Heterochromia means "different (hetero-) colors (-chromia)." Usually the term is used to describe the condition where a person has different colored eyes which is blue eye and one green eye, for example. Other terms to describe different colored eyes are heterochromia iridis and heterochromia iridium."Iridis" and "iridium" refer to the iris of the eye. The iris is the thin,circular structure that surrounds the pupil and contains the pigment melanin,which gives our eyes their distinctive color.

The amount of melanin in the iris determines whether we have blue eyes,green eyes,hazel eyes or brown eyes.Blue eyes have the least amount of melanin in the iris; brown eyes have the most. Heterochromia is usually benign.In other words,it is not an eye disease, and it does not affect visual acuity.

Benign heterochromia can give a person a captivating,even exotic,appearance.In fact, a number of celebrities-including Dan Aykroyd, Kate Bosworth, Henry Cavill, Alice Eve, Josh Henderson, Mila Kunis, Jane Seymour and Christopher Walken -have heterochromia.

Heterochromia also occurs in animals.Breeds of dogs that commonly exhibit heterochromia includes Siberian husky, Australian Shepherd, Border collie, Collie, Shetland sheepdog, Welsh corgi, Great Dane, dachshund and Chihuahua. Such cat breeds include Turkish Van, Turkish angora, Japanese bobtail, sphynx. Often such "odd-eyed cats" have been bred specifically to have this feature.