If you're looking for a diagnostic tool to help pinpoint problems in your body, visiting an iridologist could be the solution. [...] A practitioner can make inferences about the body areas or organs that will help them make a diagnosis and treatment plan for each client. "While iridologists do not diagnose disease, they do analyse tissue conditions such as inflammation, weakness, degeneration and hypo or hyper activity from the various signs of each iris," Ms Schreuders said. [...] Your first consultation will generally last an hour. "A picture is taken of the patient's eyes and a detailed medical history is taken," Ms Marriott said.
If the detailed and wholly revealing medical answer is right there in the eyes, why do they spend an hour taking a "detailed medical history"? Because, just like psychics, the more clues they get from you, the more accurate they make their guesses seem. And why is it repeatedly referred to as "diagnostic" when these healers-cum-psychics only make "inferences"?
From EoR's observation of an iridologist in full flight, the "consultation" involved asking a lot of leading questions such as "Any health problems?", a bit of mysterious eye-gazing (the equivalent of the magician's handwaving) and then a few comments about some fairly nonspecific conditions that someone of that age and with those health problems could be expected to have.
Iridologists don't believe in green eyes. "Genetically, there are only blue or brown eyes - all other colours result from iris fibre changes or deposits in the eyes which, from a natural therapies perspective, indicate a variety of conditions in the body." Many green-eyed people have blue eyes discoloured by cloudy particles in the iris that could indicate a health problem - often a congestion of the lymphatic system.
Isn't it a wonderfully simple world the iridologists live in? Green is not an eye colour (EoR wonders what nasty - presumably genetically transmitted - health diseases, black, grey, hazel or albino irises "may" indicate). In reality, eye colour is a result of a complicated set of genes determining the amount of melanin in the iris, flecks, rays, rings, and diffusion patterns.
What genes determine eye color in humans? At one time, scientists thought that a single gene pair, in a dominant-recessive inheritance pattern, controlled human eye color. The allele for brown eyes was considered dominant over the allele for blue eyes. The genetic basis for eye color is actually far more complex. Two key genes for eye color are located on chromosomes 15 and 19. The Bey2 gene (also called EYCL3), on chromosome 15, has a brown and a blue allele. A second gene, located on chromosome 19 (the Gey gene, or EYCL1), has a blue and a green allele. Geneticists have designed a model using the Bey2 and Gey genes that explains the inheritance of blue, green, and brown eyes. In this model, the brown allele of the Bey2 gene is always dominant over the blue allele, so even if a person is heterozygous (one brown and one blue allele) for the Bey2 gene, the brown allele will be expressed. The green allele of the Gey gene is dominant to the blue allele of either Gey or Bey2 but is recessive to the brown allele of Bey2. This means that there is a dominance order between the two genes. If a person has a brown Bey2 allele and all other alleles are blue or green, the person will have brown eyes. If there is a green Gey allele and the rest of the alleles are blue, eye color will be green. Blue eyes will occur only if all four alleles are for blue eyes. This model explains the inheritance of blue, brown, and green eyes but cannot account for gray, hazel, or multiple shades of brown, blue, green, and gray eyes. It cannot explain how eye color can change over time. This suggests that there are other genes, yet to be discovered, that determine eye color or that modify the expression of the known eye-color genes. One such gene may be controlling the deposition of the pigment lipofuscin (lipochrome) in the iris and may determine amber, green, and violet eye colors.
In the iridologists' world, there's still only a single gene pair (assuming, which might be a presumption, that they even believe in "genes") and such things as "weak" organs and "congested" systems.
Iridology also practices its own anatomy which bears no relation to anatomy as it is known in all living humans:
The theory is that the iris contains nerve fibers connected to various parts of the body through a previously unknown nerve pathway in the cranial nerves.
From the same page also comes an example of how confirmation bias plays such a large part in this scam:
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.
And here's that psychic trick again:
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.
Is that any different from "I'm getting an M or an A. Does that mean anything to you?"?
Evidence for such a fundamentally flawed hypothesis is also thin on the ground:
There is no proven scientific basis for iridology. Several studies in humans report that iridology is not effective for diagnosing disease.
Preliminary research suggests that iridology may assist in the identification of individual predispositions for vascular diseases such as hypertension. Further research is needed to confirm these findings.
In terms of magic, however, and its uncanny ability to generate an income stream, iridology is a marvel of madness.