Am J Ophthalmol. 2006 Mar 15;  

Erie JC, Patel SV, McLaren JW, Hodge DO, Bourne WM.  Department of Ophthalmology (J.C.E., S.V.P., J.W.M., W.M.B.).  

PURPOSE: To measure changes in keratocyte density up to 5 years after PRK and LASIK.  

DESIGN: Prospective, nonrandomized clinical trial.  

METHODS: Eighteen eyes of 12 patients received PRK to correct a mean refractive error of -3.73 +/- 1.30 diopters, and 17 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 diopters. 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 paired t tests with Bonferroni correction for five comparisons.  

RESULTS: After PRK, keratocyte density in the anterior stroma decreased by 40%, 42%, 45%, and 47% at 6 months, 2 years, 3 years, and 5 years, respectively (P < .001). At 5 years, keratocyte density decreased by 20% to 24% in the posterior stroma (P < .05). After LASIK, keratocyte density in the stromal flap decreased by 22% at 6 months (P < .02) and 37% at 5 years (P < .001). Keratocyte density in the anterior retroablation zone decreased by 18% (P < .001) at 1 year and 42% (P < .001) at 5 years. At 5 years, keratocyte density decreased by 19% to 22% (P < .05) in the posterior stroma.  

CONCLUSIONS: Keratocyte density decreases for at least 5 years in the anterior stroma after PRK and in the stromal flap and the retroablation zone after LASIK.