Iridology (sometimes referred to as iris diagnosis) is based on the belief that each area of the body is represented by a corresponding area in the iris of the eye (the colored area around the pupil). According to this viewpoint, a person's state of health and disease can be diagnosed from the color, texture, and location of various pigment flecks in the eye. Iridology practitioners claim to diagnose "imbalances" that can be treated with vitamins, minerals, herbs, and similar products. Some also claim that the eye markings can reveal a complete history of past illnesses as well as previous treatment. One textbook, for example, states that a white triangle in the appropriate area indicates appendicitis, but a black speck indicates that the appendix had been removed by surgery. Iridology charts -- dozens of which exist -- vary somewhat in the location and interpretation of their iris signs. Sclerology is similar to iridology but interprets the shape and condition of blood vessels on the white portion (sclera) of the eyeball. Some iridologists use computers to help them analyze eye photographs and select the products they recommend.
Proponents of iridology attribute its development to Ignatz von Peczely, a Hungarian physician who, during his childhood, had accidentally broken the leg of an owl and noticed a black stripe in the lower part of the owl's eye. Nonadherents suggest that von Peczely may have developed his theory to pass time while he was imprisoned after the 1848 Hungarian revolution. After his release from prison he allegedly saved the life of his mother with homeopathic remedies, recalled the incident of the owl's eye, and began studying the eyes of his patients.
Bernard Jensen, D.C. (1908-2001), the leading American iridologist, stated that "Nature has provided us with a miniature television screen showing the most remote portions of the body by way of nerve reflex responses." He also claimed that iridology analyses are more reliable and "offer much more information about the state of the body than do the examinations of Western medicine." However, in 1979 he and two other proponents failed a scientific test in which they examined photographs of the eyes of 143 persons in an attempt to determine which ones had kidney impairments. (Forty-eight had been diagnosed with a standard kidney function test, and the rest had normal function.) The three iridologists showed no statistically significant ability to detect which patients had kidney disease and which did not. One iridologist, for example, decided that 88% of the normal patients had kidney disease, while another judged that 74% of patients sick enough to need artificial kidney treatment were normal.
In 1980, an experienced Australian iridologist underwent two tests. In the first, he examined photographs of 15 patients who had been medically evaluated and had a total of 33 health problems. The iridologist did not correctly diagnose any of these problems. In three cases he named a part of the body that had had trouble (for example, he said "lesion in throat area" for a patient whose tonsils had been removed during childhood), but he completely missed the other 30 problem areas and made 60 incorrect diagnoses. In the second trial, four people had their eyes photographed when they were in good health and rephotographed when they reported being ill. The iridologist made a large number of (incorrect) diagnoses from the initial photographs and was unable to accurately identify any organ that underwent a change when the health problem arose. He was also asked to compare iris photographs of another healthy individual taken only two minutes apart. He made five incorrect diagnoses for the first of these and four different incorrect ones for the second.
More recently, five leading Dutch iridologists failed a similar test in which they were shown stereo color slides of the right iris of 78 people, half of whom had gallbladder disease. None of the five could distinguish between the patients with gallbladder disease and the people who were healthy. Nor did they agree with each other about which was which. These negative results, of course, are not surprising, because there is no known mechanism by which body organs can be represented or transmit their health status to specific locations in the iris.