Acrylic multifocal IOLs

Letters to the Editor

ments are intrinsically dependent on the laser platform, and therefore cannot be applied to all other platforms. Theoretical analysis of the problem (independent of the laser platform) has been discussed by Gatinel et al.5 Diego de Ortueta, MD, EBOD Mitrofanis Pavlidis, MD Recklinghausen, Germany REFERENCES

1. Pinelli R, Ngassa EN, Scaffidi E. Sequential ablation approach to the correction of mixed astigmatism. J Refract Surg. 2006;22:787-794. 2. Vinciguerra P, Sborgia M, Epstein D, Azzolini M, MacRae S. Photorefractive keratectomy to correct myopic or hyperopic astigmatism with a cross-cylinder ablation. J Refract Surg. 1999;15:S183-S185. 3. Chayet AS, Montes M, Gomez L, Rodriguez X, Robledo L, MacRae S. Bitoric laser in situ keratomileusis for the correction of simple myopic and mixed astigmatism. Ophthalmology. 2001;108:303-308. 4. Mrochen M, Seiler T. Influence of corneal curvature on calculation of ablation patterns used in photorefractive laser surgery. J Refract Surg. 2001;17:S584-S587. 5. Gatinel D, Hoang-Xuan T, Azar DT. Three-dimensional representation and qualitative comparisons of the amount of tissue ablation to treat mixed and compound astigmatism. J Cataract Refract Surg. 2002;28:2026-2034.

Reply: We appreciate Drs de Ortueta and Pavlidis’ comments. Mixed astigmatism remains a great challenge for our profession. The theoretical and practical problem was and is the partial correction of the cylinder (characteristics of the cross-cylinder technique and the bitoric technique). Our research was focused on the following points: 1) total correction of the positive cylinder (when and if possible), and 2) potential management of the negative sphere. Our purpose, optically speaking, was to obtain, first, a myopic optical system, and second, to treat myopia, managing an almost “spherical” cornea. It is well known that positive cylinder in mixed astigmatism needs less tissue removal than the ablation of the negative cylinder.1 Another important practical point is to reduce the number of retreatments as much as possible. The bitoric technique results in approximately 25% of retreatments.2 In our 40 eyes, no eye has been retreated. The “sequence” of the ablation (first the positive cylinder, then the negative sphere) positively influences the shape, the “economy” of the ablation, its effectiveness, and consequentially the postoperative visual acuity. The sequential ablation was a theoretical concept, based on our persuasions. The optical principle was Journal of Refractive Surgery Volume 23 April 2007

not laser-dependent, our practical application was performed with one laser (Technolas 217 excimer laser, Bausch & Lomb), and the results are reported in our study. However, this does not mean that it would not be possible to reach an algorithmic strategy with other technologies, considering that cross-cylinder and bitoric ablation, as well as sequential ablation, are effective with different lasers. In our experience, the time of exposure of the stromal bed never caused problems related to dehydration; however, the amount of time will be reduced when this method becomes standardized through software produced by different laser companies. In addition, presbyopic multifocal LASIK has been accepted by the scientific community, which follows the concept of separate ablations. We hope that other colleagues try using this technique with different lasers, customizing the parameters from laser to laser, but always maintaining the total correction of the positive cylinder and negative sphere. Roberto Pinelli, MD Brescia, Italy REFERENCES

1. Gatinel D, Hoang-Xuan T, Azar DT. Three dimensional representation and qualitative comparisons of the amount of tissue ablation to treat mixed and compound astigmatism. J Cataract Refract Surg. 2002;28:2026-2034. 2. Albarran-Diego C, Munoz G, Montes-Mico R, Alio JL. Bitoric laser in situ keratomileusis for astigmatism. J Cataract Refract Surg. 2004;30:1471-1478.

Acrylic Multifocal IOLs To the Editor: Acrylic refractive and diffractive multifocal intraocular lens (IOL) implants1-3 have become increasingly popular with cataract surgeons over the past few years. We have often wondered how such IOLs might affect the view of the fundus in diagnosing and treating retinal disorders. We received anecdotal and second-hand reassurances that acrylic multifocal IOLs do not pose a significant problem for the retinal surgeon. Previous authors have described vitreoretinal surgery through silicone multifocal lenses. Lim et al4 performed a rabbit study comparing the view of the posterior segment through a silicone monofocal IOL versus an AMO Array silicone multifocal IOL (AMO, Santa Ana, Calif) during vitrectomy surgery. This study found that although slightly more distortion of light occurred through the Array lens compared to the monofocal lens, this did not impair visibility of the various posterior segment structures and did not

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Letters to the Editor

interfere with the performance of surgery. Mainster et al5 published two cases in which difficulty was encountered in performing vitreoretinal surgery through an AMO Array silicone multifocal lens. One eye underwent retinal detachment surgery; the other eye had macular pucker surgery. The authors concluded that such lenses should not be implanted in patients at risk for future vitreoretinal surgery. To date, no case reports describing difficulty in performing vitreoretinal surgery through an acrylic multifocal lens have been published in the peer-reviewed literature. The AMO Rezoom package insert1 states that although rarely encountered during the clinical trial, the imaging quality and depth of field through this lens may potentially impact vitreoretinal surgery. We gained firsthand experience with difficulties that can occur with the AMO Rezoom lens during vitreoretinal surgery. Patient MS underwent uncomplicated cataract surgery in her right eye with implantation of an AMO Rezoom multifocal IOL. Postoperatively, she reported blurry vision. By 3 months postoperatively, best corrected distance visual acuity was 20/50 related to an epiretinal membrane. Notably, slit-lamp microscopy, optical coherence tomography, and fundus fluorescein angiography and photography were all performed without difficulty and there appeared to be no alteration of the fundus view by the multifocal IOL. However, at the time of membrane peeling, we were surprised and dismayed to find that, despite a perfectly clear view of the macula, stereopsis was markedly reduced. The compromise in depth perception appeared to be consistent in all fields of view through the op-

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erating microscope using a plano contact lens as well as non-contact wide-field viewing system. Surgery was completed with difficulty, but without complication. Monofocal silicone IOLs have been relatively contraindicated in patients with retinal pathology who might require vitreous surgery due to the rapid fogging that occurs under air or silicone oil, which can preclude fundus visualization during vitrectomy. Similarly, if this experience of difficult stereopsis during vitreoretinal surgery through an acrylic multifocal lens is confirmed by other observers, even more caution should be exercised in implanting such lenses in eyes with any pathology that might potentially require vitreous surgery. Jeffrey K. Luttrull, MD Paul J. Dougherty, MD Camarillo, California REFERENCES

1. AMO RezoomTM Acrylic Multifocal Posterior Chamber Intraocular Lens [package insert]. Santa Ana, Calif: Advanced Medical Optics; 2005. 2. Chiam PJ, Chan JH, Aggarwal RK, Kasaby S. ReSTOR intraocular lens implantation in cataract surgery: quality of vision. J Cataract Refract Surg. 2006;32:1459-1463. 3. Blaylock JF, Si Z, Vickers C. Visual and refractive status at different focal distances after implantation of the ReSTOR multifocal intraocular lens. J Cataract Refract Surg. 2006;32:1464-1473. 4. Lim JI, Kuppermann BD, Gwon A, Gruber L. Vitreoretinal surgery through multifocal intraocular lenses compared with monofocal intraocular lenses in fluid-filled and air-filled rabbit eyes. Ophthalmology. 2000;107:1083-1088. 5. Mainster MA, Reichel E, Warren KA, Harrington PG. Ophthalmoscopy and vitreoretinal surgery in patients with an Array refractive multifocal intraocular lens implant. Ophthalmic Surg Lasers. 2002;33:74-76.

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