CVI: mixed messages

22 July 2021

Cerebral visual impairment is the most common cause of vision problems in primary school-age children but the condition can often slip through the net. Journalist Jo Waters reports on the strategies for supporting children.

Cerebral visual impairment (CVI) is probably the most common disability in children you’ve never heard of. An umbrella term, it’s used to describe a range of vision conditions in children that originate in the brain rather than the eyes (although it’s important to state that one doesn’t exclude the other – some children with CVI will have an eye problem too). The eyes are supplying images to the brain, but the brain can’t sort or categorise them, which is why glasses don’t fix CVI.

CVI can cause reduced visual acuity, problems seeing contrast, lack of peripheral vision, difficulties with shape and face recognition and problems seeing moving objects.

How it starts

Causes of CVI can include any condition that affects the brain, such as hypoxia at birth, premature birth and meningitis, says Dr Cathy Williams, associate professor of paediatric ophthalmology at Bristol University, and a consultant paediatric ophthalmologist at University Hospitals Bristol and Weston NHS Foundation Trust. ‘Using imaging techniques, we can see areas of brain damage or scarring so we understand that is the cause,’ says Cathy. ‘In others, the structure of the brain is normal, but we can see it’s not working properly in terms of vision, and newer imaging techniques show that it’s the connections that are not working.

‘There are some genetic conditions [such as ATR-X, Mowat-Wilson and Pitt-Hopkins syndromes] that can cause CVI too. There are so many different types of visual impairment that come under this umbrella and there will be a different mechanism for each.’

‘CVI is not well known because it’s a complicated condition, and most health professionals aren’t taught about it during their training,’ says Professor Gordon Dutton, professor emeritus of visual science at Glasgow Caledonian University, and former consultant paediatric ophthalmologist at the Royal Hospital for Sick Children, Glasgow, who wrote one of the first papers on CVI in 1995 and three textbooks on the subject.

‘Unfortunately, a lot of cases are either missed or misdiagnosed as having another condition such as autism, ADHD or learning disabilities. But some children with CVI can show typical features of autism as well, and CVI is an important reason for learning disabilities, and needs to be considered as a potential cause. Yet getting a diagnosis of CVI can be transformative for some children as they can be given the right support to help them cope with their impairment. For some that could be something as simple as being given a large print book or a typoscope – a piece of plastic with a slot to cut out the “clutter” on the page of a book.

‘Many of these children currently get a raw deal as they are not being picked up by health professionals including paediatric ophthalmologists, community paediatricians and neurologists.’

Janet Harwood, a specialist vision impairment teacher in Sussex, and chair of trustees of the CVI Society, says delays in diagnosis can lead to children being labelled as having a learning disability and ‘written off’. ‘The majority of children with CVI in mainstream primary schools are shockingly underestimated,’ she says. ‘There is also the issue of parents not being believed, told they are over-anxious and being dismissed. It can be frustrating for them.’

‘Unfortunately, a lot of cases are either missed or misdiagnosed as having another condition such as autism, ADHD or learning disabilities’

Features in babies and children

CVI features vary in severity and nature according to the cause, but Professor Dutton says there are clues early on in a child’s life that health visitors can pick up on, and that the more severe the condition, the earlier it is usually spotted.

‘Of course, vision is still developing in a newborn, but later on, parents will report that their baby isn’t seeing – this can be due to CVI or ocular causes – and needs checking out. Parents of CVI toddlers will notice their child moves away from them as they approach and that’s because the child’s brain is not mapping properly. If children are not meeting developmental milestones, they should be referred to a developmental paediatrician.

‘By the age of four or five, most children will be able to find a toy you ask them to get in a toy box, but a child with CVI won’t and will have several adaptive strategies to cover this. They will either tip all the toys on the floor to find it or they will take the top one by default. Failing that, they will ask someone to find it for them.

‘One of the key features of CVI can be impairment of the visual field – a child might not be able to see to the left or right or down below. These children won’t go downstairs, they will trip and fall often and appear clumsy or be unable to find things, struggle to walk over rough ground and grab on to a parent’s clothing as a tactile guide.’

Cathy says symptoms can include clumsiness, bumping into things, difficulties keeping their eyes on a line of text, changing eye position, or staying focused and not recognising shapes or people. ‘But it must be remembered that vision problems are not the only causes of these difficulties.’

Janet adds that a child being unable to maintain eye contact or appearing not to look or listen to things that appear obvious are other clues they may have CVI. ‘Equally, they may get anxious when other children are milling around – they may push them away or act clingy. There are clues from an early age if you know what you are looking for, but the trouble is all the emphasis is on other conditions such as autism and ADHD, which are much better known.

Professor Dutton says: ‘For some individuals with CVI the behaviours they adopt resemble autism. For example they don’t return your gaze because it feels uncomfortable to do so, or they can’t identify people or perhaps don’t see the language of facial expression, which suggests that they lack “theory of mind”. In this situation, autism is a differential diagnosis.

‘Those trained in autism but not CVI can understandably therefore make a diagnosis of autism, when the cause of the behaviours is in fact CVI, if they have yet to learn of this alternative.

‘Other individuals with CVI can have all the features of autism as well, when it is effectively a dual diagnosis.’

Janet says that getting the right diagnosis is crucial. ‘Some of the children will just about hold things together in school but the pressure of trying to keep up may cause them to have meltdowns at home. When they move on to secondary school, if they don’t get a diagnosis and the right help it can be too overwhelming, and many present with anxiety, anger, school avoidance or self-harm.’

How common is CVI?

New research by the Bristol University Medical School, led by Cathy, has found that 3% of primary aged children may have CVI – much more common than was previously thought (Williams et al, 2021).

The team also found that children who were struggling with their learning and were already being given extra help at school were more likely to have brain-related vision problems: four in every 10 children with support for special educational needs had one or more brain-related vision problem, while for all children it was only about three in 100.

Cathy says: ‘While this does not prove that these kinds of vision problem are the cause of the difficulties with learning for any particular child, it does suggest that attending to children's visual needs, such as making things bigger or less cluttered, might be a good place to start. If interventions can work to reduce the impact of these problems on children’s learning, it might improve both educational and wellbeing outcomes for children.’

Diagnosis and management

The diagnosis of CVI usually involves input from several sources including parents, eye specialists, teachers, paediatricians and educational or neuropsychologists and is not based on a one-off test.

‘There are a number of problems we can test for in age-related tests,’ explains Cathy. ‘These include how far a child can read down a vision chart, and tests to see if they have an impaired visual field, and we can find out if their problems do or don’t equate to CVI. These tests are not done routinely but can be done by any vision professional who has been trained, with experience of testing children, particularly children with additional needs.

‘Even standard eye tests are very important though, to see if a child needs glasses. I think it would be taking a sledgehammer to crack a nut to say all children should be assessed for CVI, but my suggestion is that children who flag up as having a problem in their development and learning should have a detailed vision assessment (looking for signs of CVI) as part of the investigations that are offered or recommended.

Cathy says there’s no magic pill or injection to treat CVI, yet the condition can be managed with techniques for specific impairments, which can make a big difference. Early-onset CVI that has been diagnosed in childhood often persists into adulthood, but in less marked cases the features can abate as the child develops or learns alternative approaches.

These include simple changes such as making text bigger, and making type-size adjustments on tablets and laptops. ‘If in doubt, don’t wait for a diagnosis of CVI, make things bigger, bolder and less cluttered – it doesn’t cost any money and that alone might really help a child to work as well as their peers,’ says Cathy. ‘But we are making great discoveries in other areas of vision conditions, including retinal conditions that were previously untreatable. So I have every confidence that in five, 10 or 15 years we will have treatments for CVI.’

Professor Dutton says the University of Edinburgh has developed the Insight software programme to provide practical suggestions to support CVI children with 52 specific problems. The software is a good resource for health professionals and teachers.



‘In Scotland we have also developed the VINCYP (Visual Impairment Network for Children and Young People) service, where health professionals can refer children for a visual assessment and get educational support for them.’

What is the CP’s role?

‘Apart from signposting, I think the main thing is for HVs and nursery nurses to be aware of CVI – if a child is not developing as expected it’s worth asking if vision problems could be part of this, especially if they have had any problems affecting their brain, such as cerebral palsy, or have a red flag such as being born prematurely. Getting an eye test or a referral to a specialist would be the next step,’ says Cathy. ‘And don’t be afraid to make things bigger to see if a child responds better.

‘In babies – if they are not responding to toys with black and white contrast (or bold red, yellow, blue ), multi-sensory toys or shiny and illuminated toys, try stimulating them with something lighter or shinier to see if that makes a difference.’

Getting CVI included in medical school and allied health professionals’ training, drawing up guidelines and developing new treatments are all really crucial, says Professor Dutton, as is greater public awareness of the condition. ‘Things are improving, different professions are now working together more. We just need more health professionals to think about vision and consider CVI.’


  • Contact the CVI Society for advice and support
  • CVI Scotland has resources and learning materials
  • The CVI Project is a five-year programme of National Institute of Health Research-funded work investigating the prevalence and effects of CVI, and how best to support children with the condition
  • Insight, a software Q&A for health professionals on CVI, has practical suggestions for dealing with specific impairments
  • Visual Impairment Network for Children and Young People in Scotland


Williams C, Pease A, Warnes P et al. (2021) Cerebral visual impairment-related vision problems in primary school children: a cross-sectional survey. Developmental Medicine and Child Neurology 63(6): 683-9. See: (accessed 10 June 2021).

Image Credit | Shutterstock

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