Out of all the possible quirks to be born with, two-tone eyes might be among the most striking. The phenomenon is known as heterochromia iridum, and it comes with a long list of variations and possible causes.
It’s also fairly uncommon – only around one in a hundred Americans have the condition. Those that do obviously have a pair of peepers that could draw a second look from just about anybody, but is that all?
If you have or know someone who has heterochromatic eyes, you might find yourself wondering if there are any downsides or worries that come along with the territory. We’ll try and answer your questions in this article, and give you a little more information as we do.
Born This Way
There can be many, many causes of heterochromia iridum, which can be broadly broken down into two categories: congenital and acquired. Congenital heterochromia is genetic in origin, and people with the condition are born with it. This can sometimes be a result of simple genetic inheritance, which doesn’t come along with any complications. However, it can also result from a long list of other causes.
Heterochromia can, unfortunately, be an early sign of a genetic disorder. Waardenburg Syndrome, a relatively rare, heritable disorder, is one example. People living with Waardenburg Syndrome can have a wide range of symptoms, with hearing loss being perhaps the most severe.
Heterochromia – or characteristic pale blue eyes – is a common red flag for the disorder. Ocular melanosis, which can put sufferers at increased risk for glaucoma, can also influence eye pigmentation.
Bottom line: congenital heterochromia iridum isn’t necessarily cause for panic, but it absolutely should put you on the watch for a few more serious symptoms.
A couple of more benign, but equally interesting causes, are mosaicism and chimerism. They might sound a little imposing, but believe it or not, they’re fairly simple. Both are ways for children to pick up heterochromia without directly inheriting genetic traits that cause it.
If you know a bit of genetics, then you’re probably used to the idea that every cell in a single human’s body has the same DNA. But it turns out that’s not entirely true – a good number of us (if not all) are actually genetic mosaics, and have a certain percentage of cells with different DNA.
Mosaicism occurs in the early stages of human development, when one cell picks up a mutation that alters its DNA, a change that it then passes on to all other cells it produces. In some cases, that mutation can produce two eyes with different genetic roots, which can in turn cause heterochromia.
Chimeras also have a couple different types of DNA bouncing around, but they get them from a different source. Fraternal twins in the earliest stages of development can actually fuse together, creating a single individual with two genetic sources. As those two sources can be as diverse as any two siblings (read: pretty darn different), heterochromia is well within the realm of possibilities.
Just Something I Picked Up
So that’s congenital heterochromia, let’s talk about the acquired version. There’s a long list of ways to wind up heterochromic as an adult. Sadly, an awful lot of them aren’t what you’d call desirable.
Blunt or penetrating injury to an eye can change its color, as damaged blood vessels can leak into the eye. Tumors can also affect eye color. Many are benign, and some can even show up as nevi (birthmarks). However, other, more worrying ones can pop up – it doesn’t happen often, but cancerous growths can also cause heterochromia.
There are several other possible causes, but any unexpected eye changes should be cause for alarm. If you wake up with an eye inexplicably several shades lighter, it’s time to call for help.
Sometimes though, heterochromia is no more than a fashion choice. Colored contacts have been around for some time now, and as heterochromatic eyes can be nothing short of stunning, some folks might deck their orbs out in different colors.
And it’s possible to go a step further. While you won’t see them in the US, decorative eye implants do exist, and can semi-permanently give you just about any eye color you’d like. Both options do carry some risks. Decorative contacts are still medical devices, and wearing them puts you at the same risk of infection and eye damage as any contact wearer.
Surgery, at this stage, is even more of a gamble. Clinics willing to perform the procedure are often overseas, and require extra vetting to be sure of a safe surgery.
Of course, for some people, it’s worth it. After all, there’s a long list of celebrities to imitate…
Heterochromic and High-Profile
Any of you out there with heterochromia have some star-studded brethren. There’s no denying that heterochromic eyes have a certain allure, and you’ll often see them on actors. Mila Kunis, Benedict Cumberbatch, Kate Bosworth, Robert Downey Jr., and Christopher Walken all have heterochromia to greater or lesser extents. And if you like your celebrities a little more historical, well, add Alexander the Great to the list.
So that’s heterochromia. If you or a loved one happens to be heterochromic, you may find yourself wondering if there’s anything you should be worried about moving forward. The answer: sometimes yes, and sometimes no.
The main takeaway you should have regarding health is that heterochromia can be a symptom of more serious symptoms, especially if acquired later in life. For this reason, you should absolutely have your differently-colored eyes checked for other problems. That goes double if you notice any sudden changes to eye color, as this almost always means that there’s something nasty afoot.
But don’t despair. First off, plenty of the conditions that can cause heterochromia are treatable, and the ones that aren’t can generally be kept to a minimum with proper medical attention. Second, heterochromia is often benign, only really showing itself in a pair of very pretty eyes.
If that’s the case, then the only things you have to worry about are the same vision problems everyone has to deal with. Eat well, take eye vitamins, research healthy eye habits, and you ought to be just fine.