From http://www.netasia.net/users/truehealth/Iridology.htm by Health Frontiers Center for Quackery Control, Inc., an affiliate of the National Council Against Health Fraud.   A Philippine skeptical website. 

Looking for a non-invasive way of examining your body? Tired of all those expensive medical tests? Afraid of going under the knife or being exposed to x-rays?

Practitioners of iridology claim they can help you just by looking at the iris, the colored portion of the eye. This system of iris analysis can supposedly detect subconscious tensions, hereditary weaknesses, and states of health and disease.

Although they can’t really say what’s wrong with you, iridologists claim their unique method can alert you to "imbalances" which can be treated with vitamins, minerals or herbs.

How It Started

No one knows when this practice started but Dr. Ignatz von Peczely of Hungary is credited as the promoter of this "science." The story goes that at the age of 10, Peczely accidentally broke an owl’s leg and saw a black stripe in its eye. He took care of the bird and later noticed that the stripe slowly disappeared as the owl got well. Peczely eventually became a doctor and saw the same changes in the irises of accident victims. From there, he concluded that all diseases were reflected in the iris of the eye.

The Holistic Health Handbook says there are over 10,000 iridologists or iridiagnosticians in Europe and over 1,000 in the United States. The most popular proponent of this art is Dr. Bernard Jensen, an American chiropractor who has written 2 books on the subject. Iridology is also popular in France and in Belgium and many organizations exist such as the National Iridology Research Foundation and the Iridology Foundation of the Philippines.

What the Zones Say

Iridologists believe the iris is divided into 40 zones, each corresponding to different body parts. These zones and their bodily connections were made by Peczely himself who published a book on iridology in 1866.

By looking at a particular part of the iris, iridologists say they can determine which body part or organ has a problem. Warning signs include abnormal spots, colors or lines.

In the early days, these signs were seen with the help of a magnifying glass and a torch. The modern iridologist now uses a special camera and makes slides that are projected onto a screen. These are then compared with iris charts based on the ones Peczely devised. As E.G. Bartlett said in Healing Without Harm:

"It is in the eye that the nervous system comes to the surface. And the iris reflects all parts of the body, and even the mind and the spirit. The lines, flecks, and pigments guide the iridologist not only to what is wrong at the moment of examination but also to what may have been wrong in the past or may go wrong in the future. It should be said, however, that it does not show up specific illnesses; rather it indicates the things a patient may be prone to: congestion of the digestive system, circulation problems, stomach acidity, tendency to a weak heart, these are the kind of things that show up, and they may develop into problems or they may not. At least the pin-pointing of the danger spots and signals can alert the patient so that he can take preventive measures.

"The left iris corresponds with the left side of the body; the right with the right side. At the top of the iris information relating to the brain and the heart is to be found; in the center the stomach and the organs of digestion; moving outwards, indications are given as to the intestines and the colon; still further, the kidneys, the liver, the back, and the skin. Bluish rings round the outer rim of the iris can show stress problems; pupil size is related to nervous response; textural appearance indicates recuperative ability," Bartlett adds.

Shortcomings of Iridology

Strangely, the "science" of iris analysis is not taught in medical schools nor is it practiced by competent doctors. Why is this so? First, doctors say there is no anatomic evidence which shows that the iris is connected to certain organs. Iridologists contend that the neuro-optic reflex somehow links the iris to the body via the sympathetic nervous system. But even if this were so, that doesn’t mean the iris can automatically tell you what’s wrong with your body. As Dr. Russell S. Worrall, coordinator of the Special Task Force on Vision-Related Misinformation of the National Council Against Health Fraud, Inc. (NCAHF) said in Iridology: Diagnosis or Delusion?:

"Anatomical interconnection does not imply functional connection any more than having a telephone in your home is proof of the proposition that you receive all of the calls intended for the president of the United States. Further, the autonomic nerves supplying the eye are of small caliber and would not seem to have adequate numbers of nerve fibers to handle the volume of information presumed to reach the iris. Anatomical, physiological, and clinical studies have eloquently demonstrated the functional neural pathways involved in many of the eye’s control and response mechanisms, but published studies report no evidence in support of a functional iris-body connection."

Medical science does concur that the eyes may reveal certain illnesses like tuberculosis, arteriosclerosis and drug use. A muddy or clouded iris, for instance, may indicate rheumatoid arthritis; dilated pupils may signal glaucoma or brain injury; while bloodshot eyes may be caused by measles or conjunctivitis. But these symptoms don’t always appear with these disorders. Nor are they confined to certain segments of the iris.

Confusing Charts

Secondly, iridologists themselves can’t seem to agree on how to diagnose their patients. Their observations and evaluations of the iris are taken from 20 different charts which each show the iris in a wide combination of connections to various body parts. Thus, a patient who sees different iridologists is likely to end up with 20 different diagnoses depending on which chart is used.

"Although most charts are in general agreement on major landmarks such as the leg area being represented at the six-o’clock portion, there are also many differences in both location and interpretation of the iris signs," Worrell said in his article in Examining Holistic Medicine edited by Douglas Stalker and Clark Glymour.

The shortcomings of iridology were apparent way back in the early 1900s when its practitioners failed to identify what was wrong with their patients. In Not Necessarily the New Age, Alan M. Mac Robert, editor of Sky and Telescope magazine, said, "the method never produced any results and so it slowly faded away." But not for long. The holistic health scene has given new life to this old racket. Still, current studies have shown that nothing has changed: iridology remains an unreliable diagnostic tool.

Studies Debunking Iridology

The first one was made in 1979 by University of California at San Diego researchers A. Simon, D. Worthen and J. Mitas. The researchers asked three iridologists, including Jensen, to analyze the kidney function of 143 patients based on color slides of their irises. Of that number, 24 subjects had severe kidney disease, 24 others had moderate kidney disease, and 95 had no problems whatsoever.

The funny thing is that none of the iridologists could detect which patients had kidney trouble. Worse, those who had kidney disease were told they were fine, while those who weren’t sick were informed that they had a kidney problem. Obviously, the diagnostic skills of an iridologist are no better than guesswork.

In another study made in 1981, D. Cockburn of the University of Melbourne in Australia asked iridologists to evaluate iris photographs of people with serious diseases. Again, they failed to do so.

"More recently, five leading Dutch iridologists flunked a similar test in which they were shown stereo color slides of the right iris of 78 people, half of whom had gall bladder disease. None of the five could distinguish between the patients with gall bladder disease and the people who were healthy. Nor did they agree with each other about which was which," revealed Drs. Stephen Barrett and Victor Herbert in The Vitamin Pushers.

In defending his art, Jensen claimed the color slides used in the first study were of poor quality, making it difficult for him and his colleagues to diagnose the subjects. But this was not case according to nutritionist Kurt Butler in A Consumer’s Guide to Alternative Medicine:

"The camera used belonged to one of the iridologists, and the slides were presented to them in their offices, at their leisure, and with the option of discarding any slides they thought unsatisfactory."

Jensen also says that the first study merely proves that iridology can’t assess kidney function but has other diagnostic uses. If so, why did he and his colleagues agree to be tested in that manner? Why did they participate in the study if they knew all along that they couldn’t detect kidney disease? And what about the 2 other studies which iridologists flunked too?

No Clinical Value

To save face, iridologists claim their art has been around for more than 125 years. Surely, it couldn’t have lasted that long if it didn’t have any value at all. But tradition and old age have nothing to do with credibility. For example, crime and prostitution are definitely older than iridology but that doesn’t make them acceptable or respectable in our society.

"It is clear from a logical, theoretical, and clinical perspective that iridology is a pseudo-science of no clinical value. Unfortunately, the use of iridology by unorthodox practitioners is all too common today, and the unsuspecting and often vulnerable patient in the clinical application of the science is the recipient of its presumed benefits…. This is an area of great concern to everyone in the health professions, because acceptance of this pseudo-science can lead an individual to delay needed treatment when a false-negative diagnosis is made (i.e., when a disease is present but not detected)… On the other hand, when a false-positive finding is reported (i.e., when a disease is ‘detected’ but not present) to a naïve patient, extreme mental anguish can result. In addition, the patient may expend large sums of money on unneeded treatments or (if they are skeptical) on traditional diagnostic tests to confirm the reported non-disease," Worrell said.

"To think that inspecting the eye will reveal illness in vital organs and other parts of the body is purely wishful thinking. This practice belongs in a carnival sideshow. On second thought, it doesn’t belong there either," added Henry Gordon, a magician and fellow of the Committee for the Scientific Investigation of Claims of the Paranormal (CSICOP) in Channeling Into the New Age.