PRK is used to treat refractive errors, whereby the anterior surface of the cornea is modified by an excimer laser. In 1988, Marguerite McDonald, MD, FACS, of New York, performed the first excimer laser PRK. Since that time, milions of patients with refractive error have been treated with PRK. The short-term stability has been demonstrated in many studies, but only few long-term results are available.1-6 In this article, we will present data from our 10-year follow-up study on PRK.
METHODS AND PATIENTS GROUP
In our clinic, we started performing PRK in 1994. We used the Keratom II (Schwind eye-tech-solutions, Kleinostheim, Germany), a first-generation broad-beam excimer laser. It has a fixed pulse repetition rate of 30 Hz, and an eye tracker was added in 1995.
We recalled patients who had myopic laser correction from September 1994 to December 1995. From the original group of 300 eyes (265 patients), 34% (103 eyes of 52 patients) attended the 10-year follow-up visit. The mean age of patients was 39 ±9 years, the preoperative mean spherical refraction was -4.90 ±2.20 D, and the range of diopters was wide (ie, -0.50–14.50 D). Twenty percent of eyes were between -0.50 and -3.00 D; 58% eyes were between -3.00 and -6.00 D, and 22% of patients with myopia were higher than -6.00 D. The mean preoperative cylindrical refraction was -0.96 ±1.08 diopters of cylinder (Dcyl) (range, -5.75–0.00 Dcyl), the mean UCVA was 0.06 ±0.05, and the mean BCVA was 0.95 ±0.23.
In addition to UCVA and BCVA, all patients underwent a detailed ophtalmic examination before surgery, 1 year, and 10 years postoperatively that included slit-lamp microscopic examination, corneal topography, applanation tonomentry, and fundus examination (Table 1).
RESULTS
At 1 year postoperative, the mean spherical refraction was -0.57 ±1.29 D (range, -8.50–1.00 D). At 10 years postoperative, 93.2% eyes were stable, and the mean spherical refraction was -0.84 ±1.40 D (range, -9.00–1.50 D). Spherical refraction decreased by more than 1.00 D in seven eyes (6.8%).
In our initial PRK cohort, we also operated on patients with high myopia. One patient with unstable myopia had a spherical refraction of -14.00 D before surgery. At 1 year postoperative, she had -8.50 D and -9.00 D after 10 years. All examined patients were satisfied.
The mean cylindrical refraction at 1 year postoperative was -0.77 ±0.59 Dcyl and -0.9 ±0.66 Dcyl at 10 years. UCVA was 0.87 ±0.29 after 1 year and 0.69 ±0.3 at the time of last visit (Figure 1). BCVA was 1.01 ±0.17 at 1 year postoperative and 0.97 ±0.11 after 10 years. Grade 1 haze was observed in one eye (0.97%). At the date of last visit, grade 2 haze was observed in two eyes (1.94%), however, we did not observe haze of a higher grade.
Despite the high accuracy of PRK for the correction of most myopic cases, six eyes (9.8%) in our series were unstable. In these eyes, we found prolongation in the anterioposterior axis. This reflects steady growth of the axial length, but it does not necessarily mean that the cornea was not stable.
Most patients, as well as surgeons, wonder what will happen 10 or more years after an excimer laser procedure. We may now provide them with a reassuring answer, based upon ours and others research.1-6 We found that, 10 years after surgery, spherical refraction was stable in 93.2% of eyes. In the 1990s, PRK was performed on patients with wide ranges of myopia. Since this time, the indication criteria have changed to resemble worldwide results, including our own. We presently suggest that PRK be performed for myopia up to -6.00 D.
Laser treatment technology for refractive errors is constantly gaining precision. Today, we use algorithms allowing individual ablation profiles for a given eye. In the higher diopter range, we may either use LASIK or implant a phakic IOL.
In conclusion, we have shown that refractive stability was maintained for up to 10 years in 93.2% of eyes managed with PRK for low, moderate, and high myopia. Unstable refraction—caused by continuing eye growth—was found in 6.8% of eyes. For that reason, it is important to find patiens with progressive myopia prior to laser surgery. All treated patients were satisfied with their vision. We believe that PRK achieves excellent and stable long-term results in patients with myopia up to -6.00 D.
Alena Feuermannová, MD, is from the Department of Ophthalmology, Charles University, Hradec Králové,, Czech Republic. Dr. Feuremannová states that she has no financial interest in the products or companies mentioned. She may be reached at feuerale@fnhk.cz.
Vera Lorencová, MD, is from the Department of Ophthalmology, Charles University, Hradec Králové,, Czech Republic. Dr. Lorencová states that she has no financial interest in the products or companies mentioned. She may be reached at lorencovar@lfhk.uni.cz.
Pavel Rozsíval, MD, is from the Department of Ophthalmology, Charles University, Hradec Králové,, Czech Republic. Dr. Rozsíval states that he has no financial interest in the products or companies mentioned. He may be reached at rozsival@lfhk.cuni.cz.
Juraj Urminsk´y, MD, is from the Department of Ophthalmology, Charles University, Hradec Králové,, Czech Republic. Dr. Urminsk´y states that he has no financial interest in the products or companies mentioned. He may be reached at urminsky@seznam.cz.
Up Front | Sep 2007
Long-Term Follow-Up on PRK
After 10 years, refractive stability maintanence occurred in most eyes with moderate-to-high myopia.
Vera Lorencová, MD; Pavel Rozsíval, MD; Juraj Urminsky, MD; and Alena Feuermannová, MD
