Dr. Michelle Calder-Cardwell is the owner and lead optometrist at
Urban Optiques Vision & Eyewear in Northville, MI.
Q. My sister has green eyes and I have blue, but our parents have brown and blue. Besides genetics, can you explain the mystery of what gives our eyes their color?
A. It sounds like you already know that genetics determines the color of our eyes, so I won't bore you with a complicated science lesson. Instead, I'll focus on explaining the mystery behind eye color.
In a nutshell, the color of your eyes depends on how much of the pigment melanin you have in your iris—the colored part of your eyes. The more pigment you have, the darker your eyes will be. Blue, grey, and green eyes are lighter because they have less melanin in the iris.
Besides giving our eyes color, melanin helps protect them from the sun. Because they have less pigment, light eyes are much more sensitive to the sun's harmful rays than brown or black eyes.
Disease, trauma, and aging can lead to changes in eye color. In fact, our eyes begin changing from the time we're born. Newborn babies don't have melanin in their eyes, so they begin life with blue or almost colorless eyes. The melanin gradually increases, and by about three years of age, their eyes will have darkened to their true color.
Most people in the world will end up with brown eyes. The second most common colors are blue and grey, and green is the rarest color.
On a side note, it's interesting that eye color has been the source of superstition through the years. The mystically-inclined believe the eyes are the windows to the soul and eye color shows a person's talents. Some personality traits attributed to eye color are: