What is CVI?
CVI is the abbreviation for ‘cerebral visual impairment’. This is also referred to as visual perception disorder. CVI is an umbrella term for visual problems that originate in the brain’s processing of visual stimuli. The eyes of a child with CVI may be completely unaffected.
Which visual problems can occur as part of CVI?
A whole range of visual functions can be impaired in CVI. The severity of the impairments can vary from child to child and occur in different combinations. The following visual functions may be impaired in children with CVI:
- Perception of space, distance or 3D vision
- Shape recognition, size comparison
- Eye motor skills, eye control and visual acuity
- Recognition of colours, shapes or faces
- Visual attention
- Visuomotor coordination (e.g. eye-hand coordination, fine and gross motor skills)
- Visual exploration (of new, unfamiliar environments)
In addition, there are other visual functions performed by the brain that may be individually impaired. CVI can also occur in combination with numerous other disorders and impairments, such as auditory processing and perception disorders, autism spectrum disorders or other disorders and impairments.
How many children have CVI?
Our research project is investigating this question for the first time for children in Switzerland. This is based on research findings from comparable countries, which show that CVI appears to be much more common in childhood than previously assumed. For example, a project in England found that 3.4% of primary school children have CVI-related vision problems. The publication on this data states that almost one child per school class has at least one CVI-related vision problem.
What causes CVI?
The most common causes of CVI are health problems during pregnancy or during or shortly after birth. If the child experiences oxygen deprivation, low blood sugar or a stroke during this period, the areas of the brain responsible for visual perception may not develop fully, resulting in vision problems. In addition, injuries to the brain, e.g. as a result of an accident, can impair visual perception.
However, research into CVI in children also shows that a large number of children with CVI had no obvious health problems during pregnancy or birth and that the cause of CVI in these children is unknown (depending on the study, this is the case in up to 55% of children with CVI).
What are the consequences of CVI for a child?
Depending on its extent and intensity, CVI can have different consequences for children, and children with CVI exhibit different behaviours to cope with their impaired vision. This makes CVI unique in every child. Many children with CVI
- talk comparatively more because they supplement their impaired visual perception with auditory information.
- become exhausted more quickly than other children because they are much more visually challenged,
- often need more time to find their bearings visually (e.g. in new spatial environments or on a worksheet),
- exhibit behaviours that are similar to the symptoms of other disorders, such as autism spectrum disorder, ADHD, and dyslexia,
- are insecure and less self-confident because they cannot fully trust their perception.
Can CVI occur in combination with other developmental disorders?
Yes. CVI can also occur in combination with an auditory processing and perception disorder, for example. Furthermore, recent research shows that children diagnosed with autism spectrum disorder or dyslexia often also have CVI-related vision problems, but in many cases these are not recognised or diagnosed. As a result, these children cannot be given the best possible support and their behaviour is not sufficiently understood by those around them.
How can one imagine the vision of children with CVI?
The following short video from the Dutch organisation Bartiméus provides an insight into the characteristics of CVI in children (if you would like to watch this video with English subtitles, simply click on ‘Watch on YouTube’. On YouTube, you can then select subtitles in many different languages).
In the following videos from CVI Scotland, researchers, parents, children and young people with CVI have attempted to simulate the visual perception of people with CVI.
Another video illustrates how visual perception can change under certain conditions in CVI:
This video simulates how a young man with CVI perceives the world visually, what coping strategies he uses, and illustrates the overlaps in behaviour between people with CVI and people with autism spectrum disorder (If you would like to watch this video with English subtitles, simply click on ‘Watch on YouTube’. On YouTube, you can then select subtitles in many different languages).