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Michael J. Endl, MD; Carlos E. Martinez, MS, MD; Stephen D. Klyce, PhD; Marguerite B. McDonald, MD; Steven J. Coorpender, MS; Raymond A. Applegate, OD, PhD; Howard C. Howland, PhD

Arch Ophthalmol. 2001;119:1159-1164.

Objective  To evaluate the effects of photorefractive keratectomy on corneal optical aberrations using a 5.5-mm optical zone and a 7.0-mm transition zone.

Methods  Videokeratographs of 72 eyes from 47 patients treated for low to moderate (1-9 diopters) myopia were obtained at the preoperative and 1-, 3-, 6-, 12-, and 18-month postoperative examinations. The videokeratoscopy data files were used to calculate the wavefront variance of the corneas for small (3-mm) and large (7-mm) pupils using a previously described method.

Results  In general, all optical aberrations decreased postoperatively for 3-mm pupils and increased for 7-mm pupils compared with preoperative values. For 3-mm pupils, the 2 common optical aberrations (comalike [S₃] and spherical-like [S₄]) decreased postoperatively and never returned to preoperative values. For 7-mm pupils, however, comalike aberrations increased slightly and spherical-like aberrations increased by nearly an order of magnitude during the postoperative period. Similarly, for 3-mm pupils, the higher order S₅ and S₆ aberrations decreased throughout the postoperative period, with S₆ values showing an approximately 23-fold reduction at 12 and 18 months. For 7-mm pupils, S₅ and S₆ aberrations increased slightly, more so for S₅ (approximately 3-fold) than for S₆. Total wavefront aberrations decreased an average of 2.3 times postoperatively for 3-mm pupils, and increased significantly (P<.05) at all postoperative examinations for 7-mm pupils. Opening the pupil from 3 mm to 7 mm before surgery produced a 14-fold increase in total aberrations, whereas this same change produced an average 113-fold increase after photorefractive keratectomy.

Conclusions  Corneal optical aberrations after photorefractive keratectomy with a larger ablation zone and a transition zone are less pronounced and more physiologic than those associated with first-generation (5-mm) ablations with no transition zone.

Clinical Relevance  Evaluating the postoperative corneal aberration structure will help us devise ways to minimize the wavefront aberrations of the eye through the creation of an ideal corneal first surface, thereby improving visual results for patients undergoing excimer laser ablations for refractive correction.

From the LSU Eye Center, Louisiana State University Health Sciences Center (Drs Endl and Klyce and Mr Coorpender), and the Southern Vision Institute (Dr McDonald), New Orleans; the Long Beach Eye Institute, Long Beach, Calif (Dr Martinez); the Department of Ophthalmology, University of Texas Health Science Center at San Antonio (Dr Applegate); and the Department of Neurobiology and Behavior, Cornell University, Ithaca, NY (Dr Howland). None of the authors has any commercial or proprietary interests in any of the instruments used in this investigation.

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