Abstract
Purpose :
Older adults report difficulties performing daily activities, such as walking and stepping, under low light levels, particularly those with age-related macular degeneration (AMD). This study explored the effect of low light levels and target contrast on precision stepping accuracy in older adults with and without AMD.
Methods :
Twenty-four older adults (12 AMD and 12 controls, aged over 65 years) walked along a 14-m level walkway containing stepping and distractor targets (10 each, 15x15cm). Participants stepped as closely as possible to the middle of stepping targets and avoided distractor targets. Stepping tasks were performed under three light levels (photopic, 440lx; 2 levels of mesopic, 10 and 3lx) and two stepping target contrasts (high 89% and low 54%). Foot placement during stepping was recorded using leg mounted cameras. Custom software determined anteroposterior (AP) and mediolateral (ML) stepping errors for each step (ball of foot to target centre), as well as absolute error (Euclidean distance).
Results :
For absolute stepping errors, there were significant effects of group (p=0.004), light (p<0.001) and a significant group*light interaction (p=0.015), but no effect of contrast (p=0.14) (Figure). Controls showed similar errors under all light levels (p=0.99) but the AMD group had greater errors overall, and more errors under mesopic conditions compared to photopic (p<0.001). For both ML and AP stepping errors, there were significant effects of light (p≤0.008) but no group effect (p≥0.13); all participants stepped more laterally and posteriorly under low mesopic compared to photopic conditions. Target contrast had a significant effect on ML (p=0.007) but not AP stepping errors (p=0.48); all participants stepped more laterally for low compared to high contrast targets. There was a significant light*contrast interaction for AP (p=0.019) stepping errors; all participants stepped posteriorly for low compared to high contrast targets under photopic conditions.
Conclusions :
Reduced light levels and lower contrast stepping targets negatively impacted stepping accuracy. Findings have implications for enhancing environmental design, including lighting and contrast, to promote safe mobility and minimise falls risk, particularly in older adults with AMD.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.