Ischemia
The word "ischemia" () is from Greek ἴσχαιμος "iskhaimos", "staunching blood" from ἴσχω "iskhο", "keep back, restrain" and αἷμα "haima", "blood".
Anterior ischemic optic neuropathy
The second major risk factor involves more general cardiovascular risk factors. The most common are diabetes, hypertension and high cholesterol levels. While these factors predispose a patient to develop NAION, the most common precipitating factor is marked fall of blood pressure during sleep (nocturnal arterial hypotension)- that is why at least 75% of the patients first discover visual loss first on waking from sleep. These vascular risk factors lead to ischemia (poor blood supply) to a portion of the optic disc. The disc then swells, and in a crowded optic disc, this leads to compression and more ischemia.