According to iridolgy:
- The iris is the greenish-yellow area surrounding the transparent pupil. The white outer area is the sclera, the central transparent part of which is the cornea.
- Iridologists generally use equipment such as a flashlight and magnifying glass, cameras or slit-lamp microscopes to examine a patient's irises for tissue changes, as well as features such as specific pigment patterns and irregular stromal architecture. The markings and patterns are compared to an iris chart that correlates zones of the iris with parts of the body. Typical charts divide the iris into approximately 80-90 zones. For example, the zone corresponding to the kidney is in the lower part of the iris, just before 6 o'clock. There are minor variations between charts' associations between body parts and areas of the iris.
- According to iridologists, details in the iris reflect changes in the tissues of the corresponding body organs. One well-known practitioner, Dr. Bernard Jensen, puts it this way: "Nerve fibers in the iris respond to changes in body tissues by manifesting a reflex physiology that corresponds to specific tissue changes and locations". This means that a bodily condition translates to a noticeable change in the appearance of the iris. For example, acute inflammatory, chronic inflammatory and catarrhal signs may indicate involvement, maintenance, or healing of corresponding distant tissues, respectively. Other features that iridologists look for are contraction rings and Klumpenzellen, which may indicate various other health conditions, as interpreted in context.
History
The first explicit description of iridological principles such as homolaterality (without using the word iridology) are found in Chiromatica Medica, a famous work published in 1665 and [edit reprinted in 1670 and 1691 by Philippus Meyeus (Philip Meyen von Coburg).