Purpose: To determine the benefit of aspirin in reducing the risk of nonarteritic anterior ischemic optic neuropathy in the fellow eye following 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 nonarteritic anterior ischemic optic neuropathy.
Results: The 2-year cumulative probability of nonarteritic anterior ischemic optic neuropathy in the fellow eye was 7% in the aspirin group and 15% in the no-aspirin group, and 5-year cumulative probabilities were 17% and 20%, respectively. Compared with the no-aspirin group, the rate ratio for nonarteritic anterior ischemic optic neuropathy in the fellow eye in the aspirin-user group was 0.43 (95% confidence interval, 0.19 to 0.92) over the 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%; however, if none of the patients with incomplete follow-up developed nonarteritic anterior ischemic optic neuropathy in the fellow eye, then the 5-year risk would be about 12%.
Conclusions: The 5-year risk of nonarteritic anterior ischemic optic neuropathy occurring in the second eye is far lower than that reported by previous studies. Our results suggest a possible short-term but little or no long-term benefit to aspirin in reducing the risk of nonarteritic anterior ischemic optic neuropathy in the fellow eye. However, this finding must be viewed with caution because this study was not conducted prospectively with a controlled protocol.