The original LASIK procedure was called PRK, or Photorefractive Keratectomy. It differs from modern LASIK in that PRK would try to preserve the epithelium of the eye. PRK was the first surgical procedure developed to reshape the cornea, by sculpting, using a laser. Later, modern LASIK was developed, but the same type of laser is used for LASIK 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 moved away to expose the stromal layer underneath. In LASIK, a flap is made in the stromal layer.
In both of these corrective procedures your ophthalmologist uses a laser to change the shape of your cornea. This improves the way light rays are focused on the retina. PRK is used to treat myopia (nearsightedness), hyperopia (farsightedness) and astigmatism.