Optic nerve

The optic nerve, also known as cranial nerve II or simply as CN II, is one of twelve cranial nerves but is also considered to be part of the central nervous system. It sends information from the retina (the outermost part of the eye) to the brain. The brain forms a picture using the information so that you can see things.
The retina sees the image upside-down and the optic nerve sends it to the brain so it turns it back into normal.