“Elevated Light Levels in Schools Have a Protective Effect on Myopia”, 2015-04-25 ():
Background: To determine whether elevated light levels in classrooms in rural areas can protect school-age children from myopia onset or myopia progression.
Method: A total of 317 subjects from 1,713 eligible students aged 6–14 in 4 schools located in northeast China participated in the study. Students received a comprehensive eye examination including cycloplegic refraction and ocular biometry, which included axial length (AL), anterior chamber depth (ACD), and corneal curvature (CC) measurement, and completed a questionnaire.
The intervention arm included 178 students in two schools with rebuilt elevated lighting systems and the control arm included 139 students in which lighting systems were unchanged.
Results: for the two arms were compared with a Wilcoxon rank sum test, a χ2 test or a t-test, as appropriate. Factors that might help explain any differences were explored with multivariate linear regression analysis.
Results: The median average illuminance of blackboards and desks and uniformity of desk lighting were statistically-significantly improved, however, the uniformity of blackboard lighting declined after intervention. At baseline, the mean refraction, AL, CC, ACD and myopia prevalence between the two arms were not statistically-significantly different.
After 1 year, compared with the control arm the intervention arm had a lower incidence of new myopia onset (4% vs 10%; p = 0.029), a smaller decrease in refractive error among no myopic subjects (−0.25 dioptre [D] vs −0.47 D; p = 0.001), and shorter axial growth for both non-myopic (0.13 vs 0.18 mm; p = 0.023) and myopic subjects (0.20 vs 0.27 mm; p = 0.0001).
Multivariate linear regression analysis showed the intervention program, lower hyperopic baseline refraction, lower father’s education level, longer time sleeping and less time in screen-viewing activities were associated with less refractive shift in the direction of myopia in non-myopic children. For myopic subjects, myopia progression was statistically-significantly associated with family income only. The intervention program and older age had a protective effect on axial growth for both myopic and non-myopic subjects. The father’s education level and sleep duration were statistically-significantly associated with axial growth in non-myopic children.
Conclusion: Elevated light levels in classrooms have a statistically-significant effect on myopia onset, decreases in refraction, and axial growth; if the findings of lighting intervention are reproduced in future studies, the ambient light levels in schools should be improved.