Heterochromia: Causes And Types
Have you ever seen someone with eyes that are two different colors?
This fascinating trait is called heterochromia, and only six people in a thousand have it. It can happen in different ways and for different reasons. Even if you haven’t seen someone with different colored eyes, you’ve likely seen an odd-eyed dog or a cat. But how does such a strange-looking thing happen?
What Causes Heterochromia
Most of the time, heterochromia is simply congenital (meaning the result of genetics) and caused by a benign mutation affecting the way melanin (pigment) develops in the irises. A few famous examples of congenital heterochromia are Mila Kunis, Jane Seymour, Simon Pegg, and Anthony Stewart Head.
People who weren’t born with heterochromia might still develop it, as it can also be caused by trauma (due to injury or surgery) or disease (such as diabetes, eye tumors, or glaucoma). Acquired heterochromia might look as interesting as congenital heterochromia, but it often indicates the eye is damaged or unhealthy. The most famous example of it is David Bowie, whose left iris remained permanently dilated after an injury, giving him the appearance of having different colored eyes.
Types Of Heterochromia
Just as heterochromia can be the result of a variety of causes, it can also produce a wide range of results. The three categories are complete, segmental, and central heterochromia. Complete heterochromia, also called heterochromia iridum, occurs when the two irises are different colors. Segmental heterochromia, also called heterochromia iridis, occurs when a patch of a different color appears in one iris.
Central heterochromia is more common than the other types, but not nearly as visually striking. It happens when the irises match each other but have a ring of a different color around the pupils. For instance, someone with blue eyes might have a thin ring of hazel or brown around their pupils.
Heterochromia In Folklore
In our culture, heterochromia is merely an intriguing anomaly, but that hasn’t been the case for everyone. Some Native American cultures believe having heterochromia means the person can see into heaven and earth at the same time through different colored eyes. They refer to this as having “Ghost Eyes.” Halfway around the world, Eastern European pagans believe being born with heterochromia means the person has witch eyes!