Determination of the Nerve Growth Factor Level in the Central Cornea After LASIK and Epi-LASIK Treatment in a Rabbit Model System

Abstract

Corneal refractive surgery results in nerve damage. Nerve regeneration is a complex process that involves nerve growth factor (NGF). Here, a comparative study was conducted to determine the NGF level in the central cornea after laser in situ keratomileusis (LASIK) and epipolis laser in situ keratomileusis (epi-LASIK) treatment. Twenty-four New Zealand white rabbits underwent randomly assigned epi-LASIK treatment on 1 eye and LASIK treatment on the other eye. Experimental animals were sacrificed 1 day, 3 days, 7 days, and 1 month after treatment, and the NGF level was determined by immunohistochemistry and Western blot analyses. Statistical analyses were performed using a Student t test (P < 0.05). Immunohistochemical staining demonstrated a weak NGF signal in the cornea of control and LASIK-treated rabbit eyes. After epi-LASIK treatment, the level of NGF increased significantly in the epithelial layer at the 1- and 3-day time point, and returned to control levels 7 days after treatment. Western blot analyses showed that the NGF level was significantly lower after LASIK treatment as compared to epi-LASIK treatment, 1 day and 3 days after treatment (t = -6.50, -5.85; P = 0.023, 0.028), with no significant difference between the two groups at the 7-day and 1-month time points (P > 0.05). This study demonstrates for the first time that the NGF level in the central corneal epithelial layer of rabbit eyes is significantly increased early after epi-LASIK treatment in contrast to LASIK treatment, and decreased to control levels 1 week after treatment.