title: Using diplopia as a warning of an inappropriate visual (ocular) accommodative response (WIVAR).
abstract: BACKGROUND
  Over-accommodation, a tendency to focus at a distance closer than the desired distance, has been previously shown to occur when using a head-up display (HUD).
  
  
  METHODS
  A simple system was developed as a warning of an inappropriate visual accommodative response (WIVAR) during flight training. Two lines, which are seen as four low-contrast lines (physiological diplopia) if the user is focused in the distance due to the link between convergence and accommodation, are projected onto the pilot's HUD combiner.
  
  
  RESULTS
  The results show that by using the WIVAR system the accommodative response can be kept more distant when viewing forward-looking infra-red imagery (by 0.12 +/- 0.04 D; p < 0.05), performing a high cognitive workload task (by 0.07 +/- 0.03 D; p < 0.05) and especially when viewing in a Ganzfeld (by 0.41 +/- 0.12 D; p < 0.01).
  
  
  CONCLUSIONS
  While collimated HUD imagery stimulates the user to a more distant focus, the use of the WIVAR lines can cause additional relaxation of accommodation.
authors.affiliation: Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria, Australia.
authors.forename: J S
authors.initials: JS
authors.lastname: Wolffsohn
authors.forename: G K
authors.initials: GK
authors.lastname: Edgar
authors.forename: N A
authors.initials: NA
authors.lastname: McBrien
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D000337:Aerospace Medicine; D000704:Analysis of Variance; D001359:Aviation / Q000193:education*; D004172:Diplopia / Q000175:diagnosis / Q000503:physiopathology*; D005128:Eye Diseases / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male