While excimer lasers have ruled the roost for many years in corneal refractive surgery, new technologies are now emerging which may challenge their dominant position. This year's Winter Refractive Surgery Meeting will include reports of early results of LASIK and PRK using a new non-excimer solid-state laser.
The new Lasersoft (Katana Technologies GmbH) is a tuneable short-pulse, 210 nm wavelength, Q-switched, diode-pumped laser with a 0.25 mm flying spot and an ablation zone variable from 1.0 to 10.0 mm. The laser system is also fitted with an eye tracker working at a speed of more than 1 kHz, said Matteo Piovella MD, Monza, Italy, who will be presenting his findings at the meeting (Saturday, Super Vision III, 15:00-15:45).
"This laser applies less energy to the cornea, and thus in theory should induce less scarring. In addition, the very small spot size fits the present requirements for effective custom ablation. Other important features of the solid-state laser are its reduced dimensions and lower maintenance needs," he added.
In a study involving 16 eyes of 16 patients who underwent LASIK with the new laser to correct a mean refractive error of -3.3 D, the mean postoperative refraction at one month's follow-up was -0.2 D. In addition, mean uncorrected visual acuity was 0.7 and there were no postoperative complications.
Dr Piovella told EuroTimes that the Lasersoft system has several potential advantages over currently available excimer laser systems. For example, the system does not require the use of toxic excimer gases. It also provides better pulse-to-pulse stability of the energy due to the cw-diode pumping of the primary laser. Moreover, the system's 0.2 mm spot size permits higher precision and is saving corneal material.
"The real Gaussian beam profile gives precise ablation and a smooth surface after treatment. The 210 nm wavelength of the beam is closer to absorption peak of corneal collagen, which therefore reduces thermal effects and collateral damage. Furthermore the wavelength is not absorbed in air, water or tear fluid, thus the ablation process is less sensitive to humidity in the surgery room, no purging with inert gases is necessary, and even if the stromal bed is wet the ablation rate remains stable."
In another Italian study to be presented at the conference the laser appeared to produce very promising results in surface ablations for both hyperopia and myopia with or without astigmatism (Sunday, Surgery of High Myopia and High Hyperopia/ Hypermetropia, 08:00-10:30).
The study included 51 eyes of 29 patients. Thirty-seven eyes had –1.0 D to –9.0 D of myopia, with or without myopic astigmatism, 10 had +1.0 D to + 5.5 D of hyperopia, with or without hyperopic astigmatism, or four eyes had up to 4.4 D of mixed astigmatism, said Marco Rossi MD, Busto Arsizio, Italy.
All eyes underwent PRK with the new solid-state laser. At two weeks' follow-up, 61% of eyes affected by myopia and/or myopic astigmatism had a UCVA from 0.9 to 1.0, as did 50% of eyes affected by mixed astigmatism. In addition, 90% of eyes affected by hyperopia and/or hyperopic astigmatism had a BCVA of 0.9 to 1.0. Postoperative refraction ranged from -2.0 D to +0.5 D after 14 days.
Dr Rossi noted that the new laser appeared to be very gentle on the cornea. For example, temperature of corneal surface during surgery, as measured with an infrared camera, varied between 0.5° and 1.0° Celsius.
Confocal studies indicated little in the way of corneal inflammation postoperatively. In addition, evaluation of the corneas the day after surgery showed a normal re-epithelialisation speed and very homogeneous and transparent corneal surfaces, short pain and short inflammatory signs. No haze was found."PRK performed with the Lasersoft system gives good refractive results in short time both in myopic and in hyperopic group with short inflammatory sign and reduced pain. Longer follow up will be necessary to confirm the reliability in time. We plan to present four month results in Barcelona."
