Eyes

"The eye is the organ of sight (vision) in humans and animals. The eye works by transforming light waves into visual images. Eighty percent of all information received by the human brain comes from the eyes. Eye color is created by the amount and type of pigment in the iris. Multiple genes inherited from each parent determine a person’s eye color. The eye is a slightly asymmetrical globe, about an inch in diameter. The front part of the eye (the part you see in the mirror) includes:
• The iris (the pigmented part)
• The cornea (a clear dome over the iris)
• The pupil (the black circular opening in the iris that lets light in)
• The sclera (the white part)
• The conjunctiva (an invisible, clear layer of tissue covering the front of the eye, except the cornea)"

Optic neuritis

Optic neuritis is inflammation of the optic nerve, the structure that connects the eye to the brain. The optic nerve consists of nerve tracts (axons) that originate in the retina of each eye. The optic nerve carries visual information from the retina to the nerve cells in the brain stem, where the information is relayed to the area of the brain that recognizes vision (the occipital cortex). Optic neuritis can occur in children or adults and may involve either one or both optic nerves.