The impact patterns of classroom lighting parameters on visual fatigue and a mathematical model

In the classroom, visual fatigue resulting from unfavorable non-visual impacts will diminish learning efficiency and affect eye health. To maintain the quality of the classroom lighting environment, it is crucial to set a combination of lighting parameters that minimizes visual fatigue. However, describing lighting quality traditionally by combining illuminance and color temperature fail in intuitively expressing the complexity of the lighting environment in the human visual field. For this reason, this study introduced the idea of luminance gradients and defined 20 lighting parameters for classroom lighting based on luminance and correlated color temperature (CCT). Using the experimental method of combining a subjective questionnaire survey with a critical flicker-fusion frequency test, four parameters with a significant impact on the comprehensive index of visual fatigue (VF) out of the 20 lighting parameters are extracted, i.e., directional luminance gradients (D31 and D12), the mean value of luminance (Lm), and CCT. Based on the findings of the impact of four lighting parameters on visual fatigue, an optimal range of lighting parameters conducive to reducing visual fatigue was established. Additionally, a mathematical model for predicting visual fatigue (VF) was developed as VF = g (D31, D12, Lm, CCT), providing a quantitative tool for evaluating and improving classroom lighting quality.