The Real Reason of Myopia in Children and Its Prevention Myopia, or nearsightedness, affects over 34 millions of Americans over the age of 40. However, within the age range of 12-54, this condition affects over 41% of the population. It’s predicted that by 2050, nearly 50% of the entire world’s population will be nearsighted. And the main reason for this is an epidemic of myopia in children, which is caused by the simple fact that they don’t spend enough time outdoors.