title: Use of single-vision distance spectacles improves landing control during step descent in well-adapted multifocal lens-wearers.
abstract: OBJECTIVE
  Epidemiologic research has shown that multifocal spectacle wearers (bifocal and progressive addition lenses [PALs]) are more than twice as likely to fall than are nonmultifocal spectacle wearers, with this risk further increasing when negotiating stairs. The present study investigated whether step and stair descent safety is improved by using single-vision distance lenses.
  
  
  METHODS
  From a stationary standing position on top of a block, 20 long-term multifocal wearers stepped down (from different block heights) onto a lower level wearing bifocal, progressive addition, or single-vision distance lenses.
  
  
  RESULTS
  Use of single-vision distance spectacles led to an increased single-limb support time, a reduced ankle and knee angle and vertical center-of-mass velocity at contact with the lower level, and a reduced ankle angular velocity and vertical center-of-mass velocity during initial landing (P < 0.03). These findings indicate that landing occurred in a more controlled manner when the subjects wore single-vision distance spectacles, rather than tending to "drop" onto the lower level as occurred when wearing bifocals or PALs.
  
  
  CONCLUSIONS
  Use of single-vision distance spectacles led to improvements in landing control, consistent with individuals' being more certain regarding the precise height of the lower floor level. This enhanced control was attributed to having a view of the foot, step edge, and immediate floor area that was not blurred, magnified, or doubled and that did not suffer from image jump or peripheral distortions. These findings provide further evidence that use of single-vision distance lenses in everyday locomotion may be advantageous for elderly multifocal wearers who have a high risk of falling.
authors.affiliation: Division of Medical Engineering, School of Engineering, Design, and Technology, University of Bradford, Bradford, UK.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Timmis
authors.forename: Louise
authors.initials: L
authors.lastname: Johnson
authors.forename: David B
authors.initials: DB
authors.lastname: Elliott
authors.forename: John G
authors.initials: JG
authors.lastname: Buckley
mesh_terms: D000058:Accidental Falls / Q000517:prevention & control; D000368:Aged; D000369:Aged, 80 and over; D005139:Eyeglasses; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009949:Orientation / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*; D011474:Prosthesis Design; D012307:Risk Factors; D015348:Vision, Binocular / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology