Packet 2 Amblyopia

Question 1

4 classifications of Amblyopia

Answer 1

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

Question 2

how does strabismic occur

Answer 2

foveal line of sight fails to intersect object of fixation

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

Question 3

1/3 of amblyopia in clinics is

Answer 3

anisometropic amblyopia

Question 4

some facts for anisometropic amblyopia

Answer 4

• 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

Question 5

what are some necessary characteristics of strabismus

Answer 5

• frequency
• laterality
• fixation distance

Question 6

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

Answer 6

no relationship

Question 7

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

Answer 7

3.50 D

Question 8

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

Answer 8

6.50 D

Question 9

50% had amblyopia when their hyperopia is greater than

Answer 9

2.50 D

Question 10

50% had amblyopia when their myopia was greater than

Answer 10

4.50 D

Question 11

what are some characteristics of isometropia amblyopia

Answer 11

• 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

Question 12

amount of hyperopic aniso that is amblyogenic

Answer 12

> or = 1.00 D

Question 13

amount of myopia aniso that is amblyogenic

Answer 13

> or = 3.00 D

Question 14

amount of astigmatism aniso that is amblyogenic

Answer 14

> or = 1.50D

Question 15

amount of isometropic hyperopia that is amblyogenic

Answer 15

> or = 4.00 D

Question 16

amount of isometropic myopia that is amblyogenic

Answer 16

> or = 6.00 D

Question 17

amount of isometropic astigmatism that is amblyogenic

Answer 17

> or = 2.00 D

Question 18

what are some things that can cause deprivation amblyopia

Answer 18

• any physical obstruction to line of site:

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

Question 19

what are some characteristics of deprivation amblyopia?

Answer 19

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

Question 20

what are the 2 amblyogenic mechanisms

Answer 20

1. form deprivation

2. abnormal binocular interaction

Question 21

what is form deprivation mechanism?

Answer 21

• 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

Question 22

what is abnormal binocular interaction mechanism?

Answer 22

• ABI caused by unequal or conflicting input to 2 eyes

- competitive, inhibitory effect leading to suppression

Question 23

what mechanism for strabismus?

Answer 23

ABI

Question 24

what mechanism for anisometropia?

Answer 24

both ABI and form deprivation

Question 25

what mechanism for isoametropia?

Answer 25

form deprivation

Question 26

what mechanism for deprivation (unilateral)?

Answer 26

ABI and form deprivation

Question 27

what mechanism for deprivation (bilateral)?

Answer 27

form deprivation

Question 28

in amblyopia, when is the most critical period

Answer 28

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

Question 29

which one is more powerful: ABI or form deprivation alone

Answer 29

ABI

Question 30

cut off for shallow amblyopia

Answer 30

20/20 - 20/32

Question 31

cut off for moderate amblyopia

Answer 31

20/40 - 20/80

Question 32

cut off for deep/severe amblyopia

Answer 32

20/100 or worse

Question 33

amblyopic eye behaviors

Answer 33

- 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

Question 34

amblyopic eye defects: behavioral responses related to:

Answer 34

- contour interaction effects - spatial distortion and uncertainty - reduced contrast sensitivity function - eccentric fixation - reduced accommodation - poor saccades - fixation instability

Question 35

some characteristics of ETDRS charts

Answer 35

- 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

Question 36

how do you measure VAs in people with latent nystagmus?

Answer 36

- high plus (like >+5.00) over fellow eye | - polarized testing conditions