EFFECT OF CORTICOSTEROIDS ON RABBIT CORNEAL KERATOCYTES AFTER PHOTOREFRACTIVE KERATECTOMY

BACKGROUND: To determine the corticosteroid effect on the activity and repopulation of keratocytes after photorefractive keratectomy (PRK). METHODS: A 193-nm excimer laser (VISX Twenty/Twenty) created a central ablation depth of 22 mu m (diameter: 5 mm) on 22 corneas of 16 albino rabbits. Two ablated eyes were examined 6 hours following PRK. Twelve eyes received no postoperative corticosteroids and eight were treated with topical fluoromethalone for 3 months. Corneas were examined 1, 3 , 6, and 12 months after PRK by immunofluorescence and transmission el ectron microscopy. RESULTS: Corticosteroids reduced haze (p=0.02), but all corneas (treated or untreated) cleared 6 months after PRK. Kerato cytes were absent from the anterior 100 mu m of the stroma 6 hours aft er PRK. However, the number acid activity of keratocytes were signific antly greater in this area in untreated corneas at 1 month and then gr adually decreased. By 6 and 12 months, the number of keratocytes appro ached controls, Treated corneas had fewer keratocytes than either cont rols or untreated eyes (p<0.01) and by 3 months, a subepithelial acell ular zone of 30 to 50 mu m thickness appeared and persisted until at l east 12 months after PRK. CONCLUSIONS: Corticosteroids have a transien t effect in reducing haze and seem to inhibit keratocyte movement, lea ding to an acellular subepithelial region beneath the ablated area.