Reinnervation in the Cornea After LASIK

A recent study by the Mayo Clinic’s Department of Ophthalmology (Rochester, Minn.) showed that the number of subbasal and stromal nerve fiber bundles in the corneal flap decreases by 90 percent immediately after laser in situ keratomileusis (LASIK). During the first year after LASIK, subbasal nerve fiber bundles gradually return, but by 1 year the number remains less than half of the number before LASIK.

Researchers evaluated the denervation and reinnervation of human central corneas using sequential, quantitative measurements of nerves viewed by confocal microscopy in vivo during the first year after LASIK. They studied 17 eyes of 11 patients who had undergone LASIK to correct myopia from -2.0 D to -11.0 D; eyes were treated with an excimer laser with a planned 180-microm flap. Clinicians scanned central corneas throughout their full thicknesses by confocal microscopy before and at 1 week and 1, 3, 6 and 12 months after LASIK. They determined the number of nerve fiber bundles per scan in two to eight scans per eye per visit in the subbasal region, the full-thickness stroma, the stromal flap (layer between the most anterior keratocyte and the flap interface) and the stromal bed (layer between the flap interface and the endothelium).

In the subbasal region, the number of nerve fiber bundles decreased by more than 90 percent 1 week after LASIK and was significantly lower at all times after surgery than before. It increased 6 and 12 months after LASIK, but remained less than half of the preoperative value. In the stromal flap, the number of nerves at all times after surgery was also significantly lower than before surgery and did not increase significantly by 1 year. In the stromal bed, researchers found no significant differences among any of the nerve measurements before and after LASIK.

SOURCE: Lee BH, McLaren JW, Erie JC, et. al. Reinnervation in the cornea after LASIK. Invest Ophthalmol Vis Sci 2002;43(12):3660-64.