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Human Eye

Human Eye.

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Human Eye

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  1. Human Eye The eyes are undoubtedly the most sensitive and delicate organs we possess, and perhaps the most amazing. They present us with the window through which we view the world, and are responsible for four fifths of all the information our brain receives – which is probably why we rely on our eyesight more than any other sense.

  2. Eye In Detail

  3. How We See • he images we see are made up of light reflected from the objects we look at. This light enters the eye through the cornea. Because this part of the eye is curved, it bends the light, creating an upside-down image on the retina (this is eventually put the right way up by the brain). • The retina is a complex part of the eye, but only the very back of it is light-sensitive,and is packed with photosensitive cells called rods and cones. These allow us to see images in colour and detail, and to see at night. • The lens focuses the image. It can do this because it is adjustable - using muscles to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain. The lens focuses the image. It can do this because it is adjustable - using muscles to change shape and help us focus on objects at different distances. The automatic focusing of the lens is a reflex response and is not controlled by the brain. • Once the image is clearly focused on the sensitive part of the retina, energy in the light that makes up that image creates an electrical signal. Nerve impulses can then carry information about that image to the brain through the optic nerve.

  4. Common Eye Problems • Short sight (myopia) and long sight (hypermetropia) are common conditions, both caused by the cornea and lens not focusing properly on the retina.

  5. What Is Hypermetropia? In a hypermetropic eye, the light is not bent sufficiently so that it focuses at a point behind the retina. Here a person sees well for distance but near vision is difficult and causes strain. Hence hypermetropic people are called long-sighted.

  6. What Is Myopia? Myopia "shortsightedness“ is a refractive defect of the eye in which collimated light produces image focus in front of the retina when accommodation is relaxed.

  7. Amazing Facts About Eye • We should never put anything in or near our eyes, unless we have a reason to use eye drops. We would only do that if our doctor or parent told us to use them. • Blinking helps to wash tears over our eyeballs. That keeps them clean and moist. Also, if something is about to hit our eye, we will blink automatically. • Our body has some natural protection for our eyes. Our eyelashes help to keep dirt out of our eyes. Our eyebrows are made to keep sweat from running into our eyes. • Our eyes are very important to us, and we must protect them. We don't want dirt, sand, splinters or even fingers to get in our eyes. We don't want our eyes to get scratched or poked. That could damage our sight! • The study of the iris of the eye is called iridology. • The shark cornea has been used in eye surgery, since its cornea is similar to a human cornea. • The number one cause of blindness in adults in the United States is diabetes. • The eyeball of a human weighs approximately 28 grams. • The eye of a human can distinguish 500 shades of the gray.

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