Safety Considerations for Phakic Iols Avoid Potential Problems by Paying Attention to These Points

Refractive Surgery Feature story

Safety Considerations for Phakic IOLs Avoid potential problems by paying attention to these points.

By Gwyn Samuel Williams, MRCS; and Mohammed Muhtaseb, FRCOphth

n the decades since their introduction in the 1950s, phakic IOLs have become a compelling option for the correction of refractive error. There are, however, potential problems that can result from electing a Iphakic IOL as part of a refractive solution. Consequently, various safety parameters have been devised to mini- mize risks. But before complications can be properly addressed, it is important to distinguish among the available phakic IOLs and differentiate those problems associated with each lens design.

TYPES OF PHAKIC IOL Initial phakic IOL designs were angle-fixated lenses Figure 1. The Artisan lens is the longest-serving example of intended for implantation in the anterior chamber.1 an iris-supported lens. Unfortunately, the first 5-year follow-up study demon- strated a high rate of angle recession, glaucoma, hyphe- Posterior chamber phakic IOLs. The move to the pos- ma, endothelial cell loss, and decentration, leading to terior chamber began in the 1980s, when surgeons began removal in up to 60% of cases.2 Subsequent lens designs fixating iris-supported lenses on the posterior rather than improved, and today, in addition to anterior chamber the anterior face of the iris but continued to place the phakic IOLs, posterior chamber phakic IOLs are also optic in the anterior chamber.6 These so-called anterior- available. posterior lenses were associated with pupil block and Anterior chamber phakic IOLs. Phakic IOLs designed daytime photophobia in bright light, as the pupil could for the anterior chamber are either angle-supported or not constrict beyond a certain size due to the protrud- iris-supported. Angle-supported lens models include ing optic.6 The only such lens in use today is a one-piece the AcrySof Cachet one-piece foldable lens (Alcon meniscus PMMA lens, the Nikai IOL (Soleko). Laboratories, Inc.) and the two-piece Kelman Duet After this experience, lenses placed entirely in the Implant (Tekia).3 Several rigid PMMA angle-supported posterior chamber were developed in the early 1990s. lenses are still used in Europe, notably the ZSAL-4 The first lens of this design was what is now called the (Morcher GmbH). With its flexible haptics, this lens is Implantable Collamer Lens (ICL; STAAR Surgical);7 others designed to disperse compressive forces, reduce move- followed, including the Sticklens (IOLTech Laboratories). ment, and thus, decrease endothelial damage.4 Iris-supported lenses were developed to avoid the POTENTIAL PROBLEMS complications seen with angle-supported lenses in their AND SAFETY CONSIDERATIONS early years. The longest-serving example is the Artisan Endothelial cell count. Arguably the two most lens (Ophtec GmbH; Figure 1), a one-piece PMMA lens important parameters for contraindication of phakic that fixates onto the anterior surface of the iris. A fold- IOL implantation are anterior chamber depth (ACD) able version of this lens, the Artiflex, is also available. less than 2.8 mm and endothelial cell count (ECC) lower Studies have shown that endothelial loss rates with this than 2,500 cells/mm2 at 20 years of age or 2,000 cells/ lens are no higher than natural atrophy.5 mm2 at 40 years of age.3 However, these parameters are

30 Cataract & Refractive Surgery Today EUROPE July/August 2012 Refractive Surgery Feature story

A calculation based on the ECC, the age of the patient, and the natural endothelial cell death rate can be used to determine safety.

risk for decompensation.15 The usual rule is that these indices stabilize after initial postoperative decompensation as rates of hexagonal cells increase.11 Reversal of this trend may be an indication for explantation. Angle considerations. A stable refraction and good ocular health are also important criteria. For posterior Figure 2. Evaluating endothelial morphology is important in chamber phakic IOLs, an open angle is the most impor- determining the potential risk of phakic IOL surgery. tant factor; Shaffer grades 3 and 4 are the least problem- atic angles.16 no longer absolute and should be considered on a case- Age. Declining endothelial cell counts and increasing by-case basis. A calculation based on the ECC, the age of crystalline lens thickness, which both occur with aging, the patient, and the natural endothelial cell death rate reduce ACD. Current thinking suggests 50 years of age (14 cells/mm2/year) can be used to determine safety.8 is the upper-age limit for phakic IOL implantation.3 One All intraocular procedures entail some degree of endo- must also bear in mind that phakic IOL implantation thelial cell loss, and insertion of a phakic IOL induces preserves the crystalline lens, and therefore, in a younger between 2.1% and 7.6%.3 Postoperative endothelial loss patient, preserves accommodation. In patients of pres- is also an important issue. In one study, the Artisan lens byopic age, this advantage is void, and the surgeon must was associated with endothelial cell loss of 1.06% at consider whether these patients would not be better 1 year, with an average yearly endothelial cell density served by clear lens extraction and placement of a pseu- change of -1.7% over the course of 3 years9 compared dophakic lens such as a multifocal.17 with the natural average change of -0.6%.10 Another Crystalline lens rise. Another recently recognized safety study showed 1-year endothelial loss rates of 3.5%; how- criterion proposed for anterior chamber phakic IOLs is ever, the loss rate stabilized over 5 years and the percent- crystalline lens rise,18 defined as the distance between the age of hexagonal cells increased, indicating stability.11 For anterior pole of the crystalline lens and the horizontal the ICL, the 1-year endothelial cell loss rate was 5.17% plane joining the opposite iridocorneal recesses. Among in one study,12 and, in another, a cumulative decrease of 87 eyes implanted with an Artisan IOL, little risk of pig- 7.7% was seen in endothelial cell density over 5 years.13 ment dispersion was found when the crystalline lens rise The reason for the discrepancy is possibly due to chronic was less that 600 µm. Beyond this level, the incidence low-grade inflammation.14 jumped to 67%. Postoperative checks are vital to detect higher-than- Additionally, due to natural thickening, the anterior expected rates of endothelial cell loss, and the lens pole of the crystalline lens moves forward by 20 µm each should be removed if the loss rate is too high.3 There is year, and for every 1.00 D of accommodation the ante- debate as to how high the cell loss rates must be before rior pole moves forward by 30 µm.19 Anterior segment one contemplates removal, with the options based on optical coherence tomography (OCT) can be used to an absolute ECC or on cumulative loss compared with calculate whether a phakic IOL—and which model—is preoperative values. safe to implant.20 Endothelial morphology. A high rate of hexagonal cells Cataract formation. The incidence of nuclear cataract indicates endothelial stability. During pre- and postopera- 4 years after angle-supported phakic IOL implantation tive evaluation of the endothelium, check for signs of poly- has been reported as 3.42%.21 In one series of posterior megathism and pleomorphism, which are variations in the chamber IOLs,22 8.2% of 170 patients developed some size and shape of the cells, respectively (Figure 2). Corneas degree of anterior subcapsular opacity, which was symp- with high rates of polymegathism and pleomorphism do tomatic in five patients (2.3%) and required phacoemul- not tend to do well after intraocular surgery, and the pres- sification in two patients (1.2%). As 86% of these anterior ence of less than 50% hexagonal cells is considered high subcapsular elements presented within 7 months of the

July/August 2012 Cataract & Refractive Surgery Today Europe 31 Refractive Surgery Feature story

Take-Home Message Mohammed Muhtaseb, FRCOphth, is a Consultant Ophthalmic Surgeon at the Royal • Insertion of a phakic IOL induces between 2.1% and Glamorgan Hospital, Wales, United Kingdom. 7.6% endothelial cell loss. Dr. Muhtaseb states that he has no financial • During pre- and postoperative evaluation of the interest in the products or companies men- endothelium, check for polymegathism and tioned. He may be reached at tel: +44 7949 235 666; pleomorphism. e-mail: [email protected]. • Anterior segment OCT can indicate whether a Gwyn Samuel Williams, MRCS, is a Specialist phakic IOL is safe to implant, and which one. Registrar at the Royal Glamorgan Hospital, • The most vital preoperative consideration is Wales, United Kingdom. Dr. Williams states accurate calculation of the phakic IOL power. that he no financial interest in the products or companies mentioned. He may be reached at operation and tended to be within the first group of tel: +44 1792 797398; e-mail: gwynwilliams@ patients operated upon by individual surgeons, the study doctors.org.uk. authors posited that surgical technique and adequate sizing were more relevant to cataract formation than the 1. Brown CA. Anterior chamber implants with the Ridley tripod lens. Proc R Soc Med. 1976;69:908-911. 2. Barraquer J. Anterior chamber plastic lenses. Results of and conclusions from five years’ experience. Trans presence of the lens in the posterior chamber. Cataract Ophthalmol Soc UK. 1959;79:393-424. formation does not always occur; one of the first patients 3. Lovisolo CF, Reinstein DZ. Phakic intraocular lenses. Surv Ophthalmol. 2005;50:549-587. 4. Jiminez-Alfaro I, Garcia-Feijoo J, Perez-Santonji JJ, et al. Ultrasound biomicroscopy of ZSAL-4 anterior chamber who underwent posterior chamber phakic IOL implanta- phakic intraocular lenses for high myopia. J Refract Surg. 2001;17:641-645. tion showed no sign of cataract at 18-year follow-up.14 5. Budo C, Hessleohl JC, Izak M, et al. Multicenter study of the Artisan phakic intraocular lens. J Cataract Refract Surg. 2000;26:1163-1171. Intraocular pressure (IOP) and uveitis. The level of 6. Fyodorov SN, Zuev VK, Aznabayev BM. Intraocular correction of high myopia with negative posterior chamber initial surgical trauma due to phakic IOL insertion deter- lens. Ophthalmosurgery. 1991;3:57-58. 7. Rosen E, Gore C. Staar Collamer posterior chamber phakic intraocular lens to correct myopia and hyperopia. mines postoperative rates of uveitis and pigmentary J Cataract Refract Surg. 1998;24:596-606. dispersion glaucoma.3 Newer phakic IOL designs and 8. Lovisolo CF, Pesando PM. The implantable contact lens and other phakic IOLs. Canelli, Italy: Fabiano; 1999. 9. Stulting RD, John ME, Maloney RK, et al. Three-year results of Artisan/Verisyse phakic intraocular lens implanta- the performance of prophylactic peripheral iridotomies tion. Results of the United States Food and Drug Administration clinical trial. Ophthalmology. 2008;115:464-472. have been introduced to prevent pupil block. Therefore, 10. Bourne WM, Nelson LR, Hodge DO. Central corneal endothelial changes over a ten-year period. Invest Ophthal- mol Vis Sci. 1997;38:779-782. transient rise in postoperative IOP is now thought to 11. Benedetti S, Casamenti V, Benedetti M. Long-term endothelial changes in phakic eyes after Artisan intraocular be related more to steroid use than to the operation lens implantation to correct myopia: five-year study. J Cataract Refract Surg. 2007;33:784-790. 23,24 12. Jiminez-Alfaro I, Benitez del Castillo JM, Garcia-Feijoo J, et al. Safety of posterior chamber phakic intraocular itself. There have, however, still been reports of lenses for the correction of high myopia: anterior segment changes after posterior chamber phakic intraocular lens intractable increases in IOP requiring trabeculectomy25 implantation. Ophthalmology. 2001;108:90-99. 13. Alfonso JF, Baamonde B, Fernandez-Vega L, et al. Posterior chamber collagen copolymer phakic intraocular as well as pupil block despite a patent peripheral iri- lenses to correct myopia: five-year follow up. J Cataract Refract Surg. 2011;37:873-880. dotomy.26 14. Bozkurt E, Yazici AT, Yildirim Y, et al. Long-term follow-up of first-generation posterior chamber phakic intraocular lens. J Cataract Refract Surg. 2010;36:1602-1604. Similarly, postoperative uveitis is no longer a signifi- 15. Phillips C, Laing R, Yee, R. Specular Microscopy. In: Krachmer JH, Mannis MJ, Holland A, eds. Cornea, Volume 1: cant long-term problem with modern lens designs.23 Fundamentals, Diagnosis and Management, 2nd ed. London: Elsevier Mosby; 2005; 268. 16. Lovisolo CF, Pesando PM. Posterior chamber phakic intraocular lenses. In: Alio JL, Perez-Santonja JJ, eds. However, one group of researchers found evidence of Refractive Surgery with Phakic IOLs. Fundamentals and Practice. El Dorado, Panama: Highlights of Ophthalmology low-grade anterior chamber inflammation up to 2 years International; 2004; 135-164. 27 17. Patel V, Muhtaseb M. Endothelial cell loss after pIOL implantation for high myopia. J Cataract Refract Surg. postoperatively. 2008;34:1424-1425. 18. Baikoff G, Bourgeon G, Jodai HJ, et al. Pigment dispersion and Artisan implants: crystalline lens rise as a safety criterion [article in French]. J Fr Ophtalmol. 2005;28:590-597. OTHER CONSIDERATIONS 19. Muftuoglu O, Alio JL. Anterior chamber angle-supported complications. In: Alió JL, Azar DT, eds. Management Patients who are best served by a less-invasive refractive of Complications in Refractive Surgery. Berlin: Springer-Verlag; 2008: 236. 20. Baikoff G, Lutun E, Wei J, et al. Refractive phakic IOLs: three different models and contact with the crystalline solution, such as spectacles, contact lenses, or LASIK, lens. An AC-OCT study [article in French]. J Fr Ophtalmol. 2005;28:303-308. should be contraindicated for phakic IOL implantation. 21. Alio JL, de la Hoz F, Ruiz-Moreno JM, et al. Cataract surgery in highly myopic eyes corrected by phakic anterior chamber angle-supported lenses. J Cataract Refract Surg. 2000;26:1303-1311. One advantage of phakic IOL insertion over clear lens 22. Sanchez-Galeana CA, Smith RJ, Sanders DR, et al. Lens opacities after posterior chamber phakic intraocular lens extraction or LASIK is that the lens can be removed or implantation. Ophthalmology. 2003;110:781-785. 28 23. Huang D, Schallhorn SC, Sugan A, et al. Phakic intraocular lens implantation for the correction of myopia. replaced; however, this is by no means desirable nor Ophthalmology. 2009;116:2244-2258. is it common, as reoperation rates are below 8% in the 24. Aguilar-Valenzuela L, Lleo-Perez A, Alonso-Munoz L, et al. Intraocular pressure in myopic patients after Worst- 23 Fechner anterior chamber phakic intraocular lens implantation. J Refract Surg. 2003;19:131-136. majority of studies and less than 4% in others. The vast 25. Sanchez-Galeana CA, Zadok D, Montes M, et al. Refractory intraocular pressure increase after phakic posterior majority of explantations in these series were performed chamber intraocular lens implantation. Am J Ophthalmol. 2002;134:121-123. 26. Kodjikian L, Gain P, Donate D, et al. Malignant glaucoma induced by a phakic posterior chamber intraocular lens due to one of the complications described above, but for myopia. J Cataract Refract Surg. 2002;28:2217-2221. refractive errors still occur, and one of the most vital 27. Perez-Santonja JJ, Iradier MT, Benitez del Castillo, et al. Chronic subclinical inflammation in phakic eyes with intraocular lenses to correct myopia. J Cataract Refract Surg. 1996;22:183-187. preoperative considerations is accurate calculation of the 28. Trindade F, Pereira F. Exchange of a posterior chamber phakic intraocular lens in a highly myopic eye. J Cataract power of phakic lens needed. n Refract Surg. 2000;26:773-776.

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