Why Do Some People Have Two Different Colored Eyes?


Heterochromia is a Greek word meaning color difference. A person with two differently colored eyes is said to have complete heterochromia. Usually this has simply been passed on genetically and the heterochromia is an inherited trait. Babies are usually born with both eyes being the same color and the heterochromia (if it’s going to happen) will show up within a month or two.

Blue and green eye pigment doesn’t exist!

You may be surprised to find out that pigmentation of the human iris (that’s the colored part of the eye) ranges from a very light brown to a much darker black/brown. The lighter shades of eye color that appear to be blue, green or hazel are simply caused by the way light travels through the light brown pigment in the eye. This optical phenomenon, known as Raleigh scattering, also explains the blue appearance of our sky above. Rayleigh scattering of sunlight in the atmosphere causes diffuse sky radiation, which is the reason for the blue color of the sky and the yellow tone of the sun itself.

Eye color is the result of how much pigment is made in the front part of the eye. Little or no pigment gives blue eyes, some pigment results in green, and lots of pigment gives brown eyes. The amount of pigment is determined by at least two genes in special cells called melanocytes.

A common form of heterochromia is one blue eye and one different colored eye. One way to end up with a blue eye is if part of one eye is missing melanocytes. Another way is if an eye color gene only “works” in one eye.

Different types of heterochromia

There are different types of heterochromia:

  • Complete Heterochromia means having two completely differently colored eyes
  • Partial Heterochromia means most of the iris might be blue or green with only a small section or spot of a different color being present
  • Central Heterochromia describes an eye that has one color right around the central pupil area and a different color throughout the rest of the iris.

Some medical conditions are associated with heterochromia

Very occasionally, heterochromia can indicate a more serious underlying medical condition so you might want to shop for ophthalmologists (eye doctors) that specialize in the diagnosis and treatment of diseases of the eyes. While genetics are by far the most common reason for specific eye colorations, injury to the eye or disease can herald the onset of heterochromia. An ophthalmologist will have the eye instruments required for viewing the interior of your eye. They are in constant contact with companies, such as, Rumex International, that specialize in the manufacture of eye instruments and will be properly equipped to diagnose and treat any injuries responsible for eye color changes. Unfortunately reversing eye color change once it has occurred is not always possible.

If you notice that there are new changes in the color of your eye, or if your child begins developing two different colored eyes, it doesn’t hurt to undergo a thorough eye examination. This exam can rule out most causes of heterochromia to ensure that there is no underlying disorder that may be causes the difference. However, if this test comes back clear, no further testing may be necessary.

My name is Liza McFlow. I am a student of Medical Department. I make my first steps in the world of Blogs. I would like to try myself as a writer of interesting articles about ophthalmology, eyes health, optometry.

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