The Chinese government reckons that more than 450m people in China, or at least one in three, are short-sighted. Globally just over one in five are. The prevalence of myopia among Chinese schoolchildren is even more alarming. In 2018 an official survey of 1m pupils found that among those aged between 12 and 14, 72% had myopia, up from 58% in 2010. The affliction’s spread in China is partly related to genes. Myopia is more common among East Asians than among white people. But lifestyle plays a big role. A report by the World Health Organisation says the genetic contribution is “considered small”. To the extent that genes are involved, they “may determine susceptibility to environmental factors”. These are often a lack of outdoor activity and excessive “near work”, ie, too much time staring at close objects. The government is trying to reverse the trend. In 2018 it pledged to ensure that, by the end of this decade, less than 60% of 12- to 14-year-olds would be short-sighted. Pupils in the first two years of primary school — a time of life when eyes are highly sensitive to strain — must not be given written homework. Those in the final year of primary school should receive at most one hour of it daily. Schools and families must encourage children to avoid sweets and eat more fish. Experts agree that fish, which has high levels of omega-3 fatty acids, is good for eye health. Many doctors also recommend avoiding sugary foods, though why this helps is unclear. Find the synonym for short-sight. What maybe the most important reason for Chinese pupils to be short-sighted?