Optic Nerve: Second Cranial Nerve

The optic nerve extends from the retina to the optic chiasm and is approximately 5 cm in length. The optic nerve runs from the back of the globe of the eye to the apex of the orbit and enters the skull through the optic canal to reach the optic chiasm, where it is joined by the optic nerve from the other eye. Directly above the optic chiasm is the hypothalamus and directly below the chiasm is the pituitary gland. The stalk of the pituitary gland runs from the hypothalamus superiorly to the pituitary gland inferiorly, just behind the optic chiasm and between the optic tracts.