17 The Basics of Femtosecond Laser Cataract Surgery
The introduction of the femtosecond laser into cataract surgery has refined and improved a couple of steps like capsulotomy in an already very efficient and safe procedure, performed by phacoemulsification since the 1970s. Following Nagy’s first cataract operation with a femtosecond laser, different platforms have been developed. They employ varying docking procedures. Rise in intraocular pressure (IOP) is a major concern in the docking process. Such IOP spikes after using a flat applanating contact lens have been reported in early femtosecond lasers (those employed in corneal surgery). All current laser-assisted cataract surgery (LCS) systems perform intraoperative imaging—an approach different from the previous generation Er:YAG (Erbium-doped yttrium aluminum garnet) and Nd:YAG (neodymium-doped yttrium aluminum garnet) laser cataract systems that did not rely on imaging. Three of these current platforms use optical coherence tomography. The laser requires well-trained personnel and a room with enough space and constant temperature. Performing the laser “pretreatment” in the operating room is strongly recommended since transporting the patient from a special “laser suite” to the operating room is both time-consuming and questionable with regard to the required sterility. The femtosecond laser is, after all, a relatively new technology in cataract surgery and its potential for future development seems promising.
Keywords: Catalys, controlling, docking, Femto LDV, imaging, interface, intraocular pressure, laser suite, LensAR, LenSx, phacoemulsification, setting, staffing, Victus
When the femtosecond laser was—after its successful performance in corneal refractive procedures—introduced into cataract surgery, it was neither exactly the invention of the wheel nor was it immediately conceived as opening the door to a new era in ophthalmology. Unlike great milestones in medical progress like Jenner’s smallpox immunization or Fleming’s discovery of the first antibiotic, the femtosecond laser did not suddenly and to general relief fill a dreadful void. Nor did it present a breakthrough in a medical field that could offer only dire therapeutic options. The laser rather burst upon an ophthalmic subspecialty with a degree of surgical and functional success that would be the envy of most other invasive disciplines in modern-day medicine. Since the introduction of phacoemulsification by Charles Kelman, the advent of ever-smaller incisions that minimize both surgically induced astigmatism and the threat of infection and with a large variety of intraocular lenses (IOL), cataract surgery has more and more become a refractive method while fulfilling its traditional purpose as a vision-restoring procedure better than ever. Cataract surgery was already safe and highly effective, both in the industrialized world and in developing countries although in some of them there is unfortunately still a shortage of skilled surgeons, nurses, and facilities, which renders cataract still the Number One cause of blindness in the world. Cataract surgery was and still is the most frequently performed surgical procedure in the world—and will be in the foreseeable future with ever-increasing numbers. Currently, approximately 19 million cataract operations are performed worldwide each year, about 3 million of them in the United States and 700,000 in Germany per annum. With an unchecked global population increase and the demographic aging of most societies, the demand for cataract surgeons operating with the best possible equipment will continue to rise. The World Health Organization estimates that the number of annual cataract operations will increase to 32 million by the year 2020, as the number of people 65 years and older doubles worldwide between 2000 and 2020. 1
The introduction of a new technology into a medical field that is widely regarded as performing close to perfection seems like a risk, particularly if the new method is economically anything but a bargain. And yet, within the time span of just a few years, the femtosecond laser has become an established part of cataract surgery, predominantly if not exclusively so far in the industrialized world. Cataract surgeons live up to the conventional wisdom that the better is the enemy of good and many of them welcomed the new technology since there still is room for improvement in the 21st century version of one of humankind’s oldest invasive procedure. The reproducibility and the unparalleled precision of certain steps performed by the femtosecond laser—in particular that most crucial intervention, capsulotomy—have added a new dimension to cataract surgery—at least in the perception of the vast majority of those surgeons who have employed the new technology. It comes as no surprise that the most experienced high-volume laser-assisted cataract surgery (LCS) surgeons are excited about this new option without being uncritical toward the pitfalls and the yet unanswered questions of this technology. The authors of the following chapters are leaders in this field and are graciously sharing their experiences and their thoughts with this book’s readers. It is a rapidly developing field: there are now hundreds of articles, studies, and reviews in peer-reviewed journals as well as in other publications.
17.2 First Lasers in Cataract Surgery
Laser technology has been an integral part of ophthalmology for about half a century. In the posterior segment, lasers have been employed to treat different retinopathies as well as tears, lattice, and other alterations of the retina. In the anterior segment, a number of laser interventions have been established to treat glaucoma, from (argon) laser trabeculoplasty to suture lysis following trabeculectomy. There is, as Zoltan Nagy has pointed out, no tissue within the eye that cannot be treated with some type of laser. 2 For the general public and for patients, the term “laser” has a certain aura: of being less invasive, little pain, representing state-of-the-art technology and medicine—in every respect preferable to the “knife,” the classical symbol of surgery. The public’s craze for the laser—facilitated by ample media coverage in the age of early space exploration in the 1960s—did not spare cataract surgery. Around 1970, first attempts were made to use a laser for capsulotomy. One of the early challenges was to minimize damage to the surrounding tissue. An important breakthrough was the design of a Q-switched laser that delivered an extremely short duration of pulses and thus was able to minimize the thermal damage. One of the first reports described what was then called a laser phacopuncture in soft cataracts. 3
Over the next couple of years, a number of laser systems were tried in cataract surgery, but none of them was to last. The one exception is the therapeutic option that ever since has a place in the management of cataract patients though it is not employed in the operation itself but rather in coping with its most frequent unwanted side effect: the treatment of posterior capsular opacification with the neodymium-doped yttrium aluminum garnet (Nd:YAG) laser as first described by Aron-Rosa et al in 1980. 4 Less durable was, for instance, the Erbium-doped yttrium aluminum garnet (Er:YAG) laser, which was introduced into cataract surgery in 1993 and which was thought to be well suited for lens phacovaporization. 5 An Nd:YAG laser, Dodick Laser Photolysis Surgical System, marketed by ARC Laser Corp (Salt Lake City, UT) received Food and Drug Administration (FDA) marketing approval in July 2000. It was, however, not the almost noninvasive procedure that some patients associate with the term “laser.” During that intervention, a laser probe was inserted into the anterior chamber and the tip of the probe made contact with the lens. The shock waves disrupted this lens material at the mouth of the probe, and the fragmented material was aspirated. 6 Although these systems confirmed the fact that lasers could perform several steps of cataract surgery, their clinical utility was limited because they were inefficient in their delivery of laser energy and lens fragmentation. Excimer lasers, so revolutionary in the field of corneal refractive surgery, proved not to be effective in cataract surgery either.
The breakthrough for the laser in the treatment of the world’s leading cause of blindness and vision loss came with another technology that had already been employed very successfully in refractive surgery. For the first time, a femtosecond laser was used on a patient in a cataract operation by Zoltan Z. Nagy and his team at Semmelweis University in Budapest, Hungary, in 2008. 7 Based on the initial results and experiences by Dr. Nagy, the FDA approved the four main steps of femtosecond LCS in 2009 for the LenSx (Alcon Laboratories, Inc., Fort Worth, TX) used by the Budapest team. These four steps are femtolaser-like capsulorhexis, lens fragmentation (liquefaction), corneal incisions, and arcuate incisions. 2 Unlike other lasers such as Nd:YAG and Excimer, ultrashort pulses (10-15 seconds) eliminate the threat of collateral damage to the surrounding tissues and the excessive generation of heat.
17.2.1 Five Platforms
At the current time, five femtosecond laser systems for cataract surgery are commercially available. Beyond the LenSx, these are the Catalys Precision Laser System (Abbott Medical Optics, Abbott Park, IL), the Lensar platform (Lensar Inc., Orlando, FL), the Victus platform (Bausch and Lomb, Rochester, NY), and the Femto LDV platform (Ziemer Ophthalmic Systems, Switzerland). All of these, except the Femto LDV platform, are available in the United States. The LenSx is reported to be the most widely sold of the systems. 8 There are a number of differences between them, some of which should be pointed out in short here (Table 17.1).