Abstract
Abstract: :
Purpose: In an earlier study we demonstrated a 90% loss of subbasal nerve density within the first year after LASIK (Lee et al. IOVS 2002; 43:3660-3664.). In this study we measured the return of innervation to the cornea 2 and 3 years after laser in situ keratomileusis (LASIK). Methods: Seventeen corneas of 11 patients who had undergone LASIK (planned 180-µm flap) to correct myopia from –2.0 D to –11.0 D were examined by using confocal microscopy before, and at 1, 2, and 3 years after surgery. In all available scans, we estimated the number of visible nerve fiber bundles, their mean angle, and their depth in the cornea. Changes in these variables were examined by using the Friedman test and confirmed by Generalized Estimating Equation models. Results: The number of visible subbasal nerves per exam that initially decreased by 90% from 3.4 (2.5, 5.3) [median (interquartile range)] before LASIK returned to 1.5 (0.3, 3.3) at 1 year (p=0.03) and increased to numbers that were not significantly different from preoperative numbers at 2 years [2.5 (1.5, 4.5)] and at 3 years [2.3 (1.5, 3.5)]. The number of visible stromal nerves per exam decreased (p=0.02) from 2.3 (2.0, 2.6) before LASIK to 1.0 (0.5, 1.5) at 1 year and 1.0 (0.5, 1.5) at 2 years after LASIK. By 3 years, the number of stromal nerves increased to 1.5 (1.0, 2.0) and was not significantly different from numbers before LASIK. Conclusions: Corneal nerves that are lost within the first year after LASIK gradually return, by 2 years in the subbasal layer and by 3 years in the stroma, to numbers not significantly different from numbers before LASIK.
Keywords: cornea: clinical science • refractive surgery: LASIK • microscopy: confocal/tunneling