Reinnervation in the cornea after LASIK.

PURPOSE

Nerve fibers in the cornea are disrupted by photorefractive procedures. In this study, the denervation and reinnervation of human central corneas were evaluated by sequential, quantitative measurements of nerves viewed by confocal microscopy in vivo during the first year after LASIK.

METHODS

Seventeen eyes were studied 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- micro m flap. Central corneas were scanned throughout their full thicknesses by confocal microscopy before and at 1 week and 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. The number of nerve fiber bundles per scan in two to eight scans per eye per visit was determined 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).

RESULTS

In the subbasal region, the number of nerve fiber bundles decreased by more than 90% 1 week after LASIK and was significantly lower at all times after surgery than it was before surgery (P < 0.001). 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 less than before surgery (P < 0.001) and did not increase significantly by 1 year. In the stromal bed, there were no significant differences among any of the nerve measurements before and after LASIK (P = 0.24).

CONCLUSIONS

In the corneal flap, the number of subbasal and stromal nerve fiber bundles decreases by 90% immediately after LASIK. During the first year after LASIK, subbasal nerve fiber bundles gradually return, although by 1 year their number remains less than half of that before LASIK.