The glasses are already designed to correct presbyopia only, so they should be worn if you need glasses only for reading. They should not be worn for driving or watching television. Ready-made readers are a one-size-fits-all and so the frame may not fit you and you may not be looking through the center of the lenses, which can cause headaches or eyestrain. They are also made so that the lenses in both eyes are the same, and so they are not ideal for people who have one eye that is different from the other. They also can not correct astigmatism .
Ready-made reading glasses can be useful as spare glasses for some people to do thing such like shopping, or keep a pair in the car of reading maps. Moreover, it is less important if you lost them because that they are inexpensive. We recommend that if you need glasses, you have at least one proper custom-made pair which you use for most reading, with ready-made reading glasses as additional pairs.