Elevated Light Levels In Classrooms And Protective Effect On Myopia In School Children

Objectives To determine whether elevated light levels in classrooms can protect school-age children from vision acuity loss, myopia onset or myopia development.Methods A total of 3 687 students aged 6-14 years were eligible to participate in our study, they are from eight schools from rural and urban areas in in Sujiatun district, Shenyang, China. 2 092 children from four schools(one primary school and one junior high school in rural area; one primary school and one junior high school in urban area) took part in intervention program for one year, in which classroom lighting systems have been rebuilt. 1 595 children from the other schools those were selected for a comparable academic burden and adjacent location to intervention schools, took role of the control arm in which lighting systems were not rebuilt. All students took part in school-based unaided visual acuity examinations three times at baseline, six months and one year after intervention using E Standard Logarithm Vision Acuity Chart at a distance of five meters. Of those 317 students selected from rural schools had a comprehensive eye examination including cycloplegic refraction and ocular biometry such as axial length(AL), anterior chamber depth(ACD), and corneal curvature(CC), and filled out a questionnaire. The old lighting and new lighting in intervention arm were compared with control arm by Wilcoxon rank sum test separately. Three vision acuity results between the two arms were compared with multivariate analysis of covariance with repeated measures. Changes in refractive error and ocular biometry between the two arms were compared by a t test, and the possible factors that might cause differences were explored with multivariate linear regression analysis.Results Before the intervention, lighting levels in the two arms were not significantly different. The median average illuminance of blackboards and desks and uniformity of desks lighting were significantly improved, however, the uniformity of blackboard lighting declined after intervention. Compared the three average scores of vision acuity in the intervention arm(4.87±0.23, 4.84±0.25, and 4.85±0.23 at baseline, intervention after six months and intervention after one year, respectively) to those in the control arm(4.88±0.22, 4.84±0.25, and 4.81±0.27), the significant difference was found between the two arms(P<0.001). The average scores of vision acuity after intervention one year in intervention arm was significantly higher than that in the controls(P<0.001). In subsample, the mean refraction, AL, CC, ACD, myopia prevalence, mean age, mean vision acuity, boy-to-girl ratio, Han-to-minority nationality ratio and primary-to-junior high school ratio between the two arms were not significantly different at baseline. After one year, compared with the control arm the intervention arm had lower new myopia onset(3.9% vs. 10.1%; P<0.05), a smaller decrease in refraction among nonmyopic subjects(-0.25 diopter [D] vs.-0.47 D; P<0.01), and shorter axial growth for both nonmyopic(0.13 mm vs. 0.18 mm; p <0.05) and myopic subjects(0.20 mm vs. 0.27 mm; P<0.01). Multivariate linear regression analysis showed intervention program, lower hyperopic baseline refraction, lower education levels of fathers, and longer times for sleep and screen-viewing activities were associated with decreases in refraction in nonmyopic children. For myopic subjects, myopia progression was significantly associated with family income only. Intervention program and older age had a protective effect on axial growth for both myopic and nonmyopic subjects. The father’s education level and sleep duration were significantly associated with axial growth in nonmyopic children.ConclusionsElevated light levels in classrooms have a significant effect on vision acuity loss, myopia onset, decreases in refraction, and axial growth for children in primary and junior high schools. Therefore, the ambient light levels in schools should be improved.