Radial Keratotomy or RK and Photorefractive Keratectomy

Radial Keratotomy or RK and Photorefractive Keratectomy or PRK are other refractive surgeries used to reshape the cornea.

In RK, a very sharp knife is used to cut slits in the cornea changing its shape.

PRK was the first surgical procedure developed to reshape the cornea, by sculpting, using alaser.

Later, LASIK was developed. The same type of laser is used forLASIK and PRK. Often the exact same laser is used for the two types of surgery. The major difference between the two surgeries is the way that the stroma, the middle layer of the cornea, is exposed before it is vaporized with the laser. In PRK, the top layer of the cornea, called the epithelium, is scraped away to expose the stromal layer underneath. In LASIK, a flap iscutin the stromal layer and the flap is folded back.

Another type of refractive surgery is thermokeratoplasty in which heat is used to reshape the cornea. The source of the heat can be a laser, but it is a different kind of laser than is used for LASIK and PRK. Other refractive devices include corneal ring segments that are inserted into the stroma and special contact lenses that temporarily reshape the cornea (orthokeratology).