NIGHT VISION ORIENTATION

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Anatomy of the Eye

• Cornea - Transparent tissue located over the
  
  
  
  
  front of the eye.
• Iris - Round, pigmented (colored) membrane
  surrounding the pupil.
• Pupil - Opening in the center of the iris.
• NOTE Pupil size.

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Anatomy of the Eye (cont.)

• Lens - Positioned behind the pupil and directs
  light.
• Retina - Thin multi-layered membrane which covers
  most of the posterior compartment of the eye.
  
  
  

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ANATOMY AND PHYSIOLOGY OF THE HUMAN EYE
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PHOTORECEPTOR CELLSCONE CELLS (Day Vision)

• Cone Cells Used during periods of bright light
  exposure and identifies colors.
• Seven million contained in fovea and parafoveal
  regions of retina.
• Sharp visual acuity and color sense.
• 11 ratio of cone cells to neuron cells.

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PHOTORECEPTOR CELLSROD CELLS (Night Vision)

• Rod Cells Used during periods of low ambient
  lighting and darkness.
• Identifies outlines of shapes and objects.
• Decreased color sense and visual acuity.
• 120 million rod cells (periphery of retina).
• 101 to 10,0001 rod cells to neuron cells.

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PHOTORECEPTORS
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RETINAL BLIND SPOTS

• The Day (Physiological) Blind Spot
• Results from the position of the Optic disc on
  the retina.
• Located 15 degrees from fovea.
• Photoreceptor cells none.
• Covers an area of 5.5 to 7.5 degrees.

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BLIND SPOTS
Day or Physiological Blind Spot
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X
X
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RETINAL BLIND SPOTS

• Night Blind Spot
• Photoreceptor cells
• Occurs when the cones in the fovea and
  parafovea regions are non effective due to loss
  of ambient light.
• Encompasses an area of 5.5 to 10 degrees wide in
  the center of the visual field.

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Visual Deficiencies
Presbyopia - (aging) Hardening of lens loss of
elasticity
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ASTIGMATISM
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BLIND SPOT
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Types of vision

• Photopic vision (DAY)
• Mesopic vision (Dawn/Dusk)
• Scotopic vision (NIGHT)

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Photopic vision

• Day light or bright light
• Central vision
• Color sense and sharpness
• Best visual acuity

Photopic vision
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Mesopic vision

• Dawn, dusk, and full moonlight
• Parafoveal regions (rods and cones)
• Degraded visual acuity and color sense

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Scotopic vision

• Night vision (partial moon and star light)
• Peripheral vision (rods only)
• Acuity degraded (20/200) to silhouette
  recognition
• Color blind -black, gray, and white
• Off center viewing to compensate blind spot
• Ten degree circular overlap of scanning sectors

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DARK ADAPTATION FACTORS

• Photosensitivity of the eye.
• Bleaching effect of rods. (Rhodpsin)
• Nutrition.

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Limitations of Night Vision.

• Depth perception (safe landings).
• Visual acuity (obstacle identification) .
• Blind spots.
• Dark adaptation (time factor).
• Color vision.

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Night Flight Techniques

• Preflight ALL aircraft lighting
• Carry flashlight, finger light or lip light
• Use red or green/blue lighting as supplemental
  lighting
• Pre-position landing light
• Conduct blind cockpit drills
• Determine and familiarize with destination
  lighting (PCL)
• Dark Adapt
• Dim Cockpit lights
• Avoid extremely bright lit areas
• Dont stare at bright lights
• Reduce speed during approaches

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Night Flight Techniques

• Avoid flight directly into sunset or rise or
  rising/falling moon
• Be aware that Mesopic times are most dangerous
  due to false sense of acuity

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Search/Aquire/Identify

• Scanning Techniques
• Off-center viewing.
• Shape and Silhouette

SEE ME
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QUESTIONS?