My grandma's cat Miciò, photo by Ilaria Cannava My grandma’s cat Miciò, photo by Ilaria Cannava

Heterochromia iridum is a difference in coloration of the eyes; it is caused by a congenital or acquired uneven distribution of melanin, the pigment that determines not only the color of the eyes but also the one of hair and skin – quite a huge responsability.

David Bowie’s profusely photographed blue right eye & green/brown left eye contributed quite a lot to bring the phenomenon to common knowledge. In his case we talk about acquired heterochromia, and more precisely about a punch in the face at the age of about 15. Bowie also presents a permanent dilated pupil, a condition known as anisocoria. Actually, one must be cautious when it is about David Bowie. Some of you – especially the ones who have read Lester Bangs – may have heard that Bowie has a tendency to get credited for things that are not, in fact, that unique or special as they may seem.

Heterochromia is quite uncommon in humans, but relatively frequent in animals, for example in certain breeds of cats such as the Turkish Van. Their blue eye corresponds to a spot where melanin is absent. Here above you see an example of stunningly beauty.