In most sensitive occupations such as nuclear, military and chemical industries closed circuit systems and visualuddisplay terminals (VDTs) are used to carefully control and assess sensitive processes. Visual fatigue is one of theudfactors decreasing accuracy and concentration in operators causing faulty perception. This study aimed to findudout a relationship between visual fatigue symptoms (VFS) of Flicker value variations in video display terminalud(VDT) operators.udThis cross-sectional study, conducted in 2011, aimed to examine visual fatigue and determine the relationshipudbetween its symptoms and visual flicker value changes in 248 operators of VDTs in several occupations. Theudmaterials used in this study were a visual fatigue questionnaire of VDTs and a VFM-90.1 device. Visual fatigueudwas measured in two stages (prior to beginning to work and 60 min later). The data were analyzed by SPSS11.5,udusing descriptive statistics, paired t-test, simple and multiple linear regressions, correlation and recognitionudcoefficients. Then regression equations of changes in flicker value depending on the changes in the mainuddomains and the changes in final score before the questionnaire were obtained.udPaired t-test indicated significant differences in the mean score of visual fatigue symptoms and the mean score ofudflicker value between the two stages, respectively (P ≤ 0.001). Simple and multiple regressions of flicker valueudvariations, for the last visual fatigue changes in questionnaire score and the four main domains of theudquestionnaire were obtained R2 = 0.851 and R2 = 0.853, respectively. Correlation coefficient in the above testsudindicated reverse and significant relationships among flicker value changes with changes in questionnaire scoreudand visual fatigue symptoms.udDiagnosing the first symptoms of visual fatigue could be an appropriate warning for VDTs operators in sensitiveudoccupations to react suitably, in behavior and management, to control or treat visual fatigue and prevent errorsudefficiently.
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