FEATURE

How to examine the visual system Part 2: , , fundoscopy and additional tests

BY E LINTON AND A FOTAKAKIS

xamining the visual system you need to be looking at the left eye you already know from the response can be a tricky skill for medical and making sure the constricts in to light shone in the right eye that students to master, yet it is a response to the light. Next, shine your the motor pathways to each eye are Etask that is frequently tested light back in to the left eye again, but working. in examinations. This is the second this time you need to look at the right The last test for the pupils is looking of a two-part series of articles, which eye and make sure that the pupil on the for a relative afferent pupillary defect together aim to improve understanding right also constricts when you shine (RAPD), using the swinging light test. of the individual components of light in to the left pupil. The first light To do this you now shine your light on the visual exam and then provide a is checking for the direct , i.e. the each eye in turn moving back and forth structure which links them together in response of the pupil directly affected between them. This highlights to you a methodical way. The previous article by the beam of light. The second light is if there is a problem with one of the focused on the first three aspects of checking for the consensual reflex, i.e. eyes that is not obvious enough to be examination: visual acuity, visual fields the response of the right eye when you picked up on the direct and consensual and eye movements. This article will shine light in to the left eye. In a normal reflex tests. The concept here is that focus on the remaining components: patient, the eyes will work together so if you shine a light in to both eyes one accommodation, pupils, fundoscopy and that they both respond equally to a light after the other in a normal individual, additional tests. source, even if only one of the eyes is the pupils will constrict equally to both exposed to it. light sources, thanks to the direct and Accommodation People classically find this a difficult consensual reflex pathways. (Cranial nerve III) topic to grasp but if you break it down The pathological response we are Testing for the accommodation reflex and get to grips with it, the test can looking for in this test is that on moving follows nicely on from eye movements. be quite useful in clinical situations. the light from one eye to the other, the Ask the patient to keep focusing on the Consider the following scenarios: pupils will appear to dilate when light tip of your index finger and slowly move 1. You shine light in to right eye. Right is shone in the affected eye. This is it towards them, aiming for the tip of eye constricts but left eye does not. because the direct reflex in the affected their nose. You need to be watching We know that the right eye has no eye is disturbed in some way, causing their pupils to make sure you see them problem in sensation because we the source of light to be determined constrict as your finger gets closer. have seen it react to the stimulus, as weaker than that shone in the good and this also tells us the right eye. The pupils still constrict, but to a Pupils eye has normal motor responses. lesser degree, so that on swinging a light ( II and III) Therefore, we can deduce that there from one eye to the other, the pupils The next step on the visual system test is a problem with the motor pathway will actually appear to dilate. Let’s put is the pupils. If you have not already in the left eye because it has not this theory in to practice: A patient with made a comment about their size and reacted to the stimulus. optic neuritis on the right eye undergoes shape then you can do so now. It is 2. You shine a light into the right eye. a swinging light test. When you shine the easier for this part for you to leave your Both pupils constrict. You shine a light in the left eye, both eyes constrict. chair and crouch / stand just to one side light into the left eye and neither When you move the light across to the of the patient with your pen torch in constrict. This indicates the defect right eye, both pupils appear to dilate, hand. is sensory in the left eye, because and then on moving the light back to Ask the patient to look ahead at a the left eye, the pupils constrict again. specific point that you give them, e.g. In this example, a defect in the right a curtain hook or the corner of a door. eye means that the direct reflex is Explain that you are going to shine your impeded, so that in comparison to the small light in to each of their eyes twice light perceived by the left eye, the right in turn, and that they should continue “The key point is to eye’s source seems inferior, and thus the to look forward at their point during this pupils do not constrict as much. test. get the patient This is a complicated test to get to Approaching from, for example, the comfortable and grips with but try and focus on the basic patient’s left side, shine your light once principles and hopefully with practice it in to their left eye. When you do this relaxed.” will become clearer.

eye news | AUGUST/SEPTEMBER 2014 | VOL 21 NO 2 | www.eyenews.uk.com FEATURE

Fundoscopy the patient how they are planning on (called the disc) surrounding an (Cranial nerve II) travelling home after the examination, inner ring (the cup). You should At this point you have almost as it will not be safe for them to drive comment on the cup:disc ratio, completed your examination of the themselves for hours after their pupils which means the size of the inner visual system from far out, right to have been dilated. cup in relation to the outer disc. the back of the eye. The fundus is the This may be more simply considered final step. If you are asked to examine by thinking of it as a doughnut, Remember all of the cranial nerves, this part of and thus the size of the hole in the trOPicamide OPens the eye the examination is often passed on to centre in relation to the doughnut save time. However, it can come up as around the edge. The ideal cup:disc a station by itself and it is a very useful ratio is reported to be 0.3, which skill to have as a junior doctor as well as When the patient is ready switch on means that the hole in the centre of later in life if you want to work in acute your ophthalmoscope and stand about the doughnut makes up three tenths medicine or general practice. a metre away from the patient, at a 45 of the whole doughnut. The larger If you are pressed for time, make degree angle away from them. If you the cup in the middle becomes in sure you explain that ideally you would are starting with their right eye, hold relation to the disc, the less healthy like to complete your examination by the ophthalmoscope in your right hand the . In people suffering visualising the fundus using a direct and look through it with your right eye from glaucoma, there is gradual ophthalmoscope. At this point the at their right eye. increase in cup:disc ratio. examiner may tell you that this is not If you cannot find the disc initially but necessary and you can breathe a sigh you are able to see some blood vessels, of relief. Remember these can be useful in helping you to If you are asked to continue, the key RIGHT RIGHT RIGHT and LEFT LEFT LEFT locate the disc. If you consider the back point is to get the patient comfortable of the eye like a tree, and the optic and relaxed. Place them on a chair in a nerve head is the tree trunk, the blood space which allows you plenty of room vessels spread out across the retina to stand on both sides of them. Explain The first thing you are looking for is a from the optic nerve like branches on to the patient that you are going to use red glow over the patient’s eye. This is a tree. This is useful because if you a light to look in to the back of their eye. called the Red Reflex. This represents track vessels back towards their main Ask the patient to focus on a specific the reflection of your light source off branches you will eventually make it point in the distance (the curtain rail the back of the patient’s red-coloured back to the disc. or corner of the door from earlier). retina. If pathology exists which Once you have taken a look at the Request that they keep focusing on this impedes the journey of the light source optic nerve head, it is important to point even if you get in the way. through the eye then the red reflex survey the rest of the retina. You could It is nice to warn the patient that will be diminished or absent. The most comment on the vessels themselves, you will need to get quite close to their common cause of this is a cataract. and whether they show signs of face in order to be able to see inside the After you have established the red proliferative retinopathy (growth very small pupils to the back of the eye, reflex slowly move in towards your of new, friable, tortuous vessels in and reassure them that you will place patient. When you are close enough response to ischaemia), venous nipping your hand on their forehead so they do place your left hand on the patient’s (a sign of hypertension) or clots. You not have to worry about you knocking forehead to prevent you clashing may spot retinal haemorrhages, or heads. As a courtesy, and to show your heads. Move slowly closer to the eye signs of diabetic retinopathy (cotton examiner that you are thinking about maintaining your 45 degree angle until wall spots). It is important to check the patient’s comfort you should warn you are close enough that you can see all four quadrants of the retina in a the patient that the bright light may the retina. Moving in from this angle methodical manner to ensure no areas cause them some discomfort, and if at should place your focus directly on to are missed. When you head out to the any time they feel as though they need the optic nerve. peripheries you may wish to ask the a rest from the light they should let you If you can spot the optic nerve you patient to look up, down, left and right know. Lastly, make sure the patient is should comment on the ‘three Cs’: to help you see a bit further. Look out happy for you to dim / switch off the colour, contour and cup-size: for burn marks from laser therapy on lights for you to get a better view of the Colour: a healthy optic disc should be the edge of the retina, which could eye with your torch. pink coloured. If the disc appears indicate treatment for proliferative In most exam situations the patient to be pale you may worry about retinopathy. will have already had their pupils pathology such as optic neuritis or The final part of your examination of dilated by the examiner, or sometimes glaucoma. the fundus should assess the macula. dilatation will not be an option. Contour: you should comment on the You should ask the patient to now Either way, it is worth mentioning to outline of the disc which should look directly in to your light, as this the examiner that you would ideally be smooth and well-defined. If the places the macula in direct view of dilate the eyes with mydriatic drops, edges are indiscriminate or blurred, your ophthalmoscope. It is important e.g. tropicamide if the patient has not this could indicate papilloedema to leave this part until the end as it is previously had any adverse effects and (swelling of the optic nerve head). uncomfortable for the patient and it if they were not known to be at risk of Cup-size: the optic nerve head can will leave them temporarily dazzled acute angle closure glaucoma. To really be thought of as resembling a afterwards thus unlikely to be able show you are thinking you should ask doughnut: it has an outer edge to focus easily. The macula can be

eye news | AUGUST/SEPTEMBER 2014 | VOL 21 NO 2 | www.eyenews.uk.com FEATURE

affected by age-related changes, known Additional tests Conclusion as age-related macular degeneration. There are two additional areas of the The examination of the visual system has This comes in two forms, wet and dry. examination of the visual system which multiple components and it can be difficult The dry type is associated with drusen you may wish to include or mention. to remember these and test them in a fluid – milky white deposits on the macular. The first is the testing of colour vision, manner, especially during high pressure The wet type is signified by the leakage which aims to identify patients suffering situations such as medical school exams. of fluid and blood from new fragile blood from various forms of colour blindness. This article was the second of a two-part vessels that form below the macula. A common tool for testing colour vision series and explained the examination of in clinical practice is the Ishihara Test, accommodation, pupils, fundoscopy and Remember which consists of a booklet in which each additional tests. It is hoped that medical 1. Ophthalmoscopy is a difficult page has a number centred on a colourful students and junior doctors reading background. You ask the patient to turn this two-part article will have gained a practical skill and one that medical each page and state the number that they better understanding of the individual students notoriously struggle to see in the centre. The Ishihara Chart may components of the visual system get to grips with. There really is not be provided in your examination in examination and how to group them no other way of mastering it than which case you could mention it just after together to form a structured approach. practising as much as you can. you have tested visual acuity or at the end 2. It can be very tempting to fabricate when you talk about additional things you what you are seeing when actually would like to do if time and resources were available. Emma Linton, you can see nothing at all. Try to Foundation Year 1 Doctor, remember if you do this that your The second area you may wish East and North to include or mention during your Hertfordshire NHS light may give you away to the examination of the visual system is the Trust, UK. examiner as they can see where it testing of contrast sensitivity. Contrast Email: elinton is shining. If they can see it shining @doctors.org.uk sensitivity is the ability to distinguish or [email protected] on the patient’s nose while you are between dark and light. The tool used in beautifully describing the details Declaration of Competing Interests ophthalmic practice is commonly the Pelli None declared. of the patient’s optic disc they will Robson Contrast Sensitivity Chart. This is probably not be too impressed. similar in appearance to the Snellen Chart, Apostolos Fotakakis, except all of the letters are the same size, 3. If you really are struggling to see Ophthalmology Registrar, anything, and time is running and they differ in contrast so the letters at Lister Hospital, Stevenage, UK. out, thank your patient and stop the top are dark and those at the bottom are light. This test may be included if examining them. Explain to the patients are complaining of falls especially examiner that unfortunately you in poor light conditions, or if they are are struggling to visualise this Declaration of Competing Interests having difficulty with their vision while None declared. patient’s fundus but ideally you driving at night. A poor outcome in the would like to examine for... and Correspondence: testing of contrast sensitivity can indicate 98 Pirton Close, Stevenage, Herts, SG1 4FH, UK. talk them through all of the above. underlying pathology of the retina, cataract disease or glaucoma.

eye news | AUGUST/SEPTEMBER 2014 | VOL 21 NO 2 | www.eyenews.uk.com