Iridology is defined by proponents as a study of the iris of the eye to detect weakness or illness in specific body tissues. Based on that assessment diet and herbs are used for treatment. Areas which can be assessed include physical, mental, sexual, and emotional.
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Scientific Evidence
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The descriptions of the anatomy and physiology of the iris-body connection vary from text to text. Most texts claim that the optic nerve carries impulses from all over the body to the iris. A brief text describes it:
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“The nerve fibers (of the iris) receive their impulses by way of their connections to the optic nerve, optic thalami and spinal cord (6:3).”
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However, a survey of scientifically reputable literature shows there is no connection between the iris and optic nerve.
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“All of the accumulated research unequivocally demonstrates that the mammalian optic nerve...is...one in which the signals travel from (emphasis added) the eye to the brain. There is no evidence suggesting that any fibers from the optic nerve make connections with the iris. This, combined with the fact that only half of the fibers in the optic nerve cross, makes the proposition that the optic nerve is the final link to the iris untenable (12:173).”
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Some iridologists claim that the connection from the nervous system occurs through the autonomic system. Even here there is disagreement, as some claim it is the sympathetic, while others opt for both sympathetic and parasympathetic connections. Reputable research on the eye shows:
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“Anatomical, physiological, and clinical studies have eloquently demonstrated the functional neural pathways involved in many of the eye’s control and response mechanisms, [Note: the autonomic nervous system] but published studies report no evidence in support of a functional iris-body connection (12:171,172).”
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A common claim is that “It (the iris) is an extension of the brain” (6:3).
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Anatomically the tissue of the eye as a whole developed from the same embryonic neural tube which is also the source of the brain developmentally. The iris is indeed incredibly delicate tissue. It is not, however, nerve tissue as are the brain and nervous system.
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Iridologists have failed to produce objective, verifiable evidence to support either their theories or applications of iridology. Iridology has been examined in studies using controls at UC-San Diego (1979), University of Melbourne (1981), and University of Limburg-The Netherlands (1988). In not one of these studies were the claims of iridology found to be valid.
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