Many children can be affected by a single CVI, the commonest being a reduction in clarity of vision (reduced visual acuity). Others though may have a number of CVIs. These tend to come in typical patterns that relate to the parts of the brain affected and the cause of brain event. We have called these patterns CVI Clusters and the common ones are listed below.
If you look at the Brain Location page you will see that it is the layout of the visual functions in the brain and how close together they are physically in the brain that leads to these clusters.
If the child you support, has a CVI in one of these groups, we think it is worth seeking out the visual difficulties related to the other CVIs, in case they are also present.
Validated approaches to identify these CVIs are available for medical professionals, but we are aware that testing to seek out evidence of the individual CVIs listed on our CVIs page are not available in all parts of the world.
For more information on the individual CVIs please see the CVIs page.
Children with CVI can be affected mildly to profoundly. Understanding which CVIs the child is affected by is just one part of what one needs to know about them, to help make sure that support is optimal. Please also see our page The Lists (for profiling people with CVI).
This list does not cover every combination and our experts have seen other varieties outside of these groups too.
CVI Cluster 1 Note: This may include the mildly affected children, whose difficulties with visual search can be made worse by clutter, stress or tiredness, yet they can go unnoticed. These children often perform well in mainstream schools but may have a few difficulties in the afternoon when they are tired after school, or have difficulties with sports requiring good hand eye coordination. In some cases, when damage extends into the temporal lobes, the recognition process may be affected, creating additional difficulties with recognition. This can however be very subtle, and easily missed if not sought out.
CVI Cluster 2 Note: This group is more common in slightly more severely affected children. As in CVI Cluster 1, visual recognition can also be affected, but it can be difficult to determine the exact cause of this.
CVI Cluster 3 Note: This group of visual difficulties, from birth, typically affects the child's global development most severely.
CVI Cluster 4 Note: Please see our page Combined Hemianopia and Visual Attention or Neglect. Hemi-inattention can be missed when combined with hemianopia both typically affecting the same side.
Lower Visual Field Impairment
A lower visual field impairment is a good indicator that CVIs called dorsal stream dysfunction (simultanagnostic vision and optic ataxia) may also be present. It might be only the lowermost slither of the lower visual field that is less clear, making tripping more likely. While in more profoundly affected children, a marked absence of vision in the lower half of the visual field, is a strong indicator of accompanying dorsal stream dysfunction, possibly at the more severe level called Balint Syndrome.
In the video below, from Lesson 3d Visual Fields (at 4.08 minutes) a way to understand if the lower visual field is typical, is demonstrated by Professor Gordon Dutton.
Providing a detailed list of CVIs that are present for a complex and non-verbal child can be difficult, but this information is very much worth looking out for. If the child is visually unresponsive in the lower half of their visual field, we think the initial assumption should be that they are likely to have marked simultanagnostic vision and optic ataxia. If they respond well in a quiet uncluttered environment, then this is an indicator that this assumption is probably correct.
From many accounts we also believe that light gazing, a behaviour found in many profoundly affected children, may be due to the competing elements of simultanagnostic vision, with bright light being the greatest attractor of attention. See our page Light Gazing.
If a profoundly learning delayed child has known reduced visual acuity, it is very possible they have the combination in CVI Cluster 3. Dorsal stream dysfunction is commonly present in such children who have reduced visual acuity. Ideally each affected child needs to have each CVI identified, but where this is not possible, these suggestions may help the child considerably.
Some profoundly disabled children are not considered to have a visual impairment because their visual acuity has been found to be typical. In this group they may still have CVI Cluster 1 or more likely 2. One way to look for this is to seek out whether visual reactions to movement in the lower visual field are present.
Supporting a child with multiple CVIs.
Each CVI affects the child's vision all the time, so they all need to be accommodated all the time. This might sound very complicated, but one parent has explained how they learnt to understand their child's multiple CVIs with simplicity:
I think of it like looking after a group of children, and each has one very simple need, and if I can get them all right, I have a happy group who learn well together. One of these children needs things to be very slow, another needs things to stay where they are, another needs only one thing at a time in an uncluttered room, another needs things to be higher up to be seen, while another needs strong contrast and another needs things to be bigger. Put together these are all the different visual impairments in the same boy. And a happy group is a happy boy!
It's not always easy, if he gets up and goes for a walk about, then for him, everything starts to move, and the careful one thing at a time world, becomes a world of lots of things popping in and out of vision. At home and school we keep his world very consistent, but very quickly when out and about he becomes disorientated and confused, apart from when we take him to the beach. If he lies down, which he likes to do, the single object that has carefully been placed up high, is no longer where it can be seen - it has disappeared for him!
There is no perfect solution, but being mindful of these different needs has made a world of difference to my son. At first it felt very complicated, which is why I had to make it simple like this, and now it is second nature.
Looking at the different 'simple' needs in this account:
Combined Reduced Visual Acuity & Simultanagnostic Vision
Where visual acuity is reduced and simultanagnostic vision is present, there as is a problem because making things bigger to make them clearer, might also make them less clear. The approach we have found that works well is to build things up one thing at a time, a bit like building a jigsaw. We explain this with different examples in our sections 'Jigsaw' Learning Using 3Z Approach (zoom in zip up zoom out). For a more detailed explanation see our page The Visual Acuity / Simultanagnostic Vision Problem.
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