As parents, it is easy to spend hours a day looking into your child’s eyes. After all, mutual gazing is one of the earliest forms of communication you can have with them. When looking into your child’s eyes, the eye color you see as a newborn or infant may not be the same eye color they end up with as a toddler.
But how do you know when – or if – those baby blue or gray eyes will turn into a different shade? We spoke with Emily M. Zepeda, MD, a clinical assistant professor and pediatric ophthalmologist at the Dean McGee Eye Institute/University of Oklahoma Department of Ophthalmology, to provide more information on what determines eye color and when your baby’s eyes will begin to change colors.
What Color Eyes Will my Baby Have?
In the distant past, no two individuals have the same exact eye color thanks to genetics.
Scientists believe as many as 16 genes help make up eye color, although two major genes – HERC2 and OCA2 – play the largest determining factor. Both of these genes are located on chromosome 15, one of the 23 pairs of chromosomes found in humans.
“Eye color is determined by an individual’s genetics; inherited genes which are the codes that influence the expression of traits such as our skin color, hair, and eye color,” Dr. Zepeda says. “Most of these codes related to eye color are linked to the production, transport, and storage of a pigment called melanin.”
This pigment is created by special cells called melanocytes. The pigment is stored in special vessels called melanosomes.
“Between humans, the relative number of melanocytes is similar; however, how much melanin is created, as well as the number of melanosomes, differs from person to person,” Dr. Zepeda says. “These differences give rise to the wide range of beautiful eye colors observed.”
How do Eyes Get Their Color?
To understand how eyes get their color, you must first understand the role of the iris – the muscle structure that surrounds the pupil (the black part of the eye) and controls how much light enters the eye. The iris has a back layer (known as the pigment epithelium) and a front layer (known as the stroma).
Most people have some brown in the pigment epithelium. However, the amount of pigment in the stroma is what determines your eye color.
“The iris holds many melanocytes which house all the melanin. Blue eyes contain minimal amounts of pigment while brown eyes have high melanin levels,” Dr. Zepeda says.
The more active the melanocytes are, the more melanin is produced. In other words, people with lighter color eyes (blue or green) do not have a different color pigment. They simply have less brown pigment than people with darker eyes.
Dr. Zepeda also explains how the amount of light reflected off the iris determines eye color. Lighter colored eyes have less or no melanin to absorb light, therefore more light is scattered across the color spectrum by collagen fibers to make eyes appear blue or green. Darker eyes have more melanin and absorb more light to make eyes appear brown.
This explains why some people’s eyes look a different color in a dark or light environment – blue eyes can look brighter outside but darker inside depending on how much light reflects off the iris.
Here is an overview of how pigment plays a role in the following eye colors:
- Brown: Both layers of the iris have more pigment, absorbing light to make the eyes appear brown. More than half of people have brown eyes.
- Blue/gray: The front layer of the iris has no pigment, allowing light to reflect off and give a blue appearance. About 25% of people have blue eyes.
- Green/hazel: Either the front or back layer – or both – have a low amount of pigment. Blue light reflects off the pigment to make the iris look green. About 18% of people have hazel eyes, while less than 10% of people have green eyes.
When Will My Baby’s Eyes Stop Changing Color?
A baby’s iris does not contain much melanin at birth. The lack of melanin allows light to reflect off the iris and make the eyes look blue (and sometimes gray), hence the name baby blue.
Over time, melanocytes continue to develop and produce melanin. Some children will keep their blue eyes, but many will experience a change before their toddler years. As more melanin develops, the eyes can darken to green, hazel, or brown.
Predicting when your child’s eyes will stop changing color can vary.
“The range of time when a baby will develop their ‘true’ eye color varies, but it usually happens between six and nine months of age,” Dr. Zepeda says.
Are All Babies Born With Blue Eyes?
Not all babies are born with blue eyes, though. White children tend to have blue or gray eyes at birth, while Asian, Black, and Hispanic children usually have darker eyes. This has to do with family history and from where certain groups of people originated. For example, Africa, South America, and Central America have sunnier/hotter climates than Europe. The body naturally boosts melanin production as a protective measure for people from these environments. Typically, the result is darker-colored eyes as well as darker skin.
If your child does have blue eyes, Dr. Zepeda exercises caution when exposing them to sunlight.
“Blue eyes have less pigmentation to absorb light in comparison to darker eyes that contain more melanin,” she says. “Because of this, blue eyes may be more sensitive to the effects of harsh lights such as fluorescent lights and sunlight. This is why parents should be vigilant to the lighting conditions for all newborns.”