The Eyes Have It!

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The Eyes Have It!
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Light, Lens, Action!

• From the moment you wake up in the morning to the
  time you go to sleep at night, your eyes are
  acting like a video camera. Everything you look
  at is then sent to your brain for processing and
  storage much like a video cassette. This is a
  very simplified explanation, but as you read on,
  you will discover why the sense of sight is
  actually considered the most complex of the five
  senses.

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How the Eye Works

• Take a moment to locate an object around you. Do
  you know how you are able to see it? Would you
  believe that what you are actually seeing are
  beams of light bouncing off of the object and
  into your eyes? It is hard to believe, but it is
  true.

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How the Eye Works continued

• Your lens in your eyes change size all the time.
  When you look at objects real close up, the lens
  gets thicker. If you look at objects far away, it
  gets thinner. It does this to help you focus the
  correct image on the retina.
• After light passes through the lens it shines
  through the vitreous humor to the back of the eye
  where it hits the retina. The retina takes the
  light and changes it into nerve impulse so the
  brain can understand what the eye sees. It sends
  the message to the brain by way of the optic
  nerve.

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Parts of the Eye

• The light rays enter the eye through the cornea,
  which is a thick, transparent protective layer on
  the surface of your eye. Then the light rays pass
  through the pupil (the dark circle in the center
  of your eye) and into the lens.

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Function of the eye parts

• Cornea The cornea is a clear white covering over
  the outside of the eye. It helps the eye focus
  like a lens on a camera.
• Iris The iris is the part of your eye that has
  color. It gets bigger and smaller to let in
  different amounts of light.
• Pupil Black opening in the middle of the eye.
  Light comes through this opening.

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Function of the ey

• Lens The lens bends light. This helps the eye
  see close up and far away things.
• Vitreous Humor The vitreous humor is clear
  water-like substance in the back of your eye.
• Retina The retina has nerve cells called rods
  and cones that detect light. It is in the back of
  your eye.
• Optic Nerve The optic nerve carries electrical
  signals from your retina to your brain so you can
  see.

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Flipped Image

• When you see images, they turn upside down when
  they hit the retina. So your brain sees
  everything in the world upside down. Your brain
  basically flips everything around so it is right
  side up again.

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Protection Because the eye is such an important
and complex part of our body, we have many
features which protect the eye.

• The eyebrows are the strips of hair above your
  eyes which prevent sweat from running into them.
• Eyelashes help keep the eye clean by collecting
  small dirt and dust particles floating through
  the air. The eyelashes also protect the eye from
  the sun's and other light's glare. The eyelids
  sweep dirt from the surface of the eye. The
  eyelid also protects the eye from injury.
• Tears are sterile drops of clean water which
  constantly bathe the front of the eye, keeping it
  clean and moist.

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Imperfect EyesightNearsighted and Farsighted

• Not all people have perfect vision.
• People who can see things up close, but not far
  away are considered to be nearsighted. This
  happens when the light entering the eye focuses
  on a point in front of the retina.

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• On the other hand, people who can see far away
  objects but not those that are up close are
  farsighted. Farsightedness occurs when the light
  that enters the eye focuses on a point behind the
  retina.

Whether a person is nearsighted or farsighted,
glasses or contacts help that person to see
things much more clearly!
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Eye Fun Facts

• Most people blink every 2-10 seconds.Each time
  you blink, you shut your eyes for 0.3 seconds,
  which means your eyes are closed at least 30
  minutes a day just from blinking.
• If you only had one eye, everything would appear
  two-dimensional. (This does not work just by
  closing one eye.)?
• Owls can see a mouse moving over 150 feet away
  with light no brighter than a candle.
• The reason cat's and dog's eyes glow at night is
  because of silver mirrors in the back of their
  eyes called the tapetum. This makes it easier for
  them to see at night.
• An ostrich has eyes that are two inches across.
  Each eye weighs more than their brain.
• A chameleon's eyes can look in opposite
  directions at the same time.
• A newborn baby sees the world upside down because
  it takes some time for the baby's brain to learn
  to turn the picture right-side up.
• One in every twelve males is color blind