Interesting Facts – Chapter 2

5 Amazing Facts About Our Eyes

Let's set off on an amazing journey through our eyes!

How our eye is built:

1) One of the most important parts of our eyes is super thin and see-through!
Imagine a fly suddenly zooms right in front of your face! Light bouncing off the fly enters your cornea – a thin, clear covering over the front of your eye. The light then passes through your pupil (the black circle in the middle of the colored iris) and on to the lens. But we’re not done yet! The lens focuses the light onto your retina, a thin, vital layer at the back of your eye. The retina works a lot like a camera, capturing the image of the fly. That image is sent to your brain, which instantly tells you: “Duck!” or “Wave your arms!” so the fly will buzz off somewhere else.

How the eye works:

2) We blink more than 10,000 times a day!
Our eyesight is incredibly important, so our bodies have clever ways to protect our eyes. Each eye sits on a cushion of fat, surrounded by protective bone. Your eyebrows stop sweat from dripping into your eyes, and your eyelashes keep out dust and other bits. Your eyelids work like windshield wipers, spreading tears with every blink to keep your eyes moist and wash away germs. And if something comes too close, your eyelids snap shut amazingly fast. How fast? In the blink of an eye – you can blink 2 to 10 times a second! Amazing!

3) Our eyes adjust in milliseconds to every move of our head!
Even when we’re not running or jumping, our heads are never completely still. So why isn’t everything blurry when we move? Our eyes automatically adjust to our head’s movement, quickly and precisely. They’re good at following moving objects, and even better at keeping up with our head. Try it: keep your head still, hold your hand up about 30 cm away and wave it quickly side to side. Your fingers get blurry. Now keep your hand still and shake your head side to side. Your fingers stay perfectly clear!

How the picture travels to the brain:

4) Our eyes see everything upside down and backwards!
Our eyes are amazing, but the pictures they send to the brain are a little strange – they’re upside down, backwards and flat! Luckily, our brain fixes all of that. It quickly flips the images from our retinas the right way up and combines the pictures from both eyes into one 3D image.
Each retina also has a tiny area called the “blind spot” that can’t record what we see. Our brain fills that in too – but sometimes we can trick it! Try this: hold the tips of your two index fingers together about 15 cm in front of your eyes. Look at them for about ten seconds. Now move them slightly apart and look past them at something far away. A little see-through floating finger appears between them! You just tricked your brain into seeing something that isn’t there!

5) Your pupils change size every time the light changes!
Our black pupils may be small, but they have a big job – they grow or shrink to let in exactly the right amount of light so we can see. Try this: go into a room without windows, turn off the light and close the door almost all the way, leaving just enough light to see your pupils in a mirror. They’ll be much bigger than usual, stretched wide to catch as much light as possible. Now switch on the light while you watch. You’ll see them shrink to tiny dots almost instantly – right before your eyes. Amazing!

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