CAN ZINC PREVENT APOPTOSIS OF ANTERIOR KERATOCYTES AFTER SUPERFICIAL KERATECTOMY

Objective, To determine whether zinc, which blocks apoptosis in many s ystems, including in leukemic cells and possibly in retinal dystrophie s, can prevent the unwanted loss of anterior stromal keratocytes after superficial keratectomy. Methods, After mechanical central corneal ep ithelial debridement, the left eyes of nine New Zealand white rabbits were treated with 25 mM zinc chloride (ZnCl2) in Earle's salts minimal essential medium (MEM) either every 30 min (n = 3), every 2 h (n = 3) , or every 4 h (a = 3). The left eyes of nine additional animals, divi ded into three equal groups, were deepithelialized, and each received pure culture medium at one of the same three frequencies. One eye of e ach of another six rabbits was deepithelialized but received no drops. After 24 h, all 24 animals were sacrificed and the globes were enucle ated. The corneas were processed and sections were stained with hemato xylin and eosin. Results, The cell count of MEM-treated corneas exceed ed that of untreated corneas (p = 0.03, analysis of variance [ANOVA]), but there was no difference among eyes that received the different fr equencies of MEM application (p = 0.36, ANOVA). Cell counts increased with frequency of zinc application, but the differences were not stati stically significant (p = 0.09, ANOVA). Only in the group receiving th e most frequent zinc applications were superficial keratocytes retaine d. This group also possessed a greater number of stromal keratocytes t han untreated controls and MEM-treated corneas (p = 0.01). Conclusions , At a significantly high dosage, zinc can prevent loss of superficial keratocytes to a greater extent than culture medium alone can. Moreov er, zinc has the advantage of preserving the most anterior layer of ke ratocytes. Retention of these cells may prevent the reactive overproli feration that constitutes haze after photorefractive surgery.