Cornea

The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber and provides most of an eye's optical power http://www.eyeglossary.net/#C. Together with the lens, the cornea refracts light and consequently helps the eye to focus. The cornea gives a larger contribution to the total refraction than the lens, but whereas the curvature of the lens can be adjusted to "tune" the focus, the curvature of the cornea is fixed.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The cornea has sensitive nerve endings; touch of the cornea causes an involuntary reflex to close the eyelid. Because transparency is of prime importance, the cornea does not have blood vessels; it receives nutrients via diffusion from the tear fluid at the outside and the aqueous humour at the inside. In humans, the cornea has a diameter of about 12 mm and a thickness of 0.5 - 0.7 mm in the center and 1.0 - 1.2 mm at the periphery.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Medical terms related to the cornea often start with "kerat-".

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Eye: : This article refers to the sight organ. See Eye (disambiguation) for other usages....

Iris: :For uses as an abbreviation, see IRIS...

Pupil: The term pupil can also mean student. See also: exit pupil...