Advanced surface ablation: future of refractive surgery?

San Francisco-Advanced surface ablations, such as LASEK and Epi-LASIK, are ideal refractive procedures for challenging cases, such as patients with thin corneas and high myopia, and are even better for routine cases, according to Richard W. Yee, MD.

San Francisco-Advanced surface ablations, such as LASEK and Epi-LASIK, are ideal refractive procedures for challenging cases, such as patients with thin corneas and high myopia, and are even better for routine cases, according to Richard W. Yee, MD.

For these reasons, Dr. Yee contends that advanced surface ablations constitute the future of refractive surgery. He spoke during Cornea Day 2006 at the American Society of Cataract and Refractive Surgery.

Advanced surface ablation is the next logical step away from PRK; the term was coined in 2001 by a group at the first International LASEK Congress in Houston, which included Dr. Yee, Dan Durrie, MD, Marguerite McDonald, MD, and James Jester, PhD.

"Advanced surface ablation is very good for problem cases, and even better than lamellar surgery for the routine patients," Dr. Yee stated.

In contrast to lamellar surgery, Dr. Yee believes that advanced surface ablation should be the future of refractive surgery because the complications that are associated with it are not as serious as those associated with LASIK.

"Advanced surface ablation has short-term complications-such as pain and haze-compared with the long-term complications of LASIK that affect the corneal anatomy, physiology, and biometrics and include flap-related complications such as thin flaps or buttonholes," he said.

"Even though the rate of complications is decreasing with improving technology, the rates of flap complications range from 0.3% to 9.1% of cases performed," Dr. Yee explained. He pointed out that in a busy refractive practice, the number of patients with, for example, a buttonhole flap is substantial when compared with surface ablation having zero chances of flap problems.

There is also pathology associated with LASIK procedures that may go unnoticed and perhaps unreported.

In a study of patients who underwent "successful" LASIK procedures (i.e., those with a visual acuity of 20/20), Dr. Yee said more than 50% of the eyes that were examined postmortem were not normal.

"There is epithelial basement wrinkling, microstriae, and epithelial ingrowth," he said. "These eyes are not physiologically and anatomically normal after LASIK."

Another potential risk of LASIK, according to Dr. Yee, is the interface fluid syndrome, which occurs when the LASIK flap separates in patients with high IOP or endothelial cell decompensation. The result of this is unstable vision and refractive error.

There is also a greater incidence of keratectasia associated with LASIK-30 times that seen with advanced surface ablation, according to Dr. Yee.

Other considerations are that the incidence of dry eye is greater in LASIK, and even higher in patients who underwent LASIK and use computers. Creation of flaps in LASIK increases the higher-order aberrations (coma and spherical aberration), and these aberrations are much more significant in patients with large pupils. In addition, the number of stromal keratocytes decreases over the long term.

"The fact that the safety profile and physiological optics are much better in patients who undergo advanced surface ablations cannot be emphasized enough," Dr. Yee said.

Advances in technology, he noted, have made surface ablations much safer.

"The newer technology is better than that used with the original PRK procedures," he said. "The surface ablated with the LADARVision platform (Alcon Laboratories) is better than that treated with the old broad-beam technology.

"Surface ablation will prevail because we have-and will have-an even better understanding of wound healing," Dr. Yee said. "When the basement membrane is left on, there is not as much scarring. The key factor in the early reports on LASEK is that when the basement membrane was present, the risk of developing haze is less.