Cortical Visual
Impairment
Visual Diagnosis Fact Sheet by the Blind Babies Foundation,
San Fransico, CA
DEFINITION:
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 eyes
see.
This is not an indicator of cognitive ability.
CAUSE:
The major causes of CVI are asphyxia, prenatal hypoxia
ischemia (“hypoxia”: a lack of sufficient oxygen in
the body cells or 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.
CHARACTERISTICS:
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 the child should be seen by both
a pediatric neurologist, and a pediatric ophthalmologist.
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 combination of the MRI and how the child
is functioning visually, provides the basis for diagnosis.
BEHAVIORAL/VISUAL CHARACTERISTICS:
Children with CVI have different abilities and needs. The
presence and type of additional handicaps vary: some children have
good language skills and others do not, and spatial confusion is
common because of the anatomical proximity of the parietal and occipital
lobes.
Habilitation should be carefully planned.
A full evaluation by a number of professional is essential. The
evaluation team could include: teachers (of the visually impaired
or severely handicapped), PT’s, OT’s, Speech Therapists,
and Orientation and Mobility Specialists.
There are several common characteristics of visual
function demonstrated by children with CVI:
- Vision is variable: sometimes on, sometimes off;
changing minute by minute, day by day.
- Rapid horizontal head shaking or eye pressing is
uncommon among children with CVI.
- One third of children with CVI are photophobic.
- Others may be 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 elimination).
- The vision of children with CVI has been described
much like looking through a piece of Swiss cheese.
- 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.
- Many children with CVI may be able to use their
peripheral vision more effectively than their central vision.
The behaviors of children with CVI reflect their
adaptive response to the characteristics of their condition:
- Children with CVI may experience a “crowding
phenomenon” when looking at a picture: difficulty differentiating
between background and foreground visual information.
- Close viewing is common, used to magnify the object
or to reduce crowding.
- Overstimulation can result in “fading”
behavior by the child, or in a 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
system.
- 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.
MYTHS:
The following are some of the many myths associated
with CVI:
- Children with CVI are visually inattentive and
poorly motivated.
- All children with CVI will have cognitive deficits.
- CVI is not a true visual impairment.
- Children with CVI are totally blind.
- Children whose visual cortex is damaged are Cortically
Blind.
TEACHING STRATEGIES:
- 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 “break”
times.
- 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 visual field.
- 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 adaptive behaviors.
- 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.
- When 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.
- The simpler, more constant and more predictable
the visual information, the better the child with CVI is likely
to deal with it. Keep toys an environment simple and uncluttered. 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 cue 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.
RESOURCES:
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.; 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 91401
4. “Cortical Visual Impairment in Children,”
Good, W; Jan, J.E.; Luis, D. (1994) Survey of Ophthalmology. 38:4:351-364
ACKNOWLEDGMENTS:
Janice Polizzi Off to a Good Start Program
Collette Altman Home Counselors
Barb Lee Dennak Murphy
Julie Bernas-Pierce Dr. William Good
Dr. Creig Hoyt Ann SilverrainTACK TILES
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