Iris Color: Validation of a new Classification and Distribution in a Spanish Population-Based Sample

Abstract

Purpose To design and validate a standard, simple, and reliable iris color classification and to study its distribution in a Spanish population. Iris color has a geographic distribution and has been correlated with different ocular diseases. However, there is no standard and validated iris color classification allowing comparison among different studies. Methods Classification was made in three grades (blue-gray, hazel-green, brown) and was validated by 3 independent readers. Initially, a preliminary study was made in 50 iris photographs to detect technical hitches. Afterwards, based on this procedure, 221 iris photographs were graded Results Measures of interobserver reliability were 0.786 by kappa index with an agreement of 89.6%. Iris color distribution in the Spanish cohort was blue-grey 16.29%, hazel-green 55.2%, and brown 28.5%. Conclusions This classification is simple, reliable, and easy to use in clinical research and by ophthalmologists or generalists in practice. The Spanish cohort from this study shows a different iris color distribution from those previously published in other countries.