PAUSE FOR THOUGHT

The seemingly inexorable rise of femtosecond laser-assisted cataract surgery (FLACS) seems to owe more to the powerful marketing potential of laser surgery than to any proven benefit to the patient in terms of surgical outcomes, according to Rupert Menapace MD, FEBO.

“Laser surgery is a big seller and it is easy to convince the patient of the magic of laser cataract surgery. Skilled manual surgery with modern instrumentation is as good as femtosecond laser-assisted cataract surgery. It saves lots of money and preserves the independence of the surgeon. It is not only ethically correct but also simply fair to inform the patient about the facts when discussing the option of femto-laser cataract,” Dr Menapace told delegates attending the JCRS Symposium at the XXXI Congress of the ESCRS in Amsterdam.

The key questions which need to be answered in relation to FLACS, added Dr Menapace, are whether it is more effective and safer than manual surgery and, if so, whether it is worth the additional cost.

While not minimising the capability of the femtosecond laser to create perfect corneal cuts of any desired architecture and location, Dr Menapace noted that modern ultrathin steel microkeratomes can also create excellent incisions in a variety of geometries.

“The differences in incision quality, if at all present, are marginal and will be nullified by oar locking and distension of the incision due to manipulation of the phaco and i&A probes and the lens injector tip during IOL insertion. In fact a recent study found exactly the same topographical changes with 2.75mm clear corneal incisions made with a steel blade and a femtosecond laser,” he said.

The perfectly-shaped capsulotomies created by the femtosecond laser are often cited as a major advantage over manual techniques, but the key issue is actually the centration of the capsulotomy to guarantee circumferential capsule-optic overlap, said Dr Menapace.

“The larger the capsulotomy the more precisely it must coincide with the anatomical centre of the capsular bag. This, however, is still a guess since the imaging tools of lasers cannot reach out to the lens equator. The centre of the limbus or pupil or even visual axis can considerably deviate from the anatomical centre of the lens. Using these features as landmarks can be very misleading. A capsulotomy, even when perfectly shaped, misses its target when not perfectly concentric with the IOL optic,” he said.

By contrast, simple and straightforward techniques exist to ensure proper sizing and centration of a manual capsulorhexis, said Dr Menapace, adding that this can be achieved by simply following a circle mirrored in the surgical microscope. Likewise, secondary capsulorhexis reshaping is possible using a manual approach in situations where a large eye or an extremely wide pupil make judgement of the correct size and centration difficult, he added.

For cataract removal, femtosecond lasers can pre-fragment the nucleus and save phaco time and ultrasound energy, said Dr Menapace, but the key benefits stop there.

“The laser must stop at least 1.0mm above the posterior capsule as a safety distance to avoid inadvertently cutting into it and it does not create a groove. The resulting posterior hinge and the difficulty to insert the phaco tip and spatula between the closely attached sectors make cracking of the nucleus more difficult. Alternatively cutting the central lens material in small cubes may cause them to spin off and be difficult to visualise and retrieve when they settle in the chamber angle or ciliary sulcus,” he said.

The femtosecond laser is also redundant when it comes to extremely hard black cataracts since the laser cannot penetrate into the deeper layers, added Dr Menapace. Cortical clean-up is also rendered more complicated by using the femtosecond laser, he said.

In terms of safety, Dr Menapace said while the femtosecond laser can create clear corneal incisions, its inability to create limbal or posterior limbal incisions limits its utility.

“Both limbal and posterior limbal incisions have been shown to be significantly superior to clear corneal incisions with regard to astigmatic neutrality and deformation stability. While a 3.0mm clear corneal incision still induces significant sectorial flattening, a posterior limbal incision does not up to a width of 4.0mm. Because of the reduced self-sealing ability and deformation stability, the use of clear corneal instead of scleral corneal incisions increases the risk of endophthalmitis to a similar extent as when not using intracameral cefuroxime prophylaxis,” he said.

While femtosecond lasers can reduce phaco energy and ultrasound power consumption, studies thus far have failed to demonstrate a concomitant reduction in endothelial cell loss, said Dr Menapace.

Improvement of refractive outcomes with the femtosecond laser has also not been corroborated by independent studies nor has it been shown to reduce the incidence of posterior capsule opacification, added Dr Menapace.

The expense of femtosecond laser technology should also give surgeons pause for thought, he said.

Rupert Menapace: rupert.menapace@meduniwien.ac.at