Development of a new classification system and proposed assessment protocol for childhood cerebral visual disorders

The most common clinical pathology of childhood visual impairment in the developed world is cerebral visual impairment (CVI), which includes visual impairment originating in the central nervous system and where there is no explanatory ocular condition. Because of the challenges in clinical assessment and heterogeneity of presentations within CVI, there have been several calls to develop an empirical assessment and classification system to systematically measure and classify symptoms of CVI. This study aimed to develop a clinical assessment protocol and classification system for childhood CVI from a scientific perspective. A comprehensive clinical assessment battery was designed to identify relevant vision-related symptoms and to establish scientifically the most useful assessment tests for the proposed assessment protocol. Sixty-nine children aged 5-16 years with diagnosed or suspected congenital CVI of mixed abilities, including a subgroup of children aged 8-16 years with relatively good visual acuity and average range cognitive functioning, were assessed on basic vision, higher vision cognitive and ophthalmological measures. Principal components analysis suggested that three areas of vision should be measured in a CVI assessment protocol: ‘spatial vision’ (Sonksen logMAR, LEA Contrast Sensitivity Symbols), ‘stereopsis’ (Frisby Stereotest), and ‘higher vision’ (Test of Visual Perceptual Skills, Beery Visuomotor Integration Test). The results of these five tests were subjected to two stages of statistical classification analysis, with findings suggesting that a three-group classification most appropriately represented the children in this sample. Validation analyses suggested that the basic and higher vision, cognitive and ophthalmological features of the groups were all in a gradient of severity. This supports a previously hypothesized framework of CVI based on severity degrees of vision (which parallel the paediatric characteristics). Despite differences in vision (and accompanying paediatric characteristics) between groups, the functional impact of CVI on daily activities and quality of life was similarly high across all groups. The results indicated that both basic and higher visual functions must be included in a comprehensive assessment of CVI, and strongly support a multidisciplinary approach to the clinical assessment of the condition. This classification system and its proposed assessment protocol may be valuable for assisting in the clinical assessment process and identification of CVI and its management needs, for establishing future clinical thresholds for CVI diagnoses, for comparing CVI presentations of different populations, and for systematically establishing prevalence and epidemiology of CVI at national population level