title: Designing and validation a visual fatigue questionnaire for video display terminals operators.
abstract: BACKGROUND
  Along with the rapid growth of technology its related tools such as computer, monitors and video display terminals (VDTs) grow as well. Based on the studies, the most common complaint reported is of the VDT users.
  
  
  METHODS
  This study attempts to design a proper tool to assess the visual fatigue of the VDT users. First draft of the questionnaire was prepared after a thorough study on the books, papers and similar questionnaires. The validity and reliability of the questionnaire was confirmed using the content validity index (CVI) beside that of the Cronbach's Coefficient Alpha. Then, a cross-sectional study was carried out on 248 of the VDT users in different professions. A theoretical model with four categories of symptoms of visual fatigue was derived from the previous studies and questionnaires. Having used the AMOS16 software, the construct validity of the questionnaire was evaluated using the confirmatory factor analysis. The correlation co-efficiency of the internal domains was calculated using the SPSS 11.5 software. To assess the quality check index and determining the visual fatigue levels, visual fatigue of the VDT users was measured by the questionnaire and visual fatigue meter (VFM) device. Cut-off points were identified by receiver operating characteristic curves.
  
  
  RESULTS
  CVI and reliability co-efficiency were both equal to 0.75. Model fit indices including root mean of squared error approximation, goodness of fit index and adjusted goodness of fit index were obtained 0.026, 0.96 and 0.92 respectfully. The correlation between the results measured with the questionnaire and VFM-90.1 device was -0.87. Cut-off points of the questionnaire were 0.65, 2.36 and 3.88. The confirmed questionnaire consists of four main areas: Eye strain (4 questions), visual impairment (5 questions) and the surface impairment of the eye (3 questions) and the out of eye problems (3 questions).
  
  
  CONCLUSIONS
  The visual fatigue questionnaire contains 15 questions and has a very remarkable validity and reliability. Using this questionnaire and its findings, one will be able to identify, assess and finally prevent the effective factors of VDT users' visual fatigue.
authors.affiliation: Incubator Center of Health Technology, Shahrekord University of Medical Sciences, shahrekord, India.
authors.forename: Hassan
authors.initials: H
authors.lastname: Rajabi-Vardanjani
authors.affiliation: Department of Occupational Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, India.
authors.forename: Ehsanollah
authors.initials: E
authors.lastname: Habibi
authors.affiliation: Department of Occupational Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, India.
authors.forename: Siyamak
authors.initials: S
authors.lastname: Pourabdian
authors.affiliation: Department of Occupational Health Engineering, School of Health, Isfahan University of Medical Sciences, Isfahan, India.
authors.forename: Habibollah
authors.initials: H
authors.lastname: Dehghan
authors.affiliation: Department of Epidemiology and Statistics, School of Health, Isfahan University of Medical Sciences, Isfahan, India.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Maracy
keywords: Reliability; validity; visual display terminals; visual fatigue questionnaire
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