To report a case of unilateral acute retinal necrosis (ARN) following herpes simplex virus (HSV) encephalitis.

A 19-year-old man previously diagnosed with HSV encephalitis presented with a headache and visual loss in his left eye. On the initial visit, slit-lamp examination showed conjunctival injection and inflammatory cells (3+) in the anterior chamber of the left eye. Funduscopic examination showed optic disc swelling, multiple yellow-whitish spots in the peripheral retina and retinal vascular sheathing. After the patient was diagnosed with ARN, intravenous acyclovir (1,500 mg/m²/day) was administered. Because retinal detachment and multiple retinal breaks were found during the treatment period, the authors performed barrier laser treatment in the peripheral retina. At that time, no retinal necrosis was observed in the patient's right eye. The retinal lesions regressed, and no new retinal lesion was observed in the left eye, during the follow-up period.

We report a case of ARN in a patient with HSV encephalitis. Ophthamologist should perform a thorough ophthalmic examination in a patient diagnosed with HSV encephalitis.