I have 496 and 497 corneal thickness and -4.5 in both eyes. LASIK is off the list. Should I go for PRK or ICL? Male, 18 yrs old

PRK and ICL are both options, but you may want to consider having LASIK with a femtosecond-created flap. The femtosecond laser can create a thin flap which should fit your particular parameters. Remember that whichever option you choose, each procedure carries its own unique set of risk factors. Discuss with your ophthalmologist.

You would likely do well with either.  If price is not an issue, I would recommend the ICL.  Make sure you find an experienced surgeon and it is done in an appropriate setting (ideally not the back room of an office) probably best in a licensed surgery center.

If your surgeon uses Intralase your corneas should be in range for LASIK as femtosecind laser technology can allow for the creation of a thin flap to allow for safe LASIK for your situation. Otherwise PRK or ICL are both reasonable choices.