title: Dynamic visual acuity (DVA) during locomotion for targets at near and far distances: effects of aging, walking speed and head-trunk coupling.
abstract: This study examined effects of aging, head-trunk coupling (HTcoupling) and walking speed on dynamic visual acuity (DVA) at near and far viewing distances. Ten healthy participants were recruited in 3 groups; young: 20-33 years, Older1: 65-74 years, Older2: 75-85 years. The binocular DVA was measured while walking on a treadmill at 0.75 and 1.5 m/s speeds. The optotype display was placed at 0.5 m for NearDVA and at 3.0 m for FarDVA. On randomly selected trials, HTcoupling was achieved by using a collar. A mix-factor ANOVA (age-group x HTcoupling x speed) was performed separately for the Near and FarDVA. NearDVA declined with HTcoupling (p=0.021). Additionally, NearDVA worsened at the faster speed (p< 0.001). At 1.5 m/s speed the differences between Young and Older2 groups were significant (p=0.012) and those between Older1 and Older2 were marginal (p=0.085). FarDVA declined at the faster speed (p< 0.001) with no effect of HTcoupling or age-group. NearDVA is more sensitive to normal aging process. These age-related deficits become more apparent at higher walking speeds. Effect of HTcoupling on NearDVA suggests a possible additive effect of insufficient dampening of the vertical movement of the overall head-trunk complex and inability of the linear vestibulo-ocular reflex to compensate for the consequent high discrepancy.
authors.affiliation: School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada.
authors.forename: Nandini
authors.initials: N
authors.lastname: Deshpande
authors.forename: Brandon M
authors.initials: BM
authors.lastname: Tourtillott
authors.forename: Brian T
authors.initials: BT
authors.lastname: Peters
authors.forename: Jacob J
authors.initials: JJ
authors.lastname: Bloomberg
mesh_terms: D000054:Acceleration; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D004215:Distance Perception / Q000502:physiology*; D005260:Female; D006257:Head; D019416:Head Movements; D006801:Humans; D008124:Locomotion / Q000502:physiology*; D008297:Male; D009068:Movement / Q000502:physiology*; D010037:Otolithic Membrane / Q000502:physiology; D012027:Reflex, Vestibulo-Ocular / Q000502:physiology*; D013909:Thorax; D014724:Vestibular Function Tests; D014792:Visual Acuity / Q000502:physiology*; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Dynamic visual acuity; aging; locomotion; vestibulo-occular reflex