MD, PhD, FMedSci, FRSB, FRCP, FRCPEd

case-control study

Ignaz von Peczely (1826-1911), a Hungarian physician, got the idea for iridology (or iris-diagnosis) more than a century ago, after seeing streaks in the iris of a man he was treating for a broken leg, and similar phenomena the iris of an owl whose leg von Peczely had broken many years before. He subsequently became convinced that his method was able to distinguish between healthy organs and those that are overactive, inflamed, or distressed. Iridology became internationally known when US chiropractors began adopting this method in their clinical practice. In the United States, most insurance programs do not cover iridology but, in some European countries, they often do. In Germany, for instance, 80% of the Heilpraktiker (non-medically qualified health practitioners) practice iridology.

Iridologists claim to be able to diagnose the health status of an individual, medical conditions or predispositions to disease through abnormalities of pigmentation in the iris. The popularity of iridology renders it necessary to ask whether this method is valid.

The aim of my systematically review from 1999 was to critically evaluate all available, reliable tests of iridology as a diagnostic tool. Four case control studies were included; these are investigations where iridologists are asked to tell by looking at the iris of individuals whether that person does or does not have a certain condition. The majority of these studies suggested that iridology is not a valid diagnostic method. Back then, I concluded that “the validity of iridology as a diagnostic tool is not supported by scientific evaluations. Patients and therapists should be discouraged from using this method.”

Since the publication of my article, several further studies have emerged:

One German team conducted a study investigating the applicability of iridology as a screening method for colorectal cancer. Digital color slides were obtained from both eyes of 29 patients with histologically diagnosed colorectal cancer and from 29 age- and gender-matched healthy control subjects. The slides were presented in random order to acknowledged iridologists without knowledge of the number of patients in the two categories. The iridologists correctly detected 51.7% and 53.4%, respectively, of the patients’ slides; therefore, the likelihood was statistically no better than chance. Sensitivity was, respectively, 58.6% and 55.2%, and specificity was 44.8% and 51.7%. The authors’ conclusion was blunt: “Iridology had no validity as a diagnostic tool for detecting colorectal cancer in this study.”

A study from South Africa aimed to determine the efficacy of iridology in the identification of moderate to profound sensorineural hearing loss in adolescents. A controlled trial was conducted with an iridologist, blind to the actual hearing status of participants, analysing the irises of participants with and without hearing loss. Fifty hearing impaired and fifty normal hearing subjects, between the ages of 15 and 19 years, controlled for gender, participated in the study. An experienced iridologist analysed the randomised set of participants’ irises. A 70% correct identification of hearing status was obtained with a false negative rate of 41% compared to a 19% false positive rate. The respective sensitivity and specificity rates therefore were 59% and 81%. The authors of this investigation concluded that “iridological analysis of hearing status indicated a statistically significant relationship to actual hearing status (P < 0.05). Although statistically significant sensitivity and specificity rates for identifying hearing loss by iridology were not comparable to those of traditional audiological screening procedures.”

A further German study investigated the value of iridology as a diagnostic tool in detecting some common cancers. One hundred ten subjects were enrolled; 68 subjects had histologically proven cancers of the breast, ovary, uterus, prostate, or colorectum, and 42 were cancer-free controls. All subjects were examined by an experienced practitioner of iridology, who was unaware of their medical details. He was allowed to suggest up to five diagnoses for each subject and his results were then compared with each subject’s medical diagnosis to determine the accuracy of iridology in detecting malignancy. Iridology identified the correct diagnosis in only 3 cases (sensitivity, 0.04). The authors concluded that “iridology was of no value in diagnosing the cancers investigated in this study.”

Based on these results it is impossible, I think, to claim that iridology is a valid or useful diagnostic tool. As there is no anatomical or physiological basis for its assumptions, iridology is not biologically plausible. Furthermore, the available clinical evidence does not support its validity as a diagnostic tool. In other words, iridology is bogus. This statement is in sharp contract to the information consumers receive about the method on uncounted websites, books, articles, etc. One website picked at random provides the following information:

The iris reveals changing conditions of every part and organ of the body. Every organ and part of the body is represented in the iris in a well defined area. In addition, through various marks, signs, and discoloration in the iris, nature reveals inherited weaknesses and strengths.

By means of this art / science, an iridologist (one who studies the coloration and fiber structure of the eye) can tell an individual his/her inherited and acquired tendencies towards health and disease, his current condition in general, and the state of every organ in particular.

Iridology cannot detect a specific disease, but, can tell an individual if they have over or under activity in specific areas of the body. For example, an under-active pancreas might indicate a diabetic condition.

Another source claims:

The underlying platform of iridology is that that eyes act as a ‘window’ to a person’s health & well being. This ‘window’ enables the practitioner to see whether areas or organs within the body are healthy, inflamed or ‘over active’. It also enables them to assess a person’s past/ possible future health problems & consider if the patient has a susceptibility to certain diseases. It is important to understand that iridology is simply a method of diagnosis & analysis.

You may well think that none of this really matters. Who cares whether iridology is bogus or not! I would argue that it does matter. Bogus methods cost money that could be better spent elsewhere. More importantly, false positive and false negative diagnoses generated by bogus diagnostic methods can put lives at risk.

But there is a more general and perhaps more crucial point here: alternative medicine is an area where people far too easily get away with ignoring the published evidence and scientific consensus. In the last two decades, I have seen many alternative modalities getting scientifically dis-proven; not in a single such instance can I remember that the corresponding alternative practitioners and their professional organisations took any notice of this fact, and not once did I notice that their practice had changed.

If research is  systematically ignored, it becomes a useless appendix. More importantly, progress is then stifled to the detriment of all our best interests.

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