10 Fascinating Facts About Your Eyes and How We See the World

4. Blue-eyed people share a common ancestor

If you have a pair of baby blues, you're among the 8 to 10 percent of the population worldwide with blue eyes, which are the result of a mutation that causes the irises to lack pigment. Researchers believe this mutation first appeared in a person who lived in Europe between 6,000 to 10,000 years ago, meaning all blue-eyed people alive today share a common ancestor.

5. How you feel affects what you see

For people struggling with depression, saying that the world seems drab, flat, or gray may be more than a metaphor. Research has found that individuals with major depression experience measurable differences in how their eyes perceive contrast, which validates the idea that mental health can influence how we see our surroundings.

6. Night vision occurs slowly

If you feel like your eyes need time to adjust to a dark room, that's because they do. Night vision takes between 20 and 30 minutes to “turn on” through a process known as dark adaptation. Even once our eyes have adjusted, our surroundings appear mostly black-and-white because the rod cells that allow us to see in dimly lit conditions aren't responsible for color vision.

7. Fooled by your eyes? Blame the brain

When it comes to vision, eyesight is only part of the equation — visual information is captured by our eyes but processed by more than 30 areas of the brain. Optical illusions, for example, work by tricking the brain into incorrectly interpreting what your eyes see or by creating a new image that isn't there at all.

8. Your eye color is one-of-a-kind

Just like fingerprints, the colors and patterns within the iris, or colored part of the eye, are unique (so unique, in fact, that iris scans have been found to be more successful than fingerprint recognition technology). Even identical twins who share DNA don't have identical irises.

9. 20/20 vision isn't “perfect”

We often call 20/20 vision “perfect,” but that measurement simply means someone is able to see an eye chart as expected from 20 feet away — meaning it's possible to see even more sharply. One study of professional baseball players, for example, found that more than three-quarters of players had 20/15 vision or better, meaning they could see clearly from 20 feet what the average person sees at 15.

10. Color blindness is a guy thing

Some form of color blindness, or color deficiency, affects approximately 1 in 10 men, most often resulting in trouble distinguishing between red and green tones. Less commonly, someone might not be able to tell blues and yellows apart.