Ischemic optic neuropathies

Ischemic optic neuropathy represents as an acute ischaemic disorder of the optic nerve. It is of two very distinct types: anterior ischemic optic neuropathy (AION) involving the ONH, and posterior ischaemic optic neuropathy (PION) involving a segment of the rest of the optic nerve posteriorly. Arteritic anterior ischaemic optic neuropathy (AAION) results from short posterior ciliary artery (SPCA) vasculitis and the resultant optic nerve head infarction. The rapid onset, stable course with generally poor recovery, association with vasculopathic risk factors, and similarity to AAION implies a vascular cause for nonarteritic anterior ischaemic optic neuropathy (NAION) as well, but the direct evidence remains limited. AAION is caused by giant cell arteritis (GCA). NAION has been reported in association with a number of diseases that could predispose to reduced perfusion pressure or increased resistance to flow within the optic nerve head. Typically, AAION develops in elderly patients, with a mean age of 70 years, with severe visual loss. Pallor of the optic disc, which may be severe, chalky-white, is associated with AAION. The nonarteritic form of the disease occurs in a somewhat younger age group (mean age of 60 years) and usually is associated with less severe visual loss. Ischemia of the optic nerve that does not involve the optic nerve head is termed posterior ischemic optic neuropathy (PION). It presents with acute visual loss associated with signs of optic neuropathy (afferent pupillary defect and visual field loss) in one or both eyes, with initially normal appearance of the optic disc, which subsequently becomes atrophic.