Iris (anatomy)
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The iris is a thin, ring-shaped structure in the eye in most mammals and birds that is responsible for controlling the diameter and size of the pupil, and thus the amount of light reaching the retina.
The iris in humans is the colored (typically brown, blue, or green) area, with the pupil (the circular black spot) in its center, and surrounded by the white sclera.
The iris (brown coloured portion of the eye) controls the size of the pupil by contracting the sphincter pupillae and dilator pupillae muscles.
Light micrograph of the iris near to the pupil. M. sph. sphincter muscle, L lens
![Among human phenotypes, blue-green-gray eyes are a relatively rare[citation needed] eye color and the exact color is often perceived to vary according](https://upload.wikimedia.org/wikipedia/commons/thumb/0/0c/Ageev_iris.jpg/500px-Ageev_iris.jpg)
Among human phenotypes, blue-green-gray eyes are a relatively rare[citation needed] eye color and the exact color is often perceived to vary according to its surroundings.
Eye color
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Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye's iris and the frequency-dependence of the scattering of light by the turbid medium in the stroma of th
The irises of human eyes exhibit a wide spectrum of colours
A dark brown iris bordering on black
A light brown iris
A light brown iris with limbal ring