Automated Capsulotomy Devices
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Introduction
The technological advances in the cataract surgery space has vaulted patient expectations and transformed the procedure into a refractive procedure. In the cataract surgery sequence, the continuous curvilinear capsulorrhexis (CCC) or capsulotomy of the anterior capsule is widely considered the most important step for consistent and predictable outcomes. The notable advancements in IOL technology related to advanced optics and materials has only heightened the importance of this step during cataract surgery. The opening in the anterior capsule allows safe removal of lens material and enables the implantation of an intraocular lens (IOL) within the capsular bag. Creating a circular, centered opening is critical for overlap of the anterior capsule over the optics of the IOL and prevention of IOL tilt or decentration.
Manual CCC conveys notable advances related to cost, time and efficiency and remains the most widely used technique and current gold standard but reproducible and consistent outcomes using this method require skill and experience. This step is recognized by many as the most challenging step in cataract surgery and surgeons employ various tools and techniques to maximize their outcomes. Despite the notable advantages of the manual CCC, the unmet need of patient dissatisfaction with their vision and refractive error following cataract surgery has prompted the development of new devices and technology within this space with a focus on automation.
Anterior Capsulotomy Importance
The creation of a precise, well-sized, circular capsulotomy is paramount for attaining consistent and favorable refractive and visual outcomes. The ideal anterior capsulotomy/capsulorrhexis is centered on the patient’s visual axis and achieves 360 degrees of even rim-to-optic coverage. The most important aspects to consider with creation of an anterior capsulotomy are size, capsular edge strength, circularity and centration. Collectively, these aspects contribute to the “perfect” capsulotomy.
The ideal size for the majority of cases ranges between 5.0 to 5.5 mm in order to achieve adequate, 360-degree rim-optic overlap. Prior studies have shown that capsulotomy sizes <4 mm or >6 mm both carry an increased risk of PCO formation. In addition, a poorly sized capsulotomy can consequently lead to IOL malposition (eg, tilt, decentration) which may lead to an increase in higher order aberrations. Poor sizing can also lead to incomplete optic coverage which subsequently increases the risk of IOL tilt and higher rates of PCO formation. While the manual CCC obviously permits the creation of a capsulotomy of any size, automated capsulotomy devices may be limited by the size and adjustability precision of capsulotomy.
Capsular edge strength is an important consideration with the introduction of new technologies as safety and minimization of complications remain a primary focus. Capsular edge strength is particularly important as it relates to risk of radial anterior tears; a radial tear can extend posteriorly and consequently lead to undesirable complications.
The importance of centration and circularity have been heightened by the introduction of new IOL technologies. Toric, multifocal and extended-depth-of-focus IOL offer increased spectacle independence compared to standard IOL offerings but are very sensitive to alignment, position and centration. A properly centered capsulotomy assists with capsular overlap of the IOL optic rim and maintenance of positioning of the implanted IOL. Decentration or deviation from the visual axis may contribute to undesirable visual phenomena. In addition, a malpositioned or poorly aligned IOL with associated tilt and/or decentration can affect visual and refractive outcomes.
Automated Capsulotomy Technologies
Femtosecond Laser Capsulotomy
Femtosecond-laser assisted cataract surgery, or FLACS, is capable of performing multiple steps of cataract surgery including the anterior capsulotomy. The introduction of the femtosecond laser has challenged the place of the manual CCC as the gold-standard technique as the femtosecond laser represents an automated technology that theoretically offers more consistency, circularity and centration. Since its introduction approximately a decade ago, the utility of femtosecond laser has been a major source of debate amongst cataract surgeons, consistent with the mixed results in the literature. This technology has only seen nominal adoption for a multitude of reasons including but not limited to cost, higher capital and compromised workflow. Despite the mixed results in the literature, the introduction of the femtosecond laser has highlighted the value of an automated capsulotomy as numerous studies have demonstrated the improved accuracy of centration, size and circularity and this has prompted the advent of new, additional technologies to automate this step of the cataract surgery sequence.
Several studies have reported the improved precision, circularity and reproducibility of the femtosecond capsulotomy compared to manual CCC. However, this improved performance regarding the capsulotomy hasn’t translated to superior visual and refractive outcomes. Moreover, similar to visual and refractive outcomes, the literature has remained mixed pertaining to the rate of anterior capsule tears, overall capsular strength/integrity and the rate of posterior capsular opacification (PCO). Two large studies evaluating FLACS outcomes reported anterior capsular tear rates lower than the reported rate that has been published in the literature evaluating manual CCC. However, a large comparative study in 2014 reported a statistically significant higher rate with FLACS compared to MCC. The enhanced rate with FLACS in this study was proposed to be attributable to the presence of residual, small tags that occurred after femtosecond capsulotomy.
Although the femtosecond technology is yet to demonstrate superior clinical outcomes in well-designed comparative trials, many surgeons still believe the evidence will eventually favor FLACS because of the superior precision and reproducibility of the capsulotomy. Additionally, FLACS has shown promise when employed to create the capsulotomy in complex cataracts. Ultimately, while adoption of the FLACS remains moderate in ophthalmology, it may have utility under special circumstances or when cases present unique challenges.
Zepto Precision Pulse Capsulotomy
The Zepto® precision pulse capsulotomy (PPC), which utilizes a novel mechanism for creating the capsulotomy, was FDA-approved in 2017. The PPC represents a novel approach for creation of an anterior capsulotomy. The device is composed of a small console connected to a disposable handpiece with a low-profile silicone suction shell with a flexible nitinol ring that delivers thermoelectric energy. The one-time use device utilizes the clear suction shell to create 360° apposition with the anterior capsule. After this is established, a quick pulse of energy produces an instantaneous, cleavage of the anterior capsule with a resultant, round capsulotomy of ~5.2 mm in diameter.
From a workflow standpoint, the PPC holds advantages compared to femtosecond technology including not requiring additional space, time (<5 msec), seamless introduction into the normal operating sequence and reduced costs. However, because it does carry increased costs beyond the manual CCC, it remains unclear whether this device will see widespread adoption.
Early clinical experience with the device has produced favorable, consistent results with potential value in cases of increased complexity. However, there were early reports of radial tears and incomplete capsulotomies with use of the device that prompted improvements and modifications. A reply to the author regarding an early study describing adverse complications with the device reported contrasting results suggesting there may be some user-dependent factors that contribute to successful completion of the capsulotomy. Nonetheless, additional studies are warranted to further evaluate the performance of the device.
The PPC may offer an advantage related to intraoperative alignment using patient fixation. Using Purkinje reflexes, a 2018 study described the PPC as a tool for visual axis centration. This technique evolved from the subject-fixated coaxial light reflex technique for refractive centration that was initially reported and described in 2014. Using coaxial microscope optics and patient fixation with guidance from the surgeon, the clear suction shell enables visualization that allows the capsulotomy to be centered on the Purkinje I image. This capsulotomy is able act as a “landing zone” for IOL centration with excellent capsular overlap, which is particularly important with advanced optics IOLs. Future studies will be important to determining and evaluating whether this technique translates to superior visual and refractive outcomes.
CAPSULaser Selective Laser Capsulotomy
The CAPSULaser (Excel-Lens), or selective laser capsulotomy, is a new technology currently undergoing investigation. Not yet available, the CAPSULaser aims to take advantage of the established femtosecond laser technology to create an anterior capsulotomy in a more efficient capacity with a transportable attachment to the surgical microscope. The device employs a non-contact laser that delivers continuous thermal energy to create a circular capsulotomy in 1 second. In contrast to the femtosecond laser, the laser energy is continuous rather than pulsed. The mechanism of the selective laser capsulotomy (SLC) involves application of trypan blue to the anterior capsule and the capsulotomy occurs with laser energy absorption of the dye-stained anterior capsule.
The laser projects a reticule as a guide for the surgeon to follow for centration and is readily adjustable from 4.5 to 7 mm diameters. In addition to the advantages related to efficiency, studies have demonstrated the SLC may provide a more stabilized, strengthened anterior capsule compared to manual CCC and FLACS, which is important for producing a consistent effective lens position (ELP). These studies suggest the increased strength may be a product of the associated phase change that occurs with the device that creates a “roll” at the capsular edge.
Aperture Continuous Thermal Capsulotomy
The Aperture CTC (International Biomedical Devices), or continuous thermal capsulotomy (CTC), is another option on the horizon that is currently undergoing pre-clinical testing. Similar to the previously described PPC and SLC devices, the CTC was developed with a focus on efficiency and is similarly easily incorporated into the surgical workflow. The CTC includes a small console that delivers thermal energy through a steel, ring-shaped cutting element. Once 360-degree contact with the anterior capsule is created, thermal energy is delivered that melts the collagen of the anterior capsule to create the capsulotomy.
Quick, precise and reproducible capsulotomies continue to be sought after by surgeons for optimizing outcomes without sacrificing time or efficiency. New automated devices currently or soon to be available include the Zepto precision pulse capsulotomy, CAPSULaser selective laser capsulotomy and Aperture continuous thermal capsulotomy. These devices aim to provide the advantages of precision and reproducibility with reduced costs and improved efficiency compared to femtosecond-created capsulotomies.
Notable innovation has occurred in this space as quick, precise and reproducible capsulotomies continue to be sought after by surgeons for optimizing outcomes without sacrificing time or efficiency. The manual CCC remains the technique of choice; however, there is a trend toward a guided or automated approach for improved reproducibility and precision, in particular for cases with advanced optics IOLs. At this point, there is no clear evidence to support the automated approaches lead to superior outcomes. As new devices are introduced and implemented, comparative studies will be important for evaluating their performance and determining whether their improved geometry translate to meaningful benefits for patients.
Conclusion
Notable innovation has occurred in this space as quick, precise and reproducible capsulotomies continue to be sought after by surgeons for optimizing outcomes without sacrificing time or efficiency. The manual CCC remains the technique of choice; however, there is a trend toward a guided or automated approach for improved reproducibility and precision, in particular for cases with advanced optics IOLs. At this point, there is no clear evidence to support the automated approaches lead to superior outcomes. As new devices are introduced and implemented, comparative studies will be important for evaluating their performance and determining whether the improved geometry confers superior visual and refractive outcomes.
