One of the first things someone may notice about you is your eye color. But what if each eye is a different color? While this is a relatively rare condition — occuring in less than one percent of the population — it does happen, and it has a name: heterochromia. “It’s the word we use to describe when a person’s iris color doesn’t match,” explains Timothy McCulley, M.D., professor and chair of the Ruiz department of ophthalmology and visual science at McGovern Medical School at UTHealth Houston. While not common in humans, it occurs in dogs (particularly Dalmatians and Australian sheepdogs), cats and horses with surprising regularity.
Heterochromia takes three main forms, according to the American Academy of Ophthalmology:
- Complete heterochromia: One iris — the colored tissue at the front of the eye — is a different color from the other.
- Partial heterochromia: Part of one iris is a different color from the rest of it.
- Central heterochromia. This is when the inner ring of the iris is a different color from the outer ring.
Certain famous celebrities, such as Mila Kunis, Kate Bosworth and Kiefer Sutherland, reportedly have heterochromia. Although some speculated that musician David Bowie had different colored eyes, in fact it appears that he had another condition, called anisocoria, due to an injury that made his pupils different sizes, McCulley says.
What causes heterochromia?
Much of the time, this condition boils down to genetics. But it can be due to an injury or an underlying medical problem. Here’s what you need to know.
Some cases of heterochromia, known as congenital heterochromia, cause different colored eyes as the result of a benign genetic mutation that affects the development of melanin, or pigment, in the irises. In such a case, you’re born with different colored eyes, but it doesn’t affect your overall health, including your eye health. Other times, different eye colors at birth are a symptom of another, more serious health condition, notes Douglas Lazzaro, M.D., an ophthalmologist at NYU Langone Health in New York City.
These can include:
- Horner’s syndrome. This is a condition where a nerve pathway from your brain to your head and neck is disrupted. “One of the pupils tends to be smaller, and looks lighter than the other one,” says Richard Rosen, M.D., chief of retinal services at the New York Eye and Ear Infirmary of Mount Sinai in New York City. You can be born with Horner’s or acquire it later in life.
- Waardenburg syndrome. This genetic condition passed down through families causes deafness, pale skin and eyes, and sometimes different colored eyes.
- Sturge-Weber syndrome. This is a rare blood vessel disease that can cause facial birthmarks, abnormal brain blood vessels and even glaucoma.
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Some people can develop heterochromia as an adult, thanks to an undiagnosed medical condition or even certain medications. Here are six reasons people can develop different colored eyes.
- Glaucoma. If you have glaucoma, some of the medications used to treat it — such as the eye drop latanoprost — can cause the iris of your treated eye to slowly become browner in color, notes Rosen. This is more likely to happen if you have blue-brown, gray-brown, green-brown, or yellow-brown eyes. The eyelash-enhancing drug Latisse, a repurposed glaucoma medicine, can also cause these changes.
- Eye trauma or swelling. If you’ve been hit in the eye, you may notice a temporary change in color due to scarring of the cornea, says Rosen. This can also happen if you have uveitis, a swelling of the middle layer of your eyeball, either from infection or an inflammatory disease such as rheumatoid arthritis or lupus.
- Fuchs heterochromic iridocyclitis. Remember the villain Le Chiffre in the James Bond movie Casino Royale who was always weeping bloody tears? Turns out he suffered from this condition, a form of chronic uveitis, notes Rosen. It’s not uncommon for people with this condition to have one eye that looks lighter than the other, he adds, due to an enlarged pupil and murky cornea.
- Pigment dispersion syndrome. In this condition, the back of the iris rubs against your eye’s lens, causing iris pigment to come off, says Lazzaro. “This causes a defect in the iris color, which makes it appear lighter over time,” he explains. Left untreated, it can potentially lead to glaucoma.
- Eye tumors. These can appear like freckles on your eye, making part of the iris appear a different color, says Lazzaro. Sometimes they are benign, but they can signify a potentially deadly condition, such as ocular melanoma.
- Diabetic eye disease. Untreated end-stage diabetes can cause the part of the iris around your pupil to darken, creating the illusion of a change in eye color, says Lazzaro.
Should you see a doctor if your eyes are different colors?
If you were born this way, it’s probably not something that you need to race to your eye doctor about. But if as an adult you notice heterochromatic eyes, you should see an eye specialist as soon as possible to rule out a potentially serious, even sight-stealing condition, Lazzaro says. A complete eye exam can reveal the cause, and help you get appropriate treatment.
Hallie Levine is a contributing writer and an award-winning medical and health reporter. Her work has appeared in The New York Times, Consumer Reports, Real Simple, Health and Time, among other publications.