Irish College of Ophthalmologists, Annual Conference, Knockranny House Hotel, Westport, Co Mayo, 15-17 May 2024.
About one in 30 children may have some form of cerebral visual impairment (CVI), but it is vastly underdiagnosed, particularly in ‘healthy’ children, a leading international expert in the area told the Irish College of Ophthalmologists 2024 Annual Conference in Westport.
Dr Arvind Chandna, Senior Clinician Scientist, Smith Kettlewell Eye Research Institute, San Francisco, US, and Consultant Paediatric Ophthalmologist, Alder Hey Children’s Hospital, Liverpool, gave a talk at the meeting entitled: ‘Beyond visual acuity: Cerebral visual impairment – a structured approach.’
The brain is just as important as the eyes when it comes to vision, and many vision problems are caused by areas of the brain (which are needed for sight) not working properly – this issue cannot be resolved by wearing glasses, the meeting was told. Brain-related vision problems include difficulties with moving the eyes, visual field issues, and recognising objects accurately and quickly.
Dr Chandna explained that CVI is a heterogenous disorder of brain-based visual impairment resulting from brain injury or disruption in the development of retrochiasmatic visual pathways and vision processing regions of brain, commonly occurring during gestation and at, or around, birth. It is now the commonest cause of bilateral visual impairment in children in developed countries, and the prevalence is rising, largely as premature babies are more likely to survive now, he said.
It is often picked up in children with learning difficulties, autism, or ADHD.
CVI is typically diagnosed by observation of abnormal visually guided behaviours which indicate higher visual function deficits (HVFDs), suggesting abnormal brain development or brain damage in a child with a suitable clinical history – preterm birth or oxygen deprivation at birth are red flags, Dr Chandna noted.
However, HVFDs can occur even in the presence of good visual acuity and may remain undiagnosed because the good visual acuity does not prompt further investigation. This leads to a lack of understanding of the child’s visual perceptual difficulties, Dr Chandna commented.
“It is often not obvious, it is not strabismus, it is not a refractive error,” Dr Chandna said, describing CVI as an “invisible form of blindness”.
A UK study estimated that, on average, every class of 30 children would have one or two children with at least one brain-related vision problem.
To better diagnose and recognise CVI, Dr Chandna and his colleagues refined the validated Higher Visual Function Question Inventory into a subset of 11 questions (top-11). This can be used as an assessment tool to determine difficulties with vision in everyday life in children with CVI versus behaviours seen in typical children, and catches about 98 per cent of cases, he said.
Leave a Reply
You must be logged in to post a comment.