CORNEAL ENDOTHELIAL STATUS 12 TO 55 MONTHS AFTER EXCIMER-LASER PHOTOREFRACTIVE KERATECTOMY

Purpose: To investigate the long-term effect (range, 12-55 months) of photorefractive keratectomy (PRK) on the human corneal endothelium. Methods: Specular microscopy of the central corneal endothelium was performed on 106 patients who underwent PRK to correct myopia. The duration of follow-up varied from 12 to 55 months (mean, 33 months; median, 37 months). Patients were divided in two groups: group 1 included 32 patients (35 treated eyes) with preoperative and postoperative central endothelial images; group 2 included 26 patients from group 1 and 74 additional patients with postoperative central endothelial images of the treated and untreated fellow eyes. Results: In group 1, preoperative and postoperative values were as follows: mean cell density (+/- standard deviation), 2950 +/- 329 cells/mm(2) and 2907 +/- 337 cells/mm(2), respectively (P = 0.43); polymegathism index, 0.29 +/- 0.06 and 0.28 +/- 0.05, respectively (P = 0.38); pleomorphism index, 65.8% +/- 5.6% and 64.2% +/- 5.6%, respectively (P = 0.22); figure coefficient index, 0.86 +/- 0.05 and 0.87 +/- 0.02, respectively (P = 0.20). In group 2, postoperative values of the treated and untreated eyes were as follows: mean cell density, 2912 +/- 363 cells/mm(2) and 2922 +/- 434 cells/mm(2), respectively (P = 0.86); polymegathism index, 0.28 +/- 0.05 and 0.30 +/- 0.08, respectively (P = 0.04); pleomorphism index, 64.93% +/- 17.49% and 64.07% +/- 8.31%, respectively (P = 0.45); figure coefficient index, 0.88 +/- 0.03 and 0.88 +/- 0.03, respectively (P = 0.79). Conclusions: Photorefractive keratectomy caused no damage to the central corneal endothelium. Polymegathism differences in treated and untreated eyes could be attributed to modifications in corneal metabolism or to a yet unknown mechanism.