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Photorefractive keratectomy (PRK), an early form of laser surgery that predates LASIK, is used to treat myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (blurry vision).
Like LASIK, PRK uses an excimer laser to reshape the cornea. PRK involves removing the cornea’s thin epithelial layer to expose the treatment area, and unlike LASIK, no flap is created. The epithelial layer then grows back as the cornea heals after surgery.
The flap in LASIK is what allows very fast, overnight recovery. PRK is similar to LASIK in terms of its success and predictable visual outcomes, but it differs significantly in recovery time. The procedure begins with the surgeon applying a solution to the cornea that loosens the surface layer of cells. These cells, which are much like skin cells, are then removed and discarded. The excimer laser is then applied, precisely as in LASIK, to reshape the permanent tissue of the cornea. A cool solution is then applied to the cornea and a bandage contact lens is placed on the eye. This bandage contact lens facilitates healing of the “skin” cells of the cornea, a process that takes approximately four days. During this healing phase, the eye will be intermittently uncomfortable: scratchy, sandy, gritty, itchy, and light sensitive. Patients typically require one month to achieve excellent, stable vision.
Despite the more uncomfortable and protracted recovery, PRK does have advantages over LASIK. The flap in LASIK is typically about 20% of the corneal thickness, leaving 80% of the corneal tissue to work with. In PRK, the surface layer of cells that is removed is less than 10% of the corneal thickness, leaving more available tissue to work with. Thus, PRK can be the only option for patients with thin corneas. In addition, patients with high levels of myopia may benefit from PRK, because the thicker workable tissue allows a greater range of correction than LASIK.
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