EFFECTS OF 50-PERCENT ETHANOL AND MECHANICAL EPITHELIAL DEBRIDEMENT ON CORNEAL STRUCTURE BEFORE AND AFTER EXCIMER PHOTOREFRACTIVE KERATECTOMY

Purpose, The corneal epithelium is generally removed before photoablat ion in photorefractive keratectomy (PRK) because laser transepithelial PRK may result in surface irregularity caused by variability in epith elial thickness and differing ablation rates between epithelium and st roma. We compared the effects of mechanical deepithelialization with c hemical epithelial removal by using 50% ethanol on the corneal structu re. Methods, Fourteen rabbits underwent corneal deepithelialization by using a blade in the left eye and 24 h later in the right eye. Anothe r 14 rabbits underwent corneal deepithelialization by using 50% ethano l solution. Half of the eyes treated with each technique underwent PRK after deepithelialization. Pachymetry was performed before and after each procedure on right eyes. Keratocyte and neutrophil densities were assessed by light microscopy. Results, Among non-laser-treatment grou ps, eyes that underwent mechanical deepithelialization had decreased c orneal thickness (p = 0.001), increased keratocyte densities (p = 0.03 ), and no significant difference in neutrophil densities (p = 0.91) co mpared with chemically treated eyes 24 h after surgery. Among laser-tr eatment groups, eyes that underwent mechanical epithelial removal had increased keratocyte densities (p = 0.001), decreased corneal thicknes s (p = 0.03), and increased neutrophil densities (p = 0.03) 24 h after surgery compared with chemically treated eyes. Conclusion. Deepitheli alization with 50% ethanol causes more keratocyte loss with perhaps mo re corneal edema, but less stromal influx of neutrophils, than does a mechanical technique 24 h after PRK in a rabbit model. Corneal deepith elialization with dilute ethanol may be a viable option in PRK. Howeve r, further investigation into the safety of this technique is warrante d before it can be widely applied clinically.