Iridology

Our eyes have been said to be "windows into our souls"; Hungarian physician, Dr. Ignatz Perczely believed that an individual's iris could not only look into their soul, but also 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" (1). When Dr. Peczely was a young boy, he found an owl with a broken leg. At this time, Dr. Peczely also noticed that the owl had a prominent black stripe in the iris of one eye; after nursing the owl back to health, the black line was gone and ragged white lines had taken its place (1). Dr. Ignatz studied at the Viena Medical College in 1867, where he was able to observe hundreds of patients' irides before and after surgeries (2); he went on to publish his research in his book, Discoveries in the Realms of Nature and Art of Healing and established his "Iris Chart" in 1880 (2), as seen below. The basic approach to iridology stems from a treatment known as the homunculus approach, which explains that one part of the human body maps to the rest of the body (2).

The problem with Dr. Ignatz's "Iris Chart" was that he invented the maps as a product of his imagination and the result of confirmation bias, not from actually scientific research. There were no blinded experiments or studies used to prove his theory. Sadly, iridology has survived and specifically in the U.S. can be traced to chiropractor, Bernard Jensen, who published the book, The Science and Practice of Iridology in 1952 (2); in the U.S., you can get a diagnosis from a naturopath Frank Navratil for only $150 (2). However, these "readings" are only medically cold readings, the iridologist will ask the patient about certain health issues, and if present in any form the theory is validated, but actual research has proven iridology has no effect and provides no useful information.  

(1)- http://www.gni-international.org/the-history-of-iridology/
(2)- https://www.sciencebasedmedicine.org/iridology/