I was cleaning out my bug out bag and saw something I hadn't seen mentioned here so I thought I would bring it up. I keep a spare pair of glasses in there. I had my scrip changed about a year ago, but hadn't changed the spare pair I carry in my bag. When I put them on the bifocals arn't as strong so I had a hard time reading with them. I'm going to make an apointment and order an extra pair for the bag. The ones I had in there before were the cheap plastic frame pair. The new ones I will order will be what I normaly wear so I can switch them out more easily if they get scratched or something.
Just one more thing to put in the back of your mind, just in case.