title: Self-reported importance and difficulty of driving in a low-vision clinic population.
abstract: OBJECTIVE
  To validate estimates of self-perceived driving ability from difficulty ratings of driving tasks and to determine the association of the importance and difficulty of driving with the magnitude of visual impairments.
  
  
  METHODS
  A consecutive series of 851 patients at a low-vision clinic rated the importance of driving on a four-point scale. Those who gave nonzero importance ratings then rated driving difficulty on a five-point scale. Those who gave nonzero difficulty ratings then rated the difficulty of each of 21 driving tasks on a five-point scale. Visual acuity was measured with the Early Treatment of Diabetic Retinopathy Study (ETDRS) chart, and contrast sensitivity was measured with the Pelli-Robson chart. Rasch analysis was used to test the validity and reliability of self-perceived driving ability estimates from difficulty ratings of tasks.
  
  
  RESULTS
  Patients who rated driving as not important (41%) had worse visual acuity (logMAR = 0.88) and worse contrast sensitivity (log CS = 0.83) than did those who rated driving as extremely important (55%; logMAR = 0.62; log CS =1.03; multivariate analysis of variance [MANOVA]; P = 0.003). Self-perceived driving ability correlated negatively with the overall rating of driving difficulty (r = -0.69; P < 0.001) and with logMAR (r = -0.28; P < 0.001), and correlated positively with log CS (r = 0.35; P < 0.001). The most difficult driving tasks were navigating in parking ramps, parking in the correct space, seeing lane markings, and reading signs. The least-difficult driving tasks were seeing traffic and reading the speedometer. Rasch analysis confirmed instrument validity and reliability.
  
  
  CONCLUSIONS
  Low-vision patients appeared to devalue the goal of driving when visual impairments were more severe. Valid measures of self-perceived driving ability can be estimated from difficulty ratings of specific driving tasks.
authors.affiliation: Lions Vision Research and Rehabilitation Center, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. rmassof@lions.med.jhu.edu
authors.forename: Robert W
authors.initials: RW
authors.lastname: Massof
authors.forename: James T
authors.initials: JT
authors.lastname: Deremeik
authors.forename: William L
authors.initials: WL
authors.lastname: Park
authors.forename: Lori L
authors.initials: LL
authors.lastname: Grover
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001334:Automobile Driving; D015350:Contrast Sensitivity / Q000502:physiology*; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012650:Self Disclosure; D011795:Surveys and Questionnaires; D015354:Vision, Low / Q000503:physiopathology* / Q000534:rehabilitation; D014792:Visual Acuity / Q000502:physiology*