title: The proximity-fixation-disparity curve and the preferred viewing distance at a visual display as an indicator of near vision fatigue.
abstract: OBJECTIVE
  This laboratory study investigates the relation between measures of fixation disparity (FD) (and other optometric measures) and near vision fatigue at a computer workstation.
  
  
  METHODS
  Young adult subjects with normal binocular vision performed three blocks of a visual task of 30 min each. In Block A, the viewing distance was 100 cm, as a reference without near vision. In Block B, the viewing distance of 50 cm induced a defined near vision load. In Block C, subjects were free to choose a comfortable viewing distance. This preferred viewing distance was used as an indicator of near vision fatigue because subjects adopting longer viewing distances in Block C had more near vision fatigue at 50 cm in Block B.
  
  
  RESULTS
  Subjects with preferred viewing distances longer than average (63 cm) had steeper slopes of FD as a function of viewing distance (100-30 cm), as shown by discriminant analyses.
  
  
  CONCLUSIONS
  Thus, this steep proximity-FD curve indicates a weak disparity vergence system that may cause near vision fatigue. This may explain why some young adults prefer longer viewing distances at the computer workstation.
authors.affiliation: Institut für Arbeitsphysiologie, Dortmund, Germany. jaschinski@arb-phys.uni-dortmund.de
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jaschinski
mesh_terms: D016288:Computer Terminals; D003626:Data Display; D004215:Distance Perception; D005221:Fatigue / Q000209:etiology* / Q000503:physiopathology*; D005403:Fixation, Ocular; D006801:Humans; D009907:Optometry / Q000379:methods; D014786:Vision Disorders / Q000209:etiology* / Q000503:physiopathology*