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What is CVI?

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CVI Pathway Introduction

Learning to See Inside-Out

The CVI pathway is an approach to learning how to understand the person's visual world from their perspective, that is inside-out, as opposed to understanding their world from our own perspective (outside-in) which is not possible.

To make sense we need to have a recap. If any of the following are unclear, please revisit the relevant section.

It helps a lot to have:

  • a basic understanding of visual processing by the brain from the Understand Section
  • an understanding that the form CVI takes is unique to each and every individual
  • an understanding that CVI varies according to both a) factors affecting the person like if they're stressed (egocentric) and b) environmental factors like noise and clutter (allocentric)
  • an understanding that the people with the best understanding of the person with CVI's visual world are those closest to them, the people who have spent the most time with them and are most committed to them, for example the parents and carers
  • a basic understanding of the terminology used, and the key areas of the brain dealing with vision (with further explanations being in plain English)
  • been observing the person's behaviour in different situations using the who what where when how and why approach

With this understanding, the number of different factors working together, affecting the person's visual world are huge, and too complicated for any sort of overall standardised measurement. With this in mind the next step is to demonstrate a pathway, using everything listed in the recap, to help you learn to understand the person's visual world, from inside out.

This step we've called the CVI Pathway which follows the same route through the brain as explained at the end of the Understand Section. However, before considering the effects and impact of CVI, you need some background information, including for example:

  • any other medical conditions that may be relevant, including seizures that can interfere with vision
  • the environment - is it busy, noisy, quiet, crowded, familiar etc
  • the lighting - is it dark, bright, hazy?
  • how the person is feeling - hungry, tired, excited, in pain etc

These sections described above we have called Pre CVI.

With this information we follow the pathway through the visual brain, in the order the brain processes vision. This is a scientifically based model of thinking but we are just using everyday language to explain it.

The visual brain processes in the following order:

  • the image is taken in through the eyes and goes first to the occipital lobes, where visual field, colour, contrast, acuity and movement (in the nearby middle temporal lobes) are analysed. This is Level 1
  • the analysed image information from Level 1 travels along the dorsal stream into the posterior parietal lobes where the scene is mapped to enable us to move through it. It is not a conscious process. Vision may be affected in the posterior parietal lobes creating challenges including simultanagnosia and optic ataxia, and may result in variable degrees of attention. Furthermore, the 'wires' of nerve fibres carrying the picture from the lower visual field passes through the same part of the brain, so the lower visual field may be absent or not work so well. This is Level 2
  • The image, with alterations from Level 1 travels along the ventral stream, to the temporal lobes where our visual memories are stored to give recognition. This recognised picture is mapped onto the 3D map made in the posterior parietal lobes. Brain injury or reduced function here impairs recognition. This is Level 3

At the end of Level 3 you should have a better understanding of how the person's visual world differs from yours, and the impact that difference has on their behaviour, actions and decision making process.

You are learning how to see their alternative world. Even if they do not face any other challenges, their CVI will have an impact on their whole being, not just their visual world.

Everything that has previously been described will be explained in much more detail, but using real examples. Each example will have multiple applications which will be listed. All explanations will follow this CVI Pathway in order.

Understanding and applying the CVI Pathway is a skill that improves with practice and over time becomes second nature. Eventually you will learn to understand the person's alternative visual world without even thinking about it. The knowledge you already have about the person is unique, and the CVI Pathway is a way to guide that knowledge through a process and turn it into understanding.

At the end of each example Further Suggestions will be considered, and a more technical explanation offered (in The Technical Stuff).

The CVI Pathway:

  • Pre-CVI
  • CVI Level 1
  • CVI Level 2
  • CVI Level 3
  • Further Suggestions
  • The Technical Stuff

This may seem like a very complicated and long process, but with practice quickly becomes second nature, as Connor's mother explains:

"The reality is that very quickly it becomes intuitive, without consciously processing I know based on the external environment and how Connor is feeling whether something is going to be challenging, appropriate, fun, awful, and make decisions accordingly - I'm applying the CVI Pathway - I don't need to think about whether he has any OVI or if he is affected by a seizure, I know all that, I know without thinking now if things are big enough, if there is sufficient contrast, where it is in his visual field and then the further challenges. It's like learning to swing a golf club - when you start there are about eight things you have to learn (feet, weight, grip, shoulders, head etc, but with practice you just know how to swing. When I think about it in full it's long, but when I apply it in practice it is so intuitive now it's barely conscious."

As has been mentioned several times throughout this website, it is not possible to absolutely know someone else's reality. This process is to help you learn to understand if it might be CVI, and if so which strategies would be most useful.

To demonstrate we have used some genuine case studies, where CVI has been diagnosed, and also where behaviours might suggest CVI.

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At CVI Scotland we are devoted to helping people understand cerebral visual impairments, and together working towards developing the understanding of this complex condition.