Should Aspirin Be Prescribed to Prevent Recurrence in Nonarteritic Anterior Ischemic Optic Neuropathy?

Nonarteritic anterior ischemic optic neuropathy (AION) is an idiopathic vasculopathy of the optic nerve and is the most common cause of acute optic neuropathy (1,2). Many studies have been conducted to determine causality, but none have been definitive. A link to certain systemic vascular risk factors has been suggested because there is an increased risk in AION of those factors including diabetes, hypertension, hypercholesterolemia, hypercoagulability, ischemic heart disease, and cerebrovascular disease (3–8). Because vision loss in the fellow eye can occur in up to 15% of patients with AION (9), a treatment to prevent second eye involvement has been sought. Given that vascular risk factors have been associated as noted above, aspirin has predictably been prescribed as this preventative measure. There is some evidence in the literature that supports this theory, although the number of published reports is sparse. Kupersmith et al (10) found in a retrospective trial that aspirin taken 2 or more times per week decreased the incidence and relative risk of second eye involvement (10). Beck et al found retrospectively that aspirin reduced the risk of second eye involvement and the effect was stronger in the first 2 years than at the first-year mark. The risk of second eye involvement was 7% in the aspirin group and 15% in the nonaspirin group at 2 years (11). The Ischemic Optic Neuropathy Decompression Trial (IONDT), a prospective study, enrolled 418 subjects and found that 14.7% developed second eye involvement during a follow-up period of 5.1 years. They also found that increased incidence of second eye involvement was not associated with aspirin usage. Furthermore, another retrospective trial showed that aspirin not only reduced the rate of second eye involvement, it also had a dose effect and was more beneficial at higher doses and also prolonged onset of second eye involvement (12). There is also evidence that aspirin does not improve the visual outcome of patients suffering with NAION (13). It is generally believed that prospective studies are more important and consequential than retrospective studies. However retrospective studies have their merit and their place in the scientific milieu. Aspirin has also been used for secondary prevention in other disorders. If we take simply ischemic cerebrovascular disease, there are a myriad of reports in the scientific literature demonstrating clear benefit of risk reduction with aspirin usage. If we extrapolate from the possibility that AION is associated with vascular risk factors, then treating these risk factors may help patients in other ways besides attempting to prevent second eye recurrence. The data regarding the benefits of secondary prevention of ischemic stroke with aspirin monotherapy are huge; there are countless studies in the medical literature. Aspirin plus clopidogrel seems to show some heightened benefit over aspirin monotherapy. A meta-analysis of 11 randomized controlled trials revealed a significant reduction in recurrent ischemic stroke (14). Another analysis of 16 randomized controlled trials showed a significant stroke risk reduction with dual antiplatelet therapy over aspirin monotherapy (15). Long-term dual antiplatelet therapy is also associated with more bleeding side effects and typically not recommended. This author has had personal and professional experience in early recurrence of second eye involvement. Steve Feldon was also quoted previously (9) as having a similar experience and has relayed that he found that this occurs within 18 months (personal communication). Because current MultiCare Rockwood Clinic (RE), Spokane, Washington; Department of Ophthalmology (ACA), Jules Stein Eye Institute, University of California Los Angeles, Los Angeles, California; Blanton Eye Institute (AGL), Houston Methodist Hospital, Houston, Texas; and Department of Ophthalmology and Visual Sciences (GVS), Washington University in St. Louis, St. Louis, Missouri.