This study investigates the effects of prolonged oral antiviral treatment on complications related to Herpes Zoster Ophthalmicus (HZO). HZO is an eye condition caused by the varicella-zoster virus, which can lead to painful skin rashes and eye problems. The study aims to see if the antiviral treatment can reduce issues like dendriform epithelial keratitis, stromal keratitis, endothelial keratitis, iritis, or postherpetic neuralgia compared to a placebo. Dendriform epithelial keratitis is an infection of the cornea, while stromal and endothelial keratitis affect different layers of the cornea. Iritis is inflammation of the iris, and postherpetic neuralgia is a painful condition affecting nerve fibers and skin.

Participants in the study will receive either the investigational antiviral medication or a placebo. A placebo is an inactive substance that looks like the investigational medication but does not contain any medicine. The study will compare outcomes between the two study arms to determine the effectiveness of the antiviral treatment in reducing HZO complications.

• Who can participate: Adults diagnosed with Herpes Zoster Ophthalmicus (HZO) in one eye are eligible to participate. Individuals with a diagnosis of leukemia or lymphoma, or those who have received chemotherapy in the past three months, are excluded from the study.
• Study details: Participants will be assigned to receive either an oral antiviral treatment or a placebo. The study will monitor the effects of the treatment on eye complications associated with HZO.