Gene-environment interactions in the aetiology of myopia

The term "gene-environment interactions" in statistical genetics refers to the possibility of different genotypes responding differentially to environmental exposures. Myopia is an etiologically heterogeneous disorder, in which there is a low prevalence of clearly genetic myopias, which are generally strongly familial, early in onset and severe. In the last few decades, there has been a marked increase in the prevalence of mild to moderate myopia, particularly in urban East Asia. This increase appears to be strongly associated with changing environmental exposures involving increasingly intensive education and less time spent outdoors. With analysis restricted to this form of acquired or school myopia, there is abundant evidence for environmental impacts, but only limited evidence for genetic contributions. Until the relevant genetic variation has been identified, scientific analysis of gene-environment interactions will not be possible. Currently, it is more parsimonious to interpret school myopia as a disorder caused by environmentally induced excessive axial elongation.