Now that PRK and LASIK have both existed as surgical options for more than 5 years, it is interesting to assess the strengths, weaknesses, and popularity of each procedure. Doing so reveals that PRK is a valuable treatment option.
LASIK's PROS AND CONS
LASIK rapidly overtook the popularity of PRK in Europe and the US between 1997 and 2001. LASIK's allure was quick postoperative visual recovery, often termed the WOW factor. Marketing efforts by ophthalmologists and reporting by the media equated a quicker visual recovery with better surgery, and the public had a hearty appetite for this line of reasoning.
Nevertheless, the media also publicized the fact that a small but significant percentage of patients experienced poor LASIK flaps, irregular astigmatism, and a disappointing surgical result. An individual who returned to the office the day after undergoing laser vision correction had to report great vision to his colleagues around the water cooler, or else common wisdom said the surgery was “not as good” or the patient's surgeon “did something wrong.” Several Web sites are dedicated to laser vision correction problems, 99% of which involve the LASIK flap in one manner or another.
PRK's PROS AND CONS
The knock on PRK (and I classify LASEK as a form of PRK) has generally been twofold: (1) a slower return of visual acuity and (2) corneal haze greater than -5.00 D or so. PRK's major advantage is its safety: because the procedure does not entail the creation of a flap, it offers a greatly reduced incidence of complications.
Mitomycin C (MMC) has essentially eliminated the problem of corneal haze after PRK, and it has thereby restored the procedure's value. I have used MMC (0.02% for 2 minutes postoperatively) for more than 3 years in at least 1,500 cases without any problems whatsoever. Some surgeons talk of the potential long-term effects of MMC, but clear corneas free of healing issues after 3 years is a strong signal to me that the use of this agent is justified.PRK VERSUS LASIK
Compared with LASIK, the importance of PRK is that it is the only keratorefractive laser procedure that can permanently reshape the cornea and smooth an irregular corneal surface without clinically weakening the cornea. As a result, the surgeon has the ability with PRK to simultaneously treat mildly irregular corneas and change a patient's refractive error while also improving his BCVA. To support my points, I submit two case examples.
The first patient, a 35-year-old white male, had high myopia and known keratoconus for 20 years (Figure 1). He wore glasses because he was contact lens intolerant. His manifest refractions were -11.00 +1.50 X 120 = 20/30 OD and -7.00 +2.50 X 35 = 20/25 OS. The patient underwent three treatments (in May, July, and October 2001) with PRK on his right eye and one PRK treatment (in August 2001) on his left eye. As of January 2002, the results in his right eye were a UCVA of 20/30+ and a manifest refraction of -2.00 +1.25 X 100 = 20/20-. In his left eye, he had a UCVA of 20/25- and a manifest refraction of -1.25 +0.75 X 155 = 20/20-.
The second patient was a 57-year-old white male pilot (Figure 2). In 1984, another surgeon performed RK on the patient's left eye for a refractive error of -3.25 D with a result of +1.75 -1.50 X 5 = 20/20. The same surgeon then performed hyperopic LASIK on that eye with a result of -4.00 -1.00 X 85 = 20/20- and significant epithelial ingrowth. In June 1999, I lifted the LASIK flap, removed the epithelial ingrowth, and achieved a result of +1.50
-1.25 X 110 = 20/20. Lifting the LASIK flap created multiple wedge-shaped segments of cornea. I performed uneventful hyperopic PRK on the patient's left eye in September 2002, and the patient's UCVA postoperatively was 20/20 (-0.25 D sphere). In July 1991, I had treated his right eye with RK and achieved a UCVA of 20/20.
I would hope that these two patients constitute satisfactory clinical proof to my skeptical colleagues that PRK is a valuable option for diseased corneas. The procedure does not change hard contact lens wear or penetrating keratoplasty protocols. Weakening a cornea with mild keratoconus by 3% to 5% does not clinically alter the course of the keratoconus, but the patient may be given the gift of 20/25 UCVA. Is this vision perfect? No. Is the patient helped tremendously? Yes. The role of refractive surgery is not only to treat routine eyes that require contact lenses and spectacles, but also to treat diseased eyes that can achieve functional vision and/or an improvement in symptoms. Table 1 shows some of the ocular conditions that I have successfully treated with PRK during the past 10 years.
The truth about PRK is that it is valuable for the treatment of healthy and abnormal corneas. The procedure can convert an irregular corneal surface into a smooth one, an ability that no other corneal laser procedure possesses. PRK does not offer quick visual recovery and a lot of glitz, but it has other benefits such as safety and consistent, excellent results. Even when an anterior chamber, posterior chamber, or in-the-bag IOL corrects a patient's refractive error, PRK can improve or eliminate his mild-to-moderate corneal irregular astigmatism and perhaps obviate the need for a penetrating keratoplasty.
In Europe, ophthalmologists performed more PRK than LASIK procedures in 2002! I fully expect that the latter procedure will remain the most popular form of laser vision correction in the US, but I anticipate that the volume of PRK procedures will also rise. For surgeons who contend with the rehabilitation of vision, PRK with adjunctive MMC has been a godsend.
Finally, I believe that the increased use of PRK for many indications suggests a maturation of laser refractive surgery from a pigeonholed, specialty procedure to a routinely accepted mode of treatment. After 10 years, PRK is finally receiving the accolades it deserves as a valuable component of corneal surgeons' armamentarium.Lee T. Nordan, MD, is the director of Nordan Eye Laser Medical Group in Carlsbad, California. Dr. Nordan may be reached at (760) 930-9696; firstname.lastname@example.org.