1. Home
  2. Health
  3. Vision

Iris

By Troy Bedinghaus, O.D., About.com

Updated: January 4, 2008

About.com Health's Disease and Condition content is reviewed by Kate Grossman, MD

Iris

A.D.A.M.
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.

Explore Vision

More from About.com

About.com is accredited by the Health On the Net Foundation, which promotes reliable and trusted online health information.
  1. Home
  2. Health
  3. Vision
  4. Vision Glossary
  5. Eye Anatomy
  6. Iris-What is the Iris of the Eye?

©2008 About.com, a part of The New York Times Company.

All rights reserved.