Many medical words come from Greek or Latin root words. For heterochromia, the source word is from Greek and it means iris or hair color. Additionally, “heteros” is known to mean different while “chroma” refers to color. When you take these words in conjunction, it refers to someone who has one iris that is lighter or darker than their other iris.
This condition is thought to effect just 11 people out of every thousand within the United States. While central heterochromia is the main type of the condition, there are actually two other forms as well. This medical condition is thought to be caused by variations in the levels of pigmentation or melanin. Some of the various reasons for occurring include eye injury or disease. In addition, genetic mosaicism or chimerism are thought to be two other possible reasons. Chimerism, if you are unfamiliar with it, is a condition where different parts of your body have different DNA. While your kidneys could have one set of DNA, your lungs or eyes could be from another.
There are three essential types of heterochromia. You could have central, complete or sectoral heterochromia. These tend to be classified based on how your eyes changed and if it is a genetic cause. Most cases in the United States are from genetics, but some can be due to another medical condition or an injury. Central heterochromia in particular is caused when the center of the iris looks gold and the outer iris is blue. This is known commonly as having cats eyes and looks like two different types of colors within the eye. The real eye color will always be on the outer rim of the iris.
Sectoral Heterochromia Appearance
In this second type of heterochromia, you will have two entirely different colors within the same iris. It may look like a spot or a patch of a different color, but it will not form an entire ring around the pupil.
The previous two types involved just partial eye color differences. In the last type of heterochromia, your irises will be entirely different colors. You may have one brown eye and one blue eye, or you could have one green eye and one blue eye. This condition manifests in both humans and animals, and it is exceedingly rare. Like the previous conditions, it could be caused by genetics or chimarism as well as some instances where it is caused by an environmental source.