This ppt explain about Stereopsis in infants and its development in relation to visual acuity and the different types of stereo tests

1. STEREOPSIS IN INFANTS AND ITS
DEVELOPMENT IN RELATION TO
VISUAL ACUITY
RESHMA S SURESH

2. Stereopsis
• Clinical tests for stereopsis currently available require verbal interactions that are
unreliable in patients less than 2.5 years of age
•Testing stereopsis in young children is important for assisting in the identification
and progression of amblyopia, strabismus and significant refractive error
•A study by Shea et al. (1980) is based upon generating a random-element
stereogram in real time on a modified color video monitor that presents the
stereogram as an anaglyph
•The stereoscopic form can be moved about in stereoscopic space without the
introduction of monocular cues, and these movements can be used to engage in
infants visual attention

3. •If the infant’s eye movements and other attentive behavior are correlated with
the movement of the stereoscopic form, then the infant is having the capacity of
stereopsis
•Using this method they have found that stereopsis does not emerge until the
third or fourth postnatal month
•Infants have been reported to respond to coarse disparities present in dynamic
random-dot stereograms by their fourth month of life
•A study by R Held (1980) applied a new procedure using line stereograms
•It showed that stereoacuity of one degree is measurable by the fourth month
and that it rapidly improves to at least one sec of arc by the fifth month
•Stereograms were used in order to eliminate the parallax motion that is
produced by movements of the head in relation to a real object

4. Visual cliff – Experiment for depth
perception
Visual cliff designed by Eleanor Gibson and Richard Walk (1960) was used in
the studies of depth perception
Their apparatus consisted of a 'bridge' either side of which was a sturdy glass
platform
One side of this had a chequered pattern immediately under the glass (the
'shallow side'). On the other side of the bridge was a 'cliff' - the chequered
pattern was beneath a vertical drop
36 infants ranging in age from six months to 14 months.
Infants were placed at the edge of the visual cliff and had their mother coax
them to crawl on to the glass

5. The independent variable (IV) was whether the infant was called by its mother
from the cliff side or the shallow side (of the visual cliff apparatus).
The dependent variable (DV) was whether or not the child would crawl to its
mother.
Most infants readily crossed the shallow side and most reacted with fear to the
deep side – indicating infants can perceive depth
6-12 months old infants had extensive visual experience
2-4 months old showed variation in heart rate when directly placed on the
deep side

7. Tests for stereopsis
Name of the test Age
Lang Stereo test (Random dot) 8months – 2.5 years
The TNO test 2.5-3 years
Frisby Stereo test 3-12 years
Titmus fly test 4-18 years
The Randot test 3-15 years

8. The Lang stereo I and II test
•1983, Joseph Lang
•Stereopsis screening in children
•It is based on random dot principle
•The Lang test card was held by the examiner directly
in front of the child
•Positive responses, demonstrated by correct pointing
or an attempt to grasp one of the shapes
•The patient has to locate Cat (1200 arc sec), Star
(600), Car (550) for Lang I
•The patient has to locate the arc of the moon (200
arc sec), a star (200 arc sec), a car (400 arc sec), and
an elephant (600 arc sec) for Lang II

9. The TNO test
•Toegepast Natuurwetenschappelijk Onderzoek
•This test was developed for the Dutch military
as a screening test for stereopsis
•It consists of booklet containing seven plates
•Red and green glasses are required to
dissociate
•The first four plates are useful as the disparity
is large and provides a qualitative assessment
of stereopsis
•The fifth and seventh plate grades from 480 to
15 arc sec

10. The Frisby test
•Three plastic cards each containing four
squares of small random shape one of this
squares in each plate contains a hidden circle
which is seen in disparity
•The disparity is created by displacement of
random shapes by the thickness of the plate so
this test does not require use of glasses
•A disadvantage of this test is that if the plate or
child moves, motion parallax cues can reveal
the disk
•By using plates with three different thicknesses
viewed at nine different distances, 27
disparities between 5 and 600 sec of arc can be
presented

11. The Titmus fly test
•It consists of Fly, wirt circles, and animals.
•Done at 40cm
•Requires polarized glasses
•The contours of the circles are visible monocularly
especially at high disparities, making it possible
for a stereoblind child to solve atleast some of the
levels
•Sensitivity of Titmus is estimated at 63% for
strabismus and 38% for amblyopia, making the
test unsuitable for screening
•The test-retest repeatability is relatively poor, but
better than TNO test.

12. The Randot test
•Requires polarized glasses and done at
40 cm
•The test is a contour stereotest with the
associated monocular cues in the high
disparities
•The circles and animal subtests has
monocular cues
•The third subtest does not have
monocular cues

15. Are babies born with visual abilities?
 Babies are not born with all the visual abilities they need in life
The ability to focus their eyes, move them accurately and use them together as
a team must be learned
They need to learn how to use the visual information
 From birth - babies begin exploring the wonders in the world with their eyes

16. Visual acuity, in preverbal infants, is defined as a motor or sensory response to a threshold
stimulus of known size at known testing distance.

17. Steps in infant visual development
At birth, babies can't see as well as older children or adults.
Their eyes and visual system aren't fully developed.
It is important to remember that not every child is the same and some may
reach certain milestones at different ages.
Newborn’s visual acuity: 20/600. That is a new born can see clearly at 20 feet
what a normal adult can see at 600 feet (Schiffman, 2000)

18. Birth to four months
At birth - An infant is very sensitive to bright light. A newborn baby can see
something next to them with their peripheral vision, but their central vision is
still developing.
First months of life - eyes start working together and vision rapidly improves
Eye-hand coordination begins to develop as the infant starts tracking moving
objects with his or her eyes and reaching for them

19. Two months of life - babies begin to more easily focus their eyes on the faces of
a parent or other person near them
An infant's eyes are not well coordinated and may appear to wander or to be
crossed (usually normal)
- If an eye appears to turn in or out constantly - evaluation is warranted
Babies should begin to follow moving objects with their eyes and reach for
things at around three months of age

21. Five to eight months
These months - control of eye movements and eye-body coordination skills
continue to improve
Depth perception which is the ability to judge if objects are nearer or farther
away than other objects (not present at birth)
It is not until around the fifth month that the eyes are capable of working
together to form a three-dimensional view of the world and begin to see in
depth
They get better at reaching for objects both near and far

22. Infant's color vision is not as sensitive as an adult's - it is generally believed that
babies have good color vision by five months of age
Most babies start crawling at about 8 months old - which helps further develop
eye-hand-foot-body coordination

23. Nine to twelve months
At around 9 months of age - begin to pull themselves up to a standing position
By 10 months of age a baby should be able to grasp objects with thumb and
forefinger
By twelve months of age - most babies will be crawling and trying to walk
(Parents should encourage crawling rather than early walking to help the child
develop better eye-hand coordination)

25. One to Two years
By two years of age - a child's eye-hand coordination and depth perception should be well
developed
Children this age are highly interested in exploring their environment and in looking and
listening
They recognize familiar objects and pictures in books and can scribble with crayon or pencil.

27. REFERENCES
1. https://www.opticianonline.net/cpd-archive/4723
2. https://www.aoa.org/patients-and-public/good-vision-throughout-life/childrens-
vision/infant-vision-birth-to-24-months-of-age
3. https://www.aao.org/eye-health/tips-prevention/baby-vision-development-first-
year
4. Pediatric ophthalmology and strabismus, Kenneth W. Wright and Peter H Speigel
(second edition)
5. Broadbent H, Westall C. An evaluation of techniques for measuring stereopsis in
infants and young children. Ophthalmic Physiol Opt. 1990 Jan;10(1):3-7. PMID:
2184389