In reply to Phil Tucker:
I use a monocle (seriously), goes around your neck and is far, far quicker and easier than a pair of reading glasses.
I slip it into one eye (only need one hand) read map and let it drop. I'm surprised others haven't cottoned onto it. OK it takes a little practise , but only a little and you soon have the hang of it. You put it into one eye, but keep both eyes open to map read; somehow (technical stuff) the eyes compensate and all comes into focus. Obviously you wouldn't try to read a book with it, but damn handy for days on the hills, going out to dinner and reading the menu etc.