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Background and aims: In the majority of sensitive occupations, such as nuclear, military, chemical, etc, closed circuit systems and visual displays terminals (VDTs) are used to control and monitor sensitive processes. Visual fatigue is one of the factors that decreases operators' precision and awareness and makes the reception of visual data from VDT erroneous. This study was aimed to exanimate the association of visual fatigue symptoms with flicker value changes in video display terminals operators. Methods: This cross-sectional study in 248 operators of VDTs in several occupations was conducted in 2011. The instruments that have been used in this study were a visual fatigue questionnaire of VDTs and a VFM-90.1 device. Visual fatigue was measured in two stages (prior to beginning to work and 60 min later). The data were analyzed using descriptive statistics, paired t-test, simple and multiple linear regressions. Results: Paired t-test indicated significant differences in the mean score of visual fatigue symptoms and the mean score of flicker value between two stages respectively (P< 0.001). Simple and multiple regressions were obtained for the last visual fatigue changes in questionnaire score (R² = 0.853) and the four main domains of the questionnaire (R²= 0.851). Correlation coefficient in the above testes indicated on inverse and significant association of flicker value changes with changes in questionnaire score and visual fatigue symptoms. Conclusion: diagnosing the first symptoms of visual fatigue could be an appropriate warning for VDTs operators in sensitive occupations to react suitably, in behavior and management, to control or treat visual fatigue and prevent errors efficiently. [ABSTRACT FROM AUTHOR]