Epi-LASEK aims to minimize drawbacks of LASEK and epi-LASIK

The use of alcohol enhances the quality of the epikeratome cut, according to the surgeon who first introduced LASEK.

A novel technique combines the reciprocal benefits of LASEK and epi-LASIK, improving the results and minimizing the drawbacks of both procedures.

“I named the procedure epi-LASEK because I use alcohol as well as the epikeratome to separate the epithelium from the underlying stroma,” said Massimo Camellin, MD, who first introduced LASEK and the idea of creating an epithelial flap to protect the cornea after surface ablation.

Technically, LASEK and epi-LASIK differ because of the way the epithelial flap is created. The first procedure uses a 20% alcohol solution and manual scraping, whereas epi-LASIK utilizes a mechanical device.

Under the surface, there are subtle anatomical differences between the two procedures.

Although the alcohol delamination of LASEK breaks the hemidesmosomes that join the two layers of the basal membrane — the lamina lucida and lamina densa — the epi-LASIK cut separates the whole basal membrane from the Bowman’s layer.

“The subtle layer of lamina densa that covers the Bowman’s determines the superior quality of the stromal surface obtained in LASEK because the lamina densa is smoother than the Bowman’s,” Dr. Camellin said.

However, epi-LASIK was developed to avoid the cellular damage produced by the alcohol on the epithelium, enhancing the quality and viability of epithelial flaps.

Dr. Camellin welcomed this new development as a potential improvement of his technique and used it in several patients.

“However, I found that a weak point of epi-LASIK was the high risk of damage at hinge level. As the epikeratome reaches the nasal quadrant, it tends to tear the epithelium, and you often end up with free caps, which substantially turn epi-LASIK into PRK,” he said.

In addition, by comparing the postoperative results of his LASEK and epi-LASIK patients, Dr. Camellin found that the use of alcohol has little or no influence on the results.

“What is important is the presence and not the viability of the epithelial flap because, whether it is beautifully preserved or not, the flap is slowly replaced by a new epithelium after the procedure,” he said.

Pros and cons

In 67 patients, Dr. Camellin performed LASEK in one eye and epi-LASIK in the contralateral eye.

Three patients in which the flap was lost were excluded.

“I found no significant difference in terms of pain between the two eyes but a trend in favor of LASEK because the suction applied by the epikeratome does cause some discomfort,” he said.

In the epi-LASIK eyes, the flap was better in quality and easy to separate from the stroma, but problems at hinge level were frequent.

In the first 2 months after surgery, more astigmatism was found in the epi-LASIK eyes.

“It was in all cases a central astigmatism, which resolved within a couple of months. The impact of the epikeratome may have a role in this,” Dr. Camellin said.

No significant difference was found in terms of haze, although a slight increase in haze — around month 3 — was found in a minority of LASEK patients.

“It was a very mild, subclinical haze … possibly a delayed effect of the alcohol on the flap. However, they were only traces of a slight opacity that had no influence on visual outcomes,” he said.

Surface regularity was compared on the basis of the best-fit topographic irregularity index, using the Optikon topographer.

“In the central 4 mm, more irregularities were found in the epi-LASIK eyes in the first 2 months after surgery. The two curves overlapped after this period,” Dr. Camellin said.

The same results were found by wavefront analysis.

“Again, the impact of the epikeratome may produce some irregularities, particularly in corneas with progressed small injuries,” he said.

Techniques merge into epi-LASEK

Further improvement can be achieved by combining the positive aspects of both techniques, Dr. Camellin said.

“What I did may look like a contradiction because epi-LASIK was developed with the aim of eliminating the use of alcohol. But since I found that the damage produced by it is more theoretical than substantial and the advantages more substantial than we thought at first, I decided to soak the cornea in 20% alcohol solution for 20 seconds, as I did with LASEK, and then perform the epikeratome cut,” he said.

The aim of the new epi-LASEK is to obtain the separation of lamina lucida and lamina densa.

“Once the alcohol has loosened the joints (the hemidesmosomes) between the two, the epikeratome cut will automatically be directed through this locus minoris resistentiae, in between these two layers. We’ll obtain the best, easiest and smoothest separation of the epithelium, overcoming also the hinge problems, which were the weakest point of epi-LASIK,” Dr. Camellin said.

Study confirms advantages

In a prospective study, Dr. Camellin compared the results of 45 patients in which one eye was treated with epi-LASIK and the other eye with epi-LASEK.

Epi-LASEK showed significant advantages in all parameters.

Astigmatism was significantly less in the first 2 months. The stromal surface was more regular because of the smoother layer of lamina densa covering the Bowman’s layer. Flap quality was better at hinge level because the alcohol solution soaks up the cells, making the epithelium thicker, more elastic and, therefore, more resistant to the impact of the separator.

“We obtain very beautiful, large hinges and no free caps at all,” Dr. Camellin said.

No statistically significant difference in pain was found between the two techniques because the alcohol does not cause pain. If some discomfort was experienced, it was because of the suction, he said.

Uncorrected visual acuity was slightly better with epi-LASEK in the first month, after which results were comparable.

No significant difference was found in haze formation, “which confirms that alcohol is not in itself a cause of haze. Alcoholic disepithelialization, with the manual scraping, was more likely to be the cause of the mild, late-onset haze that appeared in some LASEK eyes at around 3 months,” Dr. Camellin said.

With epi-LASEK, the advantages of the alcohol and the advantages of the mechanical cut are integrated and give the best results for a safe, pain-free and haze-free surface ablation, he said. – by Michela Cimberle

Reference:

• Camellin M, Wyler D. Epi-LASIK versus epi-LASEK. J Refract Surg. 2008;24(1):S57-63.

• Massimo Camellin, MD, can be reached at Sekal Microchirurgia Rovigo, Via Dunant 10, Rovigo 45100, Italy; 39-0425 411357/419032; e-mail: cammas@tin.it.