According to iridologist:
- Iridologists see the eyes as "windows" into the body's state of health.
- They can use the charts to distinguish between healthy systems and organs in the body and those that are overactive, inflamed, or distressed. Iridologists claim this information demonstrates a patient's susceptibility towards certain illnesses, reflects past medical problems, or predicts later health problems.
- Generally, they use equipment such as a flashlight and magnifying glass, cameras or slit-lamp microscopes to examine a patient's irises.
Iridology is not supported by quality research studies and is widely considered pseudoscience. The first explicit description of iridological principles are found in Chiromatica Medica, a famous work published in 1665 and reprinted in 1670 and 1691 by Philippus Meyeus (Philip Meyen von Coburg).