This is an inflammation of the optic nerve that causes vision loss and occasionally eye pain. The optic nerve is the large nerve that connects the eye to the brain. Inflammation of this nerve will cause vision problems such as an enlarged blind spot and decreased vision. Optic neuritis occurs more in younger people (under 50) and is sometimes a harbinger of more serious inflammatory nerve disorders like multiple sclerosis. Nerve swelling can sometimes be seen by the eye doctor by looking at the optic disk in the back of the eye. However, most of the optic nerve is located behind the eye and only a small portion of the nerve can actually be visualized during a dilated eye exam. Other hints of nerve swelling are pupil abnormalities and decreased color vision. More definitive diagnosis can be made by MRI, which is also useful for detecting other lesions in the brain consistent with multiple sclerosis. Treatment usually involves referral to a neurologist with possible IV steroids or other anti-inflammatory medicines. The vision usually comes back over a few weeks or months, though some permanent vision loss can occur.