You can use the numbers from your glasses, hoewever your eyes can get worse(only happens when you are still growing I've heard).
I go the local shop for glasses & lenses etc once a year and buy 2 packages of 6 lenses(one package for one eye, durr

). If they run out I order the same lenses online, which saves me a lot of money(only around 60 euros for 2 packages, while at the specialist it's 180 euros). Next year I go to the specialist again to see if my eyes have changed.
I'm not really an expert on this subject, I've only had lenses for 1.5 years
