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Myopia could be linked to longer periods spent in education

Educational practices may need to change to prevent damaged vision

Adrian O'Dowd

Thursday, 07 June 2018

People who spend longer in full-time education may have a higher risk of developing short-sightedness (myopia), suggests a study* published today by The BMJ.

The researchers say their study provides “strong evidence” that more time spent in education is a risk factor for myopia, and this may have implications for educational practices.

Myopia is a leading cause of visual impairment worldwide and currently, 30-50% of adults in the US and Europe are myopic, with levels of 80-90% reported in school leavers in some East Asian countries.

Based on existing trends, the number of people affected by myopia worldwide is expected to increase from 1.4 billion to five billion by 2050.

Previous studies have reported strong links between education and myopia, but it is not clear whether increasing exposure to education causes myopia, myopic children are more studious, or socioeconomic position leads to myopia and higher levels of education.

Therefore, researchers based at the universities of Bristol and Cardiff set out to determine whether education was a direct causal risk factor for myopia, or myopia was a causal risk factor for more years in education.

Using a technique called Mendelian randomisation, they analysed 44 genetic variants associated with myopia and 69 genetic variants associated with years of schooling for 67,798 men and women aged 40 to 69 years from the UK Biobank database.

After taking into account potentially influential factors, Mendelian randomisation analyses suggested that every additional year of education was associated with more myopia (a refractive error of −0.27 dioptres a year).

For example, a university graduate from the UK with 17 years of education would, on average, be at least −1 dioptre more myopic than someone who left school at 16 (with 12 years of education). This level of myopia would mean needing glasses for driving.

By contrast, there was little evidence to suggest that myopia led people to remain in education for longer.

The study had some limitations such as the fact that UK Biobank participants have been shown to be more highly educated, have healthier lifestyles, and report fewer health issues compared with the general UK population, which may have affected the results. However, there was little evidence this could explain the findings.

The researchers concluded: “This study shows that exposure to more years in education contributes to the rising prevalence of myopia, and highlights a need for further research and discussion about how educational practices might be improved to achieve better outcomes without adversely affecting vision.”

In a linked editorial**, Professor Ian Morgan at the Australian National University and colleagues said the evidence suggested it was not only genes, but environmental and social factors that may affect myopia.

They used the example of East Asia, where early intense educational pressures combined with little time for outdoors play has led to almost half of children being myopic by the end of primary school, compared with less than 10% in a study of British children.

“Early onset allows more time for myopia to progress to high and potentially pathological myopia,” they said, adding: “These systems will require substantial change to help protect the vision of future generations.”

*Mountjoy E; Davies NM; Plotnikov D; et al. Education and myopia: assessing the direction of causality by mendelian randomisation. BMJ 2018;361:k2022. DOI:10.1136/bmj.k2022.
**Morgan, I; French, A; and Rose, K. Intense schooling linked to myopia. BMJ 2018;361:k2248. DOI:10.1136/bmj.k2248.

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