the old way of enhancing a LASIK was to relift the old flap and relaser, or cut a new flap
both methods are fraught with problems, like epithelial ingrowth, or cutting into the old flap
i was the 1st surgeon in NYC to routinely enhance LASIKs by performing a LASEK on top of the old flap
and now this is becoming standard of care across the US
the reason is you eliminate the risk of epithelial ingrowth or flap wrinkles, which is significant
you also don't go deeper into the cornea, so don't weaken it further and cause KC or keratoconus
but please don't call an ASA or LASEK a PRK, or you'll think it hurts, takes a long time to recover, and carries a significant chance of haze or scarring. you really need an ASA or LASEK, and you also should have MMC, or your may very well scar. we use MMC, vit C, branded PredForte, oral steroids, and UV protection after our ASA enhancements of prior LASIKs, which is really necessary to avoid scarring