Herpes Simplex Virus Epithelial Keratitis Trial: HEDS-EKT evaluated the benefit of oral acyclovir given during treatment of an acute HSV keratitis (dendritic or geographic keratitis) in preventing the occurrence of later blinding complications. Patients entered the trial within 7 days of onset. All patients received standard treatment with a topical antiviral and were randomized to receive either oral acyclovir (400 mg five times a day for 21 days) or a placebo. Patients had eight visits within a 12-month followup period. The primary outcome was the time to the first occurrence of stromal keratitis or iridocyclitis in the study eye (eye with epithelial keratitis at time of study entry). The HEDS-EKT recruitment goal was 502 patients.