Example of complete heterochromia.
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Introduction
Hello, my name is Derek Kisic. I am a student at Mount Aloysius College in PA, and it is my 3rd year of college. The reason that I have taken an interest in heterochromia is because back in the early years of high school, I had an art teacher who had sectorial heterochromia (explained later on in the article) and he suspected that he had Waardenburg syndrome but was never diagnosed with it. In my own curiosity, I found that a rare symptom of it was discoloration in the eyes. While he left for new horizons not long after, I still was curious about the subject.
Has there been a time during elementary school when classmates would show off the colors of their eyes? Well, people who have heterochromia would win a competition for "most unique eye colors." Harmless and not life-threatening, heterochromia is the discoloration of the eyes, making it so that one eye color is different from the other eye. This is known as complete heterochromia, one of three different types of eye discoloration. The other two are sectorial heterochromia - a small section of one eye is a different color than the main parts of the iris on both eyes - and central heterochromia - the central part of the iris that is closest to the pupil being a different color than the rest of the eyes. However, going back to the "not life-threatening" thing, could it be that having different eye colors might possibly be a sign of something dangerous?
Eye color is determined by melanin concentration and distribution. This is caused by melanocytes, which are special cells that produce and disperse melanin. If these cells were to be damaged in any way on their way to the eye, they could have reduced production of melanin, meaning that the color would be different between the two eyes. This can be done through chemicals in certain medications taken over long periods of time such as certain glaucoma medication. This prevents the melanocytes from completing their journey and ultimately lead to them getting "held up" and make them incapable of completing the trip to the iris. This means that the irises will have an imbalance in melanin and create the heterochromatic eyes.
Another way that this can occur is under injuries to the eye, or physical trauma against the melanocytes that lead to them incorrectly distributing the melanin content and changing the eye color. Even rarer is an infant being born with it naturally, such as in the case with chimeras, as they have two different DNA sequences that can be at odds with one another, leading to the unique eye color. More commonly the cause is from genetic diseases like Waardenburg syndrome, Sturge-Weber syndrome, Romberg hemifacial atrophy/Parry-Romberg syndrome, and Horner's syndrome.
Waardenburg syndrome has symptoms based around the loss of hearing, along with it affecting the coloration of the skin, hair, and eyes (among other symptoms, such as abnormal shape of the face). This is a genetic disease that is caused by mutations in at least 6 different genes according to the Genetic and Rare Diseases Information Center. Sturge-Weber syndrome afflicts people who have it by causing unusual growth in blood vessels in the tissue of the brain covering and spinal cord that can lead to a multitude of problems, seizures and strokes being the most serious of the symptoms. They also have what is known as port-wine stains as birthmarks that cover their face, and they can develop glaucoma.
Parry-Romberg syndrome is another condition which may have heterochromia as a symptom. While the cause isn't understood so far, it causes the tissues on one side of the face to atrophy and cause permanent disfiguration. Seizures and pain in the nerves of the face are also symptoms of this condition, and changes to the eye, like sunken eyes and discoloration of the sclera and iris of the eye are also possible symptoms. Horner's syndrome has symptoms that include drooping eyelids and an inability to sweat from the pores on the face. If the condition is present at birth, it may also lead to discoloration and reduced amounts of melanin in the eye, causing heterochromia. There are more conditions as well that may cause heterochromia, and most have dangerous and detrimental symptoms as well.
Heterochromia, while interesting and unique to look at, is more than just having discoloration in the eyes or an interesting eye color to see. It could be from rather serious genetic disorders as well as physical trauma that had made this type of eyes the way they are. They are eyes that represent hardship of some kind, whether that be physical or genetic.
Infographic containing information about heterochromia.
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