Simultaneous vs. bilateral LASIK

Letters to the Editor In ACG patients with extensive or total synechial angle closure, however, the trabecular meshwork will remain occluded by peripheral anterior synechiae, despite anterior chamber deepening after cataract extraction. The trabecular meshwork will only be exposed if goniosynechialysis3 (GSL) is performed to separate adherent iris from the meshwork. To confirm this, we have performed ultrasound biomicroscopic examination of the anterior segment of an eye with 360° peripheral anterior synechiae and chronic ACG that underwent cataract extraction by phacoemulsification, intraocular lens implantation, and limited GSL over only the inferior 180° of the angle before and after surgery. Before cataract surgery and GSL, the trabecular meshwork was occluded by peripheral anterior synechiae in the whole 360° of the angle. After surgery, the anterior chamber depth and the apparent angle width increased significantly in the whole 360° of the angle as a result of the replacement of the thick cataractous lens by a thin intraocular lens. The trabecular meshwork is, however, only exposed to the aqueous in the inferior 180° of the angle, as a result of the adherent iris having been pulled away from the meshwork by GSL. In the superior 180° of the angle, the trabecular meshwork remained occluded by adherent peripheral iris despite the dramatic deepening of the anterior chamber. The trabecular meshwork had once again become accessible to aqueous in the anterior chamber only in that area where GSL was performed. Hayashi et al also stated in their article that “After cataract surgery, the IOP decreased in all three groups. No statistically significant differences were found in the mean IOPs at 1 and 6 months after surgery between the three groups, . . . ” Hayashi et al did not, however, report what IOP–lowering medications the glaucoma patients were receiving both before and after cataract surgery. We could not assess the IOP effects of cataract extraction without knowing the preoperative and postoperative glaucoma medications. CLEMENT C.Y. THAM, FRCS JIMMY S.M. LAI, FRCS, FRCOPHTH DENNIS S.C. LAM, FRCS, FRCOPHTH Hong Kong References 1. Hayashi K, Hayashi H, Nakao F, Hayashi F. Changes in anterior chamber angle width and depth after intraocular lens implantation in eyes with glaucoma. Ophthalmology 2000;107: 698 –703. 2. Ritch R. Argon laser peripheral iridoplasty: an overview. J Glaucoma 1992;1:206 –13. 3. Shingleton BJ, Chang MA, Bellows AR, Thomas JV. Surgical goniosynechialysis for angle-closure glaucoma. Ophthalmology 1990;97:551– 6.

Author’s reply Dear Editor: Drs. Tham, Lai, and Lam have raised some very important questions about our article regarding the intraocular pressure (IOP)–reducing effect of cataract extraction in eyes with angle-closure glaucoma (ACG). We agree that the IOP-lowering effect of cataract surgery in eyes with ACG

varies on the basis of the extent of synechial angle closure. However, they may have missed the gist of this article, which was to demonstrate changes in anterior chamber angle width and depth after cataract surgery, and not necessarily to document long-term IOP control. We hope to present the effects of cataract extraction on IOP control and number of glaucoma medications required in a separate report. We performed gonioscopic examinations the day before surgery and again 1 month after surgery in all patients. The eyes with ACG showed various degrees of peripheral anterior synechiae. We found that the extent of peripheral anterior synechiae postoperatively was less than that measured preoperatively. In practicality, it is difficult to accurately measure the extent of peripheral anterior synechiae before surgery, and it has been reported that gonioscopy before lens extraction may frequently overestimate the degree of synechial closure.1,2 Furthermore, we do not recommend prophylactic clear lens extraction for eyes with ACG, particularly in its initial stage; we definitely prefer laser iridotomy as a prophylactic treatment for ACG when cataract is not visually significant. Tham, Lai, and Lam describe an interesting patient with severe chronic primary ACG who underwent simultaneous goniosynechialysis and cataract surgery. We cannot state for which eyes with ACG the simultaneous goniosynechialysis is necessary. However, we are concerned about whether the degree of synechial closure can be accurately measured with ultrasound biomicroscopy. Furthermore, one must be cautious in reaching a conclusion regarding the necessity of goniosynechialysis on the basis of a single case. The mean number of glaucoma medications decreased significantly after cataract surgery in the eyes with ACG and those with open-angle glaucoma. However, the number of medications for eyes with ACG was less than that for eyes with open-angle glaucoma. As mentioned earlier, we will present additional data in our next report. KEN HAYASHI, MD HIDEYUKI HAYASHI, MD FUMINORI NAKAO, MD FUMIHIKO HAYASHI, MD Fukuoka, Japan References 1. Gieser DK, Wilensky JT. Laser iridectomy in the management of chronic angle-closure glaucoma. Am J Ophthalmol 1984;98: 446 –50. 2. Acton J, Salmon JF, Scholtz R. Extracapsular cataract extraction with posterior chamber lens implantation in primary angleclosure glaucoma. J Cataract Refract Surg 1997;23:930 – 4.

Simultaneous vs. Bilateral LASIK Dear Editor: In their article, Chiang and Hersh1 concluded that it is theoretically advantageous to perform sequential bilateral laser in situ keratomileusis (LASIK) as opposed to simultaneous bilateral LASIK. We have several concerns with regard to this conclusion. First, in our study of 2142 consecutive simultaneous and sequential bilateral myopic LASIK cases, we found no

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Ophthalmology Volume 108, Number 3, March 2001 statistically significant difference in 3- to 6-month postoperative refractive or visual outcomes, including spherical equivalent, uncorrected acuity, best-corrected visual acuity, and retreatment rates.2 In fact, the retreatment rate in sequential eyes was slightly higher, although not statistically significantly higher than in simultaneous bilateral eyes. Second, other studies, including a prospective study by Waring et al3,4 involving 714 eyes, have also concluded that simultaneous bilateral surgery was equally safe and effective as compared with sequential bilateral surgery. (Vicary D, et al. American Society of Cataract and Refractive Surgery, Symposium on Cataract, IOL and Refractive Surgery, 1998;34. Hardten DR, et al. American Society of Cataract and Refractive Surgery, Symposium on Cataract, IOL and Refractive Surgery, 1998;34.) In addition, only sequential surgeries in 196 eyes were studied by Chiang and Hersh,1 compared with the larger studies cited above, which included both simultaneous and sequential bilateral surgeries.2– 4 (Vicary D, et al. American Society of Cataract and Refractive Surgery, Symposium on Cataract, IOL and Refractive Surgery, 1998;34. Hardten DR, et al. American Society of Cataract and Refractive Surgery, Symposium on Cataract, IOL and Refractive Surgery, 1998;34.) Finally, Chiang and Hersh1 found no statistically significant differences in measured postoperative manifest refraction or variance from emmetropia between the first and second eyes, nor was there any mention of retreatment rates for first or second eyes. The authors admit that the “improved outcomes of sequential treatments shown are theoretical and are not clinically proved.” Although it continues to be important to examine both theoretical results (or outcomes) as well as data from clinical trials, caution is advisable when drawing conclusions from theoretical outcomes. This is especially true when the weight of clinical data, including the data from the Chiang and Hersh study, do not support the theoretical conclusion. HOWARD V. GIMBEL, MD, MPH JOHN A. VAN WESTENBRUGGE, MD, FRCSC ELLEN E. ANDERSON PENNO, MD, MS Calgary, Alberta, Canada References 1. Chiang PK, Hersh PS. Comparing predictability between eyes after bilateral laser in situ keratomileusis: a theoretical analysis of simultaneous versus sequential procedures. Ophthalmology 1999;106:1684 –91. 2. Gimbel HV, van Westenbrugge JA, Anderson Penno EE, et al. Simultaneous bilateral laser in situ keratomileusis: safety and efficacy. Ophthalmology 1999;106:1461–7; discussion 1467– 8. 3. Waring GO III, Carr JD, Stulting RD, et al. Prospective randomized comparison of simultaneous and sequential bilateral laser in situ keratomileusis for the correction of myopia. Ophthalmology 1999;106:732– 8. 4. Waring GO III, Carr JD, Stulting RD, Thompson KP. Prospective, randomized comparison of simultaneous and sequential bilateral LASIK for the correction of myopia. Trans Am Ophthalmol Soc 1997;95:271– 84.

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Author’s reply Dear Editor: Drs. Gimbel, van Westenbrugge, and Penno make important points with regard to the clinical implications of our paper. As we did stress, our study was theoretical. Not withstanding this design, however, we did find a correlation in refractive outcome between the two eyes of an individual patient. This suggests that the first eye result may be applied to improve the outcome of the second eye in some patients. Such a correlation has been supported by other investigators (Nguyen LH, et al. Invest Ophthalmol Vis Sci 2000[Suppl]: 41, S687). This finding implies the need for clinical studies specifically directed at this issue if we want to definitively answer the question, but does not address the clinical significance of such a between-eye correlation. Other factors, including general safety of bilateral procedures found in current clinical studies, anisometropia between surgery, and patient dissatisfaction with needing two operative sessions, may mitigate any advantage gained. Analysis in those clinical studies to date that show no difference in refractive outcomes between simultaneous and sequential LASIK, although well designed and executed, are population based and are not specifically designed to look at individual patients in whom this between-eye correlation may be clinically important. Rather, clinical trials specifically addressing the potential difference between simultaneous and sequential treatments with regard to the predictive ability of the first eye on second eye refractive outcome are necessary to uncover or dispel any actual clinical significance of our findings. In the absence of such further study, careful clinical judgment should be used in the decision to perform simultaneous or sequential surgery on an individual patient. PETER S. HERSH, MD PETER K. CHIANG, MD Teaneck, New Jersey

Pyramidal Anterior Polar Cataracts Dear Editor: The article by Wheeler et al1 (Ophthalmology 1999;106: 2362–7) is interesting and informative, primarily designed to study the clinical features and management of pyramidal cataracts. In this respect it is of excellent quality and right on target. However, I have made two observations relative to the histopathology discussion that need to be clarified. This may help address some unanswered questions raised in the article. The authors have concluded that although pyramidalshaped anterior polar lens opacities are often associated with progressive opacification of the underlying lens cortex, their flat, plaque-like counterparts are generally nonprogressive. They correctly note that normal lens capsule and cuboidal epithelium are frequently found at the base of anterior polar lens lesions. They further state that the pyramidal lesions in their study have histologic similarity to other anterior polar cataracts and include the features described earlier. Their photomicrographs (Fig. 3), indeed, demonstrate a reduplication of the lens capsule that effectively surrounds a polar opacity composed of spindle-