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.

Observations

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

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

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

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)

Observations

• Ptosis • Lid ever obscuring pupil?

• Using chin ↑ head posture • Using chin ↑ head posture on upgaze

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

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

Qualitative Tests

• Cross fixation if squinting

Qualitative Tests

• Cross fixation if squinting

Qualitative Tests

• Cross fixation if squinting

Qualitative Tests

• Cross fixation if squinting Tripartite field of fixation

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

Qualitative Tests

• Objection to occlusion • Look around an occluder / hand • Not significant if object to both eyes occluded • Different behaviour when occluded

Qualitative Tests

• Daylight / darkroom comparisons • Useful in delayed visual maturation / severe disability

Qualitative Tests

• 100’s & 1000’s

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

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

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

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

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

Qualitative Tests

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

Preferential Looking (PL) Tests

• Keeler /Teller Cards (with/without “puppet screen”) • Cardiff Acuity Cards • 100s & 1000s / crumbs against light/dark backgrounds

Preferential Looking (Keeler / Teller Cards)

Cardiff Acuity Cards

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

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”

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

Linear Kay Pictures

Glasgow Acuity Test

Sonksen Test

Sonksen Test

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

Snellen

Acuity Equivalents

Acuity Equivalents 3m (Kays) Snellen (US) LogMAR Approx. age norms Decimal (European) Cycles per degree (cpd) Minutes of arc (MAR)

2/60 (6/180) 3/90 3/60 (6/120) 3/60 6/60 6/48 3/30 3/24 6/38 6/30 6/24 6/19 3/19 3/15 3/12 3/9.5

6/15 6/12 6/9.5

6/7.5

3/7.5

3/6 3/4.75

3/3.75

6/6 6/4.75

3/3 3/2.375

20/600 20/400 20/200 20/160 20/100 20/80 20/50 20/40 20/25 20/20 1.3

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

-0.1

birth 4 mths 6mths 0.1

9mths 1yr Screening limit (linear) Screening limit (single) 3-4yrs 0.5

0.8

1.0

1.5

3 6 15 30 30 20 10 5 2 1

Refraction

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

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

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

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

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

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

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