Corrective Lenses

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Corrective Lenses
Catelin Kerstetter Kirk Lunden Andrew Robinson
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Corrective eyeglass lenses are needed when your
eye does not focus the image you are viewing onto
your retina, which includes (nearsightedness)
myopia, farsightedness (hyperopia), and an
astigmatism. Think of a prism when trying to
understand the way light bends through the curved
surface of a lens. The light is bent through the
portion of the prism that is thickest. When
making a minus lens, the base is the thickest
part, and the apex the thinnest part. As a
result the light stretches away from the apex,
and thus the vocal point is moved forward. In a
plus lens, the opposite happens and the light is
refracted toward the center, as the vocal point
moves further away. In a minus lens, the
stronger the lens is the further away the vocal
point will be, and in a plus lens the stronger it
is, the closer the vocal point is. Having the
correct type and power of a lens makes
adjustments to the focal point so the poor vision
is corrected.
Concept
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Discovery

• The original inventor of eyeglasses is unknown.
• However, the were invented between 1268 and 1289.
• Quartz was used at first for lenses, until glass
  was later used.
• The quartz was set in metal or bone.
• Four hundred years passed before the pieces that
  sit above ones ears were added to hold the
  glasses up.
• The bifocals were later invented in the 1780s by
  Benjamin Franklin.

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Life Before Lenses

• Until the invention of eyeglasses, there was no
  cure for vision loss.
• It is believed that early Egyptians attempted
  surgical vision correction, but were
  unsuccessful. It appears that the only successful
  account of vision correction can be found in the
  Bible. Mark 828 tells the story of Jesus
  restoring vision to a blind man.

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Life Before Lenses
Early Egyptian Eye Surgery
Jesus Heals a Blind Man
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Superstitions

• There were many superstitions that supposedly
  helped stave off vision loss including
• Wearing gold earrings
• Burning the head of a cat and blowing the ashes
  into blind eyes
• Licking the eyes of frogs

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Life Before Lenses

• Those who did not have access to a divine power
  and were stricken with poor vision were not able
  to perform most jobs. They were driven to a life
  of vagrancy and begging.

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Cultural Impact

• Lenses have become an integral part of society
• From glasses to binoculars to cameras, people
  interact with lenses daily
• The advancements in lenses has allowed humans to
  make discoveries beyond their limits of knowledge

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Glasses

• Glasses, and by extension the lenses in them, are
  prosthetics for human eyes.
• Simple tasks such as reading and communicating
  would be more difficult or impossible without
  lenses
• Glasses are shaped in ovals to allow the optical
  center to be over the eyeball

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Telescopes

• The lenses that make up a telescope allowed
  astronomers like Galileo to find the remaining
  planets in our Solar System
• The Hubble Space Telescope has granted us a look
  into the deepest reaches of space and clues to
  the questions of the universe

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Radio Dishes

• Dielectric lenses are used in the construction of
  massive radio dishes
• These dishes, though not directly used for
  seeing, have been used in radio telescopes that
  can reach further into space than conventional
  lenses and have helped prove the existence of
  quasars

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Other lenses

• Convex lenses can be used to focus energy into a
  focal point to heat an inflammable object and
  melt it
• A single convex lens with a handle is the classic
  magnifying glass
• Recently, large lenses have been used in the
  collection of solar energy into small
  photovoltaic cells

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Works Cited

• http//science.howstuffworks.com/lens3.htm
• http//science.howstuffworks.com/lens2.htm
• http//amos.indiana.edu/library/scripts/eyeglasses
  .html
• "Superstitions." Planet of the Blind. 26 Sept.
  2006. 25 Sept. 2008 lthttp//kuusisto.typepad.com/
  planet_of_the_blind/2006/09/superstitions.htmlgt.