Eye color is often the genetic trait that fascinates parents the most. Parents frequently ask our doctors here at Heritage Eye, Skin & Laser Center if they can tell what color eyes their baby will have. Will our child’s eyes be black, brown, blue, gray, green, hazel or some combination of colors?
A child’s physical characteristics depend on the genetic material each parent contributes to the child. The influences from each parent aren’t known until — surprise — after the child is born!
In years past, simple charts were used that supposedly could predict the eye color of children based on the eye color of their parents. We now realize that the way eye color is inherited is far more complicated than originally thought. Generally, though, it’s far more likely for two brown-eyed parents to have a blue-eyed child than for two blue-eyed parents to have a brown-eyed child. This is because the generally less dominant blue-eyed trait can be passed along by brown-eyed people until the genes for the lighter eye color happen to match up, possibly many generations later.
Two blue-eyed parents, on the other hand, are much less likely to have darker-eyed children. This is because darker eyes generally are so much more dominant that the genetic trait, when present, ordinarily would first show up in the parent, who then wouldn’t be blue-eyed at all.
Still, due to the complexities of how genetic traits are passed along, it is entirely possible for two blue-eyed parents to have a brown-eyed child.
How Eye Color Develops
The colored part of the eye is called the iris, which has pigmentation that determines our eye color. Human eye color originates with three genes, two of which are well understood. These genes account for the most common colors — green, brown, and blue. Other colors, such as gray, hazel and multiple combinations are not fully understood or explainable at this time.
Most babies are born with blue eyes but they may be blue only temporarily. Oftentimes, a babies’ eye color will darken in the first three years. Darkening occurs if melanin, a brown pigment usually not present at birth, develops with age.
We used to think of brown being “dominant” and blue being “recessive.” But modern science has shown that eye color is not at all that simple. Also, eye colors don’t come out as a blend of the parents’ colors, as in mixing paint. Each parent has two pairs of genes on each chromosome. So multiple possibilities exist, depending on how the “Wheel of Fortune” spins.
Children can have completely different eye colors than either of their parents. But if both parents have brown eyes, it’s most likely that their children will also have brown eyes. The darker colors tend to dominate, so brown tends to win out over green, and green tends to win out over blue. However, a brown/blue parent mix doesn’t automatically produce a brown-eyed child.
Some children are born with irises that don’t match in color. Usually this is caused by faulty developmental pigment transport, local trauma either in the womb or shortly after birth, or a benign genetic disorder. Other causes can be inflammation, freckle (diffuse nevus) of the iris and Horner’s Syndrome. Having an early eye exam is important to make sure nothing serious is going on — and “nothing serious” is the most common finding.
Why Does the Color of My Eyes Change?
The iris is a muscle that expands and contracts to control pupil size. The pupil enlarges in dimmer lighting and grows smaller in brighter lighting. The pupil also shrinks when you focus on near objects, such as a book you are reading.
When the pupil size changes, the pigments in the iris compress or spread apart, changing the eye color a bit. In addition, certain emotions can change both the pupil size and the iris color. That’s why some people say their eyes change colors when they’re angry or loving. Eye color also can change as we age, this happens in 10 to 15 percent of the Caucasian population, and can actually get darker with age.
When To Call Your Your Doctor
If your adult eye color changes dramatically, or if one eye changes from brown to green or blue to brown, called heterochromia, it’s important to see your eye doctor. Eye color changes can be a warning sign of certain diseases, such as Fuch’s heterochromic iridocyclitis, Horner’s syndrome or pigmentary glaucoma.
Can I Change My Eye Color?
Ultimately, if you don’t like the eye color you inherited, you can always change it with colored contact lenses. But remember, even colored contact lenses are a prescription medical device and must be prescribed and monitored by an eye doctor. Don’t buy your contact lenses over the Internet or get them from a friend without having an eye doctor’s prescription.
From the Staff of Heritage Eye, Skin & Laser Center…
Here’s Looking At You!
