Ischemic optic neuropathy (ION), based on vascular anatomy of the optic nerve, pathogenesis and clinical picture, consists of two distinct entities: anterior (AION) and posterior (PION) ischemic optic neuropathies. AION is due to interference with posterior ciliary artery supply to the optic nerve head and retrolaminar part of the optic nerve; it initially presents with visual loss and optic disc edema which progresses to optic atrophy in a month or two. PION is due to occlusion of nutrient arteries to the posterior part of the optic nerve; in this condition during the initial stages the optic disc is normal in spite of marked visual loss, but the atrophy develops later on. Their pathogeneses, causes, clinical pictures, diagnosis and management are discussed briefly.