When patients have thinner corneas that are a normal shape, and a relatively high prescription then PRK may be the best option for vision correction by laser. PRK is photorefractive keratectomy and this is essentially the same type of procedure as LASIK but unlike LASIK it is not done under a protective corneal flap. Instead, the outer skin of the eye is removed either mechanically or with alcohol, and then the laser reshapes the eye cutting through a thin Bowman's membrane and into the corneal stroma. Bowman's does not heal but a new skin or epithelium grows over the front of the eye and gradually over several days to weeks the vision is recovered. This procedure is less invasive than LASIK, meaning it goes less deep into the surface of the eye, since a flap would have some additional thickness and thus make the treatment deeper. In cases of thinner corneas, it may be prudent to leave more tissue beneath the treatment and PRK can make sense for these cases. There are some other considerations however. First is that with all laser femtosecond LASIK the flap can be made very thin where the invaseiveness is only minimally increased. Second, with PRK there can be scarring, so an "off label" treatment is often done of using a drug called mitomycin to stop potential scarring but this can have an unknown effect on healing and the cornea in general. Although this is thought to be safe, it is a consideration when deciding on which procedure to have. As to dry eye, this is an open question. Some believe that PRK causes less dry eye due to the reduced cutting of corneal nerves, whereas others believe that the increased healing of the epithelium required in PRK can lead to greater dry eye problems post operatively. There is no clearcut answer as to an advantage from this perspective. Therefore the real question becomes, how thin are the corneas, how high is the correction, how large must the treatment zone be, and how strong is the cornea to begin with. In other words, there is much to consider before one can accurately and completely answer this complex question.