The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Quantitative measures of iris color using high resolution photographs


1Anthropology, University of Toronto Mississauga, 2Photography, Miles Research

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Our understanding of the genetic architecture of iris color is still limited. This is partly related to difficulties associated with obtaining quantitative measurements of eye color. Here we introduce a new automated method for measuring iris color using high resolution photographs. This method extracts color measurements in the CIE 1976 L*a*b* (CIELAB) color space from a 256 by 256 pixel square sampled from the 9:00 meridian of the iris. Color is defined across three dimensions: L* (the lightness coordinate), a* (the red-green coordinate), and b* (the blue-yellow coordinate). We applied this method to a sample of individuals of diverse ancestry (East Asian, European and South Asian) that was genotyped for the HERC2 rs12913832 polymorphism, which is strongly associated with blue eye color. We identified substantial variation in the CIELAB color space, not only in the European sample, but also in the East Asian and South Asian samples. As expected, rs12913832 was significantly associated with quantitative iris color measurements in subjects of European ancestry. However, this SNP was also strongly associated with iris color in the South Asian sample, although there were no participants with blue irides in this sample. The usefulness of this method is not restricted only to the study of iris pigmentation. High-resolution pictures of the iris will also make it possible to study the genetic variation involved in iris textural patterns, which show substantial heritability in human populations.

Esteban J. Parra was supported by the Early Research Award (ERA) from the Government of Ontario, the Natural Sciences and Engineering Research Council of Canada (NSERC), The Canada Foundation for Innovation (CFI) and the Ontario Innovation Trust (OIT). Melissa Edwards and Agnes Gozdzik were supported by scholarships from NSERC (NSERC CGS M to Melissa Edwards and NSERC PGS D to Agnes Gozdzik, respectively).

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