I had PRK in between MEPs and FC1 after being hired. The FC1 article laid out the uncorrected eyesight standards – I opted to get it done while waiting for my FC1 since I knew there’s a 6 month stabilization period required before going into a flight physical.
I had a blessing from my unit’s flight doc, but I didn’t know any “surgery” or operation (PRK, ACL surgery, etc) requires a waiver if you’ve already passed MEPs. Unless you’re going to have PRK regardless of the military, I’d recommend waiting until you’re hired to shell out $$$ for the surgery – just a personal opinion.