Iridology as a Diagnostic Tool

By Dónal P. O’Mathúna, PhD

The eyes are said to be a window to the soul. Could our eyes also provide portals into our bodies’ health? Iridology claims quite literally to do so. In a manner similar to practitioners of some other alternative therapies employing unique diagnostic methods, iridologists claim that every region of the body impacts a particular area of the iris. The patterns and colors of the iris are said to reveal important diagnostic information about the health status of every organ in the body.

Iridology has become particularly popular within certain schools of alternative medicine, with one textbook claiming it is "the most valuable diagnostic tool of the naturopath."1 The International Iridology Practitioners Association (formerly called the National Iridology Research Association) claims that iridology reveals how well people are "put together," what illnesses they will tend to get, the reasons for various symptoms, and the emotional and behavior factors influencing their health.2 This information is said to provide reliable guidance on the causes of current symptoms and the measures needed to prevent future illnesses.


Iridology has developed over the past 100 years or so, with some historical accounts claiming it developed from observations that birds manifest changes in their irides before and after injuries.3 Veterinary uses of iridology remain popular, but its efficacy has not been substantiated.

Iridologists claim that every organ and part of the human body is represented in a well-defined area of the iris. Weaknesses and strengths in the body manifest themselves by changes in the marks and colors of the iris. For example, changes in the kidneys would manifest themselves at the bottom edge of the iris, with the right kidney affecting the right iris and the left kidney affecting the left iris. Stomach changes would result in changes to the iris immediately above the pupil.

The diagnosis is carried out by direct observation of the eyes or by taking detailed photographs. Computer programs also have been developed to classify the patterns and colors observed. Iridologists examine the photographs and provide patients with lists of concerns based on the patterns seen. Various herbal remedies or dietary supplements often will be suggested to treat the conditions, or prevent them from developing.4

Mechanism of Action

Changes do occur in the iris when people have certain diseases, such as rheumatoid arthritis, and rarer conditions like heterochromic cyclitis, melanoma, and metastatic carcinoma.5 However, these changes occur throughout the iris, not in isolated regions such as described in iridology. Iridologists claim that a network of thousands of nerves connects all parts of the body to the iris through the optic nerve or the oculomotor nerve.6 Such claims have no basis in modern anatomy and physiology, leaving iridology without a plausible mechanism of action.

Clinical Studies

A systematic review of iridology, which included contacting prominent iridology associations, yielded 17 reports in various languages evaluating the reliability of diagnoses made with iridology.4 All the uncontrolled studies (many of which also were not blinded) concluded that iridology was a valid diagnostic tool. Given the potential for bias inherent to uncontrolled studies, only controlled, blinded studies will be reported here.

The first controlled study of iridology was a 1979 case-controlled, retrospective study.7 Photographic slides of the irides of 143 patients were taken using iridologist’s equipment. Creatinine levels were used to divide hospital in-patients into three groups of subjects: those with kidney disease (6.3-16 mg/dL; n = 24), those with moderate kidney dysfunction (1.6-4.9 mg/dL; n = 24), and controls with normal kidney function (0.5-1.2 mg/dL; n = 95). The photographs were randomly arranged using a random number table and presented to three iridologists. One of the iridologists (Bernard Jensen, DC) was regarded as the leading American iridologist and has written several books highly acclaimed by iridologists. The iridologists’ determinations of who did or did not have kidney disease were statistically no more reliable than chance (P > 0.05). Three ophthalmologists with no experience in iridology were asked to use any means possible to evaluate kidney function using the same photographs. One of the ophthalmologists did achieve statistical significance in correctly diagnosing kidney disease (P = 0.035); the other two did not.

A similar blinded case-controlled study was carried out with 39 patients scheduled to have their gallbladders removed.8 A photographic slide of each patient’s right iris was obtained using iridologists’ procedures. The presence of gallstones and inflamed gallbladders was confirmed during surgery the following day. A control group consisted of 39 subjects with no history of gallbladder disease or gallstones (confirmed by ultrasound). The photographs were randomly coded and sent to five Dutch iridologists who willingly agreed to participate in the study. Their determinations of the presence or absence of gallbladder disease statistically were no better than chance. The observed consistency between each pair of iridologists ranged from 47% to 64% with a mean of 60%, a value only slightly higher than chance.

The most recent study involved photographs from patients with ulcerative colitis (n = 30), coronary heart disease (n = 25), asthma (n = 30), or psoriasis (n = 30).9 Subjects in a control group were matched for age and gender. The photographs were randomly ordered and examined by a blinded researcher trained by practicing iridologists and also by a computer program approved by iridologists. No significant differences were found by either method between any group and its control for the presence or absence of any feature deemed by iridology to be connected to the diseased organ.

An earlier report published the results of two trials, one of which was masked.10 In one study an Australian iridology instructor was shown photographs of the irides of 15 patients who had been medically diagnosed to have a total of 33 health problems. The iridologist did not correctly identify any of these problems, but instead diagnosed 60 other problems that the patients had not reported. In the blinded trial, four patients had their irides photographed when they were healthy and again when diagnosed with various acute illnesses (pleurisy, gastroenteritis, upper respiratory tract infection, and cystitis). The iridologist made several incorrect diagnoses from the initial photographs and did not correctly identify any of the organs affected during the illness. A fifth subject was photographed twice within two minutes. The iridologist, unaware that this was a control, claimed to detect changes in the iris that indicated disease had developed between the time the photographs were taken.

Another small study presented two iridologists with eight pairs of iris photographs, but their diagnoses were inconsistent and inaccurate, with neither noticing that one pair of photographs was of a glass eye.11

Adverse Effects

Iridology itself is harmless, involving either examination or photography of the eyes. However, harm can occur if iridology is used exclusively and in place of reliable diagnostic tools. The dangers here are significant. For example, the researchers in the aforementioned controlled study of kidney disease calculated (using both the success rate of the best iridologist and the incidence of renal disease) that of those the iridologist diagnosed as having kidney disease, only 2.5% would actually have the disease.7 Such false negatives could lead to many people failing to get effective treatment when they have a serious illness. The least reliable iridologist concluded that 88% of those in the control group had kidney disease, even though they had no symptoms and medical tests revealed no kidney dysfunction. False positives would lead to unnecessary anxiety and initiation of superfluous interventions. Since many iridologists recommend dietary supplements and herbal remedies to treat the ailments they diagnose, patients may waste valuable resources or risk potential adverse effects with these supplements.


Iridology is a practice that is valued by some within alternative medicine, but which has no scientific basis. Moreover, the small number of well-controlled iridology trials has produced results suggesting the intervention to be unreliable at best.


Patients who present on the basis of iridology results should be encouraged to examine the evidence demonstrating the practice’s ineffectiveness. Some iridologists themselves have rejected the practice upon consideration of this evidence.6 However, practicing iridologists do not limit themselves to iris examinations, but make other observations and pursue relevant lifestyle information through questioning.9 All of this may lead to plausible diagnoses, though not because of iridology.

Patients should be encouraged to base decisions about treatment and preventive strategies on medically reliable tests. Prescribing treatments on the basis of iridology results is not consistent with the principles of evidence-based medicine, nor does it appear to serve the best interest of our patients.

Dr. O’Mathúna is Professor of Bioethics and Chemistry at Mount Carmel College of Nursing, Columbus, OH.


1. Fulder S. Handbook of Complementary Medicine. New York: Oxford University Press; 1988.

2. International Iridology Practitioners Association. Available at: Accessed April 12, 2003.

3. Murphy CJ, Paul-Murphy J. Iridology. Arch Ophthalmol 2000;118:1141.

4. Ernst E. Iridology: Not useful and potentially harmful. Arch Ophthalmol 2000;118:120-121.

5. Bartholomew RE, Likely M. Subsiding Australian pseudoscience: Is iridology complementary medicine or witch doctoring? Aust N Z J Public Health 1998;22: 163-164.

6. Mather JD. Confessions of a former iridologist: Do the eyes really have it? Available at: Accessed April 12, 2003.

7. Simon A, et al. An evaluation of iridology. JAMA 1979; 242:1385-1389.

8. Knipschild P. Looking for gall bladder disease in the patient’s iris. Br Med J 1988;297:1578-1581.

9. Buchanan TJ, et al. An investigation of the relationship between anatomical features in the iris and systematic disease with reference to iridology. Complement Ther Med 1996;4:98-102.

10. Cockburn DM. A study of the validity of iris diagnosis. Aust J Optom 1981;64:154-157.

11. Emory C. Iridology: Do the eyes have it? Nutr Forum 1989;6:4-5.

Administration of High-Dose Vitamin D to Prevent Fractures

Source: Trivedi DP, et al. Effect of four monthly oral vitamin D3 (cholecalciferol) supplementation on fractures and mortality in men and women living in the community: Randomised double blind controlled trial. BMJ 2003;326:469.

Goal: To determine whether the use of high-dose vitamin D administered every four months would have a positive effect on fracture risk and all-cause mortality.

Design: Randomized, double-blind, placebo-controlled pilot trial performed over five years.

Subjects: A total of 2,686 men and women ages 65-85 years recruited from British physician registers (2,037 men, 649 women).

Methods: Subjects were randomized to receive by mail, and then immediately take, either 100,000 IU of cholecalcif-erol or a matching placebo every four months for a total of five years.

Upon receipt of the capsules, participants were also to fill out forms listing medical events, including fractures.

Four years into the study a modified food frequency questionnaire was employed to estimate dietary calcium intake, and 235 subjects were invited to have serum parathyroid hormone and vitamin D concentrations determined.

Results: Differences appeared one year into the study. A lower fracture rate was found in the vitamin D-treated group as compared with placebo (22% lower rate for first fracture regardless of site, and 33% lower rate for fractures at major osteoporotic sites including the hip, wrist, forearm, and vertebrae).

A lower rate of all-cause mortality found in the vitamin D-treated group did not reach statistical significance. Mean vitamin D concentrations were 40% higher in those who received the active treatment.

Conclusion: A dose of 100,000 IU of vitamin D administered orally in an every-four-month schedule helps prevent fractures in people older than age 65.

Study strengths: Minimal exclusion criteria (generalizable); good compliance with protocol.

Study weaknesses: Majority of data obtained was self-reported by participants; inherent weaknesses associated with food frequency questionnaires.

Of note: The every-four-month dosage schedule of 100,000 IU vitamin D is equivalent to a daily dose of 800 IU vitamin D. Also, parathyroid hormone levels were not affected significantly with the dosage regimen studied in this trial. No adverse effects were reported.

We knew that: The majority of fracture prevention trials have focused on women with osteoporosis or previous fractures.

Clinical import: The conclusions of this well-done pilot trial strongly suggest that a high-dose regimen of vitamin D offered on a schedule that promotes compliance (once every four months) can significantly lessen fracture risk in older adults. Keeping in mind the graying of the population and the well- recognized complications associated with fractures in the elderly, such an intervention could have widespread health benefits—across socioeconomic boundaries.

What to do with this article: Keep a hard copy in your file cabinet.