Amblyopia Flashcards
What is a visual screening?
A child is screened for eye problems
What is the purpose of visual screening?
Detect defects early so treatment done early before they become permanently visually impaired
When is the first ever screening that happens in a child’s life?
When they are born before they leave hospital
When are they next checked?
By doctor at 6 weeks
What exactly does the screening at this early stage entail?
Red reflex and eye development checked
What happens if a problems is found?
The child is referred for a full eye test
Who can detect strabismus?
Parents, health visitors, doctor
Which children should be more closely monitored?
FH of strabismus/amblyopia/refractive error
Child with systemic disease, hearing loss, learning difficulty, premature/low birth weight
What is a pre-school vision screening?
At age 4-5, child has a visual screening at school but this is not done everywhere
Who are the children screened by at pre school screening?
By orthoptists or
By professionals trained by orthoptists
What is the gold standard test at this screening?
Linear logMAR
What do you do before you being testing a child’s vision?
- Gain consent parent (opt-in/opt-out)
Gain consent - Explain the test procedure to the child.
Have a quick practice - Check child is able to match or name the letters at NEAR
How should you check the child’s vision?
Avoid pointing inside box, test each eye monocularly, always start with the RE unless they have strabismus, if poor result with first eye then quickly move on to second eye
If they have glasses check VA with them
What test chart can be used for 3.5-5 yr olds?
Crowded keeler logMAR
What distance for Crowded keeler logMAR?
3m
How many letters are used Crowded keeler logMAR??
Six letters are used X V O H U Y.
How many letters on each line of Crowded keeler logMAR?
4 letters surrounded by crowding bars
What is the score of each letter with Crowded keeler logMAR?
0.025
What are the advantages of Crowded keeler logMAR?
Easy to use, durable, 2 flip over books and matching card.
What’s the point of 2 books for Crowded keeler logMAR?
Incase they memorise it you have another book, use 1 book for each eye)
How do you conduct the Crowded keeler logMAR?
Test the right eye first using screening card S2
If the child is unable to identify the first letter on the S2 screening card, moves to screening card
S1
Test all letters on start line
proceeds to smaller / larger lines as necessary
2 letters per line must be correctly identified before testing smaller lines
Test all letters on the line where errors occur
tests all letters on 0.200 line if seen (testing can be stopped if this level of acuity is achieved)
correctly identifies the corresponding Keeler logMAR score, and records immediately after testing each eye
What should you ensure and observe for when conducting the test?
Ensure the child holds head straight during the test
observes the child during testing for abnormal head posture such as turning or tilting the head, or attempting to ‘peep’ from behind occlusion.
What is the main condition that screening is trying to detect and why?
Amblyopia because needs to be treated early
What others conditions you might detect?
Refractive error Strabismus Nystagmus Ptosis Muscle problem Cataract Anisocoria Rare pathologies: Coloboma, Leucocoria
What is amblyopia?
A form of cerebral visual impairment with reduced vision in one or both eyes, only occurs during critical period
What is the critical period?
Birth to 7-8 years old
How does amblyopia develop?
When we are born the visual pathway is not complete and develops as we grow up.
An interruption has occurred to the normal visual development during the critical period causing amblyopia
What can cause abnormal visual development?
Refractive error,
pathology,
strabismus
When is VA affected during childhood?
Development period, critical period and sensitive period
What is development period?
Birth to 3-5 years old
What is sensitive period?
Time of deprivation to teenage/adult yrs-can still treat but prognosis is less affective
What visual aspects does amblyopia affect, name 6?
Vision/Visual-Acuity
Contrast sensitivity
Depth perception
Difficulty with crowding
Motion perception
Visual distortion
Why should you treat amblyopia?
Affects quality of life-bullying
What lifestyle activities does amblyopia affect?
Driving: breaking distances and no. of accidents
Threading beads on a string
Does amblyopia affect education or employment?
Not really, statistics show no difference
What is a big risk of an untreated amblyope?
Risk of getting a binocular VI because if something happens to their good eye then both eyes gone
What is functional amblyopia?
Amblyopia, which is potentially reversible by occlusion therapy.
What are the 5 types of functional amblyopia?
- Strabismic amblyopia
- Stimulus deprivation amblyopia
- Anisometropic amblyopia
- Meriodonal ambylopia
- Ansimetropic ambylopia
What is strabismic amblyopia?
Occurs monocularly, occurs in CONSTANT manifest deviation (constant tropia),
Which type of tropia is strabismic amblyopia more likely to occur in?
ESOT as ESOT is more likely to be constant.
XOT often remains intermittent during childhood
What is stimulus deprivation amblyopia?
Occurs monoc or binoc.
When passage of light is obstructed by things like cataracts or ptosis which prevent clear formation of image. Binocular stimulus deprivation ambly may be caused by congenital nystagmus.
What is important to note in stimulus deprivation amblyopia?
Important to note how much pathology prevents clear image at the macula
What is Anisometropic amblyopia?
Occurs monocularly, amby in the more anismetropic eye, difference in ref error where one eye receives less visual input
What type of refractive error difference can cause anismetropic amblyopia?
The refractive error may be spherical and/or astigmatic difference.
What is Meridonal amblyopia (astigmatic)?
Occurs monoc with anismetropic amby or binoc with ametropic ambly.
A clear image is formed along more emmetropic axis and blurred among ametropic axis
What is Ametropic amblyopia?
Occurs binoc-high ref error in both eyes.
Why does high refractive error causes amblyopia?
High hyperopia (+5) -cannot be compensated for with accommodation and high myopia causes degenerative retinal changes
What is the first thing to do when investigating amblyopia?
History taking:
- What is the problem?
- What age did the problem start?
- Strabismus?-constant/intermitent/alternating
What other tests are fundamental in amblyopia investigation?
Refraction (cyclo 1% in children)
Ophthalmoscopy (elimante patholgy)
Would you prescribe a 1 year old with +1.50 in 1 eyes and plano in the other eye?
No, child will emmetropise but if it was +3.00 in 1 eye and +4.50 in. other eye then prescribe that
What does isometropia mean?
Oppsite of anismetropia
Both eyes have same refractive power
If a child has esot and a hyperopic rx what do you do?
Alway prescribe full hyperopic rx if they have esot no matter how small error
What is the normal VA for 4-5 yr olds?
- 087 (approx 6/7.5) +/- 0.10 log units for crowded
0. 010 (approx 6/6) +/- 0.10 log units for uncrowded LogMAR tests.
How should you measure child’s VA?
Use Log MAR
due to crowding
Measure near and Distance VA
With & without compensatory head posture (CHP)
What can you do if they have a manifest latent nystagmus ?
If manifest latent nystagmus may want to use spielman occluder
Why is it a good idea to measure contrast sensitivity for slightly older children (not practical in younger children)?
More sensitive measure than visual acuity
Affects are dependant on the type of amblyopia
Whys should you do cover test in amblyopia investigation?
In children VA testing is not always possible
When do you observe during cover test?
Note whether alternating unilateral deviation
Will the amblyopic eye hold fixation to blink
Central fixation versus eccentric fixation via corneal reflections (gross only)
Is the deviation constant or intermittent
What other tests should you do?
Ocular motility
(patients with incomitancy may be more likely to decompensate when you start occlusion)
Accommodation
Convergence
How do you check binocular status?
Cover test-recovery
Prism Fusion Range
Stereopsis
What should you ensure on prism cover test when measuring size of deveiation?
Ensure occlusion is not increasing size of deviation (risk of decompensation so stop treatment)
What is sbsia used for?
Sbisa bar (in patients with suppression): Do it with all strabismic amblyopes over the age of 5 years old, to prevent intractable diplopia
If patient has reduced VA, does that automatically mean amblyopia?
If no amblyogenic risk factor then probably not amblyopia
What else can it be then?
- incorrect v-a (no cooperation on that day)
- incorrect refraction
- mild pathology
What do you do in the case that VA is reduced and you thing it’s not amblyopia?
- Repeat V-A assessment
- Repeat BV assessment (cover test)
- Repeat refraction
- Repeat fundus and media examination
