solid tints...... 215 7.6 Fixed vacuum-coated tints...... 215 7.7 Fixed dipped tints...... 216 7.8 Photochromic description...... 216 7.9 Glass photochromics...... 217 7.10 Plastic photochromics...... 217

8. Key issues: multifocal lenses...... 217 8.1 General information...... 217 8.2 Solid bifocals...... 217 8.3 Fused bifocals...... 218 8.4 Verification of bifocals...... 218 8.5 Segment dimensions...... 218 8.6 Jump...... 219 8.7 Differential vertical prism...... 219 8.8 Trifocals...... 219 8.9 Varifocals or progressive addition lenses...... 220 8.10 Varifocal designs...... 220 8.11 Varifocal markings...... 220 8.12 Varifocal fitting...... 220 8.13 Varifocal verification...... 221

9. Key issues: glazing...... 221 9.1 Definitions...... 221 9.2 The glazing process...... 221

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10. Key issues: frames...... 222 10.1 Frame materials: general information...... 222 10.2 Plastic materials...... 222 10.3 Metal materials...... 223 10.4 Frame markings...... 223 10.5 Frame description...... 223 10.6 Frame measurement...... 223 10.7 Blank size calculation...... 223

11. Key issues: eye protection...... 224 11.1 Responsibility for provision of eye protection...... 224 11.2 British/European standards...... 224 11.3 Ocular and housing markings...... 224 11.4 Ocular and housing materials...... 226 11.5 Properties of eye protectors...... 226 11.6 Filters...... 226 11.7 HSE guidelines...... 226 11.8 Reglazing old appliances...... 226

12. Acknowledgment...... 228

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1. Core theoretical topics

• Lens materials

• Lens powers

• Aberrations and lens forms

• Lens coatings

• Multifocals

• Frames

• Problem solving 2. Core practical topics

• Determination of lens specification

• Determination of refractive index and surface powers

• Frame measurements

• Facial measurements

• Frame adjustments

• Determination of prescription

• Verification of lens specification 3. Key issues: practical tips for dispensing

3.1 Order writing

Orders should be written according to BS2738 part 3 (2004). Most of this is common sense but, in outline, is as follows:

• Give lens powers to two decimal places, with + or - sign as appropriate. Give back vertex distance (BVD) for sphere powers >5.00DS.

• Do not use a degree sign for the cyl axis, as this can be confused with a zero.

• Right eye is designated ‘R’, and information for this eye should be given first. Left eye is designated ‘L’, and information common to both eyes is designated ‘BE’.

• Horizontal centration or monocular centrations should be stated. If vertical centrations are not given, they are assumed to lie on the horizontal centre line (HCL). Locations of seg top position (STP) and geometric inset (GI) should also be given where relevant.

• An order is complete only when it includes the name and address of the patient, the name, address and signature of the prescriber and the date.

• All information must be legible

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3.2 Occupational dispensing

You should be able to prescribe spectacles for occupational use. You might consider the following examples and discuss with your supervisor:

Example 1

A cricketer may need UV protection and impact resistance in his spectacles. He may also want a pair of photochromic lenses. His prescription is -6.00DS R & L. What are the options?

Example 2

A presbyopic office administrator who does a great deal of VDU work wants spectacles with a wide intermediate field of view, but needs to read print at near as well. What are the options? 3.3 Dispensing for children

There are several important factors specific to dispensing for a child. These include:

• Lens material - impact resistance is important. Plastic should be favoured over glass, and polycarbonate may be preferable over both, although its resistance to abrasion is poor.

• Lens form - since children’s lenses are usually small, lens forms such as aspherics are usually unnecessary; however specifying minimum edge thickness blanks can help achieve better cosmesis of plus powered prescriptions.

• Frame material - The frame material must be robust and its allergenic properties may also be considered.

• Frame style - where possible, the size of the frame should be appropriate to the interpupillary distance (PD) to avoid decentration of the lenses. Round frame shapes will give even edge thicknesses or the possibility of knife-edge lenses in high plus prescriptions. Back vertex distance (BVD) should be considered where necessary. Curl or loop sides may be useful to secure frames on very small children. 3.4 Lens thickness

Edge thickness varies in prescriptions with high cyls. The thickest meridian is along the positive axis. For these patients, consider frame shapes that minimise edge thickness differences. For high prescriptions, choose small, regular shapes. Upswept or exaggerated angular shapes mean extra edge thickness and decentration in high negative prescriptions. If possible, the PD should be comparable to the distance between centres (see Key issues: frame measurements 10.6) to avoid this. 3.5 Differential vertical prism

You should first check for anisometropia in the vertical meridian, which would lead to differential vertical prismatic effects. The anisometropia might be spherical or a difference in power along the 180 axis only.

If anisometropia is present, calculate the differential vertical prism using Sasieni’s Rule (see differential vertical prism in section 8.7).

Consider the dispensing solutions for differential vertical prism:

• Bi-prism bifocals (or slab-off bifocals) Base down prism is removed from the lower half of the more negative lens, giving a base up effect. This method used on D-segs and executives gives the best cosmetic effect.

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Example 3

R -3.00DS L +1.00DS Add +2.25

Assuming the NVP is 10mm below the distance optical centre (OC) (Sasieni’s Rule) the vertical differential prism is 4∆ base down, right eye. Therefore, work 4∆ base up on the right eye by slabbing off.

• Drop the distance OCs by 5mm to ‘split the difference’ and reduce the prismatic effect.

Less common alternatives include using • Franklin split. This is not ideal mechanically, but gives complete control of centration in both lens portions. • Prism-controlled solid bifocals. These are round seg, solid bifocals with prism worked onto the seg only (up to 4∆). Unlikely to be generally avialable as discontinued for some time. • Different seg diameters (prism x 2 = difference in seg diameters x add). 4. Key issues: lens materials

4.1 Crown glass

Manufacture - molten glass (1000-1500˚C) is cut into a gob with shears into a cast iron mould. The lens is cooled at 360˚C per hour to avoid stress. The final lens is ground by generating (rough cutting) and lapping (finer abrasion of required radius of curvature).

Advantages - refractive index is higher than that of CR39 (n =1.523) so lenses are thinner; lenses are abrasion resistant; they have good constringence (V value 58) and transmission (92% in uncoated state).

Disadvantages - poor impact resistance and shatters into sharp shards when broken; density quite high so lenses will generally be heavier than CR39. 4.2 High index glass

Manufacture - modifiers (eg lead oxide or titanium oxide) are included in the molten glass mix to increase refractive index.

Advantages - lenses are thinner than crown and hence usually lighter, but remember that high index glasses achieve a greater n with an increase in density.

Disadvantages - the modifiers increase density and dispersion, and can make the lens softer and less durable than crown. Higher refractive index lenses have greater surface reflectance and therefore need anti-reflection (AR) coats to improve transmission (see section 7.2). 4.3 Toughened glass

Manufacture - thermally toughened lenses are made by heating fully finished and edged glass lenses to 650-700˚C and then cooling them rapidly. Chemically toughened lenses are immersed in potassium nitrate for 16 hours at 460˚C.

Characteristics - thermally toughened lenses give a cross strain pattern on a polariser and are thicker than standard glass lenses. There is no simple way to distinguish chemically toughened from standard glass.

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4.4 CR39 (ophthalmic hard resin)

Poly-digol bisallyl carbonate, or CR39, is a thermosetting plastic.

Manufacture - liquid monomer with hardener and UV absorber, in optically polished toughened glass moulds, is polymerised by heating to 40-80˚C for 24 hours. Alternatively, a semi-finished lens is moulded and the second surface ground as for glass (see above).

Advantages - CR39 has a low density and lenses are therefore lighter than crown. Transmission is good (92% in uncoated state), and constringence (V value 59) is excellent. Impact resistance is better than crown and the lens does not splinter when broken. UV protection is good (about 350nm) since UV absorbers are incorporated into the lens as standard.

Disadvantages - since it has a lower refractive index (n=1.498) than crown glass, CR39 lenses are thicker than crown glass lenses. Abrasion resistance is poor, unless a hard coat is applied. 4.5 Polycarbonate

Manufacture - lenses of bisphenol A polycarbonate, an ophthalmic thermoplastic, are made by injection moulding.

Advantages - primarily impact resistance or ‘increased robustness’ (BS EN 166 1996), making it ideal for sports and industrial purposes. It is also becoming more popular for children’s and general- purpose spectacles. Polycarbonate also has good UV protection (UV cut-off 400nm), a higher refractive index than CR39 (n=1.586) and is very light.

Disadvantages - abrasion resistance is very poor, so polycarbonate lenses are coated with silicone- based polymers. This reduces the impact resistance slightly, but the material still maintains its ‘increased robustness’ standard. Polycarbonate cannot easily be tinted. 4.6 High index plastic

Advantages - as with high index glass, increasing the refractive index of a plastic lens provides thinner, lighter lenses, with the same advantages as CR39, ie good transmission and constringence, better impact resistance than crown and no risk of splintering.

Disadvantages - high refractive index plastics with n values of 1.6 or more tend to be more rigid and brittle and less impact resistant than CR39. 4.7 Summary

You should know the following facts about every lens you regularly dispense: • Refractive index • Impact resistance • Weight (density or specific gravity) • Abrasion resistance • V value • UV absorption in untinted state • Minimum thickness (particularly centre thickness for negative lenses) • Base curves/lens form • Rx range • Blank sizes • Thickness and weight relative to CR39 • Alternatives

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Some figures are given in Table 20. Note that the values given for higher index materials are for a variety of brands; you should find out the specific values for the lenses you dispense.

Table 20 Properties of various lens materials, shown in ascending order of nd

Specific UV cutoff Material Class n n V gravity d e d (nm) (gcm-3) CR39 plastic 1.498 1.500 59 1.3 350 Crown glass 1.523 1.525 58 2.5 300 Trivex plastic/thermoplastic 1.532 1.534 43-45 1.1 395 Mid index plastic 1.557 1.561 37-47 1.2 370 Polycarbonate thermoplastic 1.586 1.589 30 1.2 385 Mid index plastic 1.595 1.602 36-42 1.3 380 Mid index glass 1.600 1.604 42 2.6 330 High index plastic 1.665 1.670 32 1.3 395 High index glass 1.701 1.706 42 3.2 330 High index plastic 1.710 1.715 36 1.4 380 Very high index plastic 1.740 1.745 33 1.4 395 Very high index glass 1.802 1.807 35 3.6 350 Very high index glass 1.885 1.893 31 4.0 340

5. Key issues: lens powers

5.1 Terminology

For a full list of terms, see BS EN ISO 13666 (2012). Common terms that will be used throughout these notes include:

• Front surface power (FSP): n-1 F 1 = ––– r1

• Back surface power (BSP): 1-n F 2 = ––– r2 where n is the refractive index and r is the radius of curvature of the surface.

• Back vertex power (BVP) = F’ v. For a thin lens:

F'v = F1 + F2 For a thick lens:

F1 F 'v = F 2 + –––––––– 1 - t F1 (( n ) where t is the centre thickness of the lens (metres).

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• OC = optical centre of the lens.

You will be expected to transpose easily between positive sphero-cyl, negative sphero-cyl and cross-cyl forms of prescription writing. 5.2 British standard tolerances

The tolerance for both meridians is determined by the power of the most powerful meridian.

Example 4

What are the acceptable tolerances on a prescription of +5.00DS / +6.00DC x 180?

Power of the most powerful meridian = +11.00D.

From the tables below: first meridian +5.00DS:±0.18D second meridian +11.00DS: ±0.18D cylinder +6.00DC: ±0.25D axis: ±2o

Measure the difference in vertex powers on the lens surface containing the segment, i.e. back surface for most solids, front surface for fused and progressives.

In Tables 21–24, tolerances are given for any lens other than progressives (BS EN ISO 21987-2017). Tolerances on progressives are only very slightly greater than those quoted here.

Table 21 Tolerances for main lens

Highest Tolerance of Tolerance of cyl 1.00-4.00 4.25-6.00 6.25+ absolute power each meridian 0.25-0.75 0-3.00 ±0.12 ±0.09 ±0.12 ±0.18 ±0.25 3.25-6.00 ±0.12 ±0.12 ±0.12 ±0.18 ±0.25 6.25-9.00 ±0.12 ±0.12 ±0.18 ±0.18 ±0.25 9.25-12.00 ±0.18 ±0.12 ±0.18 ±0.25 ±0.25 12.25-20.00 ±0.25 ±0.18 ±0.25 ±0.25 ±0.25 20.25+ ±0.37 ±0.25 ±0.25 ±0.25 ±0.37

All values in D

If you can’t remember all the values, at least have some idea of the scale of tolerances (ie 0.12-0.18D, rather than 0.50-0.75D!) and the fact that tolerance is measured according to the highest power meridian.

Table 22 Tolerances for add Table 23 Tolerances for cyl axes

Power of highest Tolerance (D) Cyl power Tolerance absolute meridian ±4.00D ±0.12 0.50DC ±7˚ >±4.00D ±0.18 0.75 ±5˚ 1.00-1.50 ±3˚ >1.50DC ±2˚

Measure the difference in vertex powers on the lens surface containing the segment, i.e. usually front surface for plastic bifocals (feel where the segment dividing line is located) and progressive lenses.

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Table 24 Tolerances for prism

Power (b) Tolerance of base Power (b) Tolerance of prism setting (deg) power (b) 3.00 ±5 2.00 ±0.12 3.25-6.00 ±2.5 2.25-10.00 ±0.25 >6.00 ±1.5 >10.00 ±0.50

5.3 Back vertex distance

Back vertex distance (BVD) is defined as the distance from the visual point of the spectacle lens to the corneal apex or the closed eyelid (BS EN ISO 13666 (2012)). If the trial frame and the final frame chosen have different BVDs, an adjustment should be made for this, particularly when using powers greater than ±5D (BS2738 part 3 2004). In practice, stating the BVDs of the trial frame and the frame on the order should be sufficient.

To calculate the compensation required for a vertex distance change, compensate for each meridian separately in cross-cyl form, rather than the sphere and the cylinder.

Power alteration = F2/1000 per mm of alteration. As negative lenses get closer to the eye, minus power decreases. As positive lenses get closer to the eye, plus power increases. As a tip to remember this, think of how you change the lens power when moving from a spectacle Rx to a contact lens Rx. 5.4 Voucher values

NHS voucher bands are defined in Tables 25 and 26. Make sure you know the current values of the commonly used bands.

Voucher supplements include complex appliances, prism, clinically necessary tint, small frame and repairs. Hospital prescriptions may qualify for photochromic or special facial supplements. You should know the qualifying criteria for all these supplements.

Table 25 Voucher categories for single vision lenses (values correct for April 2021. Ensure you check the current voucher values yearly)

Sphere 0.25-2.00 2.25-6.00 Over 6 Plano-6.00 A £39.10 6.25-9.75 B £59.30 10.00-14.00 C £86.90 Over 14 D £196.00

Table 26 Voucher categories for bifocal lenses (values correct for April 2018. Ensure you check the current voucher values yearly)

Sphere 0.25-2.00 2.25-6.00 Over 6 Plano-6.00 E £67.50 6.25-9.75 F £85.60 10.00-14.00 G £111.20 Over 14 H £215.50

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5.5 Ophthalmic prisms

Prisms are lenses that deviate light rather than change its vergence. Light is deviated towards the base (thick end) of a prism, the thinner end of a prism being its apex.

Orientation of a prism is defined by the base direction, ie up, down, in or out, or specified as an angular orientation on a 0-360˚ scale. Prisms can be identified by the variation in lens thickness, by their displacement of an image, and in that the optical centre of a lens will not coincide with the lens reference point (eg PD centration, boxed centre). 5.6 Prismatic effects of lenses

Focal lenses have prismatic effects on light passing through any point on the lens other than the optical centre, as given by Prentice’s Rule:

P(∆) = cF

where decentration, c, is in cm.

Positive lenses give prism with base in the same direction as decentration, whereas negative lenses give prism with base in the opposite direction to decentration.

Alternatively, remember the sign convention that, both for prism base direction and decentration of the OC from the viewing point, ‘down’ and ‘out’ are ‘positive’. Cylinders must be decentred perpendicular to their axes to give maximum prismatic effect, eg +2.00DC x 180 will give prismatic effect if decentred vertically, but not if decentred horizontally. 5.7 Relative prismatic effect

When calculating prismatic effects for a pair of eyes, remember the same base is additive for horizontal prisms, whereas the opposite base is additive for vertical prisms and the appropriate eye must be specified.

Example 5

Divide 4∆ base In, 6∆ base up right eye between the two eyes.

Prism should generally be divided equally between the eyes, therefore: R 2∆ base in, 3∆ base up; L 2∆ base in, 3∆ base down 6. Key issues: aberrations and lens forms

6.1 General aberrations

An aberration is an optical defect in a lens that results in the image-forming rays failing to refocus sharply or failing to focus in the desired position (BS EN ISO 13666 (2012)). Spectacle lens aberrations can be described as axial (spherical, chromatic) or oblique (transverse chromatic, coma, distortion, curvature, oblique astigmatism), according to whether the aberrated light rays are incident on the lens close to the optical axis (paraxial) or far from it (oblique). The more important aberrations for spectacle lenses are described below.

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6.2 Chromatic aberration

Chromatic aberration (CA) is caused by a lens having different refractive powers for different wavelengths of incident light. A phrase you may find helps you remember that a lens refracts short wavelengths more than long is: ‘blue bends best’.

Axial CA (D) = F/V Transverse CA (∆) = yF/V where y is decentration and V is the Abbé value representing constringence, or 1/dispersion.

• The higher the lens power, the greater is the CA. • The more peripheral the point on the lens, the greater is the CA. • The smaller the V value, the greater is the CA.

The eye itself causes CA (hence the duochrome works!) and so CA in spectacle lenses is not as great a problem as it might be. In extreme cases, CA produces coloured fringes around objects, primarily towards the edge of the lens. CA is more likely to be noticed by the patient as blur through the lens periphery. The amount of CA is primarily dependent on lens material, and higher index materials tend to have smaller V values (and hence greater CA). 6.3 Distortion

A distorted image is one with a different shape to the object. A highly positive lens produces pincushion distortion (a square object appears drawn out at the corners) because magnification increases with increasing distance from the optical axis. A highly negative lens produces barrel distortion (the sides of a square object appear convex) because magnification decreases away from the optical axis. 6.4 Oblique astigmatism

If a ray of light from a point object hits a spherical refracting surface at an oblique angle, an elliptical image forms with separate tangential (major axis) and sagittal (minor axis) line foci instead of a single image point. The difference between tangential and sagittal oblique vertex sphere powers is the oblique astigmatic error. The amount of oblique astigmatism is primarily dependent on lens form (see below). 6.5 General lens forms

• Curved lens - this has one surface convex in all meridians and one surface concave in all meridians, eg meniscus lens.

• Flat lens - any lens that does not fulfil the criteria for a curved lens. It does not necessarily have a flat surface, eg bi-convex, plano-concave lens.

• Toric lens - has one toroidal surface (may be tyre, barrel or capstan form), which has two non- identical finite radii of curvature in perpendicular sections. The base curve has lowest surface power (longest radius of curvature) and the cross curve has highest surface power. The other lens surface is spherical.

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6.6 Best lens form

Figure 36 Tscherning’s ellipse

Figure 36 shows Tscherning’s ellipse, which for a specific refractive index gives the spherical lens forms that reduce oblique astigmatism to zero.

• The form of the ellipse varies with n, and with fixation distance.

• There are two solutions of FSP for each BVP, and the shallower solution is more acceptable cosmetically.

• The positive prescription limit is around +7.00D, whatever the value of n. Above +7.00D, other means, eg aspheric surfaces, must be used to reduce peripheral lens aberrations. In practice, standard base curves are used to get ‘near to best form’. These are generally flatter than expected on the basis of Tscherning’s ellipse to make them cosmetically acceptable, and as a compromise between distance and near forms.

• Using high index lenses extends the range of negative best form lenses available. 6.7 Aspherics

An aspheric surface is generated by revolution of a symmetrical but non-circular curve about its axis of symmetry. At the lens vertex the surface has a radius of curvature (r0) which is indistinguishable from that of a sphere, and is used to calculate paraxial power.

Asphericity is given by the value p. For a spherical surface, p=1. For an aspheric surface in a highly positive lens, p is generally between 0 and 1 (ellipsoid form), so that the surface profile becomes progressively flatter at increasing distances from the vertex. For low power lenses, p<0.

Aspheric lenses are usually moulded in plastic. They are often combined with high index material to reduce thickness and weight and give an optically acceptable flatter lens form. Aspherics are available in full aperture, lenticular and bifocal forms.

By flattening the lens in the periphery, aspherics reduce oblique astigmatism, especially in high plus lenses where Tscherning’s ellipse cannot provide a best form lens. Aspherics are also used for better cosmesis and for reduced oblique astigmatism in larger blanks for low to medium prescriptions.

You can identify an aspheric lens by measuring surface power with a lens measure. The value will not be constant across the surface of an aspheric lens.

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When fitting aspherics take care with monocular PDs and vertical centration. Since the lens power changes away from the OCs, it is vital that the patient looks through the OC of the lens. With the eye in primary position, lower the OC 1mm from the pupil centre for every 2˚ of pantoscopic angle. 7.8 Lenticulars

A lenticular is a lens in which only the central portion of the lens, the aperture, contains the prescription. The surrounding portion or margin is plano or low power and acts merely as a carrier. Lenticulars are used to reduce the weight and thickness of high power lenses, and to allow high power lenses to be glazed into a wider range of larger frame sizes. Lenses are moulded in plastic.

Lenticulars have a smaller field of view than full aperture lenses. In convex lenticulars, a ring shaped scotoma is caused by the sudden prismatic effects at the edge of the optical zone. This creates a ‘jack in the box’ effect, in which objects can disconcertingly appear and disappear out of the scotoma. Field of view can be improved by blending the edge between the optical zone and the carrier, although substantial astigmatism is created in the blending zone. An alternative design is the Welsh Drop type, which consists of an optical zone with a series of concentric flatter spherical curves (Figure 37).

The edge thickness of a negative lenticular lens is less and the cosmetic effect is better than a full aperture lens, giving a wider frame choice.

Figure 37 A solid convex lenticular, B: Welsh Drop lenticular, C: blended plano margin concave lenticular.

7. Key issues: lens coatings and tints

7.1 UV filters

Ultra-violet (UV) light is of shorter wavelength than visible light, beyond the blue end of the spectrum. There are three categories of UV radiation (UVA, UVB and UVC). UVC is mostly absorbed by the atmosphere, but UVB and UVA can damage the eye causing corneal damage, eg snow blindness, arc eye and possibly cataract.

Table 27 Wavelengths of UV radiation

Category Wavelengths (nm) UVA 400-315 UVB 315-280 UVC 280-100

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To be classified as a UV-absorber, a spectacle lens must absorb 99% of UVB and 95% of UVA (315- 380nm).

The less strict UVB-absorber category requires 99% absorption of UVB and 50% of UVA (BS7394 part 2 2007). Plano sunglasses have more stringent requirements (BS EN 1836 2005).

Uncoated crown glass has a UV cut-off of 290nm, ie no light is transmitted by the lens below 290nm. Solid tints, photochromic lenses, high index materials and specialist UV absorbing materials can offer improved protection from UV in glass lenses.

NB Surface or coated tints will not necessarily provide UV protection, so you should check transmission curves if UV protection is required.

CR39 and polycarbonate lenses incorporate UV inhibitors as standard, since they prevent the lenses yellowing with age. UV cut-offs are around 350nm and 400nm, respectively. UV filters for resin lenses are solid, being incorporated into the molten monomer. Any level of UV protection can be incorporated, including cut-off values well into the visible spectrum which give the lens a coloured appearance. Plastic photochromic lenses absorb UV well.

NB Do not assume dipped tints provide UV protection. 7.2 Anti-reflection coatings

Light hitting a lens surface can be either refracted or reflected at the surface. Reflectance at the surface is given by the equation:

2 n - 1 P(%) = x 100 ( n +1 )

• Reflectance increases with higher index materials.

• Surface reflectance is highest at the blue end of the spectrum.

• Transmission values describe how much light passes through the lens. In the case of normal crown and CR39, 4% of light is lost at each surface by reflection, hence the transmission value is 92%.

The surface reflectance of a lens can be reduced by coating it with a film of material that has a lower refractive index (n) than the lens itself. Adding a coating means that there are now two reflections (at the film/air boundary and the film/lens boundary), but their combined effect can be practically eliminated by meeting two conditions:

• ncoating = ϖnlens

• Coating thickness x n = 1/4Α (or any odd number of 1/4Α)

The coating generally used on glass lenses is magnesium fluoride (MgF) with n = 1.38. This is not ideal for crown (n = 1.523, ideal n coating = 1.234), but is better for higher index materials.

A single layer of AR coating will only reduce reflections at a single wavelength, so multi-layer coatings (MARs) are required to cover the entire visible spectrum.

The functions of AR coatings are: • To boost light transmission by reducing light lost at surfaces by reflection. • To reduce power rings (multiple internal reflections of the edge of a lens). • To reduce ghost images (faint images formed by reflection at the surface(s) of the lens).

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7.3 Hard coats

Abrasion-resistant coatings can be applied to both surfaces of a lens, particularly organic lenses, to improve resistance to scratching. Hard coats, particularly quartz, can be applied in a vacuum chamber. They can also be applied by dipping the lenses in a liquid organic coat, or by dropping a small amount of the coating onto a spinning lens providing an even layer over the whole lens. 7.4 Tint description

Tinted lenses reflect or absorb a proportion of the light incident on a lens. The characteristics of a tint are:

• Its transmission across the electromagnetic spectrum, including the visible, UV and infra-red (IR) regions.

• The depth of tint, or luminous transmittance. Luminous transmittance, or light transmission factor (LTF), describes the amount of light transmitted by a lens as a percentage of the light falling on the lens (BS7394 part 2 2007).

• Its colour. Note that lens colour is mainly cosmetic, and does not necessarily reveal a great deal about the transmission characteristics of a lens, particularly in the invisible IR and UV ranges. 7.5 Fixed solid tints

Solid tints are manufactured by adding metallic compounds to the molten lens mixture, and can be made with high reproducibility and consistent transmission spectra. Solid tints are primarily for glass lenses; the only common solid tint for plastic lenses is a UV inhibitor.

The optical density of the tint, D, is directly proportional to lens thickness, but its relation to transmission of the lens, T, is more complex:

D = log10 • The tint density of a 1mm lens sample is half that of a 2mm sample.

• The transmission through a 1mm lens sample is not twice that of a 2mm sample.

• High-power and anisometropic prescriptions have uneven tint densities, being more deeply tinted in thicker parts of the lens.

• The tint colour can be seen all the way through the lens, not just on the surface. 7.6 Fixed vacuum-coated tints

Vacuum coating is a method used to coat the surface of a glass lens. Tiny quantities of coloured metallic oxides, one wavelength thick, are deposited onto the rear lens surface by evaporation in a vacuum chamber. Anti-reflection coats are applied over the film. Vacuum-coated tints reflect rather than absorb unwanted light and, as the coating is highly reflective, any surface dirt is noticeable. Since the coating is only placed on the lens surface, the resulting tint is not affected by lens thickness. It is difficult to reproduce accurately these tints and their transmission spectra, therefore lenses should be supplied as matched pairs, and the tints should be considered to be cosmetic.

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7.7 Fixed dipped tints

Tinting of CR39 lenses is usually achieved by dipping them in baths of hot dye. Colour density is determined by the length of time the lens remains in the dye. As with vacuum-coated lenses, it is difficult to reproduce these tints, so lenses should be supplied in matched pairs. In addition, do not assume they give protection from any specific wavelength of light unless adequate transmission curves are available. 7.8 Photochromic description

Photochromic lenses have variable light transmittance, darkening in strong light and fading when removed from it. Photochromics are classified by their transmittance (LTF) range, or the swing from maximum transmittance (fully faded) to minimum transmittance (fully darkened) value, eg 90/25 (see Table 28).

Table 28 Prescription photochromic material transmittance range

Supplier Material Luminous transmittance range Corning Photogray extra 88% – 22% Photogrown extra 88% – 22% Pilkington Borosilicate grey 91% – 17% Borosilicate B 90% – 17% Reactolite Rapide Sprint brown 80% – 8% Sprint grey 89% – 8% Zeis Umbramatic SR 85% – 25% Umbramatic SL 85% – 25% Uromatic 90% – 50% Umbramatic equitint 90% – 30% Claret um/tic 90% – 30% Tital umbramatic 90% – 30% Rodenstock Colormatic 2 90% – 50% Colormatic SB 85% – 25% Colormatic 1.6 88% – 33% Perfalit colormatic 80% – 35% Hoya Sungray extra 88% – 22% Sunbrown extra 88% – 22% Sunicity brown 90% – 50% Sunbrown extra 2 90% – 33% Norville Photal 87% – 42% Polarised photochromic 35% – 15% Essilor Transition plus 82% – 42% Signet Kodak instashades 87% – 18%

• Lenses darken more quickly than they fade, especially at low temperatures. • Transmittance values should be quoted for a specific temperature (25˚C) and thickness (2mm, most relevant to glass lenses).

In addition to the LTF range, other measurements are relevant to evaluating a photochromic lens: • Transmission characteristics over time following exposure to UV. • Transmission as a function of temperature. • Time to return to faded state or half-activated state. • Transmittance after 10 minutes’ fading.

Remember that, for glass lenses, all these values are affected by lens thickness, and hence prescription.

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7.9 Glass photochromics

Glass photochromic lenses have a solid tint construction, in that silver halide crystals are incorporated into the molten glass mixture. The halide crystals are sensitive to UV - they are darkened by wavelengths of 300-400nm, with a maximum activation at about 355nm. All photochromics show good UV protection in the darkened state. Light at the red end of the spectrum or an increase in temperature causes the glass to fade or return to a clear state. Since the tint is solid, tint density and transmission vary with lens thickness as described for fixed solid tints (section 7.5).

The wider the LTF swing, the narrower is the range of prescriptions for which a glass photochromic is suitable. This is because higher prescriptions and thicker lenses will give darker tints, and take longer to recover to a faded state. Thus recovery of lenses with narrow swings is quicker than those with wide swings, though the thicker they are, the longer they take to fade.

Photochromics with a narrow swing maintain a pale tint in their recovered state and are marketed for use ‘in the city’ with quickly changing light conditions from outside to inside. Photochromics are available in bifocal and varifocal form. In fused bifocals the segment is not tinted.

Since photochromic tint density varies with lens thickness, these lenses are not best suited to high prescriptions and anisometropia. One option for such patients is laminate photochromics or ‘equitints’. In these lenses a thin, even layer of photochromic glass is bonded to a white glass lens incorporating the prescription. Tint density is thus equal across the whole lens surface. A potential problem with these lenses is that the bond between the two glass layers can break. 7.10 Plastic photochromics

Photochromic tints for plastic lenses have been around for a couple of decades. The first products of this type were very temperature-dependent with narrow swings and finite fatigue lives. New products are much improved. The lens surfaces are coated with organic (carbon-based) dyes, so the tint is independent of lens thickness. Lens darkening is primarily caused by UV. When evaluating plastic photochromics, you should consider the factors described for glass photochromics above, bearing in mind that performance will be independent of prescription. 8. Key issues: multifocal lenses

8.1 General information Multifocal lenses include any lens that contains more than one focal power, and are usually employed to correct presbyopia. They are occasionally used for other purposes, such as for the treatment of convergence disorders. Always consider all the options when prescribing multifocals. These include dispensing separate distance and near spectacles, bifocals, trifocals, and varifocals. 8.2 Solid bifocals Solid bifocals are made from a single piece of material. They can be identified by feeling a ridge at the edge of the segment, where the curvature changes. To manufacture solid glass bifocal lenses, a large ring tool is used to grind the distance portion on the outer part of a saucer-shaped blank, and the near portion is worked with a smaller ring in the centre. The saucer is then cut in half. The round segment is usually placed on the rear concave surface and the prescription ground as required on the front surface. Plastic lenses are moulded with the round or shaped segment on the front surface.

Executive bifocals can be made in glass or plastic, with the segment surface on either side. The optical advantage of an executive lens is that the centres of curvature of the two portions lie on a line passing through the centre of the dividing line. Consequently there is no ‘jump’, wherever the distance OC is placed.

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8.3 Fused bifocals

Fused bifocals are made from a button of higher refractive index glass (often flint glass n=1.64) sunk into a well-polished front surface depression in the main lens (often crown glass), and polished down. The prescription is ground on the rear surface. Fused bifocals are not available in plastic. The potential disadvantage of fused bifocals is that flint glass has a low constringence (V value). This can lead to coloured fringes, especially just below the dividing line. However, the CA in the segment depends on the prescription, the position of the near visual point (NVP), and the type of bifocal. In some cases, CA in a fused bifocal may be less than in a solid bifocal. 8.4 Verification of bifocals

The power of the addition is equal to the difference in vertex powers on the surface on which the segment is situated. Therefore, for a back surface solid bifocal, the add is the difference between distance and near BVPs. In the case of a front surface fused bifocal, the add is the difference between FVPs, and the lens should be placed the wrong way up on a focimeter to measure add power accurately. 8.5 Segment dimensions

The near visual point (NVP) is the point on the segment through which the patient looks for near vision. The top of a bifocal segment is usually fitted to the lower lid margin when the eye is in the primary position. This segment position should be expressed as a measurement relative to the horizontal centre line (HCL) of the chosen frame (seg top position) or as a height from the bottom of the lens (seg height). The geometric inset of the segment is the half the difference between the distance PD and the near CD.

Figure 38 Basic bifocal lens dimensions

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8.6 Jump

When the eye moves to look through the near portion of a bifocal, the image is displaced suddenly at the dividing line of the segment.

The displacement is caused by base down prismatic effect, and is called ‘jump’.

• The amount of jump experienced at the edge of a bifocal segment is dependent on two things: the power of the add and the distance from the edge of the segment to its optical centre. The optical centre of the segment (‘os’ in Figure 38) is the centre of the circle of which the segment forms a part.

• Therefore the amount of jump in a round segment ( Ll ) = seg radius (cm) x add.

• In a shaped segment, the amount of jump is equal to the power of the add multiplied by the distance from the segment top to its optical centre (os). In a flat-top bifocal, this distance is minimal, so the amount of jump will be less than in the equivalent diameter round-seg bifocal.

• The segment always induces base down prism at the NVP. The amount of jump is also influenced by the prismatic effects of the main lens. A positive main lens induces prism base up at the NVP. A negative main lens induces prism base down at the NVP. The base down effect of a round segment is therefore exaggerated by a negative distance lens.

• Therefore, hypermetropes are better served by a cosmetically inconspicuous down curve segment. Myopes benefit from a D shaped segment or executive, in which the near optical centre is better controlled, which reduces jump. 8.7 Differential vertical prism

When wearing bifocals, a patient looks through the NVP of the segment, rather than the OC of the main lens, when viewing an object at near. Prism will be induced according to Prentice’s Rule: P=cF. At the NVP a positive main lens exerts prism up and out, while a negative main lens exerts prism down and in at the NVP. If the lens powers for each eye are different, as in anisometropia, there will be a differential vertical prism at near. A maximum 1-2 of vertical differential prism may be tolerated.

To calculate the vertical prism imbalance at near, use Sasieni’s method:

• Assume the NVP is 10mm below the OC.

• Vertical prismatic power difference is equal to the difference in dioptric power between the two lenses in the vertical meridian (ie axis 180). 8.8 Trifocals

Patients over 50 years old and requiring additions of at least +2.25DS have a zone of vision between distance and near which is not clear with bifocal correction.

• The range of clear vision with the distance portion is from infinity to the reciprocal of available accommodation (which is 1/3-2/3 of maximum amplitude).

• The range of clear vision with the near addition is from the reciprocal of seg power (far point) to the reciprocal of seg power plus available accommodation (near point).

To give a full range of clear vision, an intermediate add is required, which is 50-70% of the near vision add, depending on the patient’s requirements. Generally the top of the intermediate segment is fitted to the lower edge of the pupil, but this will also depend on the patient’s requirements. The position

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of the near segment will be controlled by the position of the intermediate seg, but should be roughly coincident with the lower lid margin. The trifocals available include concentric, E-type, D-type and combination. 8.9 Varifocals or progressive addition lenses

Varifocal lenses provide a gradual progression of power from distance to near, such that any distance can be seen clearly through some point on the lens. It is the front surface of the lens that contains the varifocal surface, the rear surface providing the sphero-cyl correction. The varifocal surface is achieved using a series of parabolic sections. The increase in spherical power down the lens is inevitably accompanied by an unwanted astigmatic effect. How this astigmatism is distributed across the lens depends on its design. 8.10 Varifocal designs

• ‘Need’-based designs are categorised as ‘soft’ and ‘hard’ designs. Soft designs have a more gradual astigmatic gradient in the lens periphery, but at the expense of a smaller stable reading area and distortions in the distance portion. Hard designs have a wider stable reading area, wider progression and distortion free distance area, but the progression is shorter and the distortions in the periphery of the lens are more severe, being crammed into a smaller space.

• Add-based designs vary according to add power.

• Multi-designs are those brands offering different designs for each combination of add power and type of distance refractive error. 8.11 Varifocal markings

Figure 39 Varifocal markings

To mark up a varifocal, first find the permanent engravings, using the reflections of a bright light on the concave lens surface, while you hold the lens over a dark background. Transfer the other markings from a template. 8.12 Varifocal fitting

• The pupil cross should be within 0.5mm of the centre of the pupil. Take care to be at the same height as the patient when marking the fitting cross.

• Horizontal centration (position of the eye relative to progression corridor) is more important than vertical centration (position of the eye relative to start of progression).

• Record monocular PDs.

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• Ensure there is sufficient depth of frame below the pupil centre to include the entire progression (>20mm).

• Set up the frame properly on the patient before taking measurements and use the same frame as that used for dispensing. 8.13 Varifocal verification

• For distance Rx, place focimeter on the upper checking circle.

• For near Rx, place focimeter on the lower checking circle. The add is equal to the difference between distance and near FVPs, and is engraved on lens.

• For prism, place focimeter at the prism reference point. Varifocal lenses are prism thinned to give 2/3 of the add base down in each lens, in order to reduce centre substance. The prism measured at the reference point therefore consists of any prescribed prism plus about 2 base down due to prism thinning.

If the prism measured in each eye is the same, the values cancel out. Therefore, prism value is only relevant if it is different for each eye, and hence induces relative prism. 9. Key issues: glazing

9.1 Definitions

The stages in lens manufacture are:

• Semi-finished: one side completely finished.

• Finished: both sides have the final optical surface, and the lens may be cut or uncut.

• Blank: material for making lens before completion of surfacing processes.

• Uncut: completely finished but not cut or edged. 9.2 The glazing process

Laying off is the process of orienting the uncut so that the cyl is at the correct axis and the OC in the correct place. Use the focimeter for this.

Cutting is the process of outlining the desired shape on one surface of the uncut. Cutting and edging are usually combined in an automatic cutting/edging machine by grinding the lens to the shape of a pre-cut or computer stored former.

Edging is the process of grinding the lens to the finished size and shape with the desired edge form. Edge form options include (see Figure 40):

• Bevel: Standard 115˚ angle, safety chamfered. This is unsatisfactory for high minus lenses or edge thickness variations, such as in non-round lenses or large cyls. • Mini-bevel: This is better for high minus lenses and edge thickness changes, as the majority of the lens is behind the bevel.

• Groove and cord: This is used for supras, in which the minimum edge thickness is 2mm, or as an effective mini-bevel from a smaller uncut.

• Twin bevel: This is an alternative to the mini-bevel for high minus lenses.

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Figure 40 Edging methods

Glazing is the process of inserting lenses into the frame. The requirements depend on the frame material. 10. Key issues: frames

10.1 Frame materials: general information

Examine the frames in your practice carefully to determine which materials you most often dispense. You should know about these in detail: their characteristics for identification, method of manufacture, likelihood of causing allergy, method of glazing, treatment for adjustments, and whether and how they can be mended if broken.

You should also know how to deal with any other frame material a patient may bring to you for adjustment or reglazing. The following notes are brief, and you should consult a good general reference for further details, e.g. Obstfeld (1997) or Wakefield (1994). 10.2 Plastic materials

• Cellulose acetate is the ‘standard’ plastic frame material. It softens at around 50˚C and is easily adjustable.

• Cellulose propionate needs a little more heat for adjustment than acetate. Propionate is slightly lighter than acetate and should be cleaned with water rather than alcohol or spirits.

• Optyl is a thermosetting epoxy resin with a plastic memory for its original shape. It must be heated to around 80˚C for adjustments, at which point it becomes very pliable and spaghetti-like. Hold it in shape whilst cooling to retain the new shape.

• SPX is a polyamide that should be glazed oversize due to its tendency to stretch.

• Carbon fibre should be glazed cold from the back of the frame. It is not readily adjustable.

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10.3 Metal materials

• Gold filled/rolled gold is quality marked with the mass of fine gold per 1000 parts of material, or the proportion of the mass which is made of a specified carat of gold, eg 1/10th 12 carat.

NB Identify gold by quality mark, not by gold colour!

• Gold plated frames are base metal alloy electroplated with a minimum of 1μm of gold of at least 18 carats.

• Nickel silver is one of the most common metal alloys for frames, comprising copper, nickel and zinc. It contains a minimum of 14% nickel, but different manufacturers use different proportions of materials. Nickel can cause allergic reactions.

• Titanium is used pure, in which form it is hypoallergenic and very strong but not easy to solder if broken, and in the form of clad titanium, comprising a core of titanium clad with nickel.

• Stainless steel can be used to form very thin frames. 10.4 Frame markings

Frames should be marked according to BS EN ISO 12870:2004 (which refers to 150 9456:1977). Markings should be as follows:

• Somewhere on the frame: manufacturer, model and colour.

• On the front (assuming the boxed system is used): horizontal boxed lens size followed by a square, distance between lenses, bridge width with symbol.

eg 50 18 /20\

• On both sides: length to bend or overall length of side.

• Frame or package should be marked BS EN ISO 12870 and ISO 9456 and grade A or B (where B is a child’s metal frame). 10.5 Frame description

ISO 9456 which superseded BS3521 part 2 (1991) lists the terms used to describe frames in Appendix A and sections 1 to 3. Make sure you are familiar with the different types of bridge, pads, joints, sides and lugs that are available. 10.6 Frame measurement

Measurements are expected to be expressed in the boxed system, rather than the older datum system (BS EN ISO 13666:2019) which was depreciated in 1992. 10.7 Blank size calculation

The calculation is as follows:

minimum size uncut = maximum lens aperture + (2 x decentration) + wastage

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Example 6

In Figure 41, if the maximum aperture of the lens (along the diagonal in this case) is 60mm, and 5mm of decentration is required in each eye so the eyes look through the optical centres of the lenses, then the minimum lens size required would be 60 + (2 x 5) + 2 = 72mm, and the smallest available blank size would be 75mm.

Figure 41 Basic frame measurements

11. Key issues: eye protection

11.1 Responsibility for provision of eye protection

A) The optometrist • Must assess the suitability of chosen appliance. • Must provide the most suitable ocular and housing type. • Must ensure the finished product complies with the patient’s requirements and relevant standards.

B) The employee • Must maintain the safety appliance in good working order. • Must report loss or damage of the appliance. • Must use the appliance as instructed.

C) The employer • Must assess the risks to workers. • Must supply an appropriate safety appliance. • Must maintain, repair and replace safety appliances as appropriate. • Must provide areas for safe storage when not in use. • Must advise employees regarding correct use of safety appliances and their limitations. 11.2 British/European standards

Eye protection standards EN166, 167 and 168 came into force in 1992 replacing an the old BS2092. These have since been revised further as BS EN 166:2002, BS EN 167:2002 and BS EN 168:2002. These new European standards give four levels of impact resistance (Tables 29 and 30). 11.3 Ocular and housing markings

Lenses are referred to as ‘oculars’ and frames as ‘housings’. Each feature is represented by a specific symbol marked on the ocular or housing (Tables 31a-c). The order in which the markings appear is standardised (Table 32). These can be found in EN 166 and the College of Optometrists’ Occupational Optometry module 6.

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Table 29 New levels of impact resistance

Levels of impact resistance Increased robustness Low energy impact Medium energy impact High energy impact

Table 30 Impact resistance of various eye protectors

Impact speed Type of protector Low energy impact Medium energy impact High energy impact 45m/s 120m/s 190m/s Spectacles ✔ Not available Not available Goggles ✔ ✔ Not available Face shields ✔ ✔ ✔

Figure 42 Types of appliance

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11.4 Ocular and housing materials

A) Oculars

• Toughened glass • Polycarbonate • CR39 • PMMA • Laminated glass

B) Housings

• Metal • Plastics • Polyvinyl chloride • Polycarbonate

Different hazardous conditions require specific materials to afford suitable protection. The optometrist must be aware of the indication for different materials. The housing should provide optimum visibility consistent with safety. 11.5 Properties of eye protectors

Summary of the new markings for oculars and housing and a comparison with their previous counterparts. 11.6 Filters

Oculars may also provide optical filtering. This is indicated on the ocular by the designation number followed by filter shade. 11.7 HSE guidelines

The governing legislation is the Personal Protective Equipment and Work Regulations 1993, which covers many areas of personal protection. Personal protective equipment should be a last resort - the process should be made as safe as possible. 11.8 Reglazing old appliances

Reglazing is rarely performed, and may only be done by the manufacturer. If a safety frame is reglazed elsewhere:

• It loses its protective status.

• The safety markings should be removed.

• The patient should be made aware of the appliance’s new status.

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Table 31a Characteristics designated by housing markings (numerals)

Housing symbol Designation Description in field of use None Basic use Mechanical hazards, UV and IR 3 Liquids Liquid droplets or splashes 4 Large dust particles Dust particles >5μm 5 Gas and fine dust particles Gases, vapours, dust <5μm 8 Short circuit electric arc Electric arc 9 Molten metals and hot solids Molten metal and hot splashes

Table 31b Characteristics designated by housing markings (letters)

Housing symbol Level of impact resistance Type of eye protector –F Low energy impact All types –B Medium energy impact Goggles and face shields –A High energy impact Face shields only

Table 31c Characteristics designated by ocular markings

Ocular symbol Property S Increased robustness F Low energy impact B Medium energy impact A High energy impact 9 Protection against molten metals and hot solids K Resistance to damage by fine particles N Non-fogging properties

Table 32 Order of markings

Order of ocular markings Order of housing markings 1. Scale number for filter lenses only 1. Identification of the manufacturer 2. Manufacturer’s identification mark 2. The standard number (eg EN 166) 3. Optical class 3. The field of intended use 4. Symbol for mechanical strength 4. Symbol of resistance to high speed particles 5. Symbol for non-adherence of molten metals 6. Symbol for resistance to surface damage by fine particles 7. Symbol for resistance to fogging

< Spectacles and protective eyewear

Table 33 Properties of eye protectors

EN 166 Protector type

New standard Housing Oculars Spectacles Goggles shields Face

Manufacturer’s mark ® ® ✔ ✔ ✔ Optical class Refractive power ±0.06 – 1 ✔ ✔ ✔ ±0.12 – 2 ✔ ✔ ✔ ±0.12 – 3 ✔ ✔ –0.25 Mechanical Increased robustness – S ✔ ✔ ✔ strength Low energy impact -F F ✔ ✔ ✔ Medium energy impact -B B ✔ ✔ High energy impact -A A ✔ Field of use Liquid droplets/splashes 3 – ✔ ✔ Large dust particles 4 – ✔ Gas fine dust particles 5 – ✔ Short circuit electric arc 8 – ✔ Molten metal/hot solids 9 9 ✔ ✔ Resistance to fogging – N ✔ ✔ ✔ Resistance to surface – K ✔ ✔ ✔ damage

This symbol ® indicates a trademark or other identification of the manufacturer.

Table 34 Properties designated by filter symbols

Filter number Filter property 2 UV filter and colour recognition may be affected 3 UV filter with good colour recognition 4 IR filter 5 Sunglare filter without IR specification 6 Sunglare filter with IR specification

12. Acknowledgment

Extracts from British Standards in Tables 30-34 are reproduced with the permission of the British Standards Institution. This publication is for educational use only.

Complete editions of standards can be obtained by post from BSI Customer Services, 389 Chiswick High Road, London W4 4AL.

< Spectacles and protective eyewear

Handy Hints Reflective Exercises

• Keep a copy of the spectacle tolerance • Spend a week checking in spectacles in your consulting room using a manual focimeter. Keep a log of any pairs which are near to the • Ask customers whether they have had accepted tolerance. Discuss why this a previous intolerance while might be with your store's dispensing dispensing, so you can take action to optician or lab manager. ensure it is not repeated. • Discuss any returns due to dispensing • Read some consumer press about or lens intolerance each week with a choosing spectacles. Think about the dispensing optician. What are the language used and how Specsavers' recurring themes? family of lens products can be described. • Complete a table of lenses available in your store. List the equivalent products • You can access the British Standards available locally. This will ensure you're from the College of Optometrists familiar with other brands and website. commonly used names.

• Ask to observe a dispensing optician dispense a pair of safety spectacles. What local industries require eye protection?

• Towards the second half of the year, help train new team members on sunglasses, tints and coatings