Cortical visual impairment (CVI) is a term used to describe visual impairment that occurs due to brain injury or growth abnormality. CVI differs from other types of visual impairment, which are due to physical problems with the eyes. CVI is caused by damage to the visual centers of the brain, which interferes with communication between the brain and the eyes. The visual pathway and the visual processing centers of the brain are damaged and this results in reduced vision. The eyes are able to see, but the brain is not interpreting what is being seen.
A significant visual characteristic of CVI is variable or inconsistent visual responses to the same visual stimuli. These children have inefficient and highly variable visual function. A child may appear to be visually more alert on one day compared to the next day and even hour.
Parents are most disturbed by the child’s lack of fixation and direct eye contact. Children with CVI may manifest with a non-purposeful gaze. They use their peripheral vision when looking and may appear as if they are looking away from the target. Look and touch occur as separate functions, they will look at a target for a moment and then turn away as they reach for it.
Affected children visually attend in near space only in an effort to magnify the object or to reduce crowding. Visual performance is better when the surrounding environment lacks clutter as they have difficulty differentiating between background and foreground visual information. Coloured objects may give better visual responses than black and white objects. Preferences are predominantly yellow and red but any colour may be preferred. Gazing at lights is a common feature among children with CVI. A third of children with CVI will be light sensitive but still gaze at light from time to time.
The eyes are able to see, but the brain is not interpreting what is being seen. This means that the incoming visual information is confusing, chaotic and does not make sense. The information cannot be sorted or organised and can be described as a kaleidoscope of pattern and colour without meaning. Visual symptoms can vary from mild to severe depending on the nature and extend of brain damage. It is often difficult to tell if a child has problems seeing clearly because of problems with communication, movement or learning difficulties.
A normal vision test is often not reliable with children with CVI. It is impossible for a child to respond to visual information when the information appears chaotic and overwhelming.
A CVI grading assessment will provide valuable information regarding a child’s ability to process visual information. It is used to describe how children with CVI see, determine appropriate intervention and to monitor progress.
CVI can get better with appropriate intervention. It is important for parents and carers to remember that children with CVI need to learn how to use visual information. Certain visual areas have been damaged or affected in children with CVI but new connections can be made. This is called ‘brain plasticity.’
Children with CVI can be over stimulated in an uncontrolled environment. The inability to cope with a sensory overload can result in withdrawal or even trigger self-abusive behaviour.
When the visual world is made simpler and more accessible, learning and progress can take place.
Keep toys and the environment simple and uncluttered, use books with one clear picture on a contrasting simple background. Children with CVI deal better with simple, constant and predictable visual information. Use familiar objects one at a time such as their cup or a favourite toy. Repetition is very helpful to provide security for the child. Familiarity and simplicity are very important.
Use bright fluorescent colours such as red, yellow, and orange since the colour system is often intact. Colour, high contrast and the use of motion may facilitate in the visual detection of an object. Try various light conditions. Some children respond better in a dark room while other performs better in dim light.
Positioning is important. Try moving the target that you want the child to see. Try to work in different visual fields. The child will demonstrate when and where they see best by their adaptive behaviours. Provide head support during work or play sessions; this will avoid involuntary shifting of the field. Children will also be more responsive when they are in a comfortable and stable position. Consistency of the environment may be helpful for children with orientation problems or those with a poor sense of localization and direction.
Frequent breaks should be given when doing visual activities; processing visual information takes a lot of energy causing the child to tire easily. Allow lots of time for children to see and respond to visual stimuli.
The prognosis depends largely on the original cause and severity of the neurological damage.
Visual rehabilitation plays an important part in the clinical management of children with CVI. This process may take several years and requires diligence and persistence depending on the cause of CVI. Due to medical advancements, children with neurological damage are surviving in increasing numbers. Many children with CVI are not correctly diagnosed and do not receive treatment.
For more information on cortical vision impairment contact:
Weltevreden Park, Illovo and Dainfern
011 475 2830
011 268 5854
011 469 5053
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