Have you ever wondered why some people have blue eyes, or what would happen if you wore a pair of glasses which flipped your vision upside-down? The answer may be no, but it's quite amazing nonetheless. We've collected what we think are 7 of the most amazing eye facts, and put them into an infographic.
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Tweetable Eye Facts
#1 Your eye colour depends on the amount of melanin in your iris. Tweet this Fact
Melanin is a dark brown pigment that decides not only your eye colour, but also the colour of your hair and skin.
The more melanin you have in your iris, the darker your eyes will be: blue eyes contain much less melanin than dark eyes, allowing a blue substance called collagen to show through.
#2 Do you have blue eyes? If so, you share a common ancestor with every other blue-eyed person in the world. Tweet this Fact
The first ever blue-eyed person lived sometime between 6,000 and 10,000 years ago.
He or she was born with a gene which could not produce enough melanin to create brown eyes, resulting in a unique DNA sequence that was transmitted to every other blue-eyed person ever since: despite thousands of years having passed, each and every person with blue eyes can still be traced back to this single ancestor.
Scientists observed a lot of variation in the amount of melanin contained in the iris of brown-eyed people. However, the amount of melanin in blue-eyed people’s irises is a lot less variable, which points to blue eyes being handed down by a single person thousands of years ago.
#3 If you have 20/20 vision, your eyesight is just ‘normal'. Tweet this Fact
20/20 vision is actually an American term: according to eye doctors, it corresponds to what a person should “normally” be able to see when looking at an eye exam chart from a distance of 20 feet.
If you can read what the average person can normally read from a chart placed at a 20 feet distance, you’ll have 20/20 vision. But this isn’t the best vision quality you can have - some people with exceptional eyesight have 20/10 vision, which in a way is twice as good as 20/20.
#4 If you wore a special pair of glasses which flipped images upside down, your brain would correct your vision. Tweet this Fact
Your brain processes all the information that your eyes collect, allowing you to see. If you wore glasses which flipped everything upside down, it would over time learn to process the information differently, so that you see things the right way up again.
However, we don’t recommend trying this at home: it could take up to a few weeks for your brain to adapt, and you would see everything upside down again after taking the glasses off.
#5 Your eye contains over 107 million cells which are sensitive to light. Tweet this Fact
The two types of cells located in your retina at the back of your eye are called ‘rods’ and ‘cones’.
There are around 100 million rods, which allow you to see better in the dark but can’t recognise colours. The other light-sensitive cells, cones, amount to around 7 million and allow you to see colours and details.
How do these cells help you see? It all happens thanks to a chemical reaction, which takes place just a few trillionths of a second after light has come into contact with the rods and cones in your eye. The electrical impulse triggered by this reaction is then transmitted to your brain, which processes the information and allows you to see.
#6 On average, you blink 17 times per minute, and around 5.2 million times a year. Tweet this Fact
Have you ever thought about how often you blink?
On average, you probably blink around 17 times a minute and 5.2 million times in a year, but the amount of times you actually blink varies and depends on what you are doing.
If you’re talking to someone, you tend to blink more often: on the other hand, you blink less when you’re reading (which is why you get dry and tired eyes).
#7 The muscle which controls your eyelids and blinking is the fastest muscle in your body. Tweet this Fact
The saying “in the blink of an eye” was coined for a good reason.
The muscle that controls your blinking is the fastest in your body, and your average blink tends to last between 100 and 150 milliseconds. Blinking is also important to your eye health, removing debris and keeping your eyes moist with tears so that they don’t dry out.