Since ancient times, people have been interested in the mystery of eye colors. Some believe that the eyes reveal a person's personality, others that it is an indicator of health.
What determines eye color? Brown, blue, green... What is the secret behind each eye color? Eyes come in many shades from dark brown almost black, to light brown and from green to grey and blue.
Despite the many variations we perceive, there are only two different pigments in our eyes: brown and red.
Revealing The Mystery Of Eye Colors
The iris is 12 millimeters in diameter and is made up of connective tissue and a thin muscle that allows it to open according to the light. The color of the eyes depends on the amount of pigment and connective tissue.
The pigment cells of the iris, called melanocytes, produce two different types of pigment: eumelanin - brown or black, and pheomelanin - red or yellow.
Eye color is determined by the pattern of brown and red pigment, collagen fibers, and the topography of the iris.
Black or almost black eyes are the most pigmented, and light blue eyes have the least amount of pigment. Light blue eyes are more common in people from Europe. However, there is no blue pigment in our eyes. So how come they are blue? Because of the white collagen fibers in the connective tissue in the iris. These fibers propagate light and so the iris looks blue.
Eye colors that fall between the dark brown and light blue ranges have varying amounts of pigment as well as areas without pigment. This causes the unique colors we see as green and grey.
But it's not just color that makes our eyes unique. The physical topography of the iris plays a very important role. When we examine our eyes, we notice several patterns. The easiest to notice is the pigmented ring that surrounds the pupil.
Curiosities About The Human Eyes
Eyelashes And Eyes
For many years, geneticists have believed that a single gene determines the color of a person's eyes, with brown eyes dominating blue eyes. However, two parents with brown eyes can have children with blue eyes. Although eye color is inherited, it is now known that several genes contribute to the spectrum of colors we see in people.
In terms of eye color, the total number of genes responsible now stands at 11. A group of researchers led by Manfred Kayser, professor of forensic molecular biology at the Erasmus Medical Centre in Rotterdam, the Netherlands, analyzed the variants of these genes in more than 3,000 people from 7 European countries.
Eumelanin is brownish-black and pheomelanin is red. By comparing these genetic profiles with a new method that assesses eye color in photographs, scientists were able to accurately predict eye color in the vast majority of cases.
There Are Five Rare Eye Colors
Some years ago, the Spanish daily ABC published a documentary about these five rare colors.
1. Amber eyes. The yellowish eye color is caused by excess lipochrome in the iris and is found in Brazil, Europe, and Asia. So far, no genetic explanation has been found for this unusual color.
The famous French singer Marie Laforet is known as the "Girl with the Golden Eyes".
2. Purple eyes. This color is due to a mixture of shades of red and blue. This type of violet eyes made Liz Taylor famous.
3. Black eyes. In this type of eye, you can't tell the iris from the pupil. This is due to the very dark color of the iris or the total lack of it. Only 1% of the world's population has black eyes, with the highest numbers found in Asia, Africa, and America.
4. Red eyes. Red is the rarest color, being characteristic of albinos. Here the iris contains no melanin at all, and light passes through it and reflects hemoglobin from the blood vessels on the retina, giving this hue.
5. Green eyes. Although we have the impression that there are many people with green eyes, only 2% of the population has this hue. These eyes are found in Hungary, Iceland, Europe in general, as well as in some ethnic groups in Iraq and Afghanistan.
The beauty of the eyes has captivated mankind for thousands of years, giving rise to famous expressions such as "the eyes are the mirror of the soul".