Real pediatric visual acuity assessment

Pediatric Visual acuity assessment
Resource person:
Ms. Manisha Dahal
Presenters:
Kamal Luitel
Bipin Koirala
IOM, MMC

Presentation layout
 Introduction
 Visual milestones
 Acuity assessment methods :
a. Infants
b. Toddlers
c. Preschools
d. School child's
 Points to remember
 Challenges in VA assessment
 Amblyopia : Handle with care

Visual Acuity
 It is the resolving power of the eye.
 In simple word, it is an ability to see two separate objects separately.
 It is determined by the smallest retinal image which can be appreciated at
certain distance.
 Standardized chart distance for VA for Adult is 6m/20 feet but it may varied
in case for children.
?

Visual acuity in infants…
 Visual acuity, in preverbal infants(who cannot speak) is
defined as a motor or sensory responses to a threshold
stimulus of known size at known distance.
 In preliterate but verbal children , VA is defined as the
smallest target of known size at known testing distance
correctly verbally identified by a child

Why to record visual acuity in children ?
 To know if the visual development is normal.
 Most of the eye problems can be treated if detected early.
 Helps to decide eligibility for low vision and rehabilitation services
 Useful in decision making.

Things to be consider while assessing VA in infants…
 A child should be aware & responsive to the surroundings &
situations.
 In both normal and visually at-risk infants, improvement in vision on
time depends on both the assessment technique used and the aspect
of vision that is being assessed.
 Visual development during infancy is highly plastic and can be
interrupted or modified by either external or internal environmental
factors(physiological factors).

 Examination early in the morning or after an infant's nap
is usually most effective.
 Infants are more cooperative and alert when feeding, it
is also helpful to suggest that the parent bring a bottle
for the child.
Cont…

Age group categories:
 Infants (Birth – 14 months)  Toddlers (14 months – 2 1/2 years)
 School children (5yrs – 15yrs)Pre-schoolers (2 1/2 years – 5 years)

Very soon after birth – can fix & follow a light source.
1 months – fixation is central, steady & maintained.
can follow a slow target.
3 months – binocular vision & eye coordination.
6 months – reaches out accurately for toys.
9 months – looks for hidden toys.
2 years – picture matching.
3 years – letter matching of single letters.
5 years – Snellen chart by matching or
naming.
Normal Visual Milestones :-

How Actually a baby sees a real world….

New born Can Fix a light source

1 Months = able to focus on objects 3 feet away &
face in front.

2 Months = eyes become more coordinated

3 months = start to reach for objects

5- 6 months= can perceive color spectrum

11- 12 months = fully develop VA like adults

Other functions which correlate with vision

Rule of 8
Age in Years Rule of 8 Expected Visual Acuity
2 8-2=6 20/60
3 8-3=5 20/50
4 8-4=4 20/40
5 8-5=3 20/30
6 8-6=2 20/20
:- Numbers are in bold type for emphasis

1. Opto kinetic nystagmus test
2. Preferential looking test
3. Cardiff acuity card test
4. Visually evoked response
5. Catford drum test
6. Indirect assessment of visual acuity
7. Hundred & thousand sweet test.
8. Lea paddle
Different types of VA Assessments in infants..

 In infants we use resolution acuity rather than recognition
acuity.
 Resolution acuity sometimes underestimate some visual
deficits like amblyopia although it is still the best method
for assessing an infant child’s visual capabilities.
Points to the Ponder:-

1. Optokinetic Nystagmus Test
OKN drum has been proposed as a method
of measuring visual acuity in children.
In this test, nystagmus is elicited by passing
a succession of black & white stripes through
the patient’s field of vision.

Procedure:
 Striped patterns are presented on a rotating drum at 40cm.
 The drum is moved in one direction in front of the patient.
 The drum should be rotated 1 revolution per 2-3 sec.
If the striped pattern is visible, the patients eyes will make
‘Rail road Nystagmus’ eye movements as they follow the
movement of the stripes.
This gives the evidence of vision in child.

Rotating OKN drum
Induced pendular nystagmus

 The clinician determine that elicits the
nystagmus response when it is moving.

Advantages:
 Quick & easy method to evaluate infant
 Portable
 Drum don’t break easily
Disadvantages:-
 Sometimes normal responses may occur in the
decorticated infant, which indicate that
subcortical areas of the occipital cortex may
generate optico- kinetic responses.
 Difficult to keep the infant fixated on this stimulus,
which take small portion of his visual
environment.
Cont…

Cont…
 Stimulus’s uniform average luminance & uniform
rate of rotation is difficult to maintain.
 Sometimes our interpretation may become wrong,
because we are evaluating a motor response in an
attempt to assess sensory function. So care should be
done to those having alteration in the oculomotor
system.

2. Preferential Looking Test
Procedures:
1. The child is presented with two stimulus field.
2. One with stripes and the other with a
homogenous gray area of the same average
luminance as stripes randomly alternated.
 PLT is used to assess VA in infants &
young children who are unable to
identify pictures or letters.

3. Typically, infants and children
will look at the more
interesting stripes.
4. A small peephole is centered
between the two fields, for
observer.
5. Observer judges the location
of the strips based on the
child’s head & eye
movements.
Cont…

 If the child can see the stripes,
he/she will prefer to look them.
 If the child can’t see them, the child
will not show a preference.
 Visual acuity determined with this
method
Interpretation..

3. Cardiff Test
 Good for slightly older children
 Consists of different cards
 They are held in front of the child
 Each card has a picture in the upper or the lower part of
the card
 The examiner simply observes the children’s fixation.
 The target are pictures drawn with a white band bordered
by two black bands , all on a neutral grey background.
 The average brightness of the picture is equal to that of the
grey background

 If the child's vision is good enough to
resolve the white and black bands, the
picture will be visible
 If the child vision is poor , than , the bands are too narrow
for child to resolve them, the picture merges with the grey
background, and simply becomes invisible. ( like vanishing
optotypes)
Interpretation..

Advantages:
 Testing cards are simple
 Portable
 Cannot lose calibration
 Time takes less than 20 mins
Disadvantages
This test presets a resolution acuity task , but not a
recognition acuity task, thus may be less ideal for the
detection of amblyopia.
This cards presents with the stripes in one orientation
(vertical) only, so for some optically uncorrected
astigmatic children the test might be unreliable.

Cont…
Difficult to those child having nystagmus
False high acuities are detected in patients with
anisometropia and strabismic amblyopia as these
patients typically have better near visual acuity.
Lack of crowding phenomenon.

4. Visually Evoked Potential
 It is a electro encephalo graphic recording made from
the occipital lobe in response to visual acuity.
 It is the only clinically objective technique available to
assess the functional state of the visual system beyond
the retinal ganglion cells.
 It is quite useful in assessing
visual function in infants.

 Flash VEP determines the integrity of
macula & visual pathway function.
 Pattern VEP depend on form sense &
gives rough estimate of the visual acuity.
Target on MonitorPreparation for the test
Cont….

Procedure :-
 A proprietary disposable headband with integrated electrodes is
used for recordings.
 Electrodes are placed in child’s forehead, parietal and occipital
part.
 Infants are positioned on a parent’s lap and children are seated in
a comfortable chair at a measured distance of 57 cm from a 17-
inch (43-cm) display monitor, so that the stimulus subtended a
total visual angle of 20°.
 The room is darkened except for the light from the testing
equipment.
 Testing is performed monocularly, using an adhesive occluder
over the fellow eye.

Limitations of VEP
 Cumbersome process
 Time consuming
 Complexity of the generated waveforms
 VEP are recorded even in absence of occipital cortex and
in cortical blindness due to contribution by sec. visual
cortices.

Expected visual Acuity Levels
Age ( Months )
Optokinetic
Nystagmus
Force
preferential
looking
VEP
1 6/90 6/120 6/90
6 6/18 6/45 6/6
12 6/12 6/30 6/6
36 6/6 6/6 6/6

5. Catford Drum Test
 It is a detection acuity test.
 It is useful in infants &
preschool children.
In this test, the children is made to observe
an oscillating drum with black dots of varying
sizes.
 The smallest dot that evokes pendular eye
movements denotes the level of visual
acuity

6. Indirect assessment of visual acuity
 Blink reflex in response to sound.
 Menace reflex i.e; closure of the eyes on
the approach of an object if vision is
normal.

 Behaviour evidence of decreased
vision in right eye.
a) A small toy is used to get the child’s attention & the
examiner covers the right eye to monitor fixation of the left
eye. The child fixates on the toy without objecting.
Binocular fixation preference
Cont..

b. When the left eye is
covered, the child objects
& tries to move the
examiner’s hand.
Cont…
c. When the right eye is
covered, the child does not
object & tracks the object

 CSM Method
Done with one eye fixating on an accommodative target
held at 40 cm.
 ‘C’ refers to the location of corneal light reflex
fixates the examiner light at monocular conditions.
 Normally reflected light from cornea in near the
centre of cornea and it should be positioned
symmetrically in both eyes.
 If fixation target is viewed eccentrically, fixation is
termed uncentral.
Cont…

 ‘S’ refers to the Steadiness of fixation at examiners light
and also as it slowly moved about.
 ‘M’ refers to the ability of the patient to Maintain alignment
first with one eye then the other as the opposite eye is
uncovered.
Evaluation :
CSM :– 6/9 – 6/6
CSNM: – 6/36 – 6/60
Unsteady central fixation < 6/60
Cont…

7. Hundred & Thousand Sweet Test
 If child able to pick up
small sweets at 33
cm, visual acuity is at
least 6/24 or 20/80.

8. Lea paddle
 It is based on preferential looking and Snellen
principle .
 The chart is placed at a distance of 1m from the
patient .
 It is usually used for the age group of 3 to 9 mnths.
 There are cards available of various thickness of
lines .

Procedure:-
 At a time two cards are held infront of the patient. The
blank infront and the one with lines ie, held behind it .
 Then immediately the second card is flipped out and
we keep on changing the positions.
 The patient should appreciate the card with lines. The
test is done at same eye level and the eye movement
of patient is seen .

Visual acuity
assessment
in Toddlers

List of methods used for visual acuity assessment
Dot visual acuity
test
Coin test
Miniature toy test
Sheridan’s ball
test
Boek’s candy test
Worth’s ivory ball
test
Marble game test
Methods
Cardiff acuity
test

Dot visual acuity test
1. Measures detection acuity.
2. Subjective method .
3. Black dots on white back ground of different size
4. Testing distance : 25 cm
5. VA range : (6/240 to 6/6)

Procedures:
a. Child is shown an illuminated box with black dots of different sizes printed on it.
b. Smallest dot identified denotes visual acuity of child

Coin test
1. Measures detection acuity
2. Subjective method.
3. Gross assumption of visual acuity
4. Coins of different sizes are used
5. Testing distance : 25 – 30 cm.

Procedures :
a. Coins of various sizes are shown to child
b. Child picks up only those coins which he can see easily
c. Smallest coin picked by child will give us threshold value of VA

Miniature toy test
1. Subjective method
2. Tests recognition acuity.
3. Testing distance : 3 meters ( 10 ft )
4. Initially was designed for handicapped and low
intelligence patients
5. Materials required: 2 sets of miniature toys (
near set & distant set )

Procedures :
a. Child is shown miniature toy from 10 ft
b. Child is asked to pick matching pair from near set
c. Smallest toy set correctly matched by child will give us VA .

Marble game test
2. Doesn’t actually measures visual acuity
but compares performance of two eyes
Procedure :
a. Child is asked to place the marbles of various size into a hole or a box
b. And based on the performance vision is noted as being ‘useful’ or ‘less useful’

Boek’s candy bead test
2. Detection acuity test
3. Testing distance : 40 cm
4. Snellen equivalent of 6/60 can be assumed by this method.

Procedures:
a. Child is shown with beads of different color and sizes
b. Child picks up those candy beads which he can see easily
c. Chocolate coated candy are best options.

Ivory’s ball test
1. Introduced by Worth’s
2. Child must be old enough to walk and reach objects
3. Subjective method and based on quality of fixation
4. Detection acuity method
5. Testing distance : 3 meters

Procedures:
a. Test consists of set of 5 ivory balls , size ranging from o.5 inch to 2.5 inch .
b. Ivory balls are rolled 3m in front of child and asked to retrieve.
c. Smallest ball that is retrieved will give gross VA estimation.

Sheridan's ball test
2. Based on quality of fixation and follow response
3. Detection acuity method
5. Styrofoam balls of progressively small sizes are used.

Procedures :
a. Styrofoam balls are rolled in front of child in different directions at 3m .
b. White or grey back ground is used based on color of ball for better contrast
c. Smallest ball that the child can correctly fixate and follow will give gross VA

Cardiff acuity test
 Testing distance : 1m
 Objective method
 Test resolution detection and recognition acuity together.
 Based on forced preferential looking
 Vanishing optotype with a white band bordered by two black bands
each of half the width of white band against uniform grey
background are used.
 If target lies beyond child's acuity limit target merges in background
becomes invisible.

Contd ..
 Target used are pictures of same size but decreasing width of black
and white band.
 Acuity is given by narrowest white band for which target is visible
 Equivalent Snellen's acuity at 1m is specified by manufacturer .
 Acuity measured by this test ranges from 6/48 to 6/ 7.5
 Best for toddlers and preschoolers

 Cardiff acuity consists of 3 charts at each acuity level.
 Pictures includes Apple , Sock , Fish , House, Boat, Train , Duck ,Car.
 Usually 2 charts are presented before child at a time and examiner looks from
peephole behind and estimates the orientation of child .

Visual acuity
assessment in
preschools

Illiterate E
cutout test /
Tumbling E test
Lea symbols
Isolated hand
figure test
Sheridan-
Gardiner HOTV
test
Ffooks test
Allen preschool
test
Broken wheel
test
Patti pics
Light house
picture cards
Methods
Kay picture chart
test

Broken wheel test
2. Recognition test based on direction identification.
4. Optotypes similar as landolt’s C is used
5. It is also based on forced choice response.

Procedure:
a. A pair of cars one of which has cut out wheel is
presented.
b. Size of car is progressively reduced
c. Child is asked to identify the car with wheel cut out.
d. Test is discontinued after child makes wrong
identification.
e. Acuity level is assumed equivalent to Snellen's
optotype

Allen preschool test
2. Recognition acuity.
3. Gives reliable result for children above 2 yrs and
preschool
4. It includes easily recognized cake , hand , bird , horse,
telephone etc.
5. VA is recorded in terms of 30 foot denominator.

Procedures :
a. Child is made familiar with pictures available.
b. Child’s one eye is closed and examiner presents the pics in sequence.
c. Examiner gradually backs away from child.
d. Greatest distance at which sequence of at least 3 pics is correctly identified is
mentioned as numerator.
e. Example : right eye VA = 20 /30 left eye VA = 25/30

Kay picture test
1. Subjective method & Recognition acuity.
3. Easy quick and effective method for children above 18 months.
4. Also effective in nonverbal and dumb childrens.
5. Available in booklet form with each page consisting 3-4 pictures of equal size in a
box.
6. Pictures used are clock , fish , apple , cup , leg , bus etc.

7. Procedures:
a. Child is made familiar with the pictures available.
b. Child is then instructed to spell the name of pictures indicated by
examiner at 3 meters distance .
c. Book is flipped to next to page until threshold value of VA is reached i.e.
child is unable to identify the picture correctly.
d. At threshold page child is rechecked by asking him to identify all picture at
that page and at least one picture in preceding and following page.
e. Acuity in Snellen's equivalent as well as log MAR value is present at
corner of each page.
8. Kay picture is available in single kay picture form as well as crowed form

Tumbling E chart test
1. Also called as illiterate E chart.
2. Subjective method and recognition acuity
measurement.
3. Testing distance: 3 meters or 6 meters.
4. Chart consists of letter E of different size ( gradually
decreasing ) and different orientations.
5. VA is specified as Snellen's notation.

Procedure:
a. Child is made familiar with the test and instructed to indicated the
orientation of legs of E
b. One eye covered , child seated at recommended testing distance
c. Child is asked to indicate E orientation from top to bottom gradually
until threshold is reached

Sheridan Gardiner chart
2. Recognition test
4. VA specified in Snellen's notation.
5. Chart consists of set of cards with isolated letters
6. Optotype size ranges from 6/60 to 6/3 letters used are H, U ,X ,O ,V ,T, .A

Procedures:
a. Done monocularly
b. Child seated at recommended testing distance.
c. Demonstration card can be give to child .
d. Child is instructed to spell the letter shown or indicate it in the demo chart
e. Test is performed until threshold is reached.

Sheridan Gardiner HOTV test
1. Similar to Sheridan Gardiner test
2. For easiness only four letters are used
3. 4 Letters used are H,O,T,V.
4. Chart might consists of isolated letters as previous
test or crowed letters.
5. VA specified as Snellen's notation.

Sjogren’s isolated hand figure test
Sjogren replaced the letter E with isolated hand figure.
2. Recognition test based on direction identification.
4. More familiar for children's

Procedure :
 Procedure similar to tumbling E chart test,
 Child is asked to indicate the orientation of fingers
 VA specified in Snellen's notation.

Ffook’s test
 Recognition acuity and subjective method.
 Testing distance : 1 meters
 Uses THREE symbols- a square, a circle & an equilateral
triangle.
 The presentation is by means of a book with two or four
symbols on each page; or a cube with a single symbol on each
face.
 Cut-out symbols are given to the child & is asked to point out
the correct symbol shown to him.

Lea symbols
1. Recognition acuity and subjective method
2. Testing distance: 3 meters
3. May be available in isolated letter format or crowded letter log MAR format.
4. 4 Optotypes used : square , apple , home , circle
5. Other format of lea chart are also used for near acuity assessment , contrast
assessment
6. VA is noted in equivalent snelllens notation or logMAR form.

Procedures :
a. Child is made familiar with picture used
b. One eye is occluded
c. A chart is given in child’s hand and instructed to indicate the picture
shown by the examiner.
d. Picture are indicated in distance chart from larger to smaller until child
cannot further identify the pictures correctly

Patti pics test
1. A variety as lea symbol
2. Optotype used are similar to lea symbol
except new added STAR .
3. Testing procedure is also same as lea
symbol test.

Research corner
The measurement of visual acuity in children : An evidence based update
Nicola S anstice PhD B optom (Hons )
Benjamin Thompson PhD
1. Patti pics gives more consistent result as compared to lea symbol in adults.
2. Patti pics VA is poorer than lea symbol VA by 1 line of optotype (0.1 log MAR)
3. Similarly Bailey-lovie chart also estimated one line poorer VA than lea symbol.
4. So Patti pics are considered standard test as compared to lea symbol

Visual acuity
assessment in
school age
(Above 5 yrs )

Snellen's letter
chart
Snellen’s E chart
Near acuity test
chart
HOTV test chart
Bailey Lovie
chart
Lanolt’s C ring
chart
Methods

Bailey Lovie chart
 LogMAR is used to notate the acuity
 Bailey-Lovie Chart follows following principles:
a. Geometric progression of size & spacing is 0.1 Log unit or 4/5
b. It has been found that the relative spacing between letters and the
number of letters per row can cause substantial variation in acuity scores

 It is based on the assumption that perceived changes in visual acuity are
proportional to the logMAR
 In this chart equally legible symbols with the same number of symbols in each row
(5) and spacing between rows and symbols proportional to the size of the symbol is
used .
 Acuity becomes worse as the log MAR value increases

 Value of each letter is 0.02 in every line (every line has 5 letters)
 Letter to Letter scoring system
 Each line = 0.1 log unit &
a. 25% larger, than the preceding line
b. Every third line is double/ half sized = 0.3 Log unit diff.
 Usual testing distances : 4 or 3 meters (depending on charts)
 Can be done at 2 or 1.5 m,
VA value = Log MAR score + 0.3 for every half distance

Snellen's letter chart
 Recognition and resolution acuity
 Testing distance : 3/6 meters
 Subjective method

Snellen’s E chart
 Resolution acuity
 Based on direction prediction
 Subjective method
 Testing distance: 3/6 meters

Summary of distant acuity testing

Near acuity measurement
Reduced kay
picture
McClure
reading book
Log MAR near
chart
Reduced
Snellen's chart
Pediatric
near acuity

Things to remember
during pediatric
visual acuity
assessment

Environment must be child friendly.

It is best to access VA with child in lap of parents.

Examiner must always try to gain child's attention
either by singing rhymes, whistling or with toys etc.

Child may peep through finger may press eye
with palm

It is best to encourage the child during the procedure by
saying good ,excellent or with certain rewards like candy.

Contd..
 Binocularly and monocularly in amblyopia , latent nystagmus
 1st better seeing eye is examined
 Test must interesting and attractive for child's.
 Test should not be complicated and must be understood by child.
 Examined with same test in every follow up if possible
 VA in small children's (<3yrs) must be accessed by indirect method and above by
direct method.

Challenges of pediatric VA assessment
 Uncooperative child
 Syndromic child's or child with delayed
developmental milestones

 Dumb / deaf / blind
child's/communication barriers
 Amblyopia

Amblyopia : Handle with care
 Vision test first in better eye.
 Vision both with and with out correction must be considered.
 Vision with single as well as crowed optotype must be
accessed.
 Always use same type of chart in each follow-up to record
improvement or deterioration
 Child may cheat with better seeing eye so examiner must be
careful.
 Grating acuity is less affected than Snellen's acuity in
strabismic amblyopia

Meridional amblyopia due simple myopia and with the rule astigmatism have under
estimation of visual acuity when E optotype is used.
Because horizontal gratings are out of focus in such refractive error.

Summary
 Task is always challenging & critical.
 Examiner must have enough calmness and patience
 Must choose appropriate method for each age group.
 Amblyopia must be handled with more care.

Real pediatric visual acuity assessment

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