Paeds: Amblyopia 1 - Week 3 Flashcards
Which type of acuity chart is the most sensitive to amblyopia?
Log MAR acuity.
(snellen is not as sensitive, 65% of amblyopes will have acuity overestimated by 1-3 lines. So it’s really only an estimation)
How can we test acuity on children:
A: Under 2.5yo
B: 2.5-3.5yo
C: 3.5-5.5yo
D: 5.5+
A: No chart/Fix and follow
B: Picture chart to estimate
C: Shape chart with logMAR format
D: letters
What feature of an acuity chart do amblyopes struggle with? When does this reach maximal effect?
Contour interaction.
Max contour interaction occurs when letters are 0.4 of a letter apart from each other (i.e. 24 seconds of arc apart)
(**demonstrated with landolt C. So could also say 0.4 of a landolt C apart from each other).
How does contour interaction vary down a snellen acuity chart? What does this say about the ability of the snellen chart to detect amblyopia?
The letters are more crammed together as they get bigger (worse acuity). So worse VA lines will have more contour interaction.
Little interaction at 6/12 or better.
So snellen charts are not that good at detecting amblyopia
What is fix and follow?
For 6 month to 3 yo children, we assess how each eye fixates and follows a target. This is known as behavioral assessment of amblyopia.
When may a Sweep VEP be used?
to determine visual acuity in a 6mth-3yo child if concerned the child might be blind or have low vision
At what distance is acuity testing in a child over 3yo usually done?
3 metres
List the 6 most common preliterate acuity charts used on children
Picture charts (AO picts, Allen picts, Kay picts)
Tumbling E
Sheridan Gardiner
Letter matching charts
Broken wheel
Lea chart (closest thing to a logMAR chart)
Is tumbling E a good preliterate chart? Explain
Not particularly. Children under 6 are poor at identifying directions
How good are Allen pictures at measuring acuity?
Fine if acuity rubbish but poor when acuity is good. Can’t really trust the numbers on this one so be careful.
How good is Sheridan Gardiner at measuring acuity?
“Complete waste of time.”
Only useful in one case: if a child with 6/30 amblyopia acuity goes e.g. 6/12 with sheridan it means problem is amblyopia. But if still 6/30 with sheriden it means problem is NOT amblyopia - indicating patching very unlikely to work and you should seriously reconsider your amblyopia diagnosis
How good are kay pictures in measuring acuity?
Actually decent. Second best choice after lea symbols.
What are 2 advantages of kay pictures compared to lea symbols?
Can test children a year before lea (so @ 2-2.5yo)
Less developmental noise than lea
List 2 advantages of Lea symbols
Good correlation (0.85) with snellen (best of the preliterate tests)
Most sensitive to amblyopia (cf other preliterate tests)
List 4 amblyogenic factors
(NB: you need an amblyogenic factor for a patient to have amblyopia)
STRAB
Anisometropia
High bilateral refractive error
Media opacity or ptosis (rare)
What should you do if you suspect amblyopia but can’t find an amblyogenic factor?
refer to ophthamologist
How should amblyopia typically respond to treatment in children?
Should see VA improvement over time until at least to 6/12 acuity. 1 month of occlusion should give you at least a line of improvement (usually 3-4 lines)
What type of pathology should you rule out when suspecting amblyopia? Provide examples (5)
Optic nerve head asymmetries
Optic nerve pallor
Papilloedema
Macular dystrophies
Other retinal abnormalities
NB: be aware that sometimes child can have both pathology and amblyopia
How can we assess for pathology in young children? (4)
Ophthalmoscopy (direct, or BIO if young - less fixation dependent)
Retinal images (photo + OCT often possible if required)
Retinoscopy (for media opacities)
Slit lamp (usually if >3yo)
List 5 prognostic indicators for amblyopia
Cause (i.e. anisometropic, strabismic, anopsia)
Length of time amblyogenic factor has been present
Age of child @ time of treatment
Eccentric fixation
Level of refractive error and anisometropia
What will amblyopic patients with eccentric fixation end up with as a final acuity after occlusion?
Poor acuity. Generally between 6/30-6/60
What is the primary and secondary purpose of amblyopia treatment?
Primary: improve monocular function (normal VA + fixation in each eye)
Secondary: improve binocular function (normal fusion at all levels)
What treatment will amblyopia respond best to?
Full plus worn full time
How does occlusion treatment work?
Occlude dominant eye: forcing other eye to take up fixation and reduces dominant eyes inhibition of amblyopic eye
