Supporting the development of inclusive products: the effects of everyday ambient illumination levels and contrast on older adults’ near visual acuity

摘要

Current older adult capability datasets fail to account for the effects of everyday environmental conditions on capability. This paper details a study which investigates the effects of everyday ambient illumination conditions (overcast, 6000 lx; In-house lighting, 150 lx; and street lighting, 7.5 lx) and contrast (90%, 70%, 50% and 30% contrast) on the near visual acuity of older adults (n=38, 65-87 years). Visual acuity was measured at a one metre viewing distance using LogMAR acuity charts. Results from the study showed that for all contrast levels tested, visual acuity decreased by 0.2 log units between the overcast and street lighting conditions. On average, participants could detect detail around 1.6 times smaller on the LogMAR charts when under overcast conditions compared to street lighting. Visual acuity also significantly decreased when contrast was reduced from 70% to 50%, and from 50% to 30% in each of the ambient illumination conditions.