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Early Intervention
Training Center
for Infants and Toddlers With
Visual Impairments
Module:
Visual Conditions and Functional Vision:
Early Intervention Issues
Session 2: Visual Capacity
Major Points
A. Introduction to vision
Vision provides continuous and holistic information that is not available through any other
sense. Vision facilitates attachment between infant and caregivers and development of
social, communication, cognitive, and motor skills.
Of all of our receptors or senses, vision is the only one that provides holistic simultaneous
information that also allows or enables us to integrate information from all of our other
sensory systems (Hyvärinen, 2000). Vision enables infants to learn about people, objects,
and events in their world, encourages play behaviors, promotes visual imitation of skills
and activities of other family members, and facilitates social development and self-help
activities, including eating and bathing. Only vision and hearing enable young children to
experience people, objects, and events at a distance. Vision alone provides continuous,
simultaneous, and holistic information about the world beyond arm’s length (Hyvärinen,
2000).
Vision also plays a critical role in attention. For individuals with intact vision, visual cues
rather than sound, tactile, or olfactory cues typically determine our attentive focus. Visual
attention is closely tied to cognitive development and has been the subject of intense study
by developmental and cognitive psychologists (Atkinson, 2000; Johnson, 1991; Ruff &
Rothbart, 1996). Vision motivates us to stay awake, alert, and attentive to people, objects,
and events that are critical to our happiness and well-being. Vision allows infants to imitate
the actions and behaviors of important people in their lives and allows them to learn about
appropriate behavior within natural contexts.
Vision drives early nonverbal communication (Glass, 2002; Warren & Hatton, 2003).
Infants’ ability to see their caregivers’ faces and respond to smiles facilitates bonding,
attachment, and reciprocal interactions. Later, vision is used to establish joint attention to
key objects in the environment. According to Fazzi and Klein (2002), gestures or nonverbal
language comprise half of all communication between individuals, with verbal
communication comprising the other half. Vision allows infants to access incidental events
or clues from the environment; which provide anticipatory cues that prepare their nervous
systems for responding through motor actions such as eating, grooming, and playing
(Fazzi & Klein, 2002).
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Visual-motor skills, or eye-hand coordination, along with cognitive (or thinking) abilities,
enable infants to continually discover new things about the world around them. A critical
stage in visual and motor development occurs at around 4-6 months, when infants begin to
reach and grasp (Glass, 2002; Hyvärinen, 2000). They can then manipulate objects, and
because of the ability to focus on objects at varying distances, infants notice near and
distant objects.
The development of purposeful movement allows infants to actually move to enticing
people and objects in their environment. Physical control of the visual environment
provides infants with the opportunity to pair active touch and movement with visual
experiences so that they can explore their world and examine it deliberately (Hyvärinen,
2000). According to Hyvärinen (2000), infants acquire the following concepts and cognitive
skills as they manipulate objects:
 size constancy: objects retain their size even though they appear smaller at a
distance;
 shape constancy: objects remain the same shape even though their shapes might
appear to alter when viewed at different angles;
 depth cues: nearer objects overlap with those at a distance, light and shadow
effects; and
 figure-ground relationships: single figures can be visually selected from
backgrounds, and elements of a scene can exist at different distances from the eye.
Because there are critical or sensitive periods of experience dependent development in the
visual system during the first few years of life (Bruer & Greenough, 2001; Horton, 2001;
Tychsen, 2001), impairments to the visual system during this early period, even if
corrected, can permanently influence a child’s visual learning (Erin, Fazzi, Gordon,
Isenberg, & Paysse, 2002; Tavernier, 1993). Key visual structures and the early
development of vision in typically developing children will be discussed in the following
section.
B. Visual development
In typically developing children, visual development proceeds in a predictable pattern.
Sasha was born full-term without complications. Sylvia and Daniel, first-time parents, were
amazed at how quickly their newborn daughter seemed to visually appreciate her world.
As a newborn, she turned her head to look at light sources; developed eye contact with
family members within 6 to 8 weeks after birth; tracked the family dog, Buster; and looked
at the toys on her mobile. Sasha looked at her hands when she was 3 months of age.
Before long, Sasha was swiping at her mobile toys, shifting her gaze back and forth to look
at toys falling and rolling away, and shifting her gaze from the right to the left side to
choose which one of two toys that she wanted.
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Daniel was very surprised when Sasha, at 6 months of age, appeared to notice him from a
distance of more than 6 feet without him making a sound to catch her attention. A month
later, Sasha noticed small breadcrumbs and showed interest in pictures. She looked
through windows and recognized familiar people that did not necessarily live in the
household. Sylvia and Daniel noticed that as Sasha’s ability to sit and hold her head up
when on her stomach become steadier, her visual attention and skills also appeared to
improve.
Understanding the progression of visual development is important for several reasons.
First, it enables us to construct an accurate picture of the visual capabilities of typical
infants at various ages and provides an indication of the visual world in which the infant
lives. According to Hyvärinen (2000, p. 800), “the clinical evaluation of children with
different visual problems uses the visual function of an infant with normal sight as the
baseline reference.” Therefore, it is reasonable to expect that ECVCs who are
knowledgeable about typical vision development will be able to assess functional vision in
children with visual impairments and to recommend appropriate strategies to enhance
visual function. In addition, knowledge of the normal course of visual development helps
professionals to identify infants with atypical development that might reflect visual or
neurological impairments.
Research on the development of vision in animals and in humans with cataracts or other
early visual deprivation suggests that there are critical or sensitive periods of development
of the visual system (Bruer & Greenough, 2001; Horton, 2001; Hyvärinen, 2000; Tychsen,
2001). Consequently, if children are deprived of visual input early in life, they may not be
able to achieve full visual potential because they lack early visual experiences and
stimulation that are needed for the refinement of eye-brain connections that drive visual
function. Thus, the visual system depends on early experiences and stimulation for normal
development and is an experience-expectant system according to Greenough (Bruer &
Greenough, 2001). Early detection of defects may prevent or facilitate the treatment of
some visual disorders such as amblyopia and strabismus. For example, studies show that
infants whose congenital cataracts were removed prior to 8 weeks of age can achieve
normal visual development as measured by preferential looking techniques (Gelbert, Hoyt,
Jastrebski, & Marg, 1982; Rogers, Tishler, Tsou, Hertle, & Fellows, 1981).
Prenatal development
During the prenatal period, the visual system usually develops in an orderly manner
(Chandna & Noonan, 2000). On the twenty-first day of gestation, there is evidence of the
first signs of the developing eye (Cook, Sulik, & Wright, 2003). At 6 weeks’ gestation, the
optic nerve, called the optic stalk, begins to develop, and the upper and lower eyelid buds
grow together and elongate to cover the developing eye. Shortly before and after this time,
the oculomotor muscles develop. At 10 weeks’ gestation, the upper and lower lids are
fused together, but they gradually separate by 6 months’ gestation. At the same time, the
vitreous and retinal areas develop. By the seventh month, the inner layer of the retina
develops to form the central macular depression or primitive fovea. The foveal cones,
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Early Intervention
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however, will continue to change after birth. Rods outnumber the cones in density in the
mid-peripheral area before birth, and the parafoveal area shows mature rod
photoreceptors at birth, making them the principal photoreceptors in the far periphery.
Postnatal development
The visual system of the newborn is immature but functional at birth (Hyvärinen, 2000).
When a full-term baby is born, the eye is 75 to 80% of the size of an adult eye (Eustis &
Guthrie, 2003). The cornea is typically flat, causing the infant to be hyperopic or farsighted.
Within the first year, the cornea changes in size, shape, and appearance. It becomes
enlarged, thinner, and more transparent (Eustis & Guthrie, 2003). According to Eustis and
Guthrie (2003), optic nerve myelinization (i.e., the growth of sheath-like material that
serves as an electrical insulator) starts at 7 months’ gestation and is complete 1 month
after birth. However, the myelin layer is thin and will continue to develop throughout
childhood. The macula (i.e., the structure of eye that provides a sharp, clear central vision
that allows a person to see color and detail) is the least-developed ocular structure at birth.
Ophthalmologic exams show a seemingly mature macula at 42 weeks’ gestational age,
although it is not functionally mature until later in childhood (Eustis & Guthrie, 2003). The
density of retinal receptor cells called cones (used to detect details and discriminate
colors) located in the fovea (the area of the macula responsible for the sharpest vision) is
only one-third that of adults, and the cone length is one-tenth that of adults. The peripheral
retina is related to motion detection. The macula provides the “what” information while the
periphery provides the “where” information in vision. In addition, color changes occur in the
iris during the first 6 months of an infant’s life for children with blue, green, or gray eyes
(Eustis & Guthrie, 2003). Please see Handout A for a summary of early ocular
development.
Development of visual abilities and behaviors
Young children’s vision and visual systems mature in the months following birth (Eustis &
Guthrie, 2003; Hyvärinen, 2000). Both Teller (1997) and Dobson (1993) noted that infants
within the first 6 to 12 months demonstrate improved visual awareness, acuity, and
fixation, better control of eye movements, improved visual scanning, and integration of
information from vision and motor skills.
Although children are born with the ability to orient to objects and faces and detect
movement, these skills mature over the first 6 months of life as the cortical brain cells
experience an increase in responsiveness (Chandna & Noonan, 2000). Glass (2002) noted
that newborn infants attend to form, object, and face; are sensitive to bright light; and are
more visually responsive under low illumination.
Although newborns may not initially have a steady gaze, they are capable of focusing on
people and objects quite close to their face. As previously stated, infants are generally
farsighted at birth, and become less farsighted during the toddler and preschool years.
Before 2 months of age, infants' eyes have the ability to focus on distant objects as well as
close objects; but they do not focus very accurately (Hyvärinen, 2000). Infant eye
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movements are unsteady during the first few months; sometimes they will focus too close
(in front of the object) and sometimes too far (Hyvärinen, 2000). The ability to focus
accurately becomes more coordinated by the third month.
Eye contact with parents occurs at approximately 6 weeks (Erin & Paul, 1996; Hyvärinen,
2000) and usually no later than 8 weeks. Convergence develops between 3 and 6 months
and enables both eyes to work together to view objects near or far. Convergence is driven
by the infant’s ability to accommodate. Accommodation occurs when ciliary muscles
contract to increase the lens curvature to focus images on the retina. Any accommodation
will result in some convergence. Additionally, as the medial rectus muscles contract to
keep the eyes aligned and on-target, they converge as the pupils constrict to increase the
depth of focus (Wright, 2003a).
Binocular vision develops by 3 to 4 months of age (Johnson, 1997; Shea, Fox, Aslin, &
Dumais, 1980). At this age, most infants use both eyes together to receive a threedimensional image or stereopsis. Shortly thereafter, at 4 to 5 months of age, infants refine
their reach and grasp behaviors. Physical control of the visual environment provides
infants with opportunities to pair active touch with visual experiences, as previously
indicated.
Hall and Bailey (1989) studied the sequence of visual development of typical infants and
young children and described visual behaviors observed during the first 2 years. Handout
B provides an adapted version that may be useful in assisting families in identifying
whether the young child exhibits a variety of visual behaviors within natural environments.
For a detailed description of the development of visual function in infants, refer to
Developmental Guidelines for Infants With Visual Impairment by Lueck, Chen, and Kekelis
(1997).
Although infants’ ability to see detail at birth is not fully developed, it improves rapidly
during the first year (Hyvärinen, 2000). Newborn visual acuity, or ability to discriminate
detail, has been estimated to range from 20/400 to 20/600 depending upon the type of
assessment used (Eustis & Gutherie, 2003). The visual evoked potential (VEP) or visual
evoked response (VER) electronically measures electrical activity in the visual cortex
(occipital cortex) that results from the retinas’ response to stimulation. This information is
obtained from electrodes attached to the infant’s scalp during exposure to visual stimuli.
The VEP or VER is used to identify objects in the visual nerve pathway from the retina to
the brain. No motor response is required; however, VEPs cannot assess the children
cognitively process visual input. Forced-choice preferential-looking tasks such as the Teller
Acuity Cards (Vistech Consultants, 1990) require a motor response of looking at cards with
increasingly small gratings. Eustis and Guthrie (2003, pp. 50-51) provide the following
estimates of visual acuities during the preschool years.
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Development of Visual Acuity in Young Children
Newborn
3 months
Forced-choice
preferential
20/600
20/120
looking
Visual evoked
20/400
potentials
Eustis and Guthrie, 2003, pp. 50-51.
6 to 7 months
12 months
3 to 5 years
20/60
20/20
20/20
Preferential looking experiments with 1- to 5-day-old infants using the colors red, green,
yellow, and blue suggested that newborns can see red, yellow, and green but not blue
(Adler, n.d.). In these experiments, the infant was presented with a gray card with two
blocks of rectangular color on one side, and no color on the other. Teller (1997) theorized
that if infants see color, they will look at the color first and not at the gray area. According
to Teller (1997), the saturation or brightness of the colors has an impact on the infant’s
ability to detect color—the brighter the color in the warm-color spectrum, the more easily it
is detected by infants. For infants, the macula is more sensitive to higher wavelengths of
color in the red/orange/yellow color spectrum (Teller, 1997). According to Adler (n.d.), adult
like color perception develops as early as 2 to 4 months of age depending on the
saturation of the color.
The infant’s response to contrast sensitivity may be a useful indicator of ability to use
vision within activities of daily living. Contrast sensitivity, or seeing subtle shades of gray, is
underdeveloped at birth, but by 2.5 to 3 months of age, infants can see shades of gray
almost as well as adults, provided that the pattern size is large (Atchley, 1999). Overall
contrast sensitivity in infants increases as the efficiency and density of the cones at the
fovea improve (Chandna & Noonan, 2000).
In a detailed review of research on measured visual field extent, Mohan and Dobson
(2000) discussed issues related to the development of visual field and the challenges
inherent in measuring it. Variations in the assessment used (type of measure, size and
luminance of stimulus, etc.) may impact measurement results. In addition, the nasal and
upper visual fields may mature faster than the temporal and lower visual fields. Mohan and
Dobson noted that there is no doubt as to whether the visual field extent of infants and
toddlers is considerably different from that of adults. Nonetheless, measurement
confounds make it difficult to determine at what age visual fields reach adult like levels.
The large range in ages for adult like visual fields in very young children reported by
different researchers in the Mohan and Dobson review is notable, and this suggests that
we currently do not know when the entire visual field reaches an adult like status.
A description of visual behaviors depicting visual abilities drawn from developmental
psychology (Atkinson, 2000; Mohan & Dobson, 2000; Ruff & Rothbart, 1996) and pediatric
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ophthalmology (Eustis & Guthrie, 2003; Hyvärinen, 2000; Wright, 2003c) follows and is
also included as Handout C, “Development of Visual Behaviors and Skills” (Fox, 2003).
Table 2. Chronology of Visual Behaviors
Chronological
Age
At birth
Visual Behaviors















2 months








attend to different aspects of objects and events
track moving objects in a jerky manner that lags behind objects’
movement
appear to look through, not at, objects of interest
have short periods of visual alertness
have preference for moving targets and human faces
scan faces with fixation concentrated at the edges
have uncoordinated eye movements
have difficulty disengaging from visual targets
exhibit selective attention from first day of life
are aware of sources of light and will turn their heads and eyes
toward diffused light
attend based on intensity of stimulus—contour, size, and brightness
attend longer to patterns rather than blank fields of color
prefer patterns and objects that have large features, high contrast,
and borders
prefer patterns of curved, rather than straight, lines
need a period of familiarity and some degree of habituation before
shifting gaze
attend to attributes such as pattern and form
change looking during developmental transition
track more smoothly
are awake and looking around for longer periods of time
are more likely to focus on faces or bull’s-eyes regardless of size or
brightness of other alternatives
look at caretakers’ faces some of the time and other times fail to
establish eye contact, often looking at the hairline or edge of the face
have glassy or partly closed eyes during face-to-face interactions
scan objects for internal and external contours and larger distribution
of scanning space
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Chronological
Age
3 months
Visual Behaviors







4 months


5 months



6 to 7 months
7 to 10 months
9 months












reduce obligatory looking behaviors—infants are able to disengage
focus on visual target
change patterns of looking between 3 to 9 months, recognize
repeated events through looking
gain greater control of eye movements due to increased cortical
development
are more likely to make eye contact
see better due to maturation of the visual system
expand visual field and are therefore more responsive to shape and
events
develop strong visual preferences for novel objects at novel locations
at 3 to 6 months
increase amount of time looking at objects
acquire greater control over shift of gaze, making attention more
flexible
shift fixation across midline
develop binocular vision
begin to reach, grasp, and manipulate objects that engage their visual
attention
reach adult levels of visual acuity and binocularity with VEP
attend to small objects
make eye contact with adults at several feet
develop eye-hand coordination with small objects
coordinate visual joint attention with objects and adults more
effectively at 12 months
experience a major transition point in development
decrease time spent looking because they learn and habituate faster
are proficient in visual exploration of novel objects
shift visual attention from primary caregiver to objects
start looking toward their mother’s faces at a distance—social
referencing
begin using caregivers as a visual point of reference in ambiguous
situations
begin to imitate actions of others with a delay
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Chronological
Age
12 months
18 months
Toddler
24 months
Birth to 10
years
Visual Behaviors














attend more to novel objects and events
sustain attention for the purpose of exploring and learning
increase looking during play with an array of toys
change in selectivity as new skills and knowledge emerge
comprehend language sufficiently for it to direct visual attention
are skilled in following glances and gestures of others
have experiences in cognition and play that influence visual attention
base visual attention on what others attend to
develop sustained attention in naturalistic settings that increases as
they learn to play with toys or watch TV
attend to complex visual displays such as looking at TV
refine looking behaviors as cognitive skills increase
have focused visual attention that doubles in length of time
experience rapid improvement in visual field development in the first
year and then slower maturation the first 10 years (Eustis & Guthrie,
2003)
continue to mature until adult like visual field is attained—precise age
of attainment is uncertain (Mohan & Dobson, 2000)
Variations in visual maturation among children of similar chronological ages
In order to understand the differences in visual maturation among children of similar
chronological age, it is first important to know that infant visual development and
maturation occur rapidly during the first year of life as discussed earlier in this session. The
infant’s visual development, however, can be interrupted or modified by internal (e.g.,
sickness) or external (e.g., lack of opportunity to use vision) factors in the environment.
Infants may have reflexes and skills that do not appear to be within the typical range during
the first year. Visual abilities may appear to be advanced or delayed, yet still fall within the
typical range of development. The vignette below illustrates how two typically developing
infants differ in their rate of visual and visual motor development due to individual
differences.
Sylvia and Letty, best friends since junior high, each married and had their first child within
2 weeks of each other. Sylvia’s son, Raul, and Letty’s son, Kenny, were born at full term
with no complications.
Kenny looked at his mom’s and dad’s faces almost immediately when he came home from
the hospital. He was very visually interested in his environment from the moment he
became a member of the family. He seemed to notice shiny, bright reflections from glass
tabletops in the living room of the house. He swiped, reached for, and grasped bright toys
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as early as 3 months and was touching his mom’s and dad’s faces at the same time. At
about 5.5 months, he sat independently and reached for everything around him. He
appeared to notice events, objects, and people at distances beyond 6 feet at about that
same time. Kenny was interested in looking at bright pictures in books and ate small-sized
snack food from his highchair tray.
Raul demonstrated many of the same behaviors, but as Sylvia and Letty compared notes,
Raul’s timeline for demonstrating visual and visual motor behaviors occurred about 2
months later than Kenny’s demonstration of those skills. There was no medical explanation
for the differences, though they were both considered to be developmentally typical. At 18
months, both boys were demonstrating similar developmentally appropriate skills in the
visual and visual motor areas of development.
C. Atypical visual development
Visual impairment can result from prematurity or atypical development of particular ocular
structures that may limit visual capacity and result in atypical visual development. The
following table can also be found as Handout D.
Table 3. Congenital Structural Abnormalities That May Alter Visual Development
Name
Optic nerve hypoplasia
Source
Elston (2000)
Atypical development of
the optic nerve
Microphthalmia/
anophthalmia
Hertle,
Schaffer, &
Foster (2002)
Anophthalmia, absence
of the eye, and
microphthalmia, a very
small and typically
malformed eye, represent
structural abnormalities of
the globe
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Comments
 Occurs in the first or early second
trimester
 May be associated with young maternal
age, fetal alcohol syndrome, possible
maternal diabetes mellitus
 Children at increased risk of endocrine
disturbances
 Visual acuity may range from light
perception to normal acuity
 May result from insult at number of
developmental stages or from acute
exposure to toxins during early
development
 Could be due to failure or late closure of
optic fissure
 Microphthalmia may result in decreased
visual acuity, photophobia, fluctuating
visual abilities
 Anophthalmia results in total blindness of
affected eye
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Name
Coloboma
Failure of parts of the
ocular system to develop
due to abnormal fusion of
optic fissure
Congenital cataract
Source
Cook, Sulick,
& Wright
(2003)
Wright
(2003b)
Clouding or opacity of the
lens that produces
indistinct image on retina
Developmental
abnormality of the
anterior segment
Hertle,
Schaffer, &
Foster (2002)
Defective development of
structures near the front
of the eye—between
cornea and vitreous
Comments
 Defect occurs at 4 to 5 weeks’ gestation
 Can affect iris, choroid, retina, and optic
nerve
 When optic nerve or retina is involved,
vision is affected
 Isolated iris colobomas may not affect
visual acuity
 Decreased visual acuity, photophobia,
field loss often results from colobomas,
depending on areas that failed to develop
 May result from genetic/hereditary
conditions, maternal infection, systemic
diseases
 Treatment within the first few weeks of
life results in near normal visual
development
 Defects in these structures may result in
poor vision due to obstruction of light as it
passes through the cornea, pupil, or lens
 Defects in trabeculum (involved in
circulation/drainage of fluid in the eyes)
can result in primary glaucoma that can
cause vision loss due to damage of the
optic nerve
 Defects of iris (aniridia, coloboma) affect
pupil size and can cause blurred image,
poor focusing, and sensitivity to glare
Prematurity and visual development
Glass (2002) and Creger (1989) provided descriptions of the fetal eye of premature infants
during the third trimester. Their descriptions of ocular structures are summarized in the
following table and in Handout E. This information may be helpful to ECVCs who work with
infants and toddlers with retinopathy of prematurity (ROP) or cortical visual impairment
(CVI), two visual conditions associated with prematurity.
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Table 4. Development of Fetal Eye
Structure
24 to 28 Weeks
Eyelid
Lids are fused early in
development, and now
reopen.
Pupil
The tunica vasculosa lentis
begins to atrophy, and at
27 weeks, pupillary light
response can be observed.
Lens
By 27 to 28 weeks, the
lens is covered with
vessels in the anterior
capsule.
The second layer of the 4layer nucleus is
developing.
Media
The media is cloudy.
The hyaloid system begins
to regress.
30 to 34 Weeks
Eyelids are less
translucent.
Retina
Retina is complete
except for the foveal
region.
Visual
cortex
All retinal layers are
present by 22 weeks.
Rods (about 130 million),
important for low light and
peripheral vision, and
cones (about 6.5 to 7
million), important for
detail, central vision,
daylight, and color,
develop by 25 weeks, and
differentiation begins.
Vascularization is just
beginning.
Rapid growth and
differentiation of nerve
cells and dendrites occur.
At 28 to 32 weeks, the
optic nerve begins to
develop. At 14 to 22
weeks, the optic chiasm is
evident.
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36 Weeks
The second layer is
complete, and the third
begins to form.
Vessels of the anterior
capsule are completely
atrophied by 34 weeks.
The media clears.
The hyaloid has almost
disappeared.
Marked development of
dendritic spines and
synapses occurs.
The media is less
dense than in adults.
Some remnants of the
hyaloid may still be
present.
The number of cones
in the fovea increases.
The temporal region is
almost fully
vascularized.
The visual cortex
structure appears
similar to that of a fullterm infant.
The nerve, chiasm, and
optic tract all myelinate
over the next 2 years.
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Glass (2002) and Creger (1989) also described visual function in premature infants.
Although each infant is unique, these descriptions provide ECVCs with information that
may help them understand the range of visual behaviors observed in premature infants.
Table 5. Functional Visual Response of the Preterm Infant
Functional
Visual
Response
of the
Preterm
Infant
24 to 28 Weeks
Immature visual function is
present once the anatomic
pathway to the visual
cortex is complete.
A visual evoked response
is obtainable in bright light.
Lids tighten In bright light.
The infant is very
nearsighted.
30 to 34 Weeks
Pupillary reflex is
present.
36 Weeks
VEP response is like
that of a newborn.
Bright light causes
lid closure.
Vertical and horizontal
tracking to soft light
occur.
There is visual
attention to highcontrast forms under
low illumination
conditions.
The infant prefers to
look at patterns.
There is no refractive
error.
Premature infants tend to be more myopic at birth, especially when retinopathy of
prematurity is present (Eustis & Guthrie, 2003). Premature infants also have a smaller
pupillary aperture and, therefore, may or may not demonstrate a light response depending
upon the degree of prematurity (Eustis & Guthrie, 2003).
In a child born pre-term with medical complications or with a documented eye disease,
visual skills may emerge at a slower rate or in a different order. The rate of development
may be affected by the premature infant’s physiological or autonomic responses, motor
development, state control, attention, and self-regulation (Creger, 1989).
Charity was born at 24 weeks’ gestation and spent time in the neonatal intensive care unit
(NICU). She appeared to be overwhelmed by environmental stimuli, including the toys that
her family brought for her, and by being handled by the nursing staff. She was not able to
participate in the reciprocal interactions that infants usually engage in with their caregivers,
and thus was showing few if any visual gaze responses to familiar caregivers. At 34
weeks, Charity began to recover from her own agitation when left alone. Her parents were
then encouraged to assume many of the caregiving responsibilities. Charity was released
from the hospital a few days after her original due date and went home with her parents.
At about this time, her parents noted that her visual gaze and hand-to-mouth behaviors
were becoming more frequent, though they sometimes did not occur, depending upon
Charity’s state of alertness. Charity also visually responded to pastel-colored toys by
localizing and fixating on them more frequently than to the bright-colored toys that her
sister and brother had enjoyed at the same age. Again, Charity’s visual responses
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appeared to depend on her waking state, environmental factors, and attributes of the toys
and caregivers.
D. Physiology, environment, and visual development
Corn (1983, 1989) proposed a model of visual functioning with three essential components
for individuals with low vision, as shown in Handout F. These three components include
visual abilities, stored and available individuality, and environmental cues. ECVCs who
understand these physiological and environmental components and how they interact with
each other are better able to facilitate visual functioning in young children with visual
impairments (Erin, Fazzi, Gordon, Isenberg, & Paysse, 2002).
Visual abilities include
 visual acuity—nearpoint, midpoint, distance;
 visual field—central, peripheral, hemifields;
 movement of eyes—alignment, stability, and coordination of eyes (vertical, horizontal,
diagonal, crossing midline, and ability to use both eyes together);
 brain functions (cortical and subcortical)—physiological control of eyes and
processing/interpretation; and
 light and color perception—color, tolerance, light/dark adaptation.
Stored and available individuality includes
 cognition—intelligence, problem solving, communication, concept development,
memory, and experience;
 sensory integration—hearing, touch, taste, and smell;
 perception—part/whole, figure/ground, closure, and sequence;
 physical abilities—motor development, muscle tone, stamina, endurance, reaction time,
and general health; and
 psychological make-up—emotional regulation and stability, motivation, attention,
self-esteem, identity, and sociability.
Environmental cues may help young children with visual impairments use their functional
vision more effectively. Environmental cues include
 color,
 contrast,
 time,
 space/distance, and
 illumination.
When caregivers increase or decrease the intensity of each cue, children may be better
able to see a favorite toy that is not within arm’s reach. By encouraging the child to move
closer to the toy, space/distance is modified, and the child is more likely to see the toy. The
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following two examples demonstrate environmental cue alterations to support the child’s
ability to use vision within natural environments.
Takoda is accustomed to taking his bath in the kitchen sink. Stephanie, his mother, uses
the sink because it provides Takoda a sense of security that he did not have in the regular
bathtub. She noticed that when she adjusted the space (decreased size of tub), Takoda
did not cry or appear scared in the water during bath time. Takoda is attracted to the color
red, and his Winnie the Pooh shampoo bottle is bright red (color/intensity). Stephanie
allows Takoda to look at the red washcloth coming toward his face before washing him by
adjusting the amount of time she gives him to look at the cloth (time).
Sierra, a toddler with albinism, is sensitive to outdoor light. When asked to find her
brother’s bike in the backyard (familiar setting), Sierra was within a foot of it and walked
past it as she faced the bright sun. Her mother asked her to turn around and walk back
toward her to look for the bike. When the sun was at Sierra’s back instead of in her eyes
(illumination/glare reduction), she immediately noticed the bike after she turned around.
Although the bike was orange and had black tape wrapped around the handlebars,
providing high contrast, the glare and degree of illumination initially interfered with Sierra’s
ability to find the bike.
In addition to the components described above (Corn, DePriest, & Erin, 2000), infants’
visual development and functional use of vision are also impacted by biological factors
such as regulation of biobehavioral states and temperament. Simeonsson and colleagues
(1988) noted that the behavioral states of infants may range from sleep to active alert to
highly distressed and agitated. As infants’ central nervous systems develop and more
control of physiological states is possible, they may become more visually attentive and
able to use vision effectively.
As noted by Lueck, Chen, and Kekelis (1997), infant temperament influences the early
development of children. Temperament is biologically based but is amenable to
environmental influences via the goodness of fit between the child, the family, and the
environment. Temperament dimensions include activity level; willingness to approach new
objects, people, and events; adaptability; persistence/attention span; distractibility;
rhythmicity; mood; intensity; and sensory threshold. Children who are attentive and
approachable may be more likely to elicit experiences that will enhance visual function.
When the temperament of a child is suited to the home environment, there will be a
goodness of fit between child and family (Thomas & Chess, 1977).
Carrie is a fearless 12-month-old with septo-optic dysplasia and low vision who is happy
most of the time and loves interacting with her father and sister and exploring her
environment. When introduced to new people or new toys, Carrie is a bit hesitant, but after
a short period of time, she will initiate interactions with others and tactually and visually
explore new toys. If Carrie’s parents completed a temperament questionnaire, we might
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find that they rated her as being highly approachable, adaptable, and attentive. These
temperament characteristics are conducive to learning and make care giving relatively
easy.
Tommy, on the other hand, has the same diagnosis and is the same age, but is fussy and
very active, has little persistence, strongly resists new experiences, foods, and toys, and is
not very adaptable. These temperament characteristics make care giving for Tommy much
more challenging, and, therefore, may result in fewer opportunities for using his vision in a
variety of settings and activities.
With an understanding of the physiological, temperamental, and environmental factors that
might influence young children’s visual capacity and visual function, early interventionists
and families will be better equipped to plan and implement strategies that will facilitate the
child’s optimal use of vision.
References for Major Points
Adler, S. (n.d.). Perceptual development. Retrieved April 24, 2003 from York University,
Department of Psychology Web site:
http://www.psych.yorku.ca/adler/courses/2110/lectures/lecture_5.htm
Atchley, P. (1999). Contrast sensitivity (p. 3). Retrieved April 24, 2003 from University of
Kansas, Department of Psychology Web site:
http://www.psych.ukans.edu/psyc620/pdf/620C16.pdf
Atkinson, J. (2000). The developing visual brain. New York: Oxford University Press.
Bruer, J.T., & Greenough, W.T. (2001). The subtle science of how experience affects the
brain. In D.B. Bailey, J.T. Bruer, F.J. Symons, & J. W. Lichtman (Eds.), Critical
thinking about critical periods (pp. 209-232). Baltimore: Paul H. Brookes.
Chandna, A., & Noonan, C. (2000). Normal and abnormal visual development. In A. Moore
& S. Lightman (Eds.), Fundamentals of clinical ophthalmology: Paediatric
ophthalmology (pp. 38-52). London: BMJ Books.
Cook, C., Sulik, K.K., & Wright, K.W. (2003). Embryology. In K.W. Wright & P.H. Spiegel
(Eds.), Pediatric ophthalmology and stabismus (2nd ed., pp. 3-38). New York:
Springer.
Corn, A.L. (1983). Visual function: A theoretical model for individuals with low vision.
Journal of Visual Impairment & Blindness, 77(8), 373-377.
Visual Conditions Module 06/04/04
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S2 Major Points
Page 16 of 19
Early Intervention
Training Center
for Infants and Toddlers With
Visual Impairments
Corn, A.L. (1989). Instruction in the use of vision for children and adults with low vision.
RE:view, 21, 26-38.
Corn, A.L., DePriest, L.B., & Erin, J.N. (2000). Visual efficiency. In A.J. Koenig & M.C.
Holbrook (Eds.), Foundations of education: Instructional strategies for teaching
children and youths with visual impairments (Vol. 2, pp. 464-491). New York: AFB
Press.
Creger, P.J. (Ed.). (1989). Developmental interventions for preterm and high-risk infants:
Self-study modules for professionals. San Antonio, TX: Psychological Corporation.
Dobson, V. (1993). Visual acuity testing in infants: From laboratory to clinic. In K. Simons
(Ed.), Early visual development: Normal and abnormal (pp. 318-334). New York:
Oxford University Press.
Elston, J. (2000). Visual pathway disorders. In A. Moore & S. Lightman (Eds.),
Fundamentals of clinical ophthalmology: Paediatric ophthalmology (pp. 223-235).
London: BMJ Books.
Erin, J. & Paul, B. (1996). Functional vision assessment and instruction of children and
youths in academic programs. In A. Corn & A. Koenig (Eds.), Foundations of low
vision: Clinical and functional perspectives (pp. 185-220). New York: AFB Press.
Erin, J., Fazzi, D., Gordon, R., Isenberg, S. & Paysse, E. (2002). Vision focus:
Understanding medical and functional implications of vision loss. In R. Pogrund and
D. Fazzi (Eds.), Early focus: Working with young children who are blind or visually
impaired and their families (2nd ed., pp. 52-106). New York: AFB Press.
Eustis, H.S., & Guthrie, M.E. (2003). Postnatal development. In K.W. Wright & P.H.
Spiegel (Eds.), Pediatric ophthalmology and strabismus (2nd ed., pp. 39-53). New
York: Springer.
Fazzi, D., & Klein, M.D. (2002). Cognitive focus: Developing cognition, concepts, and
language. In R. Pogrund & D. Fazzi (Eds.), Early focus: Working with young
children who are blind or visually impaired and their families (2nd ed., pp.107-153).
New York: AFB Press.
Fox, D. (2003). Development of visual behaviors and skills. Chapel Hill, NC: Early
Intervention Training Center for Infants and Toddlers With Visual Impairments, FPG
Child Development Institute, UNC-CH.
Gelbert, S.S., Hoyt, C.S., Jastrebski, G., & Marg, E. (1982). Long-term visual results in
bilateral congenital cataracts. American Journal of Ophthalmology, 93, 615-621.
Visual Conditions Module 06/04/04
EIVI-FPG Child Development Institute
UNC-CH
S2 Major Points
Page 17 of 19
Early Intervention
Training Center
for Infants and Toddlers With
Visual Impairments
Glass, P. (2002). Development of visual system and implications for early intervention.
Infants & Young Children, 15(1), 1-10.
Hall, A., & Bailey, I. (1989). A model for training vision functioning. Journal of Visual
Impairment & Blindness, 83, 390-396.
Hertle, R.W., Schaffer, D., & Foster, J. (2002). Pediatric eye disease: Color atlas and
synopsis. New York: McGraw Hill.
Horton, J.C. (2001). Critical periods in the development of the visual system. In D.B.
Bailey, J.T. Bruer, F.J. Symons, & J. W. Lichtman (Eds.), Critical thinking about
critical periods (pp. 45-65). Baltimore: Paul H. Brookes.
Hyvärinen, L. (2000). Vision evaluation of infants and children. In B. Silverstone, M.A.
Lang, B.P. Rosenthal, & E.E. Faye (Eds.), The Lighthouse handbook on vision
impairment and vision rehabilitation (pp. 799-820). New York: Oxford University
Press.
Johnson, M.H. (1991). Cortical maturation and the development of visual attention in early
infancy. Journal of Cognitive Neuroscience, 2, 81-95.
Johnson, M.H. (1997). Developmental cognitive neuroscience: An introduction.
Cambridge, MA: Blackwell.
Lueck, A.H., Chen, D., & Kekelis, L.S. (1997). Developmental guidelines for infants with
visual impairments: A manual for early intervention. Louisville, KY: American
Printing House for the Blind.
Mohan, K.M. & Dobson, V. (2000). When does measured visual field extent become adultlike? It depends. Vision Science and Its Applications, 35, 2-17.
Rogers, G.L., Tishler, C.L., Tsou, B.H., Hertle, R.W., & Fellows, R.R. (1981). Visual
acuities in infants with congenital cataracts operated on prior to 6 months of age.
Archives in Ophthalmology, 99, 999-1003.
Ruff, H.A., & Rothbart, M.K. (1996). Attention in early development. New York: Oxford
University Press.
Shea, S.L., Fox, R., Aslin, R.N., & Dumais, S.T. (1980). Assessment of stereopsis in
human infants. Investigative Ophthalmology & Visual Science, 19, 1400-1404.
Simeonsson, R.J., Huntington, G.S., Short, R.J., & Ware, W.B. (1988). The Carolina
record of individual behavior (CRIB): Characteristics of handicapped infants and
Visual Conditions Module 06/04/04
EIVI-FPG Child Development Institute
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S2 Major Points
Page 18 of 19
Early Intervention
Training Center
for Infants and Toddlers With
Visual Impairments
children. Chapel Hill, NC: Frank Porter Graham Child Development Center,
University of North Carolina at Chapel Hill.
Tavernier, G. (1993). The improvement of vision by vision stimulation and training: A
review of the literature. Journal of Visual Impairment & Blindness, 87, 143-148.
Teller, D. (1997). First glances: The vision of infants. The Friedenwald lecture.
Investigative Ophthalmology & Visual Science, 38, 2183-2203.
Thomas, A., & Chess, S. (1977). Temperament and development. New York:
Brunner/Mazel.
Tychsen, L. (2001). Critical periods for development of visual acuity, depth perception, and
eye tracking. In D.B. Bailey, J.T. Bruer, F.J. Symons, & J.W. Lichtman (Eds.),
Critical thinking about critical periods (pp. 67-80). Baltimore: Paul H. Brookes.
Vistech Consultants. (1990). Teller acuity card handbook. Dayton, OH: Vistech
Consultants, Inc.
Warren, D.H., & Hatton, D.D. (2003). Cognitive development in visually impaired children.
In I. Rapin & S. Segalowitz (Eds.), Handbook of neuropsychology (2nd ed., pp. 439458). Amsterdam: Elsevier Science Publishers.
Wright, K.W. (2003a). Binocular vision and introduction to strabismus. In K.W. Wright &
P.H. Spiegel (Eds.), Pediatric ophthalmology and strabismus (2nd ed., pp. 144156). New York: Springer.
Wright, K.W. (2003b). Lens abnormalities. In K.W. Wright, & P.H. Spiegel (Eds.), Pediatric
ophthalmology and strabismus (2nd ed., pp. 450-480). New York: Springer.
Wright, K.W. (2003c). Visual development and amblyopia. In K.W. Wright, & P.H. Spiegel
(Eds.), Pediatric ophthalmology and strabismus (2nd ed., pp. 157-171). New York:
Springer.
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