PRK, or photorefractive keratectomy, was invented in the early 1980s and was the first kind of corrective eye surgery to use a laser rather than a blade to remove corneal tissue. PRK uses an excimer laser that sends out a cool beam of ultraviolet light. The laser works by breaking the bonds between the molecules without damaging other tissues. The Food and Drug Administration did not approve its use for PRK corrective eye surgery until 1995. Although LASIK (laser-assisted in situ keratomileusis) is a more popular laser vision correction method, PRK is still performed on some patients who have mild to moderate refractive error.
Best Candidates
PRK can be used to correct vision in both farsighted, or hyperopic, and nearsighted, or myopic people. PRK can also be used to correct astigmatism in some patients by smoothing out irregularities in the cornea. Potential candidates for PRK have to be over 18 years of age and have had a stable eye glass prescription for at least one year. PRK works best for patients who have low or moderate amounts of hyperopia, myopia, or astigmatism; some surgeons perform PRK instead of LASIK in patients who have thin corneas. Patients who have conditions that may affect the health of their eyes, such as diabetes or glaucoma, may also be more appropriate candidates for PRK instead of LASIK. Additionally, patients who have professions that make it dangerous to have a flap on the eye, such as boxers, may benefit form PRK rather than LASIK.
During the Procedure
PRK is performed as an outpatient procedure. The eye surgeon places an anesthetic drop into the patient's eye or eyes. The patient lies down with one eye directly under the laser. The surgeon first removes the layer of epithelial cells that cover the cornea, and then uses the laser to reshape the tissue underneath. A computer program determines the amount of laser needed from the patient's prescription and eye measurements that were programmed into the laser by the surgeon. During the procedure, the patient looks straight ahead at a target to keep the eye in the proper position, and the surgeon monitors both the laser and the patient through a microscope.
After the Procedure
PRK only takes a few minutes to complete; some patients have both eyes done at the same session, while others may wait a few weeks. After the procedure, the surgeon places a special type of contact lens, called a bandage lens, on the eye, which the patient wears for a few days. The eye surgeon also often prescribes antibiotic eye drops and anti-inflammatory drops for the patient to use for a few days. The surgeon will want to evaluate the status of the cornea over the following days to ensure that the eye is healing properly. The patient should be able to resume normal activities within 2 to 3 days after PRK.
Benefits/Advantages
PRK surgery is generally successful at vision correction with a vast majority of patients achieving at least driving vision without correction; most of the rest can achieve driving vision with either contacts or glasses. One other benefit of PRK surgery is the lack of flap complications that can occur after LASIK surgery. Dry eyes, which are fairly common with LASIK surgery, are not as common with PRK. Some doctors feel that the cornea is stronger after PRK surgery than it was before the procedure.
Risks/Disadvantages
Although PRK is a safe and effective procedure, there are possible complications as with all surgical procedures. Since the epithelium of the cornea is removed during the procedure, the recovery time is longer than with LASIK surgery. The corneal epithelium has to have time to grow back. During this healing time, there will probably be pain in the eye. There is always a risk of over- or under-correction, which might require further surgery to correct. There is also a small risk of infection or scarring of the cornea; some patients may notice glare at night. Finally, it can take a few months for the vision to stabilize and reach maximal improvement.
