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Strab/Amblyopia > Packet 2 Amblyopia > Flashcards

Packet 2 Amblyopia Flashcards

1
Q

4 classifications of Amblyopia

A
  1. strabismic
  2. anisometropic
  3. isoametropic
  4. deprivation (image degradation)
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2
Q

how does strabismic occur

A

foveal line of sight fails to intersect object of fixation

-confusion and diplopia lead to suppression and then cortical spatial changes

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3
Q

1/3 of amblyopia in clinics is

A

anisometropic amblyopia

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4
Q

some facts for anisometropic amblyopia

A
  • dissimilar retinal image clarity, contrast, and size (vs. form)
  • unequal input -> ABI -> suppression
  • eye with higher ametropia becomes amblyopic
  • always unilateral
  • as aniso increases, generally more severe amblyopia
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5
Q

what are some necessary characteristics of strabismus

A
  • frequency
  • laterality
  • fixation distance
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6
Q

is there a relationship between depth of amblyopia and size of strab?

A

no relationship

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7
Q

100% of people had amblyopia when their hyperopia was greater than

A

3.50 D

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8
Q

100% of people had amblyopia when their myopia is greater than

A

6.50 D

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9
Q

50% had amblyopia when their hyperopia is greater than

A

2.50 D

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10
Q

50% had amblyopia when their myopia was greater than

A

4.50 D

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11
Q

what are some characteristics of isometropia amblyopia

A
  • from uncorrected high bilateral refractive error
  • ret images have equal clarity/ size but blurred
  • bilaterally reduced VA (same +/- one line)
  • BCVA usually 20/30- 20/60 and similar b/w eyes
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12
Q

amount of hyperopic aniso that is amblyogenic

A

> or = 1.00 D

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13
Q

amount of myopia aniso that is amblyogenic

A

> or = 3.00 D

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14
Q

amount of astigmatism aniso that is amblyogenic

A

> or = 1.50D

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15
Q

amount of isometropic hyperopia that is amblyogenic

A

> or = 4.00 D

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16
Q

amount of isometropic myopia that is amblyogenic

A

> or = 6.00 D

17
Q

amount of isometropic astigmatism that is amblyogenic

A

> or = 2.00 D

18
Q

what are some things that can cause deprivation amblyopia

A
  • any physical obstruction to line of site:

- visual axis media opacity (like a cataract), significant ptosis, prolonged occlusion

19
Q

what are some characteristics of deprivation amblyopia?

A
  • unilateral or bilateral (unilateral is worse)
  • VA loss often severe (>20/200 typically)
  • less common but hard to treat
20
Q

what are the 2 amblyogenic mechanisms

A
  1. form deprivation

2. abnormal binocular interaction

21
Q

what is form deprivation mechanism?

A
  • inadequate stimulation of fovea
  • lack of clear image- neural connections for form/shape not stimulated
  • primary effect is cortical, basic retinal receptor processes normal
  • spatial frequency channels present, but require higher contrast to be activated
22
Q

what is abnormal binocular interaction mechanism?

A
  • ABI caused by unequal or conflicting input to 2 eyes

- competitive, inhibitory effect leading to suppression

23
Q

what mechanism for strabismus?

A

ABI

24
Q

what mechanism for anisometropia?

A

both ABI and form deprivation

25
Q

what mechanism for isoametropia?

A

form deprivation

26
Q

what mechanism for deprivation (unilateral)?

A

ABI and form deprivation

27
Q

what mechanism for deprivation (bilateral)?

A

form deprivation

28
Q

in amblyopia, when is the most critical period

A

most sensitive birth to 2-3 years, then decreased until about 6 years

29
Q

which one is more powerful: ABI or form deprivation alone

A

ABI

30
Q

cut off for shallow amblyopia

A

20/20 - 20/32

31
Q

cut off for moderate amblyopia

A

20/40 - 20/80

32
Q

cut off for deep/severe amblyopia

A

20/100 or worse

33
Q

amblyopic eye behaviors

A
  • response slow and irregular
  • wide range of acuity errors
  • letters read out of order or skipped
  • miscalls not necessarily confusion letters
  • letters on ends easier than in middle
  • isolated letter > single ling > full chart
  • variability makes repeated testing poor
34
Q

amblyopic eye defects: behavioral responses related to:

A
  • contour interaction effects
  • spatial distortion and uncertainty
  • reduced contrast sensitivity function
  • eccentric fixation
  • reduced accommodation
  • poor saccades
  • fixation instability
35
Q

some characteristics of ETDRS charts

A
  • 10 sloan letters
  • equal number of letters per line
  • logMAR progression (geometric progression of letter size)
  • improved testing for worse VA levels
  • standardized contour interaction effects
36
Q

how do you measure VAs in people with latent nystagmus?

A
  • high plus (like >+5.00) over fellow eye

- polarized testing conditions

Strab/Amblyopia (6 decks)

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