Eye color and the prediction of complex phenotypes from genotypes

Population characteristics The Rotterdam Study is a population-based prospective study of subjects aged 55 years or older [S1,S2]. Collection of eye (iris) colour data and purification of DNA have been described in detail previously [S3]. In brief, each eye was examined by slit lamp examination by an ophthalmological medical researcher, iris color was graded by standard images showing various degrees of iris pigmentation and categorized into blue, brown and non-blue / non-brown called here intermediate. The Medical Ethics Committee of the Erasmus Medical Center approved the study protocol, and all participants provided written informed consent. Individuals identified as outliers using an identity-by-state analysis as described previously [S4] have been excluded because they most likely represent individuals of non-European ancestry.