Reply: Capsule stabilization devices

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pushing IOL power calculations from paraxial to exact optics, in which real physical parameters (ie, radii of curvature, conic constants, distances between surfaces, and indices of refraction) are measured and calculated (T. Olsen, MD, ‘‘Exact IOL Calculation Without Fudge Factors,’’ presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, March 2006).1,2 Moreover, HOAs have become a reality to deal with. Spherical aberration and coma can significantly alter the best focus plane position after keratorefractive surgery, and selection of adequate IOL asphericity (as more options are marketed) becomes mandatory in these cases. These calculations can be done using ray-tracing software such as Okulix; optical design software such as Zemax (Zemax Development Corporation), OSLO (Lambda Research Corporation), and Winlens (Linos Photonics); or self-programmed software (ie, spreadsheet program) from an optics text book.3 In the last 2 cases, pseudophakic ACD prediction algorithms that calculate the real physical position of the IOL (not the ELP) are needed.4,5 As it can be deduced, exact ray tracing turns out to be an ideal tool to analyze the effect of the change (error) in any variable in the performance of the system; it is a quick procedure thanks to the high computational power available today. Accuracy will always be better than with the Gaussian optics method as long as the eye being studied is correctly modeled.dJaime Aramberri, MD REFERENCES 1. Ishikawa T, Hirano A, Murai K, et al. [Intraocular lens calculation for cataract treated with photorefractive keratectomy using ray tracing method.] [Japanese] Nippon Ganka Gakkai Zasshi 2000; 104:165– 169 2. Preussner P-R, Wahl J, Lahdo H, et al. Ray tracing for intraocular lens calculation. J Cataract Refract Surg 2002; 28:1412–1419 3. Smith G, Atchison DA. Image formation and ray tracing In: The eye and visual optical instrument. Cambridge, Cambridge University Press, 1997; 21–47 4. Olsen T. Prediction of the effective postoperative (intraocular lens) anterior chamber depth. J Cataract Refract Surg 2006; 32:419–424 5. Norrby NES, Koranyi G. Prediction of intraocular lens power using the lens haptic plane concept. J Cataract Refract Surg 1997; 23: 254–259

Capsule stabilization devices In their article regarding capsule stabilization devices, Nishimura et al.1 refer to my report2 describing the use of such devices in 2000. As the authors state, the original retractors (available from Duckworth and Kent) were metallic. I recognized the inherent disadvantages of this (more difficult to insert, more likely to tear the margins of the capsulorhexis if excessive tension was created during the procedure) and designed disposable nylon retractors soon thereafter. The retractors have been available from Impex and FCI Ophthalmics since 2002 and 2005, respectively. I have used these devices in approximately 300 patients over the past 4 years and found them to provide consistent support of the lens capsule during phacoemulsification in the presence of weak or indeed virtually absent zonular support. I have no financial interest in the product, but I am a consultant to Impex and have been granted a United States patent regarding the use of capsular support devices (Inventor, Richard

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J. Mackool, MD; assignee, Alcon; ‘‘Intraocular Device for Stabilization of a Lens Capsule;’’ patent number 6183480; issued February 6, 2006). RICHARD MACKOOL, MD Astoria, New York, USA

REFERENCES 1. Nishimura E, Yaguchi S, Nishihara H, et al. Capsule stabilization device to preserve lens capsule integrity during phacoemulsification with a weak zonule. J Cataract Refract Surg 2006; 32:392–395 2. Mackool RJ. Capsule stabilization for phacoemulsification [letter]. J Cataract Refract Surg 2000; 26:630

Reply: We thank Mackool for his comments about our report of a new capsule stabilization device for supporting a lens with weak zonular support.1 The device was made in 2002, and since 2003, it has been used in approximately 100 eyes. The purpose of the capsule stabilization device is to stabilize the capsule safely. We know of some phacoemulsification techniques for cases of zonular weakness.2–6 The flexible iris retractor is a conventional instrument designed to hook the edge of the iris. The retractor is useful for standard surgery in eyes with a small pupil, but not for supporting the lens capsule. Since 1997, several reports have described phacoemulsification using the retractor at the edge of the continuous curvilinear capsulorhexis.2–5 During surgery, the iris retractor sometimes detached from the lens capsule because it was too short to obtain capsule stability. Our device has a Tshaped end that passes around the anterior capsule flap to fit the curvature of the equator and minimize stress on the capsule equator. The T-shaped end suspends and protects the capsule at a few points gently and stably. Mackool reported capsule stabilization using relatively long metallic retractors.6 However, because the metallic retractor is hard, it can damage the endothelium, corneal incision, and capsule on insertion, manipulation, or removal. In contrast, our device is flexible, 10.0 mm in length, and fashioned from 5-0 nylon. We have not experienced any technical difficulty during the course of phacoemulsification. The T-shaped end is a unique feature of the device. The capsule stabilization device aided in supporting and stabilizing the lens capsule during phacoemulsification in cases with a weak zonule. We believe it ensures a stable capsule–iris complex, reducing surgical risks.dEiichi Nishimura, MD, PhD, Shigeo Yaguchi, MD, PhD, Hitoshi Nishihara, MD, Masahiko Ayaki, MD, PhD, Tadahiko Kozawa, MD, PhD REFERENCES 1. Nishimura E, Yaguchi S, Nishihara H, et al. Capsular stabilization device to preserve lens capsule integrity during phacoemulsification with a weak zonule. J Cataract Refract Surg 2006; 32:392–395 2. Nova´k J. Flexible iris hooks for phacoemulsification. J Cataract Refract Surg 1997; 23:828–831 3. Merriam JC, Zheng L. Iris hooks for phacoemulsification of the subluxated lens. J Cataract Refract Surg 1997; 23:1295–1297

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4. Lee V, Bloom P. Microhook capsule stabilization for phacoemulsification in eyes with Pseudoexfoliation-syndrome-induced lens instability. J Cataract Refract Surg 1999; 25:1567–1570 5. Santoro S, Sannace C, Cascella MC, Lavermicocca N. Subluxated lens: phacoemulsification with iris hooks. J Cataract Refract Surg 2003; 29:2269–2273 6. Mackool RJ. Capsule stabilization for phacoemulsification [letter]. J Cataract Refract Surg 2000; 26:630

Another reason to celebrate Koch, Kohnen, Mamalis, Obstbaum, and Rosen rightly crow to celebrate 10 years of the amalgamation of the American and European journals.1 They briefly cite advances that have been made in the past 10 years, but I think omitted a very important one: an easily recognizable improvement in the quality of the published papers. By my reading, a decade ago, many papers felt more like informal communications that one would encounter in a chat group; contrast this to the circumstance now in which there is a consistently high scientific and clinical quality to the majority of contributions. Congratulations to the diligence of the editors, their board, and the contributing authors. DR. GEORGE O. WARING, III, MD, FRCOPHTH Editor-in-Chief, Journal of Refractive Surgery Atlanta, Georgia, USA

REFERENCE 1. Koch DD, Kohnen T, Mamalis N, et al. Celebrating 10 years. J Cataract Refract Surg 2006; 32:1

Reply: We greatly appreciate Waring’s kind comments. We actually have similar views about the improvements in and high quality of all the leading peer-reviewed ophthalmology journals, certainly including the Journal of Refractive Surgery. Credit for this progress goes to all who participate in the peerreview process, including authors, reviewers, managing editorial staff, editors, and publishers.dDouglas D. Koch, MD, Thomas Kohnen, MD, Nick Mamalis, MD, Stephen A. Obstbaum, MD, Emanuel S. Rosen, FRCSE

Controls required to assess IOL movement during accommodation Va´mosi et al.1 prospectively measured the change in anterior chamber depth during an accommodative effort in 22 paired eyes with 2 different foldable intraocular lenses (IOLs). Using an A-scan contact ultrasonic probe, they report a mean change in anterior chamber depth of 0.57 mm G 0.25 (SD) and 0.42 G 0.24 mm at the 12-month time window following the surgery. To assess the significance of the study’s findings, controls are required to determine the variability (standard deviation) of the

A-scan measurements of the IOL position without any accommodative effort at each time window. In addition, the same baseline measure of the variability of their A-scan measurements of the lens position with cycloplegia is required at each time window. Data concerning these measures of variability in the authors’ technique were not provided and are essential before any assessment of change associated with accommodation is possible. Using the limited data provided in the paper, I calculated that the mean of the standard deviations of the A-scan measurements of the lens position for both IOLs at all time periods was G0.22 mm. To conclude that any change in IOL position occurred at a 95% level of confidence, the difference must exceed G0.44 (2 times the standard deviation). This estimate of the accuracy of their measurements is essentially the same magnitude as the differences associated with accommodation that they report. Consequently, the lack of precision of the authors’ A-scan measurements of the IOL position makes it impossible to assess movement of an IOL associated with accommodation. RONALD A. SCHACHAR, MD, PHD Dallas, Texas, USA

REFERENCE 1. Va´mosi P, Nemeth G, Berta A. Pseudophakic accommodation with 2 models of foldable intraocular lenses. J Cataract Refract Surg 2006; 32:221–226

Posterior corneal surface changes after H-LASIK In their article about corneal surface changes after hyperopic laser in situ keratomileusis (H-LASIK), Ueda et al.1 mention that the ‘‘clinically measured posterior corneal surface moved backward after H-LASIK.’’ This possibility occurred to me in 1999 when we treated a patient with acute angle-closure glaucoma after hyperopic LASIK.2 Thinning of the peripheral cornea as in H-LASIK could shift the posterior cornea closer to the iris. A thinner peripheral cornea loses part of its resistance. A shallow anterior chamber will be shallower if the posterior corneal surface shifts backward, putting the patient at a higher risk for developing acute angleclosure glaucoma. A Medline search for acute angle-closure glaucoma after HLASIK did not show other reports at that time or now. From a pragmatic point of view, the reality is that there are no other reports of acute angle-closure glaucoma after thousands of H-LASIK procedures performed worldwide over the years. MIGUEL PACIUC, MD Mexico City, Mexico REFERENCES 1. Ueda T, Nawa Y, Masuda K, et al. Posterior corneal surface changes after hyperopic laser in situ keratomileusis. J Cataract Refract Surg 2005; 31:2084–2087

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