Today’s Wonder of the Day was inspired by Alix from Lincoln. Alix Wonders, “How do our eyes make us see?” Thanks for WONDERing with us, Alix!
Many kids play games with their friends and family members to pass the time. Have you ever played license plate bingo? It can be a challenge to spot as many different states' license plates as possible during your journey.
Or maybe you prefer to play "I Spy." You might say, "I spy with my little eye…something red!" Then it's up to your friends and family members to guess whether you're talking about the stop sign, the fire truck, the cool little red Corvette, or something else entirely.
Playing "I Spy" makes you think about how incredible your eyes are. They can look around in all directions, focusing on things near and far in mere milliseconds. They're on the job, helping you experience the world around you from the time you wake up until you go to sleep.
But exactly how do they make you see? What parts of the eye do what jobs? How are they able to do things the world's most technologically-advanced cameras can't do?
When light bounces off an object in your field of vision and enters the eye, it first penetrates a thin layer of tears that cover the eye's clear outer layer called the cornea. The cornea helps to focus the light as it enters the eye.
On the other side of the cornea is a liquid substance called the aqueous humor. This fluid maintains the proper pressure inside the eye. After the aqueous humor, light passes through the pupil, which is the round opening in the iris that you otherwise know as the colored part of your eye.
The iris changes the size of the pupil to adjust the amount of light it lets in. When it's dark, the iris makes the pupil larger to let as much light as possible in to help you see. When it's bright out, though, the iris makes the pupil smaller to reduce the amount of light entering to prevent damage to the eye.
After light passes through the pupil, it moves through the lens. The lens focuses the light onto the retina, which is the back surface of the eye. The retina is kind of like the screen in a movie theater or the film in a camera.
Ligaments inside the eye change the shape of the lens to keep light focused properly on the retina. Sometimes, however, our eyes need extra help. That's why some people wear glasses that help to bend light so that it's perfectly focused on the retina.
When light hits the retina, it activates photoreceptors called rods and cones. These special nerve cells convert light into electrochemical signals. Those electrical impulses then travel to the brain along the optic nerve.
The image the brain receives from the eyes is actually upside-down. The brain turns the image around as it processes it, so that we see things as they really are.
Although it may seem like a simple process, the coordination of all the different parts of the eye along with the optic nerve and the brain requires countless adjustments that happen in milliseconds as we look around.
If you think about all that is happening as you look at something as small as a human hair and then look into the sky at something as large and far away as the Moon, you'll realize what amazing organs your eyes really are!