Optic neuritis usually affects one eye. Symptoms might include:
- Pain. Most people who develop optic neuritis experience eye pain that's worsened by eye movement. Sometimes the pain feels like a dull ache behind the eye.
- Vision loss. Most people experience at least some temporary reduction in vision, but the extent of vision loss varies. Noticeable vision loss usually develops over hours or days. Exercise or a hot bath or shower may exaggerate the vision loss. Vision loss is permanent in some cases.
- Loss of color vision. Optic neuritis often affects color perception. You might notice that colors appear less vivid than normal.
- Flashing lights. Some people with optic neuritis report seeing flashing or flickering lights.
When to see a doctor
Eye conditions can be serious. Some can lead to permanent vision loss, and some are associated with other serious medical problems. Contact your doctor if:
- You develop new symptoms, such as eye pain or a change in your vision.
- Your symptoms worsen or don't improve with treatment.
- You have unusual symptoms, including numbness or weakness in one or more limbs, which may be an indication of a neurological disorder.
The exact cause of optic neuritis is unknown. However, optic neuritis is believed to develop when the immune system mistakenly targets the substance covering your optic nerve (myelin), resulting in inflammation and damage to the myelin.
Normally, the myelin helps electrical impulses travel quickly from the eye to the brain, where they're converted into visual information. Optic neuritis disrupts this process, affecting vision.
The following autoimmune conditions often are associated with optic neuritis:
Multiple sclerosis. Multiple sclerosis is a disease in which your autoimmune system attacks the myelin sheath covering nerve fibers in your brain and spinal cord. In people with optic neuritis, the risk of developing multiple sclerosis following one episode of optic neuritis is about 50 percent over a lifetime.
Your risk of developing multiple sclerosis after optical neuritis increases further if an MRI scan shows lesions on your brain.
- Neuromyelitis optica. In this condition, inflammation occurs in the optic nerve and spinal cord. Neuromyelitis optica has similarities to multiple sclerosis, but neuromyelitis optica doesn't cause damage to the nerves in the brain as often as multiple sclerosis does. Optic neuritis arising from neuromyelitis optica tends to be more severe than optic neuritis associated with multiple sclerosis.
Other autoimmune conditions, such as sarcoidosis and systemic lupus erythematosus, have also been associated with optic neuritis.
Other factors that have been linked to the development of optic neuritis include:
- Infections. Bacterial infections, including Lyme disease, cat-scratch fever and syphilis, or viruses such as measles, mumps and herpes can cause optic neuritis.
- Drugs. Some drugs have been associated with the development of optic neuritis. One of these drugs is ethambutol (Myambutol), which is used to treat tuberculosis.
Risk factors for optic neuritis arising from autoimmune disorders include:
- Age. Optic neuritis most often affects young adults ages 20 to 40 years.
- Sex. Women are much more likely to develop optic neuritis than men are by a ratio of 3-to-1.
- Race. In the United States, optic neuritis occurs more frequently in whites than it does in blacks.
- Genetic mutations. Certain genetic mutations might increase your risk of developing optic neuritis or multiple sclerosis.
Complications arising from optic neuritis may include:
- Optic nerve damage. Most people have some permanent optic nerve damage following an episode of optic neuritis, but the damage might not cause symptoms.
- Decreased visual acuity. Most people regain normal or near normal vision within several months. However, a partial loss of color discrimination may persist. For some people, vision loss may persist after the optic neuritis has improved.
- Side effects of treatment. Steroid medications used to treat optic neuritis subdue your immune system, which causes your body to become more susceptible to infections. Long-term use of steroids may also cause other conditions such as thinning of your bones (osteoporosis).