Impaired reach-to-grasp integration identifies cerebral visual impairment (CVI) in children and adults

Abstract Aim Cerebral Visual Impairment (CVI), an underdiagnosed cause of childhood visual impairment, presents heterogeneous symptoms involving varying degrees of dorsal and ventral stream dysfunction. We investigated whether impaired reach-to-grasp integration occurs in CVI as a potential marker of dorsal stream dysfunction. Method People with CVI (children aged 7-17, n = 16; adults aged 18-25, n = 6) and control participants (children, n = 14; adults, n = 10) reached with their left hand to grasp plastic blocks with and without a blindfold. Reach-to-grasp timing and hand shaping measures were assessed using frame-by-frame video analysis. Results Even when they could see the block, people with CVI displayed prolonged grasp relative to reach durations, more static hand shaping during the reach, and increased reliance on non-visual hand shaping strategies after block contact to secure final grasp. The three measures were incorporated into a single composite Reach-to-Grasp Integration (RGI) score that distinguished people with CVI from controls. Interpretation Temporal, sensory, and functional dissociation of the reach and grasp occurs in CVI, consistent with dorsal stream dysfunction, and is captured by the RGI score. The RGI score could form the basis for CVI behavioural screening tools beyond standard visual assessments. What this paper adds People with CVI display impaired visually-guided integration of the reach and grasp, consistent with dorsal stream dysfunction. People with CVI use static preplanned hand shapes during visually-guided reaching. People with CVI rely on non-visual hand shaping strategies after target contact to facilitate grasping. The composite Reach-to-Grasp Integration (RGI) score distinguishes CVI from control children and adults.