[Effects of simulated combined visual acuity and visual field impairments on obstacle avoidance walking and searching...

Objective: To investigate the interactive effects of combined visual acuity and visual field impairments on obstacle avoidance walking and searching abilities. Methods: A randomized controlled trial was conducted. Healthy volunteers with normal visual acuity and visual fields were recruited from the Eye Hospital of Wenzhou Medical University between March and September 2024. Binocular presented visual acuity (PVA) was measured using a standard logarithmic visual acuity chart, and binocular visual field was examined using a Humphrey perimeter. Visual function impairments were simulated. Four levels of visual acuity impairment (PVA<0.05, 0.05≤PVA<0.3, 0.3≤PVA<0.5, and PVA≥0.5) were induced by applying occlusion foils of different densities onto the spectacle lenses. Two levels of concentric visual field constriction (visual field radius≤10° and≤20°) were simulated using modified goggle-based tunnel vision simulation glasses. Participants were randomly assigned to four visual acuity simulation groups using computer-generated random numbers, and further randomly assigned in a 1∶2 ratio to the 10° and 20° visual field subgroups within each group. Each participant completed an obstacle avoidance walking task and a target search task under both simulated visual field impairment and normal visual field conditions. The primary outcome measures were task completion time, number of collisions, and target detection rate. The Kruskal-Wallis test and linear mixed-effects model were used for statistical analysis. Results: A total of 143 participants were included [aged(23.94±2.23) years; 55 males and 88 females], with 95 under the simulated 20° visual field condition and 48 under the simulated 10° visual field condition. Under the normal visual field condition, participants in the PVA<0.05 group showed longer obstacle avoidance walking completion time (23.00 s vs. 17.50 s), an increased mean number of collisions (0.75 vs. 0.00), and a decreased target detection rate (80% vs. 100%) compared with those in the PVA≥0.5 group (all P<0.05). At any given level of visual acuity, participants with 20° or 10° visual field constriction demonstrated prolonged task completion time, a reduced target detection rate, and an increased mean number of collisions compared with those with normal visual field (all P<0.05). For example, in the PVA≥0.5 group, the obstacle avoidance walking completion time increased from 17.50 s under normal visual field to 25.50 s and 39.88 s under 20° and 10° visual field constriction, respectively, with the target detection rate decreasing from 100% to 90% and 80%. Both tasks were affected by the interaction between visual acuity and visual field impairments under specific deficit combinations. The combination of 20° visual field constriction and PVA<0.05 showed the most extensive impact, with the obstacle avoidance walking completion time reaching 55.50 s, mean number of collisions reaching 5.50, and target detection rate decreasing to 50%, and significant interaction effects were observed on the task completion time, target detection rate, and collision counts (all P<0.05). Conclusions: Visual field impairment exerts a more pronounced effect on obstacle avoidance walking and target search tasks than visual acuity impairment. Combined visual acuity and visual field impairments produce a compounded interference effect on the performance of both tasks.