Optic neuritis is inflammation of the optic nerve. It may cause sudden, reduced vision in the affected eye.

The cause of optic neuritis is unknown.

Sudden inflammation of the nerve connecting the eye and the brain (optic nerve) can cause the nerve to swell and destroy its outer shell (myelin sheath). The inflammation may occasionally be due to a viral infection, or it may be caused by autoimmune diseases such as multiple sclerosis.

Risk factors are related to the possible causes.

• Sudden (acute) loss of vision in one eye
• Changes in the pupil's reactions to bright light
• Loss of color vision
• Pain when you move the eye

A complete medical examination can help rule out related diseases. Tests may include the following:

• Color vision testing
• MRI of the brain
• Visual acuity testing
• Visualization of the optic disc by indirect ophthalmoscopy

Vision often returns to normal within 2 - 3 weeks with no treatment.

Corticosteroids given through a vein (IV) may speed up recovery, but they can cause side effects.

Further tests may be needed to determine the cause of the neuritis. The condition causing the problem can then be treated.

Patients who have optic neuritis without a disease such as multiple sclerosis have a good chance of recovery. Optic neuritis caused by multiple sclerosis or other autoimmune diseases such as systemic lupus erythematosus has a poorer outlook.

• Body-wide side effects from corticosteroids
• Vision loss

About 20% of patients with a first episode of optic neuritis will develop multiple sclerosis.

Call your health care provider immediately if you have a sudden loss of vision in one eye.

If you have optic neuritis, call your health care provider if:

• Your vision decreases
• You develop pain in the eye
• Your symptoms do not improve with treatment

Germann CA, Baumann MR, Hamzavi S. Ophthalmic diagnoses in the ED: optic neuritis. Am J Emerg Med. 2007;25:834-837.