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Alex A. Black, Ashley Burns, Ric Le, Gary Venz, Stephen Witt, Zhichao Wu, Joanne Wood; Gaze Behaviour And Mobility Performance Among Older Adults With Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1909.
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There is limited research linking gaze behaviour and mobility, particularly in high-risk falls populations such as older adults with age-related macular degeneration (AMD). This study examined gaze behaviour and mobility performance among older adults with AMD when walking in unfamiliar, challenging real-world environments, and assessed the effect of the inclusion of a secondary search task on performance.
The gait and eye movement patterns of nine older adults with AMD (mean age 78 ± 6 years) were assessed while navigating an indoor mobility course which was a 20m long, level, well-illuminated corridor, and included 34 floor-based obstacles of varying contrast and size. Participants walked along the course at their natural walking pace, and instructed to avoid contact with obstacles whilst wearing a video-based mobile head-mounted eye-tracker (ASL). An additional run included a secondary search task, which was to locate a specially marked door along the course. The order of the runs was randomised. Outcome measures included mobility performance (walking velocity, stride length and obstacle errors), as well as gaze behaviour measures (fixations per second, fixation duration and time fixated on obstacles).
For all runs, a higher rate of obstacle errors was significantly associated with more fixations per second, greater fixation duration and less time spent fixating on obstacles (p<0.001). In addition, participants adopted more cautious gait patterns during the secondary search task, exhibiting a 12% decrease in walking velocity and 8% decrease in stride length (p<0.05). Importantly, obstacle errors did not increase with the inclusion of the search task. Fixation durations also increased by 7% with the inclusion of the search task, along with a reduction in percent of time spent fixating on obstacles (by 9%) (p<0.05).
These findings suggest that mobility performance is enhanced when more saccadic and scanning eye movements patterns (fewer fixations per second and shorter fixation durations) are adopted. In addition, the adaptive gait changes in the presence of a secondary search task appear to be an appropriate compensatory strategy to minimize obstacle contact in unfamiliar, challenging real-world environments.
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