EXAMINATION

VISUAL ACUITY TESTING

• Auditory-visual-verbal match is "not magical"
  • It is a learned response, i.e. a developmental issue

VISUAL ACUITY TESTING (auditory loop)

• Recognition of sound (instructions)
• Attention allocation
• Orientation
• Discrimination of sounds
• Recognition of words
• Interpretation
• Auditory - visual integration

VISUAL ACUITY TESTING (visual loop)

• Finding the target
• Oculomotor response (fixation)
• Discrimination
• Interpretation (memory, meaning)
• Visual - verbal match

VISUAL ACUITY TESTING (verbal loop)

• Oral - motor programming
• Speech
• Feedback

EXAMINATION ISSUES:

"THE PSYCHOPHYSICS PROBLEM"

• Attention allocation
• Sustaining of attention
• "testability vs. validity"
  • Clinical compromises
  • Trade-offs
    • e.g. comparisons to adult-like Snellen
  • Validity
    • Clinical standards are:
      • Snellen
      • Landolt C
      • Tumbling E
    • All others may be less valid

• Probability "demands" - the need for validity, i.e. proper number of samples
• Expeditious "demands" - the need to test quickly
• 2 alternatives (e.g. Broken Wheel test)
  • 4 of 4 consecutive correct
  • or 5 of 6
• 4 alternatives (e.g. tumbling E)
  • 3 consecutive (or 2!)

   

• Crowding effects
  • Exaggerated in younger children
  • Single vs multiple displays
• Testing distance (20 feet vs. 10 feet)
• Near vs. distance
  • young children perform better at nearpoint than at distance

• The language barrier
• Developmental level - i.e the need to test at the child's developmental level
• Alternative testing methods
  • Non-verbal
  • Pointing
  • Looking