Iridologists believe--or at least they say they believe it--that they can diagnose all sorts of physical and mental illnesses by studying the appearance and location of features on the iris of the eye. The claim that the iris can be directly mapped to various organs and regions of the human body, and that certain features can signify specific illnesses in the mapped regions. For example, they claim the part of the iris near the six o'clock position correlates to the kidney. Features located in this area denote illness or disease of the kidney.
Iridology generally limits it's scope of malpractice to diagnosing illness. I suspect this explains why all manner of alternative medicine crackpots use it as a launch pad to sell their various incarnation of "treatment." Anybody looking for a way to justify their particular brand of nonsense can diagnose some malady using iridology. After that, guess what, they have the perfect cure! They might be selling natural supplements, magnets, homeopathic remedies, or whatever--iridology makes a great segway into all of them.
Lest there be any doubt, this particular field of idiocy has been the subject of many wasted research dollars. Taken as a whole, which is the way medical literature should always be taken, the research confirms that iridolgy is worthless. There are certain recurring patterns seen in the scientific literature surrounding subjects like this:
- The better the quality of the study, the worse the quackery performs.
- The pseudoscience always seems to yield results that are just barely beyond the border of significance, even with increasingly rigorous protocols. This is often used to justify provisional acceptance while "awaiting further study."
- Quacks support their quackery with vague, feel-good rhetoric that boils down to nothing of substance.
- The quacks try to use an imperfect understanding of a disease or condition as evidence in support of their quackery. This is really a poorly-veiled argument from ignorance ("I don't understand what is happening here, therefore it must be due to my snickelfritz").
The literature on iridology uses all of these. The bottom line: absolutely no decent evidence supports the premises, or the practice of iridology. The best studies that have been done on the subject prove it is crap. But, crap is a subject for another post...