[Creative Cultivation Program] Your myopia may not be caused by mobile phones, but by staying at home

Author: Wang Pingguo

Reviewer: Pang Yufeng, Deputy Director of Otolaryngology Department, Shanghai Fifth People's Hospital Affiliated to Fudan University

Looking around, more and more people are wearing glasses, not only in China, but also around the world. According to the forecast of the Australian Ryan Horton Vision Institute, by 2050, half of the world's population will be myopic, and 1 billion of them will be severely myopic! A very scary number!

For a long time, people have blamed electronic products for myopia. First it was television, then computers, and now mobile phones have become the target of public criticism. However, according to authoritative scientific research, staying at home too much (staying indoors for too long) may be the main cause of your myopia.

In 2007, researchers led by Katherine Ross studied the myopia rate of children living in Singapore and Sydney. The results showed that although children in Sydney spent more time reading and studying, their myopia rate was only 3%, while that in Singapore was 29%.

Faced with this abnormal phenomenon, the research team continued to investigate and found that the key to the problem may be the difference in outdoor activity time between the two sides. Children in Sydney spent nearly 13.5 hours per week on outdoor activities, while children in Singapore only spent 3.05 hours. This shows that the longer you stay outdoors, the lower the possibility of myopia.

A similar study was conducted in China. Researchers from the Sun Yat-sen University Eye Center selected 12 schools with similar myopia rates, and six of them added 40 minutes of outdoor activity classes every day and encouraged parents to take their children to outdoor activities after school and on weekends. The other six served as the control group and did not make any adjustments, continuing to do what they did before.

The study lasted for 3 years. In the end, the researchers found that the myopia rate of children in schools that increased outdoor activities was 30.4%, while that of children in schools that did not increase outdoor activities was 39.5%, a difference of 9%. This means that outdoor activities can effectively reduce the incidence of myopia.

So why do outdoor activities have such a magical power to prevent myopia? Studies have found that the intensity of light during outdoor activities is a key factor.

You should be able to clearly feel that the light intensity outdoors is much higher than that indoors. For example, in summer, under direct sunlight, the light intensity can reach 60,000-100,000 lux (a unit of light intensity measurement). Even without the sun, the outdoor light intensity can reach 1,000-10,000 lux. Indoors, even in very clear weather, the light intensity is only 100-550 lux, which is hundreds or thousands of times lower than that outdoors.

Our human eyes have evolved over millions of years to adapt to natural light, but artificial light has only appeared for a few decades, and our eyes cannot adapt to artificial light in such a short time. Therefore, long-term exposure to this unfavorable light environment will naturally cause damage to the eyes.

As for the specific mechanism of influence, the current mainstream hypothesis is that outdoor natural light is beneficial to promoting the secretion of dopamine in the retina. This dopamine can prevent the eyeball from growing longer during its development, and the elongation of the eyeball is the main feature of myopic people.

This hypothesis was supported by an animal study from the University of Bingen in Germany in 2010. Ophthalmologists injected dopamine inhibitors into the eyes of chicks, and then they observed that the protective effect of light on the eyes was also weakened.

Of course, in addition to the need for the human eye to receive sufficient light intensity, the duration of light exposure is also very important to prevent myopia. According to research by Ian Morgan, a myopia researcher at the Australian National University, children need to stay in a light intensity of at least 10,000 lux (roughly the light intensity of wearing sunglasses under the shade of a tree in summer) for about three hours a day to effectively prevent myopia.

In 2021, a survey released by the Ministry of Education showed that the overall myopia rate among children and adolescents nationwide was as high as 52.7%, which means that on average one out of every two primary school students is myopic. The myopia problem among children and adolescents is already very serious, and the country has begun to attach great importance to it, and has introduced policy measures such as "burden reduction". Of course, the country can only make macro-controls, and the prevention and improvement of myopia depends on the guidance of parents. Instead of blaming mobile phones, it is better to take children to play outdoors more often when you have time, help children develop good habits of outdoor activities, and let them have a brighter future.

References:

[1] Xie Hongli, Xie Zuokai, Ye Jing, et al. Analysis of the prevalence and related factors of myopia among Chinese adolescents[J]. Chinese Medical Journal, 2010, 90(7):4.

[2] Jiang Jun. White Paper on Myopia Management (2019)[J]. Chinese Journal of Optometry and Visual Science, 2019, 21(3):5.

[3] Chen Zhi. Effects of peripheral myopic defocus on optical defocus myopia models in children and chicks[D]. Fudan University, 2013.

This article is produced by the Science Popularization China-Creation Cultivation Program. Please indicate the source when reprinting