BVP - Strabismus Assessment IV: Amblyopia - Week 12

Question 1

Define amblyopia.

Answer 1

Reduction in visual capacity of one or both eyes not improved by refractive correction and occurs in the absence of ocular or visual pathway pathology

Question 2

What can amblyopia result in the loss of?

Answer 2

Hand-eye coordination

Question 3

hat is one of the most common forms of visual impairment in the world?

Answer 3

Amblyopia

Question 4

Is amblyopia cheap to rehabilitate?

Answer 4

Yesd

Question 5

During the post-natal refining process, what percentage of the striate cortex receives binocular input?

Answer 5

80%

Question 6

What is meant by the sensitive period?

Answer 6

The time when amblyopia can occur.

Question 7

Describe how the post-natal refining process can be susceptible to amblyopia.

Answer 7

The reliance of the developing visual system on visual input makes it susceptible to abnormal input even if temporary

Question 8

When is the sensitive period?

Answer 8

From birth to ~7 yoa and up to 11-12 yoa

Question 9

List three mechanisms of amblyopia development.

Answer 9

Deprivation of form visiond
Abnormal binocular interaction
Both

Question 10

Describe deprivation of form vision and what it leads to neurologically.

Answer 10

When one eye is deprived of form vision, such as by anisometropia or cataracts, that eye will have a poorer image in the striate cortex and will not compete with the other eye’s image
Thus the axons of the eye with no form deprivation will take over the binocular cells

Question 11

What happens in the striate cortex during visual development?

Answer 11

It receives input from both eyes, which will compete for striate cortex space
If balanced there will be no amblyopia

Question 12

List two possible causes of deprivation of form vision.

Answer 12

Cataracts

High refractive error (including anisometropia)

Question 13

List two causes of abnormal binocular interaction.

Answer 13

There is a different image at corresponding points (strabismus)
If the relative clarity is different (unilateral cataract or anisometropia)

Question 14

Can strabismus result in form vision deprivation?

Answer 14

No

Question 15

Can high bilateral refractive error result in abnormal binocular interaction?

Answer 15

No

Question 16

Can bilateral cataract result in abnormal binocular interaction?

Answer 16

No

Question 17

Define amblyogenic factor.

Answer 17

A condition that will cause amblyopia if present during the sensitive period

Question 18

Describe how anisometropia is an amblyogenic factor.

Answer 18

Refractive blur in one eye causes the neural signals from that eye to be weaker than the signals from the other eye

Question 19

What does the strength of neural signals from our eyes depend on?

Answer 19

Contrast, not absolute light levels

Question 20

Describe how strabismus is an amblyogenic factor.

Answer 20

Diplopia is confusing and results in the suppression of some of the information from one eye

Question 21

Describe why suppression occurs with strabismus.

Answer 21

Diplopia is confusing and suppression is the most efficient way to deal with it

Question 22

Is suppression a monocular or binocular adaptation?

Answer 22

Binocular

Question 23

Does suppression involve the entire visual field of an eye?

Answer 23

No

Question 24

How are amblyopia and suppression related?

Answer 24

Amblyopia is a monocular sequelae to suppression

Question 25

Describe visual deprivation.

Answer 25

Physical blockage that stops the formation of a clear retinal image

Question 26

List 4 examples of visual deprivation.

Answer 26

Congenital or traumatic cataracts
Corneal opacities
Complete ptosis
Resolved perinatal macular haemorrhage

Question 27

Will the clinical sign of visual deprivation always persist? Explain.

Answer 27

The clinical sign may no longer exist (may need to be a diagnosis of exclusion)

Question 28

What is meant by orgnic amblyogenic factors?

Answer 28

Subtle, sub-ophthalmoscopic morphological changes or dietary insufficiencies

Question 29

Explain the association of nystagmus to amblyogenic factors.

Answer 29

Some amblyogenic factors are secondary to nystagmus

May be an obvious nystagnmus

Question 30

What is the most sensitive way to detect nystagmus?

Answer 30

Ophthalmoscopy - specifically visuoscopy

Question 31

Consider younger and older children with amblyopia. How do they respond to treatment (4)?

Answer 31

Younger are typically

• quicker (faster acuity improvement)
• better (better final acuity)
• happier (better compliance)
• more complete (better binocular function)

Question 32

How does amblyopia affect contrast sensitivity? Explain (2).

Answer 32

Reduced contrast sensitivity

• may be only at high spatial frequencies
• may be the entire CSF

Question 33

How does amblyopia affect VA?

Answer 33

Reduced VA (D and N)

Question 34

How does amblyopia affect spatial localisation?

Answer 34

Impaired (knowing where things are)

Question 35

How does amblyopia affect visual processing speed?

Answer 35

Reduced

Question 36

How does amblyopia affect binocular summation?

Answer 36

Reduced

Question 37

How does amblyopia affect sensory fusion?

Answer 37

Reduced

Question 38

How does amblyopia affect fixation?

Answer 38

Poor fixation

Question 39

How does amblyopia affect eye movements (saccades and pursuits)?

Answer 39

Poor eye movements
Innacurate saccades
Jerky pursuits

Question 40

How does amblyopia affect motor fusion? At worst, what is a consequence of this? At best?

Answer 40

Poor motor fusion

• at worst, strabismus
• at best, acc/verg disorder from reduced fusional vergence

Question 41

How does amblyopia affect accommodative function (lag, NPA, facility)?

Answer 41

Poor accommodative function

• increased lag
• remote NPA
• reduced facility (monocularly)

Question 42

Describe the treatment for amblyopia (4).

Answer 42

Provide a clear retinal image to the amblyopic eye
-glasses usually needed

Decrease the strength of the neural signals coming from the dominant eye
-an opaque patch or penalisation (atropine/translucent patch)

Treat any strabismus (motor and sensory)

Remove any other imediments to efficient binocular vision

• treat any residual accommodative dysfunction in the previously amblyopic eye
• treat visual inefficiencies

Question 43

Consider sensory and motor aspects of strabismus. List the treatment options for each aspect (5/3).

Answer 43

Motor

• glasses
• surgery
• vision therapy
• prism
• a combination of the above

Sensory

• maintenance patching
• anti-suppression training
• both