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Femtosecond phacoemulsification: the business and the medicine

Uy, Harvey S.a,b; Edwards, Keithc; Curtis, Nickc

Current Opinion in Ophthalmology: January 2012 - Volume 23 - Issue 1 - p 33–39
doi: 10.1097/ICU.0b013e32834cd622
CATARACT SURGERY AND LENS IMPLANTATION: Edited by Natalie Afshari

Purpose for review Phacoemulsification is the preferred method for cataract surgery in the developed world. The number of phacoemulsification procedures performed annually is expected to increase as the population ages. Femtosecond cataract surgery offers several surgical advantages over conventional phacoemulsification and has already attained commercial application in some countries. The purpose of this review is to outline the benefits, risks and commercial issues of femtosecond lasers as applied to cataract surgery.

Recent findings Cataract surgeons are adopting femtosecond technology to perform laser capsulotomy, lens fragmentation, clear cornea incisions and limbal relaxing incisions. Femtosecond lasers clearly perform these surgical steps with greater precision and reproducibility. Further benefits such as improved postoperative refractive results and reduced complication rates are being investigated. Commercial issues have invariably arisen such as cost of installation and operation, value proposition and return on investment.

Summary Femtosecond cataract surgery is an evolving procedure that can potentially lead to better and safer surgical outcomes. This review presents the currently available scientific evidence and discusses some of the relevant financial issues concerning this technology.

aAsian Eye Institute, Makati

bDepartment of Ophthalmology and Visual Sciences, University of the Philippines, Philippine General Hospital, Manila, Philippines

cLensAR Inc., Orlando, Florida, USA

Correspondence to Harvey S. Uy, MD, Asian Eye Institute, 9F Phinma Plaza Building, Rockwell Center, Makati 1200, Philippines. Tel: +1 632 898 2020; fax: +632 8998 2002; e-mail: harveyuy@yahoo.com

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INTRODUCTION

Cataract surgery is one of the most commonly performed surgical procedures worldwide and the number of individuals with cataracts is expected to reach 30 million by the year 2020. In 2011 alone, an estimated 19 million cataract procedures are expected to be performed around the world. Phacoemulsification is the preferred method for cataract surgery in the developed world. Since its introduction, phacoemulsification technology has rapidly developed through improvements in intraocular lens (IOL) technology, energy delivery, system fluidics and instrumentation [1–7]. Despite these advances, sight-threatening complications, such as postoperative corneal edema, posterior capsular rupture, cystoid macular edema and endophthalmitis, still occur [8–11]. Biomechanical damage to the cornea may result from excessive phacoemulsification energy, anterior chamber turbulence, cavitation energy and hydroxyl radical generation during ultrasonic energy delivery [12–17]. Early efforts to minimize these unwanted effects involved the use of Nd:YAG and erbium YAG lasers to precut or fragment the crystalline lens; however, these approaches were of limited utility and still required conversion to conventional ultrasound-based phacoemulsification in many cases [18–23].

The application of femtosecond lasers in corneal refractive surgery clearly demonstrated increased precision of corneal tissue photodisruption while avoiding significant collateral damage [24–26]. The early success and wide acceptance of femtosecond lasers for flap creation and astigmatic keratotomy have stimulated the development of this technology for laser-assisted or femtosecond cataract surgery [27▪,28▪▪]. In this review, we discuss the current applications and commercial issues of femtosecond lasers in laser-assisted cataract surgery.

Box 1

Box 1

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FEMTOSECOND LASERS

Ultrashort pulse lasers such as pico- or femtosecond lasers operate at near infrared wavelengths and are focused at predetermined depths to photodisrupt ocular tissues with minimal collateral damage. The laser produces cavitation bubbles that create cleavage planes used for surgical advantage. With the aid of high-resolution scanning systems, target ocular tissues can be precisely imaged allowing accurate and fast placement of femtosecond laser energy in preset patterns and predetermined depth and width. The level of precision of computer-controlled laser incisions is far greater than that achievable by manual means.

In femtosecond cataract surgery, the laser energy can be directed at the corneal tissues to create self-sealing clear corneal and limbal relaxing incisions. The laser energy can also be directed at the anterior lens capsule to create perfectly round, well centered, capsulotomy buttons of a precise diameter. Laser lens fragmentation (LLF) of the crystalline lens is another capability that results in significant reduction of phacoemulsification energy utilized for nuclear disassembly.

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FEMTOSECOND LASER SYSTEMS

As of this writing, four femtosecond laser systems are in commercial use or development. These include the LensAR Laser System (LensAR, Orlando, Florida, USA), LenSx Laser System (LensX, Aliso Viejo, California, USA), Catalys Precision Laser System (Optomedica, Santa Clara, California, USA) and Customlens System (Technolas, München, Germany). The LenSx system was the first system to be marketed commercially and has received US Food and Drug Administration 501(k) clearance for laser anterior capsulotomy and LLF. Currently, the LensAR system has also received FDA US Food and Drug Administration 501(k) clearance for laser anterior capsulotomy (LAC) and lens fragmentation. The four platforms differ in terms of their docking mechanism, imaging systems, graphic user interface, preprogrammed treatment algorithms and mobility. These features are summarized in Table 1.

Table 1

Table 1

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FEMTOSECOND CATARACT SURGERY STEPS

The essential preoperative steps for femtosecond cataract surgery include accurate biometric measurements and assessment of medical status. The patient must be able to cooperate with the docking procedure, which is generally performed under topical anesthesia without sedation. Surgical duration for the femtosecond laser treatment is about 3–5 min. Full pupil dilation is crucial to maximize femtosecond laser application and may be aided by using mydriatics and nonsteroidal anti-inflammatory drops. After docking, the anterior segment is scanned using a high-resolution imaging system followed by LAC, then LLF and creation of corneal incisions. The patient is then transferred to another bed for the phacoemulsification procedure.

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LASER ANTERIOR CAPSULOTOMY

One of the most critical steps of phacoemulsification is the creation of a continuous circular capsulorrhexis (CCC). A well constructed CCC facilitates hydrodissection, nuclear mobility and disassembly, cortical removal and IOL implantation. A poorly constructed CCC may predispose the eye to capsular tears, posterior capsular rupture, vitreous loss and improper IOL implantation [29–32]. Correct sizing of the CCC in relation to the optic diameter is critical for ensuring IOL stability, to maintain consistency of effective lens position, for minimizing posterior capsular opacification and for achieving refractive predictability. In the current age of advanced technology IOLs (aspheric, toric, multifocal, accommodative), a less-than-ideal CCC may negatively impact IOL positioning consequently leading to unexpected visual outcomes.

Unfortunately, conventional CCC creation is a manual procedure that is at best, prone to inconsistency of size, shape and centration, even in experienced hands (Fig. 1). In the presence of many predisposing factors (deep set eyes, inadequate pupil dilation, posterior synechiae, anterior capsular fibrosis, shallow anterior chamber, zonular weakness, inadequate corneal clarity, poor red orange reflex), the level of difficulty and probability of creating a suboptimal CCC increases.

FIGURE 1

FIGURE 1

These challenges and limitations stimulated the development of the femtosecond laser for LAC. Initial studies involved utilizing femtosecond lasers to create anterior capsulotomy buttons in animal and human cadaver eyes. Nagy et al.[28▪▪] demonstrated that for an intended 5-mm capsulorrhexis in porcine eyes, the mean achieved capsule button diameter was 5.88 ± 0.73 mm using a standard manual CCC and 5.02 ± 0.04 mm using LAC. Scanning electron microscopy revealed capsule buttons to have smooth edges regardless of method of cutting.

In a nonrandomized clinical trial, Tackman et al.[33▪▪] analyzed 49 capsule buttons created using LAC and 24 buttons created using manual CCC (Fig. 1). The mean deviation of capsule diameter from intended diameter was 0.18 ± 0.17 mm and significantly less in buttons created using LAC compared with the mean deviation of 0.42 ± 0.54 mm among buttons constructed using manual CCC. Furthermore, the median surgeon-reported ease capsule removal was 9 (1 = required manual capsulorrhexis of the whole diameter; 10 = free floating button or no manual detachment), indicating extreme facility of capsule removal.

Friedman et al.[34▪▪] demonstrated in 39 eyes that the deviation from the intended diameter of the capsule button was 29 ± 26 μm using LAC and 337 ± 258 μm using manual CCC. Capsule strength in porcine eyes was inversely proportional to femtosecond laser pulse energy and required 113–152 mN to rupture compared with only 65 mN needed to rupture manually created buttons. These laboratory investigations demonstrated that laser-cut anterior capsulotomies exhibited improved precision, consistency, accuracy and strength compared with manual cut capsules.

Further clinical work in human eyes similarly exhibited significant qualitative superiority and increased consistency of laser-cut anterior capsulotomies compared with conventionally created ones [28▪▪,33▪▪,34▪▪,35▪–37▪] (Fig. 2). Nagy et al.[36▪] in Hungary demonstrated in series of eyes that postoperative laser-cut capsulotomies exhibited significantly improved capsular overlap over the IOL optic and significantly reduced horizontal decentration over time [37▪]. In a study conducted in the Philippines, Uy et al.[37▪] compared the refractive outcomes of 53 eyes that underwent manual CCC with those that underwent LAC (Fig. 3). In this study, the mean deviation of spherical equivalent from intended refractive target was significantly greater for the conventional CCC group (+0.41 ± 0.40 D) compared with eyes that underwent LAC (−0.18 ± 0.515 D).

FIGURE 2

FIGURE 2

FIGURE 3

FIGURE 3

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FEMTOSECOND LASER LENS FRAGMENTATION

Nuclear disassembly is the core procedure in cataract surgery and involves the controlled, systematic breaking up and removal of the lens nucleus (nuclear disassembly). Successful phacoemulsification involves not only complete removal of lens material, but also removal in a manner that safeguards delicate surrounding ocular structures such as the capsular bag and corneal endothelium from iatrogenic damage. Nuclear disassembly is one of the most complicated steps of phacoemulsification and requires the greatest number of intraocular surgical maneuvers. Preoperative evaluation is crucial to identify cataract grading and potential complicating factors such as loose zonules, posterior polar cataracts, poor pupil dilation, posterior synechiae.

LLF substitutes laser energy for ultrasound energy and reduces potentially injurious amounts of ultrasonic energy, temperature increase [12] and free radicals [15–17]. Nagy et al.[28▪▪] demonstrated that in porcine eyes, the application of femtosecond LLF resulted in a 43% reduction in phacoemulsification power and a 51% decrease in phacoemulsification time. No complications were reported in this study. In a randomized clinical trial involving 29 patients, Batlle et al.[38▪] compared the amount of cumulative dispersive energy (CDE) utilized for phacoemulsification of laser-treated cataracts with that utilized for nonlaser-treated (manual) cataracts of different grades. Their study demonstrated that, on average, the CDE was reduced by 40% from 18.9 (manual) to 11.6 (laser) (P < 0.05) and concluded that pretreatment of the cataract with a femtosecond laser significantly lessens phacoemulsification energy potentially leading to reduction of surgical side effects.

Customizable LLF treatment profiles (algorithms) can be preprogrammed and incorporated into the femtosecond laser systems software (Fig. 4). The choice of treatment algorithm depends on surgeon preference and nuclear density. Surgeon technique and choice of treatment algorithm can influence surgical efficiency and the amount of ultrasonic energy needed for nuclear disassembly. Edwards et al.[39▪] performed a study on 138 eyes of which 85 eyes underwent LLF using a pie-cut treatment algorithm and 53 contralateral eyes underwent conventional phacoemulsification (control group) (Fig. 5). The overall mean CDE was 11.38 ± 14.93 for the laser-treated eyes and 14.04 ± 16.04 for the standard phacoemulsification eyes, a 19% reduction (P = 0.02). The amount of phacoemulsification energy reduction is related to nuclear density. For grade 1 nuclear cataracts, the mean CDE was 0 ± 0 in the LLF group compared with 4.38 ± 2.38 for the control group, a reduction of 100% (P = 0.006). For grade 2 nuclear cataracts the mean CDE was 2.98 ± 3.98 for the LLF group and 8.20 ± 6.13 in the control group, a reduction of 64% (P < 0.001). For grade 3 nuclear cataracts, the mean CDE was 9.27 ± 9.43 and 15.24 ± 12.95 for LLF and control groups, respectively, a reduction of 39%; although for grade 4 nuclear cataracts, the mean CDE was 24.04 ± 18.75 and 41.18 ± 24.68, a reduction of 42%. For grade 3 and 4 cataracts, the reduction was only significant at the 90% level. It should be observed that the absolute reduction of CDE in this study was proportional to nuclear grading (4.38, 5.22, 5.97 and 17.14 for grades 1–4 cataracts, respectively). Although this reduction in phacoemulsification energy may lessen the risk of endothelial damage and corneal decompensation, these benefits have to be established by larger, controlled studies.

FIGURE 4

FIGURE 4

FIGURE 5

FIGURE 5

LLF facilitates nuclear disassembly regardless of preferred technique. For divide-and-conquer surgeons, the fragmented nucleus requires less ultrasonic power during sculpting and segment removal, as the smaller fragments are already broken down extensively and can easily be aspirated by the instrument tip. For chop surgeons, the cleavage planes created during LLF facilitate clean fracturing and division of the nucleus into several pieces. For prechop surgeons, LLF creates cleavage planes that allow more complete and controlled division of even very dense nuclei into several segments. To date, no significant safety concerns or adverse outcomes have been reported by these various seminal studies [28▪▪,33▪▪,34▪▪,35▪–40▪]. Edwards et al.[40▪] have demonstrated in a study of 60 laser-treated eyes, the lack of differences in postoperative intraocular pressure and endothelial cell count among laser treated and control eyes.

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THE BUSINESS SIDE

Adopting new technologies into a clinical practice involves careful assessment of the benefits and costs (Table 2). Individual practices or doctors need to evaluate several parameters (patient acceptance of the technology, willingness to pay, surgical volume, surgical pricing structure, cost of space and personnel) and develop a workable business plan that will show a return on investment. A recent survey conducted about femtosecond cataract surgery (n = 1047 ophthalmologists) revealed that financial issues were their most important concern (72%) followed by reduced workflow efficiency (13%) and patient dissatisfaction or increased expectations (6%) [41▪].

Table 2

Table 2

Important considerations for adopting this technology include cost of the femtosecond machine, space, personnel and marketing. Currently, only the LensX machine is commercially available in the USA. In the future, the entry of competing platforms will provide more equipment options and lower femtosecond acquisition costs. A practice also has to consider the cost of additional space to house the femtosecond laser suite. One option is to provide a room large enough to contain both the femtosecond laser and the phacoemulsification machine so that both procedures can be performed in one room. Although this option minimizes patient and surgeon movement, it also prevents continuous use of the femtosecond unit. Another option is to have a dedicated femtosecond room and operator who continuously performs the femtosecond portions of the procedure (LAC, LLF, corneal incisions). The patients are then transferred to the phacoemulsification room for cataract removal. This latter system creates a need for coordination between the two rooms. Ideally, the distance from the femtosecond to phacoemulsification rooms should be short to minimize transport delays. Additional personnel will be needed to incorporate femtosecond cataract surgery. These include the femtosecond operator, which may be a technician or surgeon. Practices with an existing femtosecond flap maker may utilize the same operator for femtosecond cataract surgery. Clinic staff should also be trained to counsel patients on the merits and risks of femtosecond cataract surgery and premium IOLs. A marketing plan is essential to generate patient interest in this new procedure and will entail additional costs (brochures, advertisements, website).

The last but all-important issue is how to recover the cost of adopting the technology. Medicare and commercial payers already cover the cost of the cataract procedure. Neither surgeons nor facilities can charge Medicare or commercial payers additional amounts for using the femtosecond laser to perform cataract surgery. However, surgeons are allowed to charge patients directly, as a noncovered procedure, for femtosecond corneal and limbal relaxing incisons for the treatment of pre-existing astigmatism, which is present in significant degrees (>0.75 D) in about a third of the population. An appropriate informed consent should be obtained in which patients document their understanding of the procedure, the treatment alternatives, and request for the femtosecond cataract surgery as a refractive procedure [42▪].

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CONCLUSION

Femtosecond cataract surgery is a groundbreaking procedure that automates surgical steps and elevates surgical precision to a degree never before achieved. As the technology improves and new outcome and safety data emerge, confidence in the procedure will develop leading to acceptance and adoption by more cataract surgeons which in turn, will lead to the development of new useful applications.

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Acknowledgements

None.

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Conflicts of interest

H.S.U. is a paid principal investigator for LensAR Inc. K.E. and N.C. are employees of LensAR Inc.

There are no conflicts of interest.

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REFERENCES AND RECOMMENDED READING

Papers of particular interest, published within the annual period of review, have been highlighted as:

  • ▪ of special interest
  • ▪▪ of outstanding interest

Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 75).

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References

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This study demonstrates that LLF can significantly decrease the amount of phacoemulsification energy needed for removal of the crystalline lens. This suggests that LLF can reduce surgical complications attributable to excessive ultrasonic energy such as corneal decompensation.

Nagy Z, Takacs A, Filkorn T, Sarayba M. Initial clinical evaluation of an intraocular femtosecond laser in cataract surgery. J Cataract Refract Surg 2009; 25:1053–1060.

This study is one of the first to demonstrate the feasibility and safety of femtosecond cataract surgery.

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This study demonstrates that laser capsulotomy results in more consistently sized and shaped capsule buttons that are subjectively easier to remove. This suggests that laser capsulotomy may facilitate capsulorrhexis in complicated eyes.

Friedman NJ, Palanker DV, Schuele G, Andersen D, et al. Femtosecond laser capsulotomy. J Cataract Refract Surg 2011; 37:1189–1198.

This study demonstrates that laser anterior capsulotomies are superior to manual capsulorrhexis in terms of precision, consistency and strength.

Kranitz K, Takacs A, Mihaltz K, et al. Femtosecond laser capsulotomy and manual continuous curvilinear capsulorrhexis parameters and their effects on intraocular lens centration. J Refract Surg 2011; 27:558–563.

This study demonstrates that laser capsulotomy results in reduction of horizontal IOL decentration which may lead to stable and improved refractive outcomes when using advanced technology IOLs.

Nagy ZZ, Kranitz K, Takacs AL, et al. Comparison of intraocular lens decentration parameters after femtosecond and manual capsulotomies. J Refract Surg 2011; 27:565–569.

This study demonstrated that femtosecond lasers create more regularly shaped, sized and centered capsulotomy buttons resulting in better IOL overlap. These results suggest that better refractive stability can be achieve using laser capsulotomies.

Uy HS, Hill W, Edwards KH. Refractive results after laser anterior capsulotomy. Association for Research in Vision and Ophthalmology Annual Meeting. A4695 Poster #D634. Fort Lauderdale, FL; 2011. http://www.arvo.org

These results demonstrate that laser anterior capsulotomy can translate to improved refractive results that are closer to intended refractive target.

Batlle JF, Feliz R, Culbertson WW. OCT-guided femtosecond laser cataract surgery: precision and efficacy. Association for Research in Vision and Ophthalmology Annual Meeting. A4694 Poster #D633. Fort Lauderdale, FL; 2011. www.arvo.org

These results reveal that femtosecond lasers significantly reduce the amount of phacoemulsification energy needed for removal of cataracts of different grades.

Edwards K, Uy HS, Schneider S. The effect of laser lens fragmentation on use of ultrasound energy in cataract surgery. Association for Research in Vision and Ophthalmology Annual Meeting. A4710 Poster #D768. Fort Lauderdale, FL; 2011. http://www.arvo.org

This paper demonstrated that significant reductions in utilized phacoemulsification energy can be achieved with the application of femtosecond LLF.

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This study involving 60 eyes that underwent laser cataract surgery reported absence of adverse outcomes following laser cataract surgery. There were no differences in postoperative intraocular pressures and corneal thickness compared with conventionally treated eyes.

Dalton M. Bringing new technologies into the fold. Laser assisted cataract surgery. EyeWorld 2011; 16:30–31.

This article provides survey results from 1047 ophthalmologist regarding their opinions and concerns about adoption of femtosecond cataract surgery.

Passut J. Rules on how to charge for femto procedure get muddied, some say. EyeWorld 2011; 16:36–38.
Keywords:

femtosecond laser; laser capsulotomy; laser lens fragmentation; limbal relaxing incision; phacoemulsification

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