ASPIRIN THERAPY IN NONARTERITIC ANTERIOR ISCHEMIC OPTIC NEUROPATHY

PURPOSE: To determine the benefit of aspirin in reducing the risk of n onarteritic anterior ischemic optic neuropathy in the fellow eye follo wing its occurrence in the first eye. METHODS: A retrospective cohort study was conducted on 431 patients, 153 of whom were and 278 of whom were not prescribed aspirin following the development of unilateral no narteritic anterior ischemic optic neuropathy. RESULTS: The 2-year cum ulative probability of nonarteritic anterior ischemic optic neuropathy in the fellow eye was 7% in the aspirin group and 15% in the no-aspir in group, and 5-year cumulative probabilities were 17% and 20%, respec tively. Compared with the no-aspirin group, the rate ratio for nonarte ritic anterior ischemic optic neuropathy in the fellow eye in the aspi rin-user group was 0.43 (95% confidence interval, 0.19 to 0.92) over t he first 2 years and 0.68 (95% confidence interval, 0.36 to 1.26) over the 5-year period. The overall calculated 5-year risk was 19%; howeve r, if none of the patients with incomplete follow-up developed nonarte ritic anterior ischemic optic neuropathy in the fellow eye, then the 5 -year risk would be about 12%. CONCLUSIONS: The 5-year risk of nonarte ritic anterior ischemic optic neuropathy occurring in the second eye i s far lower than that reported by previous studies. Our results sugges t a possible short-term but little or no long-term benefit to aspirin in reducing the risk of nonarteritic anterior ischemic optic neuropath y in the fellow eye. However, this finding must be viewed with caution because this study was not conducted prospectively with a controlled protocol.