The optic nerve is situated in the back portion of the eyeball. It is also referred to as the cranial nerve II or the second cranial nerve. A number of pairs of cranial nerves are present, the optic nerve being the second of them. Though, optic nerve is situated in the eye it is referred to as being part of the central nervous system.

The optic nerve functions by way of transferring visual information that falls on the retina via electrical impulses to the vision centers situated in the brain. Ganglionic cells or nerve cells are the constituents of the optic nerve. There are more than one million nerve fibers present in the optic nerve. The place from where the optic nerve leaves the eye is referred to as blind spot because the specialized photosensitive cells or photoreceptors are absent from this spot.

The most common illness that affects the optic nerve is Glaucoma. Glaucoma occurs when the pressure of the fluid present in the eye (the vitreous humor) increases. This high intraocular pressure, if not treated in time, compresses the cells of the optic nerve, thereby causing their death. This condition is referred to as optic nerve atrophy.