Abstract
Abstract: :
Purpose: The number of nerve fibers in the cornea decreases after the nerves are disrupted by photorefractive procedures. In this study, we evaluated the number and distribution of nerve fiber bundles in human central corneas before and up to one year after LASIK. Methods: Seventeen eyes were studied from 11 patients who had received LASIK to correct myopia from -2.0 D to -11.0 D. Eyes were treated with a VISX Star excimer laser with a planned 180-µ m flap. Central corneas were scanned throughout their full-thickness by confocal microscopy (Tandem Scanning, Reston, VA) before, and at 1, 3, 6, and 12 months after LASIK. Nerve fiber bundles appeared as bright, well-defined, linear structures that were sometimes branched and usually appeared in several consecutive frames. These structures were identified and counted by one observer in 259 scans. The average number of nerve fiber bundles in 1 to 6 scans per eye per visit was determined in the subbasal region, in the full-thickness stroma, in the stromal flap (distance from the most anterior keratocyte to the flap interface), and in the stromal bed (distance from the flap interface to the endothelium). Median numbers of nerve fiber bundles in each region at each observation time were compared by using Friedman's test for non-parametric repeated measures analysis of variance. Significant differences were investigated by adjusting for multiple comparisons by using the Student-Newman-Keuls procedure. Results: Table: Median of average number of nerve fiber bundles per scan. ^ All were significantly different from each other except 1 month versus 3 months. * All times post-op were significantly different from pre-op. Post-ops were not significantly different from each other. Conclusion: In the corneal flap, the number of subbasal and stromal nerves decrease immediately after LASIK. During the first year post-LASIK, subbasal nerve fiber bundles return, although by 1 year their number remains less than half what it was before LASIK.
Keywords: 471 microscopy: confocal/tunneling • 441 innervation: neural regulation • 548 refractive surgery: LASIK