Persistent Corneal Haze after Excimer Laser Photokeratectomy in Plasminogen-Deficient Mice

PURPOSE. Excimer laser photorefractive keratectomy creates a nonvascular wound of the cornea. Fibrin deposition and resolution after excimer laser photokeratectomy were investigated in relation to corneal repair and restoration of clarity in mice with a genetic deficiency of plasminogen. METHODS. A Summit Apex Laser (Summit, Waltham, MA) was used to perform 2-mm, 175-pulse, transepithelial photoablations that resulted in deep stromal keratectomies. Photokeratectomy was performed on the corneas of plasminogen-deficient (Plg -/- ) mice and littermate control animals. Eyes were examined for re-epithelialization and clarity throughout the 21-day observational period. Histologic sections were taken during the observational period and fibrin(ogen) was detected immunohistochemically. RESULTS. Reepithelialization was rapid and complete within 3 days in both control and Plg -/- animals. Exuberant corneal fibrin(ogen) deposition was noted in Plg -/- mice and sparse fibrin(ogen) deposition in control mice on days 1 and 3 after injury. Fibrin(ogen) deposits resolved in control mice but persisted in Plg / mice (74% of eyes at 21 days; P < 0.004). Corneal opacification, scarring, and the presence of anterior chamber fibrin(ogen) occurred in plasminogen-deficient mice but not in control mice. CONCLUSIONS. Fibrin(ogen) deposition occurs during corneal wound repair after photokeratectomy. Impaired fibrinolysis in Plg -/- mice caused persistent stromal fibrin deposits that correlated with the development of corneal opacity.