What is Ischemic Optic Neuropathy (AION)?

This is the most common cause of sudden decreased vision in patients older than 40 years. We do not see with our eyes. We see with part of our brain that is capable of interpreting visual signals sent back from the eyes. This is located at the back of our head (the occipital lobes). Information is transmitted from the eyes to the brain via the optic nerves. These nerves are composed of the long tube extensions (axons) of cells (ganglion cells) located within the inner lining of the eye (the retina) that exit the back of the eye at the optic disc. Each of the optic nerves receives blood supply from branches of the ophthalmic artery within each eye socket. The optic disc has a unique blood supply (the posterior ciliary arteries).

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. This is a small “stroke” in the optic nerve. It is painless. Patients may become aware of decreased vision or difficulty seeing above or below the center of gaze. Loss of the blood supply results in swelling of the optic disc, often associated with hemorrhages. The hemorrhages and swelling will go away leading to the development of a pale disc (optic atrophy). As the swelling resolves, some of the axons will be permanently lost. We do know that this happens more often in patients who are born with small optic discs. These episodes may occur when there is a sudden drop in blood pressure (following an operation or associated with blood loss after an accident). Patients who smoke, or who have diabetes or high blood pressure, may be at higher risk for AION.