Why Do We Have Different Eye Colors?
Your eye color is truly unique. No one else in the world has the exact same eye color as you. Along with being an identifiable feature listed on your driver’s license, it also serves as a distinguishing characteristic that shows family resemblance or even makes someone appear more attractive.
The eyes are often one of the first things we notice when we meet someone. Some people have brown eyes, some have blue or green, and some even have eyes that are a mix of colors! Although eye color varies widely among people and the patterns in the iris are complex, an eye exam reveals little about the origin of your eye color. The explanation for your eye color is embedded in your DNA and is determined before birth. Genetics and other factors play a role in determining eye color, but exactly how we inherit our individual eye color is complex and not fully understood.
So why is there color at all? Here are the basics on why we have different eye colors.
What Gives My Eyes Their Color?
Eye color is determined by the color of each eye’s iris, the double-layered ring of muscle tissue surrounding your pupil, that regulates how much light enters your eyes. The color of your iris is determined by genetics and the amount and type of pigments in the iris.
Genetics is the combination of genes inherited from each parent. It is widely believed that 10,000 years ago, all humans had brown eyes. Blue eyes emerged as a result of a genetic mutation that caused an individual to produce less melanin than normal, giving rise to the recessive blue-eyed gene. Subsequently, genetic mutations began to affect certain genes, reducing the amount of brown pigments being produced in the front of the iris.
The two primary pigments that determine eye color are melanin and lipochrome.
• Melanin is a pigment that gives color to the eyes, hair, and skin. The amount of melanin varies from person to person, and those with more melanin tend to have darker eyes, while those with less tend to have lighter eyes. Almost everyone possesses melanin in the rear layer of their iris, except for individuals with conditions such as albinism. A high concentration of melanin in both the front and back layers of the iris results in brown eyes, while those with less melanin in the front layer have hazel or green eyes, and those with minimal or no melanin have blue or gray eyes.
• Lipochrome is a yellow pigment present in the iris that contributes to assorted colors, particularly green or amber-colored eyes.
In reality, the diversity in eye color is simply due to the level of melanin in an individual’s system and the unique shape and configuration of their irises. Light reflecting off the iris fibers reveals a spectrum of colors, with each being uniquely beautiful.
Eye Color Variations
There are a limited number of main eye colors, but the variations in which they appear are nearly limitless. No two individuals have the exact same eye color, and even identical twins can exhibit subtle yet noticeable differences in eye color.
The most common eye color worldwide is brown, in various shades, accounting for approximately 70-79% of the population. Blue eyes, which likely originate from a single ancestor with a specific mutation, represent about 8-10%. The most common eye colors worldwide:
• Brown eyes (ranging from light to dark shades): 70-79%
• Blue: 8-10%
• Hazel (combinations of green, gold, or brown): 5%
• Gray: 3%
• Green: 2%
• Red or violet: less than 1%
• Heterochromia (differently colored eyes, in part or whole): 1%
Understanding Hazel Eye Color
Hazel eyes result from having less melanin in the irises compared to individuals with brown eyes, but more than those with blue or green eyes. Hazel eyes combine shades of brown, gold, and green, although the mix is not always equal. Some may have eyes that display only two of these colors, while others exhibit all three. The diversity among hazel eyes exemplifies the uniqueness of eye color.
Unique Eye Colors
The process that determines a person’s eye color is quite complicated, leading to rare and unique colorations. Some of the most uncommon and fascinating ones include:
• Amber Eyes – Amber eyes are rarely seen in humans but are more common in cats and other species. People with solid orange/gold eyes have a unique pigment called pheomelanin dominant within the iris. This pigment is also present in those with green eyes, although in much smaller quantities.
• Albinism – Individuals with albinism are born with a congenital disorder that affects pigment production in their bodies, causing either complete or partial loss of pigment. The absence of pigment prevents the iris from appearing opaque, allowing the red of the retina to be visible. Those with albinism may experience various eye conditions such as decreased visual acuity, light sensitivity, and crossing of the optic nerve fibers.
• Heterochromia – Similar to amber eyes, heterochromia is more frequently observed in animals like cats, dogs, and horses than in humans. Heterochromia is a rare condition that affects the iris, causing differing melanin levels in each eye, giving each a distinct color. For example, one eye might be brown while the other is gray. This condition is harmless when it is genetic. Heterochromia only needs to be treated if it occurs due to health conditions such as glaucoma, diabetes, eye tumors, certain medications, or eye injuries.
Eye Color Inheritance
Babies do inherit their eye color from their parents, but it’s not the only factor. The genetics behind eye color involve numerous genes and DNA mutations. While parental eye color plays a significant role, other factors can lead to differences in eye color between parents and their children, and eye color can skip generations.
It’s common for babies to be born with blue, gray, or light eyes that darken over time. This is because melanin production in the eye cells, triggered by light, takes time to develop after exposure to sunlight.
Eye color can change throughout a person’s life. It may change before a baby’s first birthday, in later life, or due to certain medical conditions.
Eye Color and Health
Eye color does not affect vision, although individuals with darker eyes may have less discomfort in sunlight due to higher melanin levels.
Eye color changes can occur with certain medications or medical conditions, some harmless and others indicative of serious issues, such as cataracts, glaucoma, Horner syndrome, and arcus senilis.
Additionally, eye color may correlate with disease risk; for example, brown-eyed individuals might have a higher risk of cataracts, while blue-eyed individuals could be more resistant to the effects of mental health conditions like seasonal affective disorder.
If you observe rapid eye color changes, especially if accompanied by vision changes or injury, consult an eye care specialist for evaluation and appropriate care.
We Appreciate the Beauty of Our Patients’ Unique Eyes!
Every individual’s eye color is distinctive and influenced by numerous factors. While there have been significant strides made in comprehending how genes and the environment contribute to eye color, there is still much to learn.
If you’re curious about your eyes or have further questions, the local vision care experts at Wise Eyes Optical have the technology and diagnostic expertise to address any vision concerns. We provide personalized family eye care, collaborating with you to address all your vision and eye health requirements.
Contact Wise Eyes Optical
Your Hometown Vision Center Serving Central Pennsylvania
Whether you require a routine eye examination, new contact lenses, corrective procedures, or eyeglass repair, we are dedicated to keeping you and your family informed and safeguarded. If you have questions or would like to learn more, reach out to your nearest Central Pennsylvania Wise Eyes Optical office and explore the best treatment options available for you and your loved ones. For assistance, call (717) 242-1915.
