From Forbes:
A study done at the University of California, Irvine discovered that people who have a darker limbal ring – that’s the border of the iris – were found to be more attractive. Having a more defined limbal ring makes the whites of your eyes look brighter, helping you appear younger and healthier. But as we age, the limbal ring tends to fade and become less pronounced.

For the full story, please visit http://www.forbes.com/sites/celiashatzman/2014/11/18/the-secret-to-younger-brighter-eyes/.