Amblyopia Flashcards

Question

What ar abnormal responses to the 10 dipoter test

Answer 1

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

Answer 2

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

Answer 3

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

Answer 4

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

Answer 5

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

Answer 6

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

Answer 7

- 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

Answer 8

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

Answer 9

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

Answer 10

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

Answer 11

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

Answer 12

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

Answer 13

- 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

Answer 14

- 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

Answer 15

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

Answer 16

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 .

Answer 17

- 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

Answer 18

- 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

Answer 19

- 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

Answer 20

- 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

Answer 21

- 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

Answer 22

- 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

Answer 23

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 .

Answer 24

- 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

Answer 25

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

Answer 26

- 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)

Answer 27

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

Answer 28

- 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%

Answer 29

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)

Answer 30

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

Answer 31

- 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

Answer 32

- 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

Answer 33

- 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

Answer 34

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

Answer 35

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

Answer 36

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

Answer 37

- 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

Answer 38

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

Answer 39

- 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

Answer 40

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

Answer 41

- 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

Answer 42

Cover test - to see if they prefer to look with one eye or the other - - to look for a fixation pattern

Answer 43

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

Answer 44

- 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

Answer 45

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 -

Answer 46

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

Answer 47

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

Answer 48

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

Answer 49

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

Answer 50

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

Answer 51

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

Answer 52

- 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

Answer 53

- stop treatment - seek emergency assistance if appropriate - report to a yellow card scheme

Answer 54

- 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

Answer 55

- 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)

Answer 56

- 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 -

Answer 57

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 -

Answer 58

- 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

Answer 59

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

Answer 60

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

Answer 61

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

Answer 62

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 )

Answer 63

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

Answer 64

- 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

Answer 65

- 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)

Answer 66

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

Answer 67

- 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

Answer 68

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 -

Answer 69

- 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

Answer 70

- 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