Photorefractive keratomy performed off-label yields excellent visual outcomes in study

January 1, 2010

Wavefront-optimized PRK performed off-label with a 400-Hz excimer laser produced excellent safety and visual outcomes.

San Francisco-Wavefront-optimized PRK performed off-label with a 400-Hz excimer laser (Allegretto Wave Eye-Q, Alcon Laboratories) produced excellent safety and visual outcomes and a low incidence of serious complications in an active duty military population, according to Kraig S. Bower, MD, who presented the 6-month findings at the annual meeting of the American Academy of Ophthalmology.

The subjects were able to return to full duty by 30 days but would not be deployed to a field environment or combat zone before 90 days, said Dr. Bower, Ophthalmology Service, Walter Reed Army Medical Center, Washington, DC.

The retrospective study was conducted over an 18-month period among 1,200 U.S. Army soldiers who underwent PRK for myopia and myopic astigmatism at the Center for Refractive Surgery at Walter Reed. Although this 400-Hz excimer laser is only approved for LASIK in the United States, eight of 12 Army laser centers have this laser, and 80% to 90% of the 12,000 soldiers who are treated annually undergo a surface procedure. Since such a high number of off-label treatments are performed, it was important to analyze and report the initial results, Dr. Bower said.

Postoperatively, all patients were treated with a high-oxygen-transmissible soft contact lens, a topical fourth-generation fluoroquinolone, a 10-week tapered dose of fluorometholone 0.1%, and frequent doses of nonpreserved artificial tears. Patients were seen on postoperative Day 1 and Day 4, then every 1 to 2 days until re-epithelialization had occurred. Visual outcome measurements were obtained at 1, 3, 6, and 12 months postoperatively, although only results through 6 months were reported.

Testing included uncorrected visual acuity (UCVA), manifest refraction, best spectacle-corrected visual acuity (BSCVA), slit lamp biomicroscopy, IOP, and reports of any adverse events or complications.

The analysis included 2,384 eyes of 1,201 patients who were predominantly male, as expected in an active duty military population; the mean age was 31.5 years (range 19 to 57 years). The mean preoperative spherical equivalent was 3.46 D (–0.75 to –10 D), and the preoperative cylinder ranged from 0 to 4.25 D. Epithelial removal was performed by brush in about 60% of patients and by alcohol in 40%. Mitomycin-C was used in approximately 25% of eyes. No intraoperative complications were reported.

Reporting outcomes 1 month postoperatively in 1,880 eyes, Dr. Bower said that UCVA was 20/20 in 70% of eyes. At 6 months, UCVA was 20/20 or better in 95% of eyes and 20/15 or better in 70% of eyes.

"One of the things that was . . . interesting to those of us who were doing the surgery and who were accustomed to other laser platforms is the fact that . . . only 70% [saw] 20/20 at 1 month postoperatively," Dr. Bower said. "By conventional PRK standards, we felt that was a little low, but by 6 months we had excellent results."

He also reported that BSCVA 6 months postoperatively was unchanged in the majority of eyes, and nearly 25% had gained 1 line of BSCVA. This was particularly encouraging, since 1-month results indicated that 25% of eyes had lost 1 line of BSCVA from their preoperative baseline. The early postoperative loss of acuity was mainly attributable to epitheliopathy or dry eye as well as a few cases of induced astigmatism. The loss was transient, and by 6 months no eyes lost more than 1 line of BSCVA.

Subgroup analysis

Subgroup analysis showed no difference in outcomes for early postoperative visual recovery, UCVA, or maintenance of BSCVA between eyes that had undergone brush or alcohol epithelial removal.

Once the early healing problems typical of PRK had been resolved, treatment complications were minimal and included small numbers of under- or overcorrections, residual astigmatism, and residual dry eye.

Limitations of the study include the retrospective study design, lack of long-term data, and predominance of young male subjects, Dr. Bower said. The latter suggests that the data cannot be extrapolated to the general population without further evaluation. Moreover, the study did not examine the safety and efficacy of PRK for hyperopia or mixed astigmatism.

Additional study is needed to evaluate quality of vision metrics beyond Snellen acuity, such as low-contrast acuity, contrast sensitivity, and wavefront aberrations, Dr. Bower concluded.