Optic nerve: Also called cranial nerve II (second cranial nerve). The optic nerve is present in the back of the eye. The function of the optic nerve is to transfer visual information from the retina to the vision centers of the brain. The information is carried in the form of electrical impulses.

Retina:

The retina is the membrane (tissue) that covers most of the inner surface of the eyeball. It contains hundreds of millions of light-sensitive cells, called cones and rods. Rod and cone cells are also called receptors (or photoreceptors). When a ray of light is falling on the retina, the cells present over the retina get activated and convert it into nervous signals (electrical impulse) which are transported to visual centers in the brain by the optic nerve.