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NCI Dictionary of Cancer Terms


iris  listen  (I-ris)

  The colored tissue at the front of the eye that contains the pupil in the center. The iris helps control the size of the pupil to let more or less light into the eye.

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Eye anatomy; two-panel drawing shows the outside and inside of the eye. The top panel shows outside of the eye including the eyelid, pupil, sclera, and iris; the bottom panel shows inside of the eye including the cornea, lens, ciliary body, retina, choroid, optic nerve, and vitreous humor.