Distribution of Iris Colors and its Association with Ocular Disorder in the Tehran Eye Study

Purpose: To determine the distribution of iris colors in the population of Tehran and to assess possible associations between iris color and Ocular disorder Methods: Through a stratified random cluster sampling approach, 160 clusters were selected in different municipality districts of Tehran, and the approached households were invited to a clinic. After the initial interview, all participants had complete eye examinations and their iris color was categorized as grey/blue, yellow/green, light brown, medium brown, and dark. Distributions were determined in percentages and possible correlations with race, refractive errors, visual impairment, cataracts, age-related macular degeneration (AMD). Intraocular pressure (IOP) was also examined. Results: Out of 4230 participants aged 7 years or more, the iris color was determined in 4200 people; in 54.09% [95% confidence interval (CI) 51.74% to 56.44%] the iris color was medium brown as the most prevalent color, and in 1.96% (95% CI: 1.43% to 2.48%) the color was grey/blue as the least prevalent color. The inter-gender difference in iris color was not statistically significant (P=0.288). AMD showed the highest prevalence in light brown iris colors (P<0.001). Nuclear cataract and posterior subcapsular cataract (PSC) was significantly correlated with iris color, with higher risks of cataract among medium brown, light brown and yellow/green iris colors (P<0.001). Conclusion: The most prevalent iris color in the population of Tehran was medium brown. In light of the observed correlation between the iris color and certain conditions such as cataract and AMD with lighter eye colors, further studies are recommended to investigate the probable associations.