NAION is a potentially devastating infarction of the optic nerve head occurring in middle-aged to elderly patients. Patients are usually 50 years of age or over, most commonly in their sixth and seventh decades of life. The infarctions are often sectoral (Fig. 6.1) and the visual field defects are often easily correlated with the optic disc appearance (Fig. 6.2). Central visual acuity may be markedly or minimally disrupted.