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The irises of human eyes exhibit a wide spectrum of colours. Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye's iris [1] [2] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris.
An organism's "eye color" is actually the color of one's iris, the cornea being transparent and the white sclera entirely outside the area of interest. Melanin is yellowish to dark hazel in the stromal pigment cells, and black in the iris pigment epithelium , which lies in a thin but very opaque layer across the back of the iris.
Central heterochromia is also an eye condition where there are two colors in the same iris; but the arrangement is concentric, rather than sectoral. The central (pupillary) zone of the iris is a different color than the mid-peripheral (ciliary) zone. Central heterochromia is more noticeable in irises containing low amounts of melanin. [32]
Human eyes (particularly the iris and its color) and the area surrounding the eye (lids, lashes, brows) have long been a key component of physical attractiveness. Eye contact plays a significant role in human nonverbal communication. A prominent limbal ring (dark ring around the iris of the eye) is considered attractive. [109]
After a round of medication made from iodine and quinine, he observed many differences in the colour of his iris. This observation inspired him to create and publish an atlas in 1893, which contained 258 black and white illustrations and 12 colour illustrations of the iris, known as the Diagnosis of the Eye. [11]
The pupil is a hole located in the center of the iris of the eye that allows light to strike the retina. [1] It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.
The uvea (/ ˈ j uː v i ə /; [1] derived from Latin: uva meaning "grape"), also called the uveal layer, uveal coat, uveal tract, vascular tunic or vascular layer, is the pigmented middle layer of the three concentric layers that make up an eye, precisely between the inner retina and the outer fibrous layer composed of the sclera and cornea.
Iris most often refers to: Iris (anatomy), part of the eye; Iris (color), an ambiguous color term; Iris (mythology), a Greek goddess; Iris, a genus of flowering plants; Iris or IRIS may also refer to: