Disorders of the Ascending Pathway (M2)

Question 1

What are the signs and symptoms of strabismic amblyopia?

Answer 1

1. eye turn of affected eye
2. reduced optotype (Snellen) acuity in affected eye
3. suppression of affected eye during binocular viewing
4. little or no stereopsis

Question 2

At what age is there a lifetime maximum of synapses in V1?

Answer 2

0.5-1yr

Question 3

Which portion of the visual system is still developing postnatally? 1. Which is done? 2

Answer 3

1. V1 still developing

2. LGN fully retinotopically wired

Question 4

Is refractive amblyopia congenital or developmental?

Answer 4

developmental

Question 5

What is the process of how strabismic amblyopia develops from before and after birth?

Answer 5

1. prenatal waves from retina to LGN are ok
2. postnatally, the eye turn makes the same stimulus fall on non-corresponding positions of the two retinas
3. postnatal waves do not encourage orderly, projections
4. suppression of the turned eye occurs to prevent diplopia

Question 6

What are the patients that have spatial-frequency-tuned channels and then lose them? 1. Why does this occur? 2

Answer 6

1. refractive amblyopes
2. more blur of proximal stimulus during critical period = more high spatial frequency loss (modulation transfer function)

Question 7

What are the clinical consequences of strabismic amblyopia at the primary visual cortex?

Answer 7

1, impaired visual pattern recognition (reduced optotype acuity)

2. crowding (reduce optotype)
3. poor Vernier acuity
4. poor grating orientation identification acuity (“grating vertical or horizontal?”)
5. near-normal grating resolution acuity (Teller acuity)
6. poor stereo acuity

Question 8

What happens to the cells of the “handicapped” eye in the primary visual cortex if there is an amblyopia?

Answer 8

lose synaptic connections, making narrower columns

Question 9

Why does refractive amblyopia tend to occur in cases of anisometropia?

Answer 9

accommodation is consensual and usually controlled by eye of smaller refractive error so eye with larger refractive error has constant blur

Question 10

For complete achromatopsia, what is the inheritance? 1. What vision is normal and what is absent? 2. What are the signs and symptoms? 3

Answer 10

1. autosomal recessive
2. rod vision normal, cone vision completely absent
3. VA = 20/200, photophobia, no foveal reflex, and pendular nystagmus

Question 11

For Vernier acuity compared to grating acuity, what is the loss of acuity like for anisometropes? 1. For strabismics? 2. For mixed? 3

Answer 11

1. proportionate loss
2. much greater loss of vernier than grating acuity
3. intermediate more loss of vernier

Question 12

Where does the part of V1 that normally receives signals from the fovea receive info from for an achromatic patient?

Answer 12

signals from the parafoveal retina

Question 13

Is the loss of contrast sensitivity at high spatial frequencies higher or lower than the loss of visual resolution acuity?

Answer 13

equal

Question 14

What develops normally in refractive amblyopia in regards to the patients vision?

Answer 14

lowest spatial frequency channels normal

Question 15

When are patients most sensitive to refractive amblyopic damage? 1. Why? 2

Answer 15

1. under age 5

2. culling of synapses mostly done

Question 16

What type of vision may not be affected by a pure strabismic amblyopia?

Answer 16

1. have normal CSF

2. good resolution acuity

Question 17

Why do the retinal cells “fire together” during development before birth?

Answer 17

wave of spontaneous activity sweeps across the retina

Question 18

Is there a relationship between the amount of blur and depth of the amblyopia?

Answer 18

yes, more blur means worse spatial frequency loss

Question 19

What happens to patients that have blurred vision in both eyes?

Answer 19

1. critical period longer
2. eventually, connections lost and there is VA loss in both eyes
3. loss of motion perception

Question 20

For Vernier acuity compared to Snellen acuity, what is the loss of acuity like for anisometropes? 1. For strabismics? 2. For mixed? 3

Answer 20

1. proportionate loss
2. proportionate loss
3. proportionate loss

Question 21

What is the etiology of strabismic amblyopia?

Answer 21

1. eye turn in infancy/early childhood (more common for esotropia)
2. may have concomitant anisometropia (reduced contrast sensitivity and grating detection acuity in affected eye)

Question 22

What will the failure to remove a cataract in a child lead to?

Answer 22

1. unilateral amblyopia

2. severe bilateral perceptual losses

Question 23

Why do the retinal cells “fire together” during development after birth?

Answer 23

usual retinal stimulus

Question 24

What is the stereo deficiency seen in strabismic amblyopia due to?

Answer 24

1. misalignment of the eyes (clinically and developmentally?
2. scrambled signals from affected eye
3. suppression of affected eye