What is CVI?
Ocular disorders: pathology of the eye(s)
Neurological visual disorders: disturbed or reduced vision due to various brain abnormalities.
The two types of visual disorders (ocular & neurological) can coexist.
Cortical visual impairment (CVI) is a neurological visual disorder. It is the fastest growing visual impairment diagnosis today.
Definition for Medical Purposes:
Cortical visual impairment (CVI) may be defined as bilaterally diminished visual acuity caused by damage to the occipital lobes and or to the geniculostriate visual pathway. CVI is almost invariably associated with an inefficient, disturbed visual sense because of the widespread brain disturbance. See brain diagrams.
Cortical visual impairment (CVI) may be defined as bilaterally diminished visual acuity caused by damage to the occipital lobes and or to the geniculostriate visual pathway. CVI is almost invariably associated with an inefficient, disturbed visual sense because of the widespread brain disturbance. See brain diagrams.
Definition for Educational Purposes:
Cortical visual impairment (CVI) is a neurological disorder, which results in unique visual responses to people, educational materials, and to the environment. When students with these visual/behavioral characteristics are shown to have loss of acuity or judged by their performance to be visually impaired, they are considered to have CVI.
Cortical visual impairment (CVI) is a neurological disorder, which results in unique visual responses to people, educational materials, and to the environment. When students with these visual/behavioral characteristics are shown to have loss of acuity or judged by their performance to be visually impaired, they are considered to have CVI.
Note: A student whose visual functioning is reduced by a brain injury
or dysfunction may be considered blind for educational purposes if
visual function is equal to or less than the legal definition of ocular
blindness. See Federal Quota.
History
Visual impairment was defined in the past by loss of acuity (how far
we see) and also by the severity of visual field loss (blind area).
This definition was originally designed for characterizing visually
impaired adults who required social assistance and not for children with
visual impairment caused by various eye conditions. Even though it
did not accurately represent visual abilities, the definition was widely
accepted, but it adversely influenced our thinking about visual
impairment. Services were developed worldwide for only those people
with visual problems fitting this definition while others with obvious
visual difficulties who required intervention were excluded.
During the last several decades, our understanding of vision has
markedly improved. It is now realized that vision is not a single sense
but a combination of complex senses which have evolved over millions of
years. Almost the entire brain is involved in the process of seeing.
In different locations there are specialized areas for distance vision,
recognition of faces, objects, colors, contrast, and movement. There
are also areas of the brain that coordinate visually-directed movements,
and process visual information to achieve perceptions of directionality
and depth. CVI is caused by widespread damage to the brain, which
affects most of the specialized visual centers, resulting in a damaged,
inefficient visual sense. When only a small visual area is affected, it
can result in a specific visual disorder, but not in CVI.
Because in the past everyone who was considered to be visually
impaired had to have reduced or absent visual acuity, the medical
definition of CVI also emphasized loss of ability to see in the distance
(reduced acuity). It was hoped that once the correct diagnosis was
made, children with CVI would be appropriately managed by a variety of
professionals, including educators.
The medical definition of CVI is not well understood by non-medical
professionals. While acuity testing is difficult in the young and
disabled for physicians, it is even more difficult for teachers. Also,
there are many children with visual problems similar to CVI, except they
have normal acuity. This visual condition is called "cortical visual
dysfunction" (CVD). The educational management of children with CVI and
CVD is similar. It is now known that with time the visual acuity of
children with CVI tends to improve. Therefore the diagnosis of CVI
could change to CVD over time. Both groups require remedial education,
which necessitates an increased number of specialized teachers. Based
on the above discussion, it is clear that there is a need for an
educational definition of CVI and CVD, which addresses the needs of
these children.
CVI is suspected by:
- a normal or close to normal eye examination;
- a medical history which includes neurological problems; and
- the presence of unique visual/behavioral characteristics.
Four major causes of CVI:
- Asphyxia
- Brain maldevelopment
- Head injury
- Infection
Unique visual/behavioral characteristics of CVI:
- Normal or minimally abnormal eye exam (CVI may co-exist with optic nerve atrophy, hypoplasia or dysplasia and ROP.)
- Difficulty with visual novelty (The individual prefers to look at old objects, not new, and lacks visual curiosity.)
- Visually attends in near space only
- Difficulties with visual complexity/crowding (Individual performs best when one sensory input is presented at a time, when the surrounding environment lacks clutter, and the object being presented is simple.)
- Non-purposeful gaze/light gazing behaviors
- Distinct color preference (Preferences are predominantly red and yellow, but could be any color.)
- Visual field deficits (It is not so much the severity of the field loss, but where the field loss is located.)
- Visual latency (The individual's visual responses are slow, often delayed.)
- Attraction to movement, especially rapid movements.
- Absent or atypical visual reflexive responses (The individual fails to blink at threatening motions.)
- Atypical visual motor behaviors (Look and touch occur as separate functions, e.g., child looks, turns head away from item, then reaches for it.)
- Inefficient, highly variable visual sense
Intervention Strategies
Interventions selected for students with CVI will be most effective
if they are the result of careful assessment of functional vision.
Interventions strategies selected should be based on the unique visual
and behavioral characteristics associated with CVI (Jan & Groenveld,
1993). These characteristics include: color preference, visual field
preferences, difficulties with visual novelty, attraction to movement,
difficulties with visual complexity, non-purposeful gaze, attraction to
light, visual latency, difficulties with distance viewing, and the
inability to coordinate the visual motor action of looking while
reaching (Jan & Groenveld,1993, Roman, 2004). The activities and
adaptations ought to be designed to embrace any of the CVI
characteristics that are interfering with the student's ability to use
vision purposefully. The following suggestions highlight some guiding
principles for the family and educational team in planning interventions
for students who have CVI.
Resources
A website dedicated to helping parents of young children with visual impairments as well as children with multiple disabilities.
Little Bear Sees is a website focused on helping visually impaired children learn to see.
Understanding your child
Visual Characteristics of Infants with CVI
Infants with cortical visual impairment demonstrate different visual
characteristics than infants with ocular, visual impairment. The eyes of
an infant with CVI usually look normal, although they will often not be
able to visually track an object. Their visual attention span can be
very short, and they may appear to look at the object peripherally.
Sometimes they are observed to briefly look, look away, and then return
again for another brief look. If they reach for an object, they may not
look at the object while trying to reach, but rather look at the object,
look away, and then attempt to reach. Some of the infants keep their
eyes half-closed or closed completely for periods of time. They may
compulsively light gaze, a characteristic not associated with infants
with just an ocular impairment. When they move around, they may get very
close to objects, not for magnification, but rather to "block out"
background visual information. Infants with CVI do not usually have
problems with the perception of color and are often attracted to the
primary colors, especially reds and yellows.
Many of the visual characteristics presented above are related to the
difficulty with visually processing the information in the environment.
Vision is the most important sense in humans. It is critical for
survival, orientation and navigation, anticipation, adaption, non-verbal
communication, and integration of information from all of the other
senses. As a result, we live in a very visually enriched and stimulating
environment. Often this environ-ment is too overwhelming for infants
and children with CVI. They are unable to process and interpret all that
they see. The overstimulating visual environment appears to cause them
to visually "disengage" or shut down the environment. They do this by
looking away, closing their eyes, or sometimes sleeping. At times this
visual input, especially when it is also combined with noise or other
sensory input can cause the infant to become so disorganized that it
results in agitation and crying. This is referred to as infant
behavioral state.
The Importance of Understanding Behavioral States
The ability of the infant to orient and attend to the environment is
primary in learning. The term "behavior state" refers to the infant's
ability to adapt to the sensory demands of the world and to be able to
attend for the purpose of learning. Behavioral state is affected by a
variety of both intrinsic and extrinsic factors. Examples of intrinsic
factors are effects of medication, nutritional status, and seizure
activity. Examples of extrinsic factors include: visual input, noise,
and touch. Although there may be times when intrinsic factors cannot
always be controlled, we as early interventionists need to be aware of
the extrinsic factors and their effect on the behavioral state of the
infant. When the infant is giving cues that indicate either a lack of
alertness and responsiveness, avoidance or aversion, it is important to
realize that the infant is not making an adaptive response to a stimulus
and is not learning from the environment. In addition, the infant is
communicating to us that whatever we are doing may be "too much" and we
need to reduce the amount of sensory input such as talking, music,
visual stimulation, and/or touch experiences that we are providing.
Consider Vision When Adapting the Environment
The majority of infants with the diagnosis of CVI have other central
nervous system involvement and their ability to regulate their
behavioral state and team from the environment can be affected. Since
vision is such a critical factor in learning for humans, it is important
to consider the visual environment when planning intervention programs.
As stated earlier, normal visual environments can be too enriched and
too complicated for infants and children with CVI. This may result in
the child visually disengaging and not using vision for learning.
Evaluating responses to visual input and how it affects the behavioral
state of the infant can be helpful. Parents are usually the best sources
of information about how sensory stimuli affect the behavior of their
infant. Parents often report that their infant is totally visually
unresponsive to the environment or only looks at certain times.
Sometimes they report that certain visual input will agitate or upset
the infant. They may provide information about certain colors or toys
that influence visual attention. It is also helpful to see whether the
infant responds to certain light and/or patterns.
Strategies
Modifying the visual environment to regulate the infant's behavioral
state and to promote visual orientation and attention to the world is an
important part of assisting that child -to initiate movement for the
purpose of play and learning. When the infant begins to experience some
control over the environment, this helps to also regulate behavioral
state since something is not always happening to the child, but rather
the child is controlling what occurs. Typical intervention strategies
for infants and children with visual impairment concentrate on enriching
the visual environment so that the infant is more aware of visual
items. Although this is good for infants and children with an ocular or
eye impairment, it is often detrimental for an infant or child with a
cortical visual impairment. Because infants with this diagnosis tend to
visually disengage with an enriched environment, it is more helpful to
simplify the visual environment. Examples of visual
simplification include: use a solid color blanket or sheet when playing
with infant or child and introduce one simple visually contrasting
object or toy at a time; using a background shield when introducing a
contrasting object or toy to reduce the effects of figure-ground;
removing extra visual stimuli from the infant's room and crib and using
one or two high contrast items to assist the infant to focus attention;
provision of a tactile cue to the hand when the infant appears to be
visually attentive; using a primary-colored bottle during feeding to
reinforce visual discrimination of a common object; and using common
objects that have meaning in the infant and child's life. Simple primary
colored cause and effect toys that have a light and sound can be
reinforcing in promoting reaching.
It is important to note that if an infant or child is diagnosed with
cortical visual impairment and a motor impairment, you may not be able
to work on visual engagement if you are working towards motor responses
such as head or trunk control. When the infant is fighting gravity, it
is very difficult to control visual muscles and attend to a visual
stimulus; it is likely that the infant will visually disengage and not
respond. When you are working on visual goals, it is helpful to
eliminate the effects of gravity and have the infant well positioned.
Being aware of the infant's behavioral state in response to sensory
stimuli in the environment and adapting the visual environ-ment for
infants with CVI can be two important factors in promoting attention and
response in these infants. Working with parents to collaborate on
strategies to simplify visual home environments and learning to read
behavioral cues in infants with multiple disabilities can promote
partnerships that assist the infant to begin self-directed movement for
play.
Linda Baker Nobles is an assistant professor of occupational
therapy at Rockhurst College in Kansas City, Missouri, where she teaches
both occupational therapy and physical therapy students. She has over
20 years experience working with infants and children with visual
impairments and a variety of other disabilities.
Resources on CVI
Video: Cortical Visual Impairment #11407, 54 minutes. Lecture by Dr.
Good, Pediatric Ophthalmologist in California. Available for $65 from
Child Health and Development Education Media, 5632 Van Nuys Boulevard,
Suite 286, Van Nuys, CA 91401, (818) 994-0933 (Voice), (818) 994-0153
(Fax)
Booklets: (1) Monograph on CVI for $12 from North Rocks Press, Royal
New South Wales Institute for Deaf and Blind Children, 361-365 North
Rocks Road, North Rocks, NSW 2151 Australia; (2) CVI in Children: A
Handbook for Parents and Professionals for $15 from Royal Blind Society
of N.S.W., 4 Mitchell Street, Enfield, NSW 2136 Australia.
References
Baker-Nobles, L., & Rutherford, A. (1995). Understanding cortical visual impairment in children, American Journal of Occupational Therapy, 49(9), 899-903.
Good, W. V., Jan, J. E., DeSa, L.. Barkovich, A. J., Groenveld. M.,
& Hoyt, C. S. (1994). Cortical visual impairment in children, Survey of Opthalmology. 38(4), 351-361.
Groenveld, M., Jan, J. E., & Leader, P. (1990, January).
Observations on the habilitation of children with cortical visual
impairment, Journal of Visual Impairment and Blindness, 11-15.
Guess, D., Rues, J., Roberts, S., Siegel-Causey, E., Ault, M., Guy,
B., & Thompson, B. (1993). Analysis of behavior state conditions
and associated environmental variables among students with profound
handicaps, American Journal of Mental Retardation. 97(6), 634-653.
Jan, J. E., & Groenveld, M. (1993, April). Visual behaviors and adaptations associated with cortical and ocular impairment. Journal of Visual Impairment and Blindness, 101-105.
