The optic nerve (formed by a collection of axons of retinal ganglion cells) originates from the retina, which is in the back of the eye (dark side of the moon), traveling posteriorly through the optic canal, where it is covered completely by dura mater (dura mater is Latin for “tough mother”). It functions to transmit sight (special sense) from the eye to the brain, crossing paths at the optic chiasm, allowing fibers from each optic nerve to reach both sides of the brain. It also plays an important role in the pupillary light reflex, during which both pupils will constrict or dilate in response to a light or dark environment, respectively.