Iridology is the centuries old art and science of examining the iris of a patient’s eyes to gather clinically relevant information. It is based on the observation that specific areas in the eyes are reflexively linked with specific areas of the rest of the body. Over many years of observation, eye charts have been developed that map the different areas of the eyes to the different areas of the body. Iridology is thus a very empirical endeavour.

Many people find it strange that other parts of the body would be reflected in the eyes. However, once one considers how intimately the eyes are linked with the rest of the body, this idea does not seem so farfetched.

As an embryo develops, the iris originates from the same layer of tissue that gives rise to the nervous system, called the ectoderm. Specifically, the eyes and the thalamus both emerge from the diencephalon. Technically, the optic nerve is thus continuous with and part of the central nervous system (the brain), rather than the peripheral nervous system.

The eyes are innervated by 4 of the 12 cranial nerves. The eyes also contain all four of the tissue types: epithelial, connective, muscular and nervous tissue, as well as being supplied with the nutritive fluids of blood and lymph.

As sensory organs, the eyes send information directly to various structure in the thalamus and the midbrain. From here the information is integrated and relayed to many other areas of the brain, including a close association with the hypothalamus, and the pituitary and pineal glands. These structures are very important control centres, affecting the entire body. The input from the eyes thus affect the body hormonally, biochemically, structurally and metabolically. All of these influences feed back to the eyes themselves, potentially changing the appearance of the various structures of the eyes – iris, sclera, cornea, pupil, conjunctiva and retina.

Besides these physiological and anatomical connections between the eyes and the rest of the body, it is also interesting to consider the implications of the research of Dr Mae-Wan Ho as it applies to iridology. She discovered through imaging studies that the tissues of living organisms have a liquid crystal structure, which means that the molecules making up our cells and tissues are not arranged randomly but conform to a regular matrix structure – like a crystal. This is a staggering finding – to think that our bodies are coherent, all the way down to a molecular level. If each part of us is exactly in tune with every other part, it is not hard to believe that looking at the iris could give us information about the rest of the body.

The main structures of the iris are stable and are largely solidified by the time a person is born. The appearance of these structures can give iridologists clues about the constitution and predispositions of a person. As such, it is a valuable tool in preventative medicine – providing warning about potential weaknesses in the body that can be compensated for before problems arise. However, the appearance of some features of the iris are transient and do change over time. These can provide clues about the influence of a patient’s lifestyle, emotional state, mental processes, etc. on their wellbeing.

The best use of iridology is as an adjunct to other diagnostic techniques – it provides an additional perspective to view a patient from. It can corroborate diagnoses made using other diagnostic techniques as well as suggest specific areas to investigate more carefully.

In our age, scepticism is an appropriate default stance to adopt given the widely divergent views we are continually confronted with. However, many people think being sceptical means dismissing things that appear to contradict their worldview out of hand. The truth is, being sceptical requires having an open mind and a willingness to investigate things. It means reserving judgement until an informed verdict can be reached. So give iridology a try and see if it yields useful results – as William Blake wrote, “The true method of knowledge is experiment.”