INFLAMMATORY CELLS, REFRACTIVE REGRESSION, AND HAZE AFTER EXCIMER-LASER PRK

OBJECTIVE: To examine the role of inflammatory cell invasion and aspec ts of tissue reaction on refractive regression and corneal haze after myopic PRK in rabbits. METHODS: Measurements were made for 12 weeks po stoperatively of haze intensity, corneal topography, tear cytology, in flammatory cell invasion, subepithelial fibroblast density, and the th ickness of the newly laid down connective tissue and of the regrown ep ithelium. RESULTS: Inflammatory cell invasion could be prevented by fi tting a soft contact lens, but this had no effect on the haze or the r egression. Haze intensity correlated with subepithelial fibroblast pro liferation but not with new connective tissue formation or epithelial hyperplasia. Neither connective tissue nor epithelium regrew in the fo rm of a lens and thus they could not account for regression, Intensive treatment with corticosteroids resulted in a marked reduction in post operative haze and a slight lessening of long-term regression. Corresp ondingly, it reduced fibroblast proliferation. CONCLUSIONS: Haze appea rs, at least in part, to be a result of fibroblast proliferation. Regr ession is possibly caused by slow distortion of existing tissue rather than the growth of new.