Advantages of surface ablation debated

January 1, 2008

The pros and cons of surface ablation procedures were reviewed at the opening session of the refractive surgery subspecialty day at the American Academy of Ophthalmology annual meeting.

Key Points

According to Dr. Azar, safety is one of the most appealing features of surface ablation.

"These procedures avoid several of the limitations of LASIK, including potential microkeratome-and flap-related complications, but most importantly, surface ablation reduces the risk of ectasia," said Dr. Azar, professor and head, Department of Ophthalmology and Visual Sciences, and Field Chair of Ophthalmologic Research, University of Illinois, Chicago.

When combined with mitomycin-C (MMC), surface ablation also may overcome several limitations of phakic IOL surgery and offer a better alternative, especially in patients with absolute or relative contraindications to phakic IOL placement or in whom phakic IOL implantation alone may not provide a good refractive result. Such scenarios include patients with high myopia and shallow anterior chambers, low endothelial cells counts, a history of progressive endothelial cell loss, early cataracts, or high astigmatism.

"In addition, surface ablation may be a safer alternative because it avoids the relatively serious intraoperative and postoperative complications of phakic IOLs," Dr. Azar said.

Considering PRK, surface ablation also has a favorable long-term track record, and although ophthalmologists have less experience with LASEK and epi-LASIK, results from those procedures are encouraging.

Dr. Azar concluded by acknowledging that surface ablation has limitations. In that regard, the unknown long-term risks of prophylactic MMC use is an important concern.

"We can expect to see the indications and boundaries for surface ablation continue to evolve," he predicted.

On the other hand

Reviewing the cons of surface ablation, Dr. Knorz said that surface ablation procedures are associated with more discomfort, slower visual recovery, and worse efficacy and safety profiles than LASIK. Furthermore, they have no advantage for providing a better wavefront outcome.

Dr. Knorz referenced results from comparative studies to support his statements. He cited a prospective, randomized, fellow eye trial conducted by Durrie and Slade comparing wavefront-guided LASIK (sub-Bowman's keratomileusis performed with a femtosecond laser-created 100-μm, 8.5-mm flap) against advanced surface ablation in 50 bilaterally treated patients. The paper is in press, but its results showed that surface ablation was associated with more pain for up to 1 month after surgery and worse visual outcomes through at least 3 months. At 1 month, patients were significantly unhappier with the results of the surface ablation procedure; patient satisfaction with the two procedures was not similar until 6 months. In addition, wavefront evaluations showed no difference between the two procedures in the change in total higher-order aberrations from baseline to 6 months.

A paper by Shortt et al. provides evidence that LASIK is associated with better efficacy and safety outcomes than surface ablation, said Dr. Knorz, professor of ophthalmology, University of Heidelberg, Mannheim, Germany.

That publication, which appeared in Ophthalmology in 2006, presented results from a meta-analysis of prospective, randomized, controlled studies comparing LASIK and PRK for treatment of myopia and a review of prospective data from an FDA case series of myopic LASIK and PRK.

"Despite its disadvantages, surface ablation is a great tool that belongs in our armamentarium. However, its use should be limited to certain patients, including those with thin corneas, epithelial basal membrane dystrophies, or asymmetric corneal topography," Dr. Knorz concluded.