Affiliations: [a] School of Rehabilitation Therapy, Queen's University, Kingston, ON, Canada | [b] F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA | [c] Human Performance and Engineering Division, Science, Technology and Engineering Group, Wyle, Houston, TX, USA | [d] Neuroscience Laboratories, NASA/Johnson Space Center, Houston, TX, USA
Correspondence:
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Corresponding author: Nandini Deshpande, Louise D Acton Building, 31 George Street, Queen's University, Kingston, ON, K7L 3N6, Canada. E-mail: nandinijd@yahoo.com
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.
