children and different group age visual acuity assessment

1. VISUAL ACUITY
ASSESSMENT
By
Dr Azmat Khan

2. Types of Visual Acuity Testing
 a. Minimum Visible Acuity
 Minimum visible acuity is determined by the
brightness of the object relative to its
background illumination as opposed to the
visual angle subtend by the object.

3. b. Minimum Perceptible Acuity
 Minimum perceptible acuity is concerned with
simple detection of objects, not their
identification or naming.
 An example of this type of acuity testing is
determining if a child can see and grasp a small
candy bead held in the examiner's hand.

4. c. Minimum Separable Acuity
 Measures the resolution threshold, or smallest
visual angle at which two separate objects can be
discriminated.
 Landolt C, and grating acuity are examples of
minimum separable tasks.

5. d. Vernier Acuity (hyper acuity
 A precise form of visual discrimination still
under study.
 Hyper acuity has been coined to classify the high
precision (within a few seconds of arc) with
which vernier alignment task can be performed.
This level of precision is well above resolution
or recognition acuity thresholds.

6. e. Minimum Legible Acuity
 Measures the individual's ability to recognize
progressively smaller objects (letters, numbers or
objects) called optotypes.
 The angle that the smallest recognized letter or
symbol subtends on the retina is a measure of
visual acuity.
 This type of acuity testing is used most often
clinically.

7. . Snellen Acuity
 Snellen Acuity uses a notation in which the
numerator is the testing distance (in feet or
meters) and the denominator is the distance at
which a letter subtends the standard visual angle
of 5 minutes.
 A 20/20 letter (6/6 in meters) subtends an angle
of 5 minutes when viewed at 20 feet (6 meters).

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

9. Age Groups :
 Age Groups :
 Age Groups Infants (Birth – 12 months)
 Toddlers (12 months – 2 1/2 years)
 Preschoolers (2 1/2 years – 5 years)
 School going children (5 years and above)

10. Normal visual development
 From Kenneth W. Wright
 Pupillary light reaction present = 30 weeks gestation
 Blink response to visual threats = 2-5 months
 Fixation well developed = 2 months
 Smooth pursuit well developed = 6-8 weeks
 Saccades well developed 1-3 months
 OKN = 2-4 months (temporal to nasal monocular response better)
 Accommodation appropriate to target = 4months
 Stereopsis well developed = 3- 7 months

11. Normal visual development
 CSF well developed = 7 months
 Ocular alignment stabilized = 1 months
 Foveal maturation complete = 4 months
 Optic Nerve myelination complete = 7months-2 year
 Age related VA estimated by test method
Technique
OKN
FPL
VEP
Birth 2 months 4 months 6 months 1 year Age for 20/20
20/400
20/400
20/800
20/800
20/800
20/150
20/200
20/200
20/60
20/100
20/150
20/40
20/60
20/50
20/20
20-30 months
18-24 months
6-12 months
From Kenneth W. Wright

12. Normal visual development
 The development of VA from birth to age three year
 From Alec. M Ansons and Helen Davis
Age Visual Acuity
New Born
I months
4 - 6 months
3 years
6/240
6/18 - 6/6
6/6 with single optotypes
6/180 - 6/90

13. Qualitative Tests (observation of visual response)
1.Fixation:
Observe Pursuit movement and fixation
preference.
2.Cover Test:
Uniocular fixation and
Objection to occlusion.
3.Visually directed reaching:
Reaction to visual stimulas by reaching
towards the object of interest.

14. Qualitative Tests (observation of visual response)
4.100s & 1000s:
Response to small sweets indicates acuity of
approximately 6/24 at 33cm
5.Catford drum:
Moving dots or grating from 6o cm VA 2/60-6/6
6.Stycar rolling balls:( Screening test for young children and retardates)
Graded balls in various sizes from 6cm – 3.5mm in
diameter rolled along the floor from 3m.
7.16 Dioptre prism test:
To assess fixation preference in
preverbal children.

15. Quantitative Tests
1.FCPL:
The principle of this test is that a child
prefer to look at a pattern background than at a plain back
ground.
Visual acuities determine with FCPL range from
approximately 6/240 in newborn to 6/60 at three months
and 6/6 at 36 months test distance 57cm.
2.LogMAR (Bailey-Lovie):
LOGarithm of the Minimal Angle of Resolutions.
VA 6/60-6/3 and in log unit.

16. Quantitative Tests
3.Snellen Test Type: VA. 6/60-6/4
4.Sheridan Gardiner:
This test consist seven letter
(X,U,T,O,H,A,V) Matching test with key
card. VA 6/60-6/3
5.Kays Pictures:
Consist variety of picture. Matching test
with a key card or can ask the name. Also available
in LogMar format.

17. Quantitative Tests
6.Carrdiff acuity cards:
This test is based on the principal of vanishing optotypes.
The defining outer lines which form the pictures decrease in
size until the pictures appears to fade into the grey
background. The patient response is noted and recorded.
7.Cambridge crowding cards:
Matching test.This test consist five
letter (H,O,T,V,X) used with a key card with the
identification of centre letter.

18. Quantitative Tests
8.Sonksten- Silver Test:
Matching test with key card. This test
consists six letters (X,O,U,H,V,T)
9.Ffookes Symbol:
This test presents the shape of a circle, square and
triangle which the patient matches with a hand held
corresponding shape.
10.Lea Symbol test
11.Illetrate E test:
12.Landolt C test:

19. Fixation

20. Eye – Hand - Coordinatio

21. Lea Gratining

22. ‘Hundreds and thousands’
sweet test
Preferential looking with
Cardiff cards
Visual acuity tests in preverbal children

23. Visual acuity tests in verbal children
Kay single picture Multiple pictures
Sheridan-Gardiner Sonksen-Silver
At age 3 years (matching tests)
At age 2 years (naming pictures)

24. 1.Methods of testing Visual Acuity in Infants :
• Fixation Maintain Fixation Preference
• Optokinetic Nystagmus (OKN)
• Force Choice Preferential looking test (FCPL)
• Visual Evoked Potential (VEP)

25. Fixation Maintain :
There are two types fixations are present
1.Centric
2. Eccentric
Component of Fixation
C = Central
S = Steady
M = Maintained

26. CSM—central, steady, and maintained
fixation on a target.
If each eye fixates centrally rather than
eccentrically
Holds steady fixation on that target rather than
searching for it or wandering
and continues to stay fixated on that target
even when occlusion is removed from the
fellow eye, the vision is noted "CSM".

27. Fixation Preference :
Place a 10D base down prism in front of one eye
Alternate fixation indicate equal visual acuity in
both eyes
If fixation does not maintain then preferred eye
occluded
If fixation is maintained through a blink, then also
visual acuity is good

28. Optokinetic Nystagmus :
Optokinetic Nystagmus OKN drum consist of
white and black strips rotates in front of infant’s
eye
Examiner has to follow the fixation movement of
patient’s eye

29. Force Choice Preferential Looking Test :
Infants prefer to fixate high contrast bold strips
rather than homogenous field of light
Examiner has to become familiar with the child’s
looking style
First fixation Duration of fixation
Facial expression of patient

30. Visual Evoked Potential / Visual Evoked
Cortical Potential :
Visual Evoked Potential
A checkerboard stimulus phase altered at a rate of 6
cycle/sec in front of the patient’s eyes
A electrode placed on skull over occipital lobe
Result is compared with the VEP of adult

31. 2.Methods of testing Visual Acuity in
Toddlers
Hundred and Thousand Sweet Test
The Cardiff Acuity Test

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

33. The Cardiff Acuity Test :
The principle of the target design
is that of the vanishing optotype
The targets are pictures drawn with
a white band bordered by two
black bands, all on a neutral grey
background
The examiner simply observes the
child’s fixation

34. Administration of Tests in Preschoolers :
Step 1
A pre test to teach and check the child's
reliability in responding to the test
Step 2
Test to assure that the child’s responses are
reliable at 10ft (3m)
Step 3
Actual measurement of acuity level at 10ft
(3mt)

35. 3. Methods of testing Visual Acuity
inPreschoolers :
•LEA Symbols
•Light House Flash and Card
• Allen Picture Card
•Broken Wheel Test
•Tumbling E chart
•Landolt C chart
•Sjogren hand test
•HOTV test

36. LEA Symbols test :
LEA Symbols test Task is to match and point out
the distance target 10 feet distance
pictures--circle square house apple

37. Light House Flash Card Testing :
Light House Flash Card Testing 12 cards are
available, size of each card is 4×5 inch
These cards have three types of picture target
Target size available from 20/200 – 20/10
In 20/200 card we have 20/100 target size on the
reverse side

38. Allen Picture Card :
Allen Picture Card Here 6
pictures have been used –
Horse, Bird, Cake, Hand
Car and Telephone
Card size : 4 × 4 inch with
white background

39. Broken Wheel Test :
Here cards are presented with picture of a car,
very familiar to the child
Two cards are held before the child, he simply
has to recognize which one is broken
It consist of 8 pairs of test cards and a sample
pair of card (equivalent to 20/120 test size)

40. Tumbling E chart :
Tumbling E chart English E letter is used in different
directions
The child has to detect the orientation of the limbs
Landolt C chart :
Landolt C chart
Sjogren hand test

41. HOTV Test :
Optotypes are used to avoid left right confusion
Child has to identify the letter optotypes

42. 4. Methods of testing Visual Acuity inSchool
going children :
Tumbling E chart
Landolt C chart
Snellen’s chart
Log Mar Chart

43. SUMMARY
Here is a list, in age (or developmental age) order, for visual acuity tests:
Infant
VEP
OKN
Fixation behavior: CSM,
Preferential looking etc
Toddler (As soon as the child can talk)
Pictures
Preferential looking
Preschool (As soon as the child can do matching, around age 2 ½ - 3 years)
Matching: HOTV, Lea
Tumbling E
Landolt rings etc
As soon as possible ( school-aged)
Snellen letters
Numbers etc

44. Age Indication For VA Tests
 Age 0-6/12:
FCPL, VEP, OKN, Fixation, Pursuit, Objection to
occlusion, Cover Test, Catford Drum, Visually directed
reaching etc.
 6/12 to 2 years:
100s & 1000s, Stycar balls, FCPL, Cardiff cards…
 2 to 3 years:
Kay pictures, Illiterate E, Ffookes Symbol, Lea Symbol...
 3+ years:
Sheridan Gardener, Cambridge crowding cards,Sonksten
Silver, Landolt C, Snellen, LogMar, ….