The effect of capsulorhexis size on posterior capsular opacification: One-year results of a randomized prospective trial

PURPOSE: Posterior capsular opacification is the most common surgically rel ated cause of reduced vision after cataract surgery. We studied the effect of capsulorhexis size on the pattern and severity of posterior capsular opa cification. METHODS: In this prospective study 75 patients underwent standardized phaco emulsification with capsulorhexis and in-the-bag placement of a 5.5-mm poly methylmethacrylate intraocular lens implant. The patients were randomly ass igned to receive either a small capsulorhexis of 4.5 to 5 mm to lie complet ely on the intraocular lens optic or a large capsulorhexis of 6 to 7 mm to lie completely off the lens optic, Patients were examined at days 1, 14, 30 , 90, and 180 and at year 1 with logMAR visual acuity assessment, Pelli-Rob son contrast sensitivity testing, anterior chamber flare and cell measureme nt, and high-resolution digital retroillumination imaging of the posterior capsule. The pattern of posterior capsular opacification was determined, an d the percentage area of posterior capsular opacification was calculated fo r each image with dedicated image analysis software, RESULTS: Large capsulorhexes were associated with significantly more wrinkl ing of the posterior capsule and worse posterior capsular opacification tha n small capsulorhexes. At 1 year the average percentage area of posterior c apsular opacification was 32.7% for small capsulorhexes (95% confidence int erval, 19.8 to 45.6) and 66.2% for large capsulorhexes (95% confidence inte rval, 57.7 to 74.6) (P = .0001). The patients with large capsulorhexes had significantly poorer visual acuities and a trend toward worse contrast sens itivities. CONCLUSION: This study demonstrated significantly greater wrinkling and opa cification of the posterior capsule and worse visual acuity with large caps ulorhexes than with small capsulorhexes, In cataract surgery with a polymet hylmethacrylate intraocular lens, a small capsulorhexis with the edge compl etely on the surface of the implant is preferable to a large capsulorhexis in reducing posterior capsular opacification. (Am J Ophthalmol 1999; 128:27 1-279. (C) 1999 by Elsevier Science Inc. All rights reserved.)