Effect of ethanol-treated mid-peripheral epithelium on corneal wound healing in rabbits

BACKGROUND To determine the effect of an ethanol-treated mid-peripheral epithelium on wound healing of the corneal epithelium. METHODS Epithelial removal was performed on 18 rabbit eyes, which were divided into three groups of six eyes each as follows: group 1, an 8.0-mm diameter treated with balanced salt solution (BSS) and an 8.0-mm removal; group 2, an 8.0-mm diameter treated with 20% ethanol for 30 seconds and an 8.0-mm removal; and group 3, a 9.0-mm diameter treated with ethanol and an 8.0-mm removal (barrier zone setting group). The corneal defect area was analyzed post-operatively. The concentrations of vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) in tears were determined pre-operatively and post-operatively. Healed corneal tissues were examined with light and electron microscopy. Immunohistochemical analysis was also performed to estimate the expression of EGF receptors in healed corneal tissue. RESULTS The epithelial healing rate in group 3 was faster than that in the two other groups (p < 0.05). The expression of VEGF and EGF in group 3 was higher than that in the other two groups (p < 0.05). Light microscopy revealed clear healing of the corneal epithelium in all groups except for some cases in group 1. Electron microscopy revealed a relatively intact microstructure of the healed corneal tissues, especially in group 2 and 3 when compared with group 1. Meanwhile, in the immunohistochemistry, group 3 showed significantly higher expression of EGFR when compared with the other groups. Furthermore, EGFR expression had a tendency to be stronger in the mid-peripheral corneal area than in the central corneal area. CONCLUSIONS The preserved mid-peripheral epithelial layer treated with ethanol (barrier zone) promoted corneal epithelial healing. It appeared to be correlated with elevated tear VEGF and EGF levels in the post-operative period.