Cup-disc ratio and ischemic optic neuropathy.

Cup-disc ratios in the fellow eyes of 26 patients with unilateral, nonarteritic, anterior ischemic optic neuropathy were compared with the ratios in fellow eyes of 29 patients with unilateral idiopathic or demyelinative optic neuritis. The ratios in both groups were also compared with the ratios of a large group of normal subjects evaluated in a population survey. Observers measured the cup-disc ratio by viewing color stereophotographs. The cup-disc ratios of the fellow eyes of patients with anterior ischemic optic neuropathy were significantly smaller on average than were those of the fellow eyes of patients with optic neuritis and the normal subjects. Eyes with small cup-disc ratios may be more vulnerable to infarction than are eyes with large cup-disc ratios.