Paeds: Amblyopia 1 - Week 3

Question 1

Which type of acuity chart is the most sensitive to amblyopia?

Answer 1

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)

Question 2

How can we test acuity on children: 
A: Under 2.5yo
B: 2.5-3.5yo
C: 3.5-5.5yo
D: 5.5+

Answer 2

A: No chart/Fix and follow
B: Picture chart to estimate
C: Shape chart with logMAR format
D: letters

Question 3

What feature of an acuity chart do amblyopes struggle with? When does this reach maximal effect?

Answer 3

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).

Question 4

How does contour interaction vary down a snellen acuity chart? What does this say about the ability of the snellen chart to detect amblyopia?

Answer 4

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

Question 5

What is fix and follow?

Answer 5

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.

Question 6

When may a Sweep VEP be used?

Answer 6

to determine visual acuity in a 6mth-3yo child if concerned the child might be blind or have low vision

Question 7

At what distance is acuity testing in a child over 3yo usually done?

Answer 7

3 metres

Question 8

List the 6 most common preliterate acuity charts used on children

Answer 8

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)

Question 9

Is tumbling E a good preliterate chart? Explain

Answer 9

Not particularly. Children under 6 are poor at identifying directions

Question 10

How good are Allen pictures at measuring acuity?

Answer 10

Fine if acuity rubbish but poor when acuity is good. Can’t really trust the numbers on this one so be careful.

Question 11

How good is Sheridan Gardiner at measuring acuity?

Answer 11

“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

Question 12

How good are kay pictures in measuring acuity?

Answer 12

Actually decent. Second best choice after lea symbols.

Question 13

What are 2 advantages of kay pictures compared to lea symbols?

Answer 13

Can test children a year before lea (so @ 2-2.5yo)

Less developmental noise than lea

Question 14

List 2 advantages of Lea symbols

Answer 14

Good correlation (0.85) with snellen (best of the preliterate tests)
Most sensitive to amblyopia (cf other preliterate tests)

Question 15

List 4 amblyogenic factors

NB: you need an amblyogenic factor for a patient to have amblyopia

Answer 15

STRAB
Anisometropia
High bilateral refractive error
Media opacity or ptosis (rare)

Question 16

What should you do if you suspect amblyopia but can’t find an amblyogenic factor?

Answer 16

refer to ophthamologist

Question 17

How should amblyopia typically respond to treatment in children?

Answer 17

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)

Question 18

What type of pathology should you rule out when suspecting amblyopia? Provide examples (5)

Answer 18

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

Question 19

How can we assess for pathology in young children? (4)

Answer 19

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)

Question 20

List 5 prognostic indicators for amblyopia

Answer 20

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

Question 21

What will amblyopic patients with eccentric fixation end up with as a final acuity after occlusion?

Answer 21

Poor acuity. Generally between 6/30-6/60

Question 22

What is the primary and secondary purpose of amblyopia treatment?

Answer 22

Primary: improve monocular function (normal VA + fixation in each eye)
Secondary: improve binocular function (normal fusion at all levels)

Question 23

What treatment will amblyopia respond best to?

Answer 23

Full plus worn full time

Question 24

How does occlusion treatment work?

Answer 24

Occlude dominant eye: forcing other eye to take up fixation and reduces dominant eyes inhibition of amblyopic eye

Question 25

How long does full time occlusion take?

Answer 25

Generally good response in 3 months. Child will however need 6 months to get majority of effect.

Afterwards, improvement slows, (it’s asymptotic: starts fast then slows)

Question 26

For what age should occlusion treatment be considered for amblyopia?

Answer 26

Generally 12yo or younger. Older children (high school) tend to do worse (re response and compliance) but could still try.