A healthy 56-year-old man developed left-sided herpes zoster ophthalmicus, accompanied initially by ipsilateral anterior uveitis and increased intraocular pressure. Although he was treated in the subacute phase (5 days after skin eruption) with adequate oral doses of acyclovir for 10 days, the condition was later complicated by a left sectorial anterior ischemic optic neuropathy. The pathogenesis of this rare complication is discussed in this article.