Nonarteritic Anterior Ischemic Optic Neuropathy

Abstract

Currently there is no generally accepted, well-proven treatment for nonarteritic anterior ischemic optic neuropathy (NAION). Most proposed treatments are empirical and include antithrombotics, vasodynamic agents, treatments aimed at reducing optic disc edema, and various neuroprotective strategies. Most potential treatments have been inadequately studied, prematurely embraced, or prematurely discarded. Evidence for antithrombotic agents is lacking, and small vessel arterial occlusion has never been demonstrated in NAION. Antiplatelet agents have not been studied in acute NAION, but they are often prescribed for acute treatment because of their proven role in stroke prevention. Because NAION is an ischemic disorder occurring more often after the age of 50 in patients with vascular risk factors, I recommend aggressive risk-factor management and antiplatelet therapy. The evidence that aspirin can help to prevent NAION in the fellow eye is divided. I recommend aspirin for secondary prevention, mostly for its proven role in stroke prevention. NAION occurs in patients with physiologically crowded optic nerves and small cup-to-disc ratios. Disc edema may contribute to a "compartment syndrome," which compresses the fine capillary blood supply of the optic nerve head, resulting in ischemia and axonal damage. There is some limited and debatable evidence that oral steroids may shorten the duration of disc edema and improve visual outcome in NAION. I discuss this evidence with patients who present acutely with NAION, and although I consider prescribing oral steroids on a case-by-case basis, I will not routinely recommend oral steroids until a properly randomized clinical trial is performed. Some neuroprotective strategies have been studied, but none have proven to be helpful. Although some (eg, brimonidine) are probably not harmful, I do not recommend these treatments. Early referral to low vision services may help to improve functional visual outcome.