PRK was the first procedure performed using the Excimer laser. It corrects vision by reshaping the cornea. The difference between LASIK and PRK is that with LASIK a corneal flap is created and the laser is applied to the inner tissue of the cornea. With PRK, the epithelium (or outer skin of the cornea) is removed and a laser is applied to the surface of the cornea. PRK can be used to correct low to high levels of nearsightedness, farsightedness and astigmatism. Lasik uses a laser to change the curvature of the cornea (outer window of the eye). LASIK has quickly become the procedure of choice for most patients because they recover quickly and have fewer side effects and complications than with other methods of vision correction. In fact, most LASIK patients notice a significant improvement in their vision soon after surgery. LASIK removes tissue within the cornea to treat low to high levels of nearsightedness, farsightedness, and astigmatism.