The link between myopia and academic achievement isn’t news to ophthalmologists – but just how strong is the link, and what could be causing it?
Roisin McGuigan |
A recent study has delved deeper into the association between book learning and short sight (1), led by Denize Atan, an academic ophthalmologist specializing in neuro-ophthalmology at Bristol Medical School and Bristol Eye Hospital, UK. Though Atan’s clinical role centers on managing patients who have neurological conditions affecting vision, her research role centers on performing genetic epidemiology and genetic modeling to further understand the visual pathways in the central nervous system.
“Our first approach was to look for genetic correlations between measures of visual and cognitive function. For more than a century, observational studies have reported links between myopia and higher levels of educational attainment or intelligence, so this was one possible example of an association between visual and cognitive function that might have a common genetic basis,” says Atan. “However, our analyses seemed to suggest that genetic correlations between intelligence and refractive error explained only a very small part of the story.”
Causal relationships are traditionally investigated by randomized controlled clinical trials, but as a randomized clinical trial exposing children to different levels of education would be unethical, Atan and her colleagues took a different approach, using Mendelian randomization.
“The results of our study showed that exposure to more time in education contributes to the rising prevalence of myopia. We found that every additional year of education was associated with an increased myopic refractive error of −0.27 D/year,” says Atan. By contrast, the study found little evidence that myopia led to a longer time in education – in other words, myopia does not appear to lead to better educational outcomes.
The study was not designed to assess how education increases myopia risk – but previous studies and experiments provide some clues, says Atan. “Very simply, those who spend more time in education may have less exposure to natural light. Large differences in ambient light exist between well-lit classrooms (500 lux) and bright sunlight (up to 120,000 lux), and randomized controlled trials have consistently shown that more time spent outdoors during childhood protects against the development of myopia.”
Atan hopes the study will lead to further research and discussion with the aim of reducing the rising tide of myopia. “Given the benefits of time spent outdoors on mental health and the protection it provides against obesity and many chronic diseases, there may be several other reasons why our children ought to spend more time outside,” she adds.
- E Mountjoy et al., “Education and myopia: assessing the direction of causality by mendelian randomisation,” BMJ, 361, k2022 (2018). PMID: 29875094.