Surface ablation gets high marks at LASEK meeting

Highlights of the international LASEK congress included discussion on corneal haze and night vision.

CLEVELAND – Laser epithelial keratomileusis is a promising technique, but the pitfalls of older surface ablation techniques, such as corneal haze, are still an issue, according to surgeons who gathered here.

The occasion was the International Congress on LASEK and Advanced Surface Ablation, which drew surgeons from several continents to discuss LASEK, a procedure that combines elements of LASIK and photorefractive keratectomy (PRK).

Topics of discussion included whether or not to replace the epithelial sheet, what instruments work best and what surgical variations offer the most promising results. The meeting reports below originally appeared on the OSN SuperSite during the meeting.

Replace or not?

Should the epithelial sheet be replaced on the cornea after surface ablation? This question was debated by refractive surgeons during a round table discussion here.

Most refractive surgeons who perform LASEK prefer to try to rehabilitate the epithelial layer rather than remove and dispose of it after LASEK. However, debate continues about what is the best procedure.

“The more tissue that remains, the more stable the cornea is going to be,” Raymond A. Applegate, OD, PhD, told attendees.

Thomas Claringbold, DO, agreed. “I like pulling the epithelial layer back over the cornea after LASEK — whether it’s alive or dead — because it protects the eye,” he said.

“There is benefit in putting the flap on as best you can,” added Massimo Camellin, MD, the surgeon who described and popularized the LASEK technique. Dr. Camellin said he replaces the epithelial layer of all his patients after LASEK. After replacing the flap, he seals it in place with a contact lens to prevent shifting and aid wound healing.

“Even if the epithelial cells are dead, they can still help to regenerate a new series of cells. They will help to rebuild a healthy cornea,” he said.

Vikentia J. Katsanevaki, MD, took the opposing view, saying dead cells could actually impede healthy growth.

“The dead cells could stand as barriers to cell growth, altering the natural biological state,” she said.

Dead epithelial cells could further inhibit healing of the cornea by releasing toxins, she said.

“I question the quality of wound healing where there are dead cells intact,” agreed panel moderator Richard W. Yee, MD. Wound healing can be slower when dead cells are present, he said.

José Matos, MD, elaborated. “The vitality of the epithelium has a lot to do with the comfort patients have after LASEK. When the epithelium is healthier, wound healing is better and patients are happier,” Dr. Matos said.

Dr. Yee said he noted good results in LASEK patients who had their mostly healthy epithelial cells salvaged after surgery. However, he said, each LASEK case — depending on the health of the epithelial layer after surgery — should be approached individually.

“There is a time and a place for each type of method,” he said. “We still have a lot of work to do before we can truly determine which method is most conducive to successful surgical outcomes.”

Corneal haze risk

Significant corneal haze may occur after LASEK , according to a poster presentation here.

“Despite being effective, LASEK is a challenging procedure,” said Maria Regina Chalita, MD.

Dr. Chalita described a retrospective study that included 20 eyes of 14 patients who underwent LASEK. At 1 month, 94% of the patients achieved vision of 20/40 or better. At 3 months, 100% of patients achieved 20/40 or better, and at 6 months 91% achieved that level.

At 1 month after surgery, corneal haze of grade 0.5 was reported in 35% of patients, of grade 1 in 2% and of grade 2 in 5% of patients. At 3 months after LASEK, the level of haze had increased, with 62% of patients demonstrating grade 0.5 haze and 31% grade 1. At 6 months postop, grade 0.5 haze was present in 58% of patients, grade 1 in 25% and grade 2 in 8% of patients.

“Creating the epithelial flap is not simple. This may have contributed to the high haze incidence in our study,” Dr. Chalita said.

She suggested that the haze could have been induced by the administration at 1 month of fluorometholone acetate.

LASEK and night vision

LASEK was found to induce fewer “starburst” phenomena than LASIK in another study discussed here.

Bruce Larson, MD, of Loyola University in Chicago, reported the outcomes of a study comparing visual disturbances in patients after LASIK vs. LASEK.

Dr. Larson, a LASIK patient himself, has had a personal interest in starbursts since he started experiencing them in 1999.

“I would see varying sizes of these effects around bright lights at nighttime,” he said. “I realized that if I had them, there were probably a lot more people with them, too.”

To determine how severe the starburst phenomenon was in post-LASIK patients, Dr. Larson developed a device he calls a glareometer.

“The glareometer tests for starbursts and grades the severity of the glare,” Dr. Larson said. “It’s an effective way to quantify these night effects.”

After testing a number of LASIK patients in his practice with the homemade device, Dr. Larson said he was “shocked” to discover that most of them regularly saw starbursts.

“Ninety percent of my patients were testing positive for starburst phenomenon,” he said. Dr. Larson then tested a cohort of 45 myopic eyes that had undergone either LASIK or LASEK.

“Results showed that LASIK produced significantly more starbursts than LASEK, with a larger diameter for each effect,” Dr. Larson said. The size of the starbursts in LASIK patients, as measured by the glareometer, averaged 20 mm in radius, while LASEK patients’ starbursts averaged a 10.7 mm radius, he said.

Epithelial separator for LASEK

A microkeratome developed for use in LASEK is showing promise in animal studies, according to a poster presentation.

Frank A. Lattanzio, PhD, of Norfolk, Va., described the use of a subepithelial separator (SES) to create epithelial flaps in rabbit eyes. The purpose of the device is to reduce the surgeon learning curve in creation of epithelial flaps and to decrease flap variability, he reported.

The microkeratome — a plastic, oscillating blade — is driven at high frequency across the corneal epithelium. The epithelium is separated from the stroma without the need for the operator to position the blade to cut at an exact depth. According to Dr. Lattanzio’s poster, the plastic blade automatically adjusts for changes in epithelial cell depth.

Outcomes from long-term testing of corneal epithelial flap reattachment will determine whether the microkeratome will improve LASEK outcomes, the poster concluded.

The Zeus SES Microkeratome is in development for use in LASEK by CIBA Vision Ophthalmics.

LASIK pitfalls discussed

LASIK has the potential for complications that are not seen in other refractive procedures, including increased coma, keratectasia and surgeon-induced irregular flaps, according to a number of presenters.

Several surgeons described complications seen in LASIK but not in surface ablation procedures such as LASEK.

Dr. Applegate compared the amount of residual and induced aberrations following LASIK, LASEK and PRK in myopic patients. All three surgical procedures reduced second- and third-order aberrations postoperatively, but LASIK induced the most higher-order aberrations.

“The increase in coma for LASIK patients was significant,” Dr. Applegate said. Additionally, the study found that there was significantly more variability in the predictability of LASIK outcomes than the other refractive procedures.

Another complication of LASIK not seen in LASEK or PRK is keratectasia, said David Huang, MD.

“Keratectasia is a rare, but serious, complication of LASIK,” Dr. Huang said. The incidence of keratectasia in LASIK patients is about one case per 2,500 patients, he said.

Surgeons can reduce the incidence of keratectasia by following conservative guidelines, Dr. Huang said. This includes leaving adequate corneal stability by preserving a thickness of greater than 250 µm in the stromal layer.

“Ruling out forme fruste keratoconus by measuring with intraoperative pachymetry will also reduce your chances of a postop ‘surprise’ with keratectasia,” Dr. Huang added.

Flap irregularities are also unique to LASIK, the most common flap-based refractive procedure, Ronald R. Krueger, MD, said.

“Flap complications are common,” he said. “Most, like free caps, happen during surgery and can be corrected with appropriate methods.”

A free cap can be corrected by replacing the cap and sealing the cornea with a contact lens, he said. However, Dr. Krueger said, not all flap complications can be corrected definitively intraoperatively.

“We as surgeons must use proper planning to prevent all of these complications,” he said. “If we cannot resolve these challenges with LASIK, it leads us to question whether surface procedures, such as LASEK and PRK, will someday become more popular.”