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 (with Chinese and English articles):
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.)
9.http://www.lea-test.fi/files/NewConcepts_and_Names.pdf
