What Causes Differently Colored Eyes?

Have you ever seen someone with differently colored eyes or eyes that have more than one color? For instance, do you know someone with blue eyes flecked with brown? The condition is called heterochromia iridis, and it affects the iris, the colored part of your eye.

Most of the time, it doesn't cause any problems. It's often just a color quirk that's caused by genes inherited from parents or by a problem that happened when the eyes were being formed. In rare cases, though, it can be a symptom of something else. It could be a health problem or a condition a person was born with.

It's common in some animals but rare in humans. It affects fewer than 200,000 people in the United States.

A Closer Look at Eye Color

Your iris gets its color from a pigment called melanin. It's what makes them blue, green, brown, or hazel. Less melanin leads to lighter eye color. More melanin leads to darker eyes.

Sometimes, the amount of pigment in your eyes can vary:

  • Complete heterochromia means one iris is a different color than the other. For example, you may have one blue eye and one brown eye.
  • Segmental heterochromia means different parts of one iris are different colors.

Common Causes

If your eye color changes after you're an infant, it's called acquired heterochromia. Talk with your eye doctor or regular doctor if this happens to make sure a disease isn't causing it.

Some things that can cause heterochromia include:

  • Eye trauma -- from being hit in the eye, for instance -- is one reason your eye might change color. More than 80% of eye injuries are caused by projects around the house, sports, or other recreational activities.
  • Glaucoma, which affects more than 3 million Americans, is another possible cause. It's an eye disease that leads to increased pressure in your eyes from fluid buildup. It can cause vision loss, but early detection and treatment can help prevent that.
  • Certain medicines, including some glaucoma drugs that lower pressure in your eye, may cause changes in eye color.
  • Neuroblastoma is a cancer of the nerve cells that usually affects children under 10. When tumors press on nerves in the chest or neck, sometimes kids have a drooping eyelid and a small pupil. They can also get heterochromia. See a doctor right away if your child's eye color changes.
  • Eye cancer: Melanoma can affect the eye in rare cases. It happens in melanin -- the pigment that gives your eyes (and hair and skin) their color. One sign of eye melanoma is a dark spot on the iris. But blurry vision or sudden vision loss are also common.

 

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Heterochromia in Infants

If you have a baby with different colored eyes, talk to your pediatrician. You may also need to make an appointment with an eye doctor (an ophthalmologist).

Your baby probably won't have any other eye (or health) problems. But it can be linked to a disorder caused by a problem gene. Some of these include:

  • Waardenburg syndrome: This is a group of genetic conditions that can cause hearing loss and changes in hair, skin, and eye color.
  • Sturge-Weber syndrome: A key sign is a large purplish birthmark on the face caused by problems with some blood vessel. Seizures are a common sign, but heterochromia iridis also can happen.
  • Parry-Romberg syndrome: Also known as progressive hemifacial atrophy, this is a rare condition that makes one side of your face sunken and wrinkled.
  • Horner's syndrome: This is a rare disorder caused by problems with certain facial nerves. Signs of it can include heterochromia, different sized pupils, and a drooping eyelid.

 

WebMD Medical Reference Reviewed by William Blahd, MD on December 23, 2016

Sources

SOURCES:

CMAJ/JMAC Canadian Medical Association Journal: "Heterochromia."

National Institutes of Health, Genetic and Rare Diseases Center: "Heterochromia iridis," "Waardenburg syndrome," "Sturge-Weber Syndrome," "Progressive hemifacial atrophy," "Horner's Syndrome."

National Institutes of Health, Genetics Home Reference: "Is eye color determined by genetics?"

American Academy of Opthalmology: "Preventing Eye Injuries," "What is Ocular Melanoma?" "Heterochromia."   

"American Cancer Society: "Neuroblastoma," "Melanoma Skin Cancer."

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