Vision loss often includes both the loss of visual field and visual acuity which can vary from being nearly normal to severely impaired. [1]

Anterior ischemic optic neuropathy (AION) is a medical condition involving loss of vision due to damage to the optic nerve from insufficient blood supply. [2]

Patients may become aware of decreased vision or difficulty seeing above or below the center of gaze. [3]

Vision in that eye is obscured by a dark shadow, often involving just the upper or lower half of vision, usually the area towards the nose. [4]

Unfortunately, there is also a variant of GCA that produces none of the above mentioned symptoms, and the patients generally are in good health. [1]

Each of the optic nerves receives blood supply from branches of the ophthalmic artery within each eye socket. [3]

Second eye involvement occurs in approximately 15% to 20% of patients with NAION within 5 years. [2]

Anterior Ischemic Optic Neuropathy (AION) is a potentially visually devastating disease that occurs in the middle aged and the elderly. [1]

The distinction between AAION and NAION was made to highlight the different etiologies of anterior ischemic optic neuropathy. [4]

Loss of blood supply within the posterior ciliary arteries deprives the optic nerve tissue of oxygen and results in damage to part or all of the optic nerve. [3]

Second eye involvement occurs in approximately 15% to 20% of patients with NAION within 5 years. [4]

AAION is due to temporal arteritis (also called giant cell arteritis), an inflammatory disease of big-sized blood vessels (Chapel-Hill-Conference) that occurs especially with advancing age. [2]

This condition is often referred to as a stroke of the optic nerve, and it usually begins suddenly with little warning in one eye, but frequently progresses to the other eye over time. [5]

This is a small “stroke” in the optic nerve but unlike other strokes is unassociated with weakness, numbness, or loss of speech, nor is there an increased risk of a classic stroke later. [3]

… the experts in the field (neuro-ophthalmologists) have come to a consensus that most cases involve two main risk factors. [4]

Sources:
[1] Ischemic Optic Neuropathy
[2] AION – Artistopia Music
[3] North American Neuro-Ophthalmology Society-Committees
[4] Anterior ischemic optic neuropathy – Wikipedia, the free …
[5] Understanding Stroke of the Optic Nerve by Drs. Richard and …