It is an inflammation that damages the optic nerve, there is pain and temporary loss of vision are frequent symptoms of optic neuritis.
Treatment: Sometimes it gets better without any treatment, however many people need treatment to improve vision or at least prevent symptoms from getting worse. The most common are corticosteroids and they help a lot to improve vision. Sometimes they can even help bring vision back to the state it was in before optic neuritis. However, for people with multiple sclerosis or other conditions, treatment is usually not as effective.