Development and Validation of a Visual Fatigue Questionnaire for Video Display Terminal Users

Technology- related tools, including computers and video display terminals (VDTs), are rapidly expanding as a result of the quick growth of technology itself. Investigation on the complaints of VDT users reported visual discomfort. This study aimed to design an appropriate tool to assess visual fatigue of VDT users. This cross-sectional study was performed on 248 VDT users in different professions during 2011. After reading books, articles, and similar questionnaires, question banks were provided and an initial questionnaire was developed. Validity and reliability of the questionnaire were evaluated by Cronbach's alpha coefficient and content validity index (CVI). A theoretical model based on four categories of symptoms of visual fatigue, extracted from previous studies, was designed. AMOS software was used to assess the validity of its constructs using confirmatory factor analysis and fitted parameters. Using the SPSS18, internal correlation coefficients of the domains were calculated. In order to investigate the reliability and grade the final scores of the questionnaire, visual fatigue was simultaneously assessed by the questionnaire and the VFM-90.1 device and the results were compared. In addition, cutting points were determined by the ROC curve. A minimum CVI of 0.75, reliability coefficient of 0.755, model fit indices of RMSEA = 0.026, GFI = 0.96 and AGFI = 0.92 were found. The correlation between the results measured with a questionnaire and VFM-90.1 was -0.87 and the cut-off points were calculated as 0.65, 2.36 and 3.88. Four main domains of the questionnaire, including eye strain (4 questions), visual impairment (5 questions), surface-related impairments of the eye (3 questions) and problems outside the eye (3 questions), were approved. The questionnaire contained 15 questions to assess visual fatigue. It had excellent reliability and validity. Therefore, VDT users can easily assess their extent and level of visual fatigue by this relatively short and simple questionnaire.