Cerebral visual impairment (CVI) is probably the most common cause of childhood visual impairment in the UK. It isn’t a problem with the eyes, but with the brain’s visual pathways. Varying in severity, some children are identified as being blind from birth, while at the other end of the spectrum, the condition can go undiagnosed. Expert ophthalmologist Mr Richard Bowman explains:
What is cerebral visual impairment (CVI)?
A good way of thinking about CVI is as a visual version of cerebral palsy (the two often go together). Sometimes it’s been there from an early age and may be due to some medical problem from that time, e.g. premature birth or lack of oxygen to the brain around that time.
In CVI, the problem is that the visual pathways in the brain are damaged, rather than the eyes. In the brain, the visual pathways for the eyes are close to the pathways for the arms and legs, and therefore some children have cerebral palsy as well as well as CVI.
The severity of the problem varies. Some children at the severe end are identified as being blind from being a baby, while at the opposite end of the spectrum the condition may go undiagnosed – the child is thought to be clumsy in crowded environments, or maybe not doing well at school.
Although it’s due to a problem in the brain, children with CVI often have problems like strabismus as well, so they need a thorough eye exam and may also benefit from glasses.
What are the top 6 characteristics of CVI?
Any child who’s got a known medical history of brain injury and has vision problems is a suspect for having CVI. Some of the key features at the milder end of the spectrum where it can be missed include:
- Inability to process a lot of visual information at once – in a crowded environment e.g. a crowded street or supermarket, the child may not be able to pick out their parent.
- The child may struggle in the playground – thought to be shy or have a social problem, but there may actually be a visual element.
- Trouble reading – particularly as children get older and are given smaller text to read. They may be able to read a single item on a page, but may struggle with the full text.
- Motor skills – we use vision subconsciously to help us move through the world. CVI can cause apparent clumsiness or trouble copying shapes and letters.
- Difficulty seeing fast-moving objects. Many patients do fine in eye tests, as they are looking at still letters. Their problems aren’t recognised, and they don’t get help.
- Difficulty picking out distant objects.
None of the features in themselves means a child has CVI – there may be other causes for any of them, but in the context of previous brain injury/prematurity, the possibility of a visual contribution should be explored.
How to manage CVI
Like cerebral palsy – CVI is a disability, and we can’t necessarily fix the brain damage. However, there are lots of things we can do to maximise visual potential of a child with CVI.
- Basic visual assessment, as with any child with other problems. Some of these children may have more than one condition. Electrophysiology testing can measure brainwaves while a child is watching a screen to see visual responses.
- Check for squints and treat with glasses.
- Discussion between the parents and the doctor in some detail about all these different aspects of vision in practice. The doctor can try to build up a picture of the child’s visual problems, using their expertise of what problems go together. This gives the parents the best possible understanding.
- Set out the home environment in a way that benefits the child – this may be a set of strategies from the doctor’s practical experience. A good understanding of practical problems and practical solutions is key.
There is not a cure-all for CVI, but these are various things we can do to minimise the impact of the disability.
Although Mr Bowman doesn’t do neuro-psychological testing, he does work closely with neuro-psychologists and can arrange these tests. Patients shouldn’t come to the clinic expecting a test immediately, but he can refer you to a neuro-psychologist to get better idea of what visual problems your child has.
Mr Bowman deals with general aspects of ophthalmology as well as having a specialist interest in this area.