CORNEAL TOPOGRAPHY FOLLOWING EXCIMER PHOTOREFRACTIVE KERATECTOMY FOR MYOPIA

Corneal topographic analysis was performed on 97 consecutive eyes with at least one month follow-up after excimer laser photorefractive keratectomy for myopia. Centration of the ablated zone was documented in all eyes at the one month postoperative examination with the Topographic Modeling System (Computed Anatomy Inc., NY). Thirty-seven percent of eyes were within 0.25 mm of the pupillary center (PC); 48% of eyes were between 0.25 and 0.50 mm, 13% were between 0.50 and 1.00 mm, and 2% were more than 1.00 mm from the PC. The greatest amount of decentration was 1.50 mm. The mean decentration was 0.36 mm. The surface regularity index (SRI), which is a measure of the optical performance of the cornea, was significantly less at the sixth postoperative month than at the first postoperative month (P = .013). No correlation between the SRI and the amount of decentration was found. Four main patterns of ablation were noted by differential topographic analysis at the one month interval. A central uniform ablation was present in 45% of eyes; ''semicircular ablations'' were present in 33% of eyes, a ''keyhole'' ablation pattern in 12%, and a curious ''central bump'' ablation pattern in 1 0%. Corneal topographic analysis was a useful tool for documenting and quantitating results following excimer photorefractive surgery.