How PRK Works
The laser used in photorefractive keratectomy is called an excimer laser. It emits a specific wavelength of far-ultraviolet light energy that vaporizes fractional layers of cells, leaving a very smooth surface.
By carefully sculpting the shape of the outer layer of the cornea, this laser -- a "cool" laser that does not produce heat -- creates an optimal surface layer for the eye's lens.
For nearsighted patients, the laser slightly flattens the top of the cornea. For farsighted people, PRK surgery yields a slightly steeper cornea. In patients with astigmatism, the laser smooths out irregularities.
The equipment your surgeon uses includes a corneal topographer, an instrument that can perform the precise measurements and calculations needed to map your cornea and the desired correction.
PRK vs. LASIK
PRK laser eye surgery is an older procedure than LASIK, and most surgeons and patients today prefer LASIK, which has a shorter recovery time with fewer reports of pain than PRK.
However, PRK still has a place in the laser surgeon's practice. It is a useful option for patients whose corneas are too thin to make LASIK an option, or for patients who have moderately dry eyes.
Clinical trials in which patients received LASIK in one eye and PRK in the other showed that the result as far as their final visual acuity was much the same. The primary difference was in the recovery time and level of discomfort.
What is PRK?
PRK is the common name for a surgical procedure called photorefractive keratectomy. It uses an excimer laser to sculpt an area on the surface of the eye, rather than making cuts in the cornea, removing an area the thickness of 1 to 3 human hairs and molding the top of the cornea to make accurate and specific corrections to the patient¡¯s vision.
PRK can be used to treat nearsighted, farsighted, and astigmatic eyes. It has some disadvantages compared to the newer and more common LASIK surgery ¨C notably, a longer and more painful recovery time ¨C but is still a valuable option, especially for patients whose corneas are too thin to make them candidates for LASIK. In addition, PRK is one of the procedures most likely to be approved for active-duty members of the U.S. military services.
What to Expect Before PRK Surgery
You should have a thorough consultation with your optometrist, and understand what correction is needed and why PRK is the best choice for you. You should also consult with your surgeon and understand the process and the risks.
You may also have your eyes tested for tear production -- if you have "dry eye," you can still have PRK, but may need to take extra steps to ensure your eyes are hydrated.
You will be asked not to wear your contact lenses for one to three weeks before the procedure, so that the error in your eyes can be measured accurately on the day of the surgery. In addition, you should be asked to refrain from wearing any scented product, hair spray, or makeup on the day of the surgery. Finally, you should arrange for someone to bring you home from the surgery and perhaps be available for a day or two afterwards -- some patients have reported they are unable to see well enough to take their medications until their eyes have healed a bit.
Who Should Consider PRK
PRK is a useful alternative to LASIK for patients who have thin corneas. In addition, some doctors believe PRK to be more effective than LASIK for mild to moderate nearsightedness, though clinical data on this suggest there is not much difference.
Otherwise, the criteria for PRK are the same as those for other forms of refractive surgery. People who have unstable eyes (particularly those under 18), women who are pregnant or nursing, and those with certain medical conditions are not considered good candidates for successful PRK eye surgery. A good surgeon will meet with you to answer any questions you have, but also to test your eyes and take your medical history, before you schedule your surgery.
What to Expect After PRK Surgery
Most doctors advise taking a few days off from work after PRK eye surgery. You'll also be advised to avoid strenuous exercise for up to a week, as this could get in the way of your healing.
You will wear a special "bandage" contact lens for a few days, and will need to use eye drops for several weeks. It may be several days before you can drive, and you may experience some pain or discomfort, controllable with over-the-counter medication.
It's a good idea to have someone available to drive you home from the surgery and back for the first one or two follow-up exams. Some patients have also reported that right after the surgery they are unable to see well enough to take their medications, so those who live alone may want to enlist some help for those first couple of days until they can see well enough to care for themselves.
Risks of PRK
Any surgery, particularly on such a sensitive area as the eye, includes risks. PRK is considered safer than LASIK because the surgeon does not cut into the cornea, but works only on the surface.
Many of the risks of PRK are the same as those for LASIK. Night glare is a fairly common side effect and will improve with time. There is also a risk of not getting the precise correction needed, so that you may still need corrective lenses after the surgery. When you reach your 40s, you may still need reading glasses for presbyopia.
The FDA and FTC have required providers of PRK and other laser surgeries to inform patients about the risks in their advertising and in preoperative consultations. If you don't feel you're getting full information, ask questions, and consider using another provider.
What to Expect During PRK
Your eye will be numbed with anesthetic drops, and you'll lie down for the procedure. The surgical team will place a speculum over your eye to hold it open -- this sounds uncomfortable but normally isn't -- and you'll be asked to look at a target light while the doctor operates. Try to maintain your focus on this light -- it's important for getting the best results from the surgery. Many clinics find it helps to give the patient a stuffed toy or other object to hold onto during the surgery.
The actual PRK laser eye surgery takes less than a minute. The laser will probably make clicking sounds during the procedure, and you may smell a faint acrid odor. This is normal.