Investigation of vision strategies used in a dynamic visual acuity task

Abstract

Purpose: Dynamic visual acuity (DVA), the ability to resolve fine details of a moving target, requires spatial resolution and accurate oculomotor control. Individuals who engage in activities in highly dynamic visual environments are thought to have superior dynamic visual acuity and utilize different gaze behaviours (fixations, smooth pursuits, and saccades). This study was designed to test the hypothesis that athletes and video game players (VGPs) have superior DVA to controls. Furthermore, the study was designed to investigate why DVA may be different between groups. Methods: A pre-registered, cross-sectional study examined static visual acuity (SVA), DVA, smooth pursuit gains, and gaze behaviours (fixations, smooth pursuits, and saccades) in 46 emmetropic participants (15 athletes, 11 VGPs, and 20 controls). Athletes were members of varsity teams (or equivalent) who played dynamic sports (such as hockey, soccer, and baseball) for more than 1 year with a current participation of more than 6 hours per week. VGPs played action video games four times per week for a minimum of one hour per day. Controls did not play sports or video games. SVA (LogMAR) was tested with an Early Treatment Diabetic Retinopathy Study (ETDRS) chart. DVA (LogMAR; mov&, V&mp Vision Suite) was tested with Tumbling E optotypes that moved either horizontally (left to right) or randomly (Brownian motion) at 5°/s, 10°/s, 20°/s, or 30°/s. Task response time was measured by averaging the amount of time it took to respond to each letter per trial (i.e random 30°/s, horizontal 10°/s, etc.) which indicated the time it took for a motor response to occur. Smooth pursuit gains were tested with El-Mar eye tracker while participants completed a step-ramp task with the same respective velocities as the DVA task. A one-way independent measures ANOVA was used to analyze smooth pursuits. Relative duration of gaze behaviours were measured with the Arrington eye tracker while participants performed the DVA task. A one-way independent measures ANOVA was used to test for group differences in SVA. A one-way ANOVA was used to test for group and speed differences in DVA. A repeated-measures two-way ANOVA was used to compare gaze behaviours of the first five and last five letters of 30°/s velocity. Results: SVA was not significantly different between groups (p=0.595). Random motion DVA at 30°/s was significantly different between groups (p=0.039), specifically between athletes and controls (p=0.030). Thus, athletes were better than controls at random 30°/s. Horizontal motion DVA at 30°/s was also significantly between groups (p=0.031). Post-hoc analysis revealed a significant difference between athletes and VGPs (p=0.046). This suggests that athletes were better than VGPs at horizontal 30°/s. DVA task response time per letter was not significantly different between groups for horizontal motion at 30°/s (p=0.707) or random motion at 30°/s (p=0.723). Therefore, the motor response times were similar between groups at both motion types. Smooth pursuit gains were not significantly different between group at 30°/s (p=0.100) which indicates similar physiological eye movements. Eye movement gaze behaviours of horizontal motion at 30°/s were not significant between each groups for fixations (p=0.598), smooth pursuits (p=0.226), and saccades (p=0.523). Similarly, there was no significant difference in gaze behaviours for random motion at 30°/s between groups, for fixation (p=0.503), smooth pursuits (p=0.481), and saccades (p=0.507). Thus, gaze behaviours for horizontal and random motion were similar for all groups. Conclusion: Athletes exhibited superior DVA for randomly moving targets compared to controls, and superior DVA for horizontally moving targets compared to VGPs. The task response times, gaze behaviours and smooth pursuit gains of each group were not significantly different. Therefore task response times, smooth pursuit gains and gaze behaviours cannot explain the superior DVA displayed by the athletes. Further research is required in order to determine why DVA in athletes is superior at 30°/s.