A. John Kanellopoulos, MD, described his European experience with this laser at the annual meeting of the American Society of Cataract and Refractive Surgery. He is clinical clinical professor, New York University Medical School, New York, and director, Laservision Eye Institute, Athens, Greece.

Dr. Kanellopoulos and colleagues evaluated use of the laser in 385 eyes that were treated for myopic astigmatism or myopia. In all cases, the Moria M2 microkeratome (Moria, Antony, France) was used.

Dr. Kanellopoulos said that the laser has a gaus-sian-profile 0.9-mm fly-ing spot, with 200-Hz frequency and 250-Hz active eye tracker.

"All procedures per-formed were primary LASIK and non-wavefront-guided. As a rule, we overcorrected the scotopic pupil size with an ablation pattern at least 0.5 mm larger in diameter," he said. "Also as a general rule, we calculated that 280 ΅m of residual stromal bed was left following the ablation. Accordingly, the 110- and 130-΅m microkeratome heads were used, and the estimated flap thickness was 130 and 160 ΅m, respectively."

He explained that during the procedure, the following basic principles in surgical technique were observed: 1) strict standard temperature and humidity were maintained (19° to 21° C, 35% to 45% humidity); 2) minimal procedure time (the total procedure time never exceeded 8.5 minutes for any eye); 3) only two drops of topical anesthetic were used per eye; 4) the stromal bed was observed to be equally hydrated, by surgeon monitoring and intervention with Weck-cell sponge drying; 5) flap half-folding was practiced to minimize flap dehydration during ablation; and 6) strict flap repositioning accuracy was observed, with sponging of the repositioned flap with a moist Weck-cell sponge at the conclusion of the procedure.

Preop (top) and postop (bottom) wavefront maps. BCVA improved from 20/20 to 20/16. (Courtesy of A. John Kanellopoulos, MD)

Dr. Kanellopoulos reported that in this series of patients, the mean sphere was about 5 D (range, -1 to -12 D) and the cylinder was an average of 1.25 D (0.25 to 3.75 D). The uncorrected visual acuity (UCVA) improved nicely. The improvement in the mean best-corrected visual acuity (BCVA) from 20/25 to 20/15 was most impressive. At 3 months post-treatment, 87% of the eyes achieved 20/20, an "impressive" 47% 20/15, and 32% 20/10. All eyes were within ±0.75 D. There were no flap complications.

"Being in a new practice setting in Europe, I confirmed twice that the results were correct. The induced coma was only 35% (mean coma of 6% preoperatively to 9% postoperatively)," Dr. Kanellopoulos said. "The total high-order aberrations increased just 37%, which is a much smaller per-centage compared with a previous experience with LASIK and other instruments."

The results in this series, he noted, were consistent with the wavefront-guided results that he and his colleagues achieved in a group of 40 patients.

"The visual acuity results in those patients were the same as in the 385 patients, but with less higher-order aberrations," he said.

"This technique minimizes the induction of higher-order aberrations with the asphericity-preserving prolate laser software," he said. "The microkeratome provided a smooth, clear flap. The rapid-response eye tracking provided a well-centered ablation. We attempted to keep the time of the procedure to a minimum.

"We found that the procedure seems to provide safe and effective results," he said. "Even on the first postoperative day, the results were impressive, and we observed a significant increase in the BCVA, even with-out wavefront-guided ablations, using the software that is standard in the laser."

Additionally, he noted, it appears that the asphericity-preserving ablation software used with this laser results in very little high-order aberration and coma induction following LASIK, even in patients treated with non-wavefront-guided ablations. This excimer laser produces prolate ablations as a standard fea-ture. It "heats" up the periphery of its myopic ablations to reduce aberrations postoperatively.

"We theorize that this 'wavefront-friendly' software in the laser's ablation pattern is responsible for the impressive results in visual acuity postoperatively," he said. "This becomes possible with the attractive characteristics of this excimer laser: the gaussian- profile flying spot of very small size (0.9 mm), with the very high (200 Hz) frequency that minimizes procedure time and possible stromal dehydration effects on the postop wavefront, and the 250-Hz active eye-tracker that minimizes ablation decentration by responding to saccadic and accidental eye movement with an astounding 6- to 8-msec response time.

"The quality and consistency of the flaps we obtained with the M2 microkeratome should be highlighted as well," Dr. Kanellopoulos added. "We have found in clinical practice it is very helpful to customize flap size by using the four different-profile microkeratome rings to conform to preoperative corneal keratometry.