Mammalian eye

Eye
Schematic diagram of the human eye.
Human eye seen from the front in its orbit surrounded by the eyelid and eyelashes, showing the anterior segment with the iris (light brown in this individual), pupil, and sclera visible
Details
Identifiers
Latin	oculus (plural: oculi)
Anatomical terminology [edit on Wikidata]

Mammals normally have a pair of eyes. Although mammalian vision is not so excellent as bird vision, it is at least dichromatic for most of mammalian species, with certain families (such as Hominidae) possessing a trichromatic color perception.

The dimensions of the eyeball vary only 1–2 mm among humans. The vertical axis is 24 mm; the transverse being larger. At birth it is generally 16–17 mm, enlarging to 22.5–23 mm by three years of age. Between then and age 13 the eye attains its mature size. It weighs 7.5 grams and its volume is roughly 6.5 ml. Along a line through the nodal (central) point of the eye is the optic axis, which is slightly five degrees toward the nose from the visual axis (i.e., that going towards the focused point to the fovea).