The color of a person’s eyes depends on the amount and type of melanin pigment present. Melanin is produced by cells called melanocytes and is responsible for determining eye color. There are two types of melanin – eumelanin which produces brown/black pigment and pheomelanin which produces red/yellow pigment.
How Eye Color Develops
Human eye color originates with three genes, two of which are well understood. These genes account for the amount of melanin (pigment) in the iris of the eyes. Blue eyes have low amounts of melanin in the iris, while brown eyes have high amounts of melanin. Green eyes have moderate amounts of melanin.
Everyone inherits one type of gene from each parent. The inherited genes interact with each other, which determines the final eye color. For example:
- If both parents have blue eyes, the child will also have blue eyes.
- If one parent has brown eyes and one has blue eyes, the child’s eye color could be blue, green or brown.
- If both parents have brown eyes, their children will most likely have brown eyes.
At birth, most babies have light blue or grayish eye color, yet the melanin pigment typically continues to develop during infancy. This means eye color can change quite a bit during the first year. Eye color changes happen more gradually after 12-18 months. By age 3, the colored part of the eyes is largely formed.
Do Blue Eyes Ever Turn Green?
The short answer is no, blue eyes do not actually turn green over time. However, sometimes blue eyes may appear to look more green or contain specks of brown during certain lighting conditions or due to other factors like trauma or medications. Here’s a bit more detail:
- Low light conditions – Blue eyes can sometimes appear greenish or gray in low light environments. But once lighting increases, the eyes will appear blue again.
- Medications – Certain drugs like epinephrine can temporarily decrease melanin production, making blue eyes look lighter. Other drugs like chloroquine (anti-malaria) may increase melanin and make blue eyes look darker or greenish.
- Injuries – Trauma to the eye may trigger increased melanin production during healing. This could result in a blue eye acquiring traces of brown/green pigment that weren’t there before.
- Age-related changes – With advanced age, the total amount of melanin pigment may gradually decrease. This could make blue eyes paler or lighter as a senior.
What Age Are Eye Colors Set?
Eye color is considered to be set by age 3. After the first year of life, the eye color a child is born with begins to stabilize and will remain the same into adulthood. However, there are some exceptions:
- Up until 6 months of age, many babies have blue/gray eyes. Eye color continues to develop until age 1.
- For children 1-2 years old, hazel eyes may shift in color.
- By age 5, nearly all blue/brown/green eye colors are finalized.
- Teens can sometimes develop flecks of new color in the iris around puberty.
- Eyes may become paler with age as melanin levels decrease.
While unusual, there is a slight possibility for blue eyes to get darker over the years if trauma or medications trigger additional melanin production. But generally speaking, the eye colors people are born with remain stable throughout life.
How Common is Each Eye Color?
Here is a breakdown of common eye colors and their estimated frequency in the global population:
|Less than 1%
As shown, brown eyes are by far the most prevalent eye color worldwide. Blue eyes are relatively rare globally, but are more frequently seen in European countries and other regions farther from the equator. Hazel, green, gray and other eye colors make up only a small percentage of the world’s population.
What Affects Eye Color?
There are several factors that help determine a person’s eye color:
- Genetics – The melanin production genes inherited from parents are the primary influence.
- Melanin concentration – Higher levels produce brown/black while lower levels appear blue/green.
- Melanin quality – The type of melanin (eumelanin vs pheomelanin) also affects color.
- Environment – Conditions like geography and climate impact melanin production.
- Ethnicity – Those with darker complexions and skin often have brown eyes.
A combination of these factors is responsible for whether a baby is born with blue, brown, hazel, green or other eye shades. The melanin levels and genetics set at birth will then determine how eye color develops as a child matures.
Can Eye Color Indicate Health Problems?
For the most part, eye color does not directly correlate with increased health risks or vision problems. However, there are a few possible associations to be aware of:
- Light eyes may be more vulnerable to sunlight damage and UV exposure effects.
- Hazel/green eyes are sometimes seen with Wilson’s disease (copper accumulation).
- Albinism often causes very pale blue eyes due to lack of pigment.
- Some rare syndromes involve eye color changes or heterochromia (two different colors).
Overall, brown, blue, green and other natural eye colors are considered healthy variations with no medical downsides. However, if you notice significant ongoing changes to eye color or hue, it’s a good idea to mention that to an eye doctor.
In summary, it is quite rare for blue eyes to turn green after infancy and childhood development. Short-term color variations can sometimes occur due to lighting, medications, injuries or aging effects. But one’s natural eye color is set genetically early in life and remains relatively permanent barring any trauma or pigment disorders.
If you are born with cobalt blue eyes, you can expect your eye shade to stay that way throughout adulthood. While environment, ethnicity and health can influence eye colors to some degree, genetics play the biggest role in determining whether you have blue, brown, green or hazel eyes from birth.