This little piece of nonsense relates to the perception that disease of the body appears as defects or distinguishing marks in the iris. In essence if you are sick, have been sick, or will be sick then the details of the past/present/future illness will be detailed in flecks of colour in your eyes. This requires that each part of the iris maps to a corresponding part of the body and be physically connected in some manner in order for the transfer of this information. Strangely enough no evidence of these connections has ever been found during the centuries of medical research that has been done on the human body.
Ok so maybe there’s no biologic plausibility but maybe but maybe it works anyway. What we would expect to see then would be for practitioners to be able to acurately diagnose disease without input from the patient merely by examining photographs of the eye. For there to be any diagnostic relevance to flecks in the iris this must be the case. Sadly no, when practitioners are given blinded photos and even told what disease they are to diagnose they don’t even come close to getting it right let alone get any statistically significant hits.
This strongly implies that the practice of Iridology contains aspects of Cold reading when applied to live patients, in that the practitioner can gather information about the patient to help with the diagnosis and let the patient fill in any gaps or make leaps to known problems. There is also an aspect of confirmation bias whereby the occasional resounding success, which would be expected by chance over a large number of patients, is remembered and played up while the larger number of incorrect or vague diagnoses are forgotten. This also brings new meaning to “That dress brings out the colour of your eyes”