July 15, 2010 at 10:40 AM ETWondering what it is about Kate Bosworth’s looks that are so riveting? It just might be her distinctive irises. Born with heterochromia, Bosworth has one blue eye and one eye with sectors of both hazel and blue.It’s a rare defect that many people find irresistible.“It’s definitely been my ace in the hole,” says Ingrid Ingerson, a 36-year-old Seattle program assistant who also has sectoral heterochromia. She has hazel eyes with a splash of brown in her right eye. “It’s always been a hit with the boys. Not that I care about that now that I’m married, but it’s still part of my cachet and part of my mystique.”According to Dr. Ivan Schwab, an ophthalmology professor at UC Davis, heterochromia occurs more frequently in cats and dogs and is uncommon in humans, affecting only about 1 in 10,000 people. It’s often genetic — usually due to an excess or lack of melanin in the iris — but it can also be caused by injury, inflammation, tumor or medications, such as eye drops for glaucoma or eyelash enhancement.In some people, heterochromia produces two completely different-colored irises. Actress Jane Seymour has one green eye and one hazel eye. Others have a colored sector (like Bosworth) or will have central heterochromia, which is basically a ring of extra color between the pupil and the iris.“Central is pretty common,” says Schwab. “If you look really close in a person with blue eyes, at the margin [of the pupil] you’ll see lots of yellow dots that will blend in when you step away. It’s sort of the difference between a light blue and a steely blue.”Inherited heterochromia is harmless, although acquired may be a different story, says Schwab. The worst part of it is dealing with people who’ve never encountered it before.Slideshow: Celebrities with unusual eyes“Some people can’t let it go,” says Ingerson. “They’ll say, ‘What’s wrong with your eye?’ ‘Can you see out of it?’ They … want to know if it hurts. They always go to the place where it’s a problem or a malady.”Other common questions – gleaned from a “People With Sectoral Heterochromia” Facebook page – include: “Is that a glass eye?”; “I think your eye is bleeding”; and “Wow, you look just like a Husky.”While constant questions can be off-putting, most people seem to like it.“It’s exotic,” says Schwab, the ophthalmologist. “It’s striking and it makes them different.”It might even give them a certain star power. In addition to Bosworth and Seymour, luminaries sporting some form of heterochromia include actors Kiefer Sutherland, Christopher Walken, Dan Aykroyd, and Elizabeth Berkeley; singer/songwriter Carly Simon; baseball pitcher Max Scherzer; and by some reports, Alexander the Great.David Bowie, perhaps the most famous “heterochromiac” in existence, actually has an enlarged pupil in one eye, courtesy of a fistfight in his youth, which gives the appearance of two different-colored irises.Are you a heterochromiac? Tell us about your multicolored eyes in the comments.To read more Body Odd posts, click here. You can also find us on Twitter and on Facebook.