Iridology is an alternative medicine technique, where patterns, colors, and other characteristics of the iris can be examined to determine information about a patient's 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 say they can use the charts to distinguish between healthy systems and organs in the body and those that are overactive, inflamed, or distressed. This information shows a patient's susceptibility towards certain illnesses, reflects past medical problems, or predicts later health problems.