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Amblyopia Flashcards

1
Q

What is amblyopia

A

Reduced visual acuity which is not the result if any current pathology and which cannot immeaditley be improved by the correction of refractive error

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2
Q

How can amblyopia develop

A
  • if your born with a congential catarcat - and the inside oif your lense = cloudy - the retina dosnt recieve a good image - and the cataract has gone away - i.e. you dont have the current pathology anymore - your vision is still reduced due to historical pathology - that could be the cause of amblyopia
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3
Q

Is visual acuity reduced in one eye or both eyes

A

Reduction of visual acuity can be in one eye or it can be in both eyes

  • vision cannot be improved immeaditle - i.e. with trial lenses
    Vision may improve over time with refractive correction

Amblyopia affects 4% of the population

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4
Q

How does vision develop

A

The visual system is the most complex sensory system in the human body

However it is the least mature at birth

Though they have the anatomical structures needed for sight infants have not learnt yet to use them

Much of their first weeks and months are spent learning how to see

As children grow more complex skills like visual perception develop

Eyes become sensitive to light at 22 days of gestation

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5
Q

How is visual acuity developed

A
  • normal visual experience is necessary

Rods and cones synapse wirth ganglion cells in the retina

Parvocellular (x) system needs a stable well focused image

LGN - relay station

Cells in the visual cortex

Parvocellular system = responisble for central vision - (fine acuity)

LGN - relays imformation to the visual corte at the back of the brain - where the majority of visual procesing happens

V1 = primary visual cortex

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6
Q

What may interfere with normal visual imput

A

For all of this to develop normally - need to be introduced into a full visual enviroment - if the visual envrioment is limited = limited visual processing

Abnormal binocular imput leads to bsv not developing - i.e. eyes not working together - results in amblyopia

  • if one eye has poorer vision and needs refrcative corretion - (ANIOSMETROPIA) - 2 eyes have a different refractive power

Occlusion - i.e. anything that occludes the eye and stops one eye from seeing - e.g. ptosis - one lid drooped down - no light would be able to get through - that would be a cause for one eye not getting the same level of visual imput - as the other eye and would result in amblyopia

Scratch to the cornea - surface on the front of the eye - may become hazy - inisde the eye - completeley cloudy the light through with a congential traumatic cataract

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7
Q

What causes amblyopia

A

Amblyopia = a developmental condition
A condition that develops because of abnormal visual input during critical period during a childs life

Big cause = aniesmetropa - slighlty different refractive powers in each eye - one eye is easier to see through than the other

Malutrition

Constant strabismus an eye that is comstantly deviated - due to the childhood brain not wanting to see double their is a phenomena of supression - visual cortex closes off and chooses not to pay attention to a stimulus causing the diplopic image - constant starbismus because we only wanrt to see one image

Supression and amblyopia are interrelated

Corneal scars - stimulus deprication

Being born prematurely

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8
Q

What is the critical period

A

Amblyopia develops during the critical period when imparied imput affects neural plastciity - i,e, eye and brain still open to develop and their is time for it to develop - most vunreavle to damage - critical period (deprivation results in loss of function)

During the critical period - any kind of deprivation will result in a loss of visual function in that eye - when development is happening the eye is most vunreable to insult/injury

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9
Q

What is the sensitive period

A

We would offer treatment during the sensitive period
Improvement = possible

We would be concerned about anythuing affecting visual development during the critical period

The critical period lasts from 2-8 but children are offered treatment for amblyopia up to the age of 12

As you get older the susceptoibility to loss of fucntion slows down - improvement can happen = less

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10
Q

When are you most suceptible to interference in visual development

A

In early childhood you are most suceptible to interference in visual development - beyond that age you see smaller improvemenrt - as you get older the vunreability to the visual interference slows down

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11
Q

When is amblyopia most likely to develop

A

Amblyopia develops during the critical period when imparied imput affects neural plasticity

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12
Q

What is the difference in the critical period and the sensitve period

A

Critical period - deprivation results in a loss of function

Sensitive period - improvement is possible

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13
Q

What is happening in the visual system during the critical period?

A
  • during this period the visual cortex is undergoing the most processing development
  • in the visual cortex you have ocular dominance coloumns
  • these are neural structures which are not fully wired/sjaped - they take shape during the first months of life

If one eye is not used during the critical period - the neurons in the ocular dominace colpumns that should recieve visual imformation from the underused eye (potentially amblyopic eye) - dont develop normally

Because the brain that wants to make the most of the imput its receiving - the eye actually becomes wired towards the normal eye

The nerual basis of the visual cortex (the ocular dominance coloumns) becomes tuned in to seeing in the stronger seein eye

  • the eye begins to process all the imformation coming from the normal eye instead of euqally distributing imformation to either eye
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14
Q

What happens to the ocular dominace coloumns in the development of amblyopia

A

The ocular dominance coloumns that are being underused - i.e. the one that has the cataract or the one that is deviaitng or that one has a strnger need for glasses - the ocular dominace coloumns representing that eye that is not used -dont waste away - because one eye is seeing well the ocular dominance coloumns will start to unravel and procss imformation from the better seeing eye

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15
Q

What happens if you dont treat amblyopia before the critical period

A

Once critical period ends you get to the end of visual maturation - if nothing is done about amblyopia - sight is permeantly imparied in that eye - once we have reached maturation the visual system and vrain - fully wired up/matured

Once critical period ends malubility is lost and sight can be permeantly lost in that amblyopic eye

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16
Q

What is the crowding phemomena

A

Difficulty in seperating letters - if you have a line of letters of the same size and the same test types - a patient who has crowding can easily identify the middle letters with more diffculy they can identify the outside letters
Crowding phenomena - the pehnomena which a line of letters or symbols of the same size on a test types are typically identified less easily than single optotypes

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17
Q

What is a key attribute of amblyopia

A
  • crowding
    can occur in other conditions which affect VA
    E.g. if we test a three year old and we show them kay pictures - i.e. one picture at a time - that will not detetc amblyopia/crowding

Because amvblyopes are so affected by crowding we need to do a crowding test if we exepect any chance of amblyopia

Only crowding test may pick up any deficeny in visual acutiy

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18
Q

How does amblyopia affect fixation

A
  • i.e. patient as a constant right esotropia

Harder to fixate with right eye - would suggest reduced vision - less accurate fixation

Might have slow fixation/ unable to fixation

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19
Q

What type of fixation pattern is exected in amblyopia

A

In strabismic amblyopia - unilateral constant deviaition is expected - and i comparing the vision to one eye to the other when more accurate tests not possible ,consider…

  • rate of fixation
  • accuracy of fixation
  • ability to hold fixation
  • objection to coveribg one eye
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20
Q

What is a cross fixation

A

They have a esotropia but it alternates

I.e. when they look to the ledt the look with right esotropic eye when they look to the right they look with their left esotropic eye

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21
Q

How would you asess a patient who dosnt have a constant strabismus (manifest) fixation pattern

A

If they dont have a manifest strabismus - we might want to asess if they have a difference in fixation pattern - we would need to induce strabismus using a 10 dipoter fixation test

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22
Q

What is a 10 dipoter fixation test

A

Fixation preference testing has been useful in detecting amblyopia in chidren unable to give reliable visual acutiies - except for children with small angle tropia and those without manifest deviaitons - by placing a 10 dipoter vertical prism over one eye we induce a vertical deviation - once the eyes are dissociated- (refers tio the situations where the innervation of one eye causes it to move involoiunatirly or independly of the other eye) once the eyes are disscociated fixation preference is evaluated and used to predict the presence of amblyopia

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23
Q

If you have a patient with straight eyes and you place a prism base diwn in front of the eye what results would you expect

A

If you have a patient with straight eyes - you place a prism down in fron tofbthe eye - this induces dipolopia and the patients eye will move up and down

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24
Q

What is a normal response (indicating equal VA) to amblyopia

A

Spontaneous alternation - they alternate between the upper and lower image - if this does not occur occulde preffered eye momnentairlty - this response indicates equal vision - they might want to look at one image and then realise that the other one isnt there - when you cover the eye they might move to the other image - when you take the occluder away fixation is maintained for 5 secoinds through a blink or pursuit movment - indicates eqaul va- because you have given a patient two images and they are not bothered at which they look at - images are equal/clear

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25
Q

What ar abnormal responses to the 10 dipoter test

A

Abnormal responses (i.e. indicating unequal VA)

  • refixation is delayed by 3 seconds but not through a blink - fixation is maintained only for 1-2 seconds - then they go back to the preferred image
  • refixation maintaiend only for 1-2 seconds - then they go back to the preferred image
  • refixation as soon as cover removed

I.e. you cover one eye and they immeasdiley go back to the preffered image as soon as the occluder is removed

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26
Q

How else would you assess fixation

A

You can also look at which part of the retina is being used to see with - at the back of the eye you have the fovea - where all the cone cells for the central vision are - is a pit

Retina - flat except for the fovea - densely packed with cone photoreceptors - when you shine a light into the eye the fovea acts like a concave mirror - it bounces the light that you shine into the back of the eye towards you - you can check weather the fovea is being used by the patient when you examine them with a ophthalmoscope

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27
Q

What is uniocular fixation

A

The part on the retina which is used for fixation when the fellow eye is occluded in normal eye is the fovea

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28
Q

What is central fixation?

A

The use of the fovea - the reception of an image of the fixation object by the fovea - object lying in the principle visual direction - central fixation may be unsteady or steady - results in a reduced va

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29
Q

What is a eccentric fixation

A

Eccentric fixation - a uniocular condition - (when the amblyopia eye us being use) in which there is fixation of an object by a point other than the fovea - the point adopted to the principle visual direction

The degree of eccentric fixation is defined by the distance from the fovea in degrees

It is usually the point on the retina that adopts principle visual direction I.e. if the eye is exotropia it will be the nasal retina

The further way from the fovea the eccentric fixation point is the poorer the VA will be

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30
Q

What is wandering fixation

A

When the fovea has lost functional superiority over the rest of the retina thy eye doesn’t care about which point is being used to process visual information - this indicates really poor VA -

Wandering fixation - is a uniocular condition in which the fovea has lost its functional superiority and no one retinal element is used for fixation

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31
Q

What is the opthalmoscope used for

A
  • ask patient to look at the centre of the graticule
    For the best vision you want the patient to using the fovea to see the actual target - if they are using erratic parts VA will be affected
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32
Q

How are amblyopia and uniocular fixation related

A

Va is reduced if fixation is unsteady /not central - the area of the retina used dictates potential for va but amblyopia superimposed o this may reduce VA further I.e. if they are using a parafoval location (part on the retina that’s just next to the fovea) that might mean we want too get fixation

Where amblyopia is present uniocular fixation may be assessed

Things we need for good VA are central foveal and steady fixation

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33
Q

Is accommodation measured routinely in amblyopia

A

Not routinely measured in amblyopia - it is difficult to measure subjectictlvely as where va is reduced blur is not appreciated easily - accommodation measured objectively has been found to be reduced/ less accurate in amblyopia

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34
Q

What is the treatment of amblyopia.

A

Critical period - what’s the patients age , correction of refractive error

The refractive adaption period - we just give the patient glasses to see how much vision improves alone - before we step in to do something else

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35
Q

What is amblyopia

A

Amblyopia is defined as a defective visual acuity (va in one or both eyes) which persists after correction of the refractive error and removal of the pathological obstacle to the vision

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36
Q

What is stimulus depriviation of amblyopia

A

Stimulus deprivation amblyopia is characterised as the following - it affects one or both eyes

Stimulus deprivation - when little or no light enters the eye and no image is formed - as in ptosis is covering the pupil or it can be partial allowing some passage of light and the formation of a poor quality image e..g a corneal scar other conditions that may result in this type of amblyopia are congential cataract , hypephema and vitreous opacity

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37
Q

What are the features of strabismic amblyopia

A
  • strabismic amblyopia- has the following features - it is the consequence of constant or near constant unilateral strabismus with onset in childhood
  • it occurs mainly in esotropia
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38
Q

What are the features of aniosmetropic amblyopia

A
  • anisometropic amblyopia is where there is a significant difference in the refraction of the two eyes such that one eye receives a clearer image for all distances

The refractive error can be predominately spherical or predominately astigmatic

39
Q

What is meridonial amblyopia

A

This occurs when there is a moderate or a high degree of uncorrected astigmatism in one or both of the eyes - astigmatism = irregular curvature of the cornea

40
Q

When does amblyopia develop

A

Amblyopia develops only in the critical period when neural plasticity makes the visual system vulnerable to any abnormal experience such as strabismus , a blurred image or occlusion , once this period is over amblyopia dose not develop .

41
Q

How is amblyopia diagnosed

A
  • a detailed history should be taken in all cases with particular reference to the parents opinion of the childs vision , the age of onset and duration of any strabismus present and the family history
    The aim of the examination is the comparison of - the visual function of the two eyes
    The patients known or estimated vision with the norm for his or her age

The diagnosis of amblyopia is based on the following

  • the estimation or perfervbaly the measurement of va in each eye
  • the assessment of fixation in the amblyopic eye and on fixation preference in manifest strabismus
  • refraction and careful examination of the fundi and media
42
Q

What are the main factors considered in patient selection

A
  • age - amblyopia is usually treated in childhood - the younger the patient the better and the more rapid the response - most children are referred to before the age of 4 years
  • general health - e.g. a deaf child relies on lip reading - and children with defective mobility may lose confidence or regress if occluded
  • all patients must be wearing a correction for any significant refractive error- constant spectacle wear can result in improvement of vision in some cases
43
Q

What are some methods of treatment to restore visual acuity in amblyopia

A
  • the principle underlying the restoration of va is to promote the use of the amblyopic eye or eyes - this can be achieved by
  • refractive adaptation
  • occlusion of the better eye
  • cyclopegic drugs alone or in combination with optical penalisation
  • refractive surgery
  • systemic drugs
44
Q

What is refractive adaptation

A
  • the refractive error should be prescribed and worn for up to 16 weeks as acuity has been demonstrated to improve with glasses wear alone - even in the amblyopic eye of a patient with manifest strabismus
45
Q

What are the different types of occlusion treatment for patients with amblyopia

A
  • total occlusion - excluding all light and form -
  • total occlusion excluding form but allowing the passage of some light
  • partial occlusion - allowing the appreciation of form but distinguishing acuity
46
Q

What is optical penalisation

A
  • the principle of optical penalisation is the use of lenses to blur the va of the better and augment the va of the amblyopic eye

Three types of penalisation - distance penalisation, near penalisation , total penalisation

The choice depends mainly on the degree of amblyopia

Distance penalisation - encourages use of the amblyopic eye for distance - this is achieved by prescribing an optimum correction for the amblyopic eye and adding 3ds to the better eye

Near penalisation encourages the use of the amblyopic eye for near - this is achieved by using cycle-legislation in in the better eye with full correction and adding a convex lens (up to 3ds to the amblyopic eye

Total penalisation encourages the use of the amblyopic eye for all distances - this is achieved by adding a strong convex lens (or occasionally atropine and a strong concave lens) to the better eye so that the amblyopic eye sees best for both near and distance

47
Q

How are cycloplegic drugs used in the treatment for amblyopia

A

Cycloplegic drugs - cycloplegia is the paralysis of the ciliary muscle resulting the loss of the accommodation - cycloplegia with accompanying mydrasis (dilation of the pupil) is usually due to the topical application of muscaranic antagonists such as atropine - the principle use of cycloplegia in this context is to blur the vision of the better eye by preventing accommodation and decreasing the depth of focus - the usual response is that the child will use the amblyopic eye for near distance and the better eye for distance fixation .

48
Q

When might you use cycloplegia and optical penalisation

A
  • cycloplegia and/or optical penalisation can be effective in children with moderate or mild amblyopia who do not cooperate with occlusion
  • when the level of va has improved to some extent with occlusion but has become static
  • when occlusion has been worn for a long time and the child becomes tired of it
49
Q

Describe the ateiology of amblyopia

A

Whichever factor is present to cause amblyopia there is a reduction in the quality of input to the eyes- strabismus may be surgically induced, asmeitetropia produced by the use of lenses, cycloplegia or radial keratotomy and stimulus deprivation

50
Q

What happens to the ganglion cells in amblyopia

A
  • x or sustained ganglion cells are present in the central area of the eye - they respond to a well focused stable image and only pick stimuli within a small area - in amblyopia these cells show poorer spatial resolution and ability to detect contrast (particularly at high spatial frequencies)
51
Q

What happens to the lateral geniculate body in the development of amblyopia

A

In amblyopia changes in the parvocellular layers relating to the affected eye found such that these cells have a lower resolving power and a loss of contrast sensitivity at higher spatial frequencies

52
Q

What happens to the visual cortex in amblyopia

A
  • the effects on cortical cells not only involve the loss of spatial resolution and contrast sensitivity but also effect the on the response of input to either eye - about 80 percent of the cells in the visual cortex normally respond to input from either eye at separate times however where monocular input has been reduced this falls only to 7% - if the reduced input is bilateral the percentage of cells responding to stimulus from either eye is 41%
53
Q

What is amblyopia

A

A unilateral or bilateral decrease of va caused by a pattern of vision deprivation or abnormal bionocualr interaction - either their is a deprivation of stimulus reducing the retina or their is a abnormal binocular interaction - for which no cause can be detected in physical examination of the eye and which in appropriate cases is treatable by therapeutic manners (Von noorden 2002)

54
Q

What is the prevalence of amblyopia

A

Estimated to affect between 1 to 4 % of children - recent large studies estimate 1.6% and 5.6%
Higher in medically underused/ lower socioeconomic classes

55
Q

What are the types of amblyopia

A
  • strabismic, anisometropic, stimulus deprivation (occlusion)

Ametropic - where refractive error is present or where distant objects are not longer focused on the retina - high refractive error

Meridonal - astigmatism

Ametropic and meridonal amblyopia are both bilateral

Idiopathic = no known cause

Toxic - amblyopia - caused by toxicity to the retinal vascularture

56
Q

What are diagnostic signs of amblyopia

A
  • it responds to treatment
  • patient not responding to treatment needs further Investigation
  • NB - if it doesn’t respond to treatment it may be organic amblyopia e.g. optic nerve tumour
57
Q

What is organic amblyopia

A
  • organic amblyopia = irreversible amblyopia caused by ocular pathology that will limit vision improvement - structural abnormalities of the retina or the optic nerve may be present - functional amblyopia at be superimposed on the organic visual loss
58
Q

What are the different types of organic amblyopia

A

Definition of organic amblyopia = no lesion detectable but commonly used for the following conditions

  • achromotopsia - lack of cone receptors - high acuity -detect cover test
  • albinism -

Also where conditions are irreversible

  • tobacco amblyopia
  • other toxins

Would result in a decrease in vision

True causes suggested but unproven

Transient retinal haemorrhage - inhibition to visual system during early period - impede signals to photoreceptors
- maloriientation of retinal receptors — babies who are premature are much more likely to have retinopathy of prematurity - where the retina is much more likely to bleed and haemorrhage - transient retinal haemorrhages tend to build up over time

59
Q

What is hysterical or psychogenic amblyopia

A

Apparent amblyopia resulting from psychosomatic disorder or due to malingering

They often have very tubular visual fields
They have reduced visual acuity - and they can have reduced colour vision - they act in a way they can’t see

In a study conducted by Morris and Denis (1975) - they found that the visual pathway was intact

60
Q

What are some types of toxic amblyopia

A

Toxic amblyopia - visual acuity - loss due to absorption of toxic agents such as ethambutol, cyanide, ibuprofen. Usually reversible (arsenic poisoning not reversible)

Tobacco amblyopia - toxins of tobacco constrict retinal blood vessels - optic nerve may be sensitive to tobacco - can cause optic neuritis (swelling of optic nerve)

Nutritional amblyopia - caused by a deficet of vitamin b12 - often seen in alcoholics and with extreme diets - complete recovery is possible with an improved diet - but if deprivation is too prolonged - va damage is peremeant

Alchohol amblyopia - painless bilateral loss of vision . Toxic effects of alchoal cause optic neuropathy - alchoal depletes the body of nutrients often associated with b1 deficiency

61
Q

What is bupthalmus

A
  • this is where the eye develops glaucoma - high iop - this is. Common complication of cataract
    More prevalent in cataracts that have received intraoucalr lens under the age of 1
    The intraocular pressure increases
    Because the eye is very adaptable when the child is young - the eye wants to release that pressure to save its sight
    Because everything Is fluid and developing the eye grows to release that pressure
    Which means the eye develops myopia - so this condition would be called an anisomyopia - secondary to bupthalmus - best thing is surgery which helps the flow of aqueous out of the trabecular mesh work and stabilised the pressure in that eye and then keep the child under regular review - sometimes it can be better that they have contact lens - it= a very strong difference - that can reduce the difference in the image size slightly

Bupthalmus - causes a anisometropic amblyopia

62
Q

What type of amblyopia may be caused by a right lower lid haemgiominia

A

Tends to press on the cornea- it presses on the cornea in such a way that it tends to induce an astigmatism

  • because the eye becomes not spherical in its front surface at the cornea - meridional amblyopia - you nay expect a stimulus deprivation amblyopia - because it is covering part of the pupil - we would also think about a partial stimulus deprivation amblyopia - because once haemngioma is operated on and removed the astigamatism could still persist because the pressure has been their for long enoug - we treat the cause and then the remaining amblyopia -

As a result the child could have meridional amblyopia but also stimulus deprivation and anisometropic amblyopia aswell

63
Q

What causes stimulus deprivation amblyopia

A
  • when we see a ptosis or any kind of obstruction to the pupil that’s when we think about stimulus deprivation - a right lower lid haemangiomia is obscuring the lower lid pupil - not just the upper part of the lid that can be obscured by lid lesions and ptosis but also the lower lid
64
Q

What is a ametropic amblyopia

A

Retina cannot focus on the Image of a distant object
When you look through the glasses of somebody short sighted you can see the edge of their faces move inwards under the glasses and its in both eyes so it is a ametropic amblyopia

65
Q

How would you investigate and diagnose amblyopia

A
  • case history - is their a history of amblyopia
  • was their a history of ptosis that was operated on in a different hospital
  • key things in case history - has anybody got astigmatism have the parents got a refractive error - any glaucoma affecting children in the family
  • checking that their is no pathology- that is crucial to amblyopia diagnosis
  • fundus and media check
    Refraction =- check for anisometropic or an ametropic
  • visua; acuity - crowded if possible - amblyopia is highly associated with crowding - and so if we don’t do a crowded test we might not detect the amblyopia - the pinhole helps to detect weather their is any increased refractive error

Contrast sensitivity - in children you are using the lea paddles to detect the different levels - we test contrast sensitivity with pairs-forms black and white lines -the closer they are together the higher the spatial frequency - cover test - to see if they prefer to look with one eye or the other

Anisometropic and and strabismic amblyopia may have more mild losses of contrast sensitivity especially at higher spatial frequencies - spatial frequencies refers to how close the black and white lines are

66
Q

What is the cover test used for in the investigation of amblyopia

A

Cover test - to see if they prefer to look with one eye or the other

    • to look for a fixation pattern
67
Q

What is the 10 diopter prism test used for

A

If they havent got a deviation - we can put a vertical prism in front of one of their eyes which will Induce Diplopia - and if they don’t have a preference for using one eye or the other eye they will just flick their eyes up and down between the two images - but if they predetermined one eye - I.e. one eye has better acuity - that should be clear when they induce diplopia with a 10 diopter prism

68
Q

What is a neutral density filter test

A
  • you increase the filter in front of the eye and an eye with strabismic amblyopia - may have decrease VA with neutral density filters - less than you might expect - of you are looking at just their grating acuity - I.e. when you look at preferential looking tests - these don’t detect amblyopia as well
69
Q

What do comparisons of ETDRS and elderly show

A

Comparison of pref looking and ETDRS In the elderly - majority of patients score better on preferential looking frediman et al 2001 - meaning that the PFL tests is overestimating visual acuity -

70
Q

Which eye is most commonly affected in amblyopia

A

Anisometropic amblyopia - with or without strabismus occurs more often in left eye than right eyes

59% left amblyopes among 2635 participants

Strabismic amblyopia - 50% left eye and 50% right eye

71
Q

Describe the role of refractive adaptation

A

18 weeks

Used to be that we started patahcing straight days as soon as we found out child had amblyopia

Stewart et all - study showed that some children just improve with glasses alone - but their were 5o children who remained amblyopic - then they started occlusion - not all children require occlusion sometimes just giving the eye a good image is enough to improve vision

72
Q

What is the aim of management in amblyopia

A

Aim is to achieve and maintain maximum visual acuity for the eye

Remove any cause for stimulus deprivation first - I.e. you don’t want to start patching when a child is waiting for cataract surgery - or you don’t want to start patching when they are waiting for ptosis surgery and they you need to correct any refractive erro and then allow a period of up to 18 weeks to allow a period of refractive adaptation

Choose appropriate form of occlusion therapy e.g. patch

Or therapy e.g. atropine penalisation

Discontinue occlusion when max accuity is achieved and observe for stabilisation of acuity - sometimes what we find is that when we stop the patching and the visual acuity drops - then you would want to try and encourage that vision to come back up - we refer to weening people of patching is we reduce the time slightly rather than stoping is abruptly we tend to find that the va is better maintained

Go back to occlusion therapy if va is not minaintained

73
Q

What are the different types of occlusion

A

Total light occlusion -
Atropine penalisation
Total form occlusion - e.g. blenderm
Tend to use it more for patients who are elderly or have troublesome diplopia - we stick it on the glasses

Partial form occlusion - e..g. Cellotape

Atropine penalisation - has good results - positive research found

Optical penalisation is where you would give the non amblyopic eye - a high plus lens to stop them from looking through - however they may look over the top

CAM vision stimulator - not done in the uk

74
Q

What does PTTO and FFTO

A

Parity time total occlusion - common
FFTO - full time total occlusion - rare - most common scenario - stimulus deprivation - amblyopia and dense amblyopia - you would never do this in a really young baby - we would start with the hours of the months they are I.e. if they were 2 months we would start with 2 hours - you would do this because you wouldn’t want to induce occlusion amblyopia

75
Q

What type of treatment is atropine penalisation

A

Atropine penalisation is known as cycloplegic treatment - they are indicated for use in cycloplegia refraction to analyse the ciliary muscle in order to determine the true refractive error of the eye - research suggests that you don’t need to do it everyday - you only need to do it twice a week

Atropine 1% twice weekly

Common side effects

  • allergy
    Dry mouth
    Flushing
    Glare due to dilated pupil

Ointment is absorbed more slowly than drops - therefore lower risk of side effects

76
Q

What are the signs of an adverse drug reaction with atropine

A
  • dry mouth (with difficulty in swallowing and talking)
  • flushing and dry skin
  • transient bradycardia - followed by tachycardia and palpatations and arythmias (always check patient hasn’t had problems with heart before atropine treatment)
  • reduced bronchial secretions
  • urinal urgency and retintion and constipation
  • confusion particularly in the elderly
  • nausea, cpominding and giddiness

Ointment is absorbed more slowly than drops - therefore lower risk of side effects

77
Q

In the event of an adr what should you do

A
  • stop treatment
  • seek emergency assistance if appropriate
  • report to a yellow card scheme
78
Q

What do we do to guide our choices

A
  • things that can guide our choices are their level of vision

Fixation

Age

Vision

School work

Duration of strabismus

Atropine was typically only thought to be effective if the vision in the amblyopic eye was 6/24 or 6/36

It wasn’t thought to be successful for 6/60

Latent or manifest latent nystagmus - when you cover one eye - the nystagmus gets a lot higher in amplitude - level of visual acuity is related to the movement in nystagmus - the more the movement the less the visual acuity - not a good candidate for patching - you cover the eye and the eye will move around a lot more - so the visual acuity will go down - so a better treatment for these would be atropine - if they decompnesate - - if they have a binocular single vision but it’s tenuous - you might lose it when you patch them - if you take away their binoclulairy then they might be better treatnment with atropine

79
Q

What differences have been found with atropine compared top occlusion treatment

A
  • same results for occlusion and atropine according to pedig (2002)

For moderate levels of amblyopia

Atropine - found more acceptable by parents

No long term difference between atropine penalisation aged 10 years (PEDIG 2002)

80
Q

What have studies said about prescribed dosage

A
  • 6 hours daily occlusion produces the same effect as full time occlusion (Patients were 3 years with severe amblyopia)
  • visual acuity between 6/30 and 6/120 - and same effect in all levels of amblyopia in older children (7-12 children)
  • 2 hours daily patching produces a va improvement similar to that of 6 hours in moderate amblyopia va better than 6/30
  • 2 hours daily patching compared with one hour of near visual activities improves moderate to severe amblyopia in children 3-7 years old more than glasses alone
  • weekend atropine - produced similar levels of improvement to daily atropine for moderate amblyopes (6/212 - 6/24)

Weekend atropine can improve va in the ambyopic eye in children added 3-12 years with severe amblyopia

  • atropine 1 percent is as effective as occlusion for VA’S of 6/12 -
81
Q

Does evidence justify full time occlusion

A

No - if you have someone with someone severe amblyopia e.g. 6/120 you might start with 6hrs a day - but their isn’t a justification to start with more than that - we may increase that overtime - what are the advantages of atropine rather than occlusion - patch is just their for a couple of hours - a day for most children -

82
Q

What are the advantages of atropine rather than occlusion

A
  • patch is just for a couple of hours
  • a day for most children
  • but the atropine is working all the time
  • all of their life when they are looking at different distances and different settings
  • the atropine is causing the eye to have work harder
    The most common age that we start patching is age 4-5
    Because of the pre school eye test
  • so is 6hrs of patching ever justified when 2hrs should suffice
83
Q

What factors influence the frequency of visits of children undergoing occlusion

A

Density of amblyopia
- age - the younger they are the more frequently you want to check them

  • va level

-

84
Q

What does treatment of amblyopia include

A

Treatment includes

  • advice to parents
  • encouragement of compliance
  • parents from low income families have shown lower compliance with treatment but greater gains from education -than parents from high income backgrounds- Dunbar et al - education is part of the Orthoptists role
85
Q

What age do we treat amblyopia

A
  • children should be offered treatment at least up until the age of 12 years (Holmes et al 2006)
86
Q

What are the typical results of treatment from occlusion

A

Successful treatment outcome acheieved in 63-83 percent of patients

  • success is affected by va At first visit and type of amblyopia
  • very cost effective treatment

44 times more cost effective than cataract surgery

85 times more cost effective than macular hole treatment in the elderly

(Cost of treatment is divided by the number of va lines improved )

87
Q

When to discontinue occlusion

A

When va is equal on a true linear test

Not on a grating or preferential looking test

When free alternation occurs - I.e. they don’t mind which they use

  • when no further improvement can be gained
  • reduction in density of suppression with danger of intractable diplopia - if the patient takes patch off and they can see 2 - we would want to discontinue patching
88
Q

Do all patients with a fixation preference have amblyopia

A
  • 65.7% of 13p patients with a fixation preference did not have amblyopia - inaccurate tracking , spatial uncertainty or spatial distortion may be responsible
  • contrast sensitivity may be differently affected than acuity - campos and guili (1985) only 29/57 patients treated for amblyopia were able to alternate after treatment - most commencing treatment prior for age 2 altered
89
Q

How should occlusion should be stopped

A
  • occlusion should be reduced rather than stopped abruptly

Recurrence may be more likely to occur if longer periods of occlusion (6hrs a day) stopped abruptly - therefore suggested to reduce to 2hrs a day (pedig 2004)

Walsh and la Roche (2008)- following full time occlusion in difference in recurrence weather treatment stopped abruptly or tapered (24% showed recurrence)

Risk of recurrence higher where greater improvement is achieved (Holmes et al 2007)

90
Q

What are contraindications to occlusion

A

Patch allergy
Eye infection
Latent nystagmus - if their nystagmus is going to increase when we patch them
If they have a pathological cause of reduced va - i.e they don’t. Have cone receptors

Patching all day and night wont help that

  • if they have a low density of suppression -if you put up the Sbisa bar and even on 1 filter or 2 filter they’d see 2 - risk of intractable diplopia - you don’t want to do occlusion

Failure of previous treatment

Child with multiple diagnosis / syndromes/ disabilities

Terminal diagnosis

Emotionaly upset by occlusion - try atropine

Social problems - e.g. dead and need lip reading

91
Q

What should you make sure of before you include

A
  • patients over 8- check density of occlusion on sbisa bar and do not occlude if very low
  • check density of suppression on the sbisa and do not occlude if very low (you don’t want to induce intractable diplopia)
  • possibility of eccentric fixation
92
Q

How do you treat eccentric fixation

A

I.e. they have a large angle deviation - and they use a part on the retina that is no where near the fovea to fixate - that could Cause worse vision then they need to have - so what you would want to do is disrupt their fixation

-

93
Q

If a child has a right esotropia what part of the retina are they using

A
  • using their nasal retina - really far away from the retina - it is causing them to have reduced vision then they need to have - you could patch their amblyopic eye -this is called indirect/ inverse occlusion
  • you would want to patch the eye constantly

Then you would take the patch off if you could get them to fixate

  • this may disrupt fixation on their area of the retina - the further you are away from the retina - the worse your va is - if that didn’t work then surgery is used to correct the angle - you would want to do it for the whole day - constantly
  • continual period of disruption to that fixation point

Pleoptics

Bangerters method - dazzle retina expcept fovea and stimulate fovea

Cuppers method - after image utilised

Haidnigers brishes - ensures foveal fixation

94
Q

What are the outcomes for amblyopia

A
  • highly treatable
  • high success rate to treatment
  • many options available - can be tailored to individual patient

Very cost effective

  • additional support is available to parents

……06 (8 decks)

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