Fellow-eye herpes simplex virus type 1 uveitis after intravitreal bevacizumab: a case report

Background: Intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy is widely used for neovascular retinal diseases. Intraocular inflammation is a recognized adverse event and typically occurs in the injected eye. Inflammation in the fellow, uninjected eye is exceptionally rare and may be misinterpreted as sterile immune-mediated inflammation, potentially delaying appropriate treatment. We report a case of polymerase chain reaction (PCR)-confirmed herpes simplex virus type 1 (HSV-1) uveitis presenting in the fellow eye shortly after intravitreal bevacizumab administration. Case presentation: An 84-year-old man with well-controlled type 2 diabetes mellitus received intravitreal bevacizumab (1.25 mg) in the left eye for neovascular age-related macular degeneration. Three days later, he developed acute granulomatous anterior uveitis with dense vitritis in the right, uninjected eye, while the treated eye remained quiescent. Best-corrected visual acuity decreased to 20/400. Given the severity of inflammation and limited fundus visualization, viral retinitis was suspected. Empirical systemic valacyclovir and topical corticosteroids were initiated. Aqueous humor PCR detected HSV-1 DNA, confirming herpetic uveitis. Inflammation resolved within 40 days with recovery of visual acuity to 20/20 and no progression to acute retinal necrosis. The patient remained recurrence-free under antiviral prophylaxis at last follow-up. Conclusions: Severe fellow-eye inflammation following intravitreal bevacizumab may reflect viral reactivation rather than sterile inflammation. Early diagnostic evaluation, including aqueous humor PCR when clinically indicated, is essential to guide appropriate therapy and prevent sight-threatening complications.