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VK Anand, DB Elliott; Postural Sway Changes in Elderly Subjects Due to Disruption of the Somatosensory and Vestibular System Inputs, Refractive Blur and Dual Tasking . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3826.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine the effect of disruption of the inputs from the somatosensory and vestibular systems, refractive blur and dual tasking on postural sway in healthy, elderly subjects. Methods: Fifteen healthy, elderly subjects (mean age 71 ± 5 years, binocular VA -0.07 ± 0.05 logMAR, Snellen 20/17) with no history of falls and normal vision were recruited. Balance control was assessed under normal standing conditions using an AMTI force plate. Postural sway was determined as the RMS of the Centre of Pressure (COP) signal in the anterior-posterior (AP) and medial-lateral (ML) directions collected over 30 second periods. Data were collected under normal standing conditions and when the input from the somatosensory and vestibular systems were disrupted. Three measurement conditions were also repeated with the subject being given an additional physical task (holding a tray of cups) and/or mental task (counting backwards). For all measurement conditions, postural sway was measured under conditions of binocular refractive blur of 0,1, 2, 4 and 8D and with eyes closed. Results: All factors significantly increased postural sway (p<0.001). The greatest increases in postural sway were due to disruption of the somatosensory system (95% AP increase) and disruption of both the somatosensory and vestibular systems (152% AP increase). Increasing refractive blur caused increasing postural sway, with 8D blur causing a 44% increase in AP sway under normal standing conditions. The effect of refractive blur was greater when the input from the other sensory systems was disrupted (81% increase in AP sway with 8D blur). Performing an additional mental and physical task increased AP sway by approximately 24%. All these detrimental effects on balance control were additive. Conclusion: All the factors tested significantly increased postural sway and were additive. This highlights the multifactorial nature of balance control. The visual system becomes increasingly relied upon when input from the other two balance control systems, and particularly the somatosensory system, are disrupted.
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