Sun, 22 May 2022

We've known for years now that rates of short-sightedness (scientifically known as myopia) are rising globally. Some estimates even suggest that half of the world's population will be short-sighted by 2050. In the UK and Europe alone, rates of short-sightedness have doubled in the last 50 years.

But we still aren't completely sure why these rates are rising so significantly - and who might be most at risk. This is what a recent study set out to understand. Looking at data from 107,442 participants aged 40-69, the researchers confirmed that rates of myopia have increased significantly in the UK in all age groups - and showed that education level and ethnicity may also be linked to greater risk.

They found that there was a jump in the number of people with short-sightedness when they compared participants born between 1965-1970 with those born between 1939-1944 - going from 20% of the population having myopia to nearly 30%. They also found that a greater number of people were developing short-sightedness in adulthood. Those who developed short-sightedness in childhood were also shown to become highly short-sighted and at greater risk of developing serious eye conditions in adulthood.

To get a better picture of whether certain groups were more at risk than others, the researchers compared participants by sex, ethnicity and education level.

While previous studies have found that women are more short-sighted on average - particularly at younger ages - others have found no difference between men and women.

This study found women had a 24% increased risk of developing myopia in childhood - but were 12% less likely to develop myopia in adulthood. It's uncertain why this is - but it might be due to differences in lifestyle or the hormonal changes men and women experience.

Looking then at ethnicity, the researchers found that there was a higher prevalence of myopia in people who were Chinese. In fact, Chinese participants had a 240% greater risk of developing short-sightedness in childhood compared to white participants. Interestingly, all other ethnicities appeared to have a reduced risk of developing myopia in childhood - though this might be due to the fact that UK Biobank data has fewer participants from ethnic minority backgrounds.

These findings relate to what previous studies have shown, with research suggesting there's a greater prevalence of myopia in east Asia and in people of Asian descent. One study looking at young men in Seoul found that almost 97% of 19-year-olds were myopic. Again, it's not certain why this group has higher rates of short-sightedness. Some theorise it could be caused by lifestyle factors during childhood, such as greater focus on education.

The researchers also looked at the impact that education had on short-sightedness. They found that the more years spent in education, the greater the risk a person had of developing short-sightedness in both childhood and adulthood. They also showed that the youngest participants (those born between 1965-1970) who had a university education were eight times more likely to develop myopia in childhood compared to those that had no formal education qualifications. Previous studies have also shown that people who spent more years in education are more likely to develop myopia.

The nuanced relationship between ethnicity and education was also explored. Having no formal educational qualifications was linked with lower risk of becoming short-sighted, as expected. This was most visibly shown in Chinese participants, where having no qualifications did not change their risk of developing myopia. However, Chinese participants that had higher level qualifications (such as a University degree) had the largest risk of myopia across the whole study.

Although it's clear that education has a large hand in the development of myopia, the direct cause is unknown. Some argue that more time spent reading and using screens may be to blame. There's now evidence even suggesting a link between home-schooling during COVID-19 lockdowns and greater amounts of myopia in Chinese children - potentially because more time is being spent indoors.

But the significant increase in short-sightedness is concerning for a number of reasons. For a person with myopia, having to wear glasses or contact lenses can be costly. More significantly, it also puts them at greater risk of eye diseases - such as myopic maculopathy and retinal detachments, which can both permanently affect eyesight. Not only could this seriously impact a person's way of life, it would also put a greater financial strain on healthcare systems. Short-sightedness in children is even more concerning, as they're more likely to develop into severe myopia - which is more likely to lead to these eye problems as a result.

While you can't change genetics - which is one of the causes of myopia - there are a number of actions you can take to lower the risk of developing short-sightedness during childhood. Spending time outdoors has continued to demonstrate a protective effect against developing short-sightedness. But for children who may already be shortsighted, specialised spectacles and contact lenses are available that have demonstrated success in reducing myopia progression.

Authors: Neema Ghorbani Mojarrad - Lecturer in Optometry, University of Bradford | Sophie Coverdale - Optometrist and PhD Researcher, University of Bradford The Conversation

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