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

The exact cause of optic neuritis is unknown.

The optic nerve carries visual informations from your eye to the brain. Sudden swelling of this nerve can damage the insulation (myelin sheath) surrounding each nerve fiber. This can result in permanent visual loss.

Conditions that have been linked with optic neuritis include:

• Autoimmune diseases, including lupus, sarcoidosis, and Behcet's disease
• Cryptococcosis, a fungal infection
• Bacterial infections, including tuberculosis, syphilis, Lyme disease, and meningitis
• Viral infections, including viral encephalitis, measles, rubella, chickenpox, herpes zoster, mumps, and mononucleosis
• Respiratory infections, including Mycoplasma pneumonia and common upper respiratory tract infections
• Multiple sclerosis

• Loss of vision in one eye over an hour or a few hours
• Changes in the way the pupil reacts 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:

• Color vision testing
• MRI of the brain including special images of the optic nerve
• Visual acuity testing
• Visual field testing
• Examination of the optic disc using indirect ophthalmoscopy

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

Corticosteroids given through a vein (IV) or taken by mouth may speed up recovery. Higher doses should be used cautiously, as they can have serious side effects.

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

People 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. However, vision in the affected eye may still return to normal.

• Body-wide side effects from corticosteroids
• Vision loss

About 1 in 5 patients with a first episode of optic neuritis will develop myelin sheath inflammation elsewhere in the body, or will develop multiple sclerosis.

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

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

• Your vision decreases
• The pain in the eye gets worse
• Your symptoms do not improve with treatment

Glaser JS. Topical diagnosis: prechiasmal visual pathways. In: Tasman W, Jaeger EA, eds. Duane’s Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 5.

Sra SK, Sra KK, Friedlaender M, Trocme SD. Immunology of neurologic and endocrine diseases that affect the eye. In: Tasman W, Jaeger EA, eds. Duane’s Ophthalmology. 15th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2009:chap 35.