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Updated January 15, 2009



Definition: The colored part of the eye that controls the amount of light that enters into the eye. It is the most visible part of the eye.

The iris is divided into two zones:

  • Pupillary Zone: The inner part of the iris that forms the pupil's boundary.
  • Ciliary Zone: The remaining part of the iris that extends into the ciliary body.
The color of the iris is determined by a dark pigment called melanin. The more melanin present, the darker the iris.
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