Iridology, also known as iridodiagnosis, is an alternative medicine practice in which patterns, colors, and other characteristics of the iris are examined for information about a patient's systemic health. Practitioners match their observations to iris charts which divide the iris into many zones believed to correspond to specific parts of the human body. Little, if any, rigorous scientific evidence exists confirming any such link between aspects of the iris and a patient's state of health and there is no recognized causative mechanism for any purported correlation.

Iridologists claim that they do not diagnose specific diseases, but rather that they "highlight" those systems and organs in the body that are healthy and those which are described as "overactive" or "inflamed." These are said to point to a tendency in the patient towards certain illnesses, to reflect past medical problems, or to predict health problems which may be developing.

Since iridology is not a method of treatment, its practitioners have often studied other branches of alternative medicine, such as naturopathy, and used the study of the iris as a diagnostic first step. Iridology is practiced more widely in Europe (especially in the UK and Germany), where there are approximately 20,000 practitioners, than in the United States, which has only a tenth of that number.


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 usually compared to an iris chart that correlates specific zones of the iris with specific parts of the body. Typical charts divide the iris into approximately 80-90 zones. For example, the zone corresponding to the kidney is often in the lower part of the iris just before 6 o'clock. However, iridologists use a number of different maps that do not necessarily agree with one another.

According to iridologists, details in the iris are supposed to reflect changes in the tissues of the corresponding body organs. For example, acute inflammatory, chronic inflammatory and catharral signs are said to indicate involvement, maintenance, or healing of corresponding distant tissues, respectively. Other features that iridologists look for are contraction rings and Klumpenzellen, which are said to indicate various other health conditions, as interpreted in context.


Examining a person's eyes to help determine their health is an ancient practice dating back at least as far as the ancient Greeks.

The first explicit description of iridological principles such as homo-laterality (without using the word iridology) are found in Chiromatica Medica, a famous work published in 1665 and reprinted in 1670 and 1691 by Philippus Meyeus (Philip Meyen von Coburg).

The first use of the word Augendiagnostik ("eye diagnosis," loosely translated as iridology) began with Ignatz von Peczely, a 19th-century Hungarian physician. The most common story is that he got the idea for this diagnostic tool after seeing similar streaks in the eyes of a man he was treating for a broken leg and the eyes of an owl whose leg von Peczely had broken many years before. At the First International Iridological Congress of Iridology, Ignaz von Peczely's nephew, Dr August von Peczely, dismissed this myth as an apocryphal, and maintained that such claims were irreproducible.

German contribution in the Naturheilkunde field is due to a minister Pastor Felke, who developed a form of homeopathy for treating specific illnesses and described new iris signs in the early 1900s. However, Pastor Felke was subject to long and bitter litigation. The Pastor Felke Institute in Heimshiem, Germany was established as a leading center of iridologic research and training.

Iridology became popular in the United States in the 1950s, when Bernard Jensen, an American chiropractor, began giving classes in his own method. This is in direct relationship with P. Johannes Thiel, Eduard Lahn (becoming an American under the name of Edward Lane) and J Haskell Kritzer. Jensen insisted on the body's exposure to toxins, and the use of natural foods as detoxifiers.

Few medical researchers managed to secure funding to study the possible non-visual functions of the eye. In a paper published in Medical Hypotheses, one such group tried to explain the observed patterns of iris transparency that distribute light into the ora serrata (the edge of the optic retina) by postulating a so-called functio ocularis systemica. Based on this hypothesis, the researchers have developed the experimental trans-iridal light therapy method; however, no independent confirmation of the theory and method exists to date. Other results from the mentioned research include early attempts at computerized iris imaging for the purpose of iridologic diagnosis.

Support for Iridology

Practitioners of iridology point to the following benefits of iridology:

Scientific Research into Iridology

Scientific research into iridology has shown mostly, but not entirely, negative results. However, all double blinded, rigorous tests of iridology have failed to find any statistical significance to iridology.

In a study published in the Journal of the American Medical Association, three iridologists incorrectly identified kidney disease in photographs of irises and often disagreed with each other. The researchers concluded: "iridology was neither selective nor specific, and the likelihood of correct detection was statistically no better than chance." Iridologists defended themselves by stating that they needed live examinations and that their approach was valid for predictions of health, not of disease tags once the disease was developed and even complicated. However the three iridologists concerned did not state that before the study took place.

Another study was published in the British Medical Journal (Knipschild4, 1988).Paul Knipschild MD, of the University of Limburg in Maastricht, selected 39 patients who were due to have their gall bladder removed the following day, because of suspected gallstones. He also selected a group of people who did not have diseased gall bladders to act as a control. A group of 5 iridologists examined a series of slides of both groups irises.

The iridologists were not able to identify correctly which patients had gall bladder problems and which had healthy gall bladders. For example one of iridologists diagnosed 49% of the patients with gall stones as having them and 51% as not having them. He diagnosed 51% of the control group as having gall bladder problems and 49% as not. Dr Knipschild concluded: "this study showed that iridology is not a useful diagnostic aid." Iridologists defended themselves with the same considerations as above, but also attacked the methodology of the study.

Ernst5, 2000, said: "Does iridology work? This search strategy resulted in 77 publications on the subject of iridology. All of the uncontrolled studies and several of the unmasked experiments suggested that iridology was a valid diagnostic tool. Such investigations are wide open to bias. The discussion that follows refers to the 4 controlled, masked evaluations of the diagnostic validity of iridology. In conclusion, few controlled studies with masked evaluation of diagnostic validity have been published. None have found any benefit from iridology. As iridology has the potential for causing personal and economic harm, patients and therapists should be discouraged from using it."

Demea6, 2002, showed a positive result for iridology: "The research proposal is to evaluate the association between certain irian signs and general pathology of studied patients. There were studied 57 hospitalized patients The correlations resulted from, shows a high connection between the irian constitution establish[ed] through iridological criteria and the existent pathology. Iris examination can be very useful for diagnosis of a certain general pathology, in a holistic approach of the patient." (translation as per abstract) However, the absence of the required formal criteria for reliable evidence in health care (blindedness, lack of bias)

Regulation, Licensure, and Certification

In Canada and the United States, iridology is not regulated or licensed by any governmental agency. Although there are no official standards of practice in most countries, numerous organizations offer certification courses.