Sunlight in the classroom can be a protective measure against the development of myopia, reducing axial elongation (AL) in eyes of children with a shorter AL, a University of Korea study found.  

Examining the daylight factor (the ratio of indoor to outdoor light) in 50 primary schools, the researchers compared the school with the lowest daylight factor (0.51% and 145 students) with the one with the highest daylight factor (13.35% and 147 students). The refractive error and AL were measured initially and then again after six months. Children were also surveyed on parental myopia, near work and outdoor activities. 

Comparing the change in spherical equivalent, AL, and survey results after six months, the two schools showed similar results, although the initial prevalence of myopia was high in the school with high daylight factor. There were 155 emmetropic children, with a mean AL of 22.7±0.63mm, and 185 children with AL ≥22.7mm showing no difference in the AL change between the two schools. However, the AL change in 107 children with AL <22.7mm was significantly larger in the low daylight school (0.19mm) than in the high daylight school (0.15mm), the study found. 

The study was published by the Korean Journal of Ophthalmology.