Eyes: Seeing The Light (1981)

[Music] This is a film about two of your most valuable possessions, your eyes. Your eyes are your most important sense organs. Just think of all the things your eyes do for you. They enable you to gain knowledge from the world around you. to view the wonders of nature and to enjoy all kinds of entertainment. Your eyes work together with your muscles to help you develop skill in sports and games. Your eyes help keep you safe, too. They enable you to watch out for traffic and to see signs that warn of danger. While it's easy to see why your eyes are so important, you may be in the dark as to how they work and how to care for them. So, let's shed some light on the subject. >> Isn't that better? >> Yes. Thank you. [Music] [Applause] [Music] Each of your eyes is a ball-shaped organ about 1 in across and fits into a hollow pocket in In the skull, the eyeball has six muscles attached to it. What do you suppose they do? Right. They move your eyes back and forth, up and down, anywhere you want them to look. The eye is protected by pads of fat that cushion the eyeball from shock. This fat and the bones of the cheek and forehead protect the eye on all sides except the front. The front part of the eye is protected by the eyelids. They act as doors and shut quick as a wink when anything flies toward the eye. Eyelashes and eyebrows also protect the eye. They serve as protective screens to help keep out dust and sweat. Tears give protection, too. This slightly salty fluid is produced by glands behind the upper eyelid. When you blink, the eyelids spread the tears over the eye to keep it moist and clean. The tears drain into the nose through two small openings or ducts at the inner corners of each eye. As you know, your eyes must have light in order to see things. Light is a form of energy and it travels as rays. Some of the things you see give off their own light rays such as a light bulb, a fire or the sun. However, you see most things by reflected light. that is light rays that bounce off objects sent into your eyes. It's the job of your eyes to change light rays into sight messages and to send these messages to the vision center in each side of your brain. Then your brain tells you what you see. To better understand how your eyes work, let's look at the inner parts of the eye and find out what they do. The eyeball itself is made up of three layers of tissue. An outer layer called the scara, a middle layer, and the retina, an inner lining sensitive to light. The center of the eyeball is filled with a clear jelly-like substance called vitrius humor. It helps the eyeball keep its round shape. The scara or outer layer of the eyeball surface is the tough white tissue you call the whites of your eyes. At the front of the eye, the scara bulges out and becomes as clear as glass. This clear bowl-shaped part is called the cornea. It acts as a window to let light enter the eye. Behind the cornea is a small space filled with a clear watery liquid called the aqueous humor. It works with the cornea to bend light rays inward as they enter the eye. The middle layer of the eyeball is made up of three parts. The largest part is the koid. It's full of tiny blood vessels which nourish the eye. The second part of this layer is the iris. It's the colored part of the eye just behind the cornea. The black area in the middle of the iris is called the pupil. It's the opening that lets light inside the eye. The iris has two sets of muscles which change the size of the pupil. The iris makes the pupil small in bright light and large in dim light. The third part of the eyes's middle layer is the siliary muscle. Small fibers connect this muscle to the lens of the eye which is located just behind the pupil. The lens of the eye does the same job as the lens in the camera. It focuses light rays so that the pictures you see are sharp and clear. But the lens of the eye is more wonderful than that of any camera. That's because the eyes lens can change its shape. The siliary muscle makes the lens thinner to focus light rays from distant objects. It makes the lens thicker to focus light from objects nearby. The lens changes its shape so quickly that you can look at an object a few inches away 1 second and an object miles away a split second later and both objects will be in focus. The lens of the eye focuses light rays on the retina, the third layer of the eyeball. The retina is a film-like tissue lined with two kinds of light sensitive cells called rods and cones. The long thin rods work best in dim light or at night. Rods cannot recognize colors. They are used when you see black and white or shades of gray. The cones are stimulated by bright light. They enable you to see things in color. Now that you know the parts of the eye, let's look at the process of seeing from start to finish. Reflected light rays strike the eye. As the rays pass through the cornea and the aquous humor, they are bent inward through the pupil and are bent some more as they are focused by the lens. The rays then travel through the vitrius humor until they strike the retina where they form an upside down image. On the retina, the light rays form tiny dots of light on the cones or rods. The cones or rods cause the light energy to change into electrical signals. The signals travel along nerve fibers that come together to form the optic nerve. The electrical signals then move along the optic nerve to the vision center in each side of the brain. There the brain blends all the signals together to form a right side up picture of what the eye sees. >> DVR >> HBC. >> As you learned earlier, one of the wonderful things about the eye is its ability to focus on things near and far. >> NHZ. Would you read these lighted letters for me, Jack, please? But some people have eyes that don't focus as they should. >> I can't tell that one. >> They may have eyeballs that are the wrong shape. >> If the eyeball is too long, the lens focuses light in front of the retina. This defect is called nearsightedness because only things very near the eye are in focus. If the eyeball is too short, the lens focuses light beyond the retina. This defect is known as far-sightedness because only things far from the eye are clear and in focus. >> Going to uh examine your eyes here now and we're going to find the latest correction that we need to get you to see perfectly. >> Fortunately, both of these common eye defects can be corrected by glasses or contact lenses that are prescribed by an eye doctor. is now the picture at the bottom is very blurry. When the top picture is equally blurry with the one on the bottom, say stop, please. >> It's a good idea to have an eye examination periodically or every few years, even if you're not having trouble seeing. Such an examination may reveal eye defects or diseases in their early stages. Some signs of eye disease include unusual redness, blurred vision, excess watering, pain, irritation, or itching of the eye. You should see an eye doctor if you ever have these symptoms for more than a day or two. While some eye problems can be corrected, others can be prevented entirely by giving your eyes the care and protection they need. For example, you can avoid eye strain by giving your eyes good lighting when you read. Make sure the light shines down on your book and not into your eyes. When you must read for a long time, rest your eyes once in a while by looking at a distant object. This helps relax tired eye muscles. It's fun to watch television, but you can strain your eyes by watching in a dark room or by sitting too close. >> Girls, I've asked you not to sit so close to the TV. It's bad for your eyes. Sit back here a little bit. Okay. So, always have some light in the room and sit across the room from the screen. Because the eyes are such important, delicate organs, they should be protected from accidents and injuries. >> Be very careful with sharp pointed objects such as darts and arrows. Keep spectators well back from the target. Even pencils and sticks can be dangerous. >> Come on, let's go out and play. >> Okay. >> Don't ever run with a pencil or other sharp object in your hand. Be careful also with fireworks, BB guns, slingshots, and peashooters. If used carelessly, all these things can cause serious eye damage or blindness. Many chemicals can also injure the eyes. So cleaning solutions, household ammonia, and other products should be used with extreme care. If any chemical ever gets in your eye, wash it out immediately with lots of running water. Then get medical help. Very bright light can cause eye damage, too, and sometimes partial blindness. That's why you should never look directly at the sun or any other brilliant light. Sometimes the eyes need special protection at work and at play. During sports and games, wear the proper safety equipment. [Music] >> And if you wear glasses, make sure the lenses are made from shatterproof glass or plastic. It's especially important to protect your eyes from flying chips of wood or metal. So, always wear protective glasses to keep such particles out of your eyes. If you ever do get a speck of something in your eye, don't rub your eye. You might scratch the eyeball. Your tears may wash out the speck. If they don't, you can flush the eye with water. or use the corner of a clean handkerchief to try to remove the particle. If you can't get it out, see your doctor. Your eyes are among your most valuable possessions. Now that you know more about them, perhaps you will appreciate them a little more every time you see the light. >> Ah, now I see. [Music]