All subjects undergo microbiological analysis of the corneal ulcer upon intake into the study. A spatula is applied to the cornea of the affected eye(s) and blood agar and chocolate agar plates and brain heart infusion broth (BHI) are streaked for each patient. Cultures are repeated daily until two negative cultures are obtained. If the cultures are positive for any organism, that organism is considered the infecting agent. Each culture plate is incubated for at least seven days and the colony forming units are differentiated and enumerated by standard bacteriological techniques, including the VPI technique for anaerobic bacteria. No culture growth at seven days constitutes a negative culture.