title: Differential effects of refractive blur on day and nighttime driving performance.
abstract: OBJECTIVE
  To investigate the effect of different levels of refractive blur on real-world driving performance measured under day and nighttime conditions.
  
  
  METHODS
  Participants included 12 visually normal, young adults (mean age = 25.8 ± 5.2 years) who drove an instrumented research vehicle around a 4 km closed road circuit with three different levels of binocular spherical refractive blur (+0.50 diopter sphere [DS], +1.00 DS, +2.00 DS) compared with a baseline condition. The subjects wore optimal spherocylinder correction and the additional blur lenses were mounted in modified full-field goggles; the order of testing of the blur conditions was randomized. Driving performance was assessed in two different sessions under day and nighttime conditions and included measures of road signs recognized, hazard detection and avoidance, gap detection, lane-keeping, sign recognition distance, speed, and time to complete the course.
  
  
  RESULTS
  Refractive blur and time of day had significant effects on driving performance (P < 0.05), where increasing blur and nighttime driving reduced performance on all driving tasks except gap judgment and lane keeping. There was also a significant interaction between blur and time of day (P < 0.05), such that the effects of blur were exacerbated under nighttime driving conditions; performance differences were evident even for +0.50 DS blur relative to baseline for some measures.
  
  
  CONCLUSIONS
  The effects of blur were greatest under nighttime conditions, even for levels of binocular refractive blur as low as +0.50 DS. These results emphasize the importance of accurate and up-to-date refractive correction of even low levels of refractive error when driving at night.
authors.affiliation: School of Optometry and Vision Science and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Wood
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Collins
authors.forename: Alex
authors.initials: A
authors.lastname: Chaparro
authors.forename: Ralph
authors.initials: R
authors.lastname: Marszalek
authors.forename: Trent
authors.initials: T
authors.lastname: Carberry
authors.forename: Philippe
authors.initials: P
authors.lastname: Lacherez
authors.forename: Byoung Sun
authors.initials: BS
authors.lastname: Chu
mesh_terms: D000221:Adaptation, Ocular / Q000502:physiology*; D000293:Adolescent; D000328:Adult; D001334:Automobile Driving; D003624:Darkness; D005260:Female; D006801:Humans; D008297:Male; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology*; D014787:Vision Tests; D014792:Visual Acuity; D055815:Young Adult
keywords: driving; nighttime; refractive blur