Photorefractive Keratectomy (PRK) uses a laser to sculpt the surface of the cornea. This contrasts with LASIK, which sculpts tissue deeper within the cornea, under a corneal flap.
PRK is useful for treating low to moderate levels of myopia or hyperopia with and without astigmatism. It is often the laser vision correction procedure of choice for people with thinner corneas and for individuals who may have certain corneal dystrophies, certain corneal scars, or a condition called "recurrent corneal erosion". Some refractive surgeons prefer PRK over LASIK for all their patients because there is no risk of a flap complication with PRK.
PRK differs from LASIK only in the first step of the procedure. In PRK, instead of creating a corneal flap, the surgeon completely removes the thin outer layer of the cornea (called the epithelium) over the treatment area. This can be done mechanically with a rotating surgical brush (usually after a dilute alcohol solution is applied to soften the epithelium) or with an excimer laser. The second step of PRK is identical to LASIK: an excimer laser is used to reshape the underlying corneal tissue.
A soft contact lens is placed over the eye after the laser ablation to serve as a bandage while the corneal epithelium grows back in place, which usually takes about 3 to 5 days. During this period, the patient usually experiences mild to marked discomfort with blurry vision. Because of the greater amount of tissue healing that needs to take place after PRK, it can take several weeks before vision is clear and stable after the procedure. If you experience complications during PRK, an enhancement surgery may be performed to try to correct your vision to the best possible acuity.
The post-operative discomfort and longer time required for corneal healing and visual recovery are reasons why PRK is not as popular as LASIK. Still, in some cases PRK offers advantages over LASIK, and the final visual outcomes of PRK are usually equal to those of LASIK.