To gain more standard CET points for this year s PAYL series, enter online at: or MODULE 11 PART 8 COURSE CODE: C-8160

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1 BLUE JULY 25.qxd: 7/8/08 09:34 Page 30 This issue : Free Worth 2 standard points MODULE 11 PART 8 COURSE CODE: C /07/08 Refractive surgery - Pre-operative assessment, selection criteria and patient counselling Bruce Allan MD FRCS FRCOphth Refractive surgery has made the transition from the fringes to the centre ground in contemporary ophthalmology, and is gaining increasing traction in the UK population as an alternative to contact lens wear or spectacle correction. Key steps in pre-operative assessment are: procedure selection, risk evaluation, and preoperative counselling. An understanding of each of these elements is becoming integral to modern optometric practice. Refractive surgery is not normally performed until the spectacle prescription has been stable (no change greater than 0.50D) for two years. Spectacle prescriptions typically stabilise in the late teens or early twenties for myopic patients, and later for hypermetropic patients, who are able to compensate by accommodation whilst younger, and often only become spectacle dependent in mid-life. Refractive surgery is not normally performed in patients under 18 years of age. Laser and implant based techniques are available to reduce or eliminate the need for spectacles in patients with any level of refractive error. For younger patients, good distance vision in both eyes is usually the aim. For presbyopic patients, monovision or multifocal strategies are commonly employed to achieve a greater all round reduction in spectacle dependence. Procedure selection Lower refractive errors are typically corrected using wavefront guided excimer laser techniques, whereas higher errors are corrected using implant based approaches. Core techniques are briefly outlined below (more information about these procedures can be found at All of these operations are day-case procedures. Excimer laser techniques require patient co-operation during surgery and are always performed under local anaesthetic. Implant based procedures can be performed safely under either local or general anaesthetic. LASIK (Laser in situ keratomileusis) range +4D to 10D with up to 6D astigmatism (figure 1). LASIK involves wavefront (aberrometry) guided excimer laser corneal reshaping ( beneath a protective corneal flap which is replaced at the end of surgery. This protective flap is now most commonly formed using a femtosecond laser ( Because surface tissue damage is minimised in LASIK, visual recovery is rapid and virtually pain free. < Figure 1 A schematic section through the eye illustrating LASIK in LASIK excimer laser reshaping of the cornea takes place beneath a thin superficial flap which is replaced at the end of the procedure CONFUSED ABOUT REQUIREMENTS? IMPORTANT INFORMATION Under the new Vantage rules, all OT points awarded will be uploaded to its website by us. All participants must confirm these results on so that they can move their points from the Pending Points record into their Final points record. Full instructions on how to do this are available on their website.

2 BLUE JULY 25.qxd: 7/8/08 09:34 Page 31 This issue : Free Worth 2 standard points Surface laser refractive surgery (PRK - Photorefractive keratectomy, LASEK - laser assisted sub-epithelial keratectomy and EpiLASIK) range +4D to 10D with up to 6D astigmatism. < Figure 2 A schematic section through the eye illustrating surface laser treatment in surface laser treatments the corneal epithelium is removed prior to excimer laser reshaping at the surface of Bowman's membrane Surface laser treatments are based on wavefront guided excimer laser reshaping of the cornea immediately beneath the surface skin layer (the corneal epithelium), which is removed prior to surgery and regenerates in the week after (figure 2). Variations in surface laser treatment (PRK and variants such as EpiLASIK, LASEK) use different techniques for removing the corneal epithelium, but produce similar results. Recovery time is longer for surface laser treatments, but they have safety advantages for patients with relatively thin corneas. Although recovery time is slower, final results for LASIK and surface treatments are similar. < Figure 3 A schematic section through the eye illustrating intraocular lens implantation in refractive lens exchange an operation identical to modern cataract surgery RLE (Refractive Lens Exchange) range: myopia/hypermetropia at any level with up to 3D of astigmatism can be treated with RLE. RLE is identical to modern cataract surgery; but the surgery is performed to correct refractive errors in patients who do not have a cataract. The operation involves replacement of the natural lens with an intraocular lens (IOL) delivered through a self-sealing micro incision which does not affect eye wall strength (figure 3). Incisional techniques or specialised toric IOLs can be used in tandem with RLE to reduce astigmatism, and multifocal IOLs ( can be implanted to reduce spectacle dependence for near vision. The IOL is implanted within the capsule of the natural lens which shrink-wraps the implant and stabilises it in the natural position as part of the healing process in the months after surgery. The lens capsule often loses transparency during this healing process and RLE (as with cataract surgery) is often followed up with a minor laser procedure YAG laser capsulotomy to restore clarity. ICL (Intraocular Collamer Lens) implantation range: up to 17D myopia with up to 5D astigmatism; up to +10D hypermetropia. ICL surgery is based on implantation of a soft flexible artificial lens which is seated just in front of the natural lens and behind the iris ( (figure 4). Unlike RLE, natural accommodation is preserved. So this approach is particularly suited to younger patients who are out of range for laser refractive < Figure 4 A schematic section through the eye illustrating ICL implantation the ICL is a soft injectable lens which vaults over the natural lens behind the iris to correct refractive errors surgery. Toric ICLs are particularly effective in treating combined myopia and astigmatism. Hyperopic toric ICLs and multifocal ICLs are not yet available. ICL implantation is contraindicated in patients with a shallow anterior chamber. ICL implants are generally implanted 31 25/07/08 Low myopia Moderate myopia High myopia Low hypermetropia High hypermetropia Range to to > to Above years LASIK/PRK LASIK ICL LASIK ICL/RLE years LASIK/PRK LASIK ICL/RLE LASIK/RLE RLE Over 60 years RLE RLE RLE RLE RLE < Table 1 An approximate guide to refractive surgery procedure selection

3 BLUE JULY 25.qxd: 7/8/08 09:34 Page 32 This issue : Free Worth 2 standard points 32 25/07/08 < Figure 5a A femtosectond LASIK flap is seen just after completion of the raster pattern. A layer of minute gas bubbles is visible just beneath the corneal surface in patients under 50 years of age. Many patients over 60 are better suited to lens exchange (RLE) than laser refractive surgery, particularly if the early signs of cataract are present. The summary table (page 31) is designed as a rough guide to procedure selection; but the age and refractive range cut offs given for each technique are not absolute. Bioptics For patients with very high starting levels of myopia (over D), a staged approach in which ICL implantation is followed up with LASIK one month later is commonly used. This two stage approach is often referred to as bioptics. A similar approach is often used to deal with high levels of astigmatism or unplanned residual refractive errors after RLE. Risk assessment Each of the procedures outlined above has a background level of risk. The initial aim of a refractive surgery consultation is to highlight areas of added risk for individual patients. These may be modifiable factors, such as treatable ocular surface problems, or non-reversible areas of added risk which will influence procedure choice and subsequent counselling. < Figure 5b A femtoecond LASIK flap after lifting by dissection with a fine, blunt spatula. The laser creates an easy plane for dissection with a high level of dimensional reproducibility An algorithmic approach to refractive surgery assessment, as summarised here, works up to a point; but risks leaving patients with unrelated eye health problems undiagnosed. Examples include glaucoma, ocular signs of systemic hypertension, diabetes, hyperlipidemia, ocular tumours and papilloedema. Refractive surgery is real medicine and not a production line. Comprehensive, expert assessment and continuity of care are required alongside state-of-the-art equipment and good technical back-up to achieve the best results. Most refractive surgery consultations include the following elements: aberrometry, corneal topography and pachymetric assessment, manifest refraction, history and slit lamp examination. Information from these tests is used to determine the least risk procedure. Aberrometry (wavefront scanning) is normally performed at the start of the consultation to minimise any disturbance to tear film stability prior to testing. Forced choice testing is useful where significant differences in manifest and aberrometry based refractions are observed, and a cycloplegic refraction is a worthwhile check wherever incomplete relaxation of accommodation is suspected (especially in younger hyperopic patients and in mixed astigmatism). Wavefront guided treatments are commonly modified by the surgeon prior to treatment delivery to take account of inaccuracies introduced by accommodation, chromatic aberration and other factors. High quality optometric input is very helpful in guiding these physician adjustments. The starting point in selecting the safest procedure is a ranking of procedures in terms of their background risk. Debate exists about the order, but most UK surgeons prefer LASIK to surface treatment where LASIK is not contraindicated (LASIK may be safer and certainly gives a faster recovery) 1. Laser procedures are preferred to implant-based procedures (there is virtually no risk of total visual loss in an extraocular procedure), and ICL implants are preferred to RLE (natural accommodation is preserved by ICL implantation and the operation is reversible). Counselling LASIK patients Wavefront guided LASIK is the default procedure in modern refractive surgery for a good reason: it is safe and highly effective. Contemporary wavefront guided laser systems include sophisticated eye tracking systems which help to ensure that the ablation pattern (the pattern of laser pulses that reshapes the cornea) is accurately superimposed on the optical map of the eye acquired during wavefront scanning (figures 5a and b). Systematic errors are ironed out with nomogram adjustments, and surgical strategies have evolved to maximise consistency between cases. Over 90% of patients with lower preoperative levels of myopia (up to 6D with up to 3D astigmatism) have an uncorrected vision of 6/6 or better after one treatment with most contemporary wavefront guided systems ( Higher treatments and hyperopic treatments are less accurate, with approximately 75% of patients achieving an uncorrected vision of 6/6 or better. Enhancement treatments are straightforward, low risk, and highly effective in treating residual refractive errors. The net result is that LASIK patients starting with a pre-operative BCVA of 6/6 or better can be confident of achieving the same level of

4 BLUE JULY 25.qxd: 7/8/08 09:34 Page 33 This issue : Free Worth 2 standard points uncorrected distance vision as a normal non-spectacle wearer. The best qualitative approximation of what patients can expect from their vision post-lasik is what they can see in soft contact lenses. Most post- LASIK patients (and most nonspectacle wearers) do not have zero refractive error; and it is important to emphasise that some sharpness may be lost. This is particularly important for rigid contact lens wearers. Spectacle dependence for low level residual refractive errors is rare in the pre-presbyopic group however. But younger patients need to know that spectacle dependence for reading is normal in later life. Monovision is the main compromise for distance vision in older patients, the majority of whom gain considerable functional freedom for near work with a low reserve of myopia (-1.00 to -1.50D) in one eye 2. These patients need to know that this undercorrection may be noticeable in mesopic conditions. Classic examples of situations where a distance spectacle correction may be preferred include night driving, theatre and cinema. Many patients in whom monovision is targeted manage well without any distance correction, but typically prefer glasses for reading fine print more as they move into their 50s. Monovision relies on binocular blur suppression and works well for most patients who do not have a strong ocular dominance. The convention is to correct the dominant eye for distance vision. A variety of tests of ocular dominance is available, but pre-operative best corrected visual acuity (BCVA) is probably the most useful guide. Monovision appears to be well tolerated with either eye corrected for the distance if patients are codominant (equal pre-operative BCVA) 2. In these circumstances, handedness is a good guide to the choice of distance eye some activities such as shooting only work if the correction is this way round. Conversely, where pre-operative BCVA is not equal, care is required even though the choice of distance eye would appear obvious. Subtle amblyopia is common, particularly amongst hypermetropic patients, and monovision does not work well if one eye is dominant. A trial in contact lenses is useful prior to surgery in this group. Evidence on post-treatment refractive stability after LASIK is incomplete; but late enhancement treatments are unusual 3. Repeat treatment is possible, if required, even many years after the original procedure provided that an adequate reserve of untreated corneal tissue remains. LASIK is not a cosmetic procedure. Like contact lenses, the motivation for surgery is functional: spectacles look great but when did you last see a professional footballer wearing them? LASIK is not risk free; but neither is contact lens wear and the most sensible approach to evaluating risk in LASIK counselling is to balance the risk of visual loss against the low, but cumulative risk of continuing to wear contact lenses 4. Contemporary (as yet unpublished) epidemiological studies suggest that approximately 1 in 2,500 wearers of the best performing daily disposable contact lenses can expect to develop microbial keratitis each year. 10% of these infections result in serious visual loss (BCVA less than the driving standard). The risk of serious visual loss from all possible causes after LASIK is difficult to estimate, but is almost certainly less than 1/2,500 where modern femtosecond lasers are used to create a homogeneous, thin (<120 micron) flap reliably. LASIK is probably safer than a decade of contact lens wear. It is certainly safer than a shorter period of overnight contact lens wear overnight wear of any lens including silicone hydrogel lenses has recently been associated with a 7x increase in the risk of microbial keratitis. LASIK is not painful, and almost all patients now prefer to have both eyes treated at one surgical session. Patients can expect 4-6 hours of relatively blurred vision ( like looking through a watery fog ) and mild postoperative discomfort ( like wearing a contact lens for too long ) after treatment. By the next day, vision is typically at the driving standard or better, and most patients can return to work. Variable vision associated with tear film instability is common in the first few days, but settles quickly. Patients commonly have unsightly subconjunctival haemorrhages. These resolve over two to three weeks and are of no functional significance. Common early postoperative side effects include light scatter symptoms (glare, starbursts and haloes whilst night driving) and dry eye symptoms. Whilst night vision problems are common in the early period after LASIK especially after treatment of high prescriptions long-term difficulties are rare and most of the scare stories that still resonate are a hangover from the days of surface treatments with small optical zones when laser refractive surgery was in its infancy. The technology has moved on, results have improved and most patients undergoing wavefront guided LASIK treatment report improved night vision (compared to pre-operative questionnaire responses) once surface tissue remodelling is complete by a year after treatment. Any postoperative light scatter symptoms typically resolve within three months. The corneal sensory nerves in the flap area are cut during LASIK, and have to regenerate to provide a normal stimulus to tear production and a normal blink rate. Functional regeneration takes six to 12 months. Dry eye symptoms are common in the early period after LASIK, but rarely persist. Occasionally, lacrimal punctal occlusion is helpful. However, most patients simply require tear supplements during activities classically associated with dry eye symptoms (prolonged computer use, long haul flights, etc). Many contact lens wearers are told, incorrectly, that they have dry eyes (low grade contact lens intolerance produces surface discomfort and dry eye symptoms) and consider themselves to be unsuitable for LASIK. Younger patients with a good marginal strip tear volume and normal meibomian anatomy are usually symptom free after LASIK /07/08

5 BLUE JULY 25.qxd: 7/8/08 09:34 Page 34 This issue : Free Worth 2 standard points 34 25/07/08 < Figure 6a An intraocular collamer lens (ICL) during injection < Figure 6b Intraocular collamer lens (ICL) implantation at completion of surgery. The appearance of the eye is unchanged Older female patients with evidence of meibomian dysfunction are more likely to be symptomatic, and work on optimising the ocular surface prior to treatment is particularly helpful in this group. When is PRK preferred to LASIK Improved patient selection strategies, improved technology, and improved strategies for treating complications have combined to make contemporary LASIK very safe. But surface treatments (PRK, LASEK or EpiLASIK) are still preferred in patients with relatively thin corneas, patients with corneal epithelial instability problems, and in some occupational groups. There is a limit to the amount of corneal tissue that can be removed without increasing the risk of keratectasia (iatrogenic keratoconus). The precise limit is unknown, but a calculated residual stromal bed (RSB) of untreated corneal tissue of less than 250 microns is the widely accepted cut-off point 5. Most surgeons aim to leave at least 270 microns to take account of possible variations in flap cut depth and allow room for an enhancement treatment if necessary. The RSB is calculated by subtracting the flap thickness plus predicted ablation depth from pre-operative corneal thickness measured by ultrasound pachymetry. The advent of thin-flap LASIK (also referred to as sub-bowman s layer keratectomy or SBK) has considerably reduced the pool of patients in whom surface treatments are preferred. Phototherapeutic keratectomy is a useful treatment for epithelial basement membrane dystrophies and recurrent erosion syndrome. By extension, many surgeons prefer surface treatments in patients with epithelial instability problems. Surface treatments have been preferred for some groups in the armed forces and patients involved in contact sports. However, large scale studies in US Army personnel 6 indicate that the risk of flap dislocation drops to less than 1 in 1,000 by one month after treatment and that significant trauma (ie an injury that would damage an unoperated cornea) is required. Accordingly, occupational limitations on LASIK are being relaxed. Surface treatments would still normally be preferred in boxers and martial arts enthusiasts. The final results of wavefront guided surface laser treatments and LASIK are similar, but recovery after surface

6 BLUE JULY 25.qxd: 7/8/08 09:34 Page 35 This issue : Free Worth 2 standard points treatments is slower. Approximately five days of discomfort and photophobia are normal after surface laser treatments, and it can take up to one month before comfortable driving and working vision are restored. Parity with the LASIK recovery trajectory is usually achieved within three months. Dry eye and night vision symptoms are common but, as with wavefront guided LASIK, these symptoms can be expected to resolve within a few months of treatment. Relative contraindications to laser refractive surgery There are few absolute contraindications to laser refractive surgery, but it makes sense to switch to an implant based technique where areas of added risk for laser treatment exist. Relative contraindications are listed below. Amblyopia or pre-existing visual loss in one eye Clearly patients with only one good eye need to consider the risks of any elective ocular surgical intervention with particular care, but laser refractive surgery is now sufficiently safe that most surgeons no longer regard uniocular status as an absolute contraindication to treatment. Topographic signs of keratoconus Pre-clinical or forme fruste keratoconus (FFKC) is a well identified risk factor for keratectasia after LASIK 5. Pretreatment topographic studies are designed to detect patients with FFKC. A set of topographic criteria for diagnosing keratoconus at an early stage has evolved from studies of clinically normal fellow eyes of patients with apparent unilateral keratoconus. Steep central keratometry readings (>47D), superior/inferior keratometric asymmetry (>1.5D), skewed radial axes, and asymmetric or off centre thinning are all signs that might suggest keratoconus. But none of these findings, in isolation, is sufficient to indicate any significant added risk a steep corneal shape is common in myopia and higher refractive errors are associated with higher levels of corneal asymmetry (coma). The Pentacam ( an instrument that builds up an accurate picture of corneal shape and thickness through a series of optical sections, includes a useful automated detection algorithm for FFKC. Other non-automated scoring systems have been developed to exclude LASIK treatment in vulnerable patients. None of these systems is infallible. Where doubt exists, some surgeons opt for a surface treatment. But keratectasia has been reported after PRK. So ICL implantation may be a safer alternative. Ocular surface problems Many common ocular surface problems (eg blepharitis, allergic conjunctivitis) can be controlled so as to minimise additional risk in the perioperative period. For nonreversible eye surface problems (eg dry eyes) implant based procedures are often preferred. A shallow anterior chamber in hypermetropia Hypermetropia is commonly associated with a relatively shallow anterior chamber angle, and an elevated risk of angle closure glaucoma. Optical coherence tomography based anterior chamber imaging systems can be used to map the anterior chamber angle configuration accurately and add precision to the estimation of risk for patients with relatively shallow anterior chambers. Where doubt exists, it makes sense to opt for RLE which is highly effective in correcting hypermetropia and deepens the anterior chamber removing any risk of acute angle closure glaucoma. A steep corneal shape in hypermetropia or a flat shape in myopia Laser corneal reshaping effectively aims to add the spherical equivalent dioptric correction to the average central keratometry. Optical results in hypermetropic correction tend to be better if the final corneal shape is within the physiological range (average central keratometry <48D). For patients starting with steep central keratometry, RLE is probably the best option. There is less concern about a flat starting shape in myopia, but some surgeons prefer to avoid a final average central keratometry less than 35D. Cataract Cataract surgery is a good treatment for myopia so why do LASIK or PRK on someone with cataracts? Symptomatic cataract is a clear contraindication to laser refractive surgery; but nonprogressive congenital lens opacities are common, and often cause no significant visual degradation. As a rule of thumb, patients with progressive myopia (and evidence of a nucleosclerotic lens opacity) or glare symptoms should have cataract surgery. It is probably reasonable to proceed with LASIK in the rest. Good nomograms now exist to modify IOL selection in cataract surgery post-lasik, and enhancement laser treatments, where necessary to adjust the refractive outcome, are usually possible. So the future cataract surgery is complicated by previous LASIK dogma is now largely redundant. Glaucoma As with post-lasik biometry, pachymetry based nomogram corrections to applanation tonomometric intraocular pressure measurements are now routine; and changes in corneal compliance after laser refractive surgery are unlikely to lead to clinically significant inaccuracy. Transient intraocular pressure increases during surgery do not appear to lead to disease progression in glaucomatous optic neuropathy. Accordingly, most patients with glaucoma can be treated safely. Herpes simplex keratitis Post-infective corneal scarring is not generally a contraindication to laser refractive surgery, and peripheral scars have little impact on the visual result. However, many surgeons prescribe prophylactic oral antiherpetic treatment for at least three months after laser refractive surgery in cases of quiescent herpes simplex keratitis /07/08

7 BLUE JULY 25.qxd: 7/8/08 09:34 Page 36 This issue : Free Worth 2 standard points 36 25/07/08 < Figure 7a An intraocular lens (IOL) folded for implantation prior to release into the lens capsular bag. Here, forceps insertion is seen. A variety of injection systems similar to that shown in fig 2a are also used for injecting IOLs in refractive lens exchange and cataract surgery < Figure 7b An intraocular lens (IOL) after unfolding within the capsular bag during refractive lens exchange Previous corneal surgery Enhancement LASIK treatment after previous radial keratotomy normally works well, but the presence of epithelial plugs in keratotomy incisions can be associated with button hole formation during flap lifting. LASIK flap complications are also more common in steep or irregular post-transplantation corneas. Surface laser treatments avoid flap problems, but are associated with increased haze and regression problems in this group, especially where higher corrections are required. So ICL implantation with topographically guided surface excimer laser refinement is becoming the preferred contemporary paradigm in post transplantation ametropia. Pregnancy Hormonal changes in pregnancy are associated with refractive instability, and refractive surgery would not normally be performed in women who are pregnant or breast feeding. General health problems An array of health problems including diabetes and immunodeficiency syndromes were listed as contraindications in earlier clinical safety trials in refractive surgery. It is probably discriminatory to propagate a policy of blanket exclusion for all patients in these groups. Patients with wellcontrolled diabetes, for example, with normal corneal sensation and no history of recurrent erosion syndrome, are probably not at increased risk. Similarly, HIV positive patients with a normal CD4 cell count, probably have little or no increased risk of intraocular infection. A more rational approach is to exercise caution where general health problems might influence wound healing or the risk of infection. Counselling in intraocular collamer lens (ICL) implantation In addition to being the procedure of choice for pre and early postpresbyopic patients with high refractive errors, ICLs are a very good alternative for many patients who are excluded from laser refractive surgery by corneal or ocular surface problems (figures 6a and b). Patients can have surgery under local or general anaesthetic. As with other implant-based procedures, considerable debate still exists about the safety of same-day bilateral surgery. The conservative and currently prevailing view in the UK is that sequential surgery, with the second eye surgery a minimum of one week after surgery in the first eye, is safer. ICLs and the toric ICL (TCL) in particular, are highly effective in providing accurate refractive correction. 83% of eyes treated in a recent FDA trial (average preoperative spherical equivalent -9.5D; average preoperative cylinder -2D) were able to see 6/6 or better unaided (97% 6/9 or better) 7. Substantial visual rehabilitation is achieved within two days of surgery, there is little postoperative discomfort, and patients can return to work within a week of surgery on the second eye. Light scatter symptoms in mesopic conditions are a common symptom after ICL surgery; but they are usually mild, improve with time, and often no worse than preoperative light scatter symptoms in contact lens wearers with a high refractive error. These symptoms rarely diminish satisfaction with surgery. Unlike laser refractive surgery, ICL surgery can be reversed, but this is rarely requested. ICLs are probably safer than other phakic intraocular lenses. Iris clip lenses were abandoned in cataract surgery in the 1980s because of their association with corneal endothelial failure, and no angle supported phakic IOL has received FDA approval or stayed on the market for any length of time. Cataract is the most common complication of ICL surgery, occurring in approximately 2% of cases. ICLs are easy to remove through a conventional cataract incision, and patients are left, effectively, with refractive lens exchange (RLE): their refractive error remains corrected. Big advantages for ICL implantation over RLE are a) preservation of natural accommodation and b) no increased risk of retinal detachment in the high myopic group. Counselling in refractive lens exchange (RLE) Cataract surgery is the most common elective operation of any type performed worldwide. Outcomes are highly predictable and good strategies exist for treating most complications. Where laser refractive surgery and ICL implantation are not appropriate; refractive lens exchange is often a very good option (figures 7a and b). It works particularly well for hypermetropic patients in the postpresbyopic age group. These patients have no increased risk for retinal detachment, and often have an

8 BLUE JULY 25.qxd: 7/8/08 09:34 Page 37 This issue : Free Worth 2 standard points anterior chamber depth that is below the minimum recommended for ICL implantation (internal anterior chamber depth <2.8mm). RLE in this group removes any future risk of angle closure glaucoma, and should be considered in preference to prophylactic peripheral iridotomies which offer no gain in visual function. In approximate round numbers, cataract surgery is associated with a 1 in 1,000 risk of permanent visual loss, a 1 in 100 risk of needing a second surgical intervention and a 1 in 10 chance of needing a laser intervention. The main modifications to these figures appropriate to RLE relate to an increased risk of retinal detachment surgery after cataract surgery in high myopia and an increased likelihood of laser intervention either to correct a residual refractive error or to treat posterior capsule opacification. Approximately 1 in 20 highly myopic patients (>-10D) per decade will develop a retinal detachment. This risk is doubled by RLE 8. More than 9 out of 10 retinal detachments are repaired successfully at the first attempt, but this still translates roughly into a 1% risk of visual loss for highly myopic patients in the decade after RLE (vs 0.5% without surgery). Regardless of whether they elect to proceed with refractive surgery, it is important to rehearse the symptoms of retinal detachment (flashes, floaters, field loss) with high myopes and ensure that they are aware of the need to attend for ophthalmic examination without delay if they experience these visual changes. Laser intervention is more common after RLE than cataract surgery. The wound healing reaction to IOL implantation, and therefore posterior capsular opacification, is unregulated in younger patients. YAG capsulotomy rates may be as high as 1 in 3 after RLE, depending on the IOL used. Also, since the primary aim is spectacle independence, RLE patients tend to be more sensitive to any residual refractive error, and more likely to request excimer laser enhancement procedures. Laser refractive enhancements are particularly prevalent amongst multifocal IOL recipients. A sharp distance focus is required for the best function with multifocal IOLs, and up to 1 in 5 recipients opt for laser enhancement. Optical side effects (haloes/glare) associated with multifocal IOL implantation are reduced in modern, diffractive designs incorporating optical features such as asphericity and apodization, and multifocal implantation is an increasingly popular choice 9. Diffractive designs are really bifocal rather than multifocal, and an intermediate distance correction (+1.00DS approx.) is preferred by patients in some occupational groups particularly those for whom screen work or reading music is important. Mix and match strategies (diffractive multifocal IOL in one eye, refractive in the other) are currently being explored to provide better intermediate vision. Multifocal IOLs can be exchanged for monofocal lenses in patients with intolerable light scatter symptoms. This can be technically difficult and is not risk free. Potential multifocal recipients need to be counselled carefully about the risk of light scatter symptoms after surgery, and should consider monovision as an alternative. Despite these limitations, multifocal IOLs offer real functional advantages over bilateral monofocal implantation targeting good unaided distance vision only. Up to 80% of multifocal IOL recipients are completely spectacle free after surgery, and light scatter symptoms are usually mild. Less than 1% of patients request reversal after implantation. After refractive surgery Although many patients are spectacle-independent after refractive surgery, continued optometric review is useful both to screen for late complications particularly after implant based refractive procedures and common unrelated eye health problems. Annual optometric review is probably not necessary after laser correction in the pre-presbyopic age group, but is recommended for all implant recipients and patients with a family history of glaucoma. Conclusion Good options for refractive surgery are available for patients of all ages with most refractive errors. A knowledge of the options available and a balanced view of the associated risks is integral to modern optometric practice. About the author Bruce Allan MD FRCS FRCOphth is a consultant ophthalmic surgeon at Moorefields Eye Hospital. He specialises in refractive surgery, cataract surgery and corneal transplantation. References 1. Shortt AJ, Bunce C, Allan BD. Evidence for superior efficacy and safety of LASIK over photorefractive keratectomy for correction of myopia. Ophthalmology 2006;113(11): Braun EH, Lee J, Steinert RF. Monovision in LASIK. Ophthalmology Kato N, Toda I, Hori-Komai Y, et al. Five- Year Outcome of LASIK for Myopia. Ophthalmology Mathers WD, Fraunfelder FW, Rich LF. Risk of Lasik surgery vs contact lenses. Arch Ophthalmol 2006;124(10): Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology 2008;115(1): Hammond MD, Madigan WP, Jr., Bower KS. Refractive surgery in the United States Army, Ophthalmology 2005;112(2): Sanders DR, Schneider D, Martin R, et al. Toric Implantable Collamer Lens for moderate to high myopic astigmatism. Ophthalmology 2007;114(1): Alio JL, Ruiz-Moreno JM, Shabayek MH, et al. The risk of retinal detachment in high myopia after small incision coaxial phacoemulsification. Am J Ophthalmol 2007;144(1): Artigas JM, Menezo JL, Peris C, et al. Image quality with multifocal intraocular lenses and the effect of pupil size: comparison of refractive and hybrid refractive-diffractive designs. J Cataract Refract Surg 2007;33(12): /07/08

9 BLUE JULY 25.qxd: 7/8/08 09:34 Page 38 This issue : Free Worth 2 standard points Module questions Course code: c-8160 Please note, there is only one correct answer. Enter online or by form provided An answer return form is included in this issue. It should be completed and returned to initiatives (c-8160) OT, Ten Alps plc, 9 Savoy Street, London WC2E 7HR by August /07/08 1. In the two years prior to refractive surgery, the spectacle prescription should only have changed by a maximum of: a. 0.50D b. 1.00D c. 1.50D d. 2.00D 2. Approximately what proportion of patients with low preoperative levels of myopia (up to 6D with up to 3D astigmatism) have an uncorrected visual acuity of 6/6 or better after one treatment with most contemporary wavefront guided systems? a. 50% b. 60% c. 70% d. 90% 7. Which one of the following treatment strategies is most likely to be appropriate for a 25 year old +2D hypermetrope who does not routinely wear spectacles? a. PRK b. LASIK c. conductive keratoplasty d. reconsider surgery later in life once the patient has become more spectacle dependent 8. Keratoconus is not normally suspected in patients with: a. thin corneas b. high levels of coma c. average central K values >47D d. flat corneas 3. Monovision after refractive surgery is generally well tolerated in patients with: a. equal pre-operative best spectacle corrected acuities b. a strong ocular dominance c. macular disease d. amblyopia 4. Intraocular collamer lens implantation is contraindicated in patients with: a. -10D of myopia b. 3D of astigmatism c. +7D of hypermetropia d. a shallow anterior chamber 5. Cataract surgery is normally preferred to LASIK in patients with: a. a lens opacity but no visual symptoms b. a lens opacity and light scatter symptoms c. age greater than 45 years d. age under 45 years 6. Refractive lens exchange is often recommended for low myopes aged: a years of age b years of age c years of age d. over 60 years of age 9. Which one of the following is incorrect regarding ICL implantation? a. ICLs are a good alternative for patients with corneal or surface problems b. patients can have surgery under local or general anaesthetic c. light scatter symptoms in mesopic conditions are rare after ICL surgery d. ICL surgery can be reversed 10. Refractive surgery is not normally performed in patients: a. over 45 years of age b. over 60 years of age c. over 75 years of age d. under 18 years of age 11. Problems with multifocal lens implants in refractive lens exchange may include all of the following except: a. glare symptoms b. relatively poor intermediate vision c. haloes d. closed angle glaucoma 12. Common side effects of LASIK include all of the following except: a. mild dry eye symptoms in the early postoperative period b. light scatter at night in the early post operative period c. subconjunctival haemorrhages d. cataract Please complete on-line by midnight on August You will be unable to submit exams after this date answers to the module will be published in our September 5 issue

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12 BLUE JULY 25.qxd: 7/8/08 09:34 Page 41 This issue : Free Worth 2 standard points 41 27/06/08