kavita-150305032201-conversion-gate01.pdf

ASSESMENT OF VISUAL
ACUITY IN CHILDREN
Intern:- Kavita Choudhary
Moderator :- Kunal Kishor

Definition
It is defined as the resolving power of the eye or
ability to see two separate objects.
It is determined by the smallest retinal image which
can be appreciated at a certain distance.
The VA test measures the smallest letters that
patient can read on a standardized chart at a
distance of 6m / 20 feets

Principal
The two distinct points can only be
recognizable as separate when they
subtend an angle of 1minute of an arc
at the nodal point of the eye

Normal visual Developments
AGE
At birth 6/120
4 months 6/60
6 months 6/36
1 year 6/18
2 years 6/6

Expected visual acuity levels
Age (months) OKN FPL VEP
1 20/300 20/400 20/300
6 20/60 20/150 20/20
12 20/40 20/100 20/20
36 20/20 20/20 20/20

Vision Tests in Infants
Vision Tests in Infants

CSM method
C : Central
S : Steady
M : Maintenance

2.Preferential Looking Test
Most Commonly used Test
Based upon turning of the head or eyes towards the
pattern rather than a uniform [homogenous] field.
Alternating Black and White Stripes are present
Stripe width progressively narrows which is then
randomly shown next to plain test object
Children with better vision are able to see finer
grating and turn towards it

Drawbacks of Preferential Looking Tests
Test near vision not distance vision

3.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

Drawbacks
Measures near visual acuity and not distance
Measures resolution acuity

4.Visual Evoked Potential
VEP is the measure of change of electrical activity
of the visual cortex in response to patterned
stimulus
Checkered board or square wave grating
Abnormal VEP may indicate a problem with the
visual information reaching the cortex
VEP is very sensitive to optical blurring, can thus be
used as a method of refraction in very young patient

VEP
VEP is useful in the determination of problems
such as amblyopia, cortical blindness, and visual
impairment

5.Opto kinetic nystagmus
Commonly used Test in Neonates
Test object moves in one direction
Based on observation of Pendular Eye
movements
Slow following phase & rapid recovery
phase.
Good correlation with subjective acuity.

Drawbacks of Optokinetic Nystagmus
Overestimates the visual acuity as the target is
moving

6.Catford Drum test
Based on observation of Pendular Eye movements
Testing distance is 60 cm
It comprises of white cylinder marked with black
dots of increasing size corresponding to visual
acuities
The drum is masked by a screen except for a
rectangular aperture which exposes a single spot
Spot is made to oscillate horizontally and stimulates
eye movement

Draw backs
Overestimate vision as
target is moving and
test is conducted at
short working distance
Unreliable for
Amblyopia Screening

Testing Of Uniocular Amblyopia In
Infants
Occluding Amblyopic eye child does not resist.
while occluding the normal eye, child resists
the occlusion.

1.Worth's ivory ball test:
Commonly Used
Based on Quality of Fixation
Ivory balls ranging from 0.5" 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

2.Boeck Candy Test
Child picks up only those candy beads which
he can see easily
Beads of different sizes are shown to child and
is expected to pick them up
This gives approximate estimation of visual
acuity

3.Screening Test for Young Children
and Retards [STYCAR]
Based on Pursuit Eye movements
Ten Balls rolled across a well illuminating
contrasting floor 3m away from child
Pursuit Eye movements indicate that they are
seen

1.Cardiff Acuity Test
Principle: vanishing optotype
Target - pictures, of the same overall size, drawn in decreasing
widths of white space
Acuity is determined by the narrowest white band for which the
target is visible to the child
Child naturally prefers to look at a target figure rather than the
blank end of the stimulus.

2.Miniature Toy Test
Was previously used for
Handicapped children and low
Intellegence patient
Component of STYCAR Test
2 sets of Miniature object are used
One set is with Examiner standing at
10ft and child is asked to pickup
similar objects from his own set

3.Coin Test
Coins of different sizes are shown to child and is
Child picks up only those coins which he can see
easily
expected to pick them up

4.LEA Symbol test
Used in children age between 2-
Good for amblyopic patient to avoid crowding
phenomenon.

1.Allen’s Picture Cards
It is recorded same as Snellens Acuity test
Instead of letters child identifies picture at a
distance of 6m.

2.Sheridan letter test
It uses 5 letters HOTV & X
A&U are added in 7 letter set
Examiner shows cards having
small range of letters at 3m
Child points at one of the card
identical to the examiner card

3.Lippmans HOTV test
Simpler version of Sheridan's test using only 4
letters HOTV.
Test distance 3 meter

Vision Test in 5-6 Years and above

1.Snellens Visual Acuity Test
Most commonly used
Smallest Object which can be resolved by the eye
substends the same visual angle at the nodal point
of the eye i.e 5 min of arc
The test employs a chart with rows of letters with
diminishing size

Each row is accorded a number
indicating the distance in meters at
which a person with normal visual
acuity should correctly identify the
letters
Testing distance is 6m

2.LogMAR Visual Acuity Charts
Based on Minimum Angle of
Resolution
More Precise than Snellen Test
Have regular progression in the
size and spacing of the letters
from one line to next
Same number of letters on
every line

3.Tumbling E Test
Based on Minimum Separable distance
Task is to identify the direction in which
the limb of E points
Identification of the last line gives visual
acuity

4.Landolt’s Broken Ring Chart
Most Commonly used
Based on Minimum Separable
distance.
The rings are constructed on the same basis as
that of Snellens
Child is instructed to indicate by the motion of the
hand at which point each one is broken
Interpretation of the last line identified by the
child determines visual acuity

Conclusion
Despite the development of methods appropriate to
different ages, measuring acuity remains difficult in
infants.
In addition, many techniques require special
equipment and conditions, making them unsuitable
for some settings

Cont………..
Whichever method is used to measure a child’s
vision, it is important to assess vision corrected for
any refractive errors, and to assess the eyes
separately as well as together whenever possible

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