Children who in some respects behave like sighted children but in other situations either don't use their vision at all or use it in a unusual way, are diagnosed having "cortical vision impairment", "cognitive vision impairment", "cortical blindness" or "cerebral visual disturbance". Sometimes they are misdiagnosed as autistic children, and quite often they are inappropriately described as having "autistic features".

These many names reveal that the condition is difficult to describe and that most probably, there are numerous different entities that should not be lumped together. In many cases the diagnosis of "CVI" means that the child's eyes look normal and the lesion causing deviant visual performance is supposed to be located beyond LGN (the lateral geniculate nucleus) either in the cortex (surface of the brain) and/or subcortical pathways (deeper in the brain). Names like "cerebral visual disability, disturbance or dysfunction", CVD, are preferred, because so often both cortical and subcortical visual functions are involved.

Much of the text in this chapter covers the assessment of both children and adults. The tone of our communication with adults changes somewhat, but the tests and the observations are the same as for the assessment of infants and children.

Causes of brain damage vary in different countries. In western countries prematurity, numerous syndromes, infections, and accidental and non-accidental injuries may lead to brain damage that causes both impaired vision and other disabilities. After infection or injury, vision impairment may be masked by the poor overall condition of the child during the period of recovery. In these cases repeated functional assessment is necessary because vision may improve or in some cases get worse. Any changes should be reported to the carers and parents without delay in order to optimise management.

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