Corneal Healing Following Laser Refractive Keratectomy

A 193-nm excimer laser system was used to ablate 4.5-mm optically contoured zones in the corneal stroma of rabbits to achieve optical flattening of 2, 4, 8, and 16 diopters. We studied the effect of edge profile and wound depth on reepithelialization and stromal remodeling using dichlorotriazinyl aminofluorescein, a vital dye that covalently binds to the stromal bed and delineates the boundaries of new collagen synthesis. All the corneas reepithelialized; no subsequent recurrent erosions occurred. All seven corneas that received an ablation of less than 50 μm were clear centrally at 8 weeks. At an ablation depth of approximately 100 μm, opacification and scarring were observed biomicroscopically and histopathologically in two specimens. No evidence of new collagen formation or epithelial hyperplasia was found in any of the seven corneas that remained clear. Stromal remodeling was observed in the two corneas that exhibited scarring.