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
• Decreased constriction of the pupil of the affected eye in 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.

Intravenous corticosteroid therapy may accelerate visual recovery but may be associated with systemic side effects. Oral corticosteroid therapy may increase the risk of recurrence, and is seldom used for initial therapy. It may be used after initial intravenous corticosteroid therapy.

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

Optic neuritis without underlying disease such as multiple sclerosis has a good prognosis for recovery. Optic neuritis resulting from multiple sclerosis, or other autoimmune disease such as systemic lupus erythematosis, is associated with a poorer prognosis.

• Systemic side effects of therapy
• 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.