How can I tell if I'm selecting the correct size reading glasses on Amazon?

Question

I'm new on purchasing reading glasses and I need to find out what dose amazon mean by selecting the correct Glass Size? Do they mean the two glass sizes or between both the glasses like knowing how wide is the nose size so the glasses can fit?

http://www.amazon.com/VisAcuity-Metal-Rimless-Reading-Glasses/dp/B000MT9ZI2/ref=pd_bbs_1?ie=UTF8&s=apparel&qid=1212272077&sr=8-1

Is there a simple way to find out whats my glass size?

Answer 1

The size means the amount of magnifying strength.   How much help do you need?   A size 2 would magnify 2 x larger than the normal print.  If you only need reading glasses either a 1.25 or a 1.50 should be OK.  As far as the actual size of the glasses they are the same. (I wear glasses for reading only and wear a 1.50.)

If you aren't sure go to a drugstore and try on the different strengths of glasses.