Technical note: Quantitative measures of iris color using high resolution photographs
Article first published online: 19 NOV 2011
Copyright © 2011 Wiley Periodicals, Inc.
American Journal of Physical Anthropology
Volume 147, Issue 1, pages 141–149, January 2012
How to Cite
Edwards, M., Gozdzik, A., Ross, K., Miles, J. and Parra, E. J. (2012), Technical note: Quantitative measures of iris color using high resolution photographs. Am. J. Phys. Anthropol., 147: 141–149. doi: 10.1002/ajpa.21637
- Issue published online: 14 DEC 2011
- Article first published online: 19 NOV 2011
- Manuscript Accepted: 11 OCT 2011
- Manuscript Received: 26 JUN 2011
- Government of Ontario (ERA), Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundation for Innovation (CFI), Ontario Innovation Trust (OIT)
- iris pigmentation;
- quantification of eye color;
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. Am J Phys Anthropol, 2012. © 2011 Wiley Periodicals, Inc.