Background: The deterioration of the integrity of binocular vision has a detrimental effect on fine visuomotor skills, however, its impact on sports performance remains unknown. We tested the influence of four viewing conditions (binocular viewing, monocular viewing, binocular viewing with monocular blur, and binocular viewing with binocular blur) on basketball free-throws performance. Methods: Twenty-three male basketball players (19.2 ± 3.4 years) performed 30 free-throws in each viewing condition following a randomised order. Image degradation was induced by the use of Bangerter filters. Complementarily, perceived levels of task load and complexity, as well as visual function were assessed. Results: We found a worse basketball free-throws performance (percentage of successful shots) in the monocular viewing (~8%) and binocular viewing with monocular blur (~9%) in comparison to the condition of binocular viewing (corrected p-values = 0.003 and 0.006; and ds = 0.838 and 0.771). The analyses of subjective ratings and visual function allowed us to confirm a successful experimental manipulation. Conclusions: Basketball free-throws performance is subject to the integrity of binocular vision, showing a worse accuracy when the sensory dominant eye was occluded or blurred in comparison to natural (binocular) viewing conditions. However, free-throws performance remains stable when the visual acuity is binocularly degraded. Our findings reveal that an appropriate functioning of the binocular vision is needed for optimal sports performance, and highlight the importance of a comprehensive clinical assessment or management of binocular vision in sport contexts.
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