Despite nearly 25 years of research on the topic, there is still no consensus on whether prism adaptation is an effective therapy for visuospatial neglect. We present a meta-analysis from 1998 to 2021 on immediate treatment effects measured by paper-and-pencil clinical tests (BIT-C and cancellation tasks combined), and a standard assessment of neglect in everyday activities (Catherine Bergego Scale). We combined the Behavioural Inattention Test-conventional sub-tests (BIT-C) and cancellation scores into one random effect meta-analytic model, justified by the fact that 89% of the BIT-C score is determined by cancellation tasks. With this approach, we were able to obtain a larger dataset than previous meta-analyses while also including a more specific patient sample: right hemisphere stroke patients with left-sided neglect. We found no evidence for beneficial effects of prism adaptation within our main meta-analytic model (BIT-C/cancellation) where sixteen randomised and non-random controlled trials, altogether including 430 patients for the task of interest, were included. Nor did we find evidence for therapeutic effects as measured by CBS, albeit half as many studies were available for this analysis. The lack of effect was consistent after the removal of influential outliers, when studies with high risk-of-bias were excluded, and when an alternative measure of effect size was considered. These results do not support the routine use of prism adaptation as therapy for spatial neglect.

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