The optic nerve is a bundle of nerve fibers that connects the retina (at the back of the eye) and the visual center of the brain. The nerve transports visual information from the retina to the brain, so that the brain can interpret the data into visual images. It is located near the macula, which is the center of the retina that provides sharp central vision. The part of the eye that protrudes through the retina and can be seen on an eye examination is called the optic disc. The optic nerve is actually more similar to brain tissue than to eye tissue. In fact, when a fetus begins to develop, the optic nerve is actually part of the brain. Only as the fetus develops binocular vision do the optic nerves move behind the eyes.
The optic nerve contains two blood vessels: the central retinal artery and the central retinal vein. The central retinal artery carries nutrients to the retina, and the central retinal vein carries waste away from the retina. Each eye has a separate optic nerve that leads from the retina towards the brain, and the two nerves join together at the optic chiasm, which is located between and behind the two eyes.
There are several problems that can affect the optic nerve, such as optic nerve neuritis, optic nerve atrophy, and optic nerve hypoplasia. Optic nerve neuritis is the inflammation of the optic nerve, and it is often caused by multiple sclerosis (MS). Optic nerve atrophy occurs when optic nerve fibers begin to die off, giving the nerve a whitish color (rather than its normal pink). Optic nerve hypoplasia, a birth defect, occurs when a fetus's optic nerve remains underdeveloped during eye formation. All of these conditions can cause anything from temporary loss of sight to complete blindness, and should be brought to medical personnel immediately.