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What You Need to Know About the Iris and Its Color

May 22, 2015

Eye color is one of our most basic traits. It’s listed on several documents, right next to height, age, gender, and other important factors. But what makes our eyes the color they are is anything but basic. In fact, the iris is quite complex.

What determines our eye color?

There are several genetic factors that determine what eye color you’ll be born with. It used to be thought that brown eyes, for example, were a dominant trait, and that blue eyes were recessive. Genetic scientists are still researching what goes in to what makes our eye a certain color in relation to genes, but there’s another thing that contributes to eye color that we don’t even think about.

Melanin Affects my Eye Color?

When we think of the word “melanin,” we often think of skin tone. Those with paler skin such as caucasians, have less melanin, while African Americans for example, have much more. Did you know that the amount of melanin we have also determines the color of our eyes?

When a baby is born, it doesn’t have melanin yet and so most babies appear not to have an eye color at all, but by one year of age, all babies have an eye color. The more melanin you have, the darker your eyes will be; the less melanin you have, the lighter your eyes will be. Thus, people with dark brown eyes have a high level of melanin while people with blue eyes have a far lower level.

Changes of the Iris

Many people are not always happy with their eye color. Just like some people prefer to curl their straight hair, or straighten their curly hair, many people desire to change their eye color. Scientists in some parts of the world, such as Mexico and Costa Rica, are performing clinical trials in which they are changing the color of patients’ irises. (This procedure is not currently legal in the United States.)

However, there are many people who experience a change in eye color without choosing to do so. Many factors can contribute to eye color change.

Infancy and Aging

We mentioned above that when born, because of the lack of melanin, many babies do not have an eye color until they are a bit older. By one year of age they have an eye color. Babies though, are not the only people affected. Those on the other side of the age spectrum—the elderly—may also experience change in eye color. As we age there is the possibility of a slight change of eye color. However, this change is not drastic.


When people experience a trauma of some kind, it has been noted in many cases to affect the color of their iris. In some cases the trauma affects the size of the pupil and in that case, how the iris’ color is perceived. David Bowie is a classic example of someone who experienced this.


Women who are pregnant can possibly experience change in color of the iris. This is related to changes in pigmentation and typically, if a change occurs, it is slight.


Unfortunately there are many diseases that cause the iris to change colors. Some of the better known diseases to do this are pigmentary glaucoma, a disease you can catch early on, and Horner’s Syndrome.

Another disease which we’ve been hearing a lot about in the news, which people are unaware affects the eye is Ebola. Ebola can cause differences in pigmentation that are often permanent, though one patient was recently lucky enough to survive Ebola and the pigmentation change was temporary. In many cases Ebola may even lead to blindness.

Have more questions? 

If you have more questions about what may cause color change of your iris or any other changes to your eye or eyesight, please feel free to reach out. We’re happy to help you schedule a consultation and answer all of your questions today!

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