Effect of nerve growth factor eye drops on corneal nerve regeneration in rabbits after LASIK

Abstract

Objective To investigate the effect of nerve growth factor (NGF) eye drops on central corneal nerve regeneration in rabbits after laser in situ keratomileusis (LASIK). Methods This was a experimental study. Fifteen New Zealand white rabbits were randomly assigned to one of three groups: NGF-treatment group, artificial tears hycosan-treatment group (positive control group), and normal saline-treatment group (negative control group) with five rabbits in each group, one drop every time and three times per day. The nerve density and the number of central corneal sub-basal and stromal cells were measured by confocal microscopy and were compared before surgery and at 1 week, 1 month, and 3 months after surgery.Analysis of variance was used for comparing the differences at different time points and among the three groups. Results The respective preoperative sub-basal nerve densities (SNDs) in the negative control group, positive control group, and NGF treatment group were 10 801±3 331 μm/mm2, 11 619±3 932 μm/mm2, and 12 299±2 622 μm/mm2. The number of corneal sub-basal nerve fibers were 12.2±3.4, 11.6±2.7, and 13.1±2.7 in the respective groups. In the preoperative corneas, the corneal stromal nerve densities were 7 258±1 242 μm/mm2, 8 148±2 462 μm/mm2, 8 984±1 526 μm/mm2, and the number of corneal stromal nerve fibers were 8.5±1.4, 8.9±2.6, 10.1±2.1 in the respective groups. Compared with preoperative values, nerve parameters in all groups increased at 1 week postoperatively (P<0.01). Compared with 1 week postoperative, SNDs and corneal stromal nerve densities in the NGF group increased at 1 month, while the control groups increased at 3 months (P<0.01). The number of sub-basal corneal nerve fibers in all three groups increased at 3 months (P<0.05). The number of corneal stromal nerve fibers increased at 1 month compared with 1 week postoperative in the NGF group and the positive control group (P<0.05). However there were no significant changes in the number of corneal stromal nerve fibers between pre-and postoperative 1 and 3 months measurements. Conclusion NGF eye drops promote corneal nerve repair at different periods following LASIK in rabbit eyes. Key words: Keratomileusis, laser in situ; Nerve growth factor; Corneal nerve regeneration