Iridology  is a technique whose proponents believe that patterns, colors, and other characteristics of the iris can be examined to determine information about a patient's systemic health. Practitioners match their observations to iris charts which divide the iris into zones corresponding to specific parts of the human body. Iridologists see the eyes as "windows" into the body's state of health.

Iridologists use the charts to distinguish between healthy systems and organs in the body and those which are overactive, inflamed, or distressed. Iridologists believe this information may be used to demonstrate a patient's susceptibility towards certain illnesses, to reflect past medical problems, or to predict health problems which may be developing.