Cortical Visual Impairment: Causes and Manifestations.
by Lilli Nielsen, Refsnaesskolen, Kalundborg, Denmark.
(This article was published in "Refsnaes-Nyt", No 38, September 1993).
What do we actually know about cortical visual impairment? What we know for sure is that we only know very little. We have, however, so many children with cortical visual impairment CVI) that it is considered appropriate to try to collect the knowledge that is available.
This article is based partly on the assessment by
means of language nor are they able to match identical figures, the
assessment must necessarily be based on the child's visual reactions
to black or grey stripes of various breadth or to various large or small
objects (preferential looking). However, the fact that the child reacts
visually only indicates that he has seen something, it does not indicate
whether he saw the whole object or the entire area of stripes. Even
if the child is able to visually follow an object moved in front of
him it is still impossible to tell whether the child saw that whole
object or whether he was able to see details of that
During the past 10 years it has become common to decorate the room or playroom of a child with vision impairment with wallpaper with black and white stripes or with patchwork tapestries made of pieces of fabric with black dots on a white background, or black horizontal, vertical and diagonal stripes on white background. Sometimes even the baby bottle has been covered with a woollen bag knitted in black and white stripes. Or the child has been provided with pictures showing black and white circles, squares and triangles on a black and white background. In some schools and institutions a special room has even been set up for vision training. Here the child with vision impairment is bombarded with sophisticated visual stimulation which is all based on the materials used to test whether a child can see or not.
Firstly, such a bombardment of visual information seems to be so overwhelming that the child refuses to look at it. Secondly, it can later be difficult to reassess the child's ability to see because the child either refuses to look at the test materials or because the test materials have become so familiar to the child that they no longer challenges him visually. Thirdly, it seems meaningless to provide the child with environments that he will never meet outside the vision training room.
One of the conditions that is characteristic of a child with multiple disabilities is that he has difficulty in generalizing what he learns in one setting to other settings, or in generalizing what he has learned during interaction with one person to his interaction with another person. So it will make the generalization of visual function unnecessarily difficult for the child if his environment for playing and learning is equipped in ways that he will never experience in places other than the learning environment.
Articles concerning cortical visual impairment (Groenveld et.al. 1990, Morse 1990, Steendam 1989), and partly on my own observations and those of colleagues regarding the visual function of children with cortical visual impairment. The diagnosis "cortical visual impairment" (CVI) means that those parts of the brain that receive and interpret the visual information from the eye and the optic nerve do not function normally.
The manifestation of this malfunction is that the child is either totally unable to see or is partially sighted in some way. Some children with CVI also have optic nerve atrophy or have a poorly developed optic nerve. Of course the child with CVI may also have a retinal or an occular disorder. As they grow quite a number of children with CVI develop some visual ability. But this ability most often manifests itself in such a way that children with CVI clearly differ from children with visual disabilities that are caused only by an occular disorder or disorder in the optic nerve or the retina.
Firstly, during the first years of life many children with CVI are either totally blind or have only light perception. Eventually, some do seem to see more and more, but they will probably never see normally. This course is sometimes described as delayed or slow development of the ability to see.
Secondly, the enhanced ability to see does not always function; from day to day or from hour to hour the child may fluctuate between functioning as totally blind and being able to see more or less.
Morse (1991) explains this by suggesting that the lateral geniculate body (the visual relay center of the brain) located in the thalamus may have a poor capacity. The thalamus is an organ located deep in the brain that distributes sensory messages to the various cortical centres. If the lateral geniculate body has this poor capacity it easily becomes overloaded and may then supress visual messages. This is probably true for some children with CVI. In other children with CVI, especially those who don't seem to have a problem with auditory or tactile messages, it would seem that the problem lies elsewhere than within the functioning capacity of the thalamus. It may be instead that the vision center in the cortex has a poor capacity for interpreting messages that are being sent from the lateral geniculate body in the thalamus.
While working daily with the child with CVI it may seem purely academic whether the child's fluctuating ability to see is caused by poor capacity of the thalamus, by lateral geniculate body, or by the visual center in the cortex. However, since the ability to integrate information from several sensory modalities is of great importance for learning to understand what has been seen, it becomes essential to try to verify whether it is the lateral geniculate body in the thalamus or the cortical centre for vision that has a poor capacity. If it is the lateral geniculate body in the thalamus that has poor capacity then the child will probably have specific difficulty in combining various sensory experiences because it must be expected that the thalamus from time to time also becomes overloaded from kinaesthetic, auditory and tactile information, making it more difficult for the child to learn to integrate the sensory information he is receiving. If it is the visual center that has a poor capacity, the child should have a better chance of adding visual information to the combination of kinaesthetic, auditory and tactile experiences that he may already have established. If this is the case it is easier for the child to learn to understand what he is looking at. The earlier the process of learning to see commences the easier it will probably be for the child to consider visual information useful. Relatively older children may have learned to get along with the combination of auditory, tactile and kinaesthetic information well enough that they have difficulty in relying on the visual information that they are slowly beginning to receive from time to time.
Based on my 25 years of work with children with CVI, I suggest that the reason why some children suddenly commence to see something at the age of 7 or 10 years is that their opportunity to learn has been enhanced by means of activities and games based on auditory, tactile and olfactory experiences. The "bombardment" of sensory information that the cortex is exposed to from these sources has probably had the effect that the visual center has begun to react, making it possible for the child to combine information from the visual and kinaesthetic sensory modalities, and so be able to look in a certain direction or to react in some of the ways that we usually interpret as a child having seen something.
Maybe early diagnosis followed by early intervention would cause an early commencement of the development of the ability to see.
Those children with CVI who have additional visual diagnoses have, of course, more difficulty in learning to see and a poorer possibility of learning to understand what they see than the children with "only" the diagnosis of cortical visual impairment. A child with CVI is often a child with additional handicaps. If the visual center in the cortex is damaged, other parts of the cortex is usually also damaged, so that the child may also be epileptic, spastic, have a hearing loss or have a generally slow capacity to learn. The child may also have emotional problems, perhaps displaying fearful or autisticlike behavior, or it may be the child's behavior is dominated by stereotyped activities.
Any of these handicaps will have some influence on the process of learning to see as well as on learning to understand what has been seen.
In the work of both caring for and educating the child, we must take into account any condition that could decrease the child's learning processes, including learning to see, so that the child is given optimal opportunity to utilize and develop whatever ability to see that is present at any time.
How can we as parents and/or teachers do this and
what should we refrain from doing?
Maybe the answers to these questions can be found by immersing ourselves in the ways in which the non-handicapped infant learns to see and learns to understand what he sees. Learning to see is a dynamic process.
In the non-handicapped infant who is as yet unable to move around, this process happens step by step in approximately the following sequence:
- Visual awareness
- Looking alternately at a person, an object and own hands.
- Varying the length of time spent in looking at an object from brief to prolonged.
- Showing preference for a specific visual experience such as for something that moves.
- Reaching towards the person or object being regarded.
- Pushing an object, and then looking at the result.
- Trying to grasp the observed object.
- Grasping and letting go the observed object.
- Turning an object whilst looking at it.
- Looking for a lost object without discovering it.
- Looking at or for another object.
- Comparing visual experiences.
- Visually following a person or an object that moves away.
- Looking for a lost object, discovering it and reaching for it if it is within reach.
- Looking at details of faces and objects.
By means of hundreds of repetitions of the visual experiences at each of these stages the infant learns to see and also commences to combine visual information with information gained from other sensory modalities. Gradually the child becomes able to distinguish between various persons and objects without either having to touch them or having to have support from auditory information. He knows what he can do with the objects with which he has been active and he recognizes certain persons just by looking at them.
Whether the child with CVI commences to display visual awareness at the age of four, or eight or 10 years he still has to go through the same dynamic process of learning to see and learning to understand what he sees. In my opinion it is impossible to train or teach a child to see. You can lead a horse to water, but you cannot make him drink. The horse will drink if he is thirsty but he will only be able to drink if there is water in the watering trough and if the watering trough is placed low enough.
In the same way we can bring the CVI child to a visually stimulating environment, but we cannot force the child to see, and the child will only commence to see if the environment includes something that motivates the child to look. Furthermore, we may be exposing the child to a difficult situation by encouraging him to look or in other ways showing that we expect him to see, because we may have choosen a time during which he is functioning as blind. To put pressure on the child to get him to use more sight than he wants to may lead him to avoid using his ability to see or contribute to his turning inwards and switching off his awareness to the surroundings - to persons as well as objects and events.
While the non-handicapped infant is breastfed or bottlefed, as well as when the adult is attending to his needs bending over him at a distance of 30-40 centimetres, the infant has the opportunity to look at the adult's face. At this level of the learning process the infant does not see the details of the adult's features. He looks at the darker parts of the face such as eyes, mouth, nostrils and hairline (Blanksby, 1992; Slater, 1989). When the infant is about three months old he will not only look at but also reach towards the adult's face, especially towards the moving mouth and eyes.
When has the four, eight or ten years old child
with CVI the opportunity to do something like this?
When the child with CVI finally does commence to see, he has little opportunity to learn to discriminate by looking at moving and immobile parts of faces. Faces are coming and going too fast for him to perceive the view of them. There may be little opportunity to discriminate between features in objects either. Thus it may not become meaningful for the child with CVI to orientate by means of sight.
Maybe it would be of help for this child to give him opportunities to look at an object made from a piece of yellow circular cardboard on each side of which is painted black hair, eyes and mouth. If this "face" is hung on a thin thread it will turn around and maybe "move" enough to inspire the child to look at it. This "face" should be hung close to the child so that he can make tactile contact with it when ready to reach for it.
Blanksby, D.C. (1992): VAP-CAP Handbook. Royal Victorian Institute for the Blind, Burwood, Australia.
Groenveld, M., Jan,J.E. & Leader,P. (1990): Observations of the Habilitation of Children with Cortical Visual Impairment. Journal of Visual Impairment & Blindness. January.
Morse, M.T. (1990): Cortical Visual Impairment in Young Children with Multiple Disabilities. Journal of Visual Impairment & Blindness. May.
Slater, A. (1989): Visual Memory and Perception in Early Infancy. In Infant Development (Ed. Slater, A. & Bremner, G.). Lawrence Erlbaum Associates, London.
Steendam, M. (1989): Cortical Visual Impairment in Children. Royal Blind Society, New South wales, Australia.
This article was printed in the journal "Information Exchange" July 1995.