One of the many fascinating variations that exist among humans (and other animals) is heterochromia iridis, or heterochromia iridum – terms used to describe different colored eyes in the same person. Caused by an excess or lack of melanin, heterochromia can occur as a result of genetics, disease or injury. Yet, whatever its underlying cause, heterochromia is almost always eye-catching!
There are three types of heterochromia of the eye: complete, sectoral and central. Complete is when both eyes are of different colors – for example, a brown eye and a blue eye – and is perhaps the most striking and widely-known of the three.
Sectoral heterochromia occurs when there are two different colors in the same iris – a splash of a second color that’s different from the dominant hue.
Central heterochromia is when the iris itself has two or more complete sets of color – for example, blue with a gold ring closer to the pupil or a purplish ring around the outside.
People with central heterochromia are sometimes said to have ‘cat eyes’, but all forms of heterochromia are unique to the individual and are fascinating to see.
Interestingly, there are only three pigment colors that make up the appearance of the iris: blue, brown and yellow. The varying amounts of each determine one’s final eye color – although heterochromia is something different: as suggested, it’s an unusually light or dark coloration of all or part of one eye.
Heterochromia is relatively rare – it affects around 11 in every 1,000 people in America – but it can develop over time. It can be inherited from one’s parents and come about as a result of various conditions – both genetic and acquired. In spite of this, it is not necessarily a sign of underlying health issues.
Heterochromia may be uncommon but many celebrities have it, among them Kate Bosworth, Jane Seymour, Mila Kunis, and Michael Flatley. Perhaps the dissimilarity helps such famous faces to stand out in a crowd.