Indoor light exposure may increase myopia risk in schoolchildren. Photo: Neon Brand on Unsplash

Environmental factors, such as increased time outdoors and light exposure, have been tied to a lower incidence of myopia. A recent investigation that measured the effect of indoor light intensity on a group of preschool children from Israel found lower amounts of illumination were associated with less hyperopic refractive error.

The study enrolled 1,131 gender-matched children between the ages of four and five from 27 nursery schools in which light intensity ranged from 264 to 804 lux. Light intensity was tested with a lux meter device inside and outside the school. Based on the level of light intensity, the researchers placed the participants in three groups: low illuminance (330 kids, 29%), medium illuminance (434 children, 38%) and high illuminance (367 children, 33%).

The researchers found a significant difference in light intensity among the three groups: 359±2.64 lux in the low illuminance group, 490±2.21 lux in the medium illuminance group and 670.76±3.73 lux in the high illuminance group.

Of note, the mean spherical equivalent was 0.56±0.03D in the low intensity group, 0.73±0.03D in the medium intensity group and 0.89±0.03D in the high intensity group.

Additionally, about 42% of kids in the low intensity group had zero refraction or less compared with 19% of children in the high intensity group.

These findings are consistent with many other studies in the literature that linked light exposure to refractive development, with a possible biological link between increased dopamine release by brighter light and the well-documented ability of dopamine agonists to slow axial elongation, making a direct link more plausible, the investigators suggested.

“If future studies confirm our findings, then increasing the light intensity of classrooms in kindergartens and primary schools could have a significant role to play in controlling the prevalence of myopia,” the authors wrote in their paper.  “Research in this area offers a promising avenue.”

Cohen Y, Iribarren R, Ben-Eli H, et al. Light intensity in nursery schools: a possible factor in refractive development. Asia Pac J Ophthalmol. January 13, 2022. [Epub ahead of print].