Eye color differences result from high melanin levels, genetic inheritance, light reflection and scattering, and evolutionary adaptation. Dark brown eyes are due to high levels of the pigment melanin in the iris, which absorbs light, making them appear darker.
What causes brown eyes?
The brown color of the eyes is due to the iris, which is composed of two layers of muscle (front & back) and other cell types. In most people, the back layer contains at least some brown pigment, even if their eyes don’t look brown. Therefore, the more melanin, the darker the eyes’ brown color. This also leads to variation in brown eye color among individuals, ranging from light honey to dark chestnut, with brown being the world’s most common eye color. These eyes dominate globally, appearing in diverse shades that shift with light and genetics.
Melanin’s Role
Understanding melanin’s role is important to understanding why there are various shades of brown in the eyes. Obviously, melanin concentration dictates the shades of brown eyes. This pigment absorbs light effectively, lending a protective, sun-filtering quality akin to natural sunglasses. Melanin is a natural pigment produced by specialized cells called melanocytes. It is responsible for giving our skin, hair, and eyes color, and it also helps protect tissues from harmful sunlight.
Types of Eye Color Due to Melanin Levels
Eye color is mainly decided by the amount and type of melanin present in the iris (the colored part of the eye):
- High melanin levels absorb more light, making the eyes appear dark brown or black.
- Moderate melanin levels result in light brown eyes or hazel eyes.
- Low melanin levels allow more light to scatter, making eyes look blue, green, or grey.
Melanin itself is brown in color. So, the more melanin in the iris, the darker the eye color appears. People with less melanin don’t have blue pigment in their eyes—rather, the blue color is created by how light scatters in the iris.
Types of Brown Eyes and Their Meanings
There are various types of brown eyes depending on the amount of melanin in the iris.
1. Light Brown Eyes
Light brown eyes have lower melanin levels and appear as a soft, golden, or honey-like shade. They contain less melanin than darker brown eyes, allowing more light to reflect, giving them a lighter appearance. This eye color is often seen in people from mixed ethnic backgrounds.
2. Honey Brown Eyes
This color appears. When melanin is present in moderate amounts and evenly distributed across the iris, it results in honey-brown eyes with a warm, golden-yellow tone, similar to honey. Honey brown eyes often look brighter in sunlight.
3. Hazel Brown Eyes
About 5% of the worldwide population is believed to have hazel-brown eyes, and this eye color is more common in Europe, the Americas, and West Asia. Hazel brown eyes are a mix of brownish and green tones. The color may change slightly depending on the lighting or clothing. This happens because melanin is unevenly distributed in the iris, resulting in different shades. Hazel eyes are a bit of a mystery. For starters, people describe this beautiful eye color in many different ways. Some say it looks like a hazelnut, while others call it golden or brownish green. The colors can also seem to blend together in some people. Hazel eyes are hard to describe because their color often looks different. It can change depending on the clothes you wear and the lighting around you.
4. Medium Brown Eyes
Medium brown eyes are around 45–50% of the world’s population and are widely observed across Asia, Africa, the Middle East, and parts of Europe. Medium brown eyes are the most common type of brown eyes. They have a normal amount of melanin, which gives them a natural and warm brown color. This eye color usually appears the same in different lighting conditions.
5. Dark Brown Eyes
Dark brown eyes appear deep and almost black in some lighting. They contain high levels of melanin, which absorbs most of the light. This makes the eyes look darker and provides better natural protection from sunlight.
6. Chestnut Brown Eyes
According to surveys, less than 3% of the global population has chestnut-brown hair. Chestnut-brown eyes have a reddish or coppery tint mixed with brown. This shade is created by melanin and subtle variations in light reflection within the iris.
Ayurvedic Eye Care for Brown Eyes
In Ayurveda, eye color is often linked to Pitta dominance, which is associated with heat and intensity in the body. People with brown eyes show a much higher tolerance towards sunlight and glare.
The higher melanin concentration that dictates the shades of brown eyes can offer some protection against harsh light and environmental stress. Ayurvedic eye care for brown eyes is needed, as they can still experience problems such as dryness, burning sensation, blurred vision, cataracts, glaucoma, or age-related eye weakness. Excessive heat, poor digestion, stress, or prolonged screen time can disturb brown eye health, one of the strongest eye types.
Due to high pigmentation, the brown eye color may sometimes mask early warning signs, making it harder to notice redness, tiny blood spots, or pigmentation changes. Therefore, it is highly recommended to undergo regular eye examinations and preventive care, which is especially important after the age of 40.
Ayurvedic eye care focuses on pacifying the eyes by cooling, nourishing, and strengthening them through proper diet, lifestyle balance, herbal formulations, and, when required, therapies such as Netra Tarpana and Anjana. Therefore, with regular eye care, brown eyes can maintain clarity, comfort, and long-term visual health.
Brown Eye colors & Genetics
In humans, eye color is determined by the amount of light reflected by the iris, a muscular structure that controls how much light enters the eye. The range in eye color, from blue to hazel to brown, depends on the level of melanin pigment stored in the melanosome “packets” in the melanocytes of the iris.
- Blue eyes contain minimal amounts of pigment within a small number of melanosomes.
- Green-hazel eyes show moderate pigment levels and melanosome number.
- Brown eyes are the result of high melanin levels stored across many melanosomes.
To date, eight genes have been identified that impact eye color. The OCA2 gene, located on chromosome 15, appears to play a major role in controlling the brown–blue color spectrum. OCA2 encodes a protein called P-protein, which is involved in melanin formation and processing.
Individuals with OCA2 mutations that prevent P-protein from being produced are born with a form of albinism. These individuals have very light-colored hair, eyes, and skin.
Conclusion:
Eye color, especially brown eye shades, is shaped by a combination of melanin levels, genetic inheritance, and the way light interacts with the iris. Brown eyes appear darker because they contain higher amounts of melanin, a natural pigment that absorbs light and offers a degree of protection from sunlight. This same melanin is responsible for the wide range of brown eye shades—from light honey and hazel brown to deep dark and chestnut brown.
Genetics plays a key role in deciding eye color, with genes like OCA2 influencing how much melanin is produced and stored in the iris. While brown is the most common eye color worldwide and often comes with natural strength and sun tolerance, it does not make the eyes immune to disease or age-related changes.
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