Are screens and low exposure to outdoor light really responsible for the rise in myopia?
Screens are probably not the main culprit; too little time outdoors and academic pressure are better-supported causes. Make sure your child spends sufficient time outside every day, especially at a young age.
Myopia in children has increased considerably over recent decades, and the combination of little time spent outdoors and a great deal of near work is the most plausible explanation. The strongest evidence concerns outdoor time: each additional hour per day spent outside reduced the odds of myopia by approximately 10 percent (odds ratio 0.90). Randomised studies and research that uses genetic variants to distinguish cause from effect confirm that this is a genuine causal relationship, not merely an association.
Screens themselves probably play a smaller role than you might expect. An analysis of five studies found a pooled odds ratio of 1.02, which is not statistically significant. Screen use and little time spent outdoors often go hand in hand, making it difficult to measure their effects separately. More recent studies do suggest a trend, but objective measurements of screen time are usually absent.
Near work, such as reading and writing, has been a subject of debate for decades. Early studies found barely any association. Newer studies find an elevated risk when viewing distance is less than 30 centimetres and when viewing continues uninterrupted for more than 30 minutes. How near work is measured turns out to strongly determine whether any association is found at all. More years of education and greater academic pressure have been causally linked to myopia through genetic research.
That outdoor light is the key factor is also apparent from the fact that indoor sport offers no protection. Physical activity in itself does not help; what matters is exposure to daylight. The lockdowns during the coronavirus pandemic provide a striking illustration: in 6-year-olds in China, the prevalence of myopia rose from 5.7 percent to 21.5 percent in 2020, compared with the years 2015 to 2019. In children aged 9 and older this effect was much smaller, suggesting that young children are particularly vulnerable during a critical phase of eye development. A historical example reinforces this picture: in Arctic Inuit communities, myopia rose after the Second World War from less than 3 percent to more than 50 percent in new generations, coinciding with a forced transition to indoor living and intensive schooling.
This answer draws on several large studies in children, including randomised studies and genetic research that can separate cause and effect more reliably than ordinary observations. The evidence is strongest for outdoor time. For screen use alone, the evidence is thin and contradictory. The coronavirus lockdown data come from a single Chinese study with methodological limitations, such as the absence of specific eye measurements, so those findings warrant some caution.
Do your eyes age faster than the rest of your body?
The lens of the eye ages noticeably early and quickly, but whether your eyes as a whole age faster than the rest of your body has not been demonstrated. The retina actually reveals a great deal about your overall health, so the two track more closely together than you might think.
Do I live longer with more social contact?
More social contact is associated with a longer lifespan, but the effect is far more specific than you might think: the type of contact and your sex make a difference, and quality counts more than quantity.
Why are antibiotics becoming less and less effective?
Antibiotics are becoming less effective because bacteria naturally possess protective mechanisms and eighty years of intensive use has greatly accelerated their spread. Use antibiotics only when truly necessary, and always complete the full course to limit the selection of resistant bacteria.
How do I know whether my fatigue is caused by my thyroid?
Thyroid blood tests can rule out or confirm whether your thyroid is the cause, but a mildly abnormal TSH alone does not explain fatigue and treating it often does not help. In Hashimoto's, symptoms can persist even when your values are normal.
How do you recognise gum recession early, and which habits can inadvertently make the problem worse?
Early gum recession is usually only detected by the dentist, not at home. Aggressive brushing, inflammation and smoking are the habits that offer the most concrete room for improvement.
How do I keep my eyes healthy and prevent cataracts or macular degeneration?
Protect your eyes with UV-filtering glasses, a diet rich in vegetables and fruit, good diabetes management and regular eye check-ups. If cataracts have advanced significantly, surgery is the only proven solution.