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DEVELOPMENT O F VISION
MANOJARYAL
InstituteOf Medicine
MaharajgunjMedical College
Introduction
 The human visual system is not fully developed at
birth :rather it matures over the first several years
of life.
 It includes:
 Development of anatomical structures
 Development of refractive errors
 Development of grating acuity
 Development of other visual attributes.
Developmentofanatomicalstructures
 At birth axial length :17mm ,70 % of adult size.
 Volume of orbit is only 50% of adult.
 Cornea is flat at birth ,becomes steepes 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
4mths. 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
months after birth.
Visualcortexdevelopment
oculardominance
 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
 Category1cellsreceiveinputfrom onlythecontralateraleye.
 Whereas category7receiveinputfromonlytheipsilateraleye.
 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 7are dominated by
ipsilateral eye.
DavidHubelandTorstonWieselExperiment
Experiment on kitten:
 They sutured one of a
kittens eye lids closed
at birthand recorded
from striate cortex
after animal has fully
matured
 Striate cortex of
monocularly deprived
animal is very different
from that of a normal
animal.
2 3 4 5 6 7
Ocular dominance
Num
ber
of
cells
contralateral ipsilateral
 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.
Criticalperiod
 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)
DevelopmentalPlasticity:
monoculardeprivation
 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
Developmentofrefractiveerrors
 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.
Animalstudiesonmonkeys,catsandchickenshave
shownthat:
 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.
Developmentofgratingacuity
 Resolution acuity of 1 month old infant as
measured behaviorally with spatial grating is
on the order of 20/600.
 Adult levels are reached by about 3 to 5 years
of age.
 Procedures used to assess grating acuity in
infants include:
 Optokinetic nystagmus
 Preferentiallooking
 Visuallyevokedpotential.
 Optokinetic nystagmus:
 A moving grating produces nystagmus.
 Consist of slow following movement
followed by fast compensating eye
movements(saccade)
 Depend upon the ability to resolve the
gratings.
 Used to assess visual capabilities in
uncooperative children, including
infants, malingers and mentally
retarded.
 Preferential looking:
 When given a choice between
patterned and non patterned stimulus
infants prefer to view the patterned
stimulus ,this behavior is known as
preferential looking.
 Used to determine infants grating
acuity.
 Both patterned and non patterned
stimuli have same average luminance
Eliminating luminance as cue.
 If examiner is required to guess which side the
pattern is on ,procedure is referred as Forced
Choice Preferential Looking.
 Alternative of preferential looking involves the
use of Tellers grating acuity cards.
 Studies using Tellers acuity cards
reveals:
 Healthy 1 month infants have acuities of
about 20/600.
 Resolution acuity improves rapidly during
first year of life.
 1 year child manifesting acuities of about
20/100
 Adult level of 20/20 acuity are not
reached until 3 to 5 year of age
Visuallyevokedpotential
 FPL suggest that adult
level of resolution
acuity are reached
between 3 to 5 year of
age .
 VEP show adult level at
6 to 8 months.
Monocular visual acuity as a function of age as
determined by tellers acuity cards
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
Causeofdecreasedvisualacuityintheinfant
 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
Developmentofothervisualattributes
 Contrast sensitivity:
 CS for 1 month old infants does not have band pass
form suggesting that lateral interconnections within
retina have not yet fully developed.
 As infants mature .CSF assumes a band pass form
and shifts to the right and upward indicating
Increasedcontrastsensitivity formost spatialfrequencies and
improved visualacuity.
 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
1 month
2 month
3 month
 Vernier acuity:
 Form of hyper acuity
 Matures rapidly during the first year
 Reaching adult level at slightly older age
(6-8 year of age)than grating acuity
 Depend on cortical processing ,it reaches
adult level later in life.
Developmentofbinocularvision
 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.
 By age of 6 months ,str.dev. enough to establish
BSV.
 Physiologically :
 At birth
 Compensatory reflex present
 At 2-3 months
 Orientation reflex ,refixation reflex ,pupillary reflex
vergene reflex are present
 At 2-3 yrs
 Accomodation reflex, fusional vergene reflex
present
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
 Color vision:
 By 2 year ,can match colors
 Infants (younger than 3 month) are less
sensitive to blue than adults
 Infants preferred red, green, and yellow
pattern
 By 2-3 month color vision close to adults.
Developmentofbinocularmotionprocessing
 Magnocellular neurons appears earlier in
dev. than parvocellular neurons.
 Magnocellular pathway at birth is biased so
as to respond preferentially to target that
move in temporal to nasal direction in the
visual field.
Developmentofvergence
 Vergences becomes remarkably accurate by
age of 6 months
 Vestibulo-ocular reflex -present at birth
,which stabilizes the eye when the head
assumes different static position or the
body turns
 Temporal vision: critical
flicker fusion frequency
 40 Hz at 1 month of age
 Reaches adult level of
about 55hz by 3 months
Retinal and cortical
immaturities that slow
the development of
grating and vernier acuity
apparently have little
effect on the maturation
of temporal resolution.
 Scotopic sensitivity:
 Adult like at 1 month of age.
 The absolute sensitivity of the scotopic
system(i.e. the sensitivity for a stimulus of
507 nm presented under conditions that
maximize scotopic sensitivity) apparently
reaches adult levels by about 6 month of
age.
 Face processing:
 Capable of discriminating between two
monkey faces as well as two human faces by
6 month
 Older infants and adults are less capable of
discriminating between the two monkey
faces.
revealing that the ability to distinguish
among faces become more specialized as an
infant matures.
VisualDevelopmentMilestones
 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 2
years
Summeryofvisualdevelopment
 CFF and the forms of scotopic and photopic
sensitivity functions showing adult like
characteristics with in the first 6 month.
 Stereopsis and color vision emerges with in 3
month of life and reaches adult level within the
1st year .
 Grating and vernier acuity improve rapidly
during the first year, but then slowly mature
until the child is 3 to 5 and 6 to 8 year old
respectively.
 The different
rates of
maturation for
the various visual
functions are
consistent with
notion that each
has a different
critical period.
Time frame for develipment of various visual
attributes.
Dot line: period over which adult or near adult
level of performance are obtained
Dashed line: red/green color vision may
continue to develop until aldolescence
Expectedvisualperformances
 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
Expectedvisualperformances
 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)
Expectedvisualperformances
 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)
Expectedvisualperformances
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)
Contd.
Expectedvisualperformances
 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)
Expectedvisualperformances
 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)
Expectedvisualperformances
 12 months to 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)
Expectedvisualperformances
 24 months to 36 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)
Expectedvisualperformances
 24 months to 36 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)
Expectedvisualperformances
 40 months to 48 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)
Expectedvisualperformances
 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.
Abnormalitiesinvisualdevelopment
 Abnormalities such as:
 Strasbismus
 Ptosis
 Congenital cataract
Can lead to AMBLYOPIA
Amblyopia
 “lazy eye”
 Relatively common developmental disorder
 Reduced visual acuity in an otherwise
healthy and properly corrected eye.
 Associated with interruption of normal early
visual experience.
 Most common cause of vision loss in
cchildrens.
Visualdeficitsinamblyopia
 Reduced visual acuity defining factor
usually 20/30 -20/60
 Impaired contrast sensitivity.
prominent at high spatial frequencies
 Central visual field is generally most affected.
 Moderate deficit in object recognition and spatial
localization.
 Severe deficit in binocular interaction.
Subtypesofamblyopia
 Form Deprivation Amblyopia:
 Caused by a physical obstruction
 e.g., congenital or traumatic cataract,
corneal opacities, prolonged uncontrolled
occlusion
therapy.
 Refractive Amblyopia:
 Isoametropic amblyopia is caused by high, but
equal, uncorrected refractive error (e.g.,
astigmatism > 2.50 D; hyperopia > than 5.00 D;
myopia > 8.00D)
 Anisometropic amblyopia is caused by unequal,
uncorrected refractive error (e.g., astigmatism >
1.50 D; hyperopia > 1.00 D; myopia > than 3.00 D
 Strabismic Amblyopia:
 Caused by early onset of constant unilateral
strabismus
Riskfactors
 Strabismus
 uncorrected significant refractive error
 Physical obstruction along the line of sight
 Prematurity/low birth weight
 Retinopathy of prematurity
 Cerebral palsy
 mental retardation
 strabismus, or congenital cataracts
 Extraocular muscle surgery for early-onset of
esotropia
Management
 Basis for Treatment:
 Improving vision in the amblyopic eye
 Decreasing the risk of blindness in the
fellow eye
 Facilitating fusion and maintaining eye
alignment
 Developing normal binocular vision
 Available Treatment Options:
 Optical correction
(spectacles and/or contact
lenses)
 Occlusion (part-time or
full-time)
 Active vision therapy
Signsofabnormalvisualproblem
 Frequent inward, upward, or downward eye
turning.
 Excessive tearing of eyes.
 Squinting or frequent closing of one eye.
 Covering of one eye with hands when
looking a object.
 Drifting of one eye when looking at objects.
 Excessive rubbing of the eyes.
 Tilting of the head.
 Poor eye hand co-ordination.
 Abnormally white pupil.
 Dropping of lids.
Clinicalconsiderationofvisualdevelopment
 Conditions such as anisometropia ,congenital
cataract, strasbismus and ptosis may produce visual
deprivation that can lead to permanent visual loss in
the form of amblyopia.
 Bcz the visual system becomes hard wiring early in
life,it is important that these conditions be
diagnosed and treated earliest as possible.
This necessitates eye examination
early in life.
references
 Visual perception
 Adler’s physiology of eye
 internet

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Development Of Vision

  • 1. DEVELOPMENT O F VISION MANOJARYAL InstituteOf Medicine MaharajgunjMedical College
  • 2. Introduction  The human visual system is not fully developed at birth :rather it matures over the first several years of life.  It includes:  Development of anatomical structures  Development of refractive errors  Development of grating acuity  Development of other visual attributes.
  • 3. Developmentofanatomicalstructures  At birth axial length :17mm ,70 % of adult size.  Volume of orbit is only 50% of adult.  Cornea is flat at birth ,becomes steepes 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
  • 4.  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 4mths. after birth  Optic nerve head relatively full size after birth.  Myelination of Visual pathway uncompleted until 2yrs.of age
  • 5.  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 months after birth.
  • 6. Visualcortexdevelopment oculardominance  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
  • 7.  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.
  • 8.  Cells in categories 1 and 7 are monocular  Category1cellsreceiveinputfrom onlythecontralateraleye.  Whereas category7receiveinputfromonlytheipsilateraleye.  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 7are dominated by ipsilateral eye.
  • 9. DavidHubelandTorstonWieselExperiment Experiment on kitten:  They sutured one of a kittens eye lids closed at birthand recorded from striate cortex after animal has fully matured  Striate cortex of monocularly deprived animal is very different from that of a normal animal. 2 3 4 5 6 7 Ocular dominance Num ber of cells contralateral ipsilateral
  • 10.  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.
  • 11.  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.
  • 12. Criticalperiod  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.
  • 13.  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)
  • 14. DevelopmentalPlasticity: monoculardeprivation  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
  • 15. Developmentofrefractiveerrors  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.
  • 16.  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.
  • 17. Animalstudiesonmonkeys,catsandchickenshave shownthat:  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.
  • 18.  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.
  • 19. Developmentofgratingacuity  Resolution acuity of 1 month old infant as measured behaviorally with spatial grating is on the order of 20/600.  Adult levels are reached by about 3 to 5 years of age.  Procedures used to assess grating acuity in infants include:  Optokinetic nystagmus  Preferentiallooking  Visuallyevokedpotential.
  • 20.  Optokinetic nystagmus:  A moving grating produces nystagmus.  Consist of slow following movement followed by fast compensating eye movements(saccade)  Depend upon the ability to resolve the gratings.  Used to assess visual capabilities in uncooperative children, including infants, malingers and mentally retarded.
  • 21.  Preferential looking:  When given a choice between patterned and non patterned stimulus infants prefer to view the patterned stimulus ,this behavior is known as preferential looking.  Used to determine infants grating acuity.  Both patterned and non patterned stimuli have same average luminance Eliminating luminance as cue.
  • 22.  If examiner is required to guess which side the pattern is on ,procedure is referred as Forced Choice Preferential Looking.  Alternative of preferential looking involves the use of Tellers grating acuity cards.
  • 23.  Studies using Tellers acuity cards reveals:  Healthy 1 month infants have acuities of about 20/600.  Resolution acuity improves rapidly during first year of life.  1 year child manifesting acuities of about 20/100  Adult level of 20/20 acuity are not reached until 3 to 5 year of age
  • 24. Visuallyevokedpotential  FPL suggest that adult level of resolution acuity are reached between 3 to 5 year of age .  VEP show adult level at 6 to 8 months. Monocular visual acuity as a function of age as determined by tellers acuity cards
  • 25. 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
  • 26. Causeofdecreasedvisualacuityintheinfant  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
  • 27. Developmentofothervisualattributes  Contrast sensitivity:  CS for 1 month old infants does not have band pass form suggesting that lateral interconnections within retina have not yet fully developed.  As infants mature .CSF assumes a band pass form and shifts to the right and upward indicating Increasedcontrastsensitivity formost spatialfrequencies and improved visualacuity.
  • 28.  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 1 month 2 month 3 month
  • 29.  Vernier acuity:  Form of hyper acuity  Matures rapidly during the first year  Reaching adult level at slightly older age (6-8 year of age)than grating acuity  Depend on cortical processing ,it reaches adult level later in life.
  • 30. Developmentofbinocularvision  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.  By age of 6 months ,str.dev. enough to establish BSV.
  • 31.  Physiologically :  At birth  Compensatory reflex present  At 2-3 months  Orientation reflex ,refixation reflex ,pupillary reflex vergene reflex are present  At 2-3 yrs  Accomodation reflex, fusional vergene reflex present
  • 32. 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
  • 33.  Color vision:  By 2 year ,can match colors  Infants (younger than 3 month) are less sensitive to blue than adults  Infants preferred red, green, and yellow pattern  By 2-3 month color vision close to adults.
  • 34. Developmentofbinocularmotionprocessing  Magnocellular neurons appears earlier in dev. than parvocellular neurons.  Magnocellular pathway at birth is biased so as to respond preferentially to target that move in temporal to nasal direction in the visual field.
  • 35. Developmentofvergence  Vergences becomes remarkably accurate by age of 6 months  Vestibulo-ocular reflex -present at birth ,which stabilizes the eye when the head assumes different static position or the body turns
  • 36.  Temporal vision: critical flicker fusion frequency  40 Hz at 1 month of age  Reaches adult level of about 55hz by 3 months Retinal and cortical immaturities that slow the development of grating and vernier acuity apparently have little effect on the maturation of temporal resolution.
  • 37.  Scotopic sensitivity:  Adult like at 1 month of age.  The absolute sensitivity of the scotopic system(i.e. the sensitivity for a stimulus of 507 nm presented under conditions that maximize scotopic sensitivity) apparently reaches adult levels by about 6 month of age.
  • 38.  Face processing:  Capable of discriminating between two monkey faces as well as two human faces by 6 month  Older infants and adults are less capable of discriminating between the two monkey faces. revealing that the ability to distinguish among faces become more specialized as an infant matures.
  • 39. VisualDevelopmentMilestones  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
  • 40.  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 2 years
  • 41. Summeryofvisualdevelopment  CFF and the forms of scotopic and photopic sensitivity functions showing adult like characteristics with in the first 6 month.  Stereopsis and color vision emerges with in 3 month of life and reaches adult level within the 1st year .  Grating and vernier acuity improve rapidly during the first year, but then slowly mature until the child is 3 to 5 and 6 to 8 year old respectively.
  • 42.  The different rates of maturation for the various visual functions are consistent with notion that each has a different critical period. Time frame for develipment of various visual attributes. Dot line: period over which adult or near adult level of performance are obtained Dashed line: red/green color vision may continue to develop until aldolescence
  • 43. Expectedvisualperformances  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
  • 44. Expectedvisualperformances  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)
  • 45. Expectedvisualperformances  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)
  • 46. Expectedvisualperformances 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) Contd.
  • 47. Expectedvisualperformances  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)
  • 48. Expectedvisualperformances  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)
  • 49. Expectedvisualperformances  12 months to 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)
  • 50. Expectedvisualperformances  24 months to 36 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)
  • 51. Expectedvisualperformances  24 months to 36 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)
  • 52. Expectedvisualperformances  40 months to 48 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)
  • 53. Expectedvisualperformances  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
  • 54.  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.
  • 55.  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.
  • 56. Abnormalitiesinvisualdevelopment  Abnormalities such as:  Strasbismus  Ptosis  Congenital cataract Can lead to AMBLYOPIA
  • 57. Amblyopia  “lazy eye”  Relatively common developmental disorder  Reduced visual acuity in an otherwise healthy and properly corrected eye.  Associated with interruption of normal early visual experience.  Most common cause of vision loss in cchildrens.
  • 58. Visualdeficitsinamblyopia  Reduced visual acuity defining factor usually 20/30 -20/60  Impaired contrast sensitivity. prominent at high spatial frequencies  Central visual field is generally most affected.  Moderate deficit in object recognition and spatial localization.  Severe deficit in binocular interaction.
  • 59. Subtypesofamblyopia  Form Deprivation Amblyopia:  Caused by a physical obstruction  e.g., congenital or traumatic cataract, corneal opacities, prolonged uncontrolled occlusion therapy.
  • 60.  Refractive Amblyopia:  Isoametropic amblyopia is caused by high, but equal, uncorrected refractive error (e.g., astigmatism > 2.50 D; hyperopia > than 5.00 D; myopia > 8.00D)  Anisometropic amblyopia is caused by unequal, uncorrected refractive error (e.g., astigmatism > 1.50 D; hyperopia > 1.00 D; myopia > than 3.00 D  Strabismic Amblyopia:  Caused by early onset of constant unilateral strabismus
  • 61. Riskfactors  Strabismus  uncorrected significant refractive error  Physical obstruction along the line of sight  Prematurity/low birth weight  Retinopathy of prematurity  Cerebral palsy  mental retardation  strabismus, or congenital cataracts  Extraocular muscle surgery for early-onset of esotropia
  • 62. Management  Basis for Treatment:  Improving vision in the amblyopic eye  Decreasing the risk of blindness in the fellow eye  Facilitating fusion and maintaining eye alignment  Developing normal binocular vision
  • 63.  Available Treatment Options:  Optical correction (spectacles and/or contact lenses)  Occlusion (part-time or full-time)  Active vision therapy
  • 64. Signsofabnormalvisualproblem  Frequent inward, upward, or downward eye turning.  Excessive tearing of eyes.  Squinting or frequent closing of one eye.  Covering of one eye with hands when looking a object.  Drifting of one eye when looking at objects.
  • 65.  Excessive rubbing of the eyes.  Tilting of the head.  Poor eye hand co-ordination.  Abnormally white pupil.  Dropping of lids.
  • 66. Clinicalconsiderationofvisualdevelopment  Conditions such as anisometropia ,congenital cataract, strasbismus and ptosis may produce visual deprivation that can lead to permanent visual loss in the form of amblyopia.  Bcz the visual system becomes hard wiring early in life,it is important that these conditions be diagnosed and treated earliest as possible. This necessitates eye examination early in life.
  • 67. references  Visual perception  Adler’s physiology of eye  internet