title: Adaptive gait changes in long-term wearers of contact lens monovision correction.
abstract: BACKGROUND
  The aim of the present study was to determine adaptive gait changes in long-term wearers of monovision correction contact lenses by comparing gait parameters when wearing monovision correction to those observed when wearing binocular distance correction contact lenses.
  
  
  METHODS
  Gait and toe clearance parameters were measured in eleven participants (53.5 +/- 4.6 years, median monovision wearing time 5 years) as they repeatedly walked up to and onto a raised surface with either monovision or distance correction.
  
  
  RESULTS
  Compared to distance correction, monovision resulted in a large reduction in stereoacuity from 17'' to 87'', a slower walking velocity (p = 0.001), a reduced horizontal toe clearance of the step edge (p = 0.035) and, for trials when monovision correction occurred first, a 33% greater variability in vertical toe clearance (p = 0.021). Variability in some gait data was large due to certain study design features and learning effects.
  
  
  CONCLUSIONS
  A slower walking velocity with monovision correction suggests participants became more cautious, likely as a result of the significantly reduced stereoacuity. The decreased horizontal toe clearance and increased vertical toe clearance variability suggests that monovision correction may cause a greater likelihood of hitting step edges and tripping during everyday gait. Recommended study design features are suggested for future adaptive gait studies to increase the precision of the data and to attempt to minimize the effects of learning from somatosensory feedback.
authors.affiliation: Bradford School of Optometry and Vision Science, University of Bradford, Bradford, West Yorkshire, UK.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Chapman
authors.forename: Anna
authors.initials: A
authors.lastname: Vale
authors.forename: John
authors.initials: J
authors.lastname: Buckley
authors.forename: Andy J
authors.initials: AJ
authors.lastname: Scally
authors.forename: David B
authors.initials: DB
authors.lastname: Elliott
mesh_terms: D003261:Contact Lenses; D003867:Depth Perception / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011305:Presbyopia / Q000503:physiopathology* / Q000628:therapy*; D013997:Time Factors; D015349:Vision, Monocular; D014792:Visual Acuity / Q000502:physiology; D016138:Walking / Q000502:physiology