My normal reading glasses are +1.5, however I have an off the peg pair for when I need to read the map, and they are +4. With these I can make out all the detail that I cannot see with my normal glasses.
That is a good idea. I have been carrying a 3" magnifying glass in my pocket on my last couple of long distance walks as it was less likely to get broken than my glasses. A cheap pair of glasses that magnify a bit more, that I could hang around my neck, could be even better. I used to use the magnifying bit in the end of the compass but it was a bit too small to really help much!