Increase public awareness and understanding of Cerebral / Cortical Visual Impairment ( CVI ) or Brain Damage Related Visual Dysfunction ( BVD )
When it comes to cerebral visual impairment
(CVI), many people have the following questions:
1. I have never
heard of cerebral visual impairment. What is this?
2. Isn’t visual impairment caused by eye
problems? How come it is related to
the brain? How does the brain
affect what we see?
3. What
is so special about cerebral visual impairment (CVI)? What is the difference
between CVI and the common visual impairment?
4. What
is the relationship between CVI and me? Why
should I need to know about it?
Apart from using our eyes, we
are also using our brains to see!
In fact, we don't just use our eyes to see
because our brains in fact process the images that are perceived by our eyes.
As shown in the diagram, the visual pathway leads
from the optic nerves (on the left of the diagram) to the rear of the brain,
i.e. the visual cortex (on the right of the diagram), which is approximately
the part of our head that rests on the pillow.
Therefore, the visual images seen by the eye will
be transmitted from the front of the head to the back of the head.
In other words, the visual pathway needs to pass
through many parts of the brain and is connected with other areas of brain
functions, e.g. motor, memory, and language, etc.
So if any parts of the brain that involve in the
transmission of visual signals are damaged, the images that the person
perceives would be different from people with normal vision! If visual
assessment reveals that vision or visual field is impaired to the degree of
visual impairment, this would be defined as cerebral visual impairment (CVI).
It was formerly called cortical blindness, which is not a very appropriate term,
because the degree of visual impairment may not reach total blindness or the degree implied by the word ‘blind’ and the
damage may not merely occur in the visual cortex but rather in other parts of
the brain as well.
Of course, the degree of visual loss in some
people is less severe and has not reached the degree of visual impairment, yet
their visual function and performance are also affected. A newer collective
term ‘brain damage related visual dysfunction (BVD) is used to describe such
conditions.
As for how brain damages affect a person’s
vision, it depends on the part(s) of the brain that is/are damaged. Of course,
detailed brain examinations, e.g. MRI will help doctors’ diagnoses, but to what
extent is the performance of visual functioning affected by the brain
damage(s), it’s a combination of various factors, e.g. detailed assessment by
optometrists, patient’s expression ability, behavioral observations, etc.
Refer to the following article: http://www.lea-test.fi/files/NewConcepts_and_Names.pdf
Definition, causes, and
trend:
Cerebral visual impairment (CVI), which has been classified under NVI
(Neurological visual impairment) and also under the collective terminology BVD
(Brain-damage related visual dysfunction) in recent years, has become the main
cause of visual impairment in children in advanced medical areas such as the
United States!
In Hong Kong, there are also varying degrees of
NVI or BVD caused by brain damage
among children with severe intellectual disabilities and physical disabilities.
Why is it so, even in advanced countries with
advanced medical services?
Why
is the number of NVI / BVD / CVI cases increasing?
The causes of NVI / BVD / CVI are: congenital brain
impairments, cerebral palsy, lack of oxygen during delivery, and accidents,
e.g. home accidents, traffic accidents, sports injuries, etc., which result in
brain hemorrhage, hydrocephalus, etc., which damage brain cells and thus affect
the brain's visual functions.
In recent years, encephalitis, which sometimes
appears in the news, is also one of the causes of brain damage especially in babies
and young children, as it could cause severe damages to brain functions.
Therefore, parents should not overlook flu or
fever conditions among children, because severe cases can cause meningitis,
acute encephalitis, seizures / epilepsy (which may lead to hypoxia and
subsequent brain damages).
Adults and the elderly may also suffer from brain
damages. The most common causes are stroke, brain tumor, accidental brain
damage, etc.
There are even cases of temporary blindness,
(e.g. because of brain hemorrhage), or
the inability to identify relatives, but after a period of time, the patient
could gradually recover his/her vision (when
the hemorrhage effects have subsided) or recognize people. This recovery of
vision sounds just like a plot in TV series.
As for elderly patients
with dementia / cognitive impairment, they may also exhibit visual performance
characteristics which are similar to CVI characteristics, because they have
problems in the processing (analyze / discriminate / identify) and memory of visual
information, e.g. difficulties in dealing with complex or unfamiliar visual
environments, and mainly pay attention to images at a near distance rather than
distant images, delay in responses, etc.
In recent years, there is an increase in the
number of students with autism or SpLD in reading and writing. In fact, they
also exhibit various difficulties in visual functioning such as the reception,
processing, and differentiation of visual information, e.g.:
-
some SpLD
students are over sensitive to glare on glossy paper or highly whitish paper
which would affect their comfort in reading or writing;
-
children
with autism are difficult to discriminate or identify the faces of different
people; or they are easily attracted by moving objects (e.g. they like to stare
at rotating fans / light sources / rotating wheels); or they have difficulty in figure-ground
discrimination in a complex picture / scene, or difficult to adapt to an
unfamiliar environment.
These behaviors are similar to some of the CVI
characteristics (refer to the list below).
At the Vision 2005 Low Vision International
Conference, foreign experts have reported that some children with NVI /BVD have
even been misunderstood as autism!
Many people assume that CVI casess only exist
in special schools or among the severely handicapped. But in
fact CVI / NVI/ BVD are not limited to people with intellectual disability or
severe disabilities.
There has been a real case of CVI in a child
with normal intelligence but who was found by parents to be unable to identify
his family members by their appearances. He also exhibited difficulties in
understanding pictures in textbooks and therefore required special education
and training in a school for the visually impaired. As for cases with physical
disabilities, such as cerebral palsy, they may exhibit BVD because of damages
in the brain.
Therefore, the author of this blog hopes to make
use of this blog and the Facebook Page called ‘CVI’ to increase public
understanding of the effects of brain damage on visual functioning and know how
to take care of cases with CVI.
Refer to the link
of the Facebook Page:
Characteristics of CVI:
People with cerebral visual impairment have the
following characteristics in their visual performance and behavior. However,
different people have different characteristics and the degree of each type of
characteristics also varies among different people.
Some cases’ CVI conditions are minor, with only a
few features; some cases are more severe and have quite a number of the
following characteristics (base on information from the website of APH, i.e.
American Printing House for the Visually Impaired.):
1. Eye examination results are generally normal, or
there is no abnormal situation, which means that vision problem is not caused
by eye disease.
2. Difficulty in understanding unfamiliar visual
environment. Better performance in more familiar visual environment.
3. Pay attention to things at close distance, not
aware of, or pay no attention to things in the distance.
4. Difficulty in understanding complex visual
environment or objects crowded together.
5. Gazing at objects or light sources without
purpose or unconsciously, such as a ceiling light and the window (i.e. brightly
lit places).
6.
Obviously like to look at objects of certain colors, have color preferences,
e.g. bright colors such as red and yellow
(see the explanation below).
7. Defect in visual field: there is a certain part
of the visual field which cannot see things.
8. Response is delayed (visual latency) and slower
than average.
9. Being attracted by people or objects in motion,
especially when objects or images move quickly, including movement-like light
reflections from objects, e.g. a person passing by, a fan rotating, reflective
shinny objects in gold and silver.
10. Lack of visual reflexive responses, or visual
reflex is different from the average person, i.e. if something, like a finger,
suddenly touches the center of the nose, the client does not automatically
blink his/her eyes as a visual reflex reaction.
11.Eye-hand coordination or visual-motor performance
is different from that of the average person, i.e. the CVI client is not
looking at the object that his/her hands are touching. Instead, the CVI client
separates the two actions of looking and touching: look at it first, then eyes
moving away from the object while reaching out at the object with his/her
hands.
12.Visual performance is low and unstable, i.e.
visual reaction and performance are weak and unstable.
Suggestions on how to help
CVI clients:
1.
More comprehensive and
detailed assessments on visual functioning of CVI clients:
Besides general ophthalmic
and optometric examinations, such as eye problems and wearing appropriate
spectacles, the client should receive more comprehensive and detailed
assessments on his/her visual functioning so as to understand the areas in
which his/her performance is weak or have problems.
For example, whether there is a visual field deficit and which
part of the visual field is affected, or whether the client is over-sensitive
to light, color discrimination ability, figure-ground discrimination, etc.
It was reported that in the United States, stroke patients would
receive assessment on visual functioning as soon as possible, especially on
visual field and his/her speed in visual tracking of moving objects as these
would affect the patients’ safety in mobility.
2. Familiar with the environment and people:
Reduce short-term changes, such as the setting at home, the
location and storage of personal items.
3. Proximity:
Try to put objects near the patient, or bring the patient to look
at it more closely instead of pointing to the distance and ask him to look at
it.
4. Reduce visual complexity / complexity of the visual setting:
For example, reduce the complexity of objects placed on the table;
use tablecloth with a single color instead of tablecloth with patterns or in
many colors.
5. Wait patiently for the patient to respond:
Should not hurry the patient. Reminders that ask the patient to
hurry up may also interfere with his/her visual usage, so wait for the patient
to think and respond slowly after giving instructions. Instructions should also
be simplified.
6. Create and make use of motion to raise visual awareness:
Shake the object, or the person moves from left to right, in front
of the client so as to draw his/her attention.
7. If the client often looks at light sources non-purposefully,
such as windows and sunlight, staring at the ceiling light while lying on the
bed, it may be necessary to cover the window with curtains, wear a hat during
outdoor activities, or turn off the ceiling lights during sleep, etc.
8. Usage of color to increase contrast and visual awareness:
In daily life, the yellow and red colors are
commonly used in public facilities to enhance contrast and visual sensitivity,
such as handrails and staircase fringes on buses or mass transit railway
cabins.
CVI clients
are somewhat similar to babies in the sense that they are more sensitive to
bright colors such as yellow and red, as well as fluorescent colors, as their
brain functioning may still preserve a higher sensitivity of these bright
colors even though they have brain damages.
Of course, using a dark color to contrast with a
light color and the usage of bright colors are also helpful to the elderly and
the visually impaired besides CVI clients who suffer from visual dysfunction
due to brain damages.
In choosing the appropriate color combinations to
increase contrast, the combination of black and yellow can help to make the
yellow parts more obvious, thus the effect is better than other color
combinations. Refer to the following example:
Colors that suit the CVI client’s preferences or
individual needs could also be used in household items, e.g. as object markers
or the colors for personal items. Dark and light color combinations as well as
bright colors could be used to increase contrast and awareness, e.g.:
-
red / yellow
towel / toothbrush / cup and plate;
-
dark and
simple background tablecloth or tray without patterns, with yellow / white /
silver tableware placed on the tablecloth or
tray (red and orange tableware
are hard to find, otherwise you can also have a try.).;
Conclusion
Brain damage leads to abnormal performance of
visual functioning in CVI cases. There are many variations in the
characteristics, abilities, and performance among patients. Therefore, it is
difficult to sum up or make simple judgment.
The above information is for reference only,
aiming at increasing public concern and awareness.
Moreover, not only should severe cases be paid
attention to, for there are some clients whose degree of visual impairment has
not yet reached low vision or visual impairment, but they also exhibit abnormal
situations in their visual functioning, vision usage and daily life performance,
which also affect their daily living.
The correct treatment should be a more
comprehensive assessment for the CVI client, which is conducted by
professionals like the neurologist, ophthalmologist, optometrist, and
occupational therapist, etc. and recommendations should be made base on
individual needs, cognitive abilities, and home setting of the CVI client.
Remarks:
1. This
blog has another article explaining the learning characteristics, training
methods, teaching strategies, and general guidelines in taking care of CVI
children with multiple disabilities:
“Methods to enhance the learning of CVI
(cerebral/cortical visual impairment) children with multiple disabilities”
2. Some articles in Taiwan have different Chinese
translation for ‘cerebral visual impairment’.
3. In Hong Kong, there are also different
versions for the Chinese translation for CVI.
References
1. Educational perspectives on visual impairment
and visual dysfunction due to brain damage in children. (A powerpoint presented
by Dr. Amanda Hall Lueck in January 2009, Hong Kong.)
2. Understanding the behaviours of children with
CVI. (A position paper by Dr. Lea Hyvarinen for the SKI-HI Institute Webcasts,
March and April, 2004.)
3. An international classification of
neurological visual disorders in children. (James E. Jan, William V. Good,
Creig S. Hoyt.)
4. Neurological visual impairment. (Fact sheet
#022, California Deaf-blind Services.)
5. The effects of brain damage on visual
functioning in children. (P.K. Alexander, Journal of visual impairment &
blindness, 1990.)
6. What is CVI? (APH.ORG)
7. The importance of timely diagnosis of cerebral
visual impairment in children for critical and early visual intervention.
(Kathleen Appleby)
8. Autism and visual impairment. (Terese
Pawletco, 2002.)
