Normally humans can adapt to poor vision very well without ever realizing that medically their vision is subpar. Newsprint is written at print which is comfortable for reading at 20/40. Many people will forgo eye exams for many years without complaint. 20/30 vision or worse in adults normally is a good measuring stick in deciding on using glasses.
Any type of nearsightedness (myopia) or farsightedness (hyperopia), to my knowledge, can be corrected with glasses. The type of glasses just differs between the two conditions. are Basically, since they are problems with focus in the eye, each type of glasses must have a different level of focus, to counteract the imperfections in vision.