THIS is a review of three disorders — ischemic optic neuropathy, optic neuritis and the infiltrative-compressive optic neuropathies — that present ophthalmically but have systemic implications. Affected patients typically suffer persistent, monocular impairment of one or more of their visual functions (acuity, field, color sense or brightness). It is important to be able to distinguish among these optic neuropathies, and to differentiate them from other disorders that produce similar symptoms. The latter distinction is usually accomplished by physical examination, but distinguishing among the various optic neuropathies is not easily accomplished by physical examination since they share many signs. However, the . . .