Myopia is predominantly genetic or predominantly environmental?

Points of agreement
- Intensive education, insufficient time outdoors and, potentially, high levels of electronic device-based near viewing play an important role in myopia development.
- Molecular genetic studies have identified rare genetic variants that cause high myopia in a deterministic manner, as well as hundreds of common genetic variants that have more subtle, non-deterministic effects on the risk of myopia.
- Polygenic risk scores can explain only 20% of the variation in refractive error in the population, which falls far short of the 70%–90% heritability estimated from twin studies (this deficit is termed the ‘missing heritability’).

Issues to be resolved
- Is the 70%–90% heritability observed in twin studies evidence of a strong genetic predisposition or an anomaly caused by a higher concordance of environmental risk factor exposure in monozygotic twin pairs compared to dizygotic twin pairs?
- Will larger genome-wide association studies (GWAS), combined with rare variant analysis, gene-gene interaction and gene-environment interaction studies, explain the missing heritability of refractive error or have current polygenic risk scores already reached their limit?
- Are geographic differences in myopia prevalence mostly driven by lifestyle differences between countries or by genetic differences between populations?
- Is the increased risk attributed to parental myopia mostly due to genetics or to parents creating a myopiagenic environment for their children?
- How can conflicting findings be reconciled, such as within-family differences in myopia risk associated with regular versus Orthodox Jewish schooling, or the absence of myopia in a proportion of children growing up in urban East and Southeast Asia despite a highly myopiagenic environment?