Iris (eye)
The iris (plural: irides or irises) is a thin, circular structure in the eye. It controls the diameter and size of the pupils.
| Iris | |
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| Iris in humans, is the colored (typically blue or brown) area, with the pupil (the circular black spot) in its center, and surrounded by the white sclera. Overlying cornea is completely transparent so is not visible, except the high-gloss luster it gives the eye. Also pictured are the red blood vessels within the sclera. These structures are easily visible on any person's eyes. | |
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| Schematic diagram of the human eye. (Iris labeled at upper right) | |
| Latin | iris |
| Artery | long posterior ciliary arteries |
| Nerve | long ciliary nerves, short ciliary nerves |
| Precursor | Mesoderm and neural ectoderm |
Eye color is the color of the iris. In humans, the iris may look green, blue, brown, hazel (a combination of light brown, green and gold), grey, violet, or even pink. In response to the amount of light exiting the eye, muscles attached to the iris expand or contract the pupil. The larger the pupil, the more light can enter the eye and reach the retina.
Iris (eye) Media
The iris (brown coloured portion of the eye) controls the size of the pupil by contracting the sphincter pupillae and dilator pupillae muscles.
Iris components
Light micrograph of the iris near to the pupil. M. sph. sphincter muscle, L lens
Constriction of the pupil (miosis) observed by laser Doppler imaging reveals radial vessels of the iris.
A human eye demonstrating its owner's rare ability to voluntarily dilate and constrict his pupil on command, via voluntary control of his iris muscles.
Anterior chamber cross-section imaged by an SD-OCT.
Structure of the iris and surrounding parts showing the dilator and sphincter muscles (dilator pupillae and sphincter pupillae).
Among human phenotypes, blue-green-gray eyes are a relatively rare[source?] eye color and the exact color is often perceived to vary according to its surroundings.
A light brown iris with prominent limbal ring. Light brown irises contain pheomelanin.
Example of heterochromia – one eye of the subject is brown, the other hazel.
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