Myopia, or shortsightedness, is an optical deficiency in which we cannot clearly distinguish objects at a certain distance. This disagreeable condition does have an advantage, though. In fact, compared to a person with normal sight, a person with myopia can bring objects closer to his eyes without his vision becoming blurry. Technically, we say that he has a shorter clear distance vision.
Of course, it is rare that we need to bring objects very close unless we want to see details. But this visual advantage was useful to monks who worked as amanuenses, or copyists, during the Renaissance, and who often were shortsighted. By being able to see the smallest details, they were able to create superb illuminated lettering and beautiful scrollwork.