In some parts of China, a shocking 90% of high school graduates experience nearsightedness. Around the world, the number of people with blurry vision is growing. How come? Already for years, experts have been pointing at the detrimental effect of spending too much time inside, staring at screens. Now, evidence shows that they are right. A new study shows that primary school children in China who are spending an extra 45 minutes per day outside in a school activity are at a reduced risk of nearsightedness. The kids who spent more time outside were 23 percent less likely to develop the condition, the authors of the study write. While they are not sure yet why spending time outside is healthy for our eyes, they suspect this has to do with the amount of natural light needed, and the way we use our eyes when we are outside.