Objective To understand the visual environment sanitation in primary and secondary school classrooms in Minhang District， Shanghai， and to investigate the factors affecting the decline in students’ visual acuity.

Methods In 2020， among all the primary and secondary schools in Minhang District， according to different types of classroom structures， levels， orientations， unilateral lighting， and bilateral lighting， a total of 20 231 students from 674 classrooms in primary and secondary schools were selected through stratified cluster sampling. Each monitored classroom was regarded as a research unit， and the naked eye vision of students was tested using a standard logarithmic vision chart during the 2020 and 2021 academic years. The change in average visual acuity between the two measurements was taken as the dependent variable， and the visual environment indices were considered as independent variables. The relationship between classroom visual environment indices and the decline in students’ naked eye vision was analyzed.

Results The qualification rates for per capita classroom area， window to floor area ratio， average illuminance of the blackboard， uniformity of blackboard illuminance， average illuminance of the desks， uniformity of desk illuminance， lighting coefficient of classroom， blackboard reflection ratio， back wall reflection ratio， and distance between lamps and desks were 79.53%， 88.58%， 46.74%， 70.33%，64.69%， 80.86%， 71.81%， 20.30%， 1.63%， and 97.53%， respectively. The average naked eye vision of primary and secondary school students in the 2020 academic year was 4.75±0.37 （right eye） and 4.76±0.37 （left eye）， while in the 2021 academic year， it was 4.70±0.39 （right eye） and 4.71±0.38 （left eye）. There was a significant decrease in the naked eye vision of primary and secondary school students in the 2021 academic year compared to that of 2020 （P<0.05）. Univariate linear regression analysis showed a significant correlation between grade， average illuminance of the blackboard， average illuminance of the desks， uniformity of desk illuminance， lighting coefficient， and distance between lamps and desks， and the decline of students’ naked eye vision within one academic year （P<0.05）. After adjusting for grade， multiple linear regression analysis revealed a significant correlation between the average illuminance of the blackboard， uniformity of desk illuminance， lighting coefficient， and distance between lamps and desks， and the decline of students’ naked eye vision within one academic year （P<0.05）. Higher average illuminance of the blackboard， uniformity of desk illuminance， lighting coefficient， and distance between lamps and desks were protective factors for naked eye vision.

Conclusion The visual environment of primary and secondary school classrooms in Minhang District is a matter of concern. Average illuminance of the blackboard， uniformity of desk illuminance， lighting coefficient， and distance between lamps and desks are related to the degree of visual impairment in students over a year.