Glasses can be bumped off your face in the line of duty, so it is important to have good uncorrected (no glasses) vision.
Vision requirements may vary between police forces, but, in general, an uncorrected (no glasses) vision of 20/40 or better is required in Ontario.
In order to be a firefighter in Ontario, an uncorrected (no glasses) vision of 20/30 or better is required.
Laser Vision Correction (LASIK and PRK) can give you the freedom of excellent vision without glasses.