Older people contact more obstacles when wearing multifocal glasses and performing a secondary visual task

OBJECTIVES: To determine whether wearing multifocal glasses affects obstacle avoidance and eye and head movements during walking with and without a secondary visual task in older people. DESIGN: Randomized order, cross-over, controlled comparison. SETTING: Falls laboratory, medical research institute. PARTICIPANTS: Thirty community-living adults aged 65 and older. MEASUREMENTS: Obstacle contacts, secondary-task errors, average head angle (HA) in pitch, and peak-to-peak pitch amplitude of the eye (PA-E) and the head (PA-H) were assessed during obstacle-only and dual-task trials that required participants to read a series of letters presented in front of them at eye level under multifocal and single-lens glasses conditions. RESULTS: When wearing multifocal lens glasses, participants performed the obstacle-only trials more slowly (P=.004) and contacted more obstacles in the dual-task trials (P=.001) than when wearing single-lens glasses. For the dual task trials under the multifocal glasses condition, greater PA-E was associated with more obstacle contacts (ρ=0.409, P=.02) and greater PA-H was associated with more secondary-task errors (ρ=0.583 P=.002). Lower HA was associated with more secondary-task errors (ρ=0.608, P=.002) and increased PA-H (ρ=0.426, P=.02). CONCLUSION: The findings demonstrate that older adults contact more obstacles while walking with their attention divided when wearing multifocal glasses. This is probably because of a failure to adopt a compensatory increase in pitch head movement, resulting in blurred vision of obstacles viewed through the lower segments of multifocal glasses.