THE EYE

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					         THE EYE
         Ch. 14 Carltons

Appendix #1 State Fluoro Syllabus
                       pg 77
Early Fluoroscopy
• FOVEA CENTRALIS
• CENTRAL PART OF
  RETINA
• CONES TIGHTLY
  PACKED
• REMAINDER –
  CONES DIMISH =
  MORE RODS
           Visual Physiology
       2 types of light receptors
    RODS            CONES
• NIGHT VISION      •   DAYLIGHT
• SCOTOPIC          •   PHOTOPIC
• PERCEIVE GRAYS    •   PERCIEVE COLOR
• PERIPHERY OF      •   CENTER OF RETINA
  RETINA = DIM      •   BETTER VISUAL
  OBJECTS SEEN          ACUITY
  BETTER – 1000 X
  MORE SENSITIVE
                    New II much brighter
• 30 min dark
  adaptation
Red goggles for dark adaptation
            Human Vision
• Light passes through the lens, where light
  is focused onto the retina.
• Between the cornea and the lens is the
  iris, which acts like a camera diaphragm =
  controls the amount of light admitted into
  the eye
          VISUAL ACUITY
• ABILITY TO PERCEIVE FINE DETAILS
• INTEGRATION TIME = 0.2 SEC (how
  long it takes to identify something)

• Photopic acuity is 10 x greater than
  scotopic

• Normal viewing distance 12 – 15 inches
                      VISION
•   EYE SEES 32 SHADES OF GRAY
•   COMPUTER 256 – 8 bit to 1024 12 bit depth SHADES
•   REGARDING CINE:
•   32 FRAMES SOME FLICKER (OLD MOVIES)
•   60 FRAMES = NO FLICKER
   The Eyes & Radiation Dose
• What is the allowable annual limit for the
  eyes? _______________________



• What problems with the eyes were seen
  with early Radiologists?
   The Eyes & Radiation Dose
• Cataracts (cataractogenic effects)
                           P49 RAD – RHB SYLLABUS

• Formation of Cataracts – dose of several 110
  rads
• Fibers in lens of eye are specialized to transmit
  light
• Damage to these (particularly to the developing
  immature cells – can result in cataracts)

				
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