Photorefractive Keratectomy, or PRK, is the original laser vision correction procedure. In the early 1990’s, when it was introduced, PRK was performed by removing the epithelium layer by scraping it off with a scalpel. As a result, the procedure caused prolonged healing and excruciating pain. Sometimes, it even caused irregular healing resulting in poor vision. However, the procedure today is much different.
In the modern day PRK procedure, the eye is numbed with eye drops only. The epithelium is removed either with alcohol, a special surgical brush, or with the laser itself. The Excimer laser is then used break molecular bonds in the corneal tissue, thus changing its shape by ablation. This shape change causes the cornea to focus light rays directly on the retina producing clear vision without glasses or contact lenses. Contrary to popular belief, the PRK procedure is not calibrated to overcorrect initially. The Excimer laser is programmed to make the proper correction.
Prior to the preoperative exam of for the PRK procedure, it is important that patients remove their contact lenses for one to two weeks. Contact lenses have the tendency to distort the surface of the eye, preventing the surgeon from getting accurate pre-operative measurements for planning the surgery.
A typical PRK procedure normally takes around four minutes to perform per each eye. And, in contrast to the PRK procedure available in those early days, the modern day procedure does not hurt at all. There is minimal sensation during the procedure and then afterwards, at worst, a patient will have a feeling of an eyelash in the eye.
Some people believe that the PRK procedure is the same as the Radial Keratotomy (RK) procedure. That belief is totally wrong. In Radial Keratotomy, the original Russian surgery for nearsightedness, a scalpel is used to place radially oriented incisions 90% deep in the cornea. The area of the cuts then bulges, causing the central cornea to flatten, thereby inducing the required refractive change in the eye. On the other hand, in PRK, the laser is used to flatten the center of the cornea to trigger the required refractive change.
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