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concom > Amblyopia > Flashcards

Amblyopia Flashcards

1
Q

What is amblyopia

A
  • reduction in vision In one or both eyes
  • persistent after correction
  • absence of retinal pathology or any disease
  • most common cause of visual loss in children
  • interruption of normal development
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2
Q

What can cause amblyopia

A
  • deprivation of form vision
  • abnormal binocular vision
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3
Q

What is depravation of form vision

A
  • can be partial or complete
  • complete: no image/stimulus reaches fovea
  • partial: degraded imaging reaching fovea
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4
Q

What is abnormal binocular vision

A
  • incomplete images fall on retina
  • images are incomparable
  • eyes compete for control over cortical connection during developmental period
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5
Q

Effects of amblyopia

A
  • reduced snellen and grating acuity
  • loss of contrast sensitivity
  • shape distortion
  • motion deficits
  • crowding effect
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6
Q

4 factors of visual function

A
  • light sense
  • form sense
  • colour sense
  • motion sense
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7
Q

What is light sense

A
  • ability to distinguish light and dark
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8
Q

What is form sense

A
  • Ability to distinguish between spatially separate visual stimuli
  • ability to discern size and shape of objects
  • position and orientation
  • rods and cones
  • most acute at fovea
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9
Q

Which region is responsible for motion sense

A
  • visual cortex
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10
Q

Periods of visual development

A
  • critical period
  • sensitive period
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11
Q

What is the critical period

A
  • period with active neural plasticity
  • deprivation impacts visual development
  • amblyopia can only develop in this time
  • earlier onset = longer the period of deprivation = worse outcome
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12
Q

What is the sensitive period

A
  • improvement is possible
  • teenage years
  • younger Px = quicker response to treatment
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13
Q

Effects of strabismus (on LGN and cortex)

A
  • high number of monocular cells
  • loss of stereoscopic vision, causing abnormal visual cortex
  • alternating strabismus results in an equal no. Of cells for R+L and virtually no binocularly driven cells
  • reduced retinal ganglion cell layer & LGN
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14
Q

Classifications of amblyopia

A
  • functional
  • no lesion
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15
Q

Types of functional amblyopia

A
  • strabismic
  • anisometropic
  • stimulus deprivation
  • meridional
  • ametropic
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16
Q

Types of no lesion amblyopia

A
  • organic
  • toxic
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17
Q

What is strabismic amblyopia

A
  • constant or near constant childhood strabismus in on eye, mostly esotropes as exotropes are intermittent
18
Q

Clinical characteristics of strabismus amblyopia

A
  • reduced vision in one eye
  • strabismus found on CT, usually not alternating
  • no pathology detected on ocular examination
  • occurs in 5-8% of general population
  • 4x greater risk if strabismic relative
  • 65% of Px have strabismic relative
19
Q

What is anisometropic amblyopia

A
  • significant anisometropia present
  • hypermetroia - most common
  • meridional - oblique astigmatism, more likely myopic
  • myopia - can be avoided if one eye clear for distance and one clear for near
20
Q

What is stimulus depravation amblyopia

A
  • one or both eyes
  • little or no light enters the eye
21
Q

What causes stimulus deprivation amblyopia

A
  • congenital cataract
  • ptosis
  • haemangima
  • vitreous opacity
  • corneal scar
22
Q

What is meridional amblyopia

A
  • moderate - high degree of uncorrected astigmatism - can be unilateral or bilateral
  • more significant risk in oblique astigmatism
23
Q

What is ammetropic amblyopia

A
  • likely bilateral
  • high degree of bilateral refractive error goes uncorrected during critical period
  • blurred vision in both eyes at all distances
  • typically a result of high bilateral hypermetropia 6D or more
24
Q

What is Organic amblyopia

A

Reversible - toxic amblyopia

Irreversible
- can’t be treated
- nystagmus
- albinism

25
Q

What is Toxic amblyopia

A
  • painless, progressive, bilateral vision loss
  • dyschromatopsia
  • may also be referred to as toxic optic neuropathy
26
Q

What is nutritional amblyopia

A
  • vitamin B12 deficiency
  • extreme diet, such as Px with ASD
  • may be complete/incomplete recovery with improved diet/vitamin intake
27
Q

What else causes nutritional amblyopia

A
  • alcohol
  • tobacco
  • antimalarials
  • anti cancer treatments
28
Q

Investigations for amblyopia

A
  • case history
  • ocular examination to assess fundus
  • full cycloplegic refraction
  • VA assessment
  • cover test
  • contrast sensitivity
  • uniocular fixation
  • 4 dioptre test
29
Q

Assessment of uniocular fixation

A
  • assess the point of the retina that the Px is using for fixation when the other eye is occluded
  • using ophthalmoscope
30
Q

Methods of Management of amblyopia

A
  • refractive adaptation
  • occlusion treatment
  • atropine
  • optical penalisation
31
Q

What is refractive adaptation

A
  • prescribed full refractive correction for full time wear
  • resolution of anisometropic amblyopia in 1/3 of 3-7 yr olds
  • resolution of amblyopia in 32% of Px with strabismic & combined strabismic and anisometropic amblyopia
  • refraction adaptation mostly complete by 18 weeks
  • 90% have resolution by 18 wks of refractive adaptation
  • improvement can continue for up to 30 weeks
32
Q

What is occlusion treatment

A
  • occlusion of non amblyopia eye
33
Q

Types of occlusion

A
  • total occlusion
  • partial occlusion
34
Q

What is total occlusion

A
  • excludes light and form vision
  • excludes form vision
35
Q

What is partial occlusion

A
  • some form vision but reduced acuity
36
Q

How long should Px be occluded - moderate and severe

A

Moderate - 2/6 hours
Severe - full time

37
Q

Risks of occlusion

A
  • intractable diplopia
  • amblyopia in other eye
  • dissociation in decompensating strabismus
  • allergic reaction
38
Q

What is atropine penalisation

A
  • prevents accommodation, and blurring vision at near fixation
  • instilled daily or 2 consecutive days per week
  • high compliance rate
39
Q

Why is atropine a good alternative

A
  • may be resistant to patch
  • allergic to patch
  • appearance of patch
40
Q

Downsides of atropine

A
  • light sensitivity
  • risk of allergic reaction
  • nightmares
41
Q

What is optical penalisation - and types

A
  • rx manipulated to blur vision in better eye
  • can be used on its own or with atropine
  • distance penalisation - +3.50 added
  • near penalisation - cyclo in non amblyopia eye with full correction and hypermetropic lens in amblyopic eye
  • total penalisation - high hypermetropic lens added to non amblyopic eye
42
Q

When is optical penalisation used

A
  • when cooperation with patching is poor
  • latent nystagmus
  • no improvement with other treatment
  • atropine alone not enough

concom (9 decks)

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