LONG-TERM CORNEAL KERATOCTYE DEFICITS AFTER PHOTOREFRACTIVE KERATECTOMY AND LASER IN SITU KERATOMILEUSIS

Purpose: To measure changes in keratocyte density up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). Methods: This was a prospective, nonrandomized clinical trial. Eighteen eyes of 12 patients received PRK to correct a mean refractive error of –3.73 ± 1.30 D, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of –6.56 ± 2.44 D. Corneas were examined by using confocal microscopy before and 6 months, 1 year, 2 years, 3 years, and 5 years after the procedures. Keratocyte densities were determined in five stromal layers in PRK patients and in six stromal layers in LASIK patients. Differences between preoperative and postoperative cell densities were compared by using Bonferroni-adjusted paired t tests. Results: After PRK, keratocyte density in the anterior stroma was decreased by 39%, 42%, 45%, and 47 % at 6 months, 2 years, 3 years, and 5 years, respectively (P <.001). At 5 years, keratocyte density was decreased by 20 % to 24 % in the posterior stroma (P <.05). After LASIK, keratocyte density in the stromal flap was decreased by 22 % at 6 months (P <.02) and 37 % at 5 years (P <.005). Keratocyte density in the anterior retroablation zone was decreased 18 % (P <.005) at 1 year and 43 % (P <.005) at 5 years. At 5 years, keratocyte density was decreased by 19 % to 22 % (P <.05) in the posterior stroma. Conclusions: Keratocyte density is decreased in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK for up to 5 years. Posterior stromal keratocyte deficits are first noted at 5 years