optic nerve

optic nerve The second cranial nerve, which connects the eye to the brain. The optic nerve carries the impulses that are formed by the retina—the nerve layer that lines the back of the eye, senses light, and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images. Using an ophthalmoscope, one can easily see the head of the optic nerve. It is the only anatomic extension of the brain, and it is a part of the central nervous system rather than a peripheral nerve.