 Patients with herpes zoster keratitis will be enrolled in the study. All patients will receive oral anti-viral medication as a standard-of-care therapy. The patients will be randomized into two groups and given either the study drug or the placebo at the time of enrollment. The patients will come for weekly visits during which slit lamp photograph of the dendrite will be taken. At week 2, if the dendrite has not healed the drug will by unmasked and rescue therapy will be given. the patients will be examined at week 1, 2, and 3 or until resolution occurs. 