Laser enables fast ablation; increases safety, efficacy

October 1, 2009

New excimer laser affords a safe, controllable, efficient procedure.

Alicante, Spain-A new excimer laser (Amaris, Schwind eye-tech-solutions) affords a very safe, controllable, and efficient procedure, according to one physician. The sixth-generation model is the laser of choice for the treatment of refractive defects associated with presbyopia at any level, he said.

"In my opinion, excimer laser surgery is the best way to correct up to 10 D of myopia, up to 7 D of hyperopia, and up to 6 D of astigmatism using the . . . laser," said Jorge L. Alió, MD, PhD, chairman and medical director of VISSUM Instituto Oftalmologichari, Alicante, Spain.

"In the patients I have treated to date, only 3% required a re-treatment," he added.

Postoperative results

At follow-up, results showed that postoperative uncorrected vision of 20/20 or better was achieved in 65% of the eyes with moderate myopia; in 100% of those eyes, the visual acuity increased to 20/40 or better (average, 20/20). Postoperative uncorrected visual acuity (UCVA) of 20/20 or better was achieved in 25% of eyes with high myopia, and in 100% of those eyes, the visual acuity increased to 20/40 or better (average 20/25). Also, postoperative UCVA of 20/20 or better was achieved in 33% of eyes with hyperopia, and in 100% of those eyes, the visual acuity was increased to 20/40 or better (average, 20/25).

According to Dr. Alió, the predictability of the target refraction also was very good. At the 1-month follow-up of these patients, 91% of moderately myopic eyes were in the range of ±0.5 D (average, 0.06 D), 100% of highly myopic eyes were in the range of ±0.5 D (0 D), and 92% of hypermyopic eyes were in the range of ±0.05 D (average, –0.18 D). These results were reached without the use of individual nomograms.

None of the patients experienced any intraoperative complications, and only one eye was reported as having very mild epithelial in-growth, which later demonstrated total regression. No other complications were seen at the follow-up.

Several uses

The laser primarily was developed for refractive surgery and is geared to treat nearsightedness, farsightedness, and astigmatism effectively. It also is useful in the treatment of healed corneal ulcers as well as corneal glaucoma, however, according to Dr. Alió.

One of the major advantages of the laser, he said, is its ability to monitor the operational procedure using its integrated online pachymetry function. This function allows the eye surgeon to monitor every step of the corneal tissue ablation process carefully by showing even the smallest changes of the stromal thickness in real time. Using this advanced interactive software, the laser allows for customized treatments.

"Centration is one of the central issues involved in high hyperopia and in moderate presbyopia," Dr. Alió said. "The . . . laser has 5° of control on the centration of the ablation area, based either on the pupil, in the cornea vertex, or on any other target area that you select."

Unique feature

The laser also sets itself apart from other devices with its unique control of the energy adjusting the thermal interference with corneal tissue, he said. This characteristic allows for a minimal biologic response based on the thermal control that the laser provides. The less biologic interaction there is with corneal tissue, the more precise the procedure, Dr. Alió said.

"Minimizing the trauma to the corneal tissue allows for a better, quicker, and more reliable wound-healing process. This is one of the reasons that the patients achieve such good visual acuity only a day after the procedure-much better than what they would achieve when using glasses or contact lenses," he said. "Patients who could see 90% before the procedure can see 110% or 120% only a day following the procedure."

The unique thermal control technology and the control of ablation is one of the cornerstone strengths of the laser, using the synergistic effects of its 500-Hz pulse frequency coupled with two automatically adjusted fluence values, Dr. Alió said. Approximately 80% of the ablation procedure is performed with a high fluence value; for the remaining 20%, the laser automatically switches to the low fluence, smoothing out the cornea.

The longer a laser operation takes, the higher the risk of complications. Extended ablation time can cause the cornea to dry out, which could lead to over-corrections in the cornea. A higher-speed laser that reduces procedure time, therefore, is a much-desired commodity in refractive surgery, because it increases the safety of the procedure, he said. The optimized pulse duration found in this laser enables a fast ablation (about 4 seconds per diopter) and subsequently keeps the generation of corneal aggression to a minimum, thereby increasing the safety and efficacy of the laser procedure, Dr. Alió added.

"I have been using the . . . laser already in all types of refractive errors, including corneal wavefront-guided correction of irregular corneas. This is the best laser I have used; it is faster, and it appears to be more reliable in terms of centration and tracking," Dr. Alió said. "The . . . laser offers more precision at all levels, leading to better outcomes, and [is] a state-of-the-art technology that allows eye surgeons to correct refractive errors optimally."