The Five Senses: Sight

Your eyes take in tons of information about the world around you — shapes, colors, movements, and more. Then they send the information to your brain for processing so the brain knows what's going on outside of your body.

The eye is about as big as a ping-pong ball and sits in a little hollow area in the skull called eye socket. The eyelid protects the front part of the eye and helps keep the eye clean and moist by opening and shutting several times a minute. This is called blinking. The eyelid also has great reflexes (automatic body responses) that protect the eye. When you step into bright light, for example, the eyelids squeeze together tightly to protect your eyes until they can adjust to the light. The eyelashes work with the eyelids to keep dirt and other unwanted stuff out of your eyes.

The white part of the eyeball is called the sclera, which is made of a tough material that covers most of the eyeball. You can see tiny blood vessels here as well.

The cornea is in front of the colored part of the eye. The cornea helps the eye focus as light makes its way through. Like clear glass, the cornea gives your eye a clear window to view the world through.

The iris 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 

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.  The pupils will get smaller when a lot of light shines near them and they'll open wider when there is little light.  

After light enters the pupil, it hits the lens, which is clear and colourless. The lens' job is to focus light rays on the back of the eyeball — a part called the retina.

The lens actually changes shape inside your eye: when you look at things up close, the lens becomes thicker to focus the correct image onto the retina; but when you look at things far away, the lens becomes thinner.

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 retina uses special cells called rods and cones to process light:

- Rods see in black, white, and shades of gray and tell us the form or shape that something has. Rods can't tell the difference between colors, but they are super-sensitive, allowing us to see when it's very dark.

- Cones see color and they need more light than rods to work well. Cones are most helpful in normal or bright light. 

Sometimes someone's eyeball shape makes it difficult for the cornea, lens, and retina to work perfectly as a team. When this happens, some of what the person sees will be out of focus.To correct this blurry vision, many people wear glasses. Glasses help the eyes focus images correctly on the retina and allow someone to see clearly. As adults get older, their eyes lose the ability to focus well and they often need glasses to see things up close or far away. 

Think of the optic nerve as the great messenger in the back of your eye. The rods and cones of the retina change the colors and shapes you see into millions of nerve messages. Then, the optic nerve carries those messages from the eye to the brain, which interprets the information.

Above the outer corner of each eye are the lacrimal glands, which make tears. Every time you blink your eye, a tiny bit of tear fluid comes out of your upper eyelid. It helps wash away germs, dust, or other particles that don't belong in your eye. Tears also keep your eye from drying out. Then the fluid drains out of your eye by going into the lacrimal duct (this is also called the tear duct). Your eyes sometimes make more tear fluid than normal to protect themselves. This may have happened to you if you've been poked in the eye, if you've been in a dusty or smoking area, or if you've been near someone who's cutting onions. And how about the last time you felt sad, scared, or upset? Your eyes got a message from your brain to make you cry, and the lacrimal glands made many, many tears.

Your eyes do some great things for you, so take these steps to protect them:

• Wear protective goggles in classes where debris or chemicals could go flying, such as wood shop, metal shop, science lab, or art.

• Wear eye protection when playing  hockey, skiing, or other sports that could injure your eyes.

• Wear sunglasses. Too much light can damage your eyes and cause vision problems later in life. For instance, a lens could get cloudy, causing a  cataract, which prevents light from reaching the retina and makes it difficult to see.
• Keep a balanced diet, which includes vitamin A (carrots).
• Rest your eyes regularly when you read, watch TV or use a computer.
• Go to the ophthalmologist regularly to have your eyesight checked.

(Information taken  and adapted from: https://kidshealth.org)

Here you have some videos to learn more about your sight: 

The eye song

How good are your eyes? A quick test