CORNEAL TOPOGRAPHY OF PHOTOREFRACTIVE KERATECTOMY VERSUS LASER IN-SITU KERATOMILEUSIS

Objective: This study aimed to compare qualitative patterns of corneal topography early in the postoperative course after excimer laser phot orefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) when used for the treatment of myopia of 6.0 to 15.0 diopters. Design : The study design was a prospective, multicenter, randomized clinical trial. Participants: A total of 64 eyes were treated with PRK and 54 eyes were treated with LASIK. Intervention: Using the Summit Apex exci mer laser, patients received either PRK or LASIK using a single pass, multizone excimer laser ablation, Computer-assisted videokeratography was performed at designated postoperative examinations. Main Outcome M easures: Videokeratography maps at 1 and 3 months after surgery were c lassified using a standard classification scheme, The association of t opography patterns to loss of spectacle-corrected visual acuity was te sted. Results: At 1 month, for the PRK (n = 60) and LASIK (n = 51) gro ups, respectively, 63.3% and 19.6% of eyes fell into one of the four o ptically irregular groups (central island, keyhole, semicircular, or i rregularly irregular; P < 0.001), At 3 months, for the PRK (n = 49) an d LASIK (n = 39) groups, respectively, 36.7% and 10.3% of eyes fell in to one of the optically irregular groups (P = 0.004), Comparing the 1- and 3-month examination results in the PRK and LASIK groups, respecti vely, 19 (42%) of 45 eyes and 11 (31%) of 36 eyes had a change in topo graphy, generally to an optically smoother pattern. The irregular grou ps, taken together, were associated with a greater tendency toward los s of spectacle-corrected visual acuity of two or more Snellen lines (P = 0.01), There also was greater tendency toward loss of spectacle-cor rected visual acuity in the PRK group that diminished with time (P < 0 .01 al 1 month, P = 0.05 at 3 months). Conclusions: After treatment fo r moderate-to-high myopia, LASIK topography patterns generally are mor e regular than are PRK patterns. This may be a result either of maskin g of underlying topography perturbations by the lamellar corneal flap, thus mitigating induced topography changes, or differences in surface wound healing. This study suggests that more rapid return of spectacl e-corrected visual acuity found in patients treated with LASIK may be a result of more regular topography patterns early in the postoperativ e course.