Refractive lens exchange for high myopia: case report

Transcription

1 Optometry in Practice 2013 Volume 14 Issue Refractive lens exchange for high myopia: case report Oliver Bowen-Thomas BSc(Hons), Michael Jeffrey MB ChB DO FRCS(Ed) FRCOphth and Clare O Donnell BSc(Hons) PhD MBA MCOptom FAAO FBCLA Optegra Eye Sciences, Optegra Manchester Eye Hospital EV C CET point for UK optometrists A 41-year-old male attended for a consultation for refractive surgery following referral from his optician. He wanted to know if anything could be done for his prescription. He was informed by his optician that there were surgical options available to treat his prescription; however, even after surgery he may still need spectacles for certain tasks. The patient was still keen. He had always found his spectacles to be heavy and uncomfortable and wanted to be able to have more freedom to manage without them. He had tried contact lenses but found them difficult to apply and he had ultimately decided to stop wearing them. myopic degenerative changes in the periphery and the retinas were flat. Ocular examination, including anterior-segment topography (Figure 1), was otherwise unremarkable. Previous ocular history revealed that he had started to wear spectacles for myopia at the age of 4 years. He always found lights at night difficult and reported being troubled by glare, starbursts and haloes around lights. This had not stopped him from driving. His occupation was to manage airline stock. He reported being seen in the hospital eye service many years previously after experiencing retinal bleeds in both eyes. Details were unavailable, but this had resulted in minor retinal scarring and he was subsequently discharged. Progressive elongation of the globe is often accompanied by degenerative changes in high myopia. Complications of high myopia can include breaks in Bruch s membrane, haemorrhage, choroidal neovascularisation and secondary pigmentary proliferation in the form of a Fuchs spot. Other complications include posterior staphylomas, macular holes, peripheral retinal holes, cataract, increased prevalence of glaucoma and corticosteroid responsiveness (Kanski 1989; Saw et al. 2005; Silva 2012). Other family members had myopia, although not to the same degree. The patient mentioned that he was taking ramipril for systemic hypertension but was in good health. Examination revealed: Rx details: R DS 6/5 L / /7.5 Intraocular pressure (IOP) (non-contact tonometer): R 20mmHg L 20mmHg Ocular examination showed relatively clear media and bilateral posterior vitreous detachments (PVDs) with no pigment visible in the vitreous. There was evidence of Figure 1. OCULUS Pentacam scans for the right (top) and left eye (bottom). Refractive surgical options that are available to myopes in their 40s include laser vision correction, phakic intraocular lenses (IOLs) and refractive lens exchange. Laser vision correction is well established, although it continues to evolve, with new approaches being introduced periodically. Energy from an excimer laser is typically used to reshape the cornea Date of acceptance: 1 November Address for correspondence: Dr C O Donnell, Optegra Manchester Eye Hospital, One Didsbury Point, 2 The Avenue, Didsbury, Manchester M20 2EY, UK. Clare.odonnell@optegra.com The College of Optometrists 155

2 O Bowen-Thomas et al. by vaporising away microns of tissue. Wavefront-guided laser technology minimises higher-order aberrations induced by the surgery (Smadja et al. 2012). Over 28 million laser vision correction procedures have been performed worldwide (Stuart 2009) and there are now a number of different options available. The most common techniques include laser-assisted in situ keratomileusis (LASIK) and surface procedures such as photorefractive keratectomy (PRK) and laser-assisted subepithelial keratomileusis (LASEK). LASIK is where a flap in the cornea is created using a femtosecond laser (that generates small gas bubbles to photodisrupt the tissue) or a mechanical microkeratome. The flap is folded back so that an excimer laser can be used to reshape the cornea. The flap is then folded back into its original position. The operation can be carried out in both eyes in approximately 15 minutes and the initial recovery period takes place within a matter of hours. With PRK, the epithelium is removed and then an excimer laser is applied directly to the cornea. The laser removes microscopic portions of tissue from the cornea, altering its shape. It takes around minutes to treat both eyes. LASEK is more commonly performed than PRK. The surface epithelium is loosened using an alcohol preparation and then lifted and moved to one side. After the excimer laser has been employed, the epithelium is then repositioned and a bandage contact lens placed over the top for 3 4 days to facilitate epithelial recovery. It takes minutes for the procedure. Vision is typically stable within a month. As with PRK, LASEK may be safer than LASIK if the cornea is relatively thin, there is marginal dry eye or the patient plays contact sports, where there is a risk of injury after treatment (Dastjerdi and Soong 2002). The range of treatment for laser vision correction is typically around 1.00DS to 9.00DS for myopia (although higher degrees can be treated) and +1.00DS to +6.00DS for hyperopia and up to 6.00DC of astigmatism. More recent approaches to laser vision correction include refractive lenticule extraction, where a femtosecond laser is used to create an intrastromal lenticule in the cornea that can then be removed through a small incision to create the refractive change (Kamiya et al. 2013). Additionally, there are now laser vision correction algorithms available that can be applied to correct presbyopia (Alió et al. 2009). Phakic IOLs (PIOLs) may be a good option where there is a high degree of ametropia, the cornea is too thin for laser and the patient is too young to have refractive lens exchange, due to the inherent loss of accommodation. There are two types of lenses, anterior chamber and posterior chamber PIOLs, the former being the most common type. Anterior chamber PIOLs can be angle-supported or iris-fixated. They can cause IOP elevation, cataract and reduced corneal endothelial cell density and therefore patients will be followed up postoperatively for evaluations including using specular microscopy. Iris-fixated PIOLs are attached by claws to the mid peripheral iris and can be associated with pigment dispersion. Posterior chamber PIOLs are implanted in the space between the posterior surface of the iris and the anterior surface of the crystalline lens. They can be spherical or toric. They have increased vaulting to avoid contact with the crystalline lens. The main complication with the latter type of lens is a tendency to cause cataracts. The range of refractive errors treatable with PIOLs is large, although it varies somewhat depending on the lens type. The risks and benefits of PIOLs are well documented (Alió and Toffaha 2013). Refractive lens exchange involves small-incision phacoemulsification surgery, removal of the crystalline lens and implantation of an IOL within the capsular bag. The surgical procedure is therefore the same as cataract surgery but the reason for surgery is elective correction of ametropia and possibly presbyopia. The procedure is usually best suited to patients who are already presbyopic or are approaching presbyopia. IOLs can be monofocal (spherical, aspheric, toric), typically providing correction for distance, intermediate or close vision. Other options are accommodating IOLs designed to provide correction for distance and intermediate with some degree of social reading ability, or multifocal lenses designed to provide correction for distance, intermediate and near vision. The treating surgeon decides with individual patients which option is most likely to satisfy their requirements. The type of IOL chosen will be based on clinical measurements and observations as well as the occupational and lifestyle requirements of the patient. Depending on the lens type chosen, there is a risk of glare/haloes and dysphotopsia, particularly with some multifocal IOL designs. While surgery is generally successful, IOL surgery for myopia carries a higher risk of retinal detachment, particularly in younger patients and those with longer axial lengths (Alió 2011; Rosen 2008). The reported incidence after lens extraction in highly myopic patients varies, with some studies reporting incidences of % (Neuhann et al. 2008), whilst others have reported incidences of 8.1% (Colin et al. 1999). The longer the axial length of an eye, the greater the vitreoretinal stretching. Removing the crystalline lens can increase the risk of PVD, which is a risk factor for retinal breaks, which in turn can lead to retinal detachment. PVD may occur naturally, particularly in older eyes, and this may have a protective effect, in contrast to PVD that occurs because of lens surgery. In the present case ophthalmoscopy showed that the patient had natural PVD prior to surgery. The patient was fully informed about the risks and benefits of IOL surgery (including retinal detachment, cystoid macular oedema, posterior capsular opacification (PCO) and possible problems with night driving due to dysphotopsia) to ensure expectations could be managed to provide the best possible outcome. After consultation and detailed discussions of the risks and benefits of each option (including PIOLs and no intervention), the patient decided to proceed with refractive lens exchange with a multifocal IOL, motivated by a desire to achieve spectacle independence at distance and near. The Lentis MPlus MF30 IOL was chosen (Figure 2). This is a single-piece aspheric hydrophilic acrylic lens with a sector-shaped 156

3 Refractive lens exchange for high myopia: case report near-vision segment which is claimed by the manufacturer to have no image jump, a +3.00D addition at the lens plane and minimal loss of light levels. The IOL is based on the concept of rotational asymmetry in which two sectors (distance and near) are both on the optic axis. A recently published large retrospective case series has demonstrated that this IOL provides excellent distance and near unaided vision with high degrees of patient satisfaction (Venter et al. 2013). Axial length: R mm L mm Ks: R. K /7.81@139 K /7.77@49 L. K /7.92@170 K /7.79@80 IOL power chosen: R. 2.00D to give an expected refractive outcome 0.40D L. 2.00D to give an expected refractive outcome 0.37D Uncomplicated lens replacement surgery was carried out on the right eye first and surgery on the left eye was carried out 1 week later. Unaided vision in the right eye at 1 week after surgery was 6/7.5, N6. The patient attended follow-up after a further week. He reported that the left eye was slightly uncomfortable. IOP using Goldmann applanation tonometry was found to be R 35mmHg, L 45mmHg. The patient was started on pressure-reducing therapy (Diamox 4 day, Xalatan at night and Cosopt 2 day). Two days later, IOPs were R 15mmHg, L 20mmHg. Diamox was stopped. One week later the pressures were 10mmHg in both eyes. Unaided vision was R 6/9 N8, L 6/12 N8. Treatment was stopped. One week later IOPs were R 20mmHg, L 19mmHg. At 2 months after surgery, the findings were: RE Vision 6/15 N8 Rx +1.25/ /6 N5 LE Vision 6/15 N12.5 Rx +1.00DS 6/7.5 N5 Binoc 6/6, N5 Figure 2. Plate haptic Lentis MPlus MF30 multifocal intraocular lens. (Image supplied by Oculentis, distributed by Topcon Surgical GB.) Biometry was performed using the Zeiss IOL Master to determine the IOL power. The measurements included axial length (measured from the precorneal tear film to the pigment epithelium of the retina), keratometry, anterior chamber depth (measured from the corneal epithelium to the anterior surface of the crystalline lens) and horizontal white-to-white width (corneal diameter). There are different formulae used by the IOL Master to calculate the IOL power required to achieve the desired refractive outcome. However, the prediction of IOL power in very long eyes can be more variable (Zaldivar et al. 2000). The surgeon can select a relevant formula depending on the length of the eye. Examples of commonly used formulae are HofferQ (for eyes <22.0mm), Holladay (for eyes mm) and SRK/T (for eyes >26mm). There are others available and they are continually evaluated for accuracy. Each IOL has what is termed an A-constant value that is calculated using information such as the IOL material and design and where the IOL is expected to sit within the capsule. This value is fed into the appropriate formula. The surgeon then selects the available IOL power that provides a predicted postoperative refraction closest to the desired (target) refractive outcome. In view of the low degree of residual hyperopic correction and after discussion with the patient, almost 3 months after surgery bilateral LASEK enhancement was performed. At 4 months, findings were: RE Vision 6/7.5 N5 Rx 0.25DS 6/6 N5 LE Vision 6/6 N5 Rx Plano/ /6 N5 The patient was very pleased with the outcome. Approximately 22 months later he returned to the clinic after observing that vision in the right eye had deteriorated. Findings were: RE Vision 3/ / /7.5 LE Vision 6/ DS 6/7.5 A diagnosis of bilateral PCO was made. After discussions with the patient about the risks and benefits of treatment, bilateral Nd:YAG laser capsulotomy was performed. After 1 month findings were: RE Vision 6/ N4 Rx +0.25/ /6 N4 LE Vision 6/6 N4 Rx +0.50/ /6 N4 The patient remains delighted with the outcome, achieving binocular 6/6 and N4 uncorrected. 157

4 O Bowen-Thomas et al. Discussion This case demonstrates that refractive lens exchange can be an effective form of refractive surgery that may be considered in patients in whom other options such as laser vision correction may not be suitable. In this case, a good outcome was achieved with careful patient counselling, modern biometry techniques and appropriate lens selection. Some patients can have elevated IOP in response to the routinely prescribed topical steroids and steroid responders should be reviewed to ensure that IOP has returned to normal. The low hyperopic outcome that was obtained was managed successfully with laser vision correction. As the patient had been advised preoperatively that laser enhancement could be offered for further refinement, this possibility was not unexpected by the patient. As with any IOL implant, there is the possibility of developing PCO months or years after surgery. PCO results from the growth and abnormal proliferation of lens epithelial cells on the capsule at the time of surgery. The cells migrate to the posterior capsule over time, where they can impinge on the visual axis, causing reduced vision. The incidence of PCO has been reported to range from <5% to up to 50% in eyes undergoing cataract surgery. IOL design, optic size and edge and IOL material are important factors in the development of PCO (Raj et al. 2007). In the Nd:YAG laser capsulotomy procedure, a clear channel is created in the centre of the opacified posterior lens capsule. Risks of the procedure can include elevation in IOP, cystoid macular oedema and retinal detachment (Raj et al. 2007). Again, managing patient expectations is crucial in elective refractive surgery and the patient was counselled preoperatively on the possibility of developing PCO. As well as offering the convenience of not requiring spectacle correction for distance, near or intermediate tasks, surgery has avoided any future cataract issues. In this case it is possible that by removing the minification effect of the myopic spectacles, the IOL slightly improved the distance visual acuity in the left eye. This increase was not observed in the right eye, perhaps due to differences in lens positioning. The patient was not affected by troublesome glare or haloes. Modern IOL surgery is safe and predictable (Lundstrom et al. 2013). Smaller incision sizes, foldable IOLs and improved intraoperative procedures for stabilising the anterior chamber have reduced complications and provided better outcomes for patients. As the range of intraocular implants expands and surgical techniques continue to evolve, lens replacement surgery may increasingly become an attractive option for patients. The recent application of femtosecond lasers in IOL surgery is designed to create more precise surgical incisions, limbal relaxing incisions and anterior capsulotomies as well as having the capability to reduce the ultrasound energy used during lens surgery. This may further reduce the risk of complications, leading to even faster visual recovery for patients. Improving the precision of the capsulotomy may have an impact on visual outcomes, and a more regularly shaped capsulotomy may reduce IOL decentration and tilt. Therefore it is expected that, in future, this technology could result in even more predictable refractive and visual outcomes after IOL surgery (see Trikha et al for review). New IOL designs and laser vision correction technologies are coming to market that will extend the range of options available to patients wishing to explore surgical alternatives for management of refractive error. It is important that the optometrist, as the trusted eyecare provider, remains aware of these alternatives, so that patients can be given accurate, up-to-date information on their options when it is requested. Furthermore, the optometrist will continue to play an important role in carrying out eye examinations for many patients postoperatively and it is important that patients are counselled on the importance of ongoing eyecare as well as actions to be taken should they develop symptoms such as flashes and floaters. For the clinician, there are useful sources of information available, such as publications in journals, conference presentations and textbooks, and refractive surgeons will generally welcome into their clinics optometrists who express an interest in expanding their knowledge of this field for the benefit of patients. Summary It is clearly important for the optometrist, as the trusted eyecare provider, to remain informed about all forms of refractive correction, both surgical and non-surgical. A desire to be less dependent on spectacles and contact lenses is not confined to the under-40s or to those with low to moderate degrees of ametropia. Refractive lens exchange by small-incision phacoemulsification surgery can be an effective method of correcting patients with high myopia who are presbyopic or who are approaching presbyopia. However, these patients present a special case in view of an increased risk of retinal complications after intraocular lens surgery and careful counselling is required. In summary, optometrists providing eyecare for the general population must be able to advise patients on the range of options available for the management of refractive error: Understanding the different options available as well as the benefits and limitations of each Being prepared to treat each patient on a case-by-case basis, gaining an appreciation of each individual s unique expectations and needs Providing care and advice postoperatively when patients attend for ongoing eye examinations Considering referral back to the treating surgeon should the need arise 158

5 Refractive lens exchange for high myopia: case report References Alió JL (2011) Lens surgery (cataract and refractive lens exchange) and retinal detachment risk in myopes: still an issue? Br J Ophthalmol 95, Alió JL, Toffaha BT (2013) Refractive surgery with phakic intraocular lenses: an update. Int Ophthalmol Clin 53, Alió JL, Amparo F, Ortiz D et al. (2009) Corneal multifocality with excimer laser for presbyopia correction. Curr Opin Ophthalmol 20, Colin J, Robinet A, Cochener B (1999) Retinal detachment after clear lens extraction for high myopia. Ophthalmology 106, Dastjerdi MH, Soong HK (2002) LASEK (laser subepithelial keratomileusis). Curr Opin Ophthalmol 13, Kamiya K, Shimizu K, Igarashi A et al. (2013) Visual and refractive outcomes of femtosecond lenticule extraction and small-incision lenticule extraction for myopia. Am J Ophthalmol doi: pii: S (13) /j.ajo [Epub ahead of print] PMID: Kanski JJ (1989) Clinical Ophthalmology. A Systematic Approach, 2nd edn. Kent: Butterworths, p. 360 Lundstrom M, Barry P, Henry Y et al. (2013) Visual outcome of cataract surgery; Study from the European Registry of Quality Outcomes. J Cataract Refract Surg 39, Neuhann IM, Neuhann TF, Heimann H et al. (2008) Retinal detachment after phacoemulsification in high myopia: analysis of 2356 cases. J Cataract Refract Surg 34, Raj SM, Vasavada AR, Johar SR et al. (2007) Post-operative capsular opacification: A review. Int J Biomed Sci 3, Rosen ES (2008) Risk management in refractive lens exchange. J Cataract Refract Surg 34, CET multiple choice questions This article has been approved for one non-interactive point under the GOC s Enchanced CET Scheme. The reference and relevant competencies are stated at the head of the article. To gain your point visit the College s website and complete the multiple choice questions online. The deadline for completion is 31 October To enable readers to prepare for the quiz, below are the topics which the questions address. 1. Common refractive correction techniques for prepresbyopes 2. Most recent approach to laser vision correction 3. Indications for phakic intraocular lenses 4. Differences between cataract surgery and refractive lens exchange 5. Reduction in risk of retinal breaks in refractive lens exchange 6. Least likely complication of refractive lens exchange surgery CPD Exercise After reading this article can you identify areas in which your knowledge of refractive lens exchange for high myopia has been enhanced? How do you feel you can use this knowledge to offer better patient advice? Are there any areas you still feel you need to study and how might you do this? Which areas outlined in this article would you benefit from reading in more depth, and why? Saw SM, Gazzard G, Shih-Yen EC et al. (2005) Myopia and associated pathological complications. Ophthal Physiol Opt 25, Silva R (2012) Myopic maculopathy: a review. Ophthalmologica 228, Smadja D, Reggiani-Mello G, Santhiago MR et al. (2012) Wavefront ablation profiles in refractive surgery: description, results, and limitations. J Refract Surg 28, Stuart A (2009) A look at LASIK past, present and future. Eyenet Magazine. feature.cfm? Date of access 11 November 2013, pp Trikha S, Turnbull AMJ, Morris RJ et al. (2013) The journey to femtosecond laser-assisted cataract surgery: new beginnings or a false dawn? Eye 27, Venter JA, Pelouskova M, Collins BM et al. (2013) Visual outcomes and patient satisfaction in 9366 eyes using a refractive segmented multifocal intraocular lens. J Cataract Refract Surg 39, Zaldivar R, Shultz MC, Davidorf JM et al. (2000) Intraocular lens power calculations in patients with extreme myopia. J Cataract Refract Surg 26,

6 O Bowen-Thomas et al. Reflection 1. What impact has your learning had, or might it have, on: your patients or other service users (eg those who refer patients to you, members of staff whom you supervise)? yourself (improved knowledge, performance, confidence)? your colleagues? 2. How might you assess/measure this impact? To access CPD Information please click on the following link: college-optometrists.org/cpd 160