title: Comparison of progressive addition lenses for general purpose and for computer vision: an office field study.
abstract: BACKGROUND
  Two types of progressive addition lenses (PALs) were compared in an office field study: 1. General purpose PALs with continuous clear vision between infinity and near reading distances and 2. Computer vision PALs with a wider zone of clear vision at the monitor and in near vision but no clear distance vision.
  
  
  METHODS
  Twenty-three presbyopic participants wore each type of lens for two weeks in a double-masked four-week quasi-experimental procedure that included an adaptation phase (Weeks 1 and 2) and a test phase (Weeks 3 and 4). Questionnaires on visual and musculoskeletal conditions as well as preferences regarding the type of lenses were administered. After eight more weeks of free use of the spectacles, the preferences were assessed again. The ergonomic conditions were analysed from photographs.
  
  
  RESULTS
  Head inclination when looking at the monitor was significantly lower by 2.3 degrees with the computer vision PALs than with the general purpose PALs. Vision at the monitor was judged significantly better with computer PALs, while distance vision was judged better with general purpose PALs; however, the reported advantage of computer vision PALs differed in extent between participants. Accordingly, 61 per cent of the participants preferred the computer vision PALs, when asked without information about lens design. After full information about lens characteristics and additional eight weeks of free spectacle use, 44 per cent preferred the computer vision PALs.
  
  
  CONCLUSIONS
  On average, computer vision PALs were rated significantly better with respect to vision at the monitor during the experimental part of the study. In the final forced-choice ratings, approximately half of the participants preferred either the computer vision PAL or the general purpose PAL. Individual factors seem to play a role in this preference and in the rated advantage of computer vision PALs.
authors.affiliation: Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Jaschinski
authors.affiliation: Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany.
authors.forename: Mirjam
authors.initials: M
authors.lastname: König
authors.affiliation: Leibniz Research Center for Working Environment and Human Factors, Dortmund, Germany.
authors.forename: Tiofil M
authors.initials: TM
authors.lastname: Mekontso
authors.affiliation: ZEISS Vision Science Lab, Carl Zeiss Vision International GmbH, Tübingen, Germany.
authors.forename: Arne
authors.initials: A
authors.lastname: Ohlendorf
authors.affiliation: Technology & Innovation, Carl Zeiss Vision GmbH, Aalen, Germany. jaschinski@ifado.de.
authors.forename: Monique
authors.initials: M
authors.lastname: Welscher
mesh_terms: D000328:Adult; D003201:Computers; D004867:Equipment Design; D005139:Eyeglasses; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000628:therapy*; D011305:Presbyopia / Q000503:physiopathology / Q000628:therapy*; D011795:Surveys and Questionnaires; D014792:Visual Acuity
keywords: computer work; presbyopia; progressive lenses; spectacle lenses