Optic neuritis is caused by inflammation of the optic nerve, which is located between the back of the eye and the brain. The optic nerve is the only pathway of information from the nerve cells in the retina of the eye to the nerve cells of the brain. When this nerve is inflamed, the transmission of information is disturbed and visual impairment results. Optic neuritis can be unilateral (affecting only one eye) or bilateral (affecting both eyes).
Optic neuritis can occur as an isolated disease or can be associated with multiple sclerosis (MS). Not everyone with MS will develop optic neuritis.
Some of the symptoms of optic neuritis include:
- Decreased visual acuity or vision loss
- Eye pain and impairment of color vision (dyschromatopsia)*
*Often, eye pain resolves over a few days as visual loss begins.
Optic neuritis is diagnosed by clinical presentation as well as visualization of the optic disc using an ophthalmoscope. In persons with optic neuritis, the optic disc appears pale and pupil response may be decreased in comparison to the unaffected eye. In some cases, MRI of the brain may also be obtained. This would show if there are any other areas of demyelination, which would increase the risk of developing multiple sclerosis.
Intravenous (IV) methylprednisone is recommended to speed the recovery of visual function, even though this does not significantly improve long-term visual outcome. Because this is an IV therapy, children are admitted to the hospital and given a bolus of methyprednisone each evening for three days.
Improvement of vision begins within two to three weeks of occurrence and continues to improve over months. As many as 80 percent of people affected with optic neuritis will regain at least 20/30 vision — 45 percent of those affected will regain 20/30 vision within the first four months; the other 35 percent within the first year.
Reoccurrence of optic neuritis is not uncommon. In the Optic Neuritis Treatment Trial (ONTT), which followed a group of patients with acute unilateral optic neuritis, 28 percent of patients experienced a recurrence of optic neuritis within five years and 35 percent within 10 years. Those with recurrences were more likely to progress to a diagnosis of multiple sclerosis.