title: Relationships between feature search and mobility performance in persons with severe visual impairment.
abstract: OBJECTIVE
  Because visual search requires both the ability to discriminate visual features and the ability to process information in a large field of view, the association between feature search and mobility of visually impaired (VI) subjects was studied.
  
  
  METHODS
  Forty-four subjects with severe visual impairment participated in the study. Feature search performance (2 x 2 deg square target amid 1 x 1 deg square distracters) was measured for 8- to 16- and 32-item set-sizes on 10 x 10, 20 x 20, and 40 x 40 deg fields. Mobility was evaluated on indoor high-density obstacle courses under photopic and mesopic illumination.
  
  
  RESULTS
  In feature search, VI subjects were slower and made more errors than normal subjects, but they searched in a parallel fashion. On the mobility task, VI subjects walked slower and made more obstacle contacts than age-matched normal controls. In VI subjects, performances on feature search and mobility tasks were significantly associated, with 37.5% to 66.9 of variations in the mobility measurements being accounted for by visual search speed.
  
  
  CONCLUSIONS
  Feature search reaction time can be a good predictor of VI patients' mobility.
authors.affiliation: Birmingham VA Medical Center, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA. patti.fuhr@va.gov
authors.forename: Patti S
authors.initials: PS
authors.lastname: Fuhr
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Thomas K
authors.initials: TK
authors.lastname: Kuyk
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005106:Exploratory Behavior; D006801:Humans; D008875:Middle Aged; D011237:Predictive Value of Tests; D011930:Reaction Time; D012720:Severity of Illness Index; D014786:Vision Disorders / Q000503:physiopathology* / Q000523:psychology*; D014796:Visual Perception; D016138:Walking