1. Acuity Testing in Children and how to cope with hysterical vision
Created on behalf of NHS NES as supplement to workshops on binocular vision and additional techniques.

2. Observations Navigation in clinic / reaching for quiet small toys
Holding new toys close for inspection
Eye contact – often avoided in autistic spectrum
Photophobia

3. Observations Obvious squint Alternating – VA equal
Fixation preference – suspect amblyopia
Infantile esotropia – amblyopia rare
Intermittent exotropia –amblyopia rare
Accommodative esotropia – VA may be good but hypermetropia may prevent habitual clear VA
Squint may be secondary to poor unilateral VA e.g cataract or retinoblastoma
Infants → esotropia
Older children / adults → exotropia

4. Qualitative Tests Fixation & following both eyes together
Infants prefer their mother’s face
Illuminated / moving small toys
Do not use noisy toys to assess VA
Smooth pursuit should be tested slowly
Jerky smooth pursuit does not mean low VA

5. Observations Nystagmus VA rarely better than 6/12 – often much worse
Amplitude of nystagmus not related to VA
Test VA uniocularly AND both eyes open
Use +6.0D lens as occluder if significant latent element
Near VA much better than distance
Test reading acuity at 1/3m and habitual near distance (even if 10cm)
Allow to adopt head posture during testing (usually face turn to fixing eye)

6. Observations Ptosis Lid ever obscuring pupil?
Using chin ↑ head posture
Using chin ↑ head posture on upgaze

7. Qualitative Tests Fixation
Fixation of deviating eye in manifest squint
Fixation should be brisk and accurate
Slow / delayed fixation often means low VA
Unsteady / no movement to fix indicates eccentric fixation and very low VA

8. Qualitative Tests Fixation preference Spontaneous alternation
Alternation after initial occlusion
Hold fixation through blink
Hold fixation up to blink
Hold fixation for few seconds
Hold fixation momentarily
Immediately return to originally fixing eye
Slow to fix
Unable to fix
EQUAL VA
DENSE AMBLYOPIA

9. Qualitative Tests
Cross fixation if squinting

10. Qualitative Tests
Cross fixation if squinting

11. Qualitative Tests
Cross fixation if squinting

12. Qualitative Tests Cross fixation if squinting
Tripartite field of fixation

13. Right eye fixing looking left 
Left eye fixing looking right 

14. Qualitative Tests Objection to occlusion
Look around an occluder / hand
Not significant if object to both eyes occluded
Different behaviour when occluded

15. Qualitative Tests Daylight / darkroom comparisons
Useful in delayed visual maturation / severe disability

16. Qualitative Tests
100’s & 1000’s

17. Qualitative Tests 10 vertical prism
Either alternate to look at diplopia or always fix with
uncovered eye if VA equal
Always fix with same eye if amblyopic

18. Qualitative Tests 10 vertical prism
Either alternate to look at diplopia or always fix with
uncovered eye if VA equal
Always fix with same eye if amblyopic

19. Qualitative Tests 10 vertical prism
Either alternate to look at diplopia or always fix with
uncovered eye if VA equal
Always fix with same eye if amblyopic

20. Qualitative Tests 10 vertical prism
Either alternate to look at diplopia or always fix with
uncovered eye if VA equal
Always fix with same eye if amblyopic

21. Qualitative Tests 10 vertical prism
Either alternate to look at diplopia or always fix with
uncovered eye if VA equal
Always fix with same eye if amblyopic

22. Qualitative Tests Optokinetic nystagmus
Asymmetrical monocular in infants under 4m and infantile esotropia
Rotate SLOWLY
Lab methods using different frequency gratings overestimate acuity

23. Preferential Looking (PL) Tests
Keeler /Teller Cards (with/without “puppet screen”)
Cardiff Acuity Cards
100s & 1000s / crumbs against light/dark backgrounds

24. Preferential Looking (Keeler / Teller Cards)

25. Cardiff Acuity Cards

26. Single Optotypes logMAR single letters
Sheridan Gardiner singles (not logMAR)
Kay pictures
Easier but overestimate VA in amblyopia
Make decision-making in young amblyopes difficult

27. LogMAR Tests More consistent than Snellen notation 6/60 = 1.0
6/6 = 0.0
Each line and letter difference standard over chart
Letters equally difficult
“Crowded”

28. Crowded LogMAR Tests Bailey-Lovie chart
Glasgow Acuity Test (Keeler) - at 3 metres
(Cambridge Crowding Cards)
LogMAR Kay Pictures - at 3 metres
LEA symbols
Sonksen test
replacing Snellen & Sheridan Gardiner linear tests at 6 metres

29. Linear Kay Pictures

30. Glasgow Acuity Test

31. Sonksen Test

32. Sonksen Test

35. Near Tests Reduced Snellen Maclure Bar Reading Book
Reduced linear Kay pictures
Reduced LEA symbols
With most VI children test at 1/3m and wherever they prefer to hold text

36. Acuity Equivalents

37. Refraction Cycloplegic refraction
Undilated retinoscopy – gross refractive error
media opacities
Bruckner reflex
Anisometropia
Gross astigmatism
“Mohindra” retinoscopy in dark

38. Crowding / Separation Difficulties
Present at threshold in everyone
Characteristics
Ends of rows clearer
Letters correct but jumbled up
Exaggerated ++ in amblyopia
?Worse if initial VA very low
Occlusion may improve singles acuity, but less for linear
VA may regress at end of occlusion
Record more details of VA e.g. 6/12, but crowding from 6/36

39. Electro-diagnostic tests
VEP, ERG,
Indicated when VA appears to be, or is suspected of being, reduced despite normal appearance on conventional examination e.g. Inherited retinal conditions
VEP acuity overestimates recognition acuity
Generally used in diagnosis
Occasionally used to monitor progress in children with congenital cataracts

40. Practical Tips
If occlusion likely to be difficult, do all both eyes open tests first
On first visit test likely better eye first
On subsequent visits test amblyopic eye first before co-operation lost
When moving on to more difficult test, try to do “old,” easier one, on same visit – especially if being occluded

41. Functional /”Hysterical” loss of vision
Children with genuine low VA are cautious in new situation of clinic, while these children enter normally
Relatively untroubled by apparently severe symptoms
Running their lives normally most of time

42. Functional /”Hysterical” loss of vision
Read VA chart very slowly from the top, not just from near threshold
Tricks
Cancelling + / - lenses – put up plus first
Testing VA at different distances
Use Bagolini glasses
If claiming unilateral loss use prisms to give diplopia
Watch pupil reactions for near – may dilate for text
Dynamic retinoscopy
Compare “tested” vs natural accommodation
Need good VA to get good stereoacuity – say TNO is a colour test
Check fundi and media carefully & refer for ophthalmologist opinion or scans if cannot improve VA

43. Functional /”Hysterical” loss of vision
Do not accuse of malingering / lying
Take it seriously
It “happens” to children and is common
Reassure child that their eyes are normal and it will get better with time
Speak to parents alone
Reassure, but ask parents to think about whether any cause they can think of
Bullying, dyslexia, anxiety, abuse
Offer a range of severity of causes
Be mindful of formal reporting procedures for child abuse