Green space within a 500m buffer around schools may be an independent protective factor for adolescent myopia. Photo: Robert Collins/Unsplash.

It goes without saying that myopia is a public health issue, particularly in high school-aged adolescents in Beijing who are affected by an alarming prevalence of myopia. As green space has a certain association with factors that can protect against myopia, researchers recently examined its effects and found that a 500m buffer around schools was associated with a lower personal myopia risk among adolescents and a lower prevalence of myopia in schools.

Green space was measured using the normalized difference vegetation index (NDVI). A total of 13,380 samples from 51 high schools were selected from a 2021 Beijing Municipal Health Commission survey. Adolescent myopia was defined as a spherical equivalent ≤-1.00D in the worse eye.

In addition to the 500m buffer associated with a lower myopia risk and prevalence, previous studies have highlighted the greenness of the buffer surrounding the school for the role it plays in students’ social and health benefits.

“We considered that students probably tended to live close to their school to minimize time costs or benefit from opportunities offered by the school (school catchment areas probably encompass the properties nearby),” the study authors explained in their paper. “Thus, the 500m buffer might also cover the students’ outside-school environments. This situation might provide day-long exposure to greener space and reduce the risk of myopia.”

They added that a greener environment could encourage more outside activities after school, encouraging students to enhance social connections with neighbors of the same age instead of playing alone on electronic devices. “In addition, with more green space outside schools, students may have greener routes between school and home, and walking home along an avenue with a tree canopy could be highly inspirational,” they suggested.

It should also be noted that the marked variation in the prevalence of myopia between suburban and urban schools did not occur when the effects of the NDVI of the buffers were considered, which suggests that the greenness level around schools rather than the urbanization of the location could better determine the prevalence of myopia.

Lastly, the effects of green space within the 500m buffer on myopia prevalence varied in different demographic subgroups. Females had a higher myopia prevalence and were slightly more sensitive to the buffer NDVI than males. “This result showed marginalization, which is usually reported in gender variation; that is, females are marginalized with poor health outcomes but gain more than males from green space exposure,” the authors noted.

“We emphasize that green space around schools is an independent protective factor for adolescents’ myopia, and we suggest the importance of the appropriate distribution of within-campus trees for myopia prevention,” they concluded.

Zhang C, Wang C, Guo X, et al. Effects of greenness on myopia risk and school-level myopia prevalence among high school-aged adolescents: cross-sectional study. JMIR Health Surveill. 2023;9:e42694.