Non-arteritic anterior ischemic optic neuropathy, known as NAION classically presents immediately upon wakening as moderate vision loss in one eye and generally progresses for several hours to days, and possibly even weeks. The degree of initial central vision loss and level of central visual recovery varies widely. In addition to central and peripheral vision changes, patients also commonly display color vision loss in the form of mild to moderate dyschromatopsia which is generally correlated with the level of visual acuity loss.
Ischemic damage to the optic nerve may occur in several anatomical locations and from a multitude of etiologies. When ischemic damage occurs in the anterior portion of the optic nerve, usually due to interruption of the posterior ciliary artery circulation, this is classified as anterior ischemic optic neuropathy (AION). AION may be further categorized into two types: arteritic AION (AAION) and non-arteritic AION (NAION).