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.

32 Responses to Iridology: if evidence is systematically ignored, lives are put at risk

  • I wonder if the people who believe in iridology use airport iris recognition systems? You know, the ones based on the fact that the iris doesn’t change?

  • I just have to say doctor you’ve spent a lot of time coming to the wrong conclusions about something you know absolutely nothing about.
    I have studied Iridology and find that it’s fascinating and in all the cases I’ve looked at; extremely accurate.
    I can attest to the fact that I’ve never harmed ANYONE with my study of their eyes while you doctor have probably done more harm to your patients in a lifetime than any one layperson could do in several.
    I just wish once the medical community would quit relying on what you would call “bogus” organizations like the FDA that don’t even study the poisons you put into people all the while making a very good living.

    Please refrain from pointing fingers at something you haven’t actually STUDIED it then YOU are the one that’s incorrect.
    Do your own homework on it….or even go to an Iridologist and see what you can… will change your life…and might even save it…..that is if you’re not as closed minded as I suspect you are.
    Good day.

    • “extremely accurate”
      any evidence?

    • Kimberly Weninger

      Where would you like me to start?

      Your failure to understand science?

      Your failure to understand evidence?

      Your failure to understand biology and human anatomy?

      Your failure to understand cognitive biases?

      Your failure to think critically?

      You choose.

    • Kimberly Weninger While you do make a lot of good points about other doctors, that does not magically make Iridology an accurate way to detect medical issues and any amount of research points to it’s inaccuracy. You cannot assume because one is an MD, or even a casual poster that they haven’t done in depth research. I could know everything on a certain subject without changing my title, by spending years learning about it. A lot of people have multiple skill sets.

  • I can tell that if you have a major health problem you eye will not be recognized by a iris recognition systems, you can google it… but the iris patter check points of coincidence and have some grade of error… and there are tons of pictures of people sick and the eye and wen they cure how the eye change…. so fuck evidence and just call it bogus…

  • @Weninger & antonio

    I went through this some years ago and studied everything there is to find about this. Both Iridology and Sclerology and other related genres are, in contrast to most other “alternative” health-related practices rather easy to disprove. In the first place, these methods have no prior plausibility as there are no anatomical or physiological circumstances, which might explain how you can diagnose health-conditions by these means. A score of studies have been performed, which totally fail to show any efficacy of iridology/sclerology. I do not want to spend my time finding the references, they are easily obtained with basic skills in google-ing. Several tests have shown that iridologists or sclerologists are no better than monkeys at diagnosing ailments, which they commonly pretend to discern.

    I had the privilege recently of reading through a book on “eyeology” by one of the purported “masters” of that trade, one Leonard Mehlmauer. The only thing I learned from reading his works was that he has no understanding of the human body or its functions. He knows some names and phrases, the rest is baloney. I will refrain from using the word most fitting for describing his qualities but if you know the works of Dostoyevsky you will understand what term I am alluding to.
    Eyeology (iridology and sclerology) are disproven nonsense. Its a simple and unusually well established fact.

  • In the mid-70’s the AMA raided a lot of iridologist, some who were medical doctors,who were using iridology in their practice. Many did prison time for allegedly “practicing medicine without a licence.” I’ve seen the efficacy of iridology in a clinical research setting first hand, so I’m not convinced that the claim that iridology is bogus . To me these statements are just a more sophisticated way of discrediting iridology. Iridology has, in the past, threatened the livelihood of western medical practitioner.

  • Hmm, the heartbeat’s pulse wave form has been proven to be correlated with various diseases.
    See the work of Jingjing Xia, and Simon Liao

    As I think of this issue, it makes for a good big data, machine learning, data science project.

    Get thousands of medical charts with confirmed diagnosis of different diseases.
    Also get pictures of the eyes.

    Analyze the data. Apply algorithms and machine learning.
    What results do you get?

    • ” heartbeat’s pulse wave form has been proven to be correlated with various diseases”
      links to evidence please

    • Rather strange coincidence that I sort of happened upon your comment while doing an unrelated search for the lack of efficacy of Iridology. Only a few hours earlier I was looking through the academic calendar for the applied computer science program at the University of Winnipeg where Simon Liao teaches. Had the opportunity to meet him a few years ago. Pretty funny guy doing some fascinating research.

      With regard to the rest of your comment, as a software dev I’d also be interested in applying machine learning to a large labeled dataset of this sort. Not specifically for Iridology purposes because I think it’s a waste of resources, but more for generally applicable medical research. I believe something along these lines is currently being studied at the University of British Columbia and a few in the states.

  • Having written a critical essay about iridology in my language, I was countered with a long, mostly translated rant containing a cavalcade of all the classical fallacies, mostly ‘ad hominem’ towards the “specialists” and Steven Barrett in particular.
    Anyway, one little claim caught my eye and I tried in vain to locate its origins.
    This claim seems to pervade many defensive writings on iridology and goes like this:


    The accuracy and reliability of iris signs as reflex indications of tissue pathology in the body have been confirmed in many thousands of instances by: laboratory tests, X-rays, and other commonly accepted diagnostic approaches. Recent research from clinical trials in South Korea from Aju University have shown that the validity of using iridology for predicting diseases ranges between 71.4% and 100% accuracy.

    The accepted clinical results by the Korean Government include:

    Diseases of: % Accuracy


    Digestive system 90.2%

    Endocrine system 86.4%

    Muscle/Skeletal system 72.2%

    Nervous system 79.9%

    Urogenital system 85.7%

    Cardiovascular system 75%

    Circulatory system 81.6%

    Immune system 54.2%

    I have hitherto been unsuccessful in finding the source of this. One iridology site gives two links, Neither of them are useful. (In the third chapter 🙂 ) This is only one of many sites that echo claims of Korean research confirming this, without citing any source.

    Anyone here have an idea or better search-skills than I have? Where in the world does this story of Korean government-sanctioned proof of iridology’s positive predictive value come from? I would love to be able to include a proper analysis of it in a little article.

  • Some before and after photos of the iris in exacting lighting conditions during treatment would help dispel critics if it can actually show changes in iris structure/color in the zone pertaining to the organs/systems being treated. If the eye truly is a reflex organ that can record evidence of disease throughout the body by some novel but hitherto not well defined biological/chemical process then I think this would be worth considering. There are thousands of iris photos out there but I am yet to see a well documented photographic sequences of iris photos from a patient being treated showing actual changes during the healing stage.

    • Of course it would be wonderful if such dreams came true. But they don’t What you propose has already been done, several times, and the outcome is entirely negative. Iridologists have compared eye photos from various diseases and their diagnostic accuracy has been that of pure chance. There is nothing to it. Iridology and sclerology are based on pure, naive fantasy.

  • So I’ve been looking around for someone to say something along these lines:

    “We documented over 100,000 people with X problem and taken a photo of their eyes to trace patterns which might correlate between the illness and the iris patterns. We’ve repeated this for X, Y, Z types of cases, and for that reason we believe that A, B, C patterns correlate to X, Y, Z possible issues.”

    So far I haven’t seen anything remotely like this from either side of the aisle on the matter.

    I think that testing how well a “master practitioner” can diagnose as a way to invalidate the study itself makes sense. But that doesn’t give the concept of “patterns in the eye matching illness in different areas of the body” a more direct study. I understand that the theory doesn’t hold up with current knowledge of how the body works, but it still doesn’t invalidate the possibility unless a direct study like this is done by a reputable organization.

    However, I think that this type of research is probably looked down upon and “oppressed” just like psychiatric studies with things like DMT and psilocybin have been for years.. which was the ENTIRE REASON they never got any credibility as useful and not harmful chemicals from what I understand from the guy that actually pulled off getting funding.

    When I literally have photos of my own eyes changing color, and I see black spots in the exact areas my doctor recently told me I have issues with..

    When my doctor is ready to throw medication at me instead of suggesting her dietician…

    When I see people getting pumped full of drugs in nursing homes and nearly 90% (estimation) of all the medical staff are overweight, sucking down coffee with sugar, unhappy, greasy…etc

    I have to wonder… perhaps those who study medicine aren’t in the study OR BUSINESS of optimal health and wellness. Which is why I can’t fully trust their opinion on these matterss. Likely when I have an actual problem most of you can treat the symptom but rarely have I heard of actual solutions from from drs who practice medicine.

    Again, take for example the case of my grandfather who had an oversized prostate which needed to be surgically reduced in size. He said he would operate on him but made it a HUGE DEAL, and made us visit him in the hospital literally 8 times before we told him to go fuck himself. We found another doctor who didn’t see the risk the other doctor did, my grandfather did the surgery, and now he’s fine. Why these things happen? I don’t know. Perhaps from the outside perspective I just don’t know enough about the politics, policies, theories, laws, and experience different doctors have. But in the end, it just APPEARS as though one doctor loves to bill insurance companies, and the other just wanted my grandfather to be well.

  • Interesting that nobody seems to want to comment on DC’s link…

    What about this one…

    • Lucinda,

      It would be surprising if there were no genetic factors which influenced both the appearance of the iris and also the risk of particular diseases, even if the mechanism were simply linkage (i.e. two genes located close together on the same chromosome). This study for instance found an association between eye colour and endometriosis (specifically, in the study population the presence of deep endometriosis was associated with an increased chance that the subject had blue eyes; note that this is not the same as saying that blue eyes increase the risk of endometriosis).

      As I mentioned previously, there are other diseases which are well known to be associated with changes in the appearance of the iris, such as the Kaiser-Fleischer rings caused by deposits of copper in Wilson’s disease, and the arcus senilis, a common finding in people with high cholesterol. Also heterochromasia (different coloured eyes) is strongly associated with deafness in white cats, and of course albinism gives rise to red eyes as well as many other problems.

      None of this in any way validates iridology, which claims a specific and diagnostic association between subtle details of the appearance of the irises and the presence of a wide variety of diseases.

  • It is interesting that none of these critics have bothered to reply to Lucinda. Their attitude is typical of those who have closed minds. In medical history, many well qualified sceptics were proved wrong. Remember the work of Semmelweiss, remember the ignorance about scurvy, remember the ignorance about pellagra.

  • I love doctors and nurses, I love the passion and the love they have for helping people, saving lives and contributing to society.

    I just can’t understand the close minded attitude and bigotry, aloofness and almost religious-like regard for the sanctity of the medical establishment despite its myriad demonstrable and obvious flaws, dangers and the misery it has caused (alongside the good)

    This unwillingness to admit that as great as medicine is it doesn’t have nearly all the answers and the world of natural medicine has time and time again has taught the medical world.

    Some areas where medicine has gotten it wrong and been a danger to far more people than iridology has
    – Supporting smoking
    – Pushing the idea that humans need to eat meat and drink animal fat
    – Supporting the idea that people must eat 3 square meals a day and meals in between (while the natural medicine world has been teaching for millennia the benefits of restriction and periodic fasting (while medicine laughed)
    – The amount of fruits and vegetables one is supposed to consume (modern medicine has only recently caught up)
    – Downplaying the benefits of raw fruits and vegetables (modern medicine has only recently caught up)
    – Downplaying the benefits of limiting meat intake (modern medicine has only recently caught up)
    – Laughing at fasting (which the medical system now seems to be telling people they discovered)
    – Downplaying the benefits of meditation (modern medicine has only recently caught up)
    – Overprescribing pills and potions (still happening despite science showing how dangerous it is)
    – Cutting out tissue that they used to fee is superfluous (appendix)
    – Being great at telling people what they are sick with (with Latin words that state the obvious and are great for categorisation but not for explaining the causes) but seldom being able to tell someone why (still the case)
    – The millions of people that have died of misdiagnosis or incorrect prescriptions and other mistakes (still happening with no sign of letup)
    – The millions of people that have died from correct prescriptions and practices (still happening with no sign of letup)
    – And then there are the people the die due to poorly designed medicines, addictive medicines, medicines that create dependencies on other medicines (again still happening)
    – The list goes on and on and on

    Not saying that iridology is some magic bullet but maybe your people are missing something… like they have with so many things before. And so-called science-based medicine has done its fair share of damage despite the good, just look at the statistics around it.

    Why not work with the natural medicine world and bring it up to the standards of the medicine world and work together to help people rather than bicker like school children which is the majority I see in the comments. Put away the criticism and cynicism. Who knows… you guys could create something better than what already exists.

    • I think you are not missing just something but a lot; e.g.:
      nobody claimed medicine is perfect;
      all agree that it needs improving;
      plenty of people spend their time trying to do that;
      it’s done by testing and implementing the results;
      iridology has consistently failed the tests.

    • The one characteristic that marks out Western medicine as different from all of the alternative systems is that practice changes as new evidence becomes available. You have virtually said as much yourself. And yet you are describing health practitioners as close-minded.

      You give as an example that doctors have supported smoking. Yes, that is true, but not in my lifetime (I am sixty years old). In fact Doll and Peto’s first prospective study showing a link between smoking and lung cancer was published in the British Medical Journal in 1950. Doctors have supported many practices in the past which are now known to be useless or harmful, such as purging and blood-letting. Even your comments about diet are ignoring the fact when three square meals a day was the recommendation it was because malnutrition was rife.

      Nobody has ever suggested that medicine is perfect. If it were there would be no need for medical and biomedical research. Not only that, but the practice of medicine and the systems involved are also under regular review with the aim of improving them.

      Can this be said of any of the alternatives?

    • Some areas where medicine has gotten it wrong and been a danger to far more people than iridology has …

      [snip list of lament]
      Some basic observations:
      – As you implicitly admit (“modern medicine has only recently caught up”), modern medicine DOES change its mind when evidence emerges that their insights are wrong or obsolete.
      – As a rule, the ‘natural medicine world’ does NOT change its mind when evidence emerges that they are wrong.
      – And where modern medicine had it wrong in the past, the natural medicine world did NOT provide the right answers either.

      Also, quite a few of your arguments are disingeneous in that you appear to attribute certain insights to ‘the natural medicine world’ when they in fact emerged from science-based medicine, such as the role of a varied diet with enough fruit ‘n veggies.

      Why not work with the natural medicine world and bring it up to the standards of the medicine world?

      Medicine has been doing this for the past two centuries already: old medical knowledge based on tradition and insights from ancient authorities and practitioners has been scrutinized using objective scientific methods, in order to separate the things that don’t work from the things that do. It turned out that old-school (‘natural’) medicine was wrong about most things – things that were subsequently abandoned by regular medicine. The things that did (appear to) work, were adopted into regular medicine. And more often than not, these things were eventually superseded by still better insights when these became apparent.

      As a result of this long and arduous process, regular medical science has improved dramatically in the past two centuries, leading to huge improvements in almost all aspects of human life: a decrease in child mortality from ~25% to less than 0.5%, and a far healthier, longer life for most of us than our forebears could have ever imagined.

      One consequence of this huge progress in medical science is that after even 10 years of hard study, a medical doctor still only masters a relatively small portion of the complete body of medical knowledge – which is why we have specialists.
      And even then, as you correctly state, medical science does not know everything by far, and still gets things wrong. But they are still improving, abandoning older insights as they become obsolete, or as better things are found.

      What you are proposing however, is putting the cart before the horse: you suggest that we should go back at least 200 years in time, and start all over again with the long-obsolete ‘insights’ of people who have no medical or even scientific education, and are, for all intents and purposes, utterly incompetent in any medical sense of the word. Because that is what ‘the natural medicine world’ basically is: a bunch of people who believe in and practice all sorts of things that real medicine has abandoned long ago already, simply because these things turned out to be wrong.
      After all, you don’t propose that our chemical science could improve by reverting to old alchemical insights about this subject – insights that were proven wrong centuries ago already? Or should we start ‘integrating’ ancient Greek principles of physics into our modern-day physics classes again? And e.g. contemplate Aristotle’s fully erroneous insight that any object’s natural state is to be at rest, based on his observation that any motion eventually stops?

      And don’t get me wrong: if good, repeatable evidence emerges that certain principles or treatments from the natural medicine world actually hold water (even if it is shaken water), then real medicine will certainly take it seriously, and eventually adopt it. But those occasions are so few and far between (and I can’t even think of one right now), that it would be very foolish indeed to start taking ‘the natural medicine world’ seriously.

      Yes, you are right that our modern-day regular medicine still is far from perfect, and that efforts should continue to improve it. But it is a HUGE improvement over even the best that ‘natural medicine’ has to offer.

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