Understanding the Behaviours of Children With CVI

A position paper by Lea Hyvärinen, MD

For the SKI-HI Institute Webcasts March and April 2004


Motto:

"Although we have the idea that we see things as they really are, in fact our brain is using shortcuts, best guesses and assumptions about the world to make our perceptions seem continuous.

If some parts of the visual pathways or cortical functions are not normal, the perception of the surrounding world, people and social and emotional relationships may be changed in only one or a few situations, or it may be greatly distorted. The important thing in early intervention and special education is to try to understand the child's visual perception and its integration with information from the other modalities as well as memory."

Basic Brain Structures and Cerebral Visual Impairment (CVI)

It is much easier to understand the often-puzzling behaviors of children with CVI if we know a few basic facts about the visual pathways and functions of the visual cortices. The key features to know and to teach to parents and every person who is involved with the care and education of the child are:

  1. the fact that there are parallel visual pathways makes it possible for some parts of the brain to receive visual information when other parts are damaged,
  2. the brain cortex has more than 30 specialized areas that handle specific parts of visual information.

We do not need to know exactly where these specific small areas are located, but we do need to know that each of these areas may be damaged by a localized lesion that does not interfere with other visual areas.

brain diagram showing the main pathway and the tectal pathway

This is a simplified drawing of the visual pathways in the brain seen from the side. We usually think of visual pathways as a pathway from the retina of the eye to the primary visual cortex, V1, located in the back of the brain. Midway in this pathway is the lateral geniculate nucleus (LGN) where the first nerve cell passes the information to the second nerve cell.

There is another pathway, the tectal pathway that leaves the main pathway before the LGN and brings visual information to several groups of cells: superior colliculus (SC), the center for rapid eye movements; and pulvinar (PU), where information gets to the cortical areas in the parietal and occipital lobes without going through the form analysis in V1.

Because of the presence of these two parallel visual pathways, some areas of the brain may get normal visual information via the tectal pathway when the main pathway is damaged in its posterior area. In such situations, children may have normal, or near normal, vision for orientation in space, good eye-hand coordination, and poor or no functions in visual recognition tasks. On the other hand, damage to the parietal lobe may disturb vision-hand or vision-foot coordination because the visual "maps" are unreliable, making some movements easier with eyes closed than with eyes open.

CVI is usually described as impaired functions of the posterior parts of the brain. There are, however, important cortical visual functions also in the frontal lobes that execute command functions (e.g., to visually attend to objects, to turn the eyes and head in anticipation of looking in a certain direction). Inflow of visual information activates the whole brain by activating the reticular formation. This is called arousal: we wake up and become more visually aware of surrounding space and activities in that space.

Causes of Cortical Visual Impairment

Children born prematurely (a large group), as well as some infants born at term may have had poor circulation in the brain before, during, or after birth or have had infection or trauma of the brain. As a result, they have lost function of small, circumscribed areas in the primary visual cortex, in the nerve fibres that transfer the information to the visual cortex, or in cortical areas where visual information is used for many recognition tasks or for eye-hand coordination. There are also numerous rare syndromes and conditions that cause abnormalities in the structure or functional development of the parts of the brain related to vision.

Many children with CVI have other problems caused by brain damage or malfunction of other parts of the body. Cerebral palsy and intellectual disabilities are the most common other impairments. Hearing impairment is common in small prematurely born infants and in several syndromes. Specific memory problems and problems in emotional development complicate the diagnosis, especially if the infant's first months of life have been in a hospital because of operations and the infant has been deprived of normal interaction with his/her parents. Brain damage is usually stable and an impaired visual system is capable of improving many functions. If a child with CVI has seizures, the seizures and medications may seriously affect development of all brain functions.

The type and degree of brain damage varies so much that it is difficult to describe a typical infant or child with vision loss due to brain damage. There are long lists of typical features, but an unusual behaviour that is said to be typical to CVI may have varying causes and may sometimes be related to something quite different from brain damage. Therefore, it is mandatory to pause and ask "Do I know why this child has this strange behaviour in this situation? If I do not understand the cause, is there someone who might help me understand?"

During these five Webcasts lectures, I will show examples of children whose behaviours would easily be misunderstood if they were not thoroughly examined clinically and then observed for months, sometimes years, by their families, therapists, and teachers. Only through this transdisciplinary functional assessment can we help each other better understand these children.

Most of the participants in these Webcasts lectures will be teachers. Therefore some problems of school-age children will be mentioned. However, the lectures will try to give information for observation and assessment of visual functioning before school age so that early intervention, training, and teaching can support each infant's/child's development. In the following text some of the common behaviours of these children are described, as well the possible reasons for the behaviours. I have used bold text more than usual so that the most important facts will be easier to notice. I would greatly appreciate any comments from the participants.

Understanding Behaviours of Children with CVI and Assessment and Intervention Strategies

The Effect of Image Quality

Before we can assess associative brain functions, we need to know as much as possible about the quality of the image that the child uses to visually perceive. Ophthalmologists can usually describe the likely quality of the picture based on the changes in the structures of the eyes and the structure of the nerve head. The retina may look totally detached, yet the infant/child clearly sees, or the eyes may look perfectly normal and the infant/child functions like a severely visually impaired child.

If there is major damage to the eyes or optic nerves, the function of the posterior visual pathways and/or cortex is difficult to assess. The test materials need to be modified to correspond to the child's possibility of seeing them. For example, quite often test pictures are drawings with rather faint black-and-white lines and, thus, parts of the pictures may be invisible, which changes the content of the information. Communication during testing may or may not pay attention to the child's possibilities to perceive expressions and/or hear instructions, which again may distort the test results and lead to wrong conclusions. Thus, we have to take results from measurements of visual field, visual acuity, contrast sensitivity, colour vision, and other clinical tests with caution and repeat them over several years to get the most accurate picture of the child's functioning. We must also compare the results from these measures with the information that we get from observation of visual functioning and from formal clinical tests such as MRI, CT, EEG and VEP (when they can be measured).

Refractive Errors, Accommodation and Oculomotor Functions

Refractive errors and accommodation need to be compensated for during all testing and observations. The tester/observer needs to know whether the child uses the eyes together (binocular vision), uses only one eye, or uses eyes alternatingly. The last possibility is often a source of much confusion. If the child changes fixation between the eyes rapidly during a test situation, the tester does not know where the child was looking when (s)he responded. For example, a child with inward squint (crossed eyes), may look with the right eye at a test picture on the left side of the test paper, which the tester is briefly pointing at. At the same time the left eye's fixation is on another picture on the right side of the paper. If fixation changes from the right eye to the left eye at the time the tester's finger disappears, the child may respond by telling about the picture at the left side of the paper. Children who freely alternate need to be tested with one eye covered. Covering an eye may disturb the child and thus decrease motivation during testing. In the classroom, the child may have this same difficulty if not trained to prefer one eye for near, the other eye for distance. This can be supported by prescribing a reading lens for the better eye and distance correction for the eye with poorer image quality.

When glasses have been prescribed for a child, information should be provided about how they were fitted and what the glasses correct (i.e., Do the glasses correct the basic refractive error or under/over correct it? At what distance is the infant/child likely to see best?).

Accommodation may be normal, insufficient, jerky or spastic. If the cornea, lens and vitreous are clear, accommodation is easy to measure (i.e., whether the refractive state changes when an interesting small object with high contrast details is brought closer the child's eyes). If the child can focus at the object, refraction moves toward myopia. If the child cannot accommodate, there is no change. Often a brain-damaged child also has fixation problems, so the eyes may wander past the object several times before they stop at the object. It may then take several seconds before accommodation suddenly "snaps in" for a few seconds and then relaxes. Although it is possible to read even despite poor fixation and accommodation, we should know about the enormous patience and endurance a child with this kind of oculomotor functions has to have in order to get through a normal school day. Reading lenses such as progressive lenses may facilitate use of vision long before the child learns to read and should therefore be evaluated in each case of poor accommodation.

Refractive errors and insufficient accommodation are the earliest clinical findings that can be measured in an infant with otherwise normal looking eyes. Every infant with deviations from normal in early interaction or in motor development should be carefully assessed for the possibility of abnormal visual experiences as a contributing factor to the deviation from normal development. Sometimes it is possible to make a tentative diagnosis just watching the infant's pupils. If the pupils of an infant do not constrict (become smaller) when an interesting toy moves close to the eyes, then accommodation may be affected. Accommodation, convergence (eyes turning inward when looking at objects near the eyes) and miosis (the pupils becoming smaller) are all related to small groups of cells which are close to each other. Therefore, the three functions that may be affected with refractive error are accommodation, convergence and miosis. It is possible that only one of them is impaired, as happened in a 12 year-old Finnish girl who lost accommodation during measles, but had no other neurological signs. It is the smallest brain damage causing loss of an important visual function that I have seen during my 40 years in ophthalmology.

Spastic accommodation is a much more difficult problem than insufficient accommodation. It means that during the typical head thrust backwards, the spasm occurs also in the muscles inside the eyes. It appears at the same time as the spasms of larger muscles and often tends not to get better with time. Spastic accommodation may make the child momentarily highly myopic, up to 15 diopters and, thus, the surrounding environment disappears in a blur. There is little we can do for these spasms. Theoretically, we can prevent them by using atropine-like medications. However, the medications are not really useful because during the spasms the child is not looking at a target. However, caretakers and teachers should understand this disturbance and how it affects the quality of visual images and allow the child time to recover from the spasms.

Saccades (fast eye movements that shift gaze from one fixation to the next) are "planned" by the functions in superior colliculus. Changes in its functions or changes in the functions of the twelve muscles that move the eyes may disturb saccades. Saccadic movements may be slower than normal, inexact in landing at the target, or there may be no fast eye movements at all. Since we use saccades to read, abnormal saccadic functions disturb reading. If the child has good head control, head movements may be used instead of eye movements. Most children who have poor saccadic movements also have poor head control and often also CP with poor hand functions. Therefore, their learning strategies need to be carefully assessed. Many children may be able to read by using single, large words on the computer screenCif the spacing of letters is wide enough and the text is supported by auditory information. Every child with CP should be observed for their eye movements during reading by recording the eye movements on video through the text printed on transparent film.

Photophobia

Photophobia (increased light sensitivity) is a common problem in children with even slight optic atrophy or retinal changes. There are several good filter lenses and absorption lenses (sunglasses) that should be evaluated as part of the clinical examination so that photophobia does not interfere with functional assessment. The lenses that correct for refractive errors can be tinted with limited extra cost.

Visual field

Visual field defects are difficult to measure in young children. We need to try to imagine whether there may be patchy losses in the visual field until clinical measurements are possible in the school-age years. If a child has fixation difficulties, nystagmus, or difficulties in directing attention, we may never be able to make reliable measurements.

If a child has optic atrophy with some loss of visual acuity and contrast sensitivity and changes in colour vision, the child may have a central scotoma. If the loss of visual field in its center is so severe that the quality of the image is better in areas surrounding the central field, then the child will use these surrounding areas of the visual field and will seem to look past an object/person when looking at it. This leaves the observers with the impression that the child is looking past them or the object. Central scotoma is very common in children with CVI and should always be looked for in children with brain damage. If an infant "avoids eye contact" the reason may be the use of best possible image (i.e., eccentric fixation) and not disturbed interaction.

Patchy field loss is very difficult to verify before 9-10 years of age. If a child can recognise pictures of known objects drawn quite small but does not recognise them when they are drawn large, it may be related to a small island of reasonably well functioning central field vision surrounded by field loss.

Field defects are important to know for assessment of perception of space and later for physical education (PE). If a child bumps into furniture or other children, there can be loss of visual field or the child has difficulties in directing his/her attention. We need to observe whether it is always the same area of the visual field (e.g., side, quadrant, or lower part) where information is missed. This is done as a normal part of therapies and play situations until measurement in the laboratory is possible. When homonymous hemianopsia (loss of half of the visual field on the same side of both eyes) is diagnosed, it is important to know that there may be perception of motion present even if the standard Goldmann visual field test shows no function. This occurs when damage to the visual pathways is in the most posterior (back) part of the pathways. Thus, visual information can enter the cortical functions through the tectal pathway (via superior colliculus and pulvinar) without form analysis in the occipital lobe.

When the lower part of the visual field functions poorly, the child bends his/her head to see where the foot is going to land. This leads to poor posture if the child does not learn long cane techniques to compensate for loss of vision in the lower part of the visual field.

Small defects or scotomas (especially on the right side of the fixation point), need to be evaluated if the child makes unusual errors in reading. If increasing the size of the text makes the errors disappear at a certain size, the child does not have dyslexia but changes in the central visual field. Let's look at the following example where a small scotoma "eats up" two letters located 3-4 letters to the right of the fixation point. This reader is a young child who still fixates at the beginning of the word and then moves to the right:

"In a small town there was a pretty girl who"

When fixating on the word "In," the child will miss the word "a" (not read it) and go directly to "small" where the second "l" will not be visible, but will appear when the fixation moves to the "m." When fixating on the "a" to complete the word "small," the next word may look like "own," because the child misses the first letter "t." The next word is seen as "here;" the next "as;" the "a" missed, etc. If the child has good command of language, (s)he will fixate backwards to check the words, which may be interpreted as a sign of dyslexia. If the text is enlarged 2x (e.g., from 12 point to 28-point text), the small scotoma is too small to cover the entire letter so the child is aware of the letter and will move on it to see what it is.

"In a small town there was"

Visual Acuity

If recognition of optotypes is poor, visual acuity of children with brain damage needs to be measured with single symbols, symbols in line test and more tightly grouped symbols, as well as grating acuity. If there is greater than normal difference between the visual acuity measured with single symbols than that measured with the more crowded symbols, then the child has difficulties in keeping details of the image apart from each other (i.e. has increased crowding phenomenon). This will likely affect the child's possibilities of seeing pictures where details are close together or slightly overlapping. This is one of the most common problems in communication of speechless children. Pictures used in communication often contain far too many details and overlapping parts—so the child does not see the picture as we see it, but as a blob of colours with perhaps one or two discernable details. Increased crowding may also affect recognition of objects on patterned backgrounds.

Infants and young children may not have a clear enough concept of "sameness" so they may not be able to compare test optotypes. This is why I designed the Lea Puzzle—the most useful thing I ever created for testing. By playing with it and combining it with the puzzle game, we can start assessing visual acuity before the child is 18 months old. (See www.lea-test.fi >> Games.) If a child has brain damage, the play situation may reveal at an early age that the child can handle form information through colour perception—but not in black-and-white. This is very important information both for diagnosis and for early intervention teaching.

If visual acuity is poor, grating acuity should be measured. It is the only way to measure visual acuity in infants during a usual clinical examination. However, it does not measure the same function as recognition of optotypes and, therefore, grating acuity values must never be converted to optotype acuities. Unfortunately, this happens now in many hospitals and causes problems in the life of children who have measurable grating acuity but may not have any form perception and thus no optotype acuity. Values below 6 cycles per degree (cpd) may not be related to cortical visual function because the superior colliculus can handle grating information up to 6 cpd. This has been shown in monkeys and has been demonstrated by a patient of mine, whose occipital lobes were damaged soon after birth.

Contrast Sensitivity

Contrast sensitivity is not regularly assessed in clinical examinations. It should be known that visual information at low contrast is important in visual communication and in perceiving the structure of the environment. Extreme situations occur in the northern states on cloudy winter days when everything is white and shadows are faint. For a child or adult person with poor contrast sensitivity in this environment, there is nothing to be seen.

In communication situations much information is conveyed through expressions. Expressions are low contrast shadows in motion. If they are not seen, the face is a motionless flat surface. Such vision loss affects early interaction because the lack of perception of expressions decreases the child's responses, which in turn makes the parents feel the baby is not interested in them. Therefore, the very simple measurement with the low contrast Hiding Heidi pictures may make the family and other caretakers aware of the need of being very close to the infant/child and of using make-up to improve visibility of their faces. If an infant responds with a smile to the smiling Heidi pictures, we learn that the infant recognises the smiling face and copies it. This measures numerous connections between brain function related to vision, motor functions, memory and emotions.

Colour Vision

Colour vision often seems to be less impaired than black-and white form vision. This may be related to the fact that bright basic colours are seen at the level of the superior colliculus. If cortical discrimination of colour hues is disturbed, the child can still perceive differences between bright basic colours. Some children with fairly good colour vision may have great difficulty naming colours because the visual memory pathways to "names" are damaged or the ability to form a template for names is poor. Therefore colour perception needs to be assessed using several test situations such as matching colours (exactly same colours), sorting colours so that the next colour is the closest in hue to the previous one, and naming colour hues.

You can train children for colour vision testing by playing the colour vision game on my homepage www.lea-test >> Games.

Motion Perception

Motion perception (perceiving visual information that moves) may be disturbed. Either the child has difficulties in seeing objects that stand still or has difficulties in seeing objects that move. Inability to perceive movement is rare but does occur in children. If moving objects cannot be seen, traffic and most games are nearly impossible to cope with. Orientation and mobility training of these children requires an instructor who is well trained in functional problems related to brain damage. If motion perception is disturbed, lip-reading or speech-reading becomes poor and perception of finger spelling and rapid signs may be lost.

Motion perception can be observed from early on. Does the infant prefer a slowly moving toy hanging close to a toy equally bright in colours but not moving, or vice versa? Does a fast rolling ball seem to disappear? There is also a game for motion perception in the Games Section on my homepage. It is the picture of my brother's much loved dog, Pepi (a Dalmatian). The picture is formed by dots in coherent motion; there is no surrounding line. This game also helps to assess saccades and the central visual field. When a child grows, traffic is an important test field for motion perception. Ball games are another good test situation.

Now when we have considered the most important confusing changes in the image quality we can start assessing functions that are called "higher visual functions" or visual perception. In a way the term "higher" visual functions is misleading because these functions are at the same level as, for example, visual acuity. Visual acuity is a part of form perception; it is perception and recognition of geometric forms. It requires both form perception and visual memory and, additionally, a strategy to answer. Similarly, contrast sensitivity, colour vision, and motion perception are each at the same level of cortical functions as are recognition of facial features or eye-hand coordination. In the early phase of "analysis" of a visual image there are some details that may be damaged or lost and, thus, may cause difficulties in using vision. Two of them can be assessed at a young age; they are direction of lines and length of lines.

Perception of length or orientation of lines can be assessed using easy test games (Lea Rectangles and Mailbox) and drawing lines of different lengths, parallel lines, and lines that form angles and crosses. Visual perception of the length and orientation of lines occurs in the lower part of the temporal lobe. Information creating the visual maps for adjusting finger positions to grasp or turn is handled in the parietal lobe. Therefore a child may not see length and/or orientation of lines but may be able to use this information for hand movements. In this case the damage is either in the primary visual cortex or in the temporal lobe. The opposite functional damage is also possible if there is localised damage to the parietal lobes. In this case, the grasping movements are inaccurate, although the child can tell which line or rectangle is longer and which is shorter. Similarly, the ability to perceive the orientation of lines and adjust a card so it is parallel to a slot may each be independently damaged, even if the functions seem to use the same visual information. The specific areas in the temporal lobe (for purely visual analysis of length or orientation) and in the parietal lobe (for vision-hand coordination) are far enough from each other that one of them may be damaged and the other function well.

Recognition of facial features is a socially important function that may be lost. If the parents and the therapists are aware of the possibility of loss of this function, they can often notice the typical signs when the infant is 11 months old. An infant with loss of face recognition does not respond differently to known and unknown people when they approach without saying anything, but responds differently to voices of known and unknown people. It is an important observation that should lead to early training of interaction using other sources of information and to compensating strategies to prevent frustrations in communication situations.

Recognition of facial expressions may be difficult for several reasons: the image quality may be poor; contrast sensitivity so low that the faint shadows that convey expressions are not seen; or perception of expressions is not functioning at the cortical level. This ability may only be a partially lost function. Early training by watching expressions in a magnifying mirror or describing expressions and how people feel when they have different expressions will often lead to marked improvement in social interactions in groups of toddlers and young children.

Picture perception and picture comprehension varies and is important to assess, especially if pictures are used to support communication. A child may not be able to see complicated pictures, although parts of the same picture may be perceived when shown in isolation. Composing a whole picture from its parts may be a lost ability in an otherwise well functioning student.

There is a variety of pictures used in communication systems. In some pictures, there are objects partially covering each other (e.g., an apple and sandwich on a plate). Some pictures use too many objects (e.g., four children close together representing gymnastics). In some pictures the key object is too small (e.g., cleaning represented by a table, an arm, and a very small triangle depicting the cleaning cloth). Before pictures can be meaningfully used in communication, the child needs to have the concept that pictures represent objects. The child must be able to see the structure of the picture, not just different blobs of colours. Much work is needed in this area of designing pictures for communication with children who are not able to speak or use sign language.

Perception of depth should not be confused with stereovision. Stereovision is a small part of visual information that we use to experience three dimensionality. Perception of relative movement of objects at different distances when we move, or during head movements, is a more powerful source of information about the three dimensional structure of the environment. Shadows, partial occlusion of objects behind other objects, and relative size of known objects effectively convey information on depth when a child has experienced movement that (s)he has caused him/herself. These children may not see the difference between shadows and thresholds or potholes, but will explore shadows with their feet before stepping on them. For example, if depth perception is impaired, a boy may not understand how other boys dare to jump down from a fence or a low wall. The boy may hesitate and feel himself inferior, then decides to jump anyway. Because he cannot anticipate the distance he will fall, he may hurt himself and be laughed at by the other boys. This might cause the boy to feel even more inferior. To prevent blows to his/her self-image, it is important to explain to the child what the problem is and teach him/her strategies for overcoming difficult situations.

Perception of surface qualities is an often missed problem, although when looked for is easy to notice. Such a child may benefit from use of long cane techniques despite "good" central vision measured as visual acuity and contrast sensitivity values. This problem sometimes occurs in children who also have difficulties in understanding spatial relationships and/or in recognising and remembering landmarks. Moving is likely to be a stressful situation if a child does not really perceive the surface that (s)he is walking on, where (s)he is, and/or does not experience him/herself as part of the environment.

Spatial awareness and orientation in space are disturbed in parietal lobe lesions. They may also be poorly developed because the child who cannot move by him/herself, but has always been moved passively (e.g., carried, pushed around in a wheelchair), has not been properly trained. Orientation and mobility training of a student with CVI and using a wheelchair is a special area that requires a well trained instructor who is willing to carefully observe what the child can perceive of his/her environment and how that information is interpreted. Testing of auditory spatial concepts and visual memory are an integral part of assessment of vision for these children.

Eye-hand coordination (vision-hand coordination) may also be affected in parietal lesions leading to clumsiness that is caused by poor visual maps for hand movements. Some children with CVI turn their head away from the object they are trying to reach. This may be related to poor visual feedback during the movement and can be diagnosed by asking the child/student to close his/her eyes instead of turning their head. If reaching is easier with their eyes closed rather than when looking at the object, visual information disturbs motor performance instead of making it more precise.

Simultan agnosia may be a problem of a child with CVI. It means that the child can direct attention to only one detail or object at a time. It makes measurement of visual fields very difficult because during the usual measurement the child should look straight ahead and observe when a light or fingers appear on the side. In such cases, the test is performed in another way. The child is instructed to look at the fixation mark and move the eyes to the moving light spot as soon as it becomes visible anywhere in the test cupola, instead of responding by pressing the button. The reflex movement of the eyes does not require decision-making and is thus a much faster and easier response.

Effect of posture on the use of vision needs to be assessed together with the child's therapist and teacher. When head control is poor, a therapist or assistant may be needed to support the head so the child can concentrate on the visual and visuomotor tasks. Use of multimedia goggles (virtual reality glasses) may be considered for some near vision tasks.

Neuropsychological testing is important in each case of CVI, although several difficulties can be observed and evaluated during therapies and in many teaching situations. Neuropsychological tests may need to be modified to meet the needs of the student in terms of contrast, size, and number of details to be seen at once.

Some Concluding Thoughts

Our understanding of a child's functioning is a step-by-step process. The child's pediatrician, ophthalmologist, optometrist, neurologist, and psychologist start to collect the information. The child's special education teacher, therapists, regular classroom teacher and teacher's aid, guided by a vision teacher, are instrumental in completing the clinical findings. The team at the school and in day care needs only a few new tests to perform a comprehensive functional assessment when supported by a vision teacher and when working in good collaboration with a pediatric ophthalmologist and an intervention team.

If information about CVI is available at clinics, private offices, day care centres, and schools for all those who are involved in the education and care of children with CVI, the services will improve without any added cost. In many cases we can use sound common sense in assessing children's problems. For each of the above mentioned symptoms and signs, we need to ask: "Does this child have this particular difficulty?" "Do we know it or do we need to ask someone else who knows?" When we notice an impaired function, we should ask ourselves, "How does it affect:

Assessment of vision of children with CVI is an ongoing process that should be discussed several times during the first year and at least twice a year in preschool age children.

When directing our attention to visual functioning, we should remember to consider each child's other impaired functions that may be even more disabling than the visual impairment. Integration of visual information with information from other modalities may be problematic. If moving requires nearly all the child's brain capacity, the child may be functionally blind when moving about his or her environment. Therefore, the child may have to stop to look around and then move again based on the visual map in memory.

These infants and children may have limited tolerance for information around them. Many are disturbed by auditory information and/or movement around them. A noisy group of toddlers may be a nightmare for a toddler with CVI, whose only retreat may be to play alone in the farthest corner.

The most typical feature of functioning of children with CVI is variation. A real part of this variation is caused by changes in brain functions because of the basic condition and changes caused by varying effects of medications and fatigue. Another part of experienced variation is related to misunderstanding. When a child has just performed a difficult task and then fails to complete an "easier" task, we may not realize that the task which is easier for us is actually more difficult for the child. Functions needed by the child to complete the "easier" task might be some of the functions that are impaired.

In the assessment of children who have very poor functions in the hands and arms, I would like to mention a feature that I do not see discussed anywhere. It is the role of hands and mouth in learning to see. A normal baby explores his/her hands with the mouth for months and explores every toy and many other objects by mouthing. If this function is not possible without help and that help is not given, visual information must be far more abstract than in children who have been able to learn the structure of objects by confirming the visual image with tactile and haptic information.

The increasing interest in CVI will bring together workers who can make new observations on infants and children with brain damage. We can hope that our diagnostic skills will improve so that early intervention will begin really early in the child's life and that we meet the needs of these children when planning their environment and social interactions and learning.

A Checklist of Possible Behavioural Characteristics of CVI
Lea Hyvärinen

What may be different in the vision of a child with CVI?

  1. Image quality changes:

  2. Oculomotor deficiencies

  3. Changes in the function on the primary and the associative visual cortices

  4. Changes in compensatory functions


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