November 1, 2021
By Dwight Akerman, OD, MBA, FAAO, FBCLA
There is substantial evidence indicating that environmental factors, including time outdoors and urbanization, can influence myopia development, particularly in school-aged children. It is well known that urban and rural differences in myopia prevalence exist, but few studies have attempted to characterize the built or natural environment using objective means. This study aims to investigate the relationship between the prevalence of myopia and the quantity of vegetation/green spaces across different regions of the world, using an objective satellite imaging technique.
The prevalence of myopia in the 15-to-19-year age group in Australia, Brazil, China, Finland, India, Iran, Japan, Oman, Singapore, South Africa, and the United Kingdom was collected from study data obtained from a systematic review and meta-analysis by Holden et al. (2016). Normalized Difference Vegetation Index (NDVI), an indicator of vegetation density, was derived from Landsat 7 Enhanced Thematic Mapper Plus (ETM+) satellite data. Green space (mean NDVI) was quantified using a 30-kilometer radius buffer surrounding point coordinates corresponding to locations mentioned in the Holden et al. prevalence studies (n = 15) that contributed most to prevalence data.
The researchers found that myopia prevalence increased significantly when green space was <-0.2, but the effect was less apparent for values >-0.1. When a mixed effects model was used, the effect of green space was found to be significantly associated with myopia prevalence (p = 0.05). The researchers concluded that there was evidence of a weak but significant non-linear relationship between myopia and green space, with the effect most apparent at low levels of green space.
A larger data sample, along with further investigations into the utilization of green spaces, is required to understand whether increasing the amount of green space can reduce myopia incidence and progression impact.
Abstract
Is Myopia Prevalence Related to Outdoor Green Space?
Brian An Peng, Thomas John Naduvilath, Daniel Ian Flitcroft, Monica Jong
Purpose: Rapid urbanization and lifestyle changes have been associated with a huge increase in myopia across many parts of the world. There is strong evidence that environmental factors, including time outdoors and urbanization, can influence the development of myopia, particularly in school-aged children. The aim of this study is to determine whether there is a relationship between the prevalence of myopia and the amount of vegetation/green spaces across different regions of the world as a risk factor for myopia development.
Methods: The prevalence of myopia in the 15 to 19-year age group in Australia, Brazil, China, Finland, India, Iran, Japan, Oman, Singapore, South Africa, and the U.K. was obtained from a meta-analysis by Holden et al. Normalized Difference Vegetation Index (NDVI) was used to quantify green space exposure based on Landsat 7 Enhanced Thematic Mapper Plus (ETM+) satellite data. Green space was measured in locations specific to 15 studies that reported myopia prevalence. Simple linear regression was used to analyze yearly data, and a mixed effects model was applied to assess the significance of green space when study was a random effect.
Results: Myopia prevalence increased significantly when green space was <-0.2, but the effect was less apparent for values >-0.1. When a mixed effects model was used, the effect of green space was found to be significantly associated with myopia prevalence (p = 0.05).
Conclusions: There was evidence of a weak but significant non-linear relationship between myopia and green space, with the effect most apparent at low levels of green space. A larger data sample, along with further investigations into the utilization of green spaces, is required to understand whether increasing the amount of green space can reduce myopia incidence and progression impact.
Peng, B. A., Naduvilath, T. J., Flitcroft, D. I., & Jong, M. (2021). Is myopia prevalence related to outdoor green space?. Ophthalmic and Physiological Optics, 41(6), 1371-1381.
DOI: https://doi.org/10.1111/opo.12896
