You know how every old person you know has to hold things further and further away to read them the older they get? This is presbyopia, or "age-related farsightedness." It eventually happens to everyone, it's just part of getting older. Basically the lens in your eye stiffens over time because of a protein deficiency, and that causes the light to refract at the wrong point in your eye. Folks with otherwise acceptable vision typically correct it with reading glasses