Visual development basics

VISUAL
DEVELOPMENT
Sachitanand Singh

• What is VISION?
Vision is a broader term than visual acuity or
eyesight. In addition to clarity of sight or simply a
description of the ability to see, the term "vision" all
interactions between the eyes and the brain, and all
neurological processes that take place in the brain to
make the sense of vision possible.

Eye health
Visual acuity
Refractive status

• Accommodation
• Binocular vision
• Eye movement skills

● Visual spatial skills
● Visual analysis skills
○ Form perception – ability to differentiate and recognise forms
○ Visual attention – the ability to focus consciousness on the requirements of a task.
○ Perception speed – the ability to perform visual processing tasks rapidly with
minimal cognitive effort.
○ Visual memory – the ability to recall visually presented material
● Visual motor integration skills

VISUAL DEVELOPMENT
• Visual development in a child is a very complex
process starting at an embryological age of as
less as 18 days.
• Development goes through a number of stages.
It is a composite function (motor system,
physiological development, cortical
development etc).

VISUAL PROCESSING
• Visual processing begins very early and
develops through infancy, pre school age and
schooling years.
• Visual processing involves vestibular and
cortical controls and development.
• Interference with development of any of the
interfaces results in the functional visual
processing being affected.

Cont...
• Visual requirements for academics are highly motor in
function.
• If this faculty is affected, then academics suffer
considerably. For example if the ocular movements
are not smooth and accurate, it may lead to inability to
read properly. If the balance mechanism (vestibular) is
poor, then the child may develop problems with
oculomotor functions.

VISUAL DEVELOPMENT
• Visual development can broadly be divided into
1. Anatomical development
2. Oculomotor development (in coordination with the
vestibular development)
3. Physiological development in the form of visual
acuity, accommodation, binocularity, ocular
movements and color perception.
All these factors combine to enable visual processing
which is of paramount importance in academic
performance.

Anatomical development
▪ At birth axial length :17mm ,70 % of adult size.
▪ Volume of orbit is only 50% of adult.
▪ Cornea is flat at birth ,becomes steeper as age
increases.
▪ Lens accommodation occurs at 1 month of age,
becomes more regular at 2-3 months, almost
adult like range by 6 months
� 14-16D at birth

▪ Muscle insertion and their relationships to the
limbus and equator change dramatically within 1st
yr of life.
▪ Differentiation of fovea occurs relatively late than
other parts of retina -incomplete until 4 months.
after birth
▪ Optic nerve head relatively full size after birth.
▪ Myelination of Visual pathway uncompleted
until 2yrs.of age

▪ Peripheral retinal development:
�Between 8 to 9 month of gestation development of
temporal retinal region complete.
�Indentation of peripheral retina in other regions of
globe continues to develop after birth.
�Zone between ora -serrata and equator enlarges in
size until about 2 year of age.
�Retinal vascularization:
Proceed from centre to periphery .
Mature pattern of vascularization-3 month after

Visual cortex development ocular
dominance
▪ Most neurons in visual cortex are binocular,
receiving input from both eyes.
▪ However, most neurons do not receive equal
input from two eyes: one eye tend to dominate
a given cortical cell
Ocular dominance Can be illustrated with an ocular
dominance histogram

� Cells in categories 1
and 7 are monocular
� Category 1 cells
receive input from
only the
contralateral eye
.
� Whereas
category 7
receive input from
only the ipsilateral
eye.

▪ Cells in categories 1 and 7 are monocular
� Category 1 cells receive input from only the contralateral
eye.
� Whereas category 7 receive input from only the
ipsilateral eye.
▪Neurons in category 4 are binocular and
receive input from both eyes.
▪Neurons in category 2 and 3 are dominated by
the contralateral eye and those in categories 5
and 7 are dominated by ipsilateral eye.

David Hubel and Torston Wiesel
Expt..
Experiment on kitten(Cat):
� They sutured one of a
kittens eye lids closed at
birth and recorded from
striate cortex after animal
has fully matured
� Striate cortex of
monocularly deprived
animal is very different from
that of a normal animal.
Number
of cells
1 2 3 4 5
6 7
Ocular dominance
Contralateral

▪ Virtually all cells are monocular and
responsive only to the nondeprived eye
▪ Conclusion:
▪ For striate cortex to develop a normal
complement of binocular cells , it is necessary
for both eyes to provide input during
development.

▪ Hubel and Wiesel work suggest that :
�During critical period the two eyes compete
with each other to dominate cortical neurons.
If both eyes have equal retinal image ,then
most of cortical neurons becomes binocular.
�When one eye wins out in competition as a
consequence ocular dominance.

Critical period
▪ Synaptic connection in cortex is
strengthened by neural activity.
▪ The geniculate neurons with input from non
deprived eye will stimulate cortical cell more
than from deprived eye.
▪ There is strengthening of synapses for non
deprived eye relative to deprived eye.

▪ The period during which the visual
system can be influenced by
environmental manipulation is referred
as the critical period or sensitive period.
▪ The human critical period is over by about 7 to 9
years of age.(vaegan and Taylor 1980)

Developmental Plasticity: monocular
deprivation
▪ Visual system is plastic
early in life,it becomes hard
wired later in life
▪ From birth to about 12 year
the visual system is still
flexible to change

Development of refractive errors
▪ The average newborn infant to be hypermetropic with
a mean refractive error of around 2D .
▪ A rapid decline in hypermetropia occurs between six
months and two years in normally developing eyes.
▪ A further, decrease towards emmetropia is then seen
up until the age of six years
▪ Later, in teenage years there is a tendency for the
number of children with myopia to increase.

▪ The correction of refractive error in infants
and toddlers is controversial because
Lenses could be potentially interfere with
emmetropization.
▪ The prescription of minus lenses for myopia lead to
near defocus ,there by promoting the development
of additional amount of myopia.
▪ Spectacle correction of clinically significant
amount of hyperopia in infants does not interfere
with emmetropization.

Animal studies on monkeys, cats and chickens
have shown that:
▪ Eyes in which the retina is allowed to receive light,
but no form vision (form deprivation), tend to
become highly myopic
i.e. the disruption of normal visual experience
leads to a breakdown in the emmetropisation
process.

▪ This myopia can be reversed if normal viewing
conditions are resumed, as long as this occurs
within a critical period” of development
▪ Human infants born with ocular pathology, e.g.
cataract, tend to develop high myopia and have a
much wider spread of refractive error.

Development of grating acuity
▪ Resolution acuity of 1 month old infant as
measured behaviorally with spatial grating is on the
order of 20/600.
▪ Resolution acuity improves rapidly during first year
of life.
▪ 1 year child manifesting acuities of about 20/100
▪ Adult levels are reached by about 3 to 5 years of
age.

▪ Procedures used to assess grating acuity in
infants include:
� Optokinetic nystagmus
� Preferential looking
� Visually evoked potential.

Technique Birth 2 months 4 months 6 months 1 yr Age for
20/20
OKN 20/400 20/400 20/200 20/100 20/60 20-30
months
FPL 20/400 20/400 20/200 20/150 20/50 18-24
months
VEP 20/800 20/150 20/60 20/40 20/20 6-12
months
OKN – Optokinetic nystagmus
FPL – Forced preferential looking
VEP – Visual evoked potential

Cause of decreased visual acuity in the infant
▪ Foveal cone immaturities
cone attain adult density & size of cones by 4
years age
▪ Cortical immaturities
▪ Incomplete myelination of the optic pathways
complete myelination of the optic nerve & optic
pathway takes >2 years

DEVELOPMENT OF VISUAL ACUITY
• If the child is unable to visualize due to any cause,
then the learning process is devoid of or reduced
visual perception. This leads to difficulty in learning.
• Reduced visual acuity is not a great hindrance in the
initial years, as the print that the child is expected to
see is big.
• However, as he grows, he is expected to read smaller
and closely printed matter. This affects the reading
and learning process.

Development of binocular vision
▪ It is felt that up to 2 months, the infant has predominantly
monocular fixation, with binocular fixation emerging at the
beginning of 3rd month.
▪ Vergences also begin to develop after 3 months.
▪ Becomes establish during 1st few year of life.
▪ Binocular cortical function 1st emerges at 3-5 months.
▪ Anatomically-After birth
� Retina & fovea are not fully developed visual perception
-poor
� Ciliary muscle not fully developed until 3 years.
� Medial rectus more developed than other muscles.

ACCOMMODATION
• This enables the child to focus the object
after fixating.
• An infant accommodates up to 19 cm at 1
month, which improves to about 10 cm at
4 months of age.
• However, the depth of focus is greater at 1
month, which decreases with improvement
in accommodation.

ACCOMMODATION
• In the beginning, as the print type is large,
and lessons are short, asthenopic
symptoms do not appear.
• However, in the later stages, fatigue,
reduction in reading efficiency, intermittent
blur, mild headaches etc manifest as
symptoms.
• These lead to avoidance of reading tasks,
which affect academics.

OCULAR MOVEMENTS
• Ocular movements are seen beneath the fused lids of
fetus even at the gestational age of 16 weeks.
• Pursuits are elicited in an infant at the age of 2 months.
However, they are not smooth and comprise of multiple
saccadic motions.
• They become smooth and regular following movements
over a period of time.
• Saccadic movements develop at the age of 2 months in
an infant.
• They too become more accurate and more peripheral as
further development takes place.

OCULAR MOVEMENTS
• An accurate oculomotor control is essential for learning
to read, which a precursor to reading to learn is.
• Accurate pursuit and saccadic movements are required
to read and follow the text.
• This is also required for phonic analysis of words and
maintenance of attention.
• Improper oculomotor control may lead to skipping of
words or lines affecting reading comprehension.
• At a higher level Arithmetic can also get affected due to
improper arrangement of numbers in columns, leading to
miscalculations

PHYSIOLOGICAL
DEVELOPMENT
• Visual development occurs as the neurological
development is taking place at prenatal as well as
infancy stages.
• A child experiences and undergoes a number of primitive
survival reflexes during this process of development.
• These primitive reflexes cease to persist after the
required development has taken place.
• These reflexes are directed from the brainstem.
• These reflexes are closely linked to the vestibular
system which is fully myelinated in utero.

MORO REFLEX
• It emerges in utero at 9 – 12 weeks and
should cease at about 4 months after birth.
• It is tested by moving the head
backwards.
• This movement elicits reflex extension of
limbs, rapid intake of breath and opening
of the hands.
• After a momentary freeze, the body is
released and then they cry.

MORO REFLEX
• If this reflex persists beyond 4 months, it
leads to the child being sensitive to
movements and other physical changes
like sound, temperature etc.
• This child may have difficulty paying
attention in a classroom setting and
traditional learning may prove difficult.

PALMAR REFLEX
• It emerges at around 11 weeks in the
fetus.
• Slight pressure on the palm results in
fingers crossing.
• It ceases after 3 months of birth.
• Palmar reflex is the precursor for pincer
grip.
• Its persistence may give rise to problems
with the speech and muscle coordination.
COLOR VISION AND PER

PALMAR REFLEX
• Pincer grip teaches a child to hold a pencil and
also handling of objects in a coordinated
manner.
• An appropriate grip is when the thumb and the
index finger come together to hold an object
(e.g. Pencil).
• If this is not learnt properly then it may lead to
problems with hand writing and may even lead
to immobilization of the wrist.
• A child learns to write as fine motor skill which
has evolved from gross motor skills.

TONIC LABYRINTHINE REFLEX
• It emerges at 16 weeks in utero.
• It is tested by moving the head backwards and
forwards eliciting limb extension and flexion
respectively.
• It works in coordination with the vestibular
system.
• It provides an adjustment response to gravity.
• It ceases a few weeks after birth. If it persists,
the child may not attain compensatory
mechanism against gravity leading to
oculomotor malfunctioning.

ASYMMETRICAL TONIC NECK
REFLEX
• It starts at about 16 weeks in utero.
• It is tested by rotating the head to one side, eliciting
extension of limbs on the same side and flexion in the
opposite side.
• It provides eye hand coordination and awareness of
distance to the child.
• This reflex must cease at around 6 months of age.
• In the absence of its phasing out, there is an interference
with the cross pattern movements like crawling, walking
etc.
• It also creates problems with visual tracking, hand
writing, eye hand coordination activities etc.

SYMMETRICAL TONIC NECK
REFLEX
• This starts at about 6 – 8 months post birth and
phases out about 3 – 4 months later.
• It enables the child to raise its body against
gravity with support of hands and knees.
• With this reflex, the child learns about the visual
space, perception of distance and near and also
binocularity.
• Its persistence leads to interference with cross
pattern creeping, visual space expansion, near
vision development and binocularity.

FUNCTIONAL VISION
• The functional vision operates in 3 basic ways:
1. Skeletal
2. Visceral
3. Cortical
The skeletal part fixates at an object, visceral part
focuses it and finally the cortical part forms a
single percept and interprets it. Any failure in this
coordination results in malfunctioning of the
functional visual apparatus.

Stereopsis:
�Rapid onset between 3 and 6 month
�Sensitivity to crossed disparities appears 3 weeks
earlier than uncrossed disparities
�In 1-3 months ,infants do not alternately
suppress each eye but instead superimpose
images
�At 3 month ,begin to show binocular fusion .
�Reaching 1 minutes of arc by 6 months

▪ Peak of CSF is at
adult location at
about 4 years
and overall
function is adult
by 9 years.
CSF shifts upward and to the right as
infant matures reaching adult form and
location at about 9 year of age
2
month
1
month
3
month

▪ Color vision:
�By 2 year, can match colors
�Infants (younger than 3 month) are less
sensitive to blue than adults
�Infants preferred red, green, oranges,greens,
blues and yellow pattern
�By 2-3 month color vision close to adults.

COLOR VISION AND PERCEPTION
• Improper color vision can lead to poor perceptual
skills.
• Initially, poor perceptual development may affect word
recognition, matching shapes, directional problems,
laterality problems etc.
• Later, visual spatial perception becomes important in
understanding spatial relationships geometry and
trigonometry.
• Spelling errors that are sound based suggest visual
perception deficiencies.

Visual Development Milestones
▪ Pupillary light reaction – 30 weeks gestation
▪ Saccades well developed – 1-3 months
▪ Ocular alignment stabilized – 1 month
▪ Smooth pursuit well developed- 6-8 weeks
▪ Blink response to visual threat – 2-5 month

▪ Fixation well developed – 2 months
▪ Accommodation appropriate to target – 4 months
▪ Foveal maturation – 4 months
▪ Stereopsis well developed – 3-7 months
▪ Contrast sensitivity function well developed -7
months
▪ Optic nerve complete myelination – 7 months to 2years

Expected visual performances
▪ Birth to 6 weeks of age:
∙ Stares at surrounding when
awake
∙ Momentarily holds gaze on bright
light or bright object
∙ Blinks at camera flash
∙ Eyes and head move
together
∙ One eye may seem turned in at
times

▪ 8 weeks to 24 weeks:
∙ Eyes begin to move more widely
with less head movement
∙ Eyes begin to follow moving
objects or people (8-12 weeks)
∙ Watches parent's face when being
talked to (10-12 weeks)
∙ Begins to watch own hands (12-16
weeks)

▪ 8 weeks to 24 weeks:
∙ Eyes move in active
inspection of surroundings
(18-20 weeks)
∙ While sitting, looks at hands,
food, bottle (18-24 weeks)
∙ Now looking for, and
watching more distant
objects (20-28 weeks)

30 weeks to 48 weeks:
∙ May turn eyes inward while
inspecting hands or toy (28-32
weeks)
∙ Eyes more mobile and move with little
head movement (30-36 weeks)
∙ Watches activities around for longer
periods of time (30-36 weeks)
∙ Looks for toys s/he drops (32-38
weeks)

∙ Visually inspects toys s/he can
hold (38-40 weeks)
∙ Creeps after favorite toy when
seen (40-44 weeks)
∙ Sweeps eyes around room
to see what's happening
(44-48 weeks)
∙ Visually responds to smiles
and voice of others (40-48
weeks)

▪ 12 months to 18 months:
∙ Now using both hands and visually steering
hand activity (12-14 months)
∙ Visually interested in simple pictures (14-
16 months)
∙ Often holds objects very close to eyes to
inspect (14-18 months)

∙ Points to objects or people
using words "look" or "see"
(14-18 months)
∙ Looks for and identifies
pictures in books (16-18
months)

∙ Occasionally visually inspects without
needing to touch (20-24 months)
∙ Smiles, facial brightening when views
favorite objects and people (20-24 months)
∙ Likes to watch movement of wheels, etc. (24-
28 months)
∙ Watches own hand while scribbling (26-
30 months)

∙ Visually explores and steers own walking and climbing
(30-36 months)
∙ Watches and imitates other children (30-36 months)
∙ Can now begin to keep coloring on the paper (34-38
months)
∙ "Reads" pictures in books (34-38 months)

∙ Brings head and eyes close to page of
book while inspecting (40-44 months)
∙ Draws and names circle and cross on
paper (40-44 months)
∙ Can close eyes on request, and may be
able to wink one eye (46-50 months)

▪ 4 years to 5 years:
∙ Copies simple forms and some letters
∙ Can place small objects in small openings
∙ Visually alert and observant of surroundings
∙ Tells about places, objects, or people seen elsewhere

▪ School –Age children's:
�Clear near vision for reading and
comfortably viewing close objects.
�Binocular vision or the ability to use both
eyes.
�Eye movement skills in order to
accurately aims the eyes.
�Focusing ability to keep both eyes
clearly focused at various distances.

▪ School –Age children's:
�Peripheral vision to be aware of objects
located out of direct view
�Eye hand co-ordination to accurately use
the eyes and hand together.
�Eye-body co-ordination to visually guide
body movements.

References
1. Visual perception
2. Adler’s physiology of eye
3. Internet
https://fitzroynortheyecentre.com.au/visual-perceptual-
assessment

Visual development basics

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