Amblyopia Flashcards
Aged 3 years.
Fundus and media normal. Refractive error RE: +0.25 LE +0.50 Not prescribed
Possible inward turning of left eye noticed since a baby.
VA R: 0.0 (6/6) L: 0.8 (6/38)
CT N & D Sl LET
OM Full
Fixation Ophthalmoscope RE Central LE Nasal, parafoveolar, unsteady
- Strabismic amblyopia
- Fundus and media check confirms no pathology
- Fixation ophthalmoscopy of right (better eye) assesses cooperation
- Fixation is adjacent to foveola, on side of retina towards nose
Aged 6 years.
Referred after routine visit to optometrist
Fundus and media normal. Refractive error RE: +6.00 LE +1.50
Glasses prescribed: R: +5.00 L: +0.50 (kids tend to overaccommodate so we may reduce their prescription slightly to allow them to relax into the glasses)
Has worn glasses for 10 days
VA with gls R: 1.00 (6/60) L: -0.1 (6/4.8)
CT with gls N & D No deviation
4ΔPRT R central suppression (foveal suppression, eye doesn’t move)
Frisby 600 secs of arc
- Anisometropic amblyopia
- Refractive adaptation should be allowed prior to start of occlusion
- If no improvement order full prescription as accommodation may be reduced in an amblyopic eye and this patient is undercorrected
Aged 8 years.
Has attended Eye clinic and Orthoptics since 6 months old
Had left unilateral congenital cataract at birth. Surgery to remove this at 4 months of age with intraocular lens (that is a lens placed within the eye).
Glasses prescribed: R: +1.00 L: +1.50/-0.75@180
VA with gls R: -0.1 (6/4.8) L: 0.6 (6/…)
CT with gls N & D sl LET
Bag gls Left suppression
Fixation Ophthalmolscope RE Central LE Central, unsteady
- Stimulus deprivation amblyopia
- Strabismic amblyopia
- Visual acuity with pinhole checks that reduction not due to need for change in refractive correction
- Care with occlusion to ensure intractable diplopia does not occur
What is the definition of Amblyopia?
A unilateral or bilateral decrease of visual acuity caused by pattern vision deprivation or abnormal binocular interaction for which no causes can be detected on physical examination of the eye, and which in appropriate cases is treatable by
therapeutic measures
Reduced visual acuity which is not the result of any current pathology and which cannot immediately be improved by the correction of the refractive error.
What’s the prevalence of amblyopia like?
Hashemi et al (2018) conducted a global & regional estimate of prevalence of amblyopia with a systematic review & found the pooled prevalence to be 1.75%. Europe reported a higher prevalence (3.67%) than Africa (0.51%). The most common cause of amblyopia was anisometropia (61.64%).
Overall estimated to occur in between 2 and 4% of children
Large studies estimate between 1.6% Kvanstrom et al (2001) and 3.6% (Williams et al 2001)
Higher in medically underserved / lower socioeconomic classes (Williams et al, 2008). Populations may encounter barriers to accessing healthcare (Ahmed et al, 2011)
What do we need to develop for visual acuity?
Normal visual experience necessary
Rods and cones synapse with ganglion cells in retina
Parvocellular (X) system needs
stable, well focused image (central vision)
Lateral geniculate body – relay station
Cells in visual cortex
What might interfere with normal visual input?
- Born with cataracts
- Mutation of the FOXL2 gene – BPES (blepharophimosis, ptosis, epicanthus inversus, and telecanthus)
- Coloboma (abnormal development of the eye)
- Retinopathy of premature
- Fetal alcohol syndrome
- Maternal Measles/maternal general health
Strabismus - Ptosis
- Bleed in the eye
- Children are born hypermetropic as the eye isn’t big enough for the refractive power of the eye +2.0DS or +3.0DS and emmetrisation occurs to become emmetropic over time. If born myopic it would affect their vision or if one eye is more hypermetropic than the other
When in Amblyopia are we more likely to see an improvement?
Amblyopia develops during the critical period when impaired input affects neural plasticity.
Critical Period (7-8yo)
Deprivation results in loss of function
Sensitive Period (up to 12yo)
Improvement possible
What happens to ocular dominance columns during the critical period?
Ocular-dominance columns are not fully wired at birth, but take shape during the first months of life.
If one eye is not used during this critical period, neurons in the ocular dominance column that should receive visual information from the unused eye do not develop normally, and instead become wired to the normal eye as trying to make the most of the information coming into it. Approx 90% will go to the seeing eye = lack of cortical processing of the amblyopic eye.
Ocular dominance columns representing the eye that is not used waste away. Once the critical period ends, sight is permanently impaired.
What is a key attribute of amblyopia?
The crowding phenomenon in which a line of letters or symbols of the same size on a test type are identified less easily than single optotypes
How does amblyopia affect fixation?
Fixation preference i.e. in CT the fixing eye may quickly return to fixation and find it harder to take up fixation with the amblyopic eye.
May use a pseudofovea, parafoveal or paramacular fixation point in amblyopia.
What are the fixation patterns and strabismus in Amblyopia?
In strabismic amblyopia unilateral constant deviation expected
Aid in comparing the VISION in one eye to the other, when more accurate tests not possible. Consider:
- Rate of fixation
- Accuracy of fixation
- Ability to hold fixation ?through blink or version - Can see if there’s a strong fixation preference by how quickly they can fixate with one eye = have reasonable vision in this eye for accurate fixation. Do they hold fixation when the occluder is taken away? Can see if they hold it through a blink. Does a child tolerate the occlusion of one eye but not the other?
- Objection to covering one eye
Have cross-fixation:
Esotropia but prefer to look with right eye when looking to the left and prefer the left eye when looking to the right
What is uniocular fixation?
The point on the retina which is used for fixation when fellow eye is occluded
Use the graticule (circle on the ophthalmoscope) to test
What is central fixation?
The reception of the image of the fixation object by the fovea, the fixation object lying in the principal visual direction.
Central fixation may be steady or unsteady (unsteady = worse vision)
Fixation is more unstable in amblyopic eyes than in fellow eyes and control eyes (Chung et al, 2015)
What is Eccentric fixation?
A uniocular condition in which there is fixation of an object by a point other than the fovea.
This point adopts the principal visual direction.
The degree of eccentric fixation is defined by its distance from the fovea in degrees.
What is wandering fixation?
A uniocular condition in which the fovea has lost its functional superiority and no one retinal element is used for fixation.
Worse fixation of all
What is fixation like in amblyopia?
VA is reduced if fixation is not central or if unsteady
Area of retina used dictates potential VA but amblyopia superimposed on this may reduce VA further
Where amblyopia is present, uniocular fixation may be assessed and sometimes fixation can get back on the fovea
What are the types of amblyopia?
Strabismic
Anisometropic
Stimulus Deprivation
Ametropic
Meridional
Idiopathic
Toxic
Reverse/Occlusion
Psychogenic
Which type(s) of Amblyopia is/are usually bilateral?
Ametropic
Meridional
Idiopathic
Toxic
What is Refractive Amblyopia?
Anisometropic or Ametropic Amblyopia
Uncorrected refractive errors are considered the most common cause of amblyopia. There are two main types of refractive amblyopia. Refractive errors have to be high enough to prohibit a clear retinal image at any distance. Patients with 3D of myopic anisometropia or more, 1.5D to 2D of astigmatic anisometropia and only 1D of hyperopic anisometropia are considered at risk for developing refractive amblyopia.
What is Anisometropic Amblyopia?
Refers to unilateral amblyopia caused by a distinct refractive error of each eye.
Anisometropic amblyopia is likely in the presence of 1.0–1.5 D or more anisohyperopia, 2.0 D or more anisoastigmatism, and 3.0–4.0 D or more anisomyopia.
What is Ametropic amblyopia?
Aka bilateral or isoametropic amblyopia
Due to bilateral high refractive error (ametropic amblyopia) result from large, approximately equal, uncorrected refractive error in both eyes of a young child.
Presence of 5.0–6.0 D or more of myopia, 4.0–5.0 D or more of hyperopia or 2.0–3.0 D or more of astigmatism
Isoametropic amblyopia is caused by image blur due to a high amount of bilateral ametropia. Lower values of ametropia can also result in anisometropic amblyopia—in addition to blur, the difference in refractive error can cause abnormal binocular vision and suppression. Can occur bilaterally
What is Ametropic amblyopia also known as?
Bilateral or isoametropic amblyopia
What is Meridional amblyopia?
Caused by significant astigmatism. Tends to be bilateral.
What is Strabismic amblyopia?
Results from suppression of the deviating eye. Constant strabismus leads to more severe amblyopia than intermittent strabismus. It is important to note that the size of the deviation is not related to the development of amblyopia, nor is the size of the deviation related to the severity of amblyopia, and even a very small-angle, constant, unilateral strabismus can cause strabismic amblyopia.
What is Deprivation amblyopia?
Amblyopia can be caused by form deprivation. Least common type but is typically the most severe form of amblyopia and develops when the visual axis is obstructed such as from ptosis, cornea opacities, cataracts, vitreous haemorrhage among others. Deprivation amblyopia is caused by a physical obstruction along the line of sight, which prevents a well focused, high contrast image on the retina.
What is Reverse Amblyopia?
Also known as occlusion amblyopia
Result of penalisation of the sound eye with patching or atropine during amblyopia treatment of the original amblyopic eye. Affects visual acuity but also binocularity, contrast sensitivity, grating acuity and central vs. eccentric fixation.
What is occlusion amblyopia also known as?
Reverse Amblyopia
What is Idiopathic amblyopia?
When there’s no known cause for the amblyopia (idiopathic)
What is psychogenic amblyopia?
Untapped potential so under the umbrella of amblyopia even though it’s not a true amblyopia
Most common in the teenage population of bilateral amblyopia.
Called functional visual loss or Streff syndrome, visual conversion reaction and hysterical amblyopia.
Often have multiple symptoms and reduced academic achievement.
Linked to visual or emotional stress and the prognosis is usually good. Visual acuity measures are variable, kinetic visual fields may spiral and an accommodative/vergence disorder is often present.
They may concentrate hard and read very slowly. It’s often emotional/ psychogenic.
What is Organic amblyopia?
In the strict sense of the definition of organic amblyopia, no lesion can be detectable and the amblyopia is irreversible. However, this term is used for conditions in which the reason for reduced visual acuity has been identified such as:
Achromatopsia - congenital cone deficiency.
Albinism - lack of pigment, translucent cornea, abnormal decussation of nerve fibres and associated with nystagmus
Macular degeneration.
Nystagmus.
Also the term may be used where the reduction in vision is reversible. i.e:
Tobacco amblyopia.
Other toxins.
Causes of truly organic amblyopia have been suggested but disputed:
Transient retinal haemorrhages at birth - follow up of series showed no detriment to visual acuity.
Malorientation of retinal receptors - unconfirmed.
What do you do if the amblyopia doesn’t respond to treatment?
A characteristic sign of amblyopia is that it responds to treatment but if it doesn’t it requires further investigation.
If not responding to treatment this will be organic amblyopia or a pathology that isn’t amblyopia.
However, Meridional can be slow to show improvements and need to ensure that their meridian is correct in their glasses. If there’s no improvement within 9 months this is where worry should occur. Find in anisometropia this can improve quickly with glasses alone and then can be pushed further with atropine/patching but no improvement we need to investigate the reason for this; need to ensure they’re following the correct treatment plan (that the kids and parents are saying the same thing also).
What is Toxic Amblyopia? & what are the types?
Toxic -
VA 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 very sensitive to tobacco – can cause optic neuritis (swelling of optic nerve).
Nutritional amblyopia -
Caused by deficit of vitamin B12. Often seen in alcoholics & with extreme diets. Complete recovery is possible with improved diet – but if deprivation is too prolonged VA damage permanent.
Alcohol amblyopia –
Painless bilateral loss of vision. Toxic effects of alcohol cause optic neuropathy. Alcohol depletes the body of nutrients – often associated with B1 deficiency
How do we investigate and diagnose amblyopia?
- Case History
- Fundus and media check
- Refraction
- Visual acuity
Crowded if possible
Interpret grating acuity with care
May include pinhole - Contrast sensitivity
Strabismic & anisometropic amblyopias may have mkd losses of CS especially at higher
spatial frequencies - Cover test – fixation pattern
- 10Δ prism test
- Uniocular fixation
- Neutral density filter test
Eyes with strabismic amblyopia may VA with
neutral density filters less than fellow
eye/other amblyopias
An initial examination should include VA, fixation, refractive error, sensory and motor fusion, stereoacuity, accommodation, ocular motility and a thorough ocular health evaluation. Amblyopic patients often perform poorly on crowded VA charts compared to their single-letter/line scores. On follow-up examination you must avoid obtaining an artificially high or low VA measurement. VA should be done before and after cycloplegia.
Which eye is more commonly affected in amblyopia?
Anisometropic amblyopia, with or without strabismus, occurs more often in left eyes than right eyes
59% left amblyopes among 2635 participants.
Strabismic amblyopia 50% left eye, 50% right eye
What is the aim for management of amblyopia?
To achieve and maintain maximum visual acuity
How do we manage amblyopia?
- Remove any cause for stimulus deprivaton and correct refractive error. Allow period of time (up to 18 weeks) for refractive adaptation
- Choose and agree a regimen of occlusion / atropine penalisation therapy
- Discontinue occlusion / penalisation therapy when maximum acuity is achieved and observe for stabilisation of acuity
- Go back to (2) if VA is not maintained
What must we consider in the treatment of amblyopia?
Critical / sensitive periods – what is the patient’s age?
Correction of refractive error
The refractive adaptation period (to see if glasses improve it alone or if further treatment is needed)
Further treatment
What is occlusion?
Reduction or prevention of visual stimulation by the embarrassment of vision. This may be full time or part time.
What are the types of occlusion?
Total light occlusion: Form and light is prevented from entering the eye.
e.g. Elastoplast, Opticlude, Coverlet, Extension patch Eze-patch
Total form occlusion: Excludes form but not light.
e.g. Blenderm, transpore on glasses.
Partial form occlusion.
e.g. Clear fablon, sellotape, soap, Bangerter or lens (optical penalisation).
(Ensure visual acuity of the good eye is reduced to below that of the amblyopic eye).
Optical penalisation
Usually +3.00DS or larger lens in front of non-amblyopic eye
What is cycloplegic treatment in amblyopia?
Atropine penalisation of non-amblyopic eye.
Two drops of cyclopentolate 1% are used in children >1yo and 0.5% in children >12yo for cycloplegic retinoscopy and refraction. If there are concerns regarding the retina then mydriatic drops should be used which give both cycloplegia and mydriasis.
Must consider both refractive error before and after cycloplegia, the amount of anisometropia after cycloplegia and should consider the patient’s ocular alignment.
What are the side effects of cycloplegic treatment?
Ointment is absorbed more slowly than drops and so has a lower risk of side effects.
Common side effects are:
- Allergy
- Dry mouth
- Flushing
- Glare due to dilated pupil
What’s the history of atropine?
Historically it was thought that atropine penalisation was only suitable for moderate and mild amblyopia (i.e. visual acuity (VA) of 6/30 Snellens (Sns) (0.7 LogMAR) or better as per PEDIG (Pediatric Eye Disease Investigator Group) definitions.
This is because atropine was thought to give insufficient blur to the better eye (i.e. not worse than 6/30 Sns / 0.7 LogMAR) to cause the amblyopic eye to dominate the visual input to the visual cortices.
Thanks to some thorough and long-term research by PEDIG we now know that this is not the case. In their 2010 study PEDIG showed that VA in the amblyopic eye in children aged 3-12 years with severe amblyopia (VA 6/37.5 – 6/120Sns / 0.8 – 1.3 LogMAR) could be significantly improved by atropine therapy and this was by instilling atropine on weekends only.
What instructions should be given regarding atropine ointment?
- Gently pull down the lower lid
- Drop one drop into the area between eyeball and inner part of lower lid
- Allow the child to close their eyes!
- Apply gentle pressure to the upper and lower lids near on the nasal side to facilitate punctal occlusion and minimised any systemic effects
- Wipe away any excess ointment which has oozed out from between the lids
- Do not allow child to rub eye and put fingers in mouth or eat the ointment!
- Wash hands
- Keep the drops locked away from reach of the child
- Ensure patient is familiar with correct disposal guidelines – medicines should not be placed in the bin but instead returned to clinic or the nearest pharmacy
- Give written instructions if these are available in the clinic to underline the information you have given – a bottle of atropine eye drops if ingested is potentially fatal. Fatalities have been reported Loewen and Barry (2000)
- Parents should be told that the pupil will dilate; the child may find bright lights troublesome (e.g bright sunlight) and the normally straight eye will be seen to turn and fellow eye will be used instead.
Can you combine atropine and occlusion?
Yes!
Optical Penalisation can be used in conjunction with atropine to reduce visual acuity in the better eye more, or to encourage use of one eye for near and one eye for distance.
How long does atropine work for?
The effect dilates the pupil (up to 10-14 days) and paralyses accommodation (up to 2-3 days), thus reducing visual acuity for near and a little for distance as some latent hypermetropia becomes manifest
What is the process for starting and ending occlusion therapy (patching or atropine)?
1) Select patient for treatment.
2) Remove any cause for stimulus deprivation and correct refractive error. Allow time for refractive adaptation (VA may improve up to 18 weeks following refractive correction, Stewart et al, 2004)
3) Choose an appropriate form of occlusion therapy.
4) Discontinue occlusion when maximum acuity is achieved and observe for stabilisation of visual acuity.
5) Wean the occlusion down i.e. from 2 hours daily, to 1 hour daily, to half an hour daily, as this has been shown to produce more stability of the improved VA (Holmes et al, 2007).
5) Where visual acuity is not maintained go back to (2).
How do you choose the type of occlusion and the length of wear?
Latent Nystagmus:
As this becomes manifest as light is prevented from entering one eye, atropine may be better for this group. An alternative is partial occlusion may be given.
Latent or Intermittent Squints:
Where decompensation may occur, atropine or reduced occlusion regimens may be preferable.
In most patients, atropine and patching are equal first line treatments (see PEDIG literature below) and it should be patients and parent/carer choice which treatment is chosen
The younger the child the more careful you need to be about both atropine and occlusion because reversal amblyopia becomes more of a risk
How can Binocular Video Games be used in amblyopia treatment?
Dichoptic video game presents different stimuli to either eye, with greater stimulation to the amblyopic eye.
Gao et al. (2018) - Found no differences in VA between the placebo and dichoptic video game
Knox et al. (2012) - smaller improvements of 1 line LogMAR after playing such games for 1 week one hour daily in eight amblyopic children.
Birch et al. (2015) - that a dichoptic ipad game in pre-schoolers played four times a week for four weeks, produced a one-line improvement in amblyopic eyes, whereas the sham ipad game did not
What is a historical management of amblyopia?
CAM visual stimulator - physiologically based treatment with stimulation of the amblyopic eye by grating rotating in the background whilst drawing. Limited advantage however.
Can you be admitted to hospital for monitored occlusion?
Yes. When severe amblyopia that would pose risks at home or in instances of poor compliance.
Where difficulty carrying out occlusion is this issue patient’s were previously, rarely admitted to a children’s ward and occlusion supervised by a paediatric nurse - rarer now, but possible after congenital cataract where VA drastically different between the eyes.
When FTTO (full time total occlusion) how often should visits be?
When FTTO (full time total occlusion) visits should be 1-2 weeks
Why should visits be every 1-2wks during FTTO?
Where the patient is a baby or older child, where decompensation of a deviation may occur or where atropine is being used.
When PTTO (part time total occlusion) how often should visits be?
Less frequently; 3 - 8 weeks
Why are visits less frequent in PTTO?
May be suggested where occlusion is part time or partial and there is no danger of intractable diplopia, decompensation of a latent deviation or occlusion amblyopia.
What advice should you give parents when their child is prescribed occlusion?
Wearing a patch reduces the field of vision as well as making the child cope with possibly markedly reduced visual acuity. Care should be advised on stairs, riding bikes, crossing roads, falling over toys etc. Some activities such as riding bikes, roller skating may be banned! for safety reasons if visual acuity is very poor.
What advice should you give parents when their child is prescribed atropine?
If atropine occlusion is given, warning about side effects should be given. In cases where patients are allergic to the drug they will become hot, flushed, dry mouthed, and may vomit. If the drug is ingested hallucinations can occur and if enough ingested it can be fatal.
When should you discontinue occlusion/atropine penalisation?
- When visual acuity is equal on a crowded test.
- When free alternation occurs
- When no further improvement can be gained.
- If occlusion has been part time or partial, full time total may be tried. If atropine has been twice weekly, daily atropine may be tried before giving up (provided patient is suitable).
- Discontinue patching if there is a reduction in density of suppression or patient reports having diplopia as there is danger of developing intractable diplopia.
When is recurrence of amblyopia more common?
Evidence has been presented (that where occlusion has been worn for long periods per
day (6 or more hours) the risk of recurrence is reduced by reducing occlusion to 2hrs a
day prior to stopping (PEDIG, 2004).
The risk of recurrence is higher where there has been greater improvement (Holmes et al., 2007).
One of the biggest challenges is the chance of recurrence after completion of treatment. A study of moderate and severe amblyopia treatment found approximately 25% of patients under age seven had a recurrence of amblyopia within the first year of stopping treatment, and children ages seven to 12 had a 7% chance of recurrence (worsening of two lines of visual acuity). This recurrence is more common in patients with severe amblyopia who went from six hours of patching per day to no patching
When should you not use occlusion?
- Patch Allergy
- Eye Infection
- Pathological causes of reduced vision
- Failure of previous treatment
- Physically or mentally disabled child
- Emotionally upset by occlusion!
- Social problems e.g. learning to lip read
- Latent nystagmus
- Decompensating deviation
- Terminal diagnosis
- Emotionally upset by occlusion
When should you occlude with care?
- Patients over 8 with manifest deviations
- Possibility of Decompensation.
- Nystagmus – but why not try atropine?!
- Very young patients – at higher risk of reverse amblyopia – half an hour daily in under one- year olds unless uniocular dense cataract removed
When should you not use atropine?
- Any heart condition (including Down Syndrome who have systemic heart disorders)
- Anyone light sensitive
- Any history of convulsions
- Known atropine allergy
- Bupthalmos
- Microcornea
- Low level of vision (>0.8DS)
- Family not on board (ingestion can be fatal)
- Using parafoveal fixation - there’s evidence to support patching to return to the fovea but this hasn’t been done with atropine
- Age - if at the end of suppression zone we don’t want them to develop irretractable diplopia
- How much school work they have as patching with low vision can impede them
- History of acute angle closure glaucoma (extremely rare in children without buphthalmos or microcornea)
- Less than 12 months old – neonates are at greater risk of toxicity from atropine, even reduced dose and at much higher risk of reverse amblyopia
- Under four year olds should be given atropine with care as increased risk of reversal amblyopia (Hainline te al, 2009)`
How can residual amblyopia be a challenge to treatment?
Residual amblyopia is another treatment challenge, considering vision does not improve sufficiently with one treatment for some patients. If the patient is currently patching for two hours, increasing patching to six hours per day may help improve visual acuity and treat residual amblyopia. Another option is to switch from patching to atropine or vice-versa to see if acuity improves.
What are some general hinderences to the success of amblyopia treatment?
Risk factors for failure to restore vision include age at which treatment for the condition started (later treatment tends to have a worse outcome), deprivation amblyopia, and poor initial visual acuity.
What are some risks associated with patching treatment?
- Overly aggressive amblyopia therapy (especially in younger patients) can produce reverse amblyopia of the sound eye.
- A new strabismus or a decompensation of an existing strabismus can also occur.
- Patches can be irritating to the skin, and the skin underlying the patch can become hypopigmented relative to the rest of the facial skin.
- There is also potential social stigma associated with wearing the patch to school in some cases.
What are some of the risks associated with Atropine?
- Atropine use can cause side effects related to the use of this medication: flushing, rapid heart rate, mood changes (uncommon) and photophobia (common) would be examples of side effects occurring with the use of this medication.
- Reverse amblyopia can also occur with Atropine use as can cause decompensation of existing strabismus or development of a new strabismus. Cases of reverse amblyopia (when the good eye is 3 logMAR units worse than VA of the amblyopic eye after treatment) are infrequent and usually mild. Most cases resolve with discontinuation of treatment.
What influences prescribed drugs?
E.g babies sleep a lot so 6 hours might be their whole waking hours
- Mild Ambly – patching 2hrs or atropine
- Mod Ambly – patching 2 hrs or atropine
- Severe Ambly – patching 6 hours or atropine
- Very severe ambly. – Not atropine. Dependent on age for patching 6 hours, but if say 0-6mo then do fewer hours, start with 1 hour and see them more frequently due to few waking hours, 6 – 12mo = 2hrs, 1 – 2yo = 3hrs = younger they are the more cautious we want to be. Can see them more regularly and then increase if needed. Do VA tests only if need be.
What influences prescribed dosage?
- 6 hours daily occlusion produces same effect as full time occlusion (patients were 3-7 years with SEVERE amblyopia (visual acuity between 6/30 and 6/120), & same effect in all levels of amblyopia in older children (7-12 years) (2008)
- 2 hours daily patching produced a VA improvement similar to that of 6 hours in
moderate amblyopia (visual acuity better than 6/30) - 2 hours daily patching combined with one hour of near visual activities improves moderate to severe amblyopia in children 3 to 7 years old more than glasses alone
Weekend atropine produced similar levels of improvement to daily atropine for
moderate amblyopes (6/12 – 6-24) (2004) - Weekend atropine can improve VA in the amblyopic eye in children aged 3-12 years with severe amblyopia (VA 6/37.5 – 6/120) (2010)
- Atropine 1% is as effective as occlusion for VA’s of 6/12 – 6/30 Sns (2006)
When would FTTO be used?
Rarely so but used most in stimulus deprivation amblyopia & dense amblyopia
What has been shown about parents from low-income families in relation to amblyopia treatment?
Where difficulty carrying out occlusion is this issue patient’s were previously, rarely admitted to a children’s ward and occlusion supervised by a paediatric nurse - rarer now, but possible after congenital cataract where VA drastically different between the eyes
How successful is amblyopia treatment?
- Successful treatment outcome achieved in 63-83% of patients
- Success affected by VA at first visit & 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 / number of lines VA
improvement)
- 44 times more cost effective than cataract
When should you discontinue occlusion?
- When VA is equal on a true linear test
- When free alternation occurs
- When no further improvement can be gained
- Reduction in density of suppression with
danger of intractable diplopia
What are the possible treatments for Eccentric fixation?
- Direct Occlusion
- Indirect (Inverse) Occlusion
- Red Filter Treatment
- Pleoptics e.g. Bangerter’s Method, Cupper’s Method & Haidinger’s Brushes
- Surgery
What is Direct Occlusion in treatment of eccentric fixation?
Where the child is young improvement with full time total to light occlusion is hoped for. Direct occlusion is usually tried as the initial treatment.
What is Indirect (Inverse) Occlusion in treatment of eccentric fixation?
Where no response is gained from direct occlusion and where the eccentric fixation is fixed, the amblyopic eye is occluded until the eccentric fixation is disrupted and fixation becomes wandering. Direct occlusion can then be used alone or in combination with another form of treatment e.g. red filter drawing. In order to avoid re-establishment of the eccentric point, if direct occlusion is only tolerated part time, indirect occlusion is continued for all other waking hours.
What is Red Filter Treatment in the treatment of eccentric fixation?
A red filter (Kodak Wratten 92) placed over the amblyopic eye encourages the foveal area to be used (because red is supposed to just stimulate cones). This will improve fixation and direct occlusion is then used to further the improvement in visual acuity. Treatments are recommended for 10 to 30 minutes daily and combined with inverse occlusion.
What is Pleoptics treatment in the treatment of Eccentric Fixation?
This method was previously frequently used but now is carried out in only a few centres for adults with loss of vision in their good eye, and seldom on children. Treatments have to be daily. The principle is to stimulate the foveal area.
Bangerter’s Method: Retina is dazzled with fovea protected thus eliminating eccentric point and fovea then stimulated.
Cupper’s method: An after image is produced around the fovea and the patient then asked to fixate an object so that it is covered by the after image. The fovea is thus re-educated.
Haidinger’s brushes – ensures foveal fixation
What is surgery used for in the treatment of eccentric fixation?
Surgery: to place the eye in a more central position has been advocated or to overcorrect the deviation to disrupt the eccentric point.
What are ‘X’ or sustained ganglion cells?
Ganglion cells in the central area of the eye responding to well focused stable images and only pick up stimuli within a small area (small receptive fields). Parvocellular cells respond best to them.
How are ‘X’ cells affected in amblyopia?
In Amblyopia they have poorer spatial resolution and ability to detect contrast (like at high spatial frequencies)
What are ‘Y’ or transient cells?
Ganglion cells which respond to defocused and moving objects. They have a large receptive field. Magnocellular cells respond best to them.
How are ‘Y’ cells impacted in amblyopia?
Although some small changes have been reported in these cells in amblyopia, they are much less than the differences reported in the ‘X’ cells.
How are parvocellular cells affected in amblyopia?
In amblyopia changes in the parvocellular layers (3, 5, 6) relating to the affected eye are found such that these cells have a lower resolving power and a loss of contrast sensitivity function at higher spatial frequencies. Histological changes accompany these neurophysiological effects, and the cells appear shrunken
How is the visual cortex affected in amblyopia?
About 80% of cells in the visual cortex normally respond to input from either eye at separate times, however, where monocular input has been reduced, this falls to only 7% in the amblyopic eye. If the reduced input is bilateral the percentage of cells responding to stimulus from either eye is 41%.
What are amblyopiogenic factors in the critical period?
During this time, the visual system is susceptible to known amblyopiogenic factors: form deprivation, optical defocus, and misalignment of the eyes. If left untreated, the two amblyopiogenic mechanisms, form deprivation and abnormal binocular inhibition, cause a progressive reduction of visual acuity until approximately 6-8 years of age, at which time visual acuity stabilizes.
- Light deprivation of the entire retina.
- Form vision deprivation of the fovea.
- Abnormal supraretinal interaction between dissimilar contours presented to corresponding retinal areas. (Abnormal binocular interaction).
LOOK AT THE AMBLYOPIA TUTORIAL WORK
Aged 6 years
Cycloplegic Refraction:
R +1.00 L +1.00
No glasses prescribed
Fundi and media healthy (checked back of eye and the vitreous and lens, anterior chamber etc)
VA u/a R 0.100 L 0.800
Crowded logMAR
CT u/a
N Moderate left esotropia, slow
to take up left fixation
D Moderate left esotropia
PCT u/a N 30Δ BO
D 25Δ BO
What amblyopia do they have? How would we treat it?
Strabismic
Strabismic deviations are initially treated with refractive correction but may require penalisation therapy such as occlusion or atropine in the better seeing eye (non-amblyopic/fixing eye).
Patching for two hours per day is recommended for patients with moderate amblyopia (0.6 or better visual acuity), while patching for six hours is recommended for patients with severe amblyopia (0.7 or worse visual acuity). Our patient falls into the severe range.
How do you assess the risks associated with patching/atropine?
- Do they have a skin condition or injury/open wounds around their face
- Are they old enough to withstand atropine drops?
- Do they have a dense strabismic amblyopia and under 4yo who are hypermetropic? This would place them at higher risk of reverse amblyopia when on atropine
- Is their suppression dense enough to withstand the patching and not cause diplopia when the patch is removed? Want to check we’re not disrupting their suppression during treatment by testing at each visit.
- Patching can affect BSV so test for BSV at each session and do not start occlusion if they have BSV
- Length of time wearing the patch
- Follow up – dense amblyopia = first visit 2-3wks and then 4wks-6wks after this
- Test to see BSV if they suppression, have ARC or diplopia (most likely to have suppression because ARC unlikely due to size, diplopia should be reported in the CT so likely suppression). We would want to know the density and area of the suppression scotoma.
How can we minimise amblyopia treatment risks?
Monitoring density of suppression during treatment. Monitoring treatment being undertaken. Monitoring side effects of patching or atropine. Monitoring QoL or impact of treatment on child.
* Regular meetings with the orthoptist on a 4-6 weekly basis ensure that reverse amblyopia isn’t occurring or decompensation of an existing strabismus by measuring at each appointment
* To educate the patient and their parents/guardians to ensure they understand the risks associated with the treatment (i.e. keeping atropine away from children, when to stop treatment and the side effects) and the importance of adhering to the treatment
* Ensuring that the correct treatment is chosen based on the child’s risks
Age 4
Cycloplegic Refraction:
R +6.00 / +0.75 x 90
L +1.00 / +0.25 x 180
Glasses prescribed 4/52 ago (4 out of 52 weeks) and worn FT since
Fundi and media healthy when checked 4/52 ago
VA c gls R 0.550 1 L 0.050 3 Uncrowded logMAR
s gls R0.700 2 L 0.075 4
Crowded logMAR (Sn equivalent)
CT c gls
N Small/mod right esotropia
D Small right esotropia
s gls
N Moderate right esotropia
D Small/mod right esotropia
Convergence
c gls with reducing deviation to 8cm, then RE diverges without diplopia
Bagolini glasses c gls
N right suppression
D right suppression
PCT
c gls
N 20Δ BO
D 15Δ BO
s gls
N 25Δ BO
D 20Δ BO
Why might the order of CT’s being conducted be important?
It can be useful to know due to the amount of time that the eyes were dissociated before being tested and whether cooperation/concentration may be a factor in the results.
May have started crowding due to the age being ready for it so important to understand the order of these or why they began
Age 4
Cycloplegic Refraction:
R +6.00 / +0.75 x 90
L +1.00 / +0.25 x 180
Glasses prescribed 4/52 ago (4 out of 52 weeks) and worn FT since
Fundi and media healthy when checked 4/52 ago
VA c gls R 0.550 1 L 0.050 3 Uncrowded logMAR
s gls R0.700 2 L 0.075 4
Crowded logMAR (Sn equivalent)
CT c gls
N Small/mod right esotropia
D Small right esotropia
s gls
N Moderate right esotropia
D Small/mod right esotropia
Convergence
c gls with reducing deviation to 8cm, then RE diverges without diplopia
Bagolini glasses c gls
N right suppression
D right suppression
PCT
c gls
N 20Δ BO
D 15Δ BO
s gls
N 25Δ BO
D 20Δ BO
What type of amblyopia does this patient likely have?
Anisometropic (caused by having a distinct refractive error in one eye, in this case the right eye).
&
Strabismic - However, it could also be strabismic. This patient has a small to moderate strabismus (ET) with right suppression during convergence testing and in Bagolini glasses there was right suppression even with glasses suggesting that there is a Constant ET with accommodative element as on PCT with glasses their angle of deviation reduces slightly
How is Anisometropic amblyopia defined?
For anisometropia this would be anything of 1.0-1.5DS difference in hypertropia, 2D in anisoastigmatism and 3-4D in ansiomyopia
Why should refractive correction be the primary treatment in anisometropia?
Studies have shown that some patients with anisometropic amblyopia may show improvement in visual acuity while wearing their glasses full-time, without concurrent patching. A retrospective study by Steele et al. showed that one third of the patients with pure anisometropic amblyopia resolved without the need of occlusion therapy. The length of recovery time was directly proportional to the severity of amblyopia. The mean time to resolution was 5.8 months[9]. In 2006 a prospective study by PEDIG reported that 27% of children with anisometropic amblyopia aged 3 to 6 resolved with spectacles alone. Visual acuity continued to improve in 48% of patients beyond 5 weeks[10].
Age 5 years
Cycloplegic Refraction:
R -1.00 / +0.25 x 110
L -1.00 /+3.75 x 110
Glasses prescribed 6/12 ago (6 months of 12 months) and worn FT since
Fundi and media healthy at last check
VA c gls
R 0.075
L 0.275
Crowded LogMAR
CT
c gls & s gls
N very slight exophoria with rapid recovery
D very slight exophoria with rapid recovery
Bagolini glasses c gls
N BSV response
D BSV response
Convergence c glsto 6cms, well maintained
20Δ prism reflex test c gls
o/c with either eye with good recovery
Frisby c gls
110” of arc at 50cm
What type of amblyopia does this person have?
Meridional Amblyopia
How do you diagnose Meridional Amblyopia?
Astigmatism results from having a cornea that is not perfectly spherical. An empty box means there is no astigmatism and your eyes are perfectly spherical. A low number, like 0.25, means your eyes are not quite round and a higher number, like 3.00, means your eyes are quite oval
Resolution of eye is reduced in selective meridians as a result of uncorrected astigmatism * Cylinder >1.5D is considered amblyogenic
The x90 or x180 refers to against the rule (steepest meridian is horizontal) and with the rule (steepest meridian is vertical)
Boy aged 31/2 years old
Glasses prescription:
R +6.50 L +6.50
Glasses worn for 4 weeks
Fundi and media healthy
VA c gls
R 0.450 1 L 0.450 2 Crowded LogMAR
CT c gls
N small exophoria with rapid recovery
D small exophoria with rapid recovery
s gls
N slight exophoria with rapid recovery
D slight exophoria with rapid recovery
Bagolini glasses
c gls
N BSV response
D BSV response
Convergence c gls to 6cm
20Δ prism reflex test c gls o/c with either eye with good recovery
Frisby c gls 110” of arc
What type of amblyopia is the patient most likely to have?
High degree of hypermetropia that is not fully corrected with glasses = Ametropia /Isoametropic/Bilateral Amblyopia
How do you treat Ametropic amblyopia?
Glasses full-time
Visual therapy/ocular exercises
In symmetric bilateral cases, treatment consists of addressing the etiology of the diminished vision.
Good potential for improvement compared to later correction of refractive error.
Needs FT wear of correct glasses. Refraction will be monitored over time and glasses updated as necessary.
Frequent visits to monitor VA.
Could have fundus and media check repeated if concerned VA not improving.
Could also discuss further investigation – EDT’s.
How do you treat Anisometropia?
Treatment for anisometropia can involve corrective lenses or surgery. Corrective lenses are only good for those with a difference between their eyes of 4D or less. Children under 12 and those with severe anisometropia are generally advised to use contacts, while others can often use glasses for correction.
Patching etc.
The preferred method of treatment for patients with anisometropia is corrective surgery, which can sometimes permanently solve most or all of the problem. Typical surgical therapies include:
Refractive corneal surgery. Used to improve the cornea’s refraction of light, this surgery can correct unilateral myopia, hypermetropia, and astigmatism.
Removal of the crystalline lens. The crystalline lens is your eye’s natural lens. For some people, removing the lens can actually improve their overall vision. The sight in that eye can then be adjusted with special glasses or further surgeries.
Intraocular lens implantation. Intraocular lens implantation (IOL) is a relatively common surgery for those with a cataract or astigmatism in their eye that is seriously impacting their life. While there are several variations of this surgery, the eye is generally cut precisely so a doctor can break up the natural lens. Then, a plastic lens is put in its place to correct vision.
Phakic IOL. This intraocular lens implantation is similar to the above surgery, but it does not remove the crystalline lens. Instead, the intraocular lens is placed in the eye with the natural lens. The two will then work together to improve vision.
