Visual acuity in children

A presentation on visual acuity assessment in children.

1. VISUAL ACUITY IN CHILDREN
Dr Saurabh Kushwaha
Resident Ophthalmology

2. SCOPE
Visual acuity
Components of visual acuity
Milestones of visual development
Normal visual development
Guidelines for visual assesment
Vision tests for various age groups

3. VISUAL ACUITY (VA)
Itisthemeasureofthespatialresolutionof
visualprocessing
Alsoknownasresolvingpowerofeye
Abilitytodifferentiatetwoseparateobjectas
separateandappreciatethedetailsofvisible
object

4. COMPONENTS OF VA
Minimumvisibility:ajudgementofwhether
atargetispresentorabsent(detectionacuity)
Resolution:evidencethatthespatialdetail
Containedwithinatargethasbeenfully
resolved(resolutionacuity)
Recognition:theidentificationofatarget

5. MILESTONES OF VISUAL
DEVELOPMENT
Afterbirth:Canfixandfollowalightsource,faceorlarge,
colorfultoy
1month:Fixationiscentral,steadyandmaintained,can
followaslowtargetandconverge
3months:binocularvisionandcoordinatedeyemovements
6months:Reachesoutaccuratelyfortoys
9months:VisuallydirectedreachingEx.lookforhiddentoys
2years:Picturematching
3 years : Letter matching of single letters
5years:Snellen’schartbymatchingornaming

6. NORMAL VISUAL DEVELOPMENT
Age VA
At birth 6/120
4 months 6/60
6 months 6/36
1 year 6/18
2 years 6/6

7. EXPECTED VA LEVELS
Age
(months)
OKN FPL VEP
1 20/30020/40020/300
6 20/60 20/15020/20
12 20/40 20/10020/20
36 20/20 20/20 20/20

8. WHY TO RECORD VA IN
CHILDREN?
Mosteyeproblemscanbetreatedif
detectedearly
Toknowifvisualdevelopmentisnormal
Helpsdecideeligibilityforlowvisionand
rehabilitationservices

9. GUIDELINES FOR THE
ASSESSMENT OF VA
Cooperationandunderstandingthetest
Childrenperformbestiftheexaminationtakesplace
whentheyarealertEx.earlyinthemorningorafteran
infant'snap
Becauseinfantstendtobemorecooperativeand
alertwhenfeeding,itissuggestedtobringabottlefor
feedingthechild
Distancevision:3m;Nearvision:33cms
Easysymbols
Linearvisualacuityshouldbetestedassoonas
possible(moreaccurate)

10. VISION TESTS UPTO 3 MONTHS

11. BLINK REFLEX TEST
Theblinktoabrightlightisabehaviorlearned
by30weeksofgestationalageandis
occasionallypresentindecorticateinfants.
Theblinktoathreateninggestureisanother
learnedreflex,usuallypresentby5months
Whentesting,caremustbetakennottobrush
airagainstthechild’scorneasandelicitablink
bythatmechanism.

12. PUPILLARY LIGHT REFLEX TEST
The pupillary light response is not equivalent to
visual ability, but its presence indicates intact afferent
visual neurologic pathways to the level of the brachium
of the superior colliculus and efferent pathways to the
iris sphincter
Visualization in very young children sometimes
requires a magnifying glass, as their pupils are smaller
than those of older children (because of decreased
sympathetic tone) and the light responses are of small
amplitude
This reflex is present in premature babies over 29 -
31 weeks of gestational age

13. EYE POPPING TEST
Sometimesveryyounginfantsdon'tshowany
distinguishablevisualbehavioratall.Inthiscase,the
eyepoppingreflexindicatesatleasttheinfant’sability
todetectchangesinroomillumination
Whentheroomlightsaresuddenlydimmed,the
baby'suppereyelidsshouldpopopenwidefora
moment.Thebabywilloftencloseitseyeswhenthe
lightsarebroughtbackup,butwillagainpopitseyes
openwhenthelightsaredimmed.Thisbehavioris
documentedas"positiveeyepopping".

14. OPTOKINETIC NYSTAGMUS
CommonlyusedtestinNeonates
Testobjectmovesinonedirection
BasedonobservationofPendulareye
movements
Slowfollowingphase&rapidrecoveryphase
Goodcorrelationwithsubjectiveacuity
Overestimatesthevisualacuityasthetargetis
moving

15. VISUAL EVOKED POTENTIAL
VEPisthemeasureofchangeofelectricalactivityof
thevisualcortexinresponsetopatternedstimulus
Checkeredboardorsquarewavegrating
VEPisusefulinthedeterminationofproblemssuch
asamblyopia,corticalblindnessandvisualimpairment
•Flash VEPs
•Pattern reversal VEPs
•Sweep VEPs

16. VISION TEST IN 3-6 MONTHS

17. FIXATION BEHAVIOR TEST
Thetestisperformedbyseatingthechildcomfortably
inthecaretaker'slap.Theobjectofvisualinterest,
usuallyabrightcoloredtoy,isslowlymovedtotheright
andtotheleft.Theexaminerobserveswhetherthe
infant'seyesturntowardtheobjectandfollowits
movements(fixandfollowbehavior).Theexaminercan
useathumbtooccludeoneoftheinfant'seyesinorder
totesteacheyeseparately
Ifthechildhasafixandfollowbehaviorthenitis
assumedthatthepatientcouldseeasmalltargetortoy
inanormallyilluminatedroom

18. BINOCULAR FIXATION PREFERENCE
Behavioralevidenceofdecreasedvisioninrighteye(A)A
smalltoyisusedtogetthechild’sattention,andtheexaminer
coverstherighteyetomonitorfixationofthelefteye.Thechild
fixatesonthetoywithoutobjecting(B)Whenthelefteyeis
covered,thechildobjectsandtriestomovetheexaminer’s
hand(C)Whentherighteyeiscovered,thechilddoesnot
objectandtrackstheobject.

19. CSM
CSM:Central;Steady;Maintenance
‘C’referstothecentralcorneallightreflexasthe
patientfixateseyeontheexaminer’slightandiffixation
targetisviewedeccentricallythenitistermedas
uncentral
‘S’referstothesteadinessastheexaminer’slightis
motionlessandthenitisslowlymovedout
‘M’referstotheabilityofpatienttomaintain
alignment,firstwithoneeyethenwithanother
Testisdonewithtargetat40cmdistance
CSM:6\6-6\9
CSNM:6\36-6\60
Unsteadycentralfixation:<6\60

20. VISION TEST IN 6-12 MONTHS

21. PREFERENTIAL LOOKING TEST
Mostcommonlyusedtest
Baseduponturningoftheheadoreyestowards
thepatternratherthanauniform(homogenous)field
Alternatingblackandwhitestripeswith
progressivelynarrowingstripsareshownrandomly,
nexttoplaintestobject
Childrenwithbettervisionareabletoseefiner
gratingandturntowardsit
Testnearvision&NOTdistancevision

22. TELLER ACUITY CARDS
Modified form of Preferential Looking Test
Simpler & rapid testing
contains 17 cards
12.5 x 12.5 cm patches of square wave grating
Gratings contrast : 82% -84%
Proper illumination :10 candelas/m²
Measures near visual acuity and NOT distance

23. CATFORD DRUM TEST (CAT)
BasedonobservationofPendularEyemovements
Itcomprisesofwhitecylindermarkedwithblackdots
ofincreasingsizecorrespondingtovisualacuities
Thedrumismaskedbyascreenexceptfora
rectangularaperturewhichexposesasinglespot
Spotismadetooscillatehorizontallyandstimulates
eyemovement
Overestimatevisionastargetismovingandtestis
conductedatShortworkingdistance
UnreliableforAmblyopiaScreening

24. VISION TEST IN 1-3 YEARS

25. WORTH'S IVORY BALL TEST
Based on Quality of Fixation
Ivory balls ranging from0.5“ to 1.5", rolled on
floor at a distance of about 3 metres
Child is asked to retrieve each ball
Rough estimate of visual acuity is made from
the size of smallest ball which the child can see

26. BOECK CANDY TEST
Childpicksuponlythosecandybeads
whichhecanseeeasily
Beadsofdifferentsizesareshowntochild
andisexpectedtopickthemup
Thisgivesapproximateestimationofvisual
acuity

27. SCREENING TEST FOR YOUNG
CHILDREN & RETARDS [STYCAR]
DYNAMIC
•BasedonPursuitEyemovements
•TenBallsrolledacrossawellilluminatingcontrasting
floor3mawayfromchild
•PursuitEyemovementsindicatethatballsareseen
STATIC
•Thesphereismountedonawandandintroduced
intotheperipheryofthevisualfieldandexaminer
determineswhetherthechildfixatesornot

28. MARBLE GAME TEST
Inchildrenof1-2yearsofagereachingor
placinggamescanbeusedtoestimatevisual
function
Thistestisnotintendedtomeasurevisual
acuityofeacheye
Thechildisaskedtoplacemarblesinthe
holesofacardorinabox
Comparethefunctioningofthechild’seye
whenoneortheotherisclosed
Thevisionofaneyeisthennotedasbeing
usefulorlessuseful

29. DOT VISUAL ACUITY TEST
Childisshownanilluminatedboxwithblack
dotsofdifferentsizesprintedonit
Thesmallestdotidentifieddenotesthe
visualacuityofthechild
Testdistanceis25cm
VA:20/800to20/20

30. CARDIFF ACUITY TEST (CAT)
Principle:vanishingoptotype
Target:pictures,ofthesameoverallsize,
drawnindecreasingwidthsofwhitespace
Acuityisdeterminedbythenarrowestwhite
bandforwhichthetargetisvisibletothechild
Childnaturallypreferstolookatatarget
figureratherthantheblankendofthestimulus

31. MINIATURE TOY TEST
Waspreviouslyusedforhandicappedchildren
andlowIntelligencepatient
ComponentofSTYCARTest
2setsofMiniatureobjectareused;01setis
withexaminerstandingat10ftandchildisasked
topickupsimilarobjectsfromhisownset

32. COIN TEST
Coins of different sizes are shown to child and
expected to pick them up
Child picks up only those coins which he can
see easily

33. PATTI PICS
PattiPicswereintroducedin2003asanimproved
testforvisionscreeningandtestingofpediatric
patientswhereuniversalsymbolsandmatchingmay
servetheprocessbetterthanlettersorothersymbols.
Onlysymboltestwiththestatedobjectiveof
calibrationtargetedtoequalSloanlettersusedinthe
ETDRScharts
Thisuniformityisespeciallyimportantwhentaking
patientsfromsymbolstolettertests

34. VISION TEST IN 3-5 YEARS

35. LANDOLT’S BROKEN RING CHART
BasedonMinimumSeparabledistance
Theringsareconstructedonthesamebasisas
thatofSnellen’stest
Childisinstructedtoindicatebythemotionof
thehandatwhichpointeachoneisbroken
Interpretationofthelastlineidentifiedbythe
childdeterminesvisualacuity

36. BROKEN WHEEL TEST
Consist of 8 pair of test cards 20/20, 20/25, 20/30,
20/40, 20/60, 20/80, 20/100, 20/120.
Each card has a black line drawing of a car on a
white background
1 with solid wheels, other with broken wheels.
Done from 3 m distance

37. TUMBLING E TEST
BasedonMinimumSeparabledistance
Taskistoidentifythedirectioninwhichthelimb
ofEpoints
Identificationofthelastlinegivesvisualacuity

38. ISOLATED HAND FIGURE TEST
Sjogrenhas replaced the E chart with the isolated
figure of a hand & in some children it works better than E
chart

39. SHERIDAN LETTER TEST
Ituses5lettersHOTVX
AandUareaddedin7letterset
Examinershowscardshavingsmallrangeof
lettersat3mandchildpointsatoneofthecard
identicaltotheexaminercard

40. LIPPMANS HOTV TEST
Simpler version of Sheridan's test using only 4
letters HOTV
Test distance 3 m

41. ALLEN’S PICTURE CARDS
ItisrecordedsameasSnellen’sacuitytest,
insteadofletterschildidentifiespictureata
distanceof6m

42. KAY PICTURE TEST
GoldStandardvisiontestforpre-literatechildren,
providingaccurate,crowdedvisualacuity
measurementsearlierthansymbolandlettertests.
Thetestisdoneatdistanceof6meter
Spiralbookletswithasinglepictureineachpage
Thesizedecreasesfrom6/60to6/6witheach
sizehaving3cards
Againthepatientisgivenakeycardandis
askedtomatchwiththepictureasshowninthe
mainchart

43. LEA SYMBOL TEST
Good for amblyopic patient to avoid crowding
Phenomenon

44. LIGHT HOME PICTURE CARD
Achartcontaininganapple,ahouseandanumbrella
arrangedinSnellen’sequivalentsof20/200-20/10
Thechildidentifesthepicturesalongthelines
Thetestiscarriedoutat3m
12cardsareavailable,sizeofeachcardis4×5inch

45. VISION TEST IN 5-6 YEARS AND
ABOVE

46. SNELLEN’S VISUAL ACUITY TEST
Mostcommonlyused
SmallestObjectwhichcanberesolvedbythe
eyesubtendsthesamevisualangleatthenodal
pointoftheeyei.e.5minofarc
Testingdistanceis6m

47. LOGMAR VISUAL ACUITY CHARTS
BasedonMinimumAngleofResolution
Samenumberoflettersoneveryline
Haveregularprogressioninthesizeandspacing
ofthelettersfromonelinetonext
MorePrecisethanSnellen’sTest

48. ETDRS
TheETDRSacuitytestwasdevelopedtoaid
inevaluatingthechangesinvisionfollowing
panretinalphotocoagulationinpatientswith
diabeticretinopathy.Previousstudieshad
somewhat confusingresultsdueto
inadequaciesoftheacuitytestsusedinthose
earlystudies.

49. CONCLUSION
Measuringvisioninchildrenisacomprehensive
task.Fordiagnosticpurposes,follow-upand
evaluationofvisualimpairments,allelements
shouldbeconsideredandcomparedwiththe
visualfunctionofdailylife.Resultsneedtobe
explainedanddiscussedwiththeparentsor
guardiantohelpthemunderstandthesituation
andstrengtheninteractionwiththeirchildren.This
willreducethevisualdisability,especiallyifthe
visioncannotbeimprovedthroughmedical
treatment.

50. THANK YOU