Aug 09 2012

Iridology Update

I published this article on Science-Based Medicine about a year ago. Some of the commenters provided excellent additional information that I have incorporated into this updated version.

There are many medical pseudosciences that persist despite a utter lack of either plausibility or evidence for efficacy. Some practices emerged out of their culture of origin, or out of the prevailing ideas of a pre-scientific age, while others were manufactured out of the imagination of perhaps well-meaning but highly misguided individual practitioners. They were just made up – homeopathy, for example, or subluxation theory.

Iridology belongs to this latter category – a system of diagnosis that was invented entirely by Ignatz Peczely, a Hungarian physician who first published his ideas in 1893. The story goes that Peczely as a boy found an owl with a broken leg. At the time he noticed a prominent black stripe in the iris of one eye of the owl. He nursed the bird back to health and then noticed that the black line was gone, replaced by ragged white lines. From this single observation Peczely developed the notion of iridology.

As I said – that is how the story goes – but it is likely apocryphal or at least oversimplified. Peczely started his career as a homeopath and a “miracle healer.” He was denounced in his own time as a dangerous quack. He later obtained his medical degree only to stave off the authorities. Iridology, therefore, is partly an offshoot of homeopathy. Thanks to Jan Willem Nienhuys for bringing this to may attention (apparently there is more information available on Peczely in Hungarian). He also relates the following information:

Fritz Salzer, in Augendiagnose und Okkultismus (München, 1926) quotes a letter from a young physician named Albert Siegrist (deceased in 1926), a son of the respected homeopath Albert Siegrist (1835-1906) and a brother of the inventor of the contact lens August Siegrist (1865-1947). Albert junior had gone to Budapest on the request of his father, to check on Péczely in 1888 or 1889. In this letter to his father he describes the visit in detail and finishes: ‘Is Dr. P. an ordinary fraud or is he mad? Maybe a mixture of both, but I tend to believe the former.’

Peczely’s idea was that the iris maps to the rest of the body in some way, and therefore the flecks of color in the iris reflect the state of health of the various body parts. This basic approach to diagnosis or treatment is called the homunculus approach – the idea that one part of the body maps to the rest of the body, including the organ systems. Reflexology, auricular acupuncture, and even straight chiropractic follow this approach.

This is what might have happened next: After publishing his initial observations, Peczely set out to test his ideas with well-designed observations that were capable of proving his hypothesis wrong. He carefully built a body of descriptive, but well-established, facts about the relationship between the iris and health. Later, anatomists discovered the underlying mechanism of this connection – a vast system of interconnectedness between the iris and the rest of the body. Further research built on the iris connection, and later medical scientists found more and  more ways to exploit this fascinating aspect of anatomy and physiology.

Of course, this is not what happened. Peczely did not do any serious scientific research. Rather, he simply invented a pseudoscience, by drawing maps of the iris that were as much a product of his imagination as observation, and were largely the result of confirmation bias. He did not perform blinded studies, or produce the kind of evidence that could separate a real phenomenon from an imaginary one. Iridology, as his practice became known, is the N-rays of medical diagnosis. Further, no subsequent science has supported the plausibility or reality of iridology. There is  no underlying anatomy or physiology that can explain how the iris would reflect the state of function of any other part of the body.

This, unfortunately, has not stopped iridology from surviving on the medical fringe for more than a century. The modern popularity of iridology, especially in the US, can be traced back to a chiropractor named Bernard Jensen. He published the book, The Science and Practice of Iridology in 1952. Iridology, or iris diagnosis, continues to be practiced by so-called alternative practitioners, including some chiropractors and naturopaths. It has never been recognized as a legitimate medical practice. For example, for $150 naturopath Frank Navratil will diagnose you from a digital image of your eyes.

Often the iris diagnosis (which can also be done by software analysis) leads to recommendations for supplementation, which are conveniently sold by the iridologist. Here is a description of how iridology is used by a proponent:

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.

Other sites caution that iridology cannot diagnosis pregnancy, because that is a natural condition of the body, and also cannot diagnose prior surgery, as anything that happens under anesthesia will block the signals that would otherwise change the iris. In other words – iridology only tells you about the susceptibility for disease – it cannot actually diagnose a disease or any other verifiable condition. This reasoning is called special pleading – the invention of a special rationalization for each fact that might otherwise falsify a claim or belief. Iridology, apparently, can only discern those things that cannot be verified or falsified.

What you end up with is a medical cold reading – similar to what a mentalist does to create the illusion of mind reading or psychic powers. While “reading” the iris the iridologist can ask about certain health issues. If they are present, that is used to validate iridology. If absent, then the subject simply has a susceptibility for the missing problem.

A Quackwatch article – Confessions of a Former Iridologist by Joshua David Mather Sr., gives some insider insight into the process. He writes:

I soon found that structure “changes” could be created on the video record by changing the angle of the light to the eye. Areas that I thought were dark would suddenly show healing lines when the position of the light changed. Thick white lines would change to thin gray lines when the light moved. More than once during this period an eminent iridologist would call me to his office and show me a change he had recorded in patient’s iris minutes after doing a spinal adjustment. After closely examining his recordings, it became obvious to me that his light position and the angle of the camera to the eye had varied from time to time causing the appearance of a change in the iris.

In other words, the technique of iridology is highly technically dependent on variables such as the angle and intensity of the illumination and the angle of the camera or viewer. With these variables the iridologist can manufacture apparent changes in the iris. These kinds of issues potentially plague any diagnostic method, which is why they need to be standardized, validated, and calibrated. Iridology never has been – it remains in the world of subjectivity.

Mather describes the process further:

The beauty of not having to provide a diagnosis from the eye is that the practitioner simply uses the iris to create leading questions. Suppose I had a patient who had a mark in his lung area. My first question would be “Have you ever had a problem with your lungs? Something like asthma, pneumonia, or emphysema?” If the patient could remember something like that I was considered a genius, but if there was nothing obvious I would question further. “Perhaps you have had a cold recently?” If the answer was no and there wasn’t anything obvious the next step would be to look at the bowel, which is theorized to cause lung weakness. The bowel is represented in the eye as the area directly around the pupil and is usually darker than the rest of the iris. If the bowel was dark then the obvious answer was that the patient had an unknown lung weakness resultant from the bowel. If there was no bowel problem, the last answer was that there was a genetic lung weakness that needed to be treated to prevent future problems.

He is describing a cold reading, not a legitimate diagnostic method.

Iridology lacks any plausibility and its history is that of a pseudoscience, not a legitimate practice. But still we listen to the best scientific evidence in determining whether or not iridology is real. Perhaps Peczely got lucky and made a correct observation despite his lack of scientific confirmation. If iridologists could demonstrate that their readings provide real information, then we would have to take their claims seriously.

In 2000 Edzard Ernst (not surprisingly) published a systematic review of iridology research. He concluded:

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.

As with N-rays, when blinding is introduced iridology is exposed as a complete fiction. Under controlled conditions iridologists cannot agree with each other as to diagnosis, and cannot distinguish healthy subjects of very ill subjects. Since the Ernst review I found one other well-controlled study of iridology, this one in cancer diagnosis. From the abstract:

One hundred ten (110) subjects were enrolled in the study: 68 subjects had histologically proven cancers of the breast, ovary, uterus, prostate, or colorectum, and 42 were control subjects.
All subjects were examined by an experienced practitioner of iridology, who was unaware of their gender or 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).
Iridology was of no value in diagnosing the cancers investigated in this study

There are no well designed studies that are positive.


Iridology is an excellent example of pseudoscience in medicine, displaying many of the core features. It was invented by one individual based upon a single observation and emerging from a culture of quackery and pseudoscience. It follows a pre-scientific notion of biology – the homunculus model. It lacks any basis in anatomy, physiology, or any other basic science. Its practitioners are mostly “alternative” practitioners who use the technique as a cold reading. And the research clearly shows that iridology has absolutely no effect – it does not provide any useful information at all.

Anyone using or promoting iridology is, therefore, a pseudoscientific practitioner. Any profession that endorses iridology is not science-based and should be looked upon with suspicion.

7 responses so far

7 thoughts on “Iridology Update”

  1. daijiyobu says:

    I always find iridologist’s claims ‘that the iris changes’ interesting due to certain logical inconsistencies:

    a) the iris changes due to diseases in various parts of the body;

    b) ‘therapies’ are done to alter those disease states and supposedly improve that patient;

    c) though the iris reflects health and disease, iridologists have nothing to show ‘after the fact’ regarding the iris reflecting those supposed health improvements [or worsenings]. In other words, if the iris changes, show that it changes in the manner claimed.

    And they never can.

    My favorite iridology video right now is a UK naturopath who demonstrates the technique

    At her web page [ ], she shows even an alternate emotional map of the iris known as behavioral
    iridology wherein:

    “positions in the right eye are related to the left brain and your fathers side of the family. Positions in the left eye are related to the right side of the brain and your mothers family.”


  2. Bronze Dog says:

    Other sites caution that iridology cannot diagnosis pregnancy, because that is a natural condition of the body, and also cannot diagnose prior surgery, as anything that happens under anesthesia will block the signals that would otherwise change the iris. In other words – iridology only tells you about the susceptibility for disease – it cannot actually diagnose a disease or any other verifiable condition. This reasoning is called special pleading – the invention of a special rationalization for each fact that might otherwise falsify a claim or belief. Iridology, apparently, can only discern those things that cannot be verified or falsified.

    Sorry if I’m being overly pedantic (or unfamiliar with an alternative use of “special pleading”), but I’d call this ad hoc hypothesizing, where new hypotheses are generated and inconsistently used to explain away failures.

    Either way, I can imagine the practical use: If someone has a mark in the “heart” area before heart surgery to fix the problem, and the iridologist doesn’t see that mark after the surgery, he can claim it went away because the problem was fixed, and its disappearance “proves” that iridology works. If he does see it after surgery, he can claim it didn’t go away because of the anesthesia, or possibly say there’s still a problem with the patient’s heart that needs to be solved with his supplements. The quack is shielded from being wrong in either case.

    On the topic of body homunculus quackery, I’ve been annoyed to see a reflexologist at my local mall. Used to, he just had a kiosk, a couple chairs, and a sign with a foot and body map labeled with Chinese characters. Now he’s got one of the stores with a fancy sign.

  3. DOYLE says:

    Just another variation of commercial divination.Practitioners,forcasters and readers consult their personally authored decoder map and create a cryptic association with someting visual.Your stuck between those who promise recuperation and alleviation for a price and your garden variety Christian scientist that will let their children rot.

  4. SARA says:

    I think this is definitely going to be one of my favorite psuedosciences. It just belongs in a Fantasy Novel, where one of the protagonists is an old wizard who uses the iris to diagnose people. Maybe it tells their future too…Oh the possibilities are endless.

    The evil wizard, of course, uses it for evil. I imagine he does terrible things to people’s eyes to change their behavior or even their physical being. Maybe that’s how he makes orks.

    You know if old Peczely had used his imagination on writing a book, we could all be enjoying and celebrating his life’s work. Wrong path taken.

  5. DevoutCatalyst says:

    I’ve seen it instill fear in people. Ersnt is right, iridology can cause harm.

  6. jimbodunn says:

    My partner recently visited an iridologist recommended by a family friend. I had only just begun cutting my teeth as a skeptic (thanks to a somewhat better recommendation by another family friend to listen to the SGU) and so in the interests of maintaining a happy relationship I allowed this to continue for a few months. As stated in the Steven’s article, the iridologist or “quack” engaged my partner in a vague and, retrospectively, obviously contrived cold reading. The result of which was a regimen of absurd naturopathic remedies which had no effect whatsoever (unless you count the one which gave my partner abdominal pains!). On top of the lack of efficacy (and the $150 NZD consultation fee) was the exorbitant cost of these remedies, around $200 NZD a fortnight! After a while my partner came to her senses (with some gentle skeptical nagging from myself) and since then we have pursued a more science based approach to the issue in question. What’s the harm? My family’s about $1000 NZD out of pocket and who knows what damage the “remedies” could have done long term…
    You’re a good man Dr. Steven Novella, long live the SGU!

  7. eyeguy says:

    The difficulty with proving iridology as a science is that there are no studies being accomplished in North America, yet, there are several studies from other countries that show great reliability of iridology as valid diagnostic tool.

    For example, three recent studies showing good success in detecting diabetes:

    Journal Article: Learning to predict diabetes from iris image analysis:

    Journal Article: Early Detection on the Condition of Pancreas Organ as the Cause of Diabetes Mellitus by Real Time Iris Image Processing:

    Journal Article: Abnormal condition detection of pancreatic Beta-cells as the cause of Diabetes Mellitus based on iris image:

    And some interesting iridology studies that were accomplished in Russia:

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