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Aim: To develop a data‐driven subgrouping method to identify and profile subtypes of early‐onset childhood cerebral visual impairment (CVI). Method: Sixty‐three children with suspected or diagnosed congenital CVI were recruited (28 males, 35 females, median age=8y, range=5–16y). Cognitive, basic, and higher‐order vision functions were assessed and quality of life, functional vision questionnaire, neurodevelopmental, and ophthalmological data were collected. Cluster analysis and other statistical analyses were undertaken to determine and validate the subgrouping. Results: Forty‐three participants completing the full test battery were included in cluster analysis, revealing two subgroups. Group A1 (n=15) showed selective visual perception and visuomotor deficits. Group A2 (n=28) showed more severe and broader visual perception and visuomotor deficits, and variable visual acuity. A third, lower‐functioning group, Group B (n=20), was differentiated and showed significant visual acuity reduction compared with Group A (p<0.001, V=0.69). External validation showed significant cooccurring ophthalmological (e.g. strabismus p<0.001, V=0.59) and motor impairment differences (χ2=16.26, p<0.001, V=0.51) between the three groups. All groups had lowered parent‐reported quality of life and everyday functional vision. Interpretation: Statistical analyses revealed three subgroups with differentiated vision function characteristics on a gradient of severity. The subgrouping method provides the first steps in developing a novel classification system to underpin future clinical diagnostics and profiling of early‐onset CVI. What this paper adds: Three data‐driven subgroups of vision function deficits were identified.A similar severity gradient was shown in cooccurring cognitive and neurodevelopmental deficits.Reported quality of life and functional vision difficulties were low across all groups. What this paper adds: Three data‐driven subgroups of vision function deficits were identified.A similar severity gradient was shown in cooccurring cognitive and neurodevelopmental deficits.Reported quality of life and functional vision difficulties were low across all groups. This article is commented on by Dutton on page 245 of this issue. [ABSTRACT FROM AUTHOR]

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The childhood condition of visual difficulties caused by brain damage, commonly termed cortical or cerebral visual impairment (CVI), is well established but has no internationally accepted definition. Clarification of its core features is required to advance research and clinical practice. This systematic review aimed to identify the definitions of childhood CVI in the original scientific literature to describe and critically appraise a consensual definition of the condition. MEDLINE, EMBASE, PsychINFO, CINAHL and AMED databases were searched in January 2017. Studies were included if they (1) were published original research, (2) contained a childhood CVI sample, (3) contained a definition of CVI and (4) described their CVI identification/diagnostic method. Thematic analysis identified concepts within definitions and narrative synthesis was conducted. Of 1150 articles, 51 met inclusion criteria. Definitions were subdivided according to detail (descriptive definition, description not reaching definition status and diagnostic/ operationalising criteria). Three themes concerning visual deficits, eye health and brain integrity were identified (each containing subthemes) and analysed individually across definitions. The most common themes were 'visual impairment' (n=20), 'retrochiasmatic pathway damage'(n=13) and 'normal/near normal eye health' (n=15). The most consensual definition identified here may not be the best quality for advancing our understanding of CVI. We argue for the alternative definition: CVI is a verifiable visual dysfunction which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment. We propose reporting guidelines to permit comparison across studies and increase the evidence base for more reliable clinical assessment and diagnosis. [ABSTRACT FROM AUTHOR]