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Technologies and techniques such as femtosecond laser-assisted cataract surgery and microinvasive glaucoma surgery may be guiding the way for future cataract surgeries.
By Cheryl Guttman Krader; Reviewed by Malik Y. Kahook, MD, Nick Mamalis, MD, and Mark Packer, MD
Results from the 2015 survey of the American members of the International Society of Refractive Surgery-which were presented at Refractive Surgery subspecialty day at the annual meeting of the American Academy of Ophthalmology (AAO)-showed an increase in the proportion of respondents performing femtosecond laser-assisted cataract surgery (FLACS) compared with the previous year.
Their use of the femtosecond laser was predominantly for capsulotomy (90%) and lens fragmentation (93%) rather than for corneal or astigmatic incisions.
Throughout 2015, the performance of the laser for creating the anterior capsule opening and the development of alternative techniques have been popular topics in cataract surgery.
Speaking to Ophthalmology Times, Malik Y. Kahook, MD, Nick Mamalis, MD, and Mark Packer, MD, discussed capsulotomy techniques, the overall safety and efficacy of FLACS, and the adoption of microinvasive glaucoma surgery (MIGS) by cataract surgeons.
Although use of the femtosecond laser to create the anterior capsulotomy for cataract surgery is arguably very reproducible and accurate in terms of achieving circularity as well as intended size and location, accumulating evidence shows the approach is not perfect, noted Dr. Packer, clinical associate professor of ophthalmology, Oregon Health and Science University, Portland.
Considering that reports associated the femtosecond laser technique with an increased rate of anterior capsule tears, Dr. Packer and colleagues undertook a study to evaluate the strength of the femtosecond laser capsulotomy. Published in the British Journal of Ophthalmology [Packer M, et al. 2015;99:1137-1142], the study compared break force and extensibility of the capsule at break point in groups of enucleated porcine eyes treated with a 5-mm manual capsulorhexis or a 4.0-, 5.0- or 5.5-mm laser capsulotomy. The results showed that resistance to tears and the extensibility of the capsular opening increased with increasing capsulotomy size.
“It is interesting that many of the publications reporting an increased rate of anterior capsule tears with the femtosecond laser technique involved relatively small capsulotomies of less than 5 mm in diameter,” Dr. Packer said. “Median diameter was 4.7 or 4.9 mm, which means that half of the capsulotomies were even smaller.
“The average size of a manual capsulotomy is usually about 5 or 5.5 mm, and so part of the explanation for why femtosecond laser capsulotomies are associated with higher tear rates may be that surgeons are operating through a smaller opening that won’t stretch as much and that has less rim area to distribute forces,” he said.
Dr. Packer said that he hopes surgeons using a femtosecond laser for capsulotomy will now be making the opening a little larger in diameter.
He noted that while Michael Lawless, MD, and colleagues from Australia initially reported an anterior capsule tear rate of 0.31% in their first report on 1,300 consecutive femtosecond laser cases, the rate had decreased to 0.21% in a subsequent, larger series of 3355 consecutive cases [Roberts TV, et al. J Cataract Refract Surg. 2015;41:1109-1110].
“The Australian surgeons did not specify if they changed the size of the capsulotomy over time,” Dr. Packer said. “However, they did note a statistically significant reduction in the rate of anterior capsule tears after the manufacturer of the femtosecond laser they were using (LenSx, Alcon) replaced the original curved rigid patient interface with a new soft interface (Softfit).”
“In theory, the propensity for tearing may be less when using the latter interface because it causes less corneal compression that may result in more accurate placement of individual laser spots within the intended circumference of the capsulotomy,” he said.
Regardless of the advances that have been made with femtosecond laser capsulotomy, some drawbacks for the technique may still exist. Because not all of the laser shots are perfectly aligned along the circumference, analyses of scanning electron microscopy images show that the capsular edges are relatively rough and uneven, Dr. Packer noted.
“Cataract surgeons looking at those images may think that if it was their own eye, they would rather have a manual capsulorhexis, sensing that its smooth edges would make it less prone to tearing,” he said.
As Dr. Packer and Dr. Kahook pointed out, cost and efficiency also present barriers to laser use.
“The safety and reproducibility of femtosecond laser capsulotomy is much better today than at launch, and I think it will be a part of our surgical practice for the foreseeable future,” said Dr. Kahook, The Slater Family Endowed Chair in Ophthalmology and Professor of Ophthalmology, University of Colorado School of Medicine, Aurora. “However, the laser is very expensive, and with most of the platforms, its use alters surgical workflow with significant added time for each case.”
Dr. Packer said, “It is interesting that for years, cataract surgeons considered the manual techniques they were using for capsulorhexis to be the best they could be. Then, the femtosecond laser came along and seemed to offer promise for greater consistency and perhaps even better predictability of the effective lens position. Concerns about anterior capsule tears somewhat dampened enthusiasm for the laser, but they seem to have been allayed. Nevertheless, the fact that the laser is restricted to the premium channel has created interest in lower cost devices.”
The limitations of the laser include the difficulty of residents mastering the continuous curvilinear capsulorhexis (CCC), a critical element in surgical success, which is frequently less than perfect even in the hands of expert surgeons. Several companies have been developing devices for enabling reproducible capsulorhexes that are less costly than the femtosecond laser while leading to less disruption of operating room flow.
“Because of its cost, FLACS is pretty well restricted to the premium channel of cataract surgery, which represents only about 15% of operations. And so, there is a lot of interest in other devices for capsulotomy,” Dr. Packer said. “It was particularly interesting that the evolution of the capsulotomy was the topic of the Binkhorst Medal Lecture given by Richard Packard, MD, at the ESCRS Congress this year, and that in concluding his talk, Dr. Packard did not say that the femtosecond laser is the state of the art but rather he suggested that one of these lower tech devices may represent the more advanced technique.”
The Verus Ophthalmic Caliper from Mile High Ophthalmics is a recently introduced device designed for assisting with a CCC at time of cataract surgery. The device is a silicone ring that is placed on the anterior capsule for use as a surgical guide. Invented by Dr. Kahook, it is now available in the United States as well as in Asia, and it is expected to get the CE mark in the first quarter of 2016, Dr. Kahook said.
The device was introduced to guide creation of a 5-mm capsulorhexis, but a second device that could guide a 5.5 mm capsulorhexis was introduced at the 2015 meeting of the American Academy of Ophthalmology in response to demand, he added.
“[It] serves as a template for CCC precision and centration, and the final result is still a CCC, which continues to be the strongest type of capsulorhexis known for cataract surgery,” Dr. Kahook said. “Therefore, use of the Verus still leverages all of the time-tested benefits of the CCC. In addition, using the Verus adds only about 30 to 40 seconds to the procedure, and it does not alter surgical workflow.”
He also noted that surgeons are finding the device valuable not only for routine cases, but also for enhancing capsulotomy precision in premium IOL cases where the patient does not want to have a FLACS procedure or a laser is not available.
In addition, the device appears to be helpful when operating on white cataracts where it improves visualization and creation of a full capsulorhexis. Furthermore, Dr. Kahook said the silicone ring has been useful as a teaching tool for residents and that the 5.5-mm device has advantages in that regard.
“After inserting the ring and tamponading it against the anterior capsule, residents are asked to make a 5-mm capsulorhexis within the ring,” Dr. Kahook said. “In this approach, the ring serves as a guide for the resident surgeon as well as the teaching surgeon. This is valuable for the teaching surgeon because there is a 0.5 mm cushion that enhances the ability to see if the capsulorhexis is not following the 5-mm goal and allows for some time to react and rectify.
“Essentially, we use it as an added training tool for residents when they are performing their first few cases until they can get comfortable working inside the eye and with the CCC maneuvers,” he said.
The device has now been used in more than 5,000 cases around the world. Each disposable silicone ring costs $25 and is not covered by any insurance companies at this time.
Three other capsulotomy devices-none of which is currently approved for use in the United States-in development all act via a thermal mechanism to create the capsular opening
One device is a laser that attaches under the surgical microscope and is used to incise the capsule (CAPSULaser, CAPSULaser). It requires opening the eye followed by instillation of trypan blue to stain the anterior capsule. The laser is not absorbed without the staining step. Unlike the femtosecond laser that delivers energy in a series of shots, this laser-based device is able to cut a continuous curvilinear capsulotomy because it rotates in a single circular pattern while firing continuously. It is imperative that the trypan blue stain is washed out of the eye so that the laser is not picked up by the cornea or surrounding tissues during treatment.
A second capsulotomy device in development uses a soft suction cup to pull the capsule into contact with a nitinol capsulotomy ring (ZEPTO capsulotomy system, Mynosys). Rapid multipulse energy in the ring causes phase transition in water molecules that results in cutting of the capsule.
Dr. Packer noted that this device was compared with manual capsulorhexis in an ex vivo study using paired human cadaver eyes and was found to create capsulotomies that were stronger than those created manually.
Dr. Mamalis said the device was found to successfully create capsulotomies in the rabbit model in his laboratory at the Moran Eye Center with no significant complications or temperature rise in the anterior chamber.
Dr. Packer is chief medical officer for International BioMedical Devices, a company that is developing a device for creating a continuous thermal capsulotomy using a stainless steel ring that acts as a heat-conducting filament (ApertureRx Precision Capsulotomy System).
The key features of the system are its continuous 360° thermal element, which overcomes the inevitable gap required by radiofrequency devices with loop wire or ring cutting elements, and its uniform contact with the anterior capsule, which obviates the necessity for vacuum suction. With just a very short, millisecond level burst of heat, the collagen in the capsule melts and a capsulotomy is created. The device is in an early stage of development, and so far, it has been used only in porcine and human cadaver eyes.
Commenting on the three thermal devices, Dr. Kahook noted their use will add time to the procedure, but will likely still be more streamlined than a femtosecond laser-based procedure done in a separate room. He said that more data are needed to establish how well these devices perform in creating a well-centered circular capsulorhexis and to determine the strength of the capsulotomy.
“The latter issue is probably the big question needing to be answered because historically, a capsulorhexis created with a thermal device has been weaker than those made with a continuous freehand tear,” Dr. Kahook explained.
Since they are still in development, the cost of these devices and how the cost will be handled from an ambulatory surgery center or hospital standpoint are also unknown.
“If their use adds $100 or more to the procedure, there will need to be some reimbursement strategy to support their adoption,” Dr. Kahook said.
The development of these new tools for capsulotomy may forever change cataract surgeons’ skills, Dr. Packer predicted.
“If a device emerges that makes capsulotomy creation better and faster, perhaps we will see that manual capsulorhexis creation becomes somewhat of a forgotten art, just like corneal suturing has become with the advent of self-sealing cataract incisions,” he said.
Dr. Mamalis, professor of ophthalmology, John A. Moran Eye Center, and co-director, Intermountain Ocular Research Center, University of Utah, Salt Lake City, noted that the financial aspect of FLACS has been a high hurdle limiting its use in his university setting where a significant proportion of the patient population has coverage from Medicare or Medicaid. Nevertheless, Dr. Mamalis observed that the various femtosecond laser manufacturers have been very good at upgrading their technology’s hardware and software in ways that have been advantageous.
“For example, incomplete capsulotomies were an issue early on, but with changes to the interface, complete capsulotomies are made in the vast majority of cases using any of the lasers,” he explained.
However, Dr. Mamalis feels there is still a need for more data in larger groups of patients to establish that FLACS offers important benefits for improving refractive and functional outcomes after cataract surgery.
The femtosecond laser has also been touted for improving surgical safety and particularly for reducing the need for ultrasound energy through pretreatment of the cataractous lens. However, a large comparative study conducted by the European Society of Cataract and Refractive Surgeons (ESCRS) found FLACS had no significant advantages over conventional phacoemulsification except for reducing the proportion of eyes with astigmatism ≥1.5 D and minimizing surgically induced astigmatism.
In an update provided at the XXXIII Congress of the ESCRS in Barcelona, Spain, in September, Peter Barry, MD, also reported that postoperative BCVA was worse after FLACS than in the conventional phacoemulsification group, the proportion of eyes with worse BCVA postoperatively than preoperatively was significantly higher in the FLACS group than in the phacoemulsification group (3.3% versus 1.3%), and the worse BCVA outcomes with FLACS were due its association with a higher rate of postoperative surgical complications compared with phacoemulsification (3.4% versus 2.3%).
“There have been some good studies comparing FLACS and conventional phacoemulsification, but most of them have been quite small,” Dr. Mamalis said. “There is really a need for more data from larger studies, such as the ESCRS trial.”
News about phacoemulsification systems included the launch of two new platforms from Abbott Medical Optics-the Compact Intuitiv and the Whitestar Signature Pro System.
The Compact Intuitiv brings advanced fluidics and multi-directional ultrasound, and it is designed to maintain chamber stability and to minimize clogging. It provides the peristaltic fluidics and phaco parameters of the Whitestar Signature, has a touchscreen user interface, and the compactness of the Sovereign Compact, enabling portability and mobility.
The Whitestar Signature Pro System offers on-demand fluidics so that surgeons can choose to use a peristaltic pump, a venturi pump, or a combination of both modalities within a case.
In addition, it features a first-in-kind mobile analytics tool for phacoemulsification known as CASA (Cataract Analysis and Settings Application). CASA transmits performance metrics for the phacoemulsification procedure directly to an iPad tablet, and can aid surgeons and administrators in managing the surgical suite, thereby enhancing productivity.
Although MIGS is not technically cataract surgery, many of the MIGS procedures are being targeted for cataract surgeons. Already, the iStent (Glaukos) seems to be making its way into the cataract surgeons’ armamentarium as it can provide an opportunity to improve IOP control and reduce the medication burden for patients with mild to moderate glaucoma who need cataract surgery, Dr. Packer said.
“Safety is the hallmark of the MIGS devices because their use does not result in the types of complications that can occur with trabeculectomy that cataract surgeons do not want to deal with, namely hypotony, flat chambers, and hyphema,” Dr. Packer said.
“These complications are not avoided completely with MIGS, but they certainly are not occurring at the frequency that would be seen with filtering surgery,” he said. “For that reason, there seems to be a lot of interest among cataract surgeons in learning MIGS procedures.”
Dr. Mamalis noted that while some MIGS procedures are being targeted for cataract surgeons, as of now they are still mostly being used by glaucoma specialists who perform cataract surgery and by high-volume cataract surgeons.
“We will see broader interest in MIGS among cataract surgeons as these devices become easier to insert,” he said. “However, it may require that cataract surgeons hone their skills in using goniomirrors and with other techniques for visualizing the trabecular meshwork.”
Dr. Kahook added: “The recent acquisition of Aquesys by Allergan is an indicator of the interest in novel techniques for lowering IOP. Companies like Ivantis and Transcend continue the march toward FDA approval and we should have over half a dozen new MIGS devices on the U.S. market in the next 2 to3 years.”
New World Medical recently launched the Kahook Dual Blade at the 2015 AAO meeting in Las Vegas. The device is designed to lower IOP by creating an opening from the anterior chamber into the canal of Schlemm through an ab interno minimally invasive approach and may be done as a standalone procedure or combined with cataract surgery.
Malik Y. Kahook, MD
Dr. Kahook is a consultant to Alcon Laboratories, Allergan, Aerie Pharma, ClarVista Medical, New World Medical, Shire, Tempest Medical, Foresight Vision, and Mile High Ophthalmics. He holds patent interests with Alcon, AMO, ClarVista Medical, Mile High Ophthalmics, Glaukos, and New World Medical.
Nick Mamalis, MD
Dr. Mamalis is a consultant to Anew Optics and Medennium and receives research grant support from these companies and ARC Laser, Aaren Scientific, Abbott Medical Optics, Alcon Laboratories, Allergan, Bausch + Lomb, Calhoun Vision, ClarVista, Genisphere, HOYA, LensGen, Mynosys, Nu-Vue Technologies, Omega, PowerVision, and Sharklet.
Mark Packer, MD
Dr. Packer is a consultant to Advanced Vision Science, Aerie Pharmaceuticals, Alcon Laboratories, Bausch + Lomb, International Biomedical Devices, i-Optics, LensAR, Oculeve, Promedica International, Rayner Intraocular Lenses, Refocus Group, SOLX, STAAR Surgical Company, Transcend Medical, and VisionCare Ophthalmic Technologies. He holds equity in Eyenovia, Iantech, International Biomedical Devices LensAR, mTuitive, Refocus Group, Transcend Medical, TrueVision Systems, and WaveTec Vision Systems.