The average Cornea is about 550 microns thick. If you have a Cornea that is less than 500 microns, many surgeons recommend PRK. Laser based correction PRK and regular refractive surgery are both very safe and have similar outcomes and use the same excimer laser.
PRK candidates often have strong correction prescriptions for farsightedness, nearsightedness and astigmatism as well. The only way to know which is right for you is a Laser Vision Screening which includes comprehensive Cornea measurements of both eyes. Typically the recovery time for PRK is slightly longer.