eye disorders
Ischemic Optic Neuropathy
Introduction
Ischemic optic neuropathy is infarction of the optic disk. It can be arteritic or nonarteritic. The only constant symptom is painless acute vision loss. Diagnosis is clinical. Treatment for the nonarteritic variety is ineffective. Treatment for the arteritic variety does not restore vision but can help protect the unaffected eye. Two varieties of optic nerve infarction exist:nonarteriticandarteritic. The nonarteritic variant occurs more frequently, typically affecting people about 50 years and older. Vision loss tends not to be as severe as in the arteritic variant, which usually affects an older group, typically about 70 years and older. Most ischemic optic neuropathy is unilateral. Bilateral, sequential cases occur in about 20%, but bilateral simultaneous involvement is uncommon. Bilateral involvement is much more common among arteritic than nonarteritic cases. Atherosclerotic narrowing of the posterior ciliary arteries may predispose to nonarteritic optic nerve infarction, particularly after a hypotensive episode. Any of the inflammatory arteritides, especially Giant Cell Arteritis , can precipitate the arteritic form. Acute ischemia causes nerve edema, which further worsens ischemia. A small optic cup to optic disk ratio is a risk factor for nonarteritic ischemic optic neuropathy but not for the arteritic variety. Usually, no medical condition is found as the apparent cause of the nonarteritic variety, although factors contributing to Atherosclerosis (eg, 