The Intriguing Science Behind Blue Eyes

There is a very special set of physics at play here, and blue eyes obtain their color in the same way as the sky and water.

There is an intriguing set of physics behind blue eyes.
Tiplyashina Evgeniya / Shutterstock

There is a very special set of physics at play here, and blue eyes obtain their color in the same way as the sky and water.

If you think people have blue eyes because of pigmented cells, guess again. The truth behind why we have blue eyes is much more fascinating and complex and there is a very special set of physics at play here.

The iris is the area of your eyes which displays its color and there are two different layers of the iris which are known as the stroma and the epithelium. The stroma part of the iris is constructed of collagen fibers which technically have no color to them while the epithelium is the layer of your eye which allows colored specks to stand out and shine through.

The stroma itself may hold deposits of collagen and it can also hold melanin created by specific cells called melanocytes, and it is these two aspects of your eyes that determine its color.

If your eyes are brown, your body has achieved this because you hold a large amount of melanin in the stroma of your iris, which creates an absorbing effect upon the light making its way into your eyes. If you’ve got green eyes, you only have very small amounts of melanin in your stroma, but won’t have anything in the way of collagen deposits either.

What makes blue eyes so very special is that not only are they missing collagen deposits, but they also have absolutely no color at all in their stroma, nor is there any pigment to speak of.

The physics behind this means that when the light is captured by these eyes the light then gets tossed back out into the atmosphere, something known as Willis–Tyndall scattering, which is what gives them their blue look, according to Science Alert.

In other words, blue eyes aren’t technically really even blue, at least as defined by a solid and specific color. Their color is entirely dependent upon the light that is present at the time. This is something that is known as structural coloration, and it is also interestingly how butterflies get their coloring.

Blue eyes obtain their look and color just like the skies and water do, as the American Academy of Ophthalmology explain, which is why lovelorn writers who compare their beloved’s eyes to the bright blue skies and the emboldened, stormy seas are closer to the truth than they could probably ever imagine.