One in three children around the world is short-sighted and the number is growing rapidly, according to new research that suggests the increase is associated with youngsters spending more time indoors gazing at screens. Short-sightedness, or myopia, is a “pervasive global public health concern, particularly among the younger population,” says the research team. Some 40% of children worldwide aged five and up will be short-sighted by 2050, says the researchers based in China. Myopia usually begins in childhood, with distant objects appearing blurry. Although it may have a genetic factor, medics…