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Femtosecond lasers take aim at cataracts

08 Dec 2010

With active developers on both sides of the Atlantic, the use of ultrafast pulses for cataract surgery has become a hot topic in ophthalmology.

In an ageing global population, the onset of cataracts is a challenge that many more people eventually have to deal with. The exact reasons why the eye's lens becomes cloudy and partially opaque as the years pass have been much studied, and no shortage of contributory factors have been identified: exposure to UV radiation, a hereditary predisposition, and the side-effects of other medical conditions are all thought to play a part.

The magnitude of the opportunity for suppliers of ultrafast lasers is evident from the market figures: according to industry analysts, more than 3 million cataract procedures are completed each year in the US alone.

Right now, cataract surgery involves removing the eye’s natural lens, usually leaving its surrounding elastic membrane or "capsule" in place, and replacing it with a synthetic intraocular lens (IOL), made from acrylic or silicone material. Once inside the capsule, the IOL restores something close to normal vision.

Doing so requires breaking up the existing lens in-situ, often using a tool equipped with a metal tip vibrating at ultrasonic rates. An initial small incision in the eye through to the lens, called a capsulotomy, opens up the capsule and allows the ultrasonic probe to be inserted. The ultrasonic vibration liquefies the lens which is then sucked or aspirated out. This is called phacoemulsification, and though effective, it is an aggressive procedure that can occasionally cause damage to the other sensitive structures in the vicinity and lead to future complications.

Opthalmologists are already familiar with the tool that could make the procedure more efficient, controllable and safe: a femtosecond laser.

In refractive eye surgery, femtosecond lasers were readily adopted as the best option to achieve accurate and reproducible incisions in the cornea in procedures such as LASIK. Now the same technology is coming to cataract surgery, with femtosecond sources used to make the incisions in the lens capsule, as well as help to fragment the old lens.

"Cataract surgery is one of the most routinely performed procedures worldwide," said Frieder Loesel, Chief Strategy Officer at Technolas Perfect Vision. "There have been great advances in the techniques and technology used to remove the cataract and in the manufacture of replacement intraocular lenses in recent decades, which makes the procedure safe and effective. Using a femtosecond laser to perform the key cataract steps including capsulotomy and lens fragmentation represents the latest advance in improving outcomes and safety still further."

It's all about control
The most hazardous parts of the procedure are cutting the window in the membrane of the lens prior to drilling it out and the subsequent lens removal - and a femtosecond laser could take care of that more accurately and with perfect reproducibility. As well as benefiting patient safety, the improved accuracy should help to ensure a successful outcome when used with more advanced multifocal, or "premium", IOLs.

Moving to femtosecond lasers also allows ophthalmologists to make precise incisions in the lens, and to exercise greater control over the process. A laser allows perfectly centered shapes and patterns to be cut into the existing lens with an accuracy beyond that possible with an ultrasound tool. Incising points of weakness into the lens in this manner makes it easier to get the old lens out, and helps achieve a more precise match between the new IOL and the existing capsule.

Technolas Perfect Vision, headquartered in Munich, already supplies a femtosecond workstation used for refractive surgery and LASIK procedures. Originally formed as a joint venture between Bausch + Lomb and 20/10 Perfect Vision, it sees incorporating the ability to carry out cataract surgery into its ophthalmology systems as the logical progression.

"The femtosecond CUSTOMLENS module can be incorporated into our current TECHNOLAS 520F system, or work as a standalone system," noted Loesel. "The workstation uses a solid-state femtosecond laser operating in the near infrared wavelength regime at around 1 micron. Pulse durations are around 500 femtoseconds, and depending on the individual steps of the procedure, pulse energies ranging from sub-microjoule to several microjoules are used."

According to Loesel, about 20 clinical cataract cases have been treated with this new procedure to date, and the clinical study work is ongoing.

International efforts
A trio of other developers are bringing femtosecond cataract surgery systems to market, all US-based and operating under the regulatory guidelines of the US Food and Drug Administration (FDA).

LensAR, Florida, has received FDA 510(k) clearance for use of its femtosecond system for anterior capsulotomy, as well as a US patent related to the use of femtosecond lasers as a means to increase the flexibility of the lens to facilitate lens removal. The LensAR system also incorporates propriety ocular measurement and 3D laser scanning technologies, used to assess the condition of the lens and to locate the incisions.

LenSx, California, was acquired in July 2010 by healthcare giant Alcon Labs in a deal reported to be worth $361.5 million in cash for LenSx shares, plus up to $382.5 million based upon future achievements and revenue milestones. The company has received FDA 510(k) clearance for use of its femtosecond laser in lens fragmentation, anterior capsulotomy and the creation of corneal incisions.

OptiMedica, also in California, has developed a cataract surgery system incorporating a pattern-scanning femtosecond laser, and uses OCT imaging to effectively determine the lens position before making an incision.

Building femtosecond sources into working surgical systems is only one part of the challenge; making equipment that fits into the daily work-flow of ophthalmology clinics without a substantial economic penalty is quite another. But, given the magnitude of the available market, Technolas' Loesel is confident that the goal is a worthwhile one:

"With 3.2 million cataract procedures being performed annually in the US alone, there is a huge market potential,” he said. “The femtosecond cataract procedure will initially be adopted in the premium cataract sector where premium lenses such as multifocal or accommodating lenses are implanted.”

“In the US, the most recent data reports that more than 13 per cent of all implanted IOLs were premium lenses. Internationally the number of premium IOLs is lower, but note that it's not only the premium IOL procedures that could benefit from a femtosecond laser procedure - all cataract cases do."

LensAR promotional video: lasers in cataract surgery

Doug Koch on the advantages of femtosecond lasers in cataract surgery

About the Author

Tim Hayes is a freelance science and technology journalist based in Bristol, UK.

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