When I looked into it, you can be as young as 17 in most states but they prefer to wait. Your eyesight will typically level out around 24-25, so it doesn’t make a lot of sense to have it done at say 20, then have your eyesight continue to degrade for 4-5 more years. Also, in women, pregnancy can alter your eyesight so if you plan to have children at an early age, they like you to wait until after the baby is born.
18, but i advise you to wait until your eye vision stops changing because then the surgery won’t be that effective…