title: Gait alterations negotiating a raised surface induced by monocular blur.
abstract: OBJECTIVE
  Falls in the elderly are a major cause of serious injury and mortality. Impaired and absent stereopsis may be a significant risk factor for falls or hip fracture, although data from epidemiological studies are not consistent. Previous laboratory based studies, however, do suggest that stereoacuity is an important factor in adaptive gait. The present study investigates how acute impairment of stereopsis, through monocular blur of differing levels, ranging from 0.50 diopter (D) to a monovision correction affected gait when negotiating a raised surface in elderly subjects.
  
  
  METHODS
  Eleven elderly subjects (73.3 +/- 3.6 years) walked up to and negotiated a raised surface under nine visual conditions, binocular vision, one eye occluded and 0.50 D, 1.00 D and monovision correction (mean 2.50 D +/- 0.20 D) with blur and occlusion either over the dominant or non-dominant eye. Analysis focused on foot positioning and toe clearance parameters.
  
  
  RESULTS
  There was no effect of ocular dominance on any parameters. Monocular blur impaired stereopsis (p < 0.01), with more minor effects on high and low contrast acuity. Vertical and horizontal lead limb toe clearance both increased under all levels of monocular blur including the lowest level of 0.50 DBlur (p = 0.03) and monovision correction led to toe clearance levels similar to that found with occlusion of one eye.
  
  
  CONCLUSIONS
  Findings demonstrated that even small amounts of monocular blur can lead to a change in gait when negotiating a raised surface, suggesting acute monocular blur affected the ability to accurately judge the height of a step in the travel path. Further work is required to investigate if similar adaptations are used by patients with chronic monocular blur.
authors.affiliation: Department of Optometry, Division of Medical Engineering, School of Engineering, Design and Technology (JGB), University of Bradford, Bradford, United Kingdom. a.vale@bradford.ac.uk
authors.forename: Anna
authors.initials: A
authors.lastname: Vale
authors.forename: John G
authors.initials: JG
authors.lastname: Buckley
authors.forename: David B
authors.initials: DB
authors.lastname: Elliott
mesh_terms: D000058:Accidental Falls / Q000706:statistics & numerical data; D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity; D003867:Depth Perception / Q000502:physiology*; D005260:Female; D005528:Foot / Q000502:physiology; D005684:Gait; D006620:Hip Fractures / Q000453:epidemiology; D006801:Humans; D008297:Male; D009039:Motion Perception; D012307:Risk Factors; D014786:Vision Disorders / Q000453:epidemiology; D015348:Vision, Binocular / Q000502:physiology*; D015349:Vision, Monocular / Q000502:physiology*; D014792:Visual Acuity / Q000502:physiology*; D016138:Walking