They've been called the window to the soul. But your eyes are also one of the most unique parts of your body, with over 2 million individual components, making them the second most complex organ... after the human brain.
Here are 10 other strange-but-true facts about your eyes.
1. You See the World Upside Down & Split in Half
When you first view an object, the image is actually processed by your eyes upside down (not unlike how the mirror in an old fashioned camera works). What's more, the image is split in half and distorted. Your retina flips the image, matches the two pieces together and clears up the distortion before sending the visual signal to your brain—with all of this occurring in nano seconds.
2. You Blink 9 Million Times a Year
On average you blink 17 times each minute. That works out to nearly 25,000 blinks a day and over 9 million blinks a year. Your eye also happens to be the fastest muscle in your body, which is how a single blink can happen in less than four-tenthsof a second—all of which may explain the old saying "in the blink of an eye."
3. Your Retinas Can't See Red
The receptors in your retina that process colours are actually only capable of detecting yellow-green and blue-green combinations. Your brain combines these different signals and identifies colours that are missing as being red.
4. Different Things Produce Different Tears
While the main purpose of tears is to remove dirt and harmful bacteria from the eyes, research has found that our tears are actually chemically different depending on the situation. Scientists have found that "reflex tears" (such as those caused by allergies or getting something in your eye) were dramatically different than "emotional tears" (such as those caused by pain or feelings of sadness and joy). In fact, scientists don't really know why we produce tears when we're upset.
5. Your Eyes Are the Same Size Now as When You Were Born
Unlike other parts of your body (such as your nose and ears) your eyes stay basically the same size throughout your life. Scientists speculate that this is because your eyes are so complex that even subtle changes in growth could affect your overall vision. In fact, babies' eyes start to develop in the womb just two weeks after conception takes place.
6. "Red Eye" is Caused by Blood Vessels
Red eye may be the bane of photographers everywhere, but there's actually a fairly simple explanation behind this well-known phenomenon. Red eye occurs because light from the flash of the camera bounces off the back of your eye, hitting the choroid, a layer of tissue located directly behind the retina. The choroid also happens to contain a lot of blood vessels that are captured by the camera and why your eyes end up appearing red on film.
7. Your Eyes Are More Unique Than Your Fingerprints
We often assume that our eyes are similar to other people because we have the same prescription or the same eye colour. In fact, your eyes are incredibly unique. To put this into perspective, your fingerprints have only 40 unique identifying characteristics. Your eyes, on the other hand, have over 256 identifiable characteristics just in your irises alone. This may explain why governments and banks around the world are now looking towards biometric eye scans as a new form of identification.
8. Only 1/6 of Your Eyeball is Exposed
It turns out that only a small portion of your eyeball is exposed at any given time. That's because a lot of what happens with your vision occurs inside your eyeball and involves millions of sensitive nerves and blood vessels. In fact, human skulls have evolved over the years to offer a maximum amount of protection to the part of your eyes that are unexposed.
9. Your Eyes Process 36,000 Bits of Information Per Hour
It turns out that your eyes are constantly taking in information that's then analyzed by your brain. In fact, researchers estimate that your eye will focus on about 50 objects per second. That's roughly comparable to the amount of data that's processed by a powerful computer.
10. Shark Corneas Are Used in Eye Surgery
It turns out that some of the most successful corneal transplants haven't come from human donors, but rather from sharks. That's because scientists have discovered that shark corneas have thick reinforcing fibres that function much like rebar does in concrete buildings. These fibres strengthen the cornea and prevent it from swelling and turning cloudy, like human corneas can do. In addition to transplanting shark corneas into human patients, scientists have continued to research sharks to understand human eye diseases.
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