Quantitative aqueous PCR viral load predicts poor visual outcome in acute retinal necrosis

Background/aims Acute retinal necrosis (ARN) is a rare herpetic uveoretinitis that frequently results in severe vision loss. Evidence from large single-centre cohorts remains limited. We evaluated clinical characteristics and prognostic factors in 148 ARN cases. Methods We retrospectively reviewed 148 consecutive patients with ARN treated at a tertiary referral centre (1985–2021). Causative virus and aqueous viral DNA copy number at presentation were determined by PCR. Associations of final best-corrected visual acuity (BCVA, logMAR) with aqueous viral load, timing of antiviral initiation and extent of retinal necrosis (quadrants involved) were analysed. Quantitative aqueous viral-load data were available in 73 of 148 patients. Results Varicella-zoster virus accounted for 125/148 (84.5%) cases; herpes simplex virus (HSV-1) for 16 (10.8%) and HSV-2 for 7 (4.7%). Mean age at onset was 50.8 years. Mean interval from symptom onset to antiviral initiation was 11.5±7.0 days; median interval from onset to vitrectomy was 22 days. Mean BCVA worsened from 0.71 logMAR at presentation to 1.20 logMAR at final visit (p<0.0001). Higher aqueous viral DNA copy number correlated with poorer final BCVA (p<0.001). Greater retinal involvement (more quadrants affected) was also associated with poorer final BCVA (p<0.0001). The interval from onset to antiviral initiation showed a weak, non-significant trend with final BCVA (p=0.055). Conclusions In this large single-centre cohort of ARN, higher aqueous viral load and greater retinal involvement were associated with worse visual outcome. Quantitative viral load assessment at presentation may support risk stratification and timely selection of optimal interventions.