Function of the Iris: The Breakdown. Unbound in its middle to allow the pupil to change size, this structure is connected to the ciliary bodyâthe part of the eye that produces the eyeâs fluid (aqueous humor) and regulates contraction and constriction of the iris. Structure. When the circular muscles contract, the size of the pupil decreases and when the radially arranged muscles contract the size of the pupil increases. Its size is controlled by the help of iris. The iris of the eye is the part of the eye that is located in between the cornea and lens. IRIS Iris is a dark muscular diaphragm that controls the size of pupil PUPIL A small opening in the iris is known as a pupil. Sphincter pupillae muscle (Musculus sphincter pupillae) Iris is a part of the eyeball that serves the regulation of the amount of light that reaches the retina, as it features an opening called the pupil through which the light can pass through. It controls the amount of light that enters the eye. The iris is a circular, colored structure that sits in front of the lens within the coronal plane towards the front of the eye. And when there is low light, the iris opens up the pupil to let in more light. The iris controls the amount of light entering the eyes. The iris is a flat and ring-shaped membrane behind the cornea of the eye with an adjustable circular opening in the center called a pupil. Eye color is specified by that of the iris. The iris contains two sets of muscles. The iris controls the size of the pupil and therefore only lets a certain amount of light to enter the eye; The iris contains two sets of smooth muscles- circular muscles and radial muscles. The lens is transparent, and can be replaced if necessary. In context|anatomy|lang=en terms the difference between pupil and iris is that pupil is (anatomy) the hole in the middle of the iris of the eye, through which light passes to be focused on the retina while iris is (anatomy) the contractile membrane perforated by the pupil, which adjusts to control the amount of light reaching the retina, and which forms the colored portion of the eye (). Iris automatically adjusts the size of Pupil according to the intensity of light.Hence, the iris controls the amount of light entering the eye by adjusting the size of pupil.ExampleIf light is bright, it reduces the size of Pupil,so that less light can enter the eyesIf light is dim, it increases the The circular muscles are arranged in concentric rings around the pupil, while the radial muscles run radially. Lens Focuses light rays onto the retina. The iris (plural: irides or irises) is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. AQUEOUS HUMOR The aqueous humour plays an essential role in the health of your eye. Anatomy . Iris The colored part of the eye which helps regulate the amount of light entering the eye. The iris surrounds a small aperture called the pupil. If the amount of light received by the eye is large (as during the day time), then the iris contracts the pupil (makes the pupil small) and reduces the amount of light entering the eye. The iris automatically adjusts the size of the pupil accordingly to the intensity of light received by the eye. In optical terms, the pupil is the eyeâs aperture, while the iris is the diaphragm. It resides at the bottom part of the pupil right underneath it. When there is bright light, the iris closes the pupil to let in less light. 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