Recovery of corneal subbasal nerve density after PRK and LASIK

PURPOSE: To measure and compare the return of corneal innervation up to 5 years after photorefractive keratectomy (PRK) and laser in situ keratomileusis (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 16 eyes of 11 patients received LASIK to correct a mean refractive error of -6.56 +/- 2.44 diopters. Corneas were examined by confocal microscopy before and at 1, 2, 3, and 5 years after the procedures. Subbasal nerve fiber bundles were measured to determine density (visible length of nerve/frame area) and expressed as micrometers per square millimeters. Differences were compared by Friedman's test and adjusted for multiple comparisons by the Student-Newman-Keuls procedure. RESULTS: After PRK, mean subbasal nerve density was reduced by 59% at 1 year (2764 +/- 1321 mu m/mm(2) [+/- SD]) when compared with preoperative (6786 +/- 1948 mu m/ mm(2); P <.001). By 2 years, subbasal nerve density (6242 +/- 1763 mu m/mm(2)) was not significantly different from density before PRK and remained unchanged to 5 years (5903 3086 ILm/mm 2). After LASIK, subbasal nerve density was reduced by 51%, 35%, and 34% at 1, 2, and 3 years, respectively (P <.001). By 5 years, subbasal nerves had returned to densities (4441 +/- 2819 mu m/mm(2)) that were not significantly different from densities before LASIK (5589 +/- 2436 mu m/mm(2)). CONCLUSION: Corneal subbasal nerve density does not recover to near preoperative densities until 5 years after LASIK, as compared with 2 years after PRK.