Vision in a Child
In this section of the
website you will find information contained in the book "Caring
For Your Child With Hydranencephaly" Part 4: Resources in Caring
for Your Child.
In some instances I will
include the text as it appears in the book and in others will
just give you the link to where the information can be found.
Please note that none of the information in this section is my
own. It is taken from the websites mentioned at the top of each
Vision and it's development
are big areas in our children's lives.
Cortical Visual Impairment
This condition is very common in children with Hydranencephaly.
It means that although there is nothing wrong with the eyes
itself, the brain is unable to tell the eyes what they are
seeing. Children with CVI aren't totally blind. They see some
colors better than others, their vision may come and go, and
change from day to day. Personal experience: We were originally
told that Kayda had no optic nerve. Three years later that same
Dr became convinced that she could see. She now sees and often
clearly understands objects up to 4 ft away. Her vision does
vary from minute to minute. In all the information that I've
read on CVI the common thread seems to be that progress is
Cortical Visual Impairment
Cortical Visual Impairment (CVI) is a temporary or permanent visual
impairment caused by the disturbance of the posterior visual pathways
and / or the occipital lobes of the brain. The degree of vision
impairment can range from severe visual impairment to total blindness.
The degree of neurological damage and visual impairment depends upon the
time of onset, as well as the location and intensity of the insult.
It is a condition that indicates
that the visual systems of the brain do not consistently understand or
interpret what the eyes see.
The presence of CVI is not an
indicator of the child's cognitive ability.
The major causes of CVI are asphyxia, perinatal hypoxia ischemia
("hypoxia": a lack of sufficient oxygen in the body cells of blood;
"ischemia": not enough blood supply to the brain), developmental brain
defects, head injury, hydrocephalus, and infections of the central
nervous system, such as meningitis and encephalitis.
Initially, children with CVI appear blind. However, vision tends to
improve. Therefore, Cortical Visual Impairment is a more appropriate
term than Cortical Blindness. A great number of neurological disorders
can cause CVI, and CVI often coexists with ocular visual loss so both a
pediatric neurologist and a pediatric ophthalmologist should see the
The diagnosis of Cortical Visual
Impairment is a difficult diagnosis to make. It is diagnosed when a
child has poor or no visual response and yet has normal pupillary
reactions and a normal eye examination. The child's eye movements are
most often normal. The visual functioning will be variable.
The result of an MRI (Magnetic
Resonance Imaging) in combination with an evaluation of how the child is
functioning visually, provide the basis for diagnosis.
Behavioral / Visual
Children with CVI have different abilities and needs. The presence of
and type of additional handicaps vary. Some children have good language
skills and others do not. Spatial confusion is common in children with
CVI because of the closeness of the occipital and pariental lobes of the
brain. Habilitation should be carefully planned. A full evaluation by a
number of professionals is essential. The evaluation team could include:
teachers (of the visually impaired or severely handicapped), Physical
Therapists (PT's), Occupational Therapists (OT's), Speech Therapists,
and Orientation and Mobility Specialists.
Common characteristics of
visual function demonstrated by children with CVI:
- Vision appears to be variable:
sometimes on, sometimes off; changing minute by minute, day by day.
- Many children with CVI may be
able to use their peripheral vision more effectively than their
- One third of children with CVI
are photophobic, others are compulsive light gazers.
- Color vision is generally
preserved in children with CVI (color perception is represented
bilaterally in the brain, and is less susceptible to complete
- The vision of children with CVI
has been described much like looking through a piece of Swiss
- Children may exhibit poor depth
perception, influencing their ability to reach for a target.
- Vision may be better when
either the visual target or the child is moving.
The behaviors of children with
CVI reflect their adaptive response to the characteristics of their
- Children with CVI may
experience a 'crowding phenomenon" when looking at a picture:
difficulty differentiating between background and foreground visual
- Close viewing is common, to
magnify the object or to reduce crowding.
- Rapid horizontal head shaking
or eye pressing is not common among children with CVI.
- Over stimulation can result in
fading behavior by the child, or in short visual attention span.
- The ability of children with
CVI to navigate through cluttered environments without bumping into
anything could be attributed to "blindsight", a brain stem visual
- Children are often able to see
better when told what to look for ahead of time.
- Children with CVI may use their
peripheral vision when presented with a visual stimulus, appearing
as if they are looking away from the target.
- Some children look at an object
momentarily and turn away as they reach for it.
The following statements are not true, according to current knowledge in
- Children with CVI are visually
inattentive and poorly motivated. All children with CVI will have
- CVI is not a true visual
- Children with CVI are totally
- Children whose visual cortex is
damaged are Cortically Blind.
- A great deal of energy is
needed to process information visually. The child might tire easily
when called upon to use his visual sense. Allow for intermittent
- Positioning is important. Keep
the child comfortable when vision use is the goal in order that
"seeing" is the only task.
- Head support should be provided
during play or work sessions, to avoid involuntary shifting of the
- Try many different positions to
find the one in which the child feels most secure. Infants and
toddlers will demonstrate when and where they see best by their
- If the child needs to use a lot
of energy for fine motor tasks, work on fine motor and vision
separately, until integration of the modalities is possible.
- The simpler, more constant and
more predictable the visual information, the better the child with
CVI is likely to deal with it. Keep toys and environment simple and
- Use books with one clear
picture on a contrasting simple background.
- Use familiar/real objects
(bottle, bowl, plate, bath toy, diaper, cup, spoon, favorite toy)
one at a time. Familiarity and simplicity are very important.
- Since the color system is often
intact, use bright fluorescent colors like red, yellow, pink, and
orange. Colored mylar tissue seems to evoke visual responses.
- Repetition is very helpful: use
the same objects and same process each time to provide familiarity
and security for the child. Familiarity breeds response.
- Look for toys and activities
that motivate the child.
- Vision is often best stimulated
when paired with another sensory system. For example, auditory cues
from the handling of mylar may help attract the child's attention.
- Introduce new and old objects
via touch and verbal description.
- Try different lighting
situations to assess optimal conditions for viewing. Try locating a
light source behind, and/or to the side of the child.
- Try moving the target that you
want the child to see. Try different visual fields.
- Allow lots of time for the
child to see and to respond to what is being seen. Learn to
interpret each child's subtle response cues: such as changes in
breathing patterns, shifts of gaze or body position, etc.
a child with CVI needs to control his head, use his vision, and perform
fine motor tasks, the effort can be compared to a neurologically intact
adult learning to knit while walking a tightrope."
1."Observations on the Habilitation of Children with Cortical Visual
Impairment" Groenveld, M.; Jan, J.E.; Leader, P., Journal of Visual
Impairment and Blindness, January, 1990.
2. Visual Behaviors and
Adaptations Associated with Cortical and Ocular Impairment in Children,"
Jan, J.E.; Groenveld, M.; Journal of Visual Impairment and Blindness,
April 1993, American Foundation for the Blind.
3.Video: "Issues in Pediatric
Ophthalmology: Cortical Visual Impairment (1994)," Child Health and
Developmental Media, Inc., 5632 Van Nuys Blvd., Suite 286, Van Nuys, CA
4."Cortical Visual Impairment in
Children, " Good, W; Jan, J.E.; Luis, D. (1994) Survey of Ophthalmology.
Julie Bernas-Pierce, Editor
Janice Polizzi Home Counselors
Colette Altmann Dennak Murphy
Barb Lee Dr. William Good
Dr. Creig Hoyt Ann Silverrain
Off to a Good Start Program
Many of the children with
Hydranencephaly are also thought to have ONH.
Optic Nerve Hypoplasia
Optic Nerve Hypoplasia (ONH) refers to the underdevelopment of the optic
nerve during pregnancy. The dying back of optic nerve fibers as the
child develops in utero is a natural process, and ONH may be an
exaggeration of that process. ONH may occur infrequently in one eye
(unilateral) but more commonly in both eyes (bilateral). ONH is not
progressive, is not inherited, and cannot be cured. ONH is one of the
three most common causes of visual impairment in children.
In most cases there is no known cause of ONH. Infrequently ONH has been
associated with maternal diabetes, maternal alcohol abuse, maternal use
of anti-epileptic drugs, and young maternal age (20 years of age or
less), but these factors account for very few of the total number of
cases. All races and socio-economic groups seem to be affected by ONH.
- ONH may occur by itself or
along with neurological or hormonal abnormalities. Hormonal problems
not apparent in early life may appear later.
- Children with ONH demonstrate a
wide spectrum of visual function ranging from normal visual acuity
to no light perception. The effect on the visual field may range
from generalized loss of detailed vision in both central and
peripheral fields (depressed visual fields) to subtle peripheral
- A high percentage of children
with ONH have associated involuntary rhythmic movements of the eye (nystagmus).
In most cases, the nystagmus is associated with significant
bilateral reduced visual acuity.
- ONH is a stable condition.
Visual function does not deteriorate with time. A mild improvement
in visual function may occur as the result of maturation processes
of the brain. In some cases, reduced nystagmus may also occur.
- Depth perception may be more
severe if vision loss is great.
- Mild light sensitivity
(photophobia) may occur.
ONH is diagnosed by direct examination of the eye by an ophthalmologist.
No current laboratory or radiographic tests will establish the
diagnosis. Many infants who are diagnosed with Optic Nerve Atrophy are,
in fact, children with ONH. Sometimes visual functioning can be
predicted from the appearance of the optic discs. However, it is very
difficult to predict visual acuity on this basis alone.
Visual And Behavioral
- The child's vision is
characterized by a lack of detail (depressed field), but this lack
of detail is not comparable to the blurred reduction in vision when
a person removes her glasses.
- In certain cases of ONH a
specific field defect occurs. Children may not be aware of people or
objects in the periphery.
- Children with ONH may be unable
to locate objects in space precisely due to a lack of depth
- Some children with ONH have
mild photophobia. These children may squint, lower their head, avoid
light by turning away, or resist participating in outdoor
- When one eye is affected more
than the other, an ophthalmologist may recommend a trial of patching
the stronger eye, since the visual loss may be due to amblyopia.
- Some feeding issues are
associated with hormonal problems. Lack of interest in eating may be
due to absent or diminished sense of smell and taste. Children with
ONH may have very restricted food preferences. Some children exhibit
excessive lip smacking while eating.
- Behaviors of some children with
ONH may be due to associated medical conditions, such as
inattentiveness and irritability due to low blood sugar levels
- The child with associated
central nervous system problems may be easily distracted, quickly
frustrated and act in a disorganized or an impulsive way.
Conditions Associated With
Associated brain and hormonal abnormalities are common in children with
nystagmus and bilateral severe vision loss, and are less common in cases
where vision loss is mild or unilateral. Abnormalities include:
1. Midline anomalies of the
brain: septo optic dysplasia (absence of the septum pellucidum and the
corpus callosum), encephaloceles, anomalies of the ventricles,
anencephaly, cerebral atrophy, and rarely, tumors.
2. Hormonal insufficiencies:
thyroid, growth hormone, pituitary, adrenal, anti diuretic hormone
Associated midline brain anomalies can be identified by either an MRI or
CT scan. Hormonal insufficiencies require an examination by a specialist
in hormonal disorders (pediatric endocrinologist). Children particularly
at risk for having associated hormonal insufficiencies are those who had
neonatal low blood sugar (hypoglycemia), had prolonged jaundice
(hyperbilirubinemia), failed to grow normally (failure to thrive), have
difficulty regulating body temperature in connection with viral
illnesses, and/or had a CT or MRI scan showing an absence of tissue
connecting the brain to the pituitary gland (the pituitary stalk).
The following statements are NOT TRUE according to current research:
- ONH occurs in clusters due to
use of pesticides in the environment.
- The associated midline brain
anomalies have a profound effect on the visual outcome and/or
spatial orientation of these patients.
- All mothers of children with
ONH were drug users during pregnancy.
- Each child should receive
medical monitoring and comprehensive, ongoing, functional and
- Teachers need to increase the
size, contrast, and lighting of materials for a child who has
nystagmus and bilateral severe visual loss because of generally
- When a specific field loss is
identified, materials need to be presented within the child's visual
field. The child should be encouraged to turn his head to look for
people and objects outside his visual field.
- A child with ONH needs the
opportunity to develop learned aspects of depth perception through
fine and gross motor activities, including container play, nesting
and stacking, ball tossing and rolling, pouring activities, and lots
of practice with stairs, slides, foam wedges for crawling, and
cardboard box play.
- The effects of light
sensitivity can be minimized by adjusting lighting levels, wearing
tinted lenses, and minimizing glare on surfaces.
- A child with ONH often has
other conditions that need to be considered when developing an
individual education plan.
- A child who is easily
distracted, frustrated, disorganized, and impulsive may be helped by
predictable physical environments, dependable daily routines, and
- Slowing the pace of activities
and providing predictable transition routines may help reduce
resistant and irritable behavior.
- Offering frequent snacks to
children diagnosed with hypoglycemia may be helpful.
- When a child does have feeding
problems, parents and professionals need to agree on recommended
strategies to create a positive feeding experience.
- When a child has no functional
vision, an approach that uses all the senses for learning is needed.
- Evaluation by an instructor of
Orientation and Mobility is essential in meeting the child's needs,
due to loss of detail vision and vision field loss.
Borchert, M.S. An Inside Look At Optic Nerve Hypoplasia Research - A
Leading Cause of Infant Blindness, USC School of Medicine.
Hoyt, C. (1986). Optic Nerve
Hypoplasia: A Changing Perspective. Transactions of the New Orleans
Academy of Ophthalmology. Raven Press, New York.
Lambert, S. & Hoyt, C. (1987).
Optic Nerve Hypoplasia. Ophthalmology. 32, #1, July, August, 1-9.
Marsh-Tootle, W.L. (1994).
Congenital Optic Nerve Hypoplasia: A Symposium Paper. Optometry & Vision
Science. 71; #3, 174-180.
Tait, P. (1989). Optic Nerve
Hypoplasia: A Review of the Literature, Journal of Visual Impairment and
Blindness, April, 207-211.
Willnow, S. et al. (1996).
Endocrine disorders in septo-optic dysplasia (De Morsier
syndrome)-evaluation and follow up of 18 patients. European Journal of
Pediatrics, 155; 179-184.
Project Coordinators: Julie Bernas-Pierce, M.Ed. and Namita Jacob
Dr. Creig Hoyt, Nancy Akeson, Gail Calvello, Laila Adle,
Carole Osselaer, Patricia Silva,Laura Davis.
Reviewers: Kay Ferrell, Ph.D., Deborah Hatton, Ph.D., Kathryn Neale
The Pediatric Visual Diagnosis
Fact Sheets are sponsored by a grant from the Blind Children's Center
and with support from the Hilton/Perkins Program through a grant from
the Conrad Hilton Foundation of Reno, Nevada.
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Strictly Prohibited (1/98 Bbf)