What is optic neuritis?
Optic neuritis (ON) is a condition in which the nerve to the eye (the optic nerve) becomes inflamed or irritated. Inflammation refers to a process in which white blood cells and chemical messengers go to an area of the body to stimulate healing or to attack viruses or foreign material. Optic neuritis is a condition that can happen because of a disease or without any specific known cause.
Who gets optic neuritis?
This disease can happen to anyone at any age, but most cases occur in women who are between the ages of 20 to 40. In the United States, optic neuritis occurs more commonly in Caucasians than in African-Americans. ON is also more common in Asian cultures.
What are the symptoms of optic neuritis?
- Optic neuritis usually occurs in one eye, though occasionally both eyes are affected (about one in 10 times).
- Vision loss is common and typically occurs over a few days and stops progressing by one to two weeks.
- Symptoms include blurring of vision, a loss of part or all of central vision, reduced color vision, and dimness of vision.
- It may also be harder to see at night due to difficulty with contrast and glare.
- Most patients with ON have eye pain which is characteristically worse with movement of the eye.
- Sometimes people see flickering or flashing lights when they have optic neuritis (about 1 in 3 patients).
- Some people notice that when they exercise or exert themselves their vision becomes blurrier.
What causes optic neuritis?
Myelin is a material that is produced by oligodendrocytes (a type of cell) in the central nervous system. Myelin wraps around the axons of many nerves. It helps speed nerve activity and insulates electrical conduction in the nerves.
The most common cause for ON is inflammatory demyelination of the optic nerve. Demyelination is a process in which the myelin is stripped off by disease. It is believed that ON is an autoimmune process, where for some unknown reason the immune system attacks tissues of the body causing injury. While this may occasionally occur after an infection, there is often no clear reason why the immune attack occurs.
Some patients with ON will go on to have other episodes of demyelination in the nervous system and develop multiple sclerosis. Multiple sclerosis is an autoimmune condition in which attacks of demyelination occur in different parts of the brain and spinal cord over time.