The first use of the word Augendiagnostik ("eye diagnosis," loosely translated as iridology) began with Ignaz von Peczely a 19th-century Hungarian physician. His experience began when he tried to liberate a barn-owl from a bush. While Ignaz von Peczely toke care of her, he observed changes in her iris. Then, Von Peczely began to observe the iris in his pacients.
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.
An 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.
But iridology is not regulated or licensed by any governmental agency (in Canada, USA and Europe), although numerous organizations offer certification courses.