CVI is a medical condition, which means in most countries that only a medical doctor can diagnose it. This is a problem, because of:
So, screening questionnaires are used, to give an indication of whether CVI is likely. However, the result of a screening questionnaire does not provide a diagnosis, though it may be a pointer to a diagnosis.
Screening questionnaires, if considered reliable, are particularly useful in research.
This paper looks at the reliability of two sets of screening questions:
1) The CVI Questionnaire (reference below)
This is a set of forty-six questions about different things a child may find difficult. The forty-six questions are in six different categories. For CVI to be considered likely, at least one question in four of the six boxes needs to be answered 'yes'.
Reference: Ortibus E, Laenen A, Verhoeven J, De Cock P, Casteels I, Schoolmeesters B, Buyck A, Lagae L. Screening for cerebral visual impairment: value of a CVI questionnaire. Neuropediatrics. 2011 Aug;42(04):138-47.
2) The Five Questions (reference below)
Each of the five questions, of things a child may find difficult, are answered:
CVI would be considered likely if at least three out of the five questions were answered always or often.
Reference: Dutton GN, Calvert J, Ibrahim H, Macdonald E, McCulloch DL, Macintyre-Beon C, Spowart KM. Structured clinical history taking for cognitive and perceptual visual dysfunction and for profound visual disabilities due to damage to the brain in children. Visual impairment in children due to damage to the brain. Mac Keith Press, London. 2010 Jan 1:117-28.
The five questions, where CVI is indicated, in practice is followed up by a further fifty question inventory and salient testing of vision, to confirm a suspected diagnosis and to establish which CVIs the person is affected by. This paper considers the five questions, not the fifty. The five questions comparatively could become a quick and easy screening tool, if found to be effective.
This researcher asked members of the public, caring for children aged between 5 and 18, to complete a survey, which asked for information about their child, including if they had CVI, and whether they were affected by a number of other conditions.
There were 535 participants of whom 104 (or 19%) had stated that the young person had CVI. This research did not follow up with diagnosis or check the responses for accuracy.
The paper notes:
It cannot be assumed that parents who attest to their child having CVI do so on the basis of a diagnostic test, therefore, it is possible that some incidents of reported CVI are erroneous. Given the large sample size, we suggest that this potential error will be small enough that it will not affect the veracity of the results.
And with this, a very big thank you needs to be extended to those who kindly participated. This research project was embraced by parents, carers, teachers and many others supporting children with CVI, and was widely shared, particularly across social media. Because of very large number of parents and carers who found a few minutes to complete this survey, both the scope of the research and the resulting recommendations are given more weight.
Through statistical analysis, both screening questionnaires were considered to have:
good convergent validity, internal consistency and a reliable factor structure and may therefore be suitable as screening tools
What does this mean?
This means that if others want to research a different area of CVI, they can confidently use these screening questions, whichever is more suitable, as a part of their research.
Establishing the validity of these screening questions will hopefully make future research into CVI, more relevant and accurate.
Here we start to enter the world of confusing labels. The paper notes that some of the screening questions, cross over into different areas, for example reading and writing difficulties where a child has CVI and difficulty reading, could be caused by dyslexia not CVI. But...CVI can cause reading and writing difficulties, but not all reading and writing difficulties are dyslexia, and CVI can cause impaired reading not related to dyslexia. Confused?
The following links explain a little more about CVI and dyslexia / reading and writing difficulties:
This paper highlights many areas where there are similar grounds for confusion.
104 of the 535 had CVI, but what about the other 431?
Of these, depending of the screening test, between...
55 (12.8%) using the five questions, and
166 (38.5%) using the CVI questionnaire
...met the criteria, as described above, for CVI to be possible. These are called Potential CVI.
It is not unreasonable to assume that the children in this group, if affected by CVI, are affected less obviously, as they have not been previously diagnosed. However, this does not necessarily mean that their potential CVI would be less severe in its impact.
One might think that the shorter five questions would likely result in more children being identified as Potential CVI, as opposed to the longer CVI Questionnaire - whereas the opposite is true. Three times more children were identified as Potential CVI using the CVI Questionnaire compared to the five questions.
This research has a higher than average percentage of participants with additional support needs, so it is not a typical representation across all children.
We just don't know, and without further evidence, there is no point speculating.
The table Figure 2 looks at this group of children with Potential CVI.
Allowing for the differences in screening questions, the results of the group Potential CVI is fascinating - what else do they have? Virtually none has 'no diagnosis'. The majority are affected by ASD, or ADHD, hearing problems, learning difficulties, dyslexia etc.
Again, we go back to the problem with labels. If these children have CVI, and possibly they do, has it been misdiagnosed as ASD or ADHD or dyslexia or any of the other conditions mentioned? Or could the child have CVI and ASD, ADHD, or Dyslexia? We know from personal experience of children, that CVI can cause all the difficulties in these groups. But, we also know from children who have been assessed, that, for example, CVI can be present, and partly responsible for their difficulties, but cannot alone account for all of their difficulties - so there must be something else. Confused?
It is confusing, particularly where medical conditions and behavioural labels are confused and interchanged as the same thing - they aren't. That is not to say the behaviours are not real and they can cause profound difficulties to all aspects of life and learning.
The many different brain-based impairments of vision that come under the CVI umbrella are medical conditions. They cause behaviours but may not be the only cause.
Of the original sample of 535 children:
181 (or 34%) had no diagnosis
104 (19%) had CVI
55-166 had likely undiagnosed CVI (of which a few had no diagnosis)
So roughly between 100 and 200 children (depending on which screening questionnaire is used) have conditions or difficulties, or both. Where they may have ASD or ADHD or dyslexia or other difficulties, just because CVI is not reported as a factor, it does not mean there is not a cause. Just because a cause is not known, it does not mean it does not exist. In Level 2 of our lessons we look at the many different elements that need to come together for effective learning (please complete Level 1 first). This understanding is relevant for everyone.
1) It would be really useful to learn more about the group with Potential CVI, because this will help targeting CVI assessment and testing. Questions to screen for CVI have to be very carefully written, so that ideally a CVI alone is identified, and the difficulties cannot easily be explained in terms of any other conditions.
2) The scale of CVI is unknown, but some suggest 3-5% across the population, some higher - however the vast majority are only mildly affected, with most unaware they are affected. The systems of medical support could not cope with the volume of widescale medical assessment and diagnosis - but what is the alternative, as this is a medical condition? Does CVI need identification when mild? The person will have some difficulties, and understanding their CVI will undoubtedly help, but do they need a doctor for this? This paper notes:
Expert testing for CVI is likely to be costly and not feasible at the population level.
On some level, this needs to be discussed, to seek a practical way of getting the right support to the right people.
3) Labels - they have their uses, particularly when it comes to apportioning support as there have to be systems to measure needs, but the child is not a label. Untangling the complex world of a child takes patience, motivation, understanding and an expert knowledge of that child - the parent or carer has to be central.
Thank you - to all the people who shared this and found the time to complete the survey. This is an incredibly useful piece of research, that will help other researchers looking into CVI further. Please, if relevant, look to find the time to participate in research and share - we all benefit from good research, like this.
Paper: Towards population screening for Cerebral Visual Impairment: Validity of the Five Questions and the CVI Questionnaire, Gorrie F. et al. PLOS, Published: March 26, 2019
Your generous donations will be put to immediate use in supporting our charity...
At CVI Scotland we are devoted to helping people understand cerebral visual impairments, and together working towards developing the understanding of this complex condition.