Non-arteritic AION (NA-AION)is the most common form of AION. The majority of those affected are over the age of 50; 10% of cases are in people over age 45. However, the condition can appear at any age. Both men and women have the same rates of occurrence.
NA-AION is caused not by inflammation of the arteries but by one of the following:
(1) a drop in blood pressure to such a degree that blood supply to the optic nerve is decreased
(2) increased intraocular pressure
(3) narrowed arteries
(4) increased blood viscosity (thickness)
(5) decreased blood flow to the optic nerve where it leaves the back of the eye.
A number of diseases or conditions can cause these risk factors, putting a person at greater risk of developing NA-AION.
Risk factors include:
- High Blood pressure
- Diabetes mellitus
- High Cholesterol
- Sleep apnea
- Heart disease
- Blocked arteries
- Anemia or sudden blood loss
- A sudden drop in blood pressure
- Sickle cell trait
- Vasculitis (inflammation of a blood vessels)
The main symptom of NA-AION is a sudden, painless loss or blurring of vision in one eye, usually noticed upon waking from a night’s sleep or even a nap. It is believed that the body’s normal drop in blood pressure during sleep ― along with one or more underlying risk factors ― triggers an interruption of blood flow to the optic nerve.
Note that there is no correlation between a person having poor eyesight (being near-sighted or far-sighted) and the development of NA-AION.