Eye Spy

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Eye Spy

• The Wonders of Human Vision

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The Human Eye
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The Human Eye

• Cornea transparent outer layer
• Does most of the bending/focusing of the
  light as it enters the eye
• Can be transplanted relatively easily
• Subject to injury doesnt heal well due to poor
  blood circulation

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The Human Eye

• Iris colored part
• This muscle controls the size of the pupil
• Only pigment present is melanin (brown) hazel
  and green eyes have less melanin, blue has very
  little melanin the bluish shades are due to
  interference between layers of protein and tend
  to be more changeable than brown eyes

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The Human Eye

• Pupil
• This opening controls the amount
  of light that enters the eye it gets smaller
  in bright light
• Some injuries/chemicals cause loss of control of
  this leads to pinpoint or wide open pupils

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The Human Eye

• Lens
• Firm gel (feels like cartilage)
  muscles control exact shape
• Allows for fine focusing
• Try to adjust your focus without blinking
• Side view Near Far

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The Human Eye

• Aqueous and vitreous humors
• Soft space-filling gels maintain shape of the eye
• Too much pressure here is called glaucoma
• Remember the air puff test at the eye doctor?

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The Human Eye

• Retina tissue all over the back of the
  eye
• Light sensing molecules called rods and cones are
  located there (more on these later)
• Snow blindness is sunburn of the retina
• Middle-back area is very sensitive the macula
  (have you heard of macular degeneration?)

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The Human Eye

• Optic nerve collects
• input from the retina and carries
  the nerve impulses to the brain
• No detector molecules there, so its a blind spot
• Make these marks on your paper about 2 inches
  apart (test left eye first)

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Rods and Cones

• These light sensitive molecules are named for
  their distinctive shapes

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Rods

• Rods sense the presence of light
  (black/gray/white) no color perception
• VERY sensitive and can detect even dim light
  (Poor night vision? eat more carrots!)
• Peripheral vision is mostly from rods, since
  theyre around the edges of the retina
• Peripheral and dim light vision is mostly
  colorblind

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Cones

• Three types in humans, called RED, GREEN, and
  BLUE
• Which cones fire with which strength determines
  the color the brain interprets
• Cones are concentrated in the macula, the center
  of the retina
• Theyre not very sensitive, operating in bright
  light only

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Rods and Cones
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Rods and Cones

• Have you ever seen a shooting star?
• Do we all see colors the same way? No way of
  knowing.
• Ever tried to pick out the right color socks in
  dim light?

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Are you color blind?

• An individual with missing or damaged cones is
  considered color blind, because they dont
  differentiate between colors very well
• Sex-linked trait genes for cones are on the X
  chromosome healthy cones are dominant
• Males one X chromosome from mom
• Females two Xs, one from each parent

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Take the test!

• Number your paper from 1 to 12.
• Write down the numbers you see on the screen as
  they appear, in order.
• Well go over the answers afterwards.
• Did you study for this?

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