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 optic nerve (the nerve connecting the eye and the brain) leads to swelling and destruction of its outer shell, called the myelin sheath. The inflammation may occasionally be the result of a viral infection, or it may be caused by autoimmune diseases such as multiple sclerosis. Risk factors are related to the possible causes.

• Acute loss of vision in one eye
• Loss of color vision
• Pain on movement of the eye
• Changes in the pupil's reactions to bright light

A complete medical examination is usually used to rule out associated diseases. Tests may include the following:

• Visual acuity testing
• Color vision testing
• Visualization of the optic disc by indirect ophthalmoscopy
• MRI of the brain to test for multiple sclerosis

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

Corticosteroids given by an IV may speed up recovery but can cause body-wide side effects.

Further tests may be needed to determine the cause of the neuritis, and the condition causing the problem would then be treated.

Patients who have optic neuritis without an underlying disease such as multiple sclerosis have a good chance of recovery. Optic neuritis resulting from multiple sclerosis or other autoimmune diseases such as systemic lupus erythematosus is associated with a poorer visual outcome.

• 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 sudden loss of vision in one eye occurs.

If you have optic neuritis, call your health care provider if vision decreases, pain in the eye develops, or if symptoms do not improve with treatment.