The Relationship Between Visual Function and Performance in Para Swimming

BACKGROUND: Paralympic swimmers with vision impairment (VI) currently compete in one of the three classes depending on their visual acuity (VA) and/or visual field. However, there is no evidence to suggest that a three-class system is the most legitimate approach for classification in swimming, or that the tests of VA and visual field are the most suitable. An evidence-based approach is required to establish the relationship between visual function and performance in the sport. Therefore, the aim of this study was to establish the relationship between visual function and performance in VI Para swimming. The swimming performance of 45 elite VI swimmers was evaluated during international competitions by measuring the total race time, start time, clean swim velocity, ability to swim in a straight line, turn time, and finish time. Visual function was measured using a test battery that included VA, contrast sensitivity, light sensitivity, depth perception, visual search, and motion perception. RESULTS: Results revealed that VA was the best predictor of total race time (r = 0.40, p < 0.01), though the relationship was not linear. Decision tree analysis suggested that only two classes were necessary for legitimate competition in VI swimming, with a single cut-off between 2.6 and 3.5 logMAR. No further significant association remained between visual function and performance in either of the two resulting classes (all |rs|< 0.11 and ps > 0.54). CONCLUSIONS: Results suggest that legitimate competition in VI swimming requires one class for partially sighted and another for functionally blind athletes.