Myopia can occur at any age, from early childhood to late adulthood. Children whose parents had myopia were more likely to develop myopia. Photo: Getty Images.

Understanding the global risk factors for childhood myopia and their impact is useful for developing effective prevention and intervention measures. A recent meta-analysis of 19 cohort studies has provided valuable information for in-depth understanding of the pathogenesis of myopia in children. The researchers, based in China, have found that onset of myopia was related to environmental factors, gender, parental myopia and various eye indicators.

A total of 3,578 children ages seven to 18 were screened among the 19 cohort studies. According to the analysis, girls were more likely to develop myopia than boys (risk ratio; RR: 1.28) and children whose parents are nearsighted are more likely to develop myopia. Children with lower spherical equivalent, longer axial length, lower positive relative regulation, poor vision, deeper anterior chamber and a thinner lens may all anticipate the onset of myopia. Interestingly, children with high IQs had an increased risk of myopia (RR: 1.50). In addition, the burden of myopia was higher in poor countries than in developed ones. Owing to some socioeconomic issues, the risk of myopia onset in underprivileged countries was also far greater.

Longer outdoor activities time (RR: 0.97) and less near-work time (RR: 1.05) appeared to decrease the incidence of myopia. The researchers noted that, “Outdoor activity time and near-work time should be considered with unified standards in future studies.”

“Urbanization, as a critical risk factor for myopia, should be paid attention to by more cohort studies in the future,” the authors of the review also suggested.

“Myopia prevention strategies should be designed based on these factors and eye indicators in order to explore a lifestyle that is more conducive to the eye health of children,” they concluded in their paper.

The team highlighted that, given that myopia has complex etiologies, the effects of some risk factors, such as genes, sleep duration and light exposure, remain controversial and lack sufficient cohort studies for confirmation.