Demyelinating inflammation of optic nerve which can cause complete or partial blindness, most often due to Multiple Sclerosis, or Diabetes Mellitus.Encyclopedia Entry for Optic Neuritis :Optic neuritis. The exact cause of optic neuritis is unknown. The optic nerve carries visual information from your eye to the brain. The nerve can swell when it becomes suddenly inflamed. The swelling can damage nerve fibers. This can cause short or long-term loss of vision. Conditions that have been linked with optic neuritis include: Autoimmune diseases , including lupus , sarcoidosis , and Beh et 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 other common upper respiratory tract infections Multiple sclerosis.Symptoms may include: 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 exam 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 to 3 weeks with no treatment. Corticosteroids given through a vein (IV) or taken by mouth (oral) may speed up recovery. However, the final vision is no better with steroids than without. Oral steroids may actually increase the chance of recurrence. Further tests may be needed to find 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 has a poorer outlook. However, vision in the affected eye may still return to normal.Complications may include: Body-wide side effects from corticosteroids Vision loss Some people who have an episode of optic neuritis will develop nerve problems in other places in the body or develop multiple sclerosis.Call your health care provider right away 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 within 2 to 3 weeks.Retro-bulbar neuritis; Multiple sclerosis - optic neuritis; Optic nerve - optic neuritis.Multiple sclerosis - discharge.External and internal eye anatomy External and internal eye anatomy.Calabresi PA. Multiple sclerosis and demyelinating conditions of the central nervous system.