This condition is relatively rare in humans. However, heterochromia appears quite commonly in dogs (such as Dalmatians and Australian sheep dogs), cats, and horses.

Heterochromia in humans can be hereditary, caused by a disease or syndrome, or due to an injury. Rock star David Bowie has heterochromia, reportedly due to an eye injury.

Specific causes include:

• Familial heterochromia (autosomal dominant transmission)
• Waardenberg syndrome (congenital and autosomal dominant)
• Neuroblastoma (as a result of cervical sympathetic nerve compression)
• Neurofibromatosis (may cause the affected iris to darken)
• Injury, hemorrhage, glaucoma, or foreign body in the eye

If you notice new changes in the color of one eye or that your infant has two differently colored eyes, consult your health care provider to be sure this isn't a symptom of a medical problem.

A complete eye exam conducted by an ophthalmologist (eye doctor) is also recommended. Some conditions and syndromes associated with heterochromia, such as pigmentary glaucoma, can only be detected by a thorough ophthalmic exam.

The following questions may help evaluate the cause:

• Were the two differently colored eyes noticed when the child was born, shortly after the birth, or recently?
• Are any other symptoms present?

An infant with heterochromia should be examined for other problems.

A complete eye examination can rule out most causes of heterochromia. If there doesn't seem to be an underlying disorder, no further testing may be necessary. If another disorder is suspected, diagnostic tests may be performed to confirm the diagnosis. This may include various blood tests, chromosome studies, or others.