Cerebral visual impairment (CVI) are visual problems that arise from the brain (50% of which is used to process vision) rather than the eyes. Visual impairment related to the eyes is called ocular visual impairment. Mr Richard Bowman, a leading ophthalmic surgeon, explains what CVI is, its characteristics and how it may present.
What causes cerebral visual impairment (CVI)?
CVI may occur from brain injuries in which the visual centres of the brain are damaged. This damage then causes interference with how the eyes and brain communicate. In other words, the eyes are physically healthy, but the brain is unable to interpret the images being seen.
How can I tell if my child has CVI?
If your child has any visual problems you should take them to an optometrist or doctor to have the cause of the problem checked by a professional.
Whilst the characteristics and symptoms of CVI can vary greatly between patients, the following are common:
- Variable vision – visual ability can change from one day to the next, or between moments of tiredness and having more energy.
- Limited field of view – some with CVI might see better on their peripheral vision, and hence they might turn their head to view an object. Lower visual field loss will cause difficulties with going down steps and stairs or tripping over objects on the floor
- Limited depth perception – patients may struggle when reaching for an object, for example.
- Some objects are seen more than others – for example, familiar faces and objects are more easily perceived than others.
- Crowding phenomenon – experienced when viewing a picture, and the background and foreground cannot be differentiated.
- Difficulty seeing things that are moving – such as people on a busy pavement, or a ball which disappears when kicked.
Are some children at greater risk of CVI?
Yes, children who are known to have suffered any degree of brain problem or injury (even mild), especially around the time of birth, ex-premature children or children with cerebral palsy are more likely to have CVI.
What is the assessment for CVI?
Children with CVI need a full conventional ophthalmology assessment but may also benefit from specialist assessment by an ophthalmologist with an interest in CVI and from formal neuropsychological tests of visual perception.
How serious is CVI?
The term covers a huge range of visual ability. Some children at the mild end of the spectrum may have normal vision when measured in a conventional hospital eye clinic but still have problems with vision in everyday life (e.g. in crowded environments and with visual control of movement). At the other end of the spectrum, some children are severely visually impaired. Severe visual impairment is usually, but not always, accompanied by other neurodevelopmental problems, such as learning difficulties or mobility problems.
If you are concerned about your child’s visual health, make an appointment with an expert.