With my cataract surgery, the left eye is “fixed” for long vision and the right eye is “fixed” for medium vision. Being “fixed” means they don't adjust - they are “fixed” where they are.
That means I can't read, period, without glasses to allow that. That scared me to death. As a result I have two prescription reading glasses, and two from the drug store in the strength I need. One of those is extremely small in a case in my purse and they stay there. If I'm away from home and the prescription pair I wear gets broken, that means I can't read jack until I get home, so those tiny ones in the purse will allow me to be able to read in case I need to read before I get home.
In a long term emergency, surely four pair for reading will be enough.
Today, though, I had to use a jewler's loupe to read some fine print on a can of bug poison. Even glasses can't help with everything.
/johnny