From Wikipedia

Iris
The iris is the greenish-yellow and the pupil is black

Iridology (also known as iridodiagnosis[1]) is an alternative medicine 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 later consequences of health problems which may be developing.

As it is not a method of treatment but a diagnostic tool, its practitioners often study other branches of alternative medicine, such as naturopathy.[citation needed].

Iridology is not supported by any published studies and is considered pseudoscience by most medical practitioners and eye care professionals