First, a multiple choice question: Which exercises can prevent myopia in children? （A. Swimming B. Running C. Table tennis When we didn’t have buildings in the past, our children could look at the trees and mountains in the distance to relax their eyes during class. But now there are lots of tall buildings everywhere, and we are helpless. The prevalence of myopia among children in rural areas used to be much lower than in urban areas, but studies have found that the prevalence of myopia among rural children is also gradually increasing compared to 20 years ago. In fact, it is very important to use recess to get more exercise outdoors and try to see as far as possible to prevent myopia. A recent study in Singapore showed that children who spent more than 3 1/2 hours a day outdoors were less likely to develop myopia. In addition to reducing adjustment spasms and adjustment fatigue, outdoor activities may slow the development of myopia by exposing the eye to more natural light and appropriate ultraviolet radiation, and by making the pupil smaller for clearer imaging. But many parents will surely say: children are so busy nowadays, how can they have so much time for outdoor activities? In fact, the so-called outdoor activities do not mean that they are always outdoors for physical exercise, we can look at the three and a half hours separately: half an hour to one hour each on the way to and from school, 1-2 hours of recess, and one hour of sports, so 3 and a half hours is not much easier? The reason why the human eye can see different objects near and far, all rely on the regulation of the eye. Studies have shown that there are abnormalities in the regulation function in myopic eyes. In particular, myopic children have an adjustment lag when they look close. The closer you look, the longer you look, the less accurate the adjustment, the more pronounced the adjustment lag, the more pronounced the posterior defocus in the retina, and the greater the impact on the formation of myopia, further explaining that working at close range can easily lead to the development of myopia. So now you have the answer? — Play table tennis! In the process of playing ping pong, the eyes must be glued to the fast shuttling, distant and variable rotating ping pong ball, which is an exercise in alternating between looking far and looking near, training the child’s ability to adjust, reducing the adjustment lag and preventing the development of myopia. At the same time, it is also theorized that the tension in the ciliary muscle can be improved, so that it relaxes and contracts, the eyes are staring at the ball in constant motion, the extraocular muscles are also in constant activity, accelerating the blood circulation in the eye tissue, improving eye acuity, eliminating eye fatigue, thus effectively playing a role in preventing myopia.