Comparison of Commercially Available Femtosecond Lasers in Refractive Surgery

Glauco Reggiani-Mello; Ronald R Krueger

Disclosures

Expert Rev Ophthalmol. 2011;6(1):55-65. 

In This Article

Commercially Available Devices

Following the introduction of this new field by IntraLase, three additional systems have become commercially available in the last few years: Femtec, Visumax and LDV. The newest device to be released is the UltraFlap FS 200 from Alcon (Figure 2).

Figure 2.

Commercially available femtosecond lasers for refractive surgery.

The success achieved by IntraLase inspired the other companies to research different approaches and applications of the promising femtosecond technology. New refinements are being systematically released with improvements in pulse rate, spot size, pulse energy and customized approaches for the use of the laser.

This competition has compelled the further development of this technology. The Femtec laser works with a similar pulse rate and energy as the IntraLase, but uses a curved applanation docking system, which promises less intraocular pressure (IOP) increase in a more physiologic interface between the eye and the laser. In addition, a new procedure for presbyopia called IntraCor[5] is being studied with this platform.

Visumax has a curved docking system, such as the Technolas laser, but uses a limbal suction mechanism compared with the standard conjunctival suction (Figure 3). The company has recently upgraded its laser to a 500-KHz pulse rate to be used together with a lower pulse energy profile, in the submicrojoule range. Furthermore, the company is investigating femtosecond-only refractive surgical procedures, femtosecond lenticular extraction (FLEx) and small-incision lenticular extraction (SmILE) in which a lenticule of stromal tissue is cut with the laser and pulled out manually. The first results are promising.[6,7]

Figure 3.

Visumax and Femtec curved docking systems. (A) Visumax and (B) Femtec curved docking systems. Note the limbal suction in the Visumax device.

The LDV from Ziemer is a smaller, portable device with some uniquely different characteristics. It operates at a very high pulse rate (in the MHz range) with very low pulse energy (in the nanojoules range), which, according to the manufacturer, produces a smoother bed with considerably less bubble formation (Figure 4). However, there are no vertical side cuts with this system, so the flap-making approach is similar to a microkeratome with a tapered flap edge. Other limitations of this system are that the procedure is not directly visible during the application of pulses, and there is a need for an interface fluid (viscoelastic substance). Since there is no vertical cut when using this device, the nonapplanated periphery establishes a tapered edge to the horizontally cut flap, which can be irregular if air is present.

Figure 4.

Different cutting profiles between high-energy and lower energy devices.

The new WaveLight FS200 UltraFlap laser from Alcon is newly available for evaluation, and its technical specifications show similarities to the IntraLase system. Initial studies show similar IOP rise pattern compared with IntraLase, with a flat applanation docking system.[8] Less opaque bubble layer (OBL) formation is expected owing to a new laser profile that creates specific cutting geometries (externalized channels) in the cornea to allow the gas bubbles to diffuse out of the relevant regions of the cornea. This can allow an immediate excimer ablation after femtosecond flap creation in the majority of cases.

IntraLase has also progressively refined its system, releasing new updates on a regular basis, being now in the fifth generation. There have been changes in the laser pulse rate (from 15–30 to 60–150 KHz), allowing faster procedures, an increase in side cut angle (>90°, allowing inverted bevel-in edge), increased geometry of cuts (allowing intrastromal corneal ring placement and shaped corneal transplants) and additional small changes in laser parameters.[101] Despite these changes, the same successful core structure of the device was maintained and its main characteristics were never lost.

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