If we talk about failure rate such as complications leading to loss of vision, I think it is about 0.1-0.2%, as it is so rare having a patient lose vision.
Failure rates in terms of the patient's satisfaction (is he/she able to see everything he/she desires without wearing a spectacle), I think that you can consider it to be about 1-2%.
If the 1-2% of patients who are over- or under-corrected are unhappy, they have to face something called “LASIK enhancement”. Most LASIK clinics would give an enhancement period of 3 years at a special price.
