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)"

Conjunctivitis

Conjunctivitis is redness and inflammation of the thin layer of tissue that covers the front of the eye (conjunctiva). It is very common. People often refer to conjunctivitis as red eye.
Other symptoms of conjunctivitis include itchiness and watering of the eyes, and sometimes a sticky coating on the eyelashes (if it's caused by an allergy).