All About Gray Eyes: Rarity, Genetics, and Causes

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A fun look at one of the most unique eye colors
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Gray eyes are mysterious and beautiful, but did you know that a lot of people don’t even know gray exists as an eye color? That’s partially because it’s so rare, but it’s also a consequence of people mistaking gray eyes for blue or green eyes. In this article, we’ll break down just how rare this eye color is and what causes it, and even share some fascinating and bizarre facts surrounding gray eyes.

How rare are gray eyes?

Grey eyes are the second rarest eye color on the planet (after green eyes), and they’re unique in how much variation there can be from person to person. They’re caused by a lack of melanin in the two layers of the iris, which creates a cool, smoky color with a lot of flecks, rings, and angles.

Section 1 of 5:

How rare are gray eyes?

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  1. Gray eyes are likely the second rarest eye color . The rarest eye color is green, which is only present in about 2% of people worldwide. [1] It’s estimated that less than 3% of the world’s population has gray eyes, making them the second rarest eye color. [2]
    • These stats are based on “standard” eye colors and don’t take into account anomalies like red eyes caused by albinism.
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Section 2 of 5:

What do gray eyes look like?

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  1. 1
    Gray eyes typically have a smoky, silvery hue. Gray eyes tend to have lots of variation, especially compared to brown eyes (which are the most common), so two people with gray eyes may have totally different patterns or colors. The hues are typically a “dusty” silver with lots of freckles, tiny spots, and rings. Gold rings are especially common, although you can also find blue or green rings. This is why gray eyes are often mistaken for blue or green eyes. [3]
    • Gray vs. Blue: Blue eyes tend to have a warmer tone than gray eyes, which tend to be cool and cold. Bluish-gray is probably the most common variation of gray eyes, so you can find eyes that sort of look like they could go either way.
    • Gray vs. Green: Look at the flecks in the eyes. Are they green ? If so, the eyes are probably green, not gray. You can 100% have gray-green eyes, they’re just exceptionally rare.
  2. 2
    Gray eyes have more collagen in their stroma. The stroma is the thickest and most transparent layer of the eye. People with gray eyes have no melanin here, which causes light to scatter differently. This is why there is so much variation from person to person with gray eyes—the stippling in the stroma is different every time. [4]
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Section 3 of 5:

What causes gray eyes?

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  1. The amount of melanin in the iris creates the gray coloration. Melanin is brown. This is why people with a lot of melanin tend to have brown (“black”) skin, and why people with brown eyes tend to have darker features. Gray eyes have very little melanin (almost none), which gives them their haunting, expressive coloration. [5]
    • The iris of your eye actually has two layers of melanin. Those layers aren’t normally noticeable if the melanin is high, but with gray eyes the two layers can be visible. This is what creates so much variation and texture in gray eyes—one layer might be darker or have a different pattern than the other.
Section 4 of 5:

The Genetics of Gray Eyes

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  1. Gray eyes are the genetic result of an incomplete dominance. Eye color is known as a polygenic trait, which means that it’s determined by multiple genes (instead of a single gene). It’s an example of incomplete dominance—a genetic phenomenon where multiple alleles are equally dominant. This is why gray eyes have such a wide range of different presentations: there is no single “winning” gene for the color. [6]
    • The genes responsible for this are the OCA2 and HERC2 genes. These are responsible for pigment production, so they’re directly responsible for how much melanin you have in your eyes.
    • Blue eyes may be identical to gray eyes, genetically speaking. Remember how we have two layers of pigment in our eyes? It’s possible that gray eyes are genetically the same as blue eyes, just that the order of the most melanated layer is different. Blue eyes have the darkest layer at the back, while gray eyes have the darkest layer in the front. [7]
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Section 5 of 5:

Fun Facts about Gray Eyes

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  1. 1
    Gray eyes are mainly found in Northern Europe. You’re much more likely to have gray eyes if you (or your ancestors) are from Iceland, Ireland, Sweden, Finland, or Norway. Gray eyes are almost nonexistent in Asia, Africa, and South America. [8]
    • One major exception is the Kurdish people of the Middle East. Up to a quarter of Kurds have blue, green, or gray eyes. This figure is even higher among Yazidi Kurds. [9]
  2. 2
    People with gray eyes are more sensitive to light. As weird as it may sound, people with gray eyes actually can’t look at bright lights as well as people with darker eyes. Since there’s almost no melanin, there isn’t as much physical “stuff” to filter the light as it enters your eyes, making people with gray eyes more likely to squint or shy away from lights. [10]
    • This is also why people with gray eyes are more likely to be diagnosed with ocular melanoma, an exceptionally rare eye cancer that is caused by exposure to UV light. [11]
  3. 3
    Gray eyes are probably stronger and less likely to decay over time. The science is still kind of out on this one, but there is some evidence that people with gray eyes have stronger vision that’s less likely to go bad as you get older. [12] Sensitivity to light being high means that people with gray eyes aren’t prone to look at bright light as often, and the extra collagen in gray eyes can potentially form a protective layer. [13]
  4. 4
    In the United Kingdom or Canada, you have “grey” eyes. Ever wondered what the difference between “gray” and “grey” is? It’s just a regional thing. If you’re British, Canadian, or Irish, you’re more likely to spell it “grey,” while Americans are more likely to say “gray.” [14]
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      • Celebrities with gray eyes include Megan Fox, Clive Owen, Pink, Hugh Laurie, Lisa Edelstein, Christopher Walken, and Olivia Wilde.
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      References

      1. ↑ https://my.clevelandclinic.org/health/articles/21576-eye-colors
      2. ↑ https://www.visioncenter.org/conditions/grey-eyes/
      3. ↑ https://www.ttdeye.com/blogs/grey-eyes-facts
      4. ↑ https://www.visioncenter.org/conditions/grey-eyes/
      5. ↑ https://my.clevelandclinic.org/health/articles/21576-eye-colors
      6. ↑ https://www.thetech.org/ask-a-geneticist/articles/2007/ask232/
      7. ↑ https://www.thetech.org/ask-a-geneticist/articles/2007/ask232/
      8. ↑ https://www.visioncenter.org/conditions/grey-eyes/
      9. ↑ https://defactostateofmind.medium.com/you-dont-look-kurdish-fefd8cb633b9
      1. ↑ https://www.dukehealth.org/blog/myth-or-fact-people-light-eyes-are-more-sensitive-sunlight
      2. ↑ https://myvision.org/eye-health/gray-eyes/
      3. ↑ https://myvision.org/eye-health/gray-eyes/
      4. ↑ https://myvision.org/eye-health/gray-eyes/
      5. ↑ https://www.merriam-webster.com/grammar/gray-vs-grey-usage-difference

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