Over-the-counter or ready-made reading glasses are less expensive but are commercially manufactured and may not be safe for you. They are designed only to magnify images in front of you. Unlike prescription glasses, they do not correct nearsightedness, farsightedness, or astigmatism. Eyeglasses from drugstores can cause you problems and it's best to consult the eye doctor to inspect those reading glasses. Drugstore glasses may not be safe because the optical centers are usually off, and not aligned with the center of each pupil, causing eye strain and double vision.