ND - Visual Development and Amblyopia - Week 3

Question 1

Infants have poorer visual acuity. Is this due to poor optics?

Answer 1

No

Question 2

Explain the state of the peripheral and central retina of an infant and how this contributes to the state of their visual acuity. Also mention the state of the visual cortex.

Answer 2

The rod-dominated peripheral retina appears normal.
The all-cone fovea contains widely-spaced cells and poorly developed cones.
The visual cortex is not fully developed.

Question 3

Do the afferent pathways from the two eyes separate before birth or do they remain segregated?

Answer 3

They remain segregated as they project to the visual cortex

Question 4

What does monocular deprivation lead to?

Answer 4

Ocular dominance shift
(contralateral deprivation results in ipsilateral domination)

Question 5

Consider a deprived eye inducing ocular dominance shift. Does the non-deprived eye take over most of the available cortical space or does it remain confined to its normal half?

Answer 5

It takes over most of the available space

Question 6

What occurs with binocular deprivation? Are receptive fields abnormal?

Answer 6

Causes only fewer binocular cells
Receptive fields are not very abnormal

Question 7

What can be said of the LGN afferents terminating in layer 4? What happens to them in early development?

Answer 7

They have markedly overlapping arbors. With early development, distinct ocular dominance patterns are evident.

Question 8

Is there competition between the geniculocortical inputs of the two eyes for cortical space?

Answer 8

Yesd

Question 9

What is essential to establishing normal connectivity in the LGN and visual cortex?

Answer 9

Form vision

Question 10

What kind of changes occur earlier along the visual pathway, in the retina and LGN?

Answer 10

Shrinkage of cells in the deprived LGN laminae

Question 11

Is there a critical period for susceptibility to ocular dominance shifts or is it relatively equal (2)?

Answer 11

There is a critical period, and the different visual functions have different critical periods (stereopsis, contrast sensitivity, motion perception etc)

Question 12

Define occlusion amblyopia.

Answer 12

When one eye is occluded by congenital cataract or lid ptosis

Question 13

Define anisometropic amblyopia.

Answer 13

When the two eyes have very different refractive errors

Question 14

Define strabismic amblyopia.

Answer 14

When one eye is deviated

Question 15

Why is visual acuity poor in one eye in conditions like occlusion/anisometropic/strabismic amblyopia? Explain why.

Answer 15

Abnormal neural development, few cortical cells are driven by the amblyopic eye

Question 16

How is stereopsis affected in occlusion/anisometropic/strabismic amblyopia and why?

Answer 16

Lack of binocular cells in the cortex results in poor stereopsis

Question 17

How is amblyopia generally treated in children?

Answer 17

The non-deprived eye is patched.

Question 18

What is a treatment option for adult amblyopia? Explain what this process is called.

Answer 18

Playing videogames with the amblyopic eye was able to improve VA in the eye, improving stereopsis. This is due to neural plasticity.

Question 19

Can patching be done for adult amblyopia? Explain.

Answer 19

Yes, the deprived eye is exposed to fractionated and uninformative images that still preserve contrast, luminance, spatial frequency, and motion.

Question 20

Is the concept of a critical period restricted to vision alone?

Answer 20

Likely not