Iris

The colored part of the eye is called the iris. Iris - eye anatomyIt controls light levels inside the eye similar to the aperture on a camera.  The round opening in the center of the iris is called the pupil. The iris is embedded with tiny muscles that dilate (widen) and constrict (narrow) the pupil size.  

The sphincter muscle lies around the very edge of the pupil. In bright light, the sphincter contracts, causing the pupil to constrict. The dilator muscle runs radially through the iris, like spokes on a wheel.  This muscle dilates the eye in dim lighting.  

The iris is flat and divides the front of the eye (anterior chamber) from the back of the eye (posterior chamber). Its color comes from microscopic pigment cells called melanin. The color, texture, and patterns of each person's iris are as unique as a fingerprint.

St. Luke's Cataract & Laser Institute provides this on-line information for educational and communication purposes only and it should not be construed as personal medical advice.  Information published on this St. Luke's website is not intended to replace, supplant, or augment a consultation with an eye care professional regarding the viewer/user's own medical care.  St. Luke's disclaims any and all liability for injury or other damages that could result from use of the information obtained from this site.

back to top