The optic nerve is responsible for relaying information from the retina (REH-tin-uh) to the brain. When it becomes inflamed, a condition called optic neuritis, the swelling can make it impossible for the optic nerve to convey its messages. The result can be a sudden or gradual loss of vision, sometimes accompanied by pain with eye movement. Optic neuritis is often a result of another disease, such as multiple sclerosis (skler-OH-siss), which damages the protective covering of nerve fibers, including the optic nerve.

In older people, temporal or cranial arteritis (ar-teer-ITE-iss), in which arteries that supply the temples become inflamed, may be the culprit. Viral illnesses can also inflame the optic nerve. Sometimes this condition goes away by itself, but with multiple sclerosis, it will likely return, causing more permanent damage with each recurrence. Consult an optometrist and ophthalmologist for more information.