The UK Guide to Laser Eye Surgery 1 Contents 4 About the authors 5 Professor Dan Reinstein, MD MA(Cantab) FRCS(C) DABO FRCOphth FEBO, PGDip CRS, CertLRS 9 Mr Glenn Carp, MBBCh (WITS), FC Ophth (SA) (WITS), PGDip CRS, CertLRS 13 Mr Alastair Stuart, BMBS, FRCOphth, PGDip CRS, CertLRS

16 How the eye works 18 Myopia - Short-sightedness 19 Hyperopia - Long-sightedness Your eye 20 Presbyopia - Ageing eyes 21 Astigmatism 22 Understanding visual acuity - What does 20/20 mean? 24 Understanding prescriptions

26 How does laser eye surgery work?

30 Common misconceptions about laser eye surgery

34 Safety considerations of laser eye surgery is like a 34 How safe is laser eye surgery? 36 How is safety measured?

38 Questions to ask when considering laser eye surgery

44 Alternative treatment options

54 Questions about technology 56 Topography and tomography camera 56 Pachymetry 59 Very high-frequency digital ultrasound 60 Pupillometry 61 Wavefront aberrometry 62 Tonometry 64 Quality of vision measurement 66 Night vision simulation 67 Contrast sensitivity testing 68 Ocular dominance and tolerance assessment 68 Microkeratome 70 Femtosecond laser 71 Excimer laser 72 Active eye tracking 73 Wavefront-guided treatment 74 Customised wavefront optimised treatment

76 Frequently Asked Questions

92 Glossary 4 About the authors 5

Professor Dan Reinstein MD MA(Cantab) FRCS(C) DABO FRCOphth FEBO, PGDip CRS, CertLRS

Professor Reinstein is the founder of • 1997: Refractive Surgical Fellowship Professor Reinstein London Vision Clinic. He is internationally under laser eye surgeons Zaldivar, is a recognised renowned for his expertise in laser eye Arbelaez, Chacon, and Barraquer surgery, and is one of the few full-time (Clinica Barraquer, Bogota, Colombia) international Ophthalmic Surgeons in the UK to have expert in laser dedicated his entire professional life to the • 1999: Fellowship in Cornea, External field of refractive surgery. Disease and Refractive Surgery (University refractive surgery of British Columbia, Canada) Professor Reinstein completed his undergraduate education at Cambridge Professor Reinstein is recognised as one of (1981 to 1984) and went on to earn his the world’s preeminent laser eye surgeons. medical degree from Cambridge University A pioneer in his field, he is the co-inventor - an M.B. B.Chir (1989). He has received of the Artemis Insight 100 - the world’s extensive post-doctorate fellowship sub- most accurate corneal scanner, which specialty training, first in corneal surgery allows London Vision Clinic to safely treat and then in laser eye surgery, including: even very high prescriptions. He was also instrumental in the development of • 1991: Research Fellowship in PRESBYOND® Laser Blended Vision and Ophthalmic Epidemiology (Institute of ReLEx SMILE - two treatments which Ophthalmology, London) have dramatically increased the range of prescriptions that can be treated, and • 1994: Fellowship in Ophthalmology (The brought the benefits of laser eye surgery Weill Medical College, Cornell University, to thousands of patients who would New York) previously have been found unsuitable.

• 1996: Residency in Ophthalmology Continued on the next page (Mount Sinai School of Medicine, New York) 6 About the authors About the authors 7

Professor Reinstein is on the General Professor Reinstein is an experienced Professor Reinstein is the former Chief Professor Reinstein has appeared Medical Council’s Specialist Register research scientist and has made major Professor Reinstein Medical Officer of a group of 60 laser eye frequently in the media as a laser in the UK and is a board-certified contributions to the field. To date, he: has appeared surgeons across 30 clinics throughout eye surgery specialist. His television ophthalmologist in the USA and Canada. North America. During his tenure, the appearances have included This Morning, He holds professorships in New York • Has published over 175 articles in peer frequently in group grew to become the largest provider BBC Breakfast, and SKY News. He has also (Columbia University Medical Center), reviewed medical journals and over 180 the media as a of laser vision correction in the world been featured in publications ranging from Paris (Centre Hospitalier National articles for the ophthalmic press (performing over 100,000 procedures The Times and The Sunday Times to GQ d’Ophtalmologie des QuinzeVingts, laser eye surgery per year). and Harper’s Bazaar. Université de Paris VI) and Ulster • Has written or contributed to over 40 specialist (Biomedical Science Research Institute, book chapters He later joined the team at Carl Zeiss Professor Reinstein had PRESBYOND® University of Ulster). He is recognised Meditec, where he helped to develop Laser Blended Vision LASIK with Mr Carp world-wide as an expert in therapeutic • Has delivered over 550 lectures at the MEL 80 excimer laser – this was a in 2016. refractive surgery, and is frequently professional meetings on five continents revolutionary technological development, approached by other surgeons regarding and became the benchmark for the his knowledge in this area. • Has presented or published over 280 industry as a whole. Professor Reinstein scientific papers or abstracts remains the lead medical consultant to Carl Zeiss and, more recently, was a major • Is the editor for the Therapeutic contributor to the development of the Refractive Surgery section for the Journal VisuMax femtosecond laser and the MEL of Refractive Surgery 90 excimer laser.

• Has published the textbook The Surgeon’s Guide to Small Incision Lenticule Extraction (SMILE)

• Is the course director for the biannual 4-day training course on Forefront Refractive Surgery

• Has trained 13 refractive surgery fellows 8 About the authors 9

Mr Glenn Carp MBBCh (WITS), FC Ophth (SA) (WITS), PGDip CRS, CertLRS

Mr Glenn Carp is a distinguished and On completion of his training, Mr Carp has extremely skilled ophthalmic surgeon, who Mr Carp continued as a consultant undergone one of has undergone one of the most extensive ophthalmologist at the St John Eye training programs of any laser eye surgeon Hospital in Johannesburg. His areas of the most rigorous in the UK. Born and educated in South specialist interest included glaucoma and training programs Africa, he qualified as a doctor in 1996 retinal surgery, and he also held a part time in Johannesburg; he began his career in post at the Johannesburg Eye Hospital as for any laser eye Ophthalmology as an Ophthalmic Senior a private consultant. Following this tenure, surgeon in the UK House Officer, followed by a year spent Mr Carp left South Africa to develop his as a Research Officer in Ophthalmology expertise in the United Kingdom, at the University of the Witwatersrand in through fellowship training in corneal South Africa. and refractive surgery.

Mr Carp is on the General Medical Since moving to the UK, Mr Carp has Council’s Specialist Register in the UK, practised at several leading hospitals, and is also a fellow of the College of including the Western Eye Hospital, Surgeons in Ophthalmology (South Africa). Maidstone General Hospital, Preston Royal In 2000, he began his specialist registrar Hospital, and Worcester Royal Hospital. training at the St John Eye Hospital in He was selected for a prestigious one Johannesburg - Africa’s largest eye hospital. year fellowship in Cornea and Anterior He has won several awards for excellence Segment Pathology and Surgery at in his field including the Tetski Patterson London’s Western Eye Hospital under the Award for clinical research and the Elli guidance of Miss Melanie Corbett, and Dahan Registrar of the Year Award, which later undertook an 18-month fellowship in recognised outstanding performance over Laser Refractive Surgery at London Vision his specialist training program. Clinic under the guidance of our founder, Professor Dan Reinstein.

Continued on the next page 10 About the authors Interpret 11 image as Mr Carp is a member of many professional Mr Carp is a regular attendee at both organisations including: national and international congresses around the world. He has been delivering • The European Society of Cataract and presentations at the ESCRS congress for Refractive Surgery (ESCRS) over a decade, and is regularly invited to give lectures on ophthalmology to medical • The British Society for Refractive Surgery students, optometrists, and ophthalmic (BSRS) nursing teams. Mr Carp is also a Zeiss vision appointed expert and speaker for both • The Medical Contact Lens and Ocular congress symposia and training courses. Surface Association (MCLOSA) (Council He has also been responsible - alongside member) Professor Reinstein - for the training of five other clinical fellows at London Vision • The Ophthalmological Society of South Clinic in refractive surgery. Africa (OSSA) As well as being a talented and dedicated refractive laser eye surgeon, Mr Carp is • The South African Society of Cataract and recognised internationally as an expert on Refractive Surgeons (SASCRS) keratoconus and corneal cross-linking. Mr Carp had his own laser eye surgery with • The South African Society for the Professor Reinstein in 2006, and recently Prevention of Blindness - providing returned the favour in April 2016. cataract surgery to poor communities

• United Kingdom & Ireland Society of Cataract & Refractive Surgeons (UKISCRS) 12 About the authors 13

Mr Alastair Stuart BMedSci Hons, BMBS, PGDip CRS, Cert LRS

Mr Alastair Stuart has undergone multiple He has won several awards for With 14 years of fellowships on top of his training to excellence in his field including: training including become an eye surgeon, in order to become a top refractive specialist in his • The trainee prize at the London School of 3 sub speciality field. Ophthalmology in 2012 fellowships, Mr Following his graduation from Nottingham • The South West Thames trainee prize in Stuart is one of Medical School in 2008, he completed 2016 the few surgeons his two-year foundation jobs at Queen’s Medical Centre. • The best video prize at the UKISCRS to have completed meeting in 2015 From this point on, Mr Stuart decided formal refractive to dedicate his training to the field of • The best paper in refractive surgery at the surgery training. ophthalmology and was subsequently UKISCRS meeting in 2016 selected for a place on the seven-year Ophthalmology training rotations In 2016, following the completion of within the London Deanery. During this his seven-year rotation Mr Stuart was placement, positions held included Senior appointed for the prestigious year-long House Officer, Registrar, and fellow at the fellowship in corneal surgery at the world Medical Eye Unit at St Thomas’ Hospital, renowned Moorfields Eye Hospital. London. Then later in 2017, he was awarded a distinction in the Diploma of Cataract and Refractive Surgery at Ulster University and is now an honorary lecturer for the University.

He was then appointed by Professor Reinstein and Mr Carp as a surgeon at the London Vision Clinic, and holds the Certificate in Laser Refractive Surgery from the Royal College of Ophthalmologists.

Continued on the next page 14 Committed 15 to

Mr Stuart is registered as a specialist in He is a key opinion leader for refractive Ophthalmology with the General Medical surgery for Carl Zeiss Meditec and is excellence Council, and is a fellow of the Royal College frequently invited to teach optometrists, of Ophthalmologists. medical students and other ophthalmic surgeons from around the world. He is a member of the following professional organisations; Together with Professor Reinstein and Mr Glenn Carp, they deliver a four-day • European Society of Cataract and teaching programme on laser refractive Refractive Surgeons surgery, which has been attended by over 300 clinicians from over 50 countries. • UK Society of Cataract and Refractive Surgeons

• British Emergency Eye Care Society

Mr Stuart has been speaking at conferences for over a decade and regularly attends many international conferences such as the UK Ophthalmology Congress, the European Cataract and Refractive Surgery Annual Meeting and the European and International Ophthalmology Symposia. 16 How the eye works 17

How the eye works

Your eye is like a camera. Your eye has: When you look at something, four Your eye is like things must happen: a camera • A variable opening called the pupil; • The image must ‘reduce’ to fit on to the • A lens system, which includes a retina; transparent covering (the cornea, which does most of the focusing) and a spherical • The scattered light must focus at the lens inside the eye behind the iris; surface of the retina;

• A reusable ‘film’ called the retina - • The image must curve, to match the a complex layer of cells at the back curve of the retina; of the eye; • The brain must interpret the image as • Various sets of muscles, which control vision. the size of the pupil, the shape of the lens system (to control the ‘zoom’ function of In order for this to occur, muscles attached the eye) and the movements of the eye. to the lens contract and relax to change the shape of the lens system and keep the When you look at something, light passes object focused on the retina, even when through the cornea and the pupil at the your eyes move. Your nervous system front of the eye. The light is refracted by controls this complex set of muscle the cornea and the lens. The lens- which is movements. inside the eye, between the pupil and the retina - refracts (bends) this light, focusing Most vision problems occur when the it onto the retina. The retina is full of eye cannot focus images onto the retina. sensory cells called ‘rods’ and ‘cones’, which The most common problems are to do change the photons of light into electrical with the shape of the cornea, the length signals. Our nerves transmit these signals of the eye, and/or the stretchiness to the brain, and the brain interprets this as (‘elasticity’) of the lens. These common an image. issues are known as short-sightedness (myopia), long-sightedness (hyperopia), ageing eyes (presbyopia) and astigmatism. In the vast majority of cases, these issues can be corrected with laser eye surgery. 18 How the eye works How the eye works 19

Myopia Hyperopia Short-sightedness Long-sightedness

Myopia occurs when your eyeball is slightly Hyperopia occurs when your eyeball is As the eye ages, however, this ‘zoom’ gets longer or your cornea is more curved than Long-sightedness slightly shorter or your cornea is flatter weaker, so near vision becomes blurred. required for clear vision. This means that can also be treated than required for clear vision. In contrast Later, distance vision becomes blurred when the light rays come together (focus), to myopia, this means that light focuses as well. This means that people with they do so slightly in front of rather than with laser eye behind the retina, and the close vision hyperopia often require reading glasses on the retina, meaning that the image surgery can appear blurry. In younger people, before their 40s, and then require both becomes blurred. The effect of this is that many hyperopic eyes can self-focus by reading and distance glasses (or bifocals) you cannot see distant objects clearly utilising the ‘zoom’ intended for reading to from their 40s or 50s and onwards. As (for example, the numbers on the front of compensate for the blurring. with myopia, laser eye surgery can correct buses) although your close vision may be hyperopia by changing the shape of very good as your eye is naturally focused the cornea so that its focusing power is at this distance. Laser eye surgery can matched to the length of the eye. Laser correct myopia by changing the shape of eye surgery can also correct ageing eyes the cornea so that its focusing power is (presbyopia). See next page matched to the length of the eye. 20 How the eye works How the eye works 21

Presbyopia Astigmatism Ageing eyes

Everyone develops presbyopia during their A normal eye is spherical, like a football. lifetime. Most people, whether they have Astigmatism occurs when your eye is previously worn glasses or not, experience more oval shaped (like a rugby ball), the symptoms of presbyopia in their 40s - meaning that the curvature of the cornea although some people do not experience (the transparent covering at the front of it until their mid-50s. As we age, the lens the eye) is not the same horizontally as inside the eye loses its ability to change it is vertically. The result of this is that, shape and shift the focus of the eye from when light enters the eye, it is focused distance to near. Effectively, the ‘zoom’ at two different planes rather than at system in the eye becomes weaker. This a single point. Images appear blurred means that your ability to read small or distorted, and you may experience print (e.g. newspapers) diminishes and ‘ghosting’. Approximately half of all people you require different lenses for focusing with myopia or hyperopia have some on close and distant objects. Traditionally, astigmatism as well. Laser eye surgery people have used reading glasses, bifocals can correct astigmatism, whether it is or varifocal lenses to correct presbyopia, accompanied by myopia or hyperopia, or or have resorted to undergoing a Clear present alone. Lens Exchange procedure (replacing the lens inside the eye with an artificial one). However, London Vision Clinic has been using PRESBYOND® Laser Blended Vision to correct the symptoms of presbyopia for over ten years; this is a much safer and less invasive procedure than Clear Lens Exchange, as it does not require the surgeon to ‘go inside’ the eye to remove the lens. 22 How the eye works How the eye works 23

Understanding visual acuity What does 20/20 mean?

‘Visual acuity’ is the standard measure of Three lines above the normal (20/20) line It is also possible to have better than In most situations where visual acuity It is possible to a person’s ability to see clearly. When your is the 20/40 line. The letters on the 20/40 20/20 vision. For example, some patients ratios are mentioned, they refer to best see better than visual acuity is measured, your optometrist line are twice as large as those on the are able to read the 20/16 line (the line corrected visual acuity. For example, the is testing your central vision – your ability 20/20 line, so a person with normal visual below the 20/20 line) during their visual legal driving standard in the UK is 20/40, the norm - better to distinguish the details and shapes of acuity could read from twice as far away acuity test. They would be said to have a which means that a person’s visual acuity than 20/20 objects from a certain distance away. - forty feet. If the smallest letters that a visual acuity of 20/16, which means that is considered good enough to drive if they In the most common visual acuity test, person can read from twenty feet away are from twenty feet away, they can read a can read the 20/40 line from twenty feet an optometrist places an eye chart at those on the 20/40 line, that person would line that a person with normal visual acuity away, with glasses on if necessary. a standard distance (twenty feet or six be said to have 20/40 vision. (This means would need to approach to a distance of In laser eye surgery, the surgeon’s goal is metres, depending on the customary unit that the person needs to approach to a sixteen feet to read. to get your visual acuity without glasses of measurement). The patient is then asked distance of twenty feet to read letters that to the same level as your best corrected to read letters on lines across the eye a person with normal acuity could read at The biggest letter, at the top of the eye visual acuity (i.e. your vision with chart. Towards the bottom of the chart is a forty feet.) chart, is the 20/200 line. Many people glasses or contact lenses) before surgery. line known as the ‘20/20 line’ – this is the believe that they have “bad vision” because Occasionally, patients achieve even better smallest line that a person with ‘normal’ they “can’t even read the E at the top vision than this. visual acuity can read from twenty feet of the chart without glasses.” However, away. Therefore, having ‘20/20 vision’ importantly, visual acuity tests measure simply means that you have normal not only a person’s uncorrected vision visual acuity. (their vision without glasses or contact lenses) but also their best corrected vision – the best vision that they are able to achieve with glasses or contact lenses. Many people with moderate myopia (short-sightedness) cannot read the ‘E’ without glasses, but have no problem reading the 20/20 line or even the 20/16 line with glasses. 24 How the eye works 25

Understanding Optometrists prescriptions measure refractive Optometrists measure refractive errors • The first number (-5.00) identifies your - myopia, hyperopia, presbyopia and degree of short-sightedness or long- astigmatism - in units called dioptres. sightedness. The minus sign in front of the Dioptres are a measure of the amount of number identifies you as short-sighted, refractive correction you need in order to whereas a plus sign means you are long- see normally. One dioptre is the equivalent sighted; errors of a lens that can focus on an object one metre away. • The second number (-1.50) identifies the amount of astigmatism you have. This is The more short-sighted, long-sighted written with either a plus sign or a minus or astigmatic you are, the higher your sign (usually minus in the UK); prescription will be in dioptres. A typical prescription has three numbers - • The third number (180) indicates the for example: -5.00 / -1.50 x 180. axis in degrees, communicating the orientation of your astigmatism. An axis of 180 degrees, for example, means the astigmatism is horizontal.

So, a prescription of -5.00 / -1.50 x 180 indicates that the patient is moderately short-sighted, with a moderate degree of astigmatism in a horizontal direction. 26 How does laser eye surgery work? 27

How does laser eye surgery work?

Any operation that corrects the focusing ReLEx SMILE is a keyhole form of LASIK Laser eye surgery of the eye is called refractive surgery. Laser laser eye surgery. SMILE (which stands for uses a beam of eye surgery is simply a form of refractive small incision lenticule extraction) differs surgery that uses a laser to reshape your from LASIK in that the surgeon does not ultraviolet light cornea - the transparent, curved window need to create a flap in the cornea. Instead, to reshape your at the front of the eye. Adjusting the a femtosecond laser is used to create a curvature of your cornea allows light to tiny tunnel, through which the surgeon cornea be focused correctly onto the retina at the draws out a minuscule amount of corneal back of the eye. Refractive surgery is the tissue (less than 1/100th of the width of a world’s most common elective surgical human hair). The main advantage of SMILE procedure. over other forms of laser eye surgery is that it is even less invasive than LASIK, as The most popular form of laser eye surgery no flap is created. SMILE can be used to is LASIK (laser in-situ keratomileusis). treat even higher prescriptions than was During LASIK, the surgeon uses either a previously deemed possible, and is often femtosecond laser or, rarely, a mechanical a preferred option for patients with drier device called a microkeratome to create a eyes or thinner corneas. very thin corneal flap, about a tenth of a millimetre thick. The surgeon then lifts this Continued on the next page corneal flap, and uses a second (excimer) laser to sculpt the bed of the cornea. This procedure can be used to flatten the cornea (to correct short-sightedness), make it steeper (to correct long-sightedness), and make it more symmetrical (to correct astigmatism). When the surgeon puts the corneal flap back, the cornea takes on this new shape. 28 How does laser eye surgery work? With LASIK 29 and SMILE laser eye surgery,

With LASIK and SMILE laser eye surgery, For the small minority of patients who are the healing process is surprisingly short. In unsuitable for either LASIK or SMILE laser the healing almost all patients, the flap (in LASIK) or eye surgery, there are alternative ‘surface’ the tiny tunnel (in SMILE) heals within a procedures known as PRK (photorefractive matter of hours after surgery. Anaesthetic keratectomy), LASEK (laser sub-epithelial drops are used to numb the eyes during keratomileusis) and Epi-LASIK (epithelial surgery, so the procedure itself is totally laser in-situ keratomileusis). These process is painless. It is normal to experience a small procedures all involve removing the surface amount of discomfort on the evening after layer of the cornea (the epithelium), and surgery as the anaesthetic wears off, but then treating the exposed area underneath this is rarely troublesome and painkillers with a laser. To the patient, the main are provided for use if necessary. difference between LASIK or SMILE and surprisingly short these surface procedures is the healing Most patients notice a significant vision time. After a surface procedure, it takes improvement immediately after surgery, approximately 5 - 7 days for the eyes to and vision continues to improve over heal, and for vision to stabilise. the next 24 - 48 hours. The rapid visual recovery time means that the vast majority of patients can return to work within 24 hours of surgery, although it will take about 3 months before the final visual outcome will be realised. 30 Common misconceptions about laser eye surgery 31

Common misconceptions about laser eye surgery

Complications are common and serious Laser eye surgery cannot help people Laser eye surgery Laser eye surgery is very safe. Of course, no aged 40+ who need reading glasses itself is quick, and procedure is entirely without some level For over a decade, PRESBYOND® Laser of risk - the point is that the relative risk Blended Vision laser eye surgery has pain-free of laser eye surgery is extremely low when been used to correct presbyopia (ageing compared to the relative benefits. In the eyes). No procedure is able to fully hands of an expert surgeon using the best restore the eye’s zooming mechanisms technology, the chances of even a small to enable perfect distance and perfect compromise to the vision is in the order of near vision in both eyes simultaneously. 0.1% for the majority of patients. For those PRESBYOND® Laser Blended Vision is a with higher prescriptions, the risk may be form of LASIK laser eye surgery, where higher, and this will be indicated at your one eye is corrected mainly for distance screening appointment if it applies to you. vision and a little up close, while the other eye is corrected mainly for close vision Laser eye surgery is painful and a little at distance. The brain learns to Laser eye surgery itself is quick, and pain- combine the two images, giving clear vision free. With LASIK and ReLEx SMILE, you at near, intermediate and far distances. may feel a moment’s pressure early in the PRESBYOND® Laser Blended Vision is procedure. You may also experience some not to be confused with monovision mild discomfort or irritation for up to 24 (which uses contact lenses or older laser hours after the surgery, but this is usually systems to correct one eye for distance relieved with artificial tears and pain-relief and the other for near, and which some eye drops (which any good clinic should patients find difficult to tolerate). Studies provide free of charge). have shown that over 97% of presbyopic patients are suitable for PRESBYOND® Laser eye surgery is only for short- Laser Blended Vision treatment. The aim of sighted people PRESBYOND® Laser Blended Vision is to With today’s technology, patients who maximise independence from glasses, but are short or long-sighted, presbyopic or you may still need to use glasses in some astigmatic can be treated. situations.

Continued on the next page 32 Common misconceptions about laser eye surgery There 33 is no

The treatment is not permanent You could end up with worse vision than Long-term follow-up studies have you started with demonstrated that once the shape of your This question deals with two issues: cornea is changed to correct your vision, Vision without glasses – uncorrected the change is permanent. Of course, your vision loss: There is virtually no chance eye is a living organ and alters over the that your vision without glasses after laser years, just as the rest of your body does. eye surgery would be worse than without Everyone’s eyes change to some degree, glasses for the specific tasks that you age limit even if they have never needed glasses. needed them before surgery. However, studies have shown that changes after surgery tend to be very small, and Vision with glasses – loss of corrected develop very slowly. Once you reach the distance visual acuity: Your maximum age of 50, your prescription will only clarity with glasses before surgery is known change by an average of half a dioptre as your ‘corrected distance visual acuity’ every decade. (CDVA). In expert hands, the chance of your CDVA being reduced by even a small You can be too old for laser eye surgery amount is around 1 in 1,000 (0.1%) per Technically, there is no upper age limit for eye for the majority of patients. For those laser eye surgery as long as the eye with higher prescriptions, the risk may be is healthy. higher, and this will be indicated at your screening appointment if it applies to you. You can go blind This is practically impossible. Realistically, the chance of going blind from laser eye surgery in the hands of an expert surgeon using the best technology is almost too small to measure - probably in the region of 1 in 5 million. 34 Safety considerations of laser eye surgery 35

Safety considerations of laser eye surgery

Laser eye How safe is laser eye surgery? surgery is safe Laser eye surgery in the right hands, with All surgery carries some risk of the right technology and aftercare, is complications (a complication is defined and efficacious extremely safe. The National Institute for as an unexpected occurrence). In laser for use in Health and Clinical Excellence (NICE) is the eye surgery, complications are very official body that produces guidance for rare, and advances in technology and appropriately UK doctors on the effectiveness of medical surgical expertise mean that almost all selected patients treatments. In 2006, NICE completed complications can now be corrected. In a two-year, in-depth study of laser eye fact, the chance of an expert being faced surgery. It concluded that laser eye with a situation of marked permanently surgery “is safe and efficacious for use in reduced vision or quality of vision that he appropriately selected patients.” Numerous or she could not correct satisfactorily is review articles of the published literature about 1 in 30,000. on laser eye surgery have demonstrated excellent patient satisfaction, clinical outcomes, and safety. 36 Safety considerations of laser eye surgery Laser eye 37 surgery is safe and efficacious

How is safety measured? Measures of safety take into account The 2006 NICE report looked at the results for use in any risk of ‘compromise’ to your vision. of studies published in medical journals Visual compromise is defined as blurring, and found that, on average, less than 1% doubling or other distortion that cannot be of LASIK patients lost more than two lines corrected by glasses to achieve the same of best corrected vision after laser eye level of vision you had before surgery with surgery. However, for expert surgeons, the glasses (your CDVA). This is different from likelihood of an eye losing two lines of appropriately a situation in which vision is improved best corrected vision is even less. The level after surgery but there is some blurring, of risk varies slightly depending on your which can be corrected with glasses. In prescription, but on average the risk of this case the vision is not compromised, an eye losing two lines of best corrected it is simply not fully focused (and can be vision is around 1 in 1,000. For those with corrected by glasses or, more usually, by a higher prescriptions, the risk may be higher, selected patients simple enhancement procedure). and this will be indicated at your screening In terms of measuring the extent of visual appointment if it applies to you. compromise, the standard method is to The best way to ensure that your measure blurring by the number of lines on treatment is as safe as possible is to the eye chart that the patient is no longer have treatment with an expert surgeon, able to read. For example, if before surgery who chooses to operate with the best you were able to see the 20/16 line with technology and insists upon very thorough glasses, and after surgery your vision - testing before surgery and regular follow- even with glasses - is 20/25, this would be up appointments after surgery. classified as a loss of two lines of CDVA. 38 Questions to ask when considering laser eye surgery 39

Questions to ask when considering laser eye surgery

No-one should undergo any form of elective surgery without feeling fully informed, You are looking safe and comfortable. You should ask as many questions as you feel are necessary for a surgeon who to help you make a decision. However, here are some essential starting points: can show you How experienced is my surgeon? • Postgraduate Diploma in Cataract and statistics that Refractive Surgery from Ulster University To become a laser eye surgeon, you (or similar postgraduate qualification) reflect individual must be registered as a doctor with the surgeon outcomes General Medical Council (GMC). There • Certificate in Laser and Refractive is also a recommendation that laser eye Surgery from the Royal College of surgeons obtain the certificate in Laser Ophthalmologists Refractive Surgery from the Royal College of Ophthalmologists, but this is not a As a patient, you should seek a laser legal requirement. Also, the availability eye surgeon who has experience in the of refractive surgery fellowship specialist specific procedure you are interested in training is very limited in the UK, so (for example, LASIK, SMILE, PRESBYOND® many surgeons learn refractive surgery Laser Blended Vision, etc.) You should also ‘on the job’. Because of this, standards - check what range of prescriptions your unfortunately - vary within the field: it is chosen clinic can safely treat. If you have important to ask whether your surgeon a more unusual prescription, you may find has undergone formal refractive surgery that some surgeons will refuse to treat training and for how long, and whether he you; this usually does not mean that your or she is a corneal specialist. Specifically, prescription cannot be treated anywhere, you should choose a surgeon with the but rather that your chosen clinic lacks following credentials as a minimum: the experience or technology to treat your particular condition. • A Fellow of the Royal College of Surgeons /Ophthalmologists or equivalent While more experienced surgeons will have performed a higher number of • Fellowship specialty training in corneal procedures, it is important not to assume surgery that high turnover equates to a high quality surgeon. Likewise, you should be • Fellowship sub-specialty training in cautious about basing your decision on refractive (laser eye) surgery advertised complication rates - since what one surgeon or clinic officially classes as a • On the General Medical Council’s ‘complication’ may be quite different to Specialist Register another. 40 Questions to ask when considering laser eye surgery Questions to ask when considering laser eye surgery 41

Will the clinic conduct all of the How much time will you spend necessary pre-operative tests to ensure with me before my surgery? my suitability for laser eye surgery? While there is no official guideline for You should be asked to come in for a The pre-operative examination is an • Dry eye exam how long a pre-operative assessment for one-on-one consent appointment with excellent opportunity to examine the eye laser eye surgery must be, you should feel your surgeon on a separate day from fully. This should ideally include the • Pupil size that you’ve been given enough time to your initial consultation. Based on the following tests (some of which are not have all of your questions answered, and updated guidelines from The Royal College routinely carried out in laser eye surgery • Corneal thickness you should have received a full eye health of Ophthalmology, published April 2017, assessments): exam (including dilation of the pupils, a minimum cooling off period of one • Wavefront analysis which is essential to evaluating the health week is recommended between the • Refractions, including manifest refraction, of the whole of the eye). procedure recommendation and surgery. cycloplegic refraction, and CDVA • Very high-frequency digital ultrasound (if In exceptional circumstances, where a necessary) one week cooling off period is impractical • Slit-lamp examination for you, the reasons for this should be • Keratoconus screening agreed between you and your surgeon • Dilated eye examination and documented in the medical record. After conducting all of the necessary We require a minimum of one day prior • Intraocular pressure tests, the clinic should provide you with to the surgery. Even if this seems like an a clear assessment of your suitability. If inconvenience, it is very important as • Contrast sensitivity your clinician determines that you are not it gives you a chance to fully digest the suitable for treatment, they should provide information you have been given during • PRESBYOND® Laser Blended Vision you with a comprehensive explanation your initial appointment, note down any assessment (if you are presbyopic) for this. You may want to ask if there concerns you wish to address with your is another provider that may have the surgeon, and make an informed decision as • Night vision simulation technology or expertise necessary to treat to whether to proceed. It is also important you safely, even if it may not be possible at that you are given the opportunity to meet • Corneal topography (including back your chosen clinic (for example some lasers your surgeon before surgery, as they are surface, i.e. tomography) are much better at treating hyperopia than the person ultimately responsible for your others, whilst some other practices will not outcome. treat patients over 40 years of age, or may offer correction of distance vision only). 42 Questions to ask when considering laser eye surgery Questions to ask when considering laser eye surgery 43

Can I see your results for patients What percentage of patients are What aftercare regime is Will I have access to my surgeon after with a similar prescription to me? charged your advertised price? Are there provided for my treatment plan? treatment? any hidden ‘extras’? In terms of follow-up, a good clinic should This is important. A surgeon is directly A good clinic should publish their results In general, you should be cautious about follow patients for one year after surgery. responsible for the care of their patients, in clearly labelled detail, so that you can choosing a laser eye surgery clinic based on This is to give the patient’s eyes time to even if he or she has delegated some examine the results that are most relevant a cheap offer. It’s possible that you will be settle fully, and to ensure that they have aspects of the aftercare to an optometrist. to you. For example, results for patients eligible for the advertised price, but some achieved the desired outcome (or to offer You should always be told how you can with short-sightedness between -1.00 D clinics are known to ‘up-sell’, advertising them an enhancement procedure, if the contact your surgeon if necessary, and and -3.00 D will have less relevance to you a very low price that is only applicable surgeon feels there is more that can be ideally your surgeon should be the person if you have -6.00 D of short-sightedness, to a small percentage of patients. You done for them). who conducts your appointment the day or if you are long-sighted. You will need should also check what is included in after surgery. to ensure that you are looking at the right your treatment fee, and whether you will The amount of aftercare appointments group of patients in order to evaluate be asked to pay extra for eye drops and needed will depend on the procedure - for You will also be given your surgeon’s surgical results properly. aftercare (charges which can quickly add example, patients who have had surface personal mobile phone number on the day up!). treatments (PRK, LASEK or Epi-LASIK) of surgery so that you can get in touch On top of this, some clinics do not publish should be closely monitored during the immediately if you have any concerns. surgical results relating to near vision Above all, you should feel comfortable first five days after surgery. However, for after laser eye surgery. If you are over questioning why laser eye surgery is LASIK and SMILE procedures, most patients 40 and considering laser eye surgery for being offered at a discount price. None should have follow-up appointments at: presbyopia, you should ask to look at of the technology and expertise required surgical results for near vision as well for world-class laser eye surgery comes • 1 day after surgery as distance vision. Ideally, the clinic cheaply, so if laser eye surgery costs less, • 1-4 weeks after surgery would have published their results in a you should ask why - what is being cut out • 3 months after surgery scientific journal (known as ‘peer-reviewed to make it cheaper? • 12 months after surgery literature’).

At London Vision Clinic, we have published results for the full range of prescriptions including myopia up to -14.00 D, hyperopia up to +7.00 D, and cylinder up to 6.00 D. 44 Alternative treatment options 45

Alternative treatment options

While over 97% of patients have a prescription that is within the treatment range for corneal laser refractive surgery, there will be a small number that do not qualify due to their prescription, the shape of the eye or the health of the cornea. If you fall in to this category, there are alternative options available to you including phakic intraocular lens implantation, clear lens exchange, or, of course, to continue with glasses and/or contact lenses.

Phakic intraocular lens implantation the likelihood of cataract formation. The Artisan lens is now much less commonly The eye possesses a crystalline lens inside, used than the ICL. which serves to add variable power to the focusing of the eye in addition to the The Implantable Collamer Lens (ICL) focusing power produced by the cornea. The Greek word for lens is ‘phacos’. Phakic intraocular lens implantation is Therefore, inserting a synthetic lens most commonly performed using the into the eye while leaving the natural ICL made by Staar Surgical. The ICL is crystalline lens of the eye intact is referred an extremely small and thin lens that is to as phakic intraocular lens implantation. implanted inside the eye. The lens sits There are two types of phakic intraocular behind the iris and in front of the natural lens clinically available: the iris-claw lens crystalline lens. ICLs have the ability to and the implantable collamer (or contact) treat nearly every possible prescription; lens (ICL). in the UK, the lens is available to treat nearsightedness from -0.50 to -18.00 D, The Iris-Claw Lens: The ‘Artisan’ far-sightedness from +0.50 D to +10.00 D and astigmatism up to 6.00 D. The lens The Artisan lens possesses two clips comes in 4 different sizes to accommodate which grip onto the front of the iris, so patients with small, medium or large eyes. the lens sits inside the eye behind the cornea. While this lens was more popular Continued on the next page in the early 2000s due to a lower risk of inducing cataract formation compared to the ICL, long term problems related to the health of the cornea have emerged. In the meantime, several improvements made to ICL technology have greatly reduced 46 Alternative treatment options Alternative treatment options 47

The Implantable Collamer Lens (ICL) Patient selection Surgery After the procedure

In 1997 the V4 ICL model was approved Patients who are interested in pursuing The power of the lens that will be You can return to most normal daily for use in the UK, and quickly became ICLs undergo the same extensive implanted determines the surgical course activities the morning after surgery with the go-to treatment option for patients examination as all laser patients. One and number of clinic visits that is required. a few restrictions (e.g. no eye rubbing, who were not candidates for corneal laser important note is that many people who ICLs used to correct myopia have a small swimming, intense physical activity, and treatment. A few years ago, an updated are candidates for ICL have high near- hole in the center of the lens to allow for avoid dusty or dirty environments). If the model of the lens was introduced, the EVO sightedness due to an elongated eye. fluid flow around the lens inside the eye eye is stable at 1 week, all restrictions are Visian ICL, which has further improved the Therefore, it is very important that a full but ICLs used to correct hyperopia do not. lifted. You will return for monitoring visits safety of these lenses, particularly with and thorough examination of the vitreous Therefore, farsighted patients will need to on a similar schedule to laser eye surgery respect to the risk of cataract formation and retina be performed through a dilated have a very short laser procedure a few for the first year. After the 1 year visit it by introducing a tiny hole in the centre of pupil. It is prudent to document the health days before the ICL procedure to create a is important to continue with an eye care the lens. This hole – the aquaport – allows of the peripheral retina with state-of-the- small hole in the iris for the fluid to flow provider for annual check-ups including for better flow of aqueous and nutrients art wide-field imaging as certain retinal through. This is done in an exam room and a dilated retinal exam to monitor the around the crystalline lens and it is pathology can affect the success rate of takes only 1 minute for each eye. positioning of the lens inside the eye and believed to be the reason for the significant phakic intraocular lens surgery. It may the health of the eye including the back reduction in ICL induced cataract. The be necessary to be evaluated by a retinal ICL surgery is typically performed 1 eye of the cornea (endothelium), iris, lens, and second very significant improvement made specialist to ensure the stability and health at a time with 1 to 3 days between eyes. back of the eye (retina). to ICL technology is in the size selection. of the retina. Treatment of asymptomatic The surgery takes approximately 10 Previously, various formulae were used to retinal holes or tears may sometimes be minutes. After treatment you will remain As with laser eye surgery, there may estimate the size of the lens need to be required before ICL surgery. at the clinic for anywhere between 30-60 sometimes be a small prescription implanted. At the London Vision Clinic, minutes before receiving a final check remaining after the ICL is implanted. Professor Reinstein and his team have been which includes eye pressure and lens Residual refractive error tends to be very involved in optimising this element of the position review. You will use drops for small but can be addressed in a number procedure using the Artemis Insight 100 approximately 2-3 weeks after surgery. of ways. After ICL surgery there are no very high-frequency digital ultrasound. restrictions on the type of glasses or To date, over 1 million ICLs have been contact lenses a patient can wear. You implanted worldwide. can also explore laser refractive surgery to treat any residual prescription (assuming you have no corneal conditions which precluded you from laser treatment in the first place).

Continued on the next page 48 Alternative treatment options Alternative treatment options 49

After the procedure Risks and complications Risks and complications

Most patients experience a small amount Risks of ICL include pupillary block, cataract It seems intuitively obvious that direct of glare and halo in the early postoperative formation, increased eye pressure, and measurement of this space inside the period but this tends to go away within glaucoma. While these risks are low, the eye will provide better information as to a few weeks to months. In some cases, a majority are associated with choosing the which ICL size to choose, than estimating mild eye drop can be used to constrict the correct size lens. this size from external measurements. pupil and decrease glare and halo. It is important that patients be aware As previously mentioned, the lens is of the different sizing methods and It is extremely rare to remove a lens available in 4 sizes. The size is chosen ensure that surgeons are using this most because of subjective complaints, but since based on measurements taken during advanced method to minimize the chance an ICL does not alter the natural state of the preoperative evaluation. The of complications or needing an ICL lens the eye it can be taken out and you can go majority of providers, both in the UK and exchange surgery. back to wearing glasses or contact lenses. internationally, still use measurements of the outside of the eye to estimate the dimensions inside the eye, which in turn determine the lens size that should be implanted. However, the anatomy inside the eye where the lens will sit, does not always correlate sufficiently with the external measurements. The most advanced method for ICL sizing is to use the Artemis Insight 100 VHF digital ultrasound scanner to directly measure the area inside the eye behind the iris where the lens will be sitting. 50 Alternative treatment options 51 It is important that patients be aware of the

Clear lens exchange

Clear lens exchange (CLE), also known as There are several inaccuracies in the refractive lens exchange (RLE), is exactly information often provided to patients different sizing the same procedure that is used for regarding CLE. The first is the often- cataract surgery, but in eyes where there cited advantage that CLE provides is no cataract in the lens. As with ICLs, permanent vision correction. While the CLE can be used to correct almost any change in refraction due to the procedure prescription. is permanent, the cornea reshapes methods continuously from the age of 40, and this In CLE, your own internal crystalline lens is change affects the prescription in about a removed and a synthetic implant is placed third of all individuals, usually by changing inside the capsular bag that contained the astigmatism. Therefore, it is possible for the natural lens. The implanted lens is the refraction to shift slightly after CLE due similar to an ICL, but it is placed inside to natural changes to the cornea. the capsular bag, whereas an ICL is placed in front of the natural lens. Because the Another proposed advantage of CLE natural lens is removed, and the implanted is that it removes the need for future lens has a fixed focus, CLE also removes cataract surgery as the natural lens has any remaining function of the eye’s ability been removed during the CLE procedure. to change focus. Therefore, an ICL is usually This is as opposed to undergoing a corneal preferred when treating patients under refractive laser procedure that leaves the the age of 65, whereas CLE is usually used natural lens intact, but cataract surgery for presbyopic patients with little near may be required later in life. However, focus reserves. In some patients with high only 30% of individuals in the UK, a hyperopia outside the range for laser eye predominantly Anglo-Saxon population, surgery, there may also not be enough actually go on to have visually significant space inside the eye to place an ICL, so CLE cataracts that require surgery. would be the only surgical option available for such patients. Continued on the next page 52 Alternative treatment options 53

Therefore, the future possible need for With all of that being said, it is very cataract surgery should be weighed up important to measure if, or to what extent, against the comparatively higher risks of any natural lens changes are happening intraocular surgery, particularly for patients before making a decision about lens younger than 60. Although it is intuitive to surgery. Changes to the lens begin as early most people that going inside the eye to as 40 years old so it is normal for someone replace a lens that is still transmitting light to have “yellowing” of the crystalline lens (not a cataract) is more invasive and less far before it affects the vision. Normal safe than performing a laser procedure on aging changes to the lens are sometimes the surface of the eye, this point is often referred to as “a little bit of cataract” or overlooked or minimized. Catastrophic “early cataract” or “dysfunctional lens risks such as bleeding or infection are syndrome.” As mentioned, these changes indeed very rare. However, CLE patients are are completely normal. Using a microscope, generally younger than those undergoing providers can visualize the crystalline lens normal age-related visually significant but it is extremely important to objectively cataract surgery so it is important to quantify the changes. As part of a normal understand there is a higher risk for retinal lens evaluation, and before making any detachment or swelling in the back of the surgery decision, a number of instruments eye. should be used to help quantify the changes. These include the HDA Optical The last point to consider is evolving Scatter Index (OSI), Oculus C-QUANT, and IOL technology. While the current IOL Tracey iTrace. technology is very good and can provide a range of vision after surgery, there are In conclusion, CLE is a vision correction still limitations that include, glare, halos, option for patients but must be discussed and decreased contrast sensitivity. As IOL thoroughly and weighed against all other technology improves, it is expected that options. As stated in The Royal College of new designs will evolve over time that Ophthalmology Guidelines, all alternative decrease the side effects and provide a interventions need to be discussed that more natural range of vision. could meet the vision correction needs with less risk, including from other practitioners. 54 Questions about technology 55

Questions about technology

There are six technologies that most laser eye surgeons use. These are:

• Topography and tomography • Wavefront aberrometry • Pachymetry • Excimer laser • Pupillometry • Femtosecond laser

Below is some more information about these technologies, as well as some others. We will explain how they measure your eyes, the readings they produce, how accurate they are, and the effect they have on your treatment.

Topography and tomography

What is it for? What actually happens? Topography and tomography are for You rest your chin on a padded support measuring the shape of your corneal and stare straight into the examining surfaces. The topographer captures an instrument. The clinician sits in front of you image of your eye to create a topographic and aligns the instrument by having you map of the front surface of the cornea. focus on a visual target. They will ask you Tomography can also capture the shape of to open your eyes widely to take a number the back surface of the cornea. of multi-coloured pictures that are printed and added to your medical record. The pictures are like maps, where the different colours show the different elevations of your corneal surface(s) and the thickness profile of your cornea.

Continued on the next page 56 Questions about technology Questions about technology 57

Topography and tomography Pachymetry Pachymetry

How does it feel? What is it for? What actually happens? You feel nothing as the instrument does Pachymetry is for measuring corneal There are three main types of pachymetry: not make contact with your eye. thickness - specifically, a pachymeter measures the depth of the thinnest point Hand-held ultrasound probes: Optical pachymetry devices: How does it benefit you? of your cornea. A topical anaesthetic drop is placed in each You rest your chin on a padded support Topography and tomography are some eye to numb the surface of the eye for and stare straight into the examining of the most important safety factors Hand-held pachymetry is traditionally used approximately 15 minutes. The optometrist instrument. The clinician sits in front of you in determining your suitability for primarily to measure the central area of then sits or stands in front of you and and aligns the instrument by having you laser eye surgery. It is important that the cornea where the cornea is thinnest. gently holds open your eyelid. They will focus on a visual target. They will ask you both topography and tomography be It takes single point measurements of the then gently touch a hand-held probe onto to open your eyes widely to take a number performed at your pre-operative screening. corneal thickness. the surface of the eye to take readings of of multi-coloured pictures that are printed Topography (measured using instruments the thickness of the cornea. and added to your medical record. The such as the Atlas or Keratron) provides the Corneal pachymetry can also be pictures are like maps, where the different most accurate measurement of the front mapped using optical devices such as Very high-frequency ultrasound colours show the thickness profile of your surface of your eye, while tomography the tomography scanners described 3D scanning: cornea and some optical devices can also (measured using instruments such as above (MS-39, Pentacam, etc). The gold In VHF digital ultrasound, you have your measure the epithelium. the MS-39, Pentacam, Orbscan and standard for pachymetry measurement eyes numbed with anaesthetic drops, and Galilei) measures the shape of both the by optical devices is an optical coherence have your eye positioned over a watertight Continued on the next page front and back surfaces of the cornea, tomography (OCT) scanner. rubber eyepiece. The eyepiece is then filled and the thickness profile of your cornea. with warm saline solution (like artificial The information provided by this 3D Very high-frequency (VHF) digital tears). Several arc-scans of the entire map of your cornea is essential for ultrasound is the most precise way to cornea are made to generate the thickness determining whether there are any corneal measure the thickness of the cornea. In profile of each individual layer within the abnormalities or if it is too thin for surgery addition, it provides 3D thickness profiles cornea, most importantly the front layer to be safe. In patients with very irregular of the individual layers of the cornea, of skin on the cornea (the epithelium). corneas, topography-guided treatments allowing improved diagnostic capabilities This scan can also be used to measure can be performed to achieve a more for both pre-operative and post-operative the thickness of the corneal flap following regular corneal shape. analysis. LASIK.

Both tomography and VHF digital ultrasound provide important information about the shape of the cornea that is used to screen for abnormalities such as keratoconus. 58 Questions about technology Questions about technology 59

Pachymetry Very high-frequency digital ultrasound

How does it feel? How does it benefit you? What is it for? How does it benefit you? Hand-held ultrasonic pachymetry is not Along with front and back surface Ultrasound is used to provide extremely VHFU is the most accurate way of painful - anaesthetic eye drops are used, tomography, measuring the thickness of precise measurements of the front surface measuring most internal structures of the so you will not feel the probe touching your cornea and epithelium is one of the of the eye (cornea and epithelium) as well eye, particularly the cornea and structures the eye. most important safety factors in laser eye as structures inside the eye (iris, ciliary behind the iris. Before surgery VHFU surgery. Using a pachymeter together with body, and crystalline lens). allows for earlier diagnosis of conditions During VHF digital ultrasound scanning, a topography device provides very accurate which can affect the outcome and safety the eye is comfortable in the warm eye data and ensures that the thickness of your What actually happens? of corneal refractive surgery. For example, bath. The measurements are taken through cornea is within safety limits. Your surgeon Very high-frequency digital ultrasound micronic changes to the epithelial cells sound waves that travel through the saline uses these measurements to determine (VHFU) with the ArcScan Insight 100 (front layer of skin on the cornea) can be solution - so no instruments will touch the whether you are suitable for surgery and imaging takes approximately 3-5 minutes. detected using VHFU that can indicate eye. which type of treatment is the safest While sitting, you will lean forward and the first signs of keratoconus (a corneal option for you. rest your head on a chin-rest, as with most condition in which modifications to the In optical pachymetry scans, the patient eye tests. The eye is then placed against standard corneal laser refractive surgery, feels nothing (as in a topography/ VHF digital ultrasound scanning is also one a soft goggle (like a swimming goggle) or other options, must be made). After tomography scan). of the most sensitive ways of diagnosing which is then filled with saline solution. surgery VHFU allows for the most accurate keratoconus - an eye condition that While you are looking at a fixation monitoring of the healing response as prevents patients from having laser light, the ultrasound device, without well as improved decision making and eye surgery. touching the eye, scans in front of the management of further care. eye. The soundwaves produce a detailed The most advanced and accurate cross-sectional image of the cornea and VHFU is also used in phakic IOL surgery, pachymetry device is the Artemis Insight structures inside the eye. such as ICL sizing. VHFU is the most 100 VHF digital ultrasound scanner. accurate way to measure the structures This measures corneal thickness more How does it feel? inside the eye that affect the outcome of accurately than OCT, tomography or hand- The surface of the eye is anesthetized surgery, particularly the parts of the eye held ultrasound machines. It produces a 3D before the exam with an eye drop. The behind the iris that can only be imaged by image that displays the thinnest point of eye is then gently rested in a “water bath” ultrasound. The high resolution imaging the cornea with great accuracy, and shows which can initially feel a little cool. There is accurately measures specific landmarks a profile of the depth of your cornea. This no other sensation throughout the exam. inside the eye including the sulcus, ciliary technology is currently only available in a Most patients describe the experience as body, and crystalline lens position. Accurate handful of clinics around the world. soothing. measurements of these structures can help better predict the final position of the phakic IOL and therefore decrease the risk of complications (see phakic IOL section). 60 Questions about technology Questions about technology 61

Pupillometry Wavefront aberrometry

What is it for? How does it benefit you? What is it for? This means the surgeon can plan your Measuring your pupil size. The pupillometer Accurate pupillometry is crucial for Measuring the optical imperfections of treatment precisely to incorporate these measures the average pupil size, variation successful laser eye surgery, because lasers your eye that are not correctable with irregularities. in pupil size over a fixed time frame, and are only capable of treating a defined area glasses alone (these are known as the difference in pupil size between the two of the eye. Typically, this is a circle with a ‘higher order aberrations’ in your visual What actually happens? eyes in three different light levels. diameter of 6 mm to 8 mm, depending on system). These irregularities of your cornea You rest your chin on a padded support the laser used. If your pupils were larger and optical system affect the finer quality and stare straight into the examining What actually happens? than the area that can be treated by the aspects of your vision (beyond the normal instrument. The clinician sits in front of you You are positioned with both eyes viewing laser, you would be left with an untreated refractive errors of short-sightedness, long- and aligns the instrument by having you a spot light through padded eyepieces. The ring around the smaller circle corrected by sightedness, presbyopia and astigmatism). focus on a visual target. You will be asked clinician then measures the size of each the laser. It would be like looking through to open your eyes widely. The clinician pupil in three different light levels, using an a clear patch in the middle of a smeared A wavefront aberrometer records data will then take one or more readings of the infrared camera. window. Some people with large pupils can from the light passing through your eye’s ‘wavefront’ of each eye. only be treated by specific lasers that are optical system (the lens and cornea). How does it feel? capable of covering larger areas. A map of the imperfections in your eye How does it feel? You feel nothing as the instrument does is then produced, as well as a visual You feel nothing as the instrument does not make contact with your eye. Secondly, some patients have an increased system analysis. not make contact with your eye. risk of experiencing night vision changes (such as halos and ‘starbursts’ around Different aberrometers measure different How does it benefit you? lights) after surgery. Accurate pupil size resolution with the number of spots The information mapped by a wavefront measurements for dark and dim lighting (measurement points) ranging from as aberrometer can be fed into the laser to conditions allow your surgeon to optimise low as 60 to as high as 1200. Recently, a achieve better results. Using wavefront your treatment plan to minimise the risk of new device has been introduced that uses aberrometry allows your surgeon to this occurring. a different measurement method and has decide if you would likely benefit from increased the resolution to 40,000 points. a ‘Wavefront Guided’ laser eye surgery A low resolution aberrometer is like a treatment (which aims to improve on the watercolour painting. It provides a general optical imperfections of your eye, beyond impression of the landscape, measuring what glasses alone can correct). Wavefront just a few points and using a mathematical technology can also detect certain eye formula to work out an approximate image conditions that would preclude you from of the rest. A high resolution aberrometer getting an optimal laser eye surgery result. is more like a photograph – it records much more data, giving a more accurate map of the number and location of imperfections. 62 Questions about technology Questions about technology 63

Tonometry Tonometry

What is it for? A slit lamp is a special microscope with How does it benefit you? Measuring the pressure inside your eyes. a light source, to which a tonometer is The inside of the eye is nourished by the Optometrists and ophthalmologists attached. The optometrist will direct a production of fluid, which drains out of measure eye pressure (also known as broad beam of blue light from the slit the eye; if there is an imbalance between ‘intraocular pressure’, or IOP) as part of a lamp into your eye while they gently move the rate at which the fluid is produced routine eye examination, to screen for eye the slit lamp forward until the tonometer and the rate at which it is drained away, diseases such as glaucoma. probe lightly touches your eye. Your the intraocular pressure may increase or optometrist can directly measure your decrease from its normal level. Measuring One method of tonometry is the ‘air-puff’ intraocular pressure by adjusting a tension changes to the IOP is important, as these method. In this test, you rest your forehead dial on the tonometer. changes can affect other structures in the on a padded support and stare straight into eye such as the optic nerve. Increased the examining instrument. The instrument How does it feel? pressure inside the eye is often associated then blows a small puff of air onto your In air-puff tonometry, nothing but air with glaucoma. Glaucoma is a treatable eye. The tonometry instrument estimates directly touches the eye. You will hear the condition but, if left untreated, it can be the pressure inside your eye by measuring puffing sound and feel a coolness or mild devastating - which is why early diagnosis the change in the light reflected off the pressure on your eye. This may make you is so important. cornea as it is temporarily indented by flinch, but it is not uncomfortable the air-puff. The clinician may perform the or painful. procedure several times for each eye. Goldmann tonometry is not painful. The Alternatively (or additionally) your optometrist will use anaesthetic eye drops optometrist may perform Goldmann to numb the surface of your eyes so that tonometry (or a similar ‘applanation you will not feel the instrument touching method’). In applanation methods, your cornea during the test. anaesthetic drops containing a fluorescein dye are placed in the eyes to numb the surface. Your optometrist will ask you to stare straight ahead whilst resting your chin and forehead against special supports on an instrument called a slit lamp. 64 Questions about technology Questions about technology 65

Quality of vision measurement Quality of vision measurement

What is it for? What actually happens? How does it feel? The light distortion analysis system is a Vision can be thought of being made up You rest your chin on a padded support You feel nothing as the instrument does method for measuring the size and shape of two elements – the quantity and the and stare straight into the examining not make contact with your eye. of halos and starbursts, based on patient quality. Vision ‘quantity’ is the visual acuity instrument. The clinician sits in front of feedback when looking at a point light (see earlier section), measured by reading you and aligns the instrument by having How does it benefit you? source. letters on a standard vision chart and is you focus on a visual target. Depending on Measuring the quality of vision in addition recorded as 20/20, for example. However, the device, you may be asked to provide to quantity of vision provides your surgeon The highest standard of care includes it is possible to have 20/20 vision, but feedback to what you can see by clicking a with a complete picture of what you see. measurement of at least contrast still not be satisfied with your vision due button. This information can then be correlated sensitivity before and after treatment to quality of vision symptoms, such as with the other scans and tests to make to ensure that visual quality has been halos, glare, starbursts, double images, or a confident and informed diagnosis, maintained. It is uncommon for laser reduced contrast sensitivity. Therefore, it and consequently make an appropriate refractive surgery to significantly reduce is important to measure the quality of treatment recommendation. For example, quality of vision, and such changes are vision in addition to quantity of vision. A these can be used to assess the visual manageable with further treatment in the number of different devices are available significance of early cataract formation. majority of cases. These devices are found to measure different aspects of quality of at only a few refractive surgery clinics, but vision. Examples of devices that measure quality are integral to the management of patients of vision include the following. The HD who are not satisfied with their quality of Analyzer evaluates how light is scattered vision. by the eye (known as the objective scatter index), providing a picture of what a point light source looks like for the patient. For example, this picture would be a small circle in a normal eye, whereas the picture becomes larger and more distorted in an eye with a cataract. The C-quant also evaluates light scatter, known as straylight, and works using feedback from the patient when viewing different image patterns. 66 Questions about technology Questions about technology 67

Night vision simulation Contrast sensitivity testing

What is it for? How does it feel? What is it for? How does it feel? Measuring your night vision disturbances. You feel nothing. Measuring your ability to distinguish You feel nothing. This test provides your surgeon with a objects in low contrast situations. Assessing picture of how your vision is affected by How does it benefit you? your ability to see contrast between How does it benefit you? glare at night, so that they can design a This test provides your surgeon with images in low lighting conditions provides Night vision disturbances may be induced customised treatment plan to maintain or subjective feedback which they then an important measure of your visual by laser eye surgery. This is more likely in enhance your night vision after surgery. match with the objective measurements function at night. It gives your surgeon an patients with high prescriptions or large that have been taken of your wavefront, understanding of how you see things in pupils. Measuring your contrast sensitivity What actually happens? refraction and topography, allowing them the real world as opposed to just black-on- provides your surgeon with a further The optometrist asks you to look at a to custom design the optimal treatment white (100% contrast) letters on a chart. measure of how well you already see at computer simulation of common night for you. Occasionally, people complain of poor night, giving an indication of how best to vision disturbances, such as halos and vision in dim lighting conditions yet have plan your treatment in order to avoid night ‘starbursts’ around light-emitting objects normal or very near normal black-on-white vision disturbances. (e.g. oncoming car headlamps and street visual acuity. This is often because they lights). They then vary the size and have reduced contrast vision. In general, lasers using ‘aspheric treatment brightness of these disturbances to try to profiles’ will be safer with respect to night simulate how you see at night. What actually happens? vision. Some laser systems are so well You are shown images of grey stripes, designed that they can even improve shapes or letters. The images are shown in contrast sensitivity and night vision in sequences, and the contrast (the difference some patients. between the colour of the image and the colour of the background) reduces each time, so that it becomes more difficult to distinguish the image. You are challenged to recognise the stripes and letters as the contrast decreases, until it is so faint that you can no longer recognise whether there are stripes, or what the letters are. 68 Questions about technology Questions about technology 69

Ocular dominance and tolerance Microkeratome Microkeratome assessment What is it for? How does it feel? What is it for? What is it for? The microkeratome is a high-precision, During this part of the procedure, you may Assessing your tolerance for PRESBYOND® The microkeratome is a high-precision, computer-controlled instrument that the feel a small amount of pressure. This may Laser Blended Vision and enabling your computer-controlled instrument that the surgeon uses to help create the corneal feel a little strange, but it is not painful. surgeon to design a customised treatment surgeon uses to help create the corneal flap in LASIK. As this happens, your vision will dim or go plan that will correct both your distance flap in LASIK. dark for a few seconds. and near vision at the same time. What actually happens? What actually happens? You lie down on the laser bed facing up. How does it benefit you? What actually happens? You lie down on the laser bed facing up. After anaesthetising your eyes with eye The main benefit of a flap in LASIK is that Your optometrist focuses your non- After anaesthetising your eyes with eye drops, the surgeon holds your eye open the healing and recovery time is much dominant eye for near vision while drops, the surgeon holds your eye open using a lid holder. The microkeratome shorter than with surface procedures (PRK, leaving your dominant eye focused for using a lid holder. The microkeratome holds your eye steady by creating suction LASEK and Epi-LASIK). The flap heals within distance. They will then measure your holds your eye steady by creating suction between it and your cornea and is then hours, and the vast majority of patients binocular vision at distance and close up between it and your cornea and is then used to make a circular corneal flap with can return to work the day after surgery. to determine whether you are likely to be used to make a circular corneal flap with a hinge. The surgeon folds the flap back suitable for a Blended Vision correction. a hinge. The surgeon folds the flap back to expose the inner surface of the cornea, to expose the inner surface of the cornea, which is then ready for reshaping. In many How does it feel? which is then ready for reshaping. In many clinics, the flap creation is done using a You feel nothing. clinics, the flap creation is done using a femtosecond laser. femtosecond laser. How does it benefit you? If you are over 40 years old, PRESBYOND® Laser Blended Vision can significantly reduce or even eliminate your dependency on reading glasses, bifocals or varifocals. 70 71

Femtosecond laser Excimer laser

What is it for? How does it feel? What is it for? How does it benefit you? Today, the majority of surgeons use You may feel some light pressure and Laser refractive surgery for the correction The excimer laser is an extremely high- a femtosecond laser instead of a gentle pushing and pulling but no of refractive error. In short-sighted patients, precision sculpting tool that changes the mechanical microkeratome when discomfort. This may feel a little strange, the laser flattens the cornea in the central focusing of the eye. It enables specialist creating a LASIK flap. A femtosecond but it is not painful. While the suction is zone. In long-sighted patients, the laser eye surgeons to reduce or eliminate the laser is also the type of laser used to applied, your vision will go fuzzy. steepens the central cornea by removing need for glasses or contact lenses. perform a SMILE treatment. Common tissue in the periphery. In astigmatic brand names of this technology include How does it benefit you? patients, the laser flattens or steepens the There have been significant strides made IntraLase, ZLASIK and VisuMax. Femtosecond lasers allow the surgeon cornea in one meridian (direction), in order in laser technology over the last two to create a thinner flap than is to make the cornea more spherical (round decades, but finding a surgeon who has What actually happens? possible using a microkeratome. The instead of oval). the experience and expertise to use the You lie down on the laser bed facing up. femtosecond laser has also enabled the technology to best effect is critical to After anaesthetising your eyes with eye SMILE procedure to be possible. The laser beam will be a certain size successful treatment. Some excimer laser drops, the surgeon holds your eye open and a certain shape. The point where the brands are Alcon, Bausch and Lomb, Nidek, using a lid holder. Your eye is held steady laser touches the eye is called a spot. Schwind, VISX, WaveLight and Carl Zeiss. by creating suction between it and the The smaller the spot, the more focused it laser. A femtosecond laser beam is then is, creating a higher intensity beam that used to create a bubble layer within the moves around the eye at a faster rate. cornea to delineate a circular corneal This means the laser only removes the flap with a hinge in LASIK, or a refractive material it needs to, providing a more lenticule in SMILE. In LASIK, the surgeon precise treatment. folds the flap back to expose the inner surface of the cornea, which is then What actually happens? ready for reshaping. In SMILE, the You lie back on a bed and look into a surgeon manually removes the lenticule flashing light. In the space of seconds, the in one piece through a small 2-mm laser removes a tiny, precise amount of keyhole opening. corneal tissue to alter the optical focusing properties of the eye. 72 Questions about technology Questions about technology 73

Excimer laser Active eye tracking Wavefront guided treatment

How does it feel? What is it for? You will hear the buzzing sounds from the Tracking and compensating for your eye What is it for? How does it feel? laser, and some patients report seeing a movements during surgery. The purpose of Trying to improve on the optical Please see excimer laser section. ‘kaleidoscopic’ light. However, you will not the eye tracker is to enable the laser spot imperfections of your eye beyond that feel anything during the treatment. Some to be delivered to the right position on the which glasses alone can correct. How does it benefit you? patients also report smelling a ‘burning’ cornea. A small percentage of patients may benefit odour (similar to the scent sometimes Wavefront Guided treatments usually from a Wavefront Guided treatment. In emitted from a hair dryer). This is not What actually happens? result in better outcomes. However, it is general, most patients would benefit more actually a burning smell; it comes from the The eye tracker monitors your eye’s worth noting that this is still an evolving from a wavefront optimised or customised breaking of carbon bonds in the tissues of natural micro-movements and calculates field – in fact, some Wavefront Guided tissue removal ablation profile (the shape the cornea. positional corrections needed to place the treatments actually are actually less of tissue removed by the laser). laser spots in the right place on the cornea. effective than the standard treatments In addition, should your eye move outside on the same laser. Asking your surgeon of the treatment zone, the eye tracker to provide data on the relative benefit ‘pauses’ the laser until the eye is back in of Wavefront Guided treatment is position (this is called passive tracking). recommended, as some clinics will charge extra for this. How does it feel? You do not feel the eye tracker. What actually happens? The measurement obtained from Wavefront Aberrometry (see page 46) is combined with the prescription in your glasses, using software that delivers a customised shape change to the cornea. 74 Questions about technology Questions about technology 75

Customised wavefront Customised wavefront optimised treatment optimised treatment

What is it for? What actually happens? How does it feel? Tailoring the treatment to your eyes, Customised Wavefront Optimised Please see excimer laser section. accounting for more than just the treatment software goes beyond ‘generic’ prescription in your glasses. Customised Wavefront Guided treatments (see How does it benefit you? Wavefront Optimised treatment planning above). In simple terms this is like the Customised treatment planning increases software enables the highest level of difference between a standard ‘off the your chance of achieving the best possible customisation for each individual eye, peg’ suit that you would find on the High visual result. It reduces your risk of night based on night vision simulations, contrast Street and a bespoke suit that has been vision changes such as glare, halos and sensitivity and other corneal and ocular custom-tailored. Using specialised bespoke starbursts to the absolute minimum, and parameters. software, your surgeon can change the maximises the depth of focus achievable parameters of your treatment based on the by PRESBYOND® Laser Blended Vision. wavefront measurement to create an even better result than that obtained by simple Wavefront Guided treatment. 76 Frequently Asked Questions 77

Frequently Asked Questions

Q: Can laser eye surgery treat the loss of reading vision? Q: Which procedure will I be suitable for? Yes. The loss of reading vision occurs due to ageing, as the eye begins to lose its The vast majority of patients undergoing ability to ‘zoom’ from distance to near. This laser eye surgery worldwide are suitable means that the close vision deteriorates. for LASIK, and most short-sighted patients Some clinics choose to treat presbyopia by are also candidates for SMILE. In the past, removing the natural lens inside the eye patients with thin corneas tended to be and replacing it with an artificial one. recommended for surface procedures (PRK, LASIK and Epi-LASIK) as these do not However, there is also a laser eye surgery require the creation of a corneal flap. procedure called PRESBYOND® Laser Blended Vision, which is highly effective Many of these patients can now be treated and much less invasive than lens with SMILE - a totally ‘flap-less’, keyhole replacement. With this technique, one procedure, which was first introduced eye is treated to view objects mainly at in the UK at London Vision Clinic in distance and a little up close, while the 2011. However, a small minority remain other is treated to view objects mainly candidates for surface treatments only, and up close and a little at distance. The brain some patients may only be suitable for an learns to combine the two images, enabling intraocular lens procedure, either an ICL or the individual to see far and intermediate CLE. distances and up close, without effort. Studies have shown that 97% of people are suitable for PRESBYOND® Laser Blended Vision, and almost all are able to read normal newsprint without glasses after surgery. 78 Frequently Asked Questions Frequently Asked Questions 79

Q: How long should I be out of contact lenses before the Q: Are both eyes treated at the Q: How long does laser eye consultation with my surgeon (‘surgeon consultation appointment’)? same time? surgery take?

Yes. Large scale studies conducted over a The treatment takes only minutes and the decade ago demonstrated that there was laser itself is only active for seconds. no difference in safety between single- eye surgery and bilateral surgery. In fact, Contact lens type Length of time lenses need some evidence suggests that it is actually Q: What happens if I look away, to be out before the consent safer to treat the second eye immediately blink, cough or sneeze during the appointment with the surgeon following the first eye. There are, of course, procedure? certain situations where your surgeon may All soft contact lenses (including toric At least 1 week before suggest treating one eye at a time, but this Nothing. Although your eye will move and extended wear) would generally be due to specific during surgery, eye tracking technology medical issues. ensures your safety when this happens Rigid gas permeable worn for At least 4 weeks before - the laser tracks your eye hundreds of (RGP) 0-10 years times every second, and compensates for Q: What will I feel during and after the any movements. In the SMILE procedure, laser eye surgery procedure? the eye is immobilised by the vacuum worn for At least 8 weeks before connection to the laser. 10-20 years There is no pain involved during laser eye surgery. You will be given a topical worn for At least 12 weeks before anaesthetic to numb your eyes - most Q: What is the risk of a complication 20-30 years patients report feeling some pressure on during laser eye surgery? the eye (which can be a strange sensation) True hard lenses At least 12 weeks before but not pain. Many LASIK and SMILE Laser eye surgery is safe, but no surgery (polymethyl methacrylate) patients do not experience any discomfort is entirely without some level of risk. after surgery - although it is normal to Thankfully, an expert surgeon will have experience some grittiness, light sensitivity the knowledge to manage complications and eye watering for the first 24 hours. properly, and will usually be able to correct After surface procedures (PRK, LASEK and any complications that do occur. In the Epi-LASIK), the eyes take a few days to hands of an expert surgeon, the chance heal. However, patients should not find the of something going noticeably wrong healing process painful, as they are given is around one in 1,000 procedures. The pain-relief medication and fitted with chance that such a surgeon would be faced bandage contact lenses. with a situation he or she would not be able to correct satisfactorily is about one in 30,000. 80 Frequently Asked Questions Frequently Asked Questions 81

Q: Can I take a tranquiliser or sedative Q: What is wavefront? Q: Is my prescription too high? However, some surgeons have the (e.g. Valium) prior to the procedure? expertise and technology that allows them In most cases, having a very high to safely treat much higher prescriptions – Rules about this will vary between clinics. Wavefront treatment has received a lot prescription will not stop you having laser a full correction is sometimes possible on Generally it is better to not use sedatives, of publicity. However, it is important to eye surgery. The range that any surgeon prescriptions of: as these can alter patient cooperation remember that not all wavefront systems can treat depends on their technology and • Myopia up to -14.00 D during the procedure. However, patients are as good as each other (see Technology experience, but technology and expertise • Hyperopia up to +6.50 D who suffer from anxiety disorders such section earlier). Wavefront sensors measure in the field is now so advanced that the • Astigmatism up to -6.00 D. as panic attacks, claustrophobia etc. may the unique optical imperfections of your vast majority of patients with very high benefit from judicial use of sedatives. If eye, called ‘higher order aberrations’. These prescriptions are now suitable for a ‘full If your prescription is higher than this, this applies to you, your surgeon should irregularities of your optical system affect correction’ and, for those patients with you should not be disheartened as it discuss the risks and benefits of sedatives the finer quality of your vision, beyond extremely high prescriptions, laser eye may be possible to significantly improve thoroughly with you, before surgery. what glasses are able to correct. The most surgery can still be used to achieve a your vision with a partial correction. Never self-medicate. Your medical team advanced wavefront technology can be significant improvement in the vision, or an Alternatively, you can consider intraocular should provide the necessary required used to customise your treatment to intraocular lens procedure could achieve a procedures such as an ICL or CLE, which medical dose. account for these higher order aberrations, full correction, either an ICL or CLE. can be used to correct almost any meaning a safer and more accurate prescription. treatment. If you are turned away by a clinic, it is Q: Do laser eye surgery results differ important to remember that this often between prescriptions? does not mean that you are not suitable Q: Am I too old / too young? Q: I have astigmatism, can I still have - it may simply mean that your chosen Yes. In general, results decrease as laser eye surgery? clinic does not have the technology or Laser eye surgery patients must be at least prescriptions increase. Results also differ experience necessary to treat you safely. 18 years old; there is no upper age limit. between short-sightedness and long- Yes. Laser eye surgery can treat sightedness. Therefore, when reviewing a astigmatism at the same time as it corrects clinic’s results, it is important to look at short or long-sightedness. No extra Q: What range of prescriptions can be Q: Does everyone get presbyopia? results for prescriptions that are similar procedure is needed. treated? to yours as these will provide you with Yes. Presbyopia typically develops during a more accurate picture of your chosen The majority of laser eye surgery is the 40s (although some patients do not clinic’s success rates. performed on patients with: begin to lose their reading vision until • Myopia up to -8.00 D their mid-50s). When presbyopia develops, • Hyperopia up to +3.00 D people begin to need glasses for reading • Astigmatism up to -4.00 D. even if they have never worn glasses before. People who previously wore glasses will need a different prescription for reading than for distance (e.g. bifocals). 82 Frequently Asked Questions Frequently Asked Questions 83

Q: What are the risks of laser eye • Ectasia, which occurs in about 4 in 10,000 As with any surgical procedure, there is a surgery? cases, is a progressive deformity that risk of infection after laser eye surgery. The makes the cornea thinner and steeper. risk of a corneal infection is approximately Laser eye surgery is, by any medical • In about 1 in every 5,000 cases, patients It can be treated with corneal cross- the same as one year of soft contact lens standard, a safe procedure. However, as develop irregular astigmatism after linking (CXL), by suturing (stitching) the wear (about 5 in 10,000 patients). As with all surgical procedures, there are some surgery. Contact lenses can usually flap to the underlying cornea, or in rare with any ophthalmic procedure there is a risks to consider. Fewer than 3% of LASIK correct this form of astigmatism (glasses circumstances with a corneal transplant. very remote risk, estimated as less than procedures result in any complications. The will not). People who have very high When identified early, it is very unlikely 1 in 4,000,000, of the loss of an eye, with chance of having a serious complication is prescriptions have a higher risk of this to lead to further visual degradation with partial or total blindness. much less than 1% generally and probably complication. Irregular astigmatism can appropriate treatment. Ectasia is more less than 0.3% with an expert surgeon. The happen even if the surgery is perfect, likely to occur in eyes with a condition most common complications and side- but your risk is increased if you have an known as keratoconus. Therefore, it is effects of laser eye surgery are as follows: inexperienced surgeon or one who does important to undergo intensive and not use the best equipment. detailed screening for keratoconus before • In about 1 in 1,000 LASIK cases, the flap surgery. Currently, the most sensitive is too short, thin or uneven. If this occurs, • Epithelial ingrowth is a potential method for detecting keratoconus is to the flap is put back in place to heal. The complication of LASIK that occurs in less use thickness maps of the epithelium surgeon will not use a laser on your eye than 1% of cases, in which epithelial in combination with topography and and your vision will likely be unaffected, cells begin to grow and multiply under tomography (see the sections on but you can try surgery again in a few the corneal flap. The most common technology). This method was pioneered months. treatment is lifting the corneal flap, by Professor Reinstein and has become removing the cells, irrigating the interface accepted by ectasia experts around the • Wrinkles in the flap (striations) occur in and repositioning the flap. Most cases, world as an important component to about 1 in every 1,000 LASIK procedures. if managed appropriately, have a good keratoconus screening. Striations can cause astigmatism. The outcome. most likely causes are either rubbing your eyes before they are fully healed, or the surgeon not lining up the flap properly when it is replaced. If the wrinkles are causing astigmatism, a second procedure can be done to lift and smooth out the flap. If they are not causing any problems they can be left untreated. 84 Frequently Asked Questions Frequently Asked Questions 85

• Most laser eye surgery patients A minor enhancement procedure can If you do have glare and halos at night Q: How does the flap stay in place in experience some temporary dryness usually address this. For the small minority because of your pupil size, there are a few LASIK? after treatment. In certain people, the of patients who are not candidates for techniques that can help. Some patients condition is long-lasting. Eye drops can an enhancement, wearing glasses can find that keeping the overhead light on Initially, the flap is kept in position by provide relief, but up to 5% of patients generally get rid of any troublesome inside their car when driving stops their a vacuum effect. The cells lining the have persistent dry eye symptoms up to symptoms. pupils dilating so much that it affects their inner surface of your cornea - known as 1 year, and 1% longer than 1 year. vision. There are also medicated eye drops endothelial cells - pump water out to the The size of your pupils can be another that stop the pupil from dilating fully, and inner part of the eye. This creates suction, • Glare and halos are probably the most cause of glare and halos. If a patient’s some patients find that these fully alleviate which holds the flap in place. During the common side-effect of laser eye surgery. pupils dilate (open) beyond the area of the the problem. Alternatively, clinics with first few hours after surgery, the outer Most patients indeed experience some cornea that has been treated during laser access to an excimer laser that includes surface of the cornea - known as the level of glare and halos at first, but this eye surgery, this can cause glare and halos a topography-guided treatment option epithelium - seals the edges of the flap. generally goes away over a period of in low light conditions. The risk of this can perform a second treatment that can Over the ensuing weeks, natural substances a few weeks to a few months. Those can be mitigated by accurately measuring reduce these symptoms. inside your cornea bond the flap to the who do have lasting effects usually only your dilated pupil size before surgery. The underlying tissue. experience symptoms at night, and most surgeon can determine whether or not Finally, glare and halos can be caused if the do not find them troublesome. Symptoms they can effectively treat a large enough area of your cornea treated by the laser can usually be improved by further area of your cornea with the laser, and if is off to one side (known as ‘off-centred surgery. The causes are below. this is not possible then the surgeon should ablation’ or ‘decentration’). Choosing a decide not to treat you. properly qualified and experienced surgeon Q: What causes glare and halos and can can help to minimise the risk of this serious it be treated? complication. Specialist clinics will be able to perform a topography-guided treatment There are several reasons why a patient to re-center the treated zone and improve might develop glare and / or halos after the quality of vision. laser eye surgery: In general, using advanced wavefront If you have been ‘under-corrected’ (i.e. technology can significantly reduce the risk if the shape of your cornea has not of glare, halos and night vision difficulties been changed enough during your resulting from surgery (see Technology procedure), you may still be slightly short section for further detail). or long-sighted and/or still have a minor astigmatism. Laser86 Eye Frequently Asked Questions 87 Surgery is

Q: What conditions may prevent me from having laser eye surgery? suitable The following list includes conditions or circumstances that prospective patients commonly ask about when discussing suitability for laser eye surgery.

Condition or Can the person have laser eye surgery at the Circumstance London Vision Clinic? for 98% of Older than 60? Yes. There is no upper age limit for laser eye surgery, as long as your eyes are healthy. Some older patients experience a longer healing period after laser eye surgery, but this can be discussed at your initial screening if it is likely to apply to you.

Pregnant or No. Laser eye surgery is not recommended until 2 patients breastfeeding? months after breastfeeding is complete. Increased hormonal activity during pregnancy and breastfeeding can affect visual outcomes and, while this is not dangerous, it increases your likelihood of being under- or over-corrected and therefore requiring an enhancement procedure. The medications used before, during and after laser eye surgery could also be transmitted to your unborn baby - this should be avoided.

Taking prescription Yes, probably. You should indicate which drugs you are drugs? taking (prescription or otherwise) during your initial screening. Occasionally, certain medications can prevent you from having laser eye surgery - however, this is rare.

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Condition or Can the person have laser eye surgery at the Condition or Can the person have laser eye surgery at the Circumstance London Vision Clinic? Circumstance London Vision Clinic?

Younger than 18? No. All laser eye surgery patients must be at least 18 Have a connective Perhaps. These conditions can be associated with years old before treatment. tissue disorder altered healing responses by the body and therefore (i.e. rheumatoid present a slightly higher risk of complications after laser Have amblyopia Yes. The aim of laser eye surgery is to achieve the same arthritis)? treatment. However, if the connective tissue disorder is (lazy eye)? level of vision as you had with glasses before surgery. controlled, it is likely that you will be suitable. We assess Having a lazy eye does not mean that you are unsuitable this on a case-by-case basis and will provide you with an for laser eye surgery, and many patients with a lazy answer at your initial screening. eye have had very successful overall outcomes - i.e. the surgery achieved the same level of vision as with glasses Have had a Yes. However, it depends on the severity of your before surgery, but can also improve the peripheral detached retina? condition. Laser eye surgery does not treat a detached vision. If you have ever been told that you have a lazy retina itself. eye (also known as amblyopia) you should mention this at your initial screening, so that your options can be discussed in detail with your optometrist. Have dry eyes? Probably. Your suitability for laser eye surgery will depend on the cause and severity of the dry eye, and it is likely that you would be recommended for Have astigmatism? Yes. Laser eye surgery has been used to treat SMILE rather than LASIK surgery (or occasionally for a astigmatism since 1994. surface procedure, if the dry eye is especially severe). To ensure optimum safety, serious dry eye conditions are Have a cataract? Yes. Whilst laser eye surgery does not ‘cure’ a cataract, sometimes monitored for several months (or even years) a mild cataract (which is not significantly affecting before surgery. the vision) should not prevent you from having laser eye surgery. Should the cataract worsen, you can still have successful cataract surgery after laser eye surgery Have epilepsy? Yes. (although you should be aware that cataract surgery after laser eye surgery is a specialist field, which Have glaucoma? Yes. Laser refractive surgery is not a treatment for may limit your choice of surgeon for your cataract glaucoma, but your surgeon will work in conjunction procedure). In cases of cataracts that are already with your glaucoma specialist to ensure that your affecting the vision, you would usually be recommended glaucoma management is not affected by your laser to have cataract surgery (lens replacement), combined eye surgery. with a laser ‘top-up’ procedure to fully focus the vision if required. Have hepatitis C? Yes. You should indicate this when you have your initial screening. Have a collagen Yes. You should indicate this when you are having an vascular disease? initial screening. Have HIV? Yes. You should indicate this when you have your initial screening. Have a Perhaps. We assess this on a case-by-case basis and will compromised provide you with an answer at your initial screening. Have (or have Only if there has not been a reoccurrence of the immune system? ever had) herpes infection for at least 12 months prior to having the infection of the procedure. eye?

Continued on the next page 90 Frequently Asked Questions Frequently Asked Questions 91

Condition or Can the person have laser eye surgery at the Condition or Can the person have laser eye surgery at the Circumstance London Vision Clinic? Circumstance London Vision Clinic?

Have diabetes? Yes, if the diabetes is controlled and you don’t have any Have night vision Yes. signs of active diabetic retinopathy. To be sure, you’ll disturbances? need to be examined for this at your initial screening. Patients with uncontrolled diabetes are not suitable for Have nystagmus Yes. Laser eye surgery will not treat the nystagmus, laser eye surgery. (involuntary eye but can be safely performed with the use of sensitive movements)? eye tracking systems (which are now fitted to most Have ever had Only if there has not been a reoccurrence of the modern lasers). iritis? condition for at least 12 months prior to having the procedure. Have only one Yes. But have to consider the greater risk. good eye? Have keloid Yes. scarring? Have prism? Yes. However, you may still need prism glasses if you have double vision with contact lenses or without the Have No. Keratoconus is a progressive disease that results prism in your spectacles. keratoconus? in the thinning of the cornea. Therefore, removing corneal tissue with laser treatment is inadvisable as Have strabismus Yes. However, laser eye surgery techniques alone will not it will further destabilise the shape of the cornea. (squint)? resolve a strabismus problem, unless the strabismus is a However, London Vision Clinic can successfully fully accommodative squint (this is seen in some long- stabilise keratoconus - or protect patients from further sighted people whose eye turns in without their glasses progression - through a treatment called cross-linking. If or contact lenses but is perfectly straight with glasses or you have ever been told that you may have keratoconus, contact lenses). In general, laser eye surgery is unlikely to please mention this as early as possible so that we can be able to restore vision beyond that which is attainable conduct the necessary investigations and direct you to with glasses or contact lenses. the right treatment pathway.

Have systemic Yes, if it is well controlled. Your surgeon will assess your Have large pupils? Yes. With our custom programmed treatments, we have lupus suitability on a case-by-case basis. successfully treated patients with very large pupils erythematosus? without inducing night vision disturbances.

Have thin corneas? Perhaps. If you have been turned down for laser surgery Have macular Yes. However, it should be noted that laser eye surgery due to corneal thickness, it is worth having a complete degeneration? does not treat macular degeneration itself. If your preoperative assessment with us, including a VHF digital central vision is significantly reduced as a result of ultrasound examination with the Artemis, to rule out macular degeneration, laser eye surgery may provide keratoconus. If you have thin corneas but do not have little improvement to your uncorrected central vision keratoconus, you will likely still be a candidate for laser (although it is likely to improve your uncorrected eye surgery using SMILE or a surface procedure. peripheral vision). 92 Glossary Glossary 93

Glossary

A D

Ablation Astigmatism Contrast sensitivity Decentration Dry eye Epithelium The removal of organic material from the A condition in which the surface of the The ability to perceive differences between A potential complication of laser eye The term ‘dry eye’ is used to describe a The outer surface layer of the cornea – cornea by an excimer laser in laser eye cornea is not spherical, but shaped like a an object and its background, i.e. the ability surgery. In perfect centration, the centre of variety of disorders with similar symptoms: the skin. Measurement of the thickness surgery. rugby ball. An astigmatic cornea focuses to distinguish a grey object on a grey the corneal ablation exactly coincides with discomfort, a feeling of dryness, burning or profile of the epithelium is one of the most incoming images on two separate points background. the centre of the visual axis. This allows stinging, grittiness, foreign body sensation sensitive methods for detecting a condition Accommodation in the eye, creating a distorted image. for sharp, focused vision – like looking and photophobia. called keratoconus. The automatic adjustment of the eye for The second number on your glasses Cornea through the very centre of your spectacle seeing at different distances, usually via prescription refers to your degree of The transparent covering at the front of lens. If the area of your cornea treated by Excimer laser changes in the convexity of the lens inside astigmatism. the eye. Most laser eye surgery procedures the laser is off to one side, this is known E An argon-fluoride laser that emits the eye. work by changing the curvature of the as decentration (or ‘off-centred ablation’). ultraviolet light in pulses, at a wavelength cornea. Decentration can cause various symptoms, Ectasia of 193nm. The term excimer comes from Acuity B including edge glare or even monocular An outward bulging and thinning of the the concept of ‘an energised molecule with The sharpness or clarity of vision. The most Corrected distance visual acuity (CDVA) double vision. Other factors, such as the cornea due to raised internal eye pressure two identical components’. Each pulse common measure of visual acuity is the Bifocals A measure of a patient’s best possible size of the pupil, the amount of light in and/or a weakened cornea. of this cool laser removes 1/4000th of Snellen acuity chart used by optometrists Corrective lenses that have two powers visual clarity whilst wearing corrective your surroundings, and the size of the a millimetre of tissue from the targeted and ophthalmologists. Normal visual acuity of correction. Typically, most of the lenses, such as glasses or contact lenses. ablation zone will affect the severity or Endothelium surface, by breaking the bonds between the is known as ‘20/20 vision’. lens is used for distance vision while a presence of symptoms. The inner layer of cells on the inside molecules of collagen. It would take about smaller area is for near vision. Bifocals Crystalline lens surface of the cornea. 200 pulses from an excimer laser to cut a Amblyopia and varifocals are normally prescribed for See ‘Lens’. Dilation human hair in half. Amblyopia, also known as ‘lazy eye’, is a individuals with presbyopia (ageing eyes). The process by which the pupil enlarges, Enhancement condition where the vision in one eye is Cross-linking (CXL) usually in low light conditions. Alternatively A secondary laser eye surgery treatment not fully developed, often due to lack of Binocular vision Corneal cross-linking is a procedure where dilation can be induced artificially by or retreatment, performed to refine or Continued on the next page use in early childhood. The blending of images seen individually riboflavin drops are put on the eye and special eye drops, which is necessary to improve the original visual result. by each eye into a single image. illuminated with UV light. This causes a examine the health of the back of the eye. Artemis / Insight chemical reaction to occur within the Epi-LASIK A trade name for a very high-frequency cornea to create bonds between corneal Dioptre (D) See Laser Assisted Epithelial Keratomileusis. (VHF) digital ultrasound scanner C layers and increase the overal strength of A unit of measurement of the refractive manufactured by ArcScan Inc, which the cornea. Cross-linking is used to treat power of a lens. Epithelial ingrowth measures corneal thickness to the accuracy Cataract patients with keratoconus or ectasia. A potential complication of LASIK, in which of 1 micron. It produces a 3D image, which A condition caused by the clouding of the Double vision epithelial cells under the corneal flap begin means it can detect the overall depth and natural lens inside the eye. Also called ‘ghosting’, this means seeing to grow and multiply. The most common thinnest point of the cornea with great double images. For example, looking at treatment is lifting the corneal flap, accuracy. Clear Lens Exchange (CLE) a clock and finding that some of the removing the cells, irrigating the interface A surgical procedure, similar to cataract numbers appear to have a lighter image and repositioning the flap. Most cases, surgery, in which a surgeon removes the repeated next to them. if managed appropriately, have a good crystalline lens from the eye and replaces it outcome. with a clear plastic intraocular lens (IOL). 94 Glossary Glossary 95

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Far-sightedness Halos Keratectomy Laser assisted sub-epithelium Micron (µm) Off-centred ablation See ‘Hyperopia’. Images from light sources look blurred Surgical removal of corneal tissue. keratectomy (LASEK) A unit of length equal to one-millionth of See ‘Decentration’. with circles radiating outward from the A surgical procedure to reshape the a metre. Femtosecond laser centre. Halos can appear as a complication Keratoconus cornea by detaching the epithelium with Ophthalmic A femtosecond laser is a laser that emits of refractive surgery but they also occur A disorder that causes thinning and an alcohol solution that softens it and Microkeratome To do with the eye. optical pulses with a duration of 1/4000th naturally. asymmetry of the cornea. The normally allows it to be rolled back into a flap. After A surgical device for creating a flap of of a second. Femtosecond laser technology symmetrical shape of the cornea excimer ablation to correct the vision, the corneal tissue, used in older forms of LASIK. Ophthalmologist is used for the SMILE laser eye surgery Hyperopia becomes distorted. A cone-shaped bulge flap of epithelium is repositioned over the Most modern laser eye surgeons now use a A medical doctor who specialises in the procedure, and to create a corneal flap in Also known as far-sightedness or long- develops, and this can result in significant cornea. femtosecond laser to create corneal flaps, diagnosis and medical or surgical treatment LASIK. sightedness. Hyperopia occurs when the visual impairment. Laser eye surgery instead of a microkeratome. of eye diseases. Ophthalmologists have eyeball is too short from front to back or is not recommended for patients with PRESBYOND® Laser Blended Vision medical degrees and further specialist Focusing power the focusing mechanism is too weak. This keratoconus. These patients may consider A laser eye surgery technique for the Monovision training. Ophthalmologists are usually The cornea is responsible for about two- causes light rays to be focused behind, cross-linking to strengthen the cornea. correction of presbyopia, in which one A technique using contact lenses (or older trained as surgeons, but some choose not thirds of the focusing power of the eye. As rather than on, the retina. People with eye is treated to view objects mainly at laser systems) to overcome the effects of to perform surgery and work as medical light enters the eye, it is focused by the hyperopia have difficulty seeing objects Keratomileusis distance, but a little up close and the other presbyopia by correcting one eye for near ophthalmologists. An ophthalmologist may cornea. Then, as the light passes through that are close by. A refractive surgical technique in which a is treated to view objects mainly up close, vision and the other for distance vision also prescribe glasses and contact lenses. the pupil, the lens adjusts the focus, thin, circular flap of the cornea is removed, but a little at distance. The brain combines – not to be confused with PRESBYOND® depending on the distance of the object frozen, reshaped on a lathe and replaced the images and enables the individual to Laser Blended Vision, which is a more Optic nerve being viewed. Close objects, such as a book I upon the cornea. clearly at all distance. sophisticated procedure. The optic nerve is a bundle of nerve fibres, or computer screen, require more power about the diameter of pencil, which passes than distant objects, such as traffic signs. Intraocular Lens (also called crystalline lens) Myopia through the back of the eyeball and Inside the eye. L The natural lens of the eye is located Also known as near-sightedness or short- connects the retina to the brain. The optic behind the iris. It helps rays of light to sightedness. Myopia occurs when the nerve carries visual messages from the G Intraocular lens (IOL) Laser focus on the retina. The lens is transparent, eyeball is too deep from front to back photoreceptors of the retina to the brain. Silicone, acrylic or plastic lens used to LASER stands for Light Amplification by but with age, it can become cloudy (this or the eye’s focusing mechanism is too Ghosting replace the natural crystalline lens of the the Stimulated Emission of Radiation. is known as a cataract). The lens has the strong. This causes light rays to be focused Optical zone See ‘Double vision’. eye. See also ‘Clear Lens Exchange’. Laser light is composed of one colour ability to ‘zoom’ its focus from distance to in front of, rather than on, the retina. The area within which the corneal shape is (wavelength), travelling in one direction, near; however, this reduces with age (this is People with myopia have difficulty seeing changed by the surgery. Intraocular pressure (IOP) and each light wave is in step with the known as presbyopia). distant objects. Pressure inside the eye. next. This makes laser light millions Continued on the next page of times more powerful than ordinary Long-sightedness daylight. See ‘Hyperopia’. N J Laser in-situ keratomileusis (LASIK) Near-sightedness Joules A surgical procedure to reshape the See ‘Myopia’. Joules is the unit of measurement of central cornea, decreasing or eliminating energy. myopia, hyperopia, and astigmatism. The surgeon creates a flap in the cornea, and the exposed eye surface below is reshaped using an excimer laser. After altering the corneal curvature, the flap is replaced. It adheres quickly, without stitches. 96 Glossary Glossary 97

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Optician Pachymeter Refraction Retina Topography / Tomography Wavefront An expert in making and fitting glasses. An A device that measures the thickness of A test to determine the best glasses or The light sensitive layer of cells (rods and A technology used to determine the A technology used to determine and optician may also be qualified to dispense the cornea. contact lenses to correct a refractive cones) on the inner, back surface of the shape of the front and back surfaces of measure higher order aberrations. These and/or fit contact lenses. error (myopia, hyperopia, presbyopia or eye that converts light images into nerve the cornea. This is used to detect any aberrations affect the finer quality Peripheral vision astigmatism). ‘Refraction’ also refers to impulses. These are then sent along the abnormalities in the shape of the cornea, of the vision. While conventional eye Optometrist The ability to see objects and movement the bending of light by the use of a lens or optic nerve for transmission to the brain. most importantly to detect eyes with examinations can detect two types of An optometrist is a non-medical eye outside the direct line of vision. other material. keratoconus, in which laser eye surgery error on the cornea: spherical (myopia and health provider, who specialises in the Retreatment should not be performed. Topography data hyperopia) and cylindrical (astigmatism), examination, diagnosis, treatment, Photorefractive keratectomy (PRK) Refractive error See ‘Enhancement’. can also be used by some laser systems wavefront diagnostics can detect an management and prevention of diseases A surgical procedure using an excimer laser A measurement of visual imperfection. to plan a topography-guided treatment, infinite set of ocular aberrations – this and disorders of the visual system. In the to reshape the central cornea, to give a The degree to which images received by which can be used to smooth the shape of information can then be used to create a UK, optometrists complete a three year flattened shape for people who are myopic the eyes are not focused on the retina S the cornea if it is irregular. customised treatment plan. degree at University. Many optometrists or a more curved surface for people who (causing myopia, hyperopia, presbyopia or dispense glasses and contact lenses. are hyperopic. astigmatism), measured in dioptres. Snellen visual acuity test Optometrists may not prescribe medicine, The Snellen test is the most common test V as they are not medical doctors. Plano Refractive lens exchange used to determine visual acuity. It uses a No refractive error. See ‘Clear lens exchange’. white chart with the big black letter E at Visual acuity Over-correction the top, followed by lines of letters that See ‘Acuity’. An outcome of refractive surgery in which Presbyopia Refractive surgery descend in size. The test gives a result such the resulting amount of correction is more Part of the normal process of ageing. As we Any surgical procedure that alters the as 20/40, which means that the person can Visual field than desired. Over-correction occurs most become older, the crystalline lens begins focusing power of the eye (including, but see an item 20 feet away with the same The extent of an area seen by the eye in frequently when healing does not occur as to lose its ability to zoom from distance to not limited to, the laser eye surgery and clarity as a normally sighted person can a given position of the gaze. The central predicted. It can usually be treated easily, near vision. To compensate for this, people intraocular procedures covered by the see at 40 feet. See also ‘Acuity’. visual field is directly in front of the object with an enhancement procedure. wear reading glasses such as bifocals. guide). at which we are looking. The peripheral SMILE visual field is ‘side vision’. The fields in each Pupil ReLEx SMILE See ‘ReLEx SMILE’. eye partly overlap. The small black circular space in the centre Often known simply as SMILE (small of the iris. The pupil changes its diameter in incision lenticule extraction). SMILE is an Starbursts response to different light levels, becoming evolution of LASIK laser eye surgery, in Images from light sources blur, with spikes bigger in the dark and smaller in bright which a tiny amount of corneal tissue is radiating out from the centre. Starbursts light. The pupil controls the amount of removed through a ‘keyhole’ incision – no can be a complication of refractive surgery, light reaching the retina and the depth of flap is created. but may also occur naturally. focus of the eye.

Pupillometry A diagnostic test to measure the size of your pupils. Address Local Telephone 138 Harley Street 020 7224 1005 London W1G 7LA Overseas Telephone United Kingdom +44 20 7224 1005

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