Since 1976, cataract surgery has passed through three phases of bimanual surgery (Table 1). In the late 1970s and 80s, surgeons who tried bimanual phacoemulsification experienced problems with corneal burns, and thus it was used only for aspiration of soft cataracts in children.1,2 These early implementations of the bimanual technique led to the development of bimanual I/A.3
The second phase of bimanual cataract surgery was introduced in 2001, with the development of cold phacoemulsification and microincision cataract surgery (MICS) with WhiteStar micropulse technology (Advanced Medical Optics, Inc., Santa Ana, California). This development opened the door to adapting the bimanual technique from I/A and vitrectomy to emulsifying the nucleus. Instruments such as irrigating choppers, bimanual I/A systems, coaxial forceps, and WhiteStar MICS handpieces were developed and adapted for bimanual phaco. Studies have demonstrated heat reduction4,5 and safety with this technique,6-10 but investigators have also documented a reduction in efficiency with respect to operating time caused by the use of smaller phaco tips.11
The third phase of bimanual phaco, with the introduction of the WhiteStar Signature, has demonstrated that MICS is not only possible but has advantages over coaxial phaco. New fluidics control with WhiteStar Chamber Stabilization Environment (CASE), using occlusion-dominated evacuation of the nucleus, with aspiration and/or emulsification and with a nucleus rotation (carousel) technique, results in the same efficiency with bimanual MICS as with coaxial phacoemulsification.
TERMINOLOGY
When phacoemulsification and foldable IOLs were introduced, the term small-incision cataract surgery described the use of an incision of 3.0 ±0.3 mm.
Bimanual phacoemulsification, meaning the separation of the irrigation and aspiration functions for I/A and vitrectomy, has been used since the early 1980s with incisions of 1 to 1.2 mm.
In 2000, Alió12 introduced the term MICS for incision sizes smaller than 1.5 mm. Conventional phaco (today described as coaxial) and laser phaco can also be performed through incisions of 1.5 mm or less.
For a more precise description, today MICS describes incision size, and bimanual, coaxial, and laser phaco describe the technique used for evacuation and emulsification.
BIMANUAL MICS TECHNIQUE TODAY
Two port incisions of 1.2 mm for 20-gauge or 1.4 mm for 19-gauge instruments are created temporally, 70º to 90º apart from each other. The wounds are created in the posterior limbal region, with greater length than width and with the outer width slightly larger than the inner width. An ophthalmic dispersive viscoelastic (Healon, Advanced Medical Optics, Inc.) is instilled. The capsulorrhexis is created with coaxial forceps or a needle, hydrodissection is performed with a small amount of balanced salt solution, and rotation of the lens and cortex are performed.
An irrigating chopper is introduced first (Duet bimanual system; MicroSurgical Technology, Redmond, Washington), followed by the phaco tip (19- or 20-gauge tip, straight, 30º bevel). For settings on the WhiteStar Signature, see Table 2.
Aspiration of cortical material is performed, with direct carouseling of the whole nucleus or direct chopping into two-over-two or four-over-four nucleus segments to carousel (Figure 1). Aspiration of cortical material can often be performed with the phaco tip. Bimanual I/A is performed, and then the incision is enlarged to 1.6 to 2 mm for insertion of a MICS IOL (Acri.Tec Acri.Smart; Carl Zeiss Meditec AG, Jena, Germany) or to 2.7 mm for a conventional or refractive IOL (Figure 2). Both lens types are implanted with injectors.
WHY BIMANUAL MICS?
Today, some surgeons use MICS, whether bimanual or coaxial, for all of their surgeries. However, most surgeons are still using conventional coaxial small-incision cataract surgery, as a significant number of surgeons are not using bimanual I/A or chopping techniques.
Despite this, MICS is now at the cutting edge of phacoemulsification techniques. The industry is still being urged to design new devices and instruments for MICS, and these developments have also helped to advance conventional phaco.
With bimanual phaco, the separation of the irrigation and phaco functions creates better fluidics in the anterior chamber, which is different from coaxial MICS. Keeping the irrigation tip above the iris plane helps improve followability of the nucleus. This helps us use the instrument to move tissue in a certain direction, and it facilitates manipulation during phaco in an eye with compromised capsular bag or zonules.
If a MICS-compatible IOL is to be implanted and the nucleus is not expected to be too hard, bimanual phaco is recommended.
DISCUSSION
Phaco surgery is scrutinized more than ever by the public and health care institutions for a number of reasons. On the one hand, the public is increasingly demanding refractive lens exchange, and on the other, health care institutions are constantly pressuring surgeons with reductions of reimbursement levels. These competing forces cause a constant struggle between safety and efficiency.
Control of the intraoperative environment, through both instrument technology and the surgeon's technical experience, is mandatory for excellent surgical quality and postoperative visual outcome, including on postoperative day 1.
The demand for efficiency is continually rising. The WhiteStar Signature is designed for this, extending safety margins for today's lens removal techniques, including bimanual MICS for cataract and refractive lens surgery.
CONTROL
Control in surgery means finding the balance between safety and efficiency. Advanced software, new processors, and sensors in the WhiteStar Signature all contribute to fluidics control.
Built-in features help the surgeon to control and anticipate situations during surgery: Pressure in the anterior chamber is monitored, and rapidly reacting control circuits regulate the flexible vacuum pump, vacuum threshold, rise time, and the amount of time high vacuum is held before powering down.
The new Surgical Media Center provides streaming video, monitoring video images, and data curves (Figure 3). These data curves, showing the actual parameters used, can help to later review each situation offline, image by image.
Thus, the machine provides more computer-assisted control of phacoemulsification by measuring the situation, anticipating changes, and automatically adjusting parameters.
SAFETY
Safety issues such as corneal burn and postocclusion surge leading to capsule rupture or an unstable anterior chamber have been addressed with these most recent innovations.
The WhiteStar technology with hyperpulse mode enabled the use of unsleeved phaco tips for incision widths less than 1 mm with specially designed handpieces. Irrigating choppers and WhiteStar CASE introduced a new era of fluidics control.
Now, the WhiteStar Signature system adds a rapidly responding vacuum pump. The system reacts in as little as 26 milliseconds, reversing the pump to actively step down vacuum, thus reducing postocclusion surge. With this amount of safety, it is now possible to work with the same settings for bimanual as conventional phaco.
EFFICIENCY
Efficiency can be used to judge the overall capabilities of a system. The system must provide efficiency: (1) for the operating room staff to set up and to run, (2) in the eyes of the patient, and (3) for the surgeon to control his work environment and manage video and system settings.
The safety provided by the WhiteStar Signature boosts efficiency, especially for MICS in bimanual or coaxial phaco. Higher flow rates and vacuum levels can be used while maintaining a stable anterior chamber. A computer-controlled peristaltic pump helps preserve the excellent holding capabilities and provide the ability for safe and efficient followability. Thus, after controlled and efficient hydrodissection, cortical material can also be evacuated out of the capsular bag with the phaco tip (Figure 4). As a result, bimanual MICS now has the same efficiency as coaxial phacoemulsification.
The WhiteStar Signature also aids efficiency in the operating room with snap-in cassettes, short circuits for priming, and preset phaco settings available through a touchscreen interface.
The Surgical Media Center adds another level of efficiency. The familiar overlay, showing phaco parameter data on the screen, has now been developed into a complete media center. Continuous recording of surgeries, showing not only the video images but also the curves of phaco parameters (Figure 3), allows later detailed image by image analysis. The system also permits easy editing of videos, case by case review, and documentation for quality management.
The WhiteStar Signature helps the surgeon to perform bimanual MICS with the same levels of safety and efficiency as in coaxial phacoemulsification, and it additionally supports teaching the technique with the new Surgical Media Center.
Ekkehard Fabian, MD, practices at AugenCentrum MVZ Rosenheim, Germany. He states that he is a paid consultant to Advanced Medical Optics, Inc., but does not have financial interest in the products mentioned. Professor Fabian may be reached at Prof.Fabian@AugenCentrum.de.
