This document discusses methods of measuring visual acuity in infants. It describes that visual acuity improves rapidly in the first years of life and matures around 5-6 years old. Several tests are mentioned, including optokinetic nystagmus testing, preferential looking tests, visually evoked responses, Cardiff acuity card tests, and observation of fixation behavior. Normal visual development milestones from birth to age 5 are provided. The document gives details on different visual acuity tests used with infants, such as the optokinetic nystagmus test, preferential looking test, and Lea paddle test.

1. VISUAL ACUITY
IN INFANTS
Zarin khan
B.Optom

2. VISUAL ACUITY
 It is the resolving power of the
eye. It is an ability to see two
separate object as separate.

3. VISUAL ACUITY IN INFANTS
 Visual acuity, in preverbal
infants defined as a motor or
sensory responses to a
threshold stimulus of known
size at known distance.

4. MEASUREMENT OF VISUAL
ACUITY IN INFANTS
A child should be aware & responsive
to the surroundings & situation.
A normal pupillary response, a positive
blind response & an elicitable OKN
indicate good visual acuity.
VA improves rapidly during the 1st
years of life than matures
approximately 5-6 years of age

5. Fixation behaviour can be determined
accurately in this age group as the
fovea develops completely by 3 months
of age.
If the child habitually fixates with one
eye, it indicates poor vision in the non
fixating eye.

6. AGE GROUP
 Infants (Birth – 14 months)
 Toddlers (14 months – 2 1/2 years)
 Pre-schoolers (2 1/2 years – 5 years)
 School going children (5 years – 15
years)

7. NORMAL VISUAL DEVELOPMENT
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.

8. DIFFERENT TYPES OF VISUAL
ACUITY TEST IN INFANTS
 Opto kinetic nystagmus test
 Preferential looking test
 Visually evoked response
 Catford drum test
 Cardiff acuity card test
 Indirect assessment of visual acuity
 Hundred & thousand sweet test.
 Lea paddle

9. OPTO KINETIC 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.

10. Procedure:
Striped patterns are presented on a
rotating drum.
The drum is moved in one direction
in front of the patient.
If the striped pattern is visible, the
patients eyes will make ‘Rail road
Nystagmus’ eye movements as they
follow the movement of the stripes.

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

12. RECORDING
New born 6/120
2 months 6/60
6 months 6/30
20-30 months 6/6

13. PREFERENTIAL LOOKING TEST
PLT is used to assess VA in infants &
young children who are unable to
identify pictures or letters.
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.

14. 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.

15. 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
RECORDING
New born 6/240
3 months 6/60
36 months 6/6

16. VISUALLY EVOKED RESPONSE
It is quite useful in assessing visual
function in infants.
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.

17. Flash VER determines the integrity of
macula & visual pathway function.
Patter VER depend on form sense &
gives rough estimate of the visual
acuity.

18. 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

19. CARDIFF ACUITY TEST
 The principle of the target design is that of the
vanishing optotype.
 The targets are pictures drawn with a white
band border by 2 black bands, all on a neutral
gray background.
 The examiner simply observes the children’s
fixation.

20. 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.

21. BINOCULAR FIXATION PREFERANCE
Behaviour evidence of decreased
vision in right eye.
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.

22. When the left eye is covered , the child
objects & tries to move the examiner’s
hand.
When the right eye is covered, the child
does not object & tracks the object

23. 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.

24. ‘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

25. 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.

26. 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 mths .
There are cards available of various
thickness of lines .

27. 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 .

28. Lea paddle

29. References…
Theory and practice of optics and
refraction—A.K Khurana
Clinical visual optics.
Internet.

30. THANK YOU……