Seasonality of Acute Retinal Necrosis

Purpose: To study the seasonal variability in the occurrence of acute retinal necrosis (ARN) in a series of polymerase chain reaction (PCR)-positive patients. Methods: Consecutive patients clinically diagnosed with ARN and a positive PCR result of aqueous humor during a seven-year period were studied retrospectively. Patients’ demographics, causative viral agent(s), and the date of disease onset were extracted from medical records. Results: Twenty eyes of 20 patients were enrolled; the mean age at presentation was 39.6 ± 14.4 (range, 6–62) years. Nine patients were female. The most common causative agent was varicella-zoster virus in 16 patients (80%), followed by herpes simplex virus in two patients (10%). The disease onset was in winter in 10 patients (50%), and the highest incidence was in February (five patients, 25%). The cumulative occurrence of ARN was significantly higher in the first half of the year (winter and spring) compared to the second half of the year (summer and fall) (P = 0.030). In general, seasons with a high incidence of ARN were preceded by cold seasons. Conclusion: In our series, we observed seasonal variability in the incidence of ARN, with the highest incidence during winter and spring. However, further epidemiologic studies in different geographical areas are required to elucidate the true seasonal nature of ARN.