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Stepping Up to a New Level: Effects of Blurring Vision in the Elderly

¹From the Department of Optometry, ²Institute of Health Research, School of Health, and ³School of Engineering, Design and Technology, University of Bradford, Bradford, United Kingdom.

PURPOSE. To determine the effects of blurring vision on whole-body center-of-mass (CM) dynamics and foot-clearance parameters in elderly individuals performing a single step up to a new level.

METHODS. Twelve healthy subjects (mean age, 72.3 ±4.17 years) performed a single step up to a new level (heights of 73 and 146 mm). Trials were undertaken with vision optimally corrected and with vision diffusively blurred by light-scattering lenses (cataract simulation). CM and foot-clearance parameter data were assessed by analyzing data collected by a five-camera, three-dimensional (3-D) motion analysis system.

RESULTS. When vision was blurred, subjects took 11% longer to execute the stepping task (P < 0.05), mediolateral displacement of the point of application of the ground reaction force vector (i.e., weighted average of all pressures over the area in contact with the ground; the so called center of pressure, CP) decreased from 37.6% of stance width to 28.3% (P < 0.01), maximum distance between the mediolateral position of the CM and CP decreased by 9.8 mm (P < 0.01), and toe clearance (distance between tip of shoe and edge of step) increased in both the horizontal (28%) and vertical (19%) direction (P < 0.05).

CONCLUSIONS. These findings suggest that when vision was blurred, subjects used a twofold safety-driven adaptation: First, to increase dynamic stability they ensured that the horizontal position of their CM was kept close to the center of the base of support and second, they increased horizontal and vertical toe clearance while swinging their lead limb forward to reduce the risk of tripping.

This article has been cited by other articles:

				L. Johnson, J. G. Buckley, A. J. Scally, and D. B. Elliott Multifocal Spectacles Increase Variability in Toe Clearance and Risk of Tripping in the Elderly Invest. Ophthalmol. Vis. Sci., April 1, 2007; 48(4): 1466 - 1471. [Abstract] [Full Text] [PDF]

				G. L. Onambele, M. V. Narici, and C. N. Maganaris Calf muscle-tendon properties and postural balance in old age J Appl Physiol, June 1, 2006; 100(6): 2048 - 2056. [Abstract] [Full Text] [PDF]

				K. Heasley, J. G. Buckley, A. Scally, P. Twigg, and D. B. Elliott Falls in Older People: Effects of Age and Blurring Vision on the Dynamics of Stepping Invest. Ophthalmol. Vis. Sci., October 1, 2005; 46(10): 3584 - 3588. [Abstract] [Full Text] [PDF]