Iridology is a form of treatment based on the assumption that the iris, that coloured part at the front of the eye, contains regions that map to the organs of the body, in such a way that changes detected in the iris demonstrate the condition of those organs. The iris of the eye is seen as a means of diagnosing medical conditions.
Some iridologists claim that they can detect the medical history of the patient by examining the iris. Some, such as the American iridologist Bernard Jensen suggested that it was possible to detect changes in the body through nerve reflex responses seen in the iris.
Crucially the claims of iridologists depend on there being a reliable link between the state of the iris and the state of the body. However, it is known that the state of the iris changes very little during the course of the life and that there is no automatic connection between the iris and the state of the body. There is no “nerve response” of the kind mentioned by Jensen.
The iris therefore cannot form a reliable diagnostic tool for medical conditions. This was put to the test with Jensen himself and two other iridologists published in the Journal of the American Medical Association in 1979. Jensen and the others were asked to identify from photographs of the eyes of 143 people, which ones had kidney impairment.
In fact, forty-eight patients had the condition. None of the iridologists could reliably identify them beyond the level obtained by chance. One of them thought that 88% had kidney disease and another believed that three quarters of them needed a kidney transplant.
The Journal of Optometry in 1981 carried details of an investigation in which an Australian iridologist was asked to identify thirty-three conditions in fifteen patients. He failed to identify any of them but made sixty incorrect diagnoses.
In 2000, Professor Edzard Ernst published a comprehensive review in the Archives of Opthamology and showed that the iridologists were simply guessing. Those few trials which claimed to show effectiveness of iridology had been designed with deliberate bias. All of the trials of iridologists had demonstrated that it was not a form of diagnosis.
Why doesn’t iridology work?
Despite the fact that some people believe the iris is a reflection of the state of the body, the evidence required to make that belief trustworthy is lacking. A diagnosis requires that causes are reliably associated with outcomes, so for the iris to be used as a diagnostic tool, we need evidence that specific conditions in the body are reliably associated with changes in the state of the iris.
If there was a reliable correlation between the two, then records of observations would show up this association but in fact each iridologist comes up with a different diagnosis. Since there is no pattern connecting the iris to the state of the body, there can be no consistent diagnostic technique. And as a result, the diagnoses vary depending on which iridologist is making it – diagnosis from an iridologist is a lottery.
For a diagnostic technique to work, there has to be consistent observation of successful identification of the medical conditions. Iridologists have never been able to provide anything remotely like evidence.
Is iridology harmful?
The extent to which iridologists wrongly diagnose, and also miss existing conditions, means that patients will be misinformed. They will receive a diagnosis that has no rational basis and that could worry them unduly, or else give them a false sense of security in the event of a serious condition being missed.
Of course, they will also be paying for a diagnosis which has no basis in fact and this could be construed as fraud.
But another worrying consequence of this type of non-diagnosis is that it confuses the patient and gives them a quite incorrect understanding of how their body works. By spreading irrational belief, those patients will be more susceptible to other non-scientific approaches to medicine. This may benefit those selling such treatments, but it is not in the interests of the patient.