Short-sightedness
As we all know,the short-sightedness issue in students is serious. The possibility of it happening is over 50%. The number of people who are short-sighted is the most in the world.
(Don't use 'but' to start a sentence)Why do people have short-sightedness ? The reason is complicated and we don't have a medicine to cure it. So the best way is to prevent it with the improvement of people's living standard. Many students have their own phones. Some of them spend a lot of time surfing the Internet or playing computer games. Their eyes get hurt deeply. When they are studying or doing homework,their eyes are too close to the books and they don't pay attention to taking breaks. The optometrist suggested that we should let our eyes rest after an hour. Do more outdoor activities to relax yourself. Lastly, you should be careful about one thing: the posture while holding a pen is connected to short-sightedness.