Retinal Zones Used as a Treatment Strategy in Management of Acute Retinal Necrosis and the Lessons Learnt: A Retrospective Study

Purpose: To use retinal zones and clock hours of involvement to plan treatment of acute retinal necrosis (ARN) during the induction phase. Design: Retrospective study. Methods: Medical records at two branches of our tertiary centre of patients with ARN were analysed. Inclusion criteria were treatment started at our centre and regular follow-up. Exclusion criteria were cases with doubtful diagnosis, irregular follow-up, and pre-existing ocular diseases causing low best corrected visual acuity (BCVA). Our standard protocol was oral valacyclovir 1000 mg TID, with intravitreal ganciclovir and oral prednisolone. However, we treated more aggressively with large areas of necrosis. Results: Thirty patients and 36 eyes were included. The mean age was 44.97 ± 13.87 years (range 18–75 years). Males and females were 50% (15/30 patients) each. The retinal involvement was: Zone 1, 11.1% (4/36 eyes), Zone 2 41.7% (15/36 eyes), and Zone 3 47.2% (17/36 eyes). 27/36 eyes (75%) had ≤6 clock hours of retinitis. 83.3% (25/30) of patients were started on 1000 mg TID of oral valacyclovir at induction. The median time to initial response was 14 days for Zone 3, 30 days for Zone 2, and 45 days for Zone 1. This was statistically significant ( P = 0.038); however the time to complete healing was not significant ( P = 0.098). There was no statistically significant correlation between zone of involvement ( P = 0.566) and clock hours of retinitis ( P = 0.661) with incidence of rhegmatogenous retinal detachment. 4/36 eyes (11.1%) had active retinitis at final visit. Final BCVA was better in eyes with ≤6 clock hours of retinitis ( P = 0.002). Conclusion: Planning management based on zones of retinal involvement and extent of clock hours of retinal necrosis may result in improved outcomes.