Amblyopia: New Findings on the Most Common Developmental Visual

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• Amblyopia New Findings on the Most Common
  Developmental Visual
• Disorder
• Dr. Debbie Giaschi
• University of British Columbia

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Amblyopia (lazy eye)

• impaired vision in one eye that cannot be
  corrected with glasses
• caused by deprivation of normal vision for a
  prolonged period during development
• usually strabismus (eye misalignment),
  anisometropia (optical error difference) or both
• affects 2.5 of general population
• often reversible through occlusion of good
  (fellow) eye before 8 years of age
• preschool vision screening important

• treatment failures may occur because occlusion
  treats only some of the deficits

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Classical form perception deficits in amblyopia

• recognition acuity

resolution acuity
Vernier acuity
visual distortions
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Children with amblyopia have difficulty seeing
the flying bird, even in the fellow eye that has
normal visual acuity (Giaschi et al., 1992)
Surprising motion perception deficits in
amblyopia
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The visual pathways
motion
posterior parietal
V5
V1
V1
inferior temporal
V4
form
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Study 1 Functional MRI(with Cindy Ho)
Background

• Motion perception is hypothesized to involve both
  low-level and high-level cortical mechanisms,
  depending on the stimulus

Goal

• To establish the existence of low- and high-level
  mechanisms for motion perception
• To determine the cortical basis for the deficit
  in amblyopia

Progress

• 4/8 controls and 6/8 children with amblyopia
  tested

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Study 1 Methods
confirmed
confirmed
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Study 1 results (controls)
large vs. small dots
low vs. high density

• blue more activation with low-level stimuli
  (small dots or high density)
• red more activation with high-level stimuli
  (large dots or low density)

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Study 1 results (amblyopia)
No regions activated more by high-level motion
Less activation, relative to controls, by
low-level motion
blue more activation with low-level stimuli
(small dots or high density)
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Study 2 Residual Binocular Vision (with Laurie
Wilcox)
Background

• Motion deficits greater in amblyopic children
  with residual coarse stereopsis
• Not measured clinically implications for
  treatment success.

Goal

• To develop a child-friendly computer measure of
  coarse stereopsis
• To determine performance limits in children with
  typical visual development
• To determine if our new task reveals residual
  binocular vision in amblyopia that is missed by
  standard clinical tests

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Study 2 Methods
Wilcox/Giaschi coarse stereo test
Clinical stereo test
Coarse stereopsis double vision perceive depth
Fine stereopsis single vision perceive depth
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If the top Pokemon is in front
You press the blue button.
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If the bottom Pokemon is in front
You press the yellow button.
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Study 3 Occlusion therapy (with David Regan)
Background

• Amblyopia is treated by occluding the fellow eye
  with a patch
• Visual acuity may not improve improvement may be
  temporary

Goal

• To determine the effect of occlusion therapy on
  motion perception in children with amblyopia
• To determine if coarse stereopsis predicts
  treatment outcomes

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The Team

• fMRI
• Cindy Ho
• Bosco Lee
• UBC High Field MRI Centre
• Jody Culham
• (U Western Ontario)

• Residual binocular vision
• Catherine Boden
• Jane Wang
• Laurie Wilcox (York U)
• Kevin Mackenzie (York U)
• Alexia Casalinuovo
• (York U)

Thank you