Ischemic optic neuropathy (ION) is a sudden loss of central vision, peripheral vision or both caused by a decreased or lost blood flow to the optic nerve.
For us to see, the optic nerve carries impulses from the eyes to the brain, where they are interpreted as images. The optic nerve consists of a million small, gentle nerve fibers, which act as cables. Many blood vessels fill the optic nerve with blood rich in oxygen. Without healthy, functional optic nerves, eyesight would not be possible.
Some ophthalmologist might describe ischemia of the optic nerve as a “stroke in the back segment of the eye”. A stroke is a severance in blood flow to the brain or nerves in the body. Ischemic optic neuropathy causes a loss in eyesight because the optic nerve has lost blood flow. How much vision is lost depends on how much the nerve is damaged.
There are two types of ischemic optic neuropathy:
- Anterior ischemic optic neuropathy (AION): AION occurs when blood flow is cut off to the front (front) part of the optic nerve (optic nerve).
- Posterior ischemic optic neuropathy (PION). PION is much more common and results from ischemia in the back/posterior part of the optic nerve, located some distance behind the eyeball.
Most cases of ischemic optic neuropathy are of the AION type.
Some of the most common diseases and conditions that can increase the risk of NAION are:
- Diabetes;
- Rheumatoid arthritis;
- Shingles;
- Anemia;
- Syphilis;
- Systemic low blood pressure or very high blood pressure;
- Stomach ulcers;
- Certain heart diseases;
- Vasculitis;
- Migraines.
Treating the underlying causes of cardiovascular disease, a risk factor for NAION, can help control NAION and prevent further vision loss.
For arterial AION – the more dangerous form of ION – corticosteroids are recommended to protect the unaffected eye.