What Is Heterochromia?

Learn about the causes of types of different-colored eyes

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Heterochromia is the term for when someone has two different-colored eyes. The difference may be complete or partial. For example, someone with blue eyes may have a patch of brown in just one eye. Or, someone may have one blue eye and one brown eye.

Someone may be born with heterochromia or have it develop later in life. It is very rare in humans, but it's often seen in animals like cats, horses, and dogs. A genetic condition, illness, or injury may be the reason behind it, and some causes can be serious.

This article discusses the types of heterochromia, possible causes, and how a healthcare provider will proceed if heterochromia is detected.

Man with heterochromia
WhitneyLewisPhotography / Getty Images 

Types and Symptoms of Heterochromia

The difference in eye colors is the only sign of heterochromia itself. Someone may, however, have other symptoms if their heterochromia stems from an underlying condition.

The extent of the difference in eye colors can differ. To reflect this, heterochromia is classified in different ways.

Cases can be distinguished by the amount of the iris (the colored part of your eye) that is involved:

  • Complete heterochromia (heterochromia iridis): One iris is a totally different color from the other. For example, the iris in one eye may be brown while the other is green.
  • Partial or segmented heterochromia: Part of one iris is different in color from the rest of that same iris.
  • Central heterochromia: A ring in one iris is a different color from the remaining parts of the same iris.

They can also be defined by the difference in the colors between the two eyes:

  • Hypochromic heterochromia: When the abnormal iris is of a lighter color than the normal one.
  • Hyperchromic heterochromia: When the abnormal iris is darker in color than the normal one.

What Causes Heterochromia?

The majority of cases of heterochromia are random. Most people born with heterochromia do not have any other health problems or symptoms. In rare cases, it is a symptom of another congenital (present from birth) disease.

It is also possible to develop heterochromia down the line due to a new, underlying condition, an eye injury or surgery, or even the use of certain medications.

If you’re born with heterochromia, or it manifests soon after your birth, it’s called congenital heterochromia.

Heterochromia that develops later in life is called acquired heterochromia.

Congenital Heterochromia

Some of the congenital diseases that can cause heterochromia include:

  • Horner’s syndrome: A rare condition that’s caused by damage to the nerves connecting the brain and eye. It usually affects just one side of the face and is characterized by droopy eyelids and permanently small pupils on that affected side.
  • Waardenburg syndrome: A group of genetic diseases that result in changes in the color of the eyes, skin, and hair. It also sometimes leads to hearing loss.
  • Piebaldism: A relatively harmless condition that’s characterized by a lack of pigment in the skin, eyes, and hair. People with this condition usually have portions of their hair, skin, and eyes that are lighter than normal.
  • Sturge-Weber syndrome: A condition where there are brain, skin, and eye abnormalities due to the abnormal development of certain blood vessels. People with this condition usually have a port-wine birthmark—a pinkish/reddish/purplish mark on their faces.
  • Parry-Romberg syndrome: In this condition, the skin, soft tissue, muscles, and sometimes bones on one side of the face slowly weaken and atrophy. It’s a very rare disease; people with it also suffer from seizures.
  • Hirschsprung disease: A condition that affects the large intestine. Mainly newborn babies and toddlers have this condition, and it makes them unable to pass stool easily and properly.
  • Tuberous sclerosis (Bourneville syndrome): A rare disease that involves the formation of noncancerous tumors in many different body organs such as the brain, heart, skin, kidneys, eyes, and lungs.
  • Duane syndrome: Also known as Duane retraction syndrome, people with this condition have difficulty moving one or both eyes inward and/or outward.

Acquired Heterochromia

Any of the following could cause heterochromia to develop in those who were not born with it:

  • Neuroblastoma: A form of cancer that starts in the nerve cells of the sympathetic nervous system. It affects mainly infants and younger children.
  • Fuchs' syndrome, also known as heterochromic cyclitis syndrome: Fuchs’ heterochromic iridocyclitis is an unusual form of chronic, low-grade anterior uveitis with variable clinical appearance. Typically the lighter-colored eye is the affected eye due to atrophy or loss of iris tissue. Symptoms can include on-and-off blurring and pain.
  • Glaucoma: This is a progressive disease where fluid builds up in the front part of your eye(s) and causes damage to the optic nerve there.
  • Central retinal vein occlusion: The blockage of the eye’s main retinal vein causes blood and other fluids to leak into the retina.
  • Melanoma of the eye: Also called ocular cancer, this is cancer that develops in the eye cells that produce melanin.
  • Eye injury or trauma
  • Certain types of eye drops
  • Eye surgery
  • Some of the drugs used to treat glaucoma
  • Diabetes

There are generally no risk factors associated with heterochromia, and it is also not an inherited disease. However, it is possible to have heterochromia because of inherited diseases like Waardenburg syndrome and piebaldism.

Diagnosis

Heterochromia is diagnosed by an ophthalmologist. They will examine your eyes to confirm that there is heterochromia present. Signs of underlying or causative diseases will also be looked out for.

If the ophthalmologist suspects that the heterochromia is a symptom of another disease, you will be referred to the particular healthcare provider trained to treat such disease for further diagnosis. Further investigation may involve blood tests, including genetic tests.

This typically is not necessary, however.

Does Heterochromia Need Treatment?

Typically, there’s no need to treat heterochromia if it isn't caused by another condition.

However, if you want both your eyes to have the same color, you may want to speak to your eye care professional about getting custom-made contact lenses to suit your particular kind of heterochromia.

If your heterochromia is as a result of any underlying disease or injury, treatment will be focused on the condition or injury. Given the array of potential causes, treatment possibilities vary widely.

A Word From Verywell

Having two different eye colors is often of no medical concern. You might even like that you have heterochromia and feel it makes you more unique.

Still, it's best to see a healthcare provider for an evaluation to make sure that there is no underlying cause that requires treatment. This is particularly important if you notice that you or your child's eyes have changed color all of a sudden.

Frequently Asked Questions

  • How rare is heterochromia?

    Heterochromia affects fewer than 200,000 people in the United States. It is much more common in animals.

  • Does heterochromia run in families?

    It may, but genetic heterochromia accounts for a very small percentage of cases. That said, heterochromia has been linked to a few rare genetic diseases, including Waardenburg syndrome, tuberous sclerosis, Bloch-Sulzberger syndrome, and piebaldism. 

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Rehman H. HeterochromiaCan Med Assoc J. 2008;179(5):447-448. doi:10.1503/cmaj.070497

Additional Reading

By Tolu Ajiboye
Tolu Ajiboye is a health writer who works with medical, wellness, biotech, and other healthcare technology companies.