Composing the puzzle: a case of acute unilateral vision loss
Authors: Fabiani Claudia , Spadavecchia Giulia , Guidetti Giorgia , Marigliani Davide , Tosi Gian Marco 
Published: January 2025

A 75‐year‐old Caucasian male, with a medical history of hypertension, diabetes, and dyslipidemia, presented to the emergency department with sudden complete vision loss in his left eye (LE). Ophthalmological examination revealed absence of light perception, a relative afferent pupil defect, and mild nuclear cataract with normal intraocular pressure. Fundoscopy indicated optic disc edema, retinal arteriolar narrowing, venous tortuosity, macular whitening, a foveal cherry‐red spot, and scattered hemorrhages in the peripheral retina and vitreous turbidity. Right eye (RE) had a best corrected visual acuity (BCVA) of 20/30, with mild nuclear cataract as the only anomaly. Spectral domain optical coherence tomography (SD‐OCT) of the RE displayed hyperreflective inner retinal layers, intra‐ and subretinal fluid, hyperreflective vitreous structure, and irregular preretinal formations. Fluorescein angiography indicated retinal non‐perfusion, suggesting combined central retinal artery and vein occlusion (CCRAVO). Fast‐track protocol for excluding Giant Cell Arteritis was initiated, followed by extensive assessment for non‐arteritic central retinal artery occlusion, which yielded unremarkable results except for preexisting medical conditions and risk factors.

Two weeks later, the patient returned with reduced visual acuity in RE. BCVA was 20/40 with fundoscopy revealing creamy focal opacities at posterior pole and mid‐periphery, and vitreous haze. SD‐OCT of lesions showed full‐thickness hyperreflectivity and disruption of retinal layers. LE exhibited mild anterior uveitis, inflammatory vitreous cells, and necrotic areas in peripheral and mid‐peripheral retina. Bilateral acute retinal necrosis (ARN) was suspected, confirmed via polymerase chain reaction (PCR) analysis of aqueous humor from LE, detecting varicella‐zoster virus (VZV).

Hospitalized, the patient received intravenous acyclovir and intravitreal foscarnet for new peripheral lesion in RE. Oral glucocorticoids were introduced. At one‐month follow‐up, vitreous inflammation resolved, retinal lesions healed, and atrophy ensued in both eyes. Retinal thinning and schisis‐like separations were observed in LE. Oral acyclovir and gradual tapering of glucocorticoids continued. Nine months post‐onset, RE BCVA improved to 20/30, and patient received prophylactic oral acyclovir. One year later, cataract surgery was performed on the RE, resulting in a BCVA improvement to 20/20.

This case highlights challenges in diagnosing herpetic ARN, evident only upon retinal necrosis. Isolated CCRAVO, though rare, may suggest VZV occlusive vasculitis. ARN's exact mechanism remains uncertain; Kyrieleis vasculitis suggests immune‐mediated process. (1,2) Comorbidities may predispose to central retinal vascular events within ARN. Comprehensive ophthalmological follow‐up is crucial, especially with early features like vitreous involvement and inflammatory precipitates. (3,4) Increased awareness of ARN's potential sight‐threatening effects on ocular vasculature aids timely identification.

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