Eye color: how it develops and why it changes
Assist. Assoc. Dr. Edited by İbrahim ŞAHBAZ.
Often times, eye color is the genetic trait that fascinates parents most in child development. Will the child’s eyes be black, brown, blue, gray, green, hazel, or a combination of these colors?
What a child looks like depends on the genetic material each parent contributes to the child. But parents’ genes can mix and match in many different ways. The effects of each parent are not known until the child is born.
How does eye color develop?
The colored part of the eye is called the iris, and the iris has the pigmentation that determines our eye color.
The color of the human eye is due to three genes, two of which are well understood. These genes determine the most common colors (green, brown, and blue). Other colors such as gray, hazel and multiple combinations are not fully understood or explained at this time.
At one time, brown eye color was considered “dominant”, while blue eye color was considered “recessive”. But modern science has shown that eye color is not so simple.
Eye color is not just a mixture of the eye colors of the parents, as in mixing paints. Each parent has two pairs of genes on each chromosome, and there are many possibilities for how this genetic information is expressed as eye color.
And early in life, eye color can change.
Most non-Hispanic White babies are born with blue eyes, and their eyes turn darker during their first three years of life. The color of the eyes becomes darker as melanin, a brown pigment that is not usually present at birth, develops with age.
Children can have completely different eye colors than either of their parents. However, if both parents have brown eyes, their child will most likely have brown eyes as well.
Darker colors tend to dominate; therefore, brown tends to dominate the color green, and green over the color blue.
However, the scenario of a brown-eyed parent and a blue-eyed parent does not automatically produce a brown-eyed child.
Some children are born with irises that do not match in color. This condition, called heterochromia, is usually caused by faulty developmental pigment transport, a local trauma to the uterus, or shortly after birth or a benign genetic defect.
Other causes include inflammation, a speck on the iris (diffuse nevus) and Horner’s syndrome.
takes place. If you notice an unusual look in your eye color, it’s not too late to see your eye doctor.
changes in eye color
The iris is a muscle that expands and contracts to control pupil size. The pupil dilates in dim light and contracts in bright light. The pupil also contracts when you focus on close objects, such as the book you are reading.
When the pupil size changes, the pigments in the iris are compressed or spread out, which changes the eye color slightly.
Some emotions can change both pupil size and iris color. This is why some people say that their eyes change color when they are angry or loving.
Eye color can also change with age. This occurs in 10 to 15 percent of the White population (usually people with lighter eye colours).
For example, my once very brown eyes are now a combination of brown, green and hazel. However, some Hazel Eyes actually darken with age.
If your adult eye color changes quite dramatically, or if the color of one of your eyes changes from brown to green or blue to brown, 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.
Source: https://www.allaboutvision.com/ Photo :https://www.matematiksel.org/