Rare bilateral optic neuritis following herpes zoster ophthalmicus in an immunocompetent adult: A case report.

Background: Herpes zoster ophthalmicus is caused by reactivation of varicella-zoster virus in the ophthalmic division of the trigeminal nerve. Optic neuritis is an uncommon but vision-threatening complication, and bilateral optic nerve involvement in immunocompetent individuals is exceptionally rare. Case presentation: A 40-year-old immunocompetent man presented with acute right frontal and periorbital pain followed by a vesicular rash in the right ophthalmic division, including Hutchinson's sign. Initial visual acuity was normal, and oral valacyclovir was started. Within days, he developed rapidly progressive visual loss in the right eye with optic disc edema and right optic nerve enhancement on orbital magnetic resonance imaging. Cerebrospinal fluid analysis and systemic autoimmune and infectious workups were unrevealing. After admission, oral valacyclovir was switched to intravenous acyclovir, and oral corticosteroid therapy was initiated. On the following day, visual acuity in the right eye declined to light perception, and the previously unaffected left eye developed decreased visual acuity, impaired color vision, and visual field defects. Corticosteroid treatment was therefore escalated to intravenous methylprednisolone pulse therapy. Because of subsequent bilateral visual deterioration, intravenous immunoglobulin was added and administered for 5 days. Despite partial radiologic improvement, vision in the right eye progressed to permanent no light perception. Left eye visual acuity partially recovered to 0.9 (approximately 20/22 Snellen) at follow-up. Conclusion: This case highlights the fulminant course of herpes zoster ophthalmicus-associated optic neuritis and shows that bilateral optic nerve involvement may occur even in immunocompetent patients. Early recognition, close monitoring of both eyes, and prompt escalation of therapy are critical when optic nerve involvement is suspected.