Give it a try! Make an eye patch or just cover one eye with your hand for five minutes in a brightly lit room. Then turn off all the lights and open your eyes! If you want more from professor Hallux then you can find more here. Week 5: Eyes This week's missions are all to do with your eyes and how they work!
More From Week 5: Eyes. Who is Professor Hallux? More to click These cameras are your eyes…. A fly darts towards your head! The light passes through your pupil, the black circle in the centre of the iris, to the lens. The lens focuses the light onto your retina — a thin but vital lining on the back of your eye that is as flimsy as a wet tissue. Your retina acts like camera film, capturing the picture of the fly. This image is sent to the brain, which instantly tells you to — duck!
Your sight is incredibly important , so your body has ways to protect your eyes. Each eye sits on a cushion of fat, surrounded by protective bone.
Your eyebrows prevent sweat dripping into your eyes, while eyelashes keep dust and other particles out. The eyelids act as windscreen wipers, spreading tear fluid with every blink to keep your eyes moist and wash away bacteria.
You blink more than 10, times a day! And if anything gets too close, your eyelids slam shut with amazing speed. How fast does this happen? You bounce your eyes around all the time. The eyes automatically adjust to the movement of your head with great speed and precision. Test it: Keeping your head still, hold up your hand about 30cm away, and quickly move it back and forth.
As fast as your eyes are, your fingers become blurry. Now keep your hand still and move your head back and forth. Amazingly, your fingers stay in focus! Lucky for you, the cameras in your head come with an impressive software package — your brain — that can fix these problems. The brain automatically flips the images from your retinas right side up and combines the images from each eye into a three-dimensional picture.
Your brain makes adjustments for this, too. But sometimes it can be fooled! The cornea helps the eye focus as light makes its way through. It is a very important part of the eye, but you can hardly see it because it's made of clear tissue. Like clear glass, the cornea gives your eye a clear window to view the world through. Behind the cornea are the iris, the pupil, and the anterior chamber.
The iris say: EYE-riss is the colorful part of the eye. When we say a person has blue eyes, we really mean the person has blue irises! The iris has muscles attached to it that change its shape. This allows the iris to control how much light goes through the pupil say: PYOO-pul. The pupil is the black circle in the center of the iris, which is really an opening in the iris, and it lets light enter the eye. To see how this works, use a small flashlight to see how your eyes or a friend's eyes respond to changes in brightness.
The pupils will get smaller when the light shines near them and they'll open wider when the light is gone. The anterior say: AN-teer-ee-ur chamber is the space between the cornea and the iris. This space is filled with a special transparent fluid that nourishes the eye and keeps it healthy.
These next parts are really cool, but you can't see them with just your own eyes! Doctors use special microscopes to look at these inner parts of the eye, such as the lens. After light enters the pupil, it hits the lens. The lens sits behind the iris and is clear and colorless. The lens' job is to focus light rays on the back of the eyeball — a part called the retina say: RET-i-nuh.
The lens works much like the lens of a movie projector at the movies. Next time you sit in the dark theater, look behind you at the stream of light coming from the projection booth. This light goes through a powerful lens, which is focusing the images onto the screen, so you can see the movie clearly. In the eye's case, however, the film screen is your retina.
Your retina is in the very back of the eye. It holds millions of cells that are sensitive to light. The retina takes the light the eye receives and changes it into nerve signals so the brain can understand what the eye is seeing. The lens is suspended in the eye by a bunch of fibers. These fibers are attached to a muscle called the ciliary say: SIL-ee-air-ee body. It has the amazing job of changing the shape of the lens. That's right — the lens actually changes shape right inside your eye!
Try looking away from your computer and focusing on something way across the room. Even though you didn't feel a thing, the shape of your lenses changed. When you look at things up close, the lens becomes thicker to focus the correct image onto the retina. When you look at things far away, the lens becomes thinner. The biggest part of the eye sits behind the lens and is called the vitreous say: VIH-tree-us body. The vitreous body forms two thirds of the eye's volume and gives the eye its shape.
It's filled with a clear, jelly-like material called the vitreous humor. Ever touch toy eyeballs in a store? Sometimes they're kind of squishy — that's because they're made to feel like they're filled with vitreous humor.
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