(See also Overview of Optic Nerve Disorders.)
Optic neuritis is most common among adults aged 20 to 40 years. Optic neuritis is most often caused by multiple sclerosis. However, some people who have optic neuritis are found only later to have multiple sclerosis. Optic neuritis may also be caused by the following:
Spread of a cancerous tumor to the optic nerve
Chemicals or drugs such as lead, methyl alcohol, quinine, arsenic, and certain antibiotics
Neuromyelitis optica (NMO)
Myelin oligodendrocyte glycoprotein autoantibody (MOG-IgG) disease
Rare causes include diabetes, pernicious anemia, certain autoimmune diseases, Graves disease that affects the orbit (called Graves orbitopathy), bee stings, and injuries. However, the cause of optic neuritis is often unknown.
Optic neuritis causes vision loss, which may be mild or severe and may occur in one or both eyes. Loss of vision may increase over 1 or 2 days. Vision in the involved eye or eyes can range from almost normal to complete blindness. Color vision may be particularly affected, but the person may not realize it. Most people have mild eye pain, which often feels worse with eye movement. Depending on the cause, vision usually returns within 2 to 3 months but not always completely. Some people have repeat episodes of optic neuritis.
Diagnosis involves examination of the reactions of the pupils and observing the back of the eyes with a light with magnifying lenses (ophthalmoscope). The head of the optic nerve at the back of the eye (optic disk) may appear swollen. Testing the field of vision may reveal loss of a portion of the visual field. Magnetic resonance imaging (MRI) may show evidence of multiple sclerosis, myelin oligodendrocyte glycoprotein autoantibody (MOG-IgG) disease, or, rarely, a tumor pressing on the optic nerve. Spinal cord imaging may be done in people with neurologic symptoms.
In some instances, such as when multiple sclerosis seems possible, corticosteroids may be given by vein to treat optic neuritis. After a few days, corticosteroids are given by mouth. These drugs may hasten recovery and reduce the chance of a recurrence. If the optic neuritis is related to multiple sclerosis or an infection, the underlying disease should also be treated.
If a tumor is pressing on the optic nerve, vision usually improves once the pressure caused by the tumor is relieved.
Magnifiers, large-print devices, and talking watches (low-vision aids) may help people with loss of vision.