Iridology: Biological plausibility, clinical evidence, and implications for ophthalmic practice

Iridology is an alternative diagnostic practice that claims to identify systemic diseases and organ dysfunction through visual inspection of iris features, including pigmentation patterns, crypts, furrows, and discolorations. Despite its continued presence within complementary and alternative medicine, iridology has not been incorporated into mainstream medical practice. This review critically examines iridology from an ophthalmologic perspective, addressing its historical origins and epistemological foundations, proposed mechanisms, biological plausibility, and clinical evidence. A systematic appraisal of the available literature, including the most recent government-commissioned evidence evaluation, demonstrates a consistent lack of diagnostic accuracy, reproducibility, and pathophysiological rationale. The ethical and clinical implications of iridology use are discussed, with particular attention to the risk of delayed diagnosis and patient misinformation. Based on the totality of evidence, iridology cannot be supported as a diagnostic or screening tool in ophthalmology or general medicine.