The optic nerve is the nerve of vision. It carries images of what we see coded as electrical impulses, from our eye to our brain. The optic nerve is like a cable of electrical wires, and consists of about 1,200,000 separate tiny wires, or nerve fibers. Each of these carries a part of the information. If some or all of the nerve fibers do not do their job, our vision becomes blurred.
Optic neuritis is the medical term used to describe an inflammation of the optic nerve.
The nerve tissue becomes swollen and red, and the nerve fibers do not work properly. If many of the nerve fibers are involved, the vision may be very poor, but if the optic neuritis is mild, vision is nearly normal. Many diseases and conditions may cause optic neuritis, which may affect the optic nerve of one or both eyes. Some people, especially children, develop optic neuritis following a virus illness such as mumps, measles, or a cold. In others, optic neuritis may occur as a sign of a neurologic disease affecting nerves in various parts of the body.