Heterochromia means “different (hetero-) colors (-chromia).” Usually, the term is used to describe the condition in which a person has different colored eyes – one blue eye and one green eye, for example.

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

Usually, congenital heterochromia is a genetic trait that is inherited. Benign heterochromia also can occur as the result of a genetic mutation during embryonic development. In some cases, heterochromia is a symptom of another condition that’s present at birth or develops shortly thereafter.

One example of a condition that causes heterochromia is Horner’s syndrome. This is the combination of a constricted pupil, partial ptosis and loss of the ability to sweat on half of the face, all caused by an interruption of certain nerve impulses to the eye.

Heterochromia that develops later in life is called acquired heterochromia. Causes of acquired heterochromia include eye injuries, uveitis and certain glaucoma medications. Latisse, a repurposed glaucoma medication now used primarily as a cosmetic agent to thicken eyelashes, also can cause the iris to change color.

Though most cases of heterochromia are congenital and benign, if you or your child has different colored eyes (or different colored segments of one or both eyes), see your eye doctor for a comprehensive eye exam to rule out other causes. After your eye doctor confirms your eyes are healthy, enjoy the compliments you are likely to receive about the unique appearance of your two different colored eyes.

For more information about Merrimack Vision Care, call 424-0404 or visit merrimackvision.com.