Facts About People With Green Eyes
While I have lots of friends, only one has green eyes. Her eyes are the first things you notice when you first meet her. Green eyes are among the rarest eye colors in the world. However, they are common in some countries. Lots of people in Iceland have green eyes. In fact, over 80% of Icelanders have either green or blue eyes.
Scientists used to think that eye color is a simple genetic trait. They now believe it is a complex one. This means that the genetic trait for eye color is determined not by a single pair but by multiple pairs of genes, possibly interacting with each other.
Eye Pigments of People with Green Eyes
Before we dive into why some eyes appear green, let’s get one thing straight. There are no green pigments in the eye!
Let’s now define a couple of things. The part of your eye with the color is called the Iris. This is the part that surrounds the pupil. The iris controls the dilation and constriction of your pupils.
If you shine a light into someone’s eye, his or her iris will contract reducing the size of the pupil. This function of the iris is important in regulating the amount of light that enters the eye.
Meet Hagop. He is having fun dilating and constricting his pupils.
Eye color depends very much on the amount of pigment on the surface of the iris. It also depends on the way light is scattered inside the eye.
Two pigments involved in eye color are Melanin and Lipochrome.
Melanin is a brown pigment that is also responsible for the color of your skin and hair. Lipochrome is a yellowish pigment responsible for the golden tone in amber eyes.
Why do Green Eyes Appear Green
Before melanin kicks in, the iris usually has a bluish tint to it. This is the reason why most babies are born with blue eyes. Melanin starts creeping into the eye as the baby grows up, usually as from the sixth month after birth.
Blue-eyed individuals have very little melanin and lipochrome on their irises. The blue eye color is due to a low melanin concentration and the way light is scattered in the iris. This phenomenon of “scattering of light in the iris” is known as Rayleigh scattering.
Rayleigh scattering happens in the presence of very little melanin. Longer wavelengths of light pass straight through the eye and are absorbed at the back of the eye. On the other hand, shorter wavelengths (otherwise known as blue wavelengths) are reflected and randomly scattered by the turbid layer of the iris. The blue wavelengths are responsible for the blue hue of the iris. This doesn’t work for brown eyes because they have more melanin. Melanin absorbs a lot light.
People with green eyes have a bit more melanin and even more lipochrome on their irises than people with blue eyes. The green color is from a combination of a blue hue from Rayleigh scattering and “yellow” from the yellow pigment (lipochrome).
The higher the melanin concentration in the iris, the darker the eye color will to be. People with brown eyes have high concentrations of melanin on their irises. So, you all with “dark” eyes have blue ones underneath all your pigments.
Personality Traits Associated with Green Eyes
Here is an interesting theory you may have already heard about. It is completely based on observation.
People often associated certain eye colors with specific personality traits. Some say that people with blue eyes tend to be kind and sweet.
What personality traits would you associated with people with green eyes?
If it is true that people often associated certain eye colors with specific personality traits, then you could wear contacts to alter the way people perceive you. Maybe you should try some blue contacts. It might make you look a little ‘sweeter’.
Genetic Determination for Green Eyes
We used to believe that eye color is a simple genetic trait. For example, it was thought that two parents with blue eyes can never have an offspring with brown eyes. This has been repeatedly shown to be wrong.
Scientists now believe that eye color is a polygenic trait. That is, a complex trait determined by multiple genes.
There are several genes thought to play a role in human pigmentation.
When it comes to genes for melanin production, one that stands out is OCA2. Scientists believe this gene is probably one of the most important genes in determining the amount of melanin to be produced in the iris.
The OCA2 gene contains instructions for melanin production. You may look at it like a recipe for melanin production. As we all know, sometimes there is an unexpected change in part of a gene. This is called Mutation. It results in an altered or damaged gene. Some mutations are severe, such as "growing an extra leg". Other mutations are unnoticeable, such as those for green or blue eyes.
Mutation in the OCA2 gene can cause melanin production to shutdown completely, such as in albinism. Or it could be less severe, only reducing the production down to a minimum, such as for green or blue eyes.
Do you have something to share about people with Green Eyes? Please tell us in the comment section below.