Intense schooling linked to myopia

In a linked article, Mountjoy and colleagues (doi:10.1136/bmj.k2022) provide compelling evidence that increased education causes myopia—a matter of sometimes acrimonious controversy for more than 400 years.1 The authors used the UK Biobank sample (www.ukbiobank.ac.uk) to perform an elegant bidirectional mendelian randomisation study, using genetic variants associated with myopia2 and with years of education.3

The logic of mendelian randomisation is simple. Genetic variants are inherited largely independently of potentially confounding variables. Thus, in relation to education and myopia it is possible to ask, with minimal confounding, whether genetic variants associated with myopia lead to more years of education or whether those associated with more education lead to more myopia. The results strongly favoured the second hypothesis.

Many other lines of evidence support a causal role for education.4 As societies have developed formal education systems, the prevalence of myopia has increased from around 1% to as much as 80-90% in young adults. …