We like blue, green and other eye colors more than brown eyes because of their rarity and good looks of them. However in fact, we all have brown eyes.

How is eye color formed?

A person’s eye color is caused by the pigmentation of a structure called the iris, which surrounds the small black hole in the center of the eye (pupil) and helps control how much light can enter the eye. The color of the iris ranges from very light blue to dark brown. Most often, eye color is classified as blue, green/hazel or brown. Brown is the most common eye color worldwide. Eye color is determined by variations in a person’s genes. Many of these genes are involved in the production, transport or storage of a pigment called melanin. A person’s eye color is determined by the quantity and quality of melanin in the front layers of the iris. People with brown eyes have a lot of melanin in their iris, while people with blue eyes have much less. Everyone has melanin in the iris of their eyes. The amount of this melanin determines the eye color of the person. Melanin is the chemical that determines skin, complexion, hair and eye color. Melanin is dark brown in color and becomes darker as its concentration increases. This is because, depending on its concentration, melanin’s ability to absorb light increases.

The Physics Behind Our Eye Color

If a person has brown eyes, there is likely to be plenty of melanin in both the upper and lower layers of their iris. But people with blue eyes have little or no melanin in the top layer of their iris. The reason we perceive their eye color as blue is the same reason we perceive the sea or the sky as blue. In people with green or hazel eyes, one or both layers of the iris contain light brown pigment. The light brown pigment interacts with blue light and the eye may appear green or mottled. Many people have variations in iris color, usually with one color close to the pupil and the other at the edge. This variation occurs when different parts of the iris have different amounts of pigment.

The laws of physics also play a role in the background. This is explained by Rayleigh scattering. White light from the Sun collides with many particles as it travels through the Earth’s atmosphere. The amount of scattering that occurs depends on the wavelength of the light. The shorter the wavelength, the greater the amount of scattering. As a result, short-wavelength blue light is scattered to a greater extent than long-wavelength red light. This explains why the sky and your eyes appear blue.

Eye Color is Often Not Constant

When babies are born, their eyes are usually blue because their melanin is still forming. Their eye color may darken later as the amount of melanin develops. Since blue and green/hazel eyes get their color from incident and reflected light, they can also appear as different colors depending on the lighting conditions. When babies are born, there is usually not much pigment in their iris. This is why their eyes look more blue. However, over time, usually a few months after birth, more and more pigment begins to accumulate in the eyes. This is why blue eyes gradually become darker or turn brown. For most children, eye color becomes stable after the first year. For some children, however, the color will continue to change for several more years.

April 2023