The iris is a flat, ring-shaped membrane behind the cornea of the eye with a pupil in the center that may be adjusted. This is the structure that determines a person's eye color. The iris, along with the pupil, is responsible for controlling the amount of light that enters the eye.
Vision can be hampered by too much or too little light. If there is too much light, the muscular iris shrinks the pupil, and if there isn't enough, it widens it. This is a brain-controlled, involuntary function. Connective tissue and smooth muscle fibers make up almost all of the iris.
Contrary to popular opinion, genuine iris color changes are uncommon. While an eye's color may appear to vary, this is usually due to changes in lighting or perception based on neighboring colors. Eye color is determined by the quantity of pigment in the iris. The eye appears blue when there is very little pigment. The color changes from deep brown to black as the pigment level rises.
No comments:
Post a Comment