title: Effect of ambient light and age-related macular degeneration on precision walking.
abstract: OBJECTIVE
  To determine how age-related macular degeneration (AMD) and changes in ambient light affect the control of foot placement while walking.
  
  
  METHODS
  Ten older adults with AMD and 11 normal-sighted controls performed a precision walking task under normal (∼600 lx), dim (∼0.7 lx), and after a sudden reduction (∼600 to 0.7 lx) of light. The precision walking task involved subjects walking and stepping to the center of a series of irregularly spaced, low-contrast targets. Habitual visual acuity and contrast sensitivity and visual field function were also assessed.
  
  
  RESULTS
  There were no differences between groups when performing the walking task in normal light (p > 0.05). In reduced lighting, older adults with AMD were less accurate and more variable when stepping across the targets compared to controls (p < 0.05). A sudden reduction of light proved the most challenging for this population. In the AMD group, contrast sensitivity and visual acuity were not significantly correlated with walking performance. Visual field thresholds in the AMD group were only associated with greater foot placement error and variability in the dim light walking condition (r = -0.69 to -0.87, p < 0.05).
  
  
  CONCLUSIONS
  While walking performance is similar between groups in normal light, poor ambient lighting results in decreased foot placement accuracy in older adults with AMD. Improper foot placement while walking can lead to a fall and possible injury. Thus, to improve the mobility of those with AMD, strategies to enhance the environment in reduced lighting situations are necessary.
authors.affiliation: *MSc †PhD ‡MD, FRCSC §OD, PhD, FAAO Department of Biomedical Physiology and Kinesiology (MSA, KL, RAS, SNR, DSM), School of Engineering Science (SNR), Simon Fraser University, Burnaby; and Private Practice, New Westminster (DRN), British Columbia, Canada.
authors.forename: M Scott
authors.initials: MS
authors.lastname: Alexander
authors.forename: Kim
authors.initials: K
authors.lastname: Lajoie
authors.forename: David R
authors.initials: DR
authors.lastname: Neima
authors.forename: Robert A
authors.initials: RA
authors.lastname: Strath
authors.forename: Stephen N
authors.initials: SN
authors.lastname: Robinovitch
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Marigold
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015350:Contrast Sensitivity / Q000502:physiology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008027:Light; D008268:Macular Degeneration / Q000503:physiopathology*; D008297:Male; D011597:Psychomotor Performance / Q000502:physiology*; D011788:Quality of Life; D015354:Vision, Low / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology; D014794:Visual Fields / Q000502:physiology; D019987:Persons with Visual Disabilities; D016138:Walking / Q000502:physiology*