Different colored irises are a fairly common occurrence in animals, but a rather rare disease in humans. Heterochromia iridis is a unique eye condition that affects the iris of the eye, where the two irises differ in color. For example, one eye could be blue while the other brown.
Actress Mila Kunis is one rare example of this condition. The colors of her irises are slightly different – one is more brownish green, while the other is blueish gray. Kunis’ eyes are indeed unique, but more unique than hers are people with irises that completely contrast in color.
Of course, no two eyes are identical, so it is perfectly normal to have a slight difference in coloration in each eye. Having two completely different colors in each eye however is a rare happening. Currently, it is not known how many people worldwide are affected by this condition, but it is estimated that less than one percent of the global population is affected.
What causes such a strange disease? Is it harmful? Does it affect how a person sees? Let’s unpack this phenomenon!
Melanin: The Cause
Our skin, hair and irises get their color from the pigment melanin. The darker the color of hair, skin and eyes, the more melanin a person has. The less melanin, the lighter someone’s skin, hair and eye color will be.
That is, for the most part. A person with dark hair will likely have brown eyes, while someone with lightly colored hair will have blue or green eyes. Sometimes someone with dark hair will have a light eye color and vice versa. This too is rare, but not as rare as having two different irises.
Sometimes our melanin distribution isn’t consistent. That’s how people end up with differing iris colors. One eye gets more melanin then the other, causing the melanin heavy eye to be darker than the other.
Most people are born with this condition. Having two differently colored irises is not hereditary, but genetics as well as non-genetic factors play a role in deciding a child’s eye color. Want to learn more about eye color? Read our article, Why Babies’ Eye Color Changes from Blue to Another Color.
If you’re born with heterochromia iridis, chance are the condition will not affect your health. The colors are purely aesthetic. One eye won’t be weaker than the other or be more susceptible to cataracts or any other vision condition. But sometimes, various other conditions that do require medical attention can cause heterochromia iridis.
A common symptom of melanoma, or skin cancer, is a discoloration in the eye. Brown flecks may begin to appear in the eyes to indicate that the melanin in the eye has become cancerous.
Eye trauma can also cause the color of your iris to change. A blow to the eye, for example, can cause the iris to lose some of its pigment and change color.
Glaucoma and glaucoma medication can also cause heterochromia iridis. It is not known for sure how glaucoma affects melanin levels, but it might have something to do with intraocular eye pressure. Glaucoma and the medication associated with it affect the eye’s fluid pressure which contributes to the color change.
Sometimes heterochromia iridis can come on suddenly. If this is the case, it may be hinting at an underlying heath problem. When this happens, you should check in with their general doctor and eye doctor to find the problem and begin treatment.
Types of Heterochromia Iridis
Generally, there are two types of this rare iris condition: complete heterochromia and segmental heterochromia.
Complete heterochromia refers to irises that are opposites of each other, like the image from before with one brown iris and one blue. This is the rarest type of heterochromia iridis.
Segmental heterochromia means that the same iris will have different colors. Kunis’ eyes, for instance, are segmental. Her iris has more than one color present. This is the more common form of heterochromia. This type of heterochromia can affect both or just one iris.
If your heterochromia iridis is caused by an underlying health condition, then whatever the treatment for that condition is will normally treat your irises too. However, in the case of eye injuries, the pigmentation is often permanent. It will persist even after the eye has healed from the injury.
If the heterochromia iridis is something that you’ve always had and was caused by a non-uniform distribution of melanin, then there isn’t really any treatment. Because the condition does not pose a threat to your eye health or overall health, there isn’t any reason to treat it.
However, this condition can make people feel uncomfortable and insecure about how their eyes look. Most people in this situation claim they wear decorative or colored contact lenses to make their eyes look like they’re the same color. However, colored or decorative contact lenses can be dangerous, especially if not used properly.
Living with the condition is what most people do. The pigmentation in the eye isn’t harmful to your eyesight and those with heterochromia have as good vision as anyone. However, many with the condition monitor the disease to make sure it isn’t indicating a more serious disease like cancer.
No eye is the same and that is certainly true when it comes to heterochromia iridis. The rare condition affects a small handful of Americans. It continues to be a source of awe for most.
There’s no reason to be ashamed of your eyes. All eyes are beautiful, no matter the color (or colors). Besides, next time a stranger asks you about your differently colored irises, you’ll be able to give them a thorough science lesson behind the condition.