Upgrades and Advances In Femto and Excimer Lasers

New algorithms and procedures are making outcomes more precise.

By Robert Murphy

Upgrades and advances to excimer and femtosecond lasers arrive so swiftly, surgeons, seemingly, have just enough time to get used to one version before a new, improved one comes along.

Refractive and cataract surgery remain lucrative enterprises for many practices. Laser manufacturers may cast a cautious eye on a market in which growth is hard to predict, but as surgeons rack up better-than-ever visual results after both refractive and cataract surgery, there's a good chance manufacturers can count on patients to keep walking through the door.

What follows is a brief overview of excimer and femtosecond lasers on the US market. There may be some overlap in product capabilities, but many systems claim features all their own.

Bausch + Lomb/Technolas Perfect Vision

The Victus femtosecond platform, a joint venture of Bausch + Lomb and Munich-based Technolas Perfect Vision (TPV), received FDA clearance in August. What's notable about Victus is that it supports both cataract and refractive procedures in a single platform, according to the companies. B+L and TPV signed a definitive agreement in September 2011 that would allow B+L to acquire TPV.

In the United States, Victus is cleared for creation of a corneal flap in patients undergoing LASIK surgery or other treatment requiring initial lamellar resection of the cornea, and anterior capsulotomy during cataract surgery. In Europe, the Victus plat-form is additionally approved for the Intracor procedure — an intrastromal approach that changes the corneal curvature slightly while leaving the epithelium and Bowman's membrane intact — as well as lens fragmentation and arcuate incisions. B+L says it plans to submit additional indications to the FDA.

Supracor, a LASIK-based procedure that draws on the European experience with Intracor, performed on the Technolas 217P Excimer laser, received approval in Europe last year. The procedure can treat a wide range of presbyopic patients, and may also be suitable for those who have previously undergone LASIK. In a multicenter European trial, Supracor was found to provide a significant improvement in uncorrected near vision while maintaining good distance vision, with a high level of patient satisfaction. “Supracor is the biggest step in presbyopia LASIK development in the past eight years,” according to lead investigator Jean-Jacques Chaubard, MD, of Nice, France.

In 2011 the FDA also approved TPV's Zyoptix Advanced Nomogram for custom LASIK. Using the Advanced Nomogram when performing custom LASIK with the Technolas 217z100 laser improves visual outcomes over non-custom modalities and reduces the need for a second enhancement procedure, according to TPV. The Advanced Nomogram was developed in collaboration with the Center for Visual Science, at the University of Rochester Flaum Eye Institute under the direction of Scott M. MacRae, MD. “The results achieved using the Advanced Nomogram set a new vision quality and accuracy benchmark in LASIK surgery in the United States,” according to Dr. MacRae.

The Ziemer Z6 Power Plus system.

Ziemer Ophthalmology

Have you checked out the Ziemer Z Model femtosecond lasers? Introduced in March, the Z Models use the same low-pulse energy, high-pulse-repetition rate and short-pulse width of Ziemer's earlier LDV and Crystal Line models. By laying down a pattern of small, but overlapping, low-energy laser spots, the Ziemer lasers achieve clean tissue resection without injecting large amounts of energy locally into the cornea. For LASIK, this means flaps that are very easy to lift, faster visual acuity recovery and quieter eyes post-surgery.

The new Ziemer lasers have more capabilities than the LDV and Crystal Line models. The Z Models are a family of femtosecond lasers offering a range of uses, from simple LASIK flap creation to advanced corneal surgery. The Z2 performs essentially the same LASIK flap procedures as the earlier Crystal Line, but does so with a larger display and more user-friendly graphical user interface.

The Z4 has all of the features of the Z2, but also has Z-axis capability. This means the software can vary the depth of the laser spot within the tissue over a wide range. It is indicated for creating custom flaps for LASIK, including different edge-cut configurations and oval as well as round flaps. The Z4 can also be used to create precise channels for intrastromal rings and precise intracorneal pockets for the installation of the new presbyopia implants that will be entering the United States in the next few years.

The Ziemer Z6 Power Plus laser can do everything the Z4 can do, but with the added ability to perform lamellar and penetrating keratoplasties. Its more powerful laser cavity means that it can penetrate even heavily scarred corneas. Z Models allow full upgradeability between models. Surgeons can purchase a Z2 now and upgrade to Z4 or Z6 as their need to perform more procedures grows. In 2013, the capabilities of the Z Models will grow even more, as Ziemer says it will add features to perform all of the procedures required for femto-cataract.

Alcon Laboratories

Alcon's Wavelight Refractive Suite includes the EX500 excimer laser and the FS200 femtosecond laser. It also includes the WaveNet computer network, allowing for transfer of patient data through diagnostic devices, the excimer laser and the femtosecond laser. The suite is said to produce faster treatment times and optimal outcomes, according to company literature.

The EX500 Excimer Laser is reported to provide treatment times of 1.4 seconds per diopter with a 1050 Hz-type eye tracker, synchronized at 500 Hz, and a latency time of 2 milliseconds.

The FS200 femtosecond laser creates a flap within about six seconds. Its Balanced Beam Control calibrates each applanation cone to eliminate the variance in glass thickness and temperature shifts in the internal components for precision and consistency. The FS200 femtosecond laser also offers advanced applications such as intracorneal rings and penetrating or perforating keratoplasty.

The femtosecond laser offers other features, including automated vacuum control of the patient interface for consistent suction, minimal IOP and ocular distortion during suction and speedy visual recovery. The operator can make use of adjustable hinge positions and sizes, and variable side-cut angles, flap sizes and shapes. The FS200 femtosecond laser combines a small focus with low pulse energy to create accurate flaps. It enables sharp cutting edges, smooth stromal beds, easy-to-lift flaps, and minimal opaque bubble layers.

Alcon's wavefront-optimized WaveLight Allegreto Wave Eye-Q lasers account for the unique curvature of the eye, improving visual quality and treating spherical aberrations. Wavefront-optimized treatment maintains the cornea's natural asphericity. The WaveLight PerfectPulse technology sends additional pulses to the corneal periphery to compensate for energy loss and to address ovalization or a decrease in the laser beam's fluence. This provides nearly a 100% optical zone and a minimal transition zone.

PerfectPulse technology ensures that every laser pulse is controlled from its generation to the point where it contacts the cornea. High-speed eye tracking follows the eye's fastest movements to ensure accurate pulse placement. The laser's Gaussian beam profile produces a smooth ablation without grooves or ridges. The small 0.68-mm spot size creates a precise ablation of corneal tissue and small transition zones.

Carl Zeiss Meditec

Carl Zeiss Meditec's (CZM) MEL 80 excimer laser is said to be fast enough to reduce procedure time for greater patient comfort. Brief stromal exposure time means faster visual recovery. An 0.7-mm spot size allows for fine corrections while maintaining a smooth ablation. The unit comes with two wavefront-optimized ablation profiles from which to choose. An active eye tracker and a rapid infrared camera that captures both the pupil and limbus provide exact positioning during treatment, according to company literature.

VisuMax is said to deliver optimal precision, performance and patient care. Currently cleared for making corneal flaps as well as for lamellar and penetrating keratoplasty for corneal transplantations, VisuMax provides the platform for ReLEx smile, the first small-incision, singlestep and all-femto vision correction method launched internationally in September 2011. Earlier this year the FDA granted conditional approval for a US clinical trial of the ReLEx smile procedure.

The ReLEx smile technique combines femtosecond laser technology and precise lenticule extraction for minimally invasive laser vision correction. The ReLEx smile method generates a refractive lenticule in the intact cornea with the femtosecond laser. The surgeon then removes the lenticule through a <4-mm incision. The VisuMax features accurate beam guidance and creates a finely balanced interaction between the repetition rate and the laser pulse energy. The VisuMax has a laser pulse rate of 500 kHz.

Abbott Medical Optics

Abbott Medical Optics' (AMO) iFS femtosecond laser — the fifth-generation IntraLase unit — recently obtained FDA clearance to create arcuate incisions in corneal surgery including cataract procedures, according to company literature.

Factors such as placement, length, depth and radius of curvature can influence a surgeon's desired corneal modification. These variables can be difficult to control with traditional incisions made by hand with a surgical knife. The iFS Femtosecond unit allows for arcuate incisions that are precise, predictable and customized.

The fourth-generation IntraLase FS Laser System from which the iFS evolved delivers 60 kHz performance for equivalent microkeratome speed and laser precision. Among the benefits of the result is enhanced biomechanical stability compared with that of a microkeratome. The laser can achieve lower induced higher-order aberrations and better refractive outcomes.

The Visumax by Carl Zeiss Meditec.

The fourth-generation IntraLase FS Laser System from which the iFS evolved delivers 60 kHz performance for equivalent microkeratome speed and laser precision. Among the benefits of the result is enhanced biomechanical stability compared with that of a microkeratome. The laser can achieve lower induced higher-order aberrations and better refractive outcomes.

The iFS is said to create biomechnically superior flaps. That's important, because maintaining the cornea's biomechanical integrity is a critical component in any refractive procedure's success. The iFS femtosecond laser allows for greater control over flap diameter, depth, centration, and morphology.

These factors can lead to numerous advantages. One is a well-controlled flap structure. Another is uniform flap thickness. Ultimately, patients enjoy superior visual outcomes, with rapid visual recovery and a better quality of vision.

AMO's iFS femtosecond laser offers surgeons many options. They may create straight, angled and arcuate incisions in the cornea. Surgeons can create multiplanar custom incisions with hermetic sealing properties requiring less suture tension. Lower suture tension may induce reduced astigmatism, even as multiplanar custom incisions yield a larger wound surface promoting stronger healing. In some cases, laser resectioning brings more rapid healing. Early suture removal promotes rapid visual recovery.

AMO combines its iFS femtosecond laser with the Advanced CustomVue procedure. The Star S4 IR excimer laser system integrates data collected by the WaveScan Wavefront System, and uses these data to deliver precision custom ablations.

With variable spot-scanning, variable beam sizes from 0.65 mm up to 6.5 mm can be scanned over the treatment area and delivers treatment at varying repetition rates. An active eye tracking system captures the three dimensions of intraoperative eye movement. The ActiveTrak automatic centering locates and then sets the treatment center to the pupil's center.

The Visx WaveScan Wavefront System deserves mention. AMO's Fourier wavefront upgrade can capture and treat wavefront information on larger-pupil patients and use this data for optical zone treatments out to 7 mm. Transition zones are adjustable out to 9.5 mm. The WaveScan system uses the patient's keratomotry values and wavefront measurement to create an optimal corneal shape for each patient.

AMO's iFS femtosecond laser.

Nidek

Nidek's EC-5000 CX III excimer laser features innovative scanning technology for precise and uniform surface ablations. It can automatically calculate and continuously monitor the laser delivery parameters. A 200 Hz active eye tracker has no minimum pupil diameter. Outcomes data has shown a low rate of surgical enhancements with the device. Features such as a 3D joystick, enhanced illumination and accurate aiming beams promote precise control of the laser beam delivery arm.

The Quest Excimer Laser System features numerous parts. The “NavFocus” feature uses a 1 kHz eye-tracking system with highspeed digital image processing to follow the patient's eye. An offset function allows the surgeon to set the tracking point within +1 mm from the pupil center. This reportedly greatly improves the alignment speed. The Quest excimer laser also has a mechanism for torsion-error control. This mechanism is meant to detect and compensate for cyclo-torsion and improve cylinder-correction accuracy while ensuring that the Quest ablates the eye precisely. Motorized magnification controls allow the surgeon easily to the change the magnification.

The Final Fit Software receives the data from the OPD-Scan II (K readings, topography) and then simulates a postoperative corneal shape and overall refraction. The Final Fit Software evaluates and then converts the OPD-Scan II's refractive and topographic data to produce custom ablation parameters.

These algorithms help to enable multiple, simultaneous, and localized ablations to correct higher-order optical aberrations, corneal irregularities and decentered ablations.

Keep an Eye on the Market

Whether you're already set up with suitable excimer and femtosecond lasers or are ready to plunge into these surgical arenas, it makes sense to keep an eye on the market now and then.

Any major conference features a full complement of manufacturers eager to explain their unit's latest upgrades. Also look for hands-on workshops. There's nothing like holding an instrument in your hands to get a sense of its ergonomic and practical utility.

Ask your clinical colleagues about their experiences with a certain laser system. A trusted friend will give it to you straight. Do your homework before making this sort of investment. There are plenty of high-quality products out there to make the investment a good one. OM

Robert Murphy is a freelance medical journalist in Philadelphia.