Why do people have different eye colors?

Ever look in the mirror and wonder why your eyes are the color they are? Learn what gives eyes their color, common eye colors around the world, and how your eye color may impact your health.

Understanding what gives eyes their color

Whether you have eyes of deep brown, vibrant blue, or rare green, the primary thing that gives your eyes color is the pigment known as melanin. Located in the iris, melanin is found in different amounts in different people, and even in the different eyes of the same person. The presence of a high concentration of melanin typically results in brown eyes, while lower levels lead to lighter eye colors like blue or green. Your eye color is mostly determined by the genetics you inherit from your parents, but it’s not as straightforward as a “mixing” of their colors. The complex combination of genes involved in eye colors makes for a wide array of eye color possibilities.

The role of genetics in eye color

Scientists used to think that eye color was based on simple genetics, but more updated research shows that that eye color is determined by more than 50 different genes. The interplay between all of these genes determines an individual's eye color. This genetic complexity is part of why there can be so many colors and shades of eye color, even within the same family. For example, two brown-eyed parents may still have children with blue or green eyes, depending on the combination of genetic traits inherited. Genetic research has also shown that certain eye colors may become more or less common depending on geographical and environmental factors. For example, populations living in sunnier climates tend to have darker eye colors. This adaptation likely provides some degree of protection against the harmful effects of ultraviolet (UV) rays.

Common eye colors around the world

While these eye colors cover a majority found in the human population, there is nearly endless variation within each color, and other eye colors do exist. For example, people with albinism often have irises that appear pink due to the complete lack of pigment.

Brown

Brown is the most prevalent eye color in the world, with over 50% of the population having varying shades of brown. Brown eyes can range from light honey to dark chestnut, influenced by the amount of melanin present. Dark brown eyes tend to be more common in individuals of African, Asian, and Hispanic descent.

Blue

Blue is the second most common eye color, particularly among individuals of European descent. Different colors of blue eyes can vary considerably, from light sky blue to deep navy. Interestingly, genetic studies suggest that all blue-eyed individuals share a common ancestor, stemming from a genetic mutation that occurred approximately 10,000 years ago.

Green

Green eyes are one of the rarest eye colors, accounting for only about 2% of the global population. The unique hue of green eyes arises from the combination of low melanin levels and the presence of a yellow pigment called lipochrome. Variations in lighting can also affect the appearance of green eyes.

Hazel

Hazel eyes feature a mix of green, brown, and gold shades, making them appear to change color depending on the environment. The structure of the iris and the scattering of light play a significant role in the intriguing appearance of hazel eyes.

Gray

Gray is another uncommon eye color that can appear almost blue under certain lighting conditions. This color is characterized by low levels of melanin.

Heterochromia: people with two differently colored eyes

Ever seen someone with a brown eye and a blue eye? This is called heterochromia. This striking phenomenon can be hereditary but may also arise from injuries, certain diseases, or even specific medications. While most instances of heterochromia do not impact health or vision, adults experiencing changes in eye color should consult a healthcare provider.

Complete Heterochromia:

One eye is a different color from the other. For instance, an individual may have one brown eye and one blue eye.

Partial Heterochromia:

A single eye contains two different colors, where typically part of the iris is one color and the rest is another.

Can eye color influence your health?

Research has suggested that eye color may be linked to certain health conditions, although these associations are not fully understood. Despite these potential associations, it is essential to recognize that numerous factors contribute to individual health. Eye color is just one of many traits that can influence overall well-being.

Eye color can increase risk of certain diseases

Studies indicate that people with brown eyes may have a lower risk of developing macular degeneration and certain types of skin cancer, but a higher risk of developing cataracts.

Increased sensitivity

Lighter-colored eyes, such as blue or green, may be more sensitive to bright light and glare. This sensitivity can be inconvenient and may lead to discomfort in sunny environments.

See an eye doctor with any questions

If you have questions about your eye color or experience any changes in your eye color, speak with your eye doctor. Be proactive—making sure to address any concerns quickly and keep up with regular eye examinations can help you maintain good eye health.

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FAQs

Frequently Asked Questions

Can two blue-eyed parents have a brown-eyed child?

Yes, it is possible for two blue-eyed parents to have a brown-eyed child if they carry right mix of genes for brown eyes.

Are there health issues associated with eye color?

Some evidence suggests that lighter-colored eyes may have increased sensitivity to light, while darker eyes may have a slight protective advantage against certain health conditions.

Do all babies have blue eyes at birth?

Not all babies are born with blue eyes; some are born with brown or darker shades. No matter what color a baby starts with, it may change during the first few years of life as melanin develops.

What is heterochromia?

Heterochromia refers to having two different colored eyes or different colors within one eye. It can be genetic or acquired due to injury or health conditions.

When should I see a doctor about my eye color?

If you notice any changes in your eye color or have concerns, speak with an eye care professional for guidance.