Objectives Iridology is a field of study that diagnoses various systemic diseases through analysis of colors, structural characteristics and changes in iris. The purpose of this study was to review previously published study results of the iridology. Methods The studies were searched with the keyword "iridology" through search engines such as SCOPUS, Pub med, RISS, and NDSL. Total of 36 iridology-related studies published from 1980 to 2012 were analyzed. Results Most diagnoses of systemic disease through iris markings were insignificant. The studies on relevance of gene polymorphism and iris constitution were highly significant. The studies on relevance of Sasang constitution and iris constitution varied in results depending on diagnosis methods. The studies on relevance of iris constitution and diseases had significant results. The structural characteristics of iris were related to certain personality. Conclusions The studies on utility of iris diagnosis and diagnostic markings were negative, but the relevance of constitution, heredity, and iris diagnosis was positive. A persistent in-depth study on relevance of iris and constitution is needed in the future.