He also selected a group of people who did not have diseased gall bladders to act as a control. A group of 5 iridologists examined a series of slides of both groups' irises. The iridologists were not able to identify correctly which patients had gall bladder problems and which had healthy gall bladders. For example, one of the iridologists diagnosed 49% of the patients with gall stones as having them and 51% as not having them. Dr Knipschild concluded: "this study showed that iridology is not a useful diagnostic aid." Iridologists defended themselves and attacked the methodology of the study.
Source: Wikipedia > Iridology
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