Question: I have two pairs of glasses -- one of which has an older prescription. Is it okay to go back and forth between the two?
Answer: If you have two pairs of glasses -- one which is older and one which is newer, and you go back and forth, it may be because they're really meant for two different tasks. And if one works for one task and the other for the other task, you're not harming your eyes. But if they're significantly different and you find that one's blurry and one's sharper, you should consult with your eye care professional to see if you need an updated prescription to make things sharper overall.