The document discusses several methods for testing visual acuity in infants and young children who are unable to participate in traditional eye charts. These include assessing a child's ability to follow objects, shine lights in their eyes to check pupil response, and use of visual evoked potential testing which measures the brain's response to different patterns. Preferential looking tests and optokinetic nystagmus testing are also explained as ways to evaluate visual acuity without a child's conscious responses.

1. Presented
By ,
SONU A.S

2.  The ability of a refractivity corrected eye
to discriminate fine details.
 It’s the is the resolving power of the eye.
 Primary measurement tool – chart
introduced in 1862 by Donders and
Snellen.
 Visual acuity is represented by Visual
Angle.
 Visual Angle – angle made by the object
with the nodal point of the eye.

3.  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.

4.  Chart illumination:
luminance level of minimum 12-20 foot
candles(130-215 lux).
 Testing Distance:
generally 6 meters.

5.  Response to light
An infant will blink in response to a bright light.
 Pupil response
Measuring the response of the pupil (the black
center part of the eye) by shining a penlight in
the eye is one way to test an infant's vision.
 Ability to follow a target
The most common vision acuity test in infants is
a test to check their ability to look at and
follow an object or toy.

6. 1. Very soon after birth – Can fix and follow a
light source.
2. 1 months – Fixation is central, steady and
maintained. Can follow a slow target.
3. 3 months – Binocular vision and eye
coordination.
4. 6months – Reaches out accurately for toys.
5. 9months – looks for hidden toys.

7.
 Visual Evoked Potential (VEP) Testing.
 Preferential Looking Test (PLT).
 OptoKinetic Nystagmus (OKN) Testing.
 Central Steady Maintain (CSM) Method.
 Cat ford Drum Test.

8. Parents or caretakers are asked routinely
whether the child responds to silent smile or
follows objects around etc.

9.  For those who are unable to read the letter
chart, the visual evoked potential (VEP) can
be used.
 It measures acuity by assessing the response
of the brain to alternating black and white
stripes or checks.

10.  To do the test, three small metal discs are placed on the
child's head.
 The discs are connected by wires to a computer.
 The child is then positioned in front of a TV screen
displaying alternating black and white stripes that
progressively get narrower.
 As the child views the stripes, a signal is relayed from
the eyes to the brain (the visual cortex).
 This signal is detected by the electrodes.
 The test is designed to find the finest black and white
stripes that reliably produce a response.

11.  Often the vision of each eye is tested separately; a
patch is used to cover the non-tested eye.
 The test typically takes less than an hour,
depending on the child's ability to cooperate.

12. 1. Patterns reversal VEPs.
2. Sweep VEPs.
3. Flash VEPs.

13.  The Preferential Looking test is used to assess visual
acuity in infants.
 who are unable to identify pictures or letters.
 The child is presented with two stimulus fields, one
with stripes and the other with a homogeneous gray
area of the same average luminance as the striped
field.
 The location of the stripes is randomly alternated.
 Typically, infants and children will look at the more
interesting stripes (if they can detect them) rather
than at the blank field.

14. In the diagram, the baby is shown in an infant seat; alternatively, the
child may sit on an adult's lap or be held over the shoulder. A small
peephole is centered between the two fields. An observer views the
child through the peephole and judges the location of the stripes
based on the child's head and eye movements.

15.  If the child can see the stripes, he/she will prefer to
look at them.
 If the child cannot see them, the striped field will
look the same as the blank gray field, and the child
will not show a preference.
 The smallest stripe width for which the observer can
consistently identify the location of the stripes is
considered to be the child's resolution threshold
(visual acuity).

16.  It is done with one eye fixation on an
accommodative target held at 40cm.
 ‘C’ refers to the location and corneal light
reflex as the patient fixates the examiners
light under monocular conditions.
 ‘S‘ refers to steadiness of fixation on
examiners light as it is held motionless and
also as it slowly moves up.

17.  ‘M’ refers to the ability of the path to
maintain alignment first with one eye then
with the other eye, as the opposite eye is
uncovered.

18. OPTOKINETIC NYSTAGMUS
(OKN) TESTING
 Nystagmus can be elicited using this test
 The only cooperation required in this test is that the
infant be awake and should hold both eyes open.
 Procedure: passing a succession of black and white
stripes through the patients field of vision. The visual
angle subtended by the smallest strip width that still
elicits an eye movement is a measure of visual acuity.
 Its reported that OKN acuity is at least 6/120 in the
newborns and improves fairly rapidly during the first

19. CATFORD DRUM TEST
 It is a detection acuity test, useful in infants and
preschool children
.
 In this test, the child 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.
 This test is unreliable since it overestimates the

20. THANKS