National Different Colored Eyes Day on July 12 is all about heterochromia iridum. It’s okay, we didn’t know what it meant at first, either. Heterochromia iridum is a term for the variation in color that gives a single organism two different colored eyes. It has been known to occur in populations of many species since the dawn of recorded history and is an interesting and sought-after trait. Only the lucky 1% of the population enjoys this special pigmentation, though there are three distinct types of heterochromia. Today, many people prefer pets with this fun eye color difference, and colored contact lenses are used just to mimic the trait! All this to say, give your friends with heterochromia a little extra love today.
History of National Different Colored Eyes Day
While today, people with two different-colored eyes are likely to get a compliment, that was far from the case through history. For example, Native American Indians used to believe that those born with the unique coloring could see both heaven and earth through their “ghost eyes.” Because they had seen dogs born with the trait, they found it inhuman and ghostly.
Many myths and fears have long been associated with heterochromia iridum, including superstitious beliefs that those with the trait were witches, were evil, could see beyond their own deaths and into the afterlife, or could consort with ghosts and spirits. Since eyes are the windows to the soul, ancient peoples who couldn’t explain the abnormality quickly resorted to ghostly explanations that painted the trait as making someone less-than-human.
Today, of course, our society finds it beautiful! However, it’s not widely understood. Did you know it can either appear at birth or be acquired? Especially if it’s acquired, it’s recommended to see a doctor just to ensure the condition is benign. While the vast majority of cases are completely harmless and simply pretty, some can indicate eye damage or that there is another underlying disease. Better safe than sorry!
There are actually three different kinds of heterochromia iridum – complete, segmental, and central. Central, the most common, appears as matching irises with different colors encircling the pupils. Many don’t know this classifies as heterochromia iridum! Segmental heterochromia appears as a different patch of color in only one iris, and complete heterochromia is the most iconic – two irises of different colors.
Whether genetic or not, the total percentage of the population with the trait is less than one half of one percent. If you want to know if there’s a chance it’s in your genes, comb through some old family photos! Keep in mind it can be very hard to discern – the majority of people actually don’t notice the condition in someone else, and it can be very easily mistaken.