The minimization of incision size is part of the natural evolution of cataract surgery. Smaller incisions allow reduced operative trauma; decrease the possibility of infection; and maximize the stabilization, rehabilitation, and restoration of visual acuity. Currently, the standard practice is coaxial phacoemulsification with incisions starting at 2.2 mm or wider; more often, the length is 2.8 mm. Microincision cataract surgery (MICS)—the term Jorge L. Alió, MD, PhD, of Spain, introduced several years ago—is considered by most surgeons to encompass any cataract procedure performed through an incision size of 2 mm or less. Generally speaking, MICS has the potential to provide patients with a higher quality of vision.
Microincision procedures are increasingly required in refractive cataract surgery, a field that is continually growing and becoming more popular. The MICS technique is truly astigmatically neutral, making it ideal for refractive lens exchange. MICS is also associated with less postoperative wound leakage. Therefore, compared with procedures that use a larger incision, the risk of endophthalmitis is theoretically reduced.
BLEND OF TECHNIQUES
MICS is not a completely new surgical technique but it is instead a modification of several existing procedures. Currently, two versions of MICS are available: biaxial MICS (B-MICS) and coaxial MICS (C-MICS). Shearing described the biaxial technique more than 20 years ago;1 however, our ophthalmic surgery community has yet to widely adopted it. Drawbacks of biaxial include the high risk of chamber instability, the necessity to decrease the parameters of fluidics, and the absence of protection between the vibrating ultrasound needle and the corneal wound.
In 2007, Bausch & Lomb (Rochester, New York) introduced its Stellaris Vision Enhancement System (Figure 1). This is a new-generation phaco machine specifically designed to optimize MICS using either a biaxial or coaxial technique. The machine may also be used for standard small-incision coaxial surgery. This is my machine of choice when performing MICS.
EVOLUTION OF PHACO TECHNIQUES
Modern phacoemulsification is no longer based primarily on the role of ultrasound energy. Now, an optimal combination of mechanical cutting, ultrasonic emulsification, and vacuum aspiration is the focus.
Before Kunihiro Nagahara, MD, of Japan, described his revolutionary phaco chop technique in 1993, divide and conquer and in-situ fracture were the gold standards of phacoemulsification. It took several minutes of sculpting trenches or grooves before the lens nucleus could be fractured into quadrants, which required a significant amount of ultrasound and caused pressure on the lens-zonular apparatus. Dr. Nagahara's technique, which he compared to splitting and chopping wood, is currently widely accepted by ophthalmic surgeons. Now, the array of modified chopping techniques include the quick chop, combined trenching and chopping (ie, stop and chop), and variations of horizontal and vertical chopping. Phaco chop techniques are faster, more efficient, and safer than traditional techniques based on sculpting and cracking.
Multiple chopper designs, initially described as a modified lens hook, are currently available: long and short, sharp and blunt, and stick- and blade-like tips. A range of blade angles is also available. What is common to each technique and instrument is the main surgical principle that an ultrasound needle holds and stabilizes the nucleus with high vacuum while a second instrument (ie, chopper) acts as an axe to split the nucleus, first in half and then into quarters—or even smaller pieces according to the hardness of the lens material.
1.8-MM C-MICS SURGICAL TECHNIQUE
I prefer a microcoaxial approach. With the Stellaris, a new needle/sleeve combination designed to fit gently through a 1.8-mm incision provides inflow volume comparable with that achieved with traditional coaxial tips. The flexible sleeve walls guarantee a perfect seal against the incision, eliminating outflow. Additionally, the sleeve wall delivers more infusion laterally to minimize repulsion of nuclear fragments from the tip and improve followability.
The fluidics system of the Stellaris is optimized for safe, efficient, and controlled microcoaxial surgery with components that include advanced pump technology and the company's StableChamber high-vacuum, flow resistant, evacuation tubing.
Chamber stability is excellent; therefore, surgeons can use high vacuum settings to maximize holding force and emulsification efficiency. High vacuum settings are great for holding the nucleus and its fragments during phaco chop maneuvers. As flow and vacuum are increased, the efficiency of fragment evacuation is enhanced and repulsion of the lens fragments by phaco energy are reduced. The irrigating fluid bottle does not need to be raised above its usual height, and adjunctive devices used to increase infusion and maintain anterior chamber stability are not necessary.
Recently, we conducted a study that assessed the safety and efficacy of the Stellaris. Seventy-five eyes (75 patients) were implanted with an Akreos MI60 IOL (Bausch & Lomb) through a 1.8-mm incision after C-MICS. (For more information, see Stellaris Results.)
CATEGORIES
Numerous methods of nucleus disassembly have been described. Because lens nuclei vary in size and density, no one technique is universal enough to fit all clinical situations. My current concept is to use a spectrum of nucleus division techniques and emulsification. Patient selection is an essential factor in determining the best surgical technique. I divide my patients in one of three categories: soft nucleus, moderately dense nucleus, and dense or very dense nucleus.
HARDNESS DETERMINES TECHNIQUE
Soft nucleus. This type of nucleus is impossible to chop because it cannot withstand high vacuum. Therefore, it has a tendency to be fragmented before the ultrasound needle fixates the phaco tip to initiate the chop. The best technique for such nuclei is phaco aspiration assisted by short bursts of ultrasound.
Moderately dense nucleus. In these cases, the quick chop technique is most suitable. After performing continuous curvilinear capsulorrhexis and introducing the handpiece into the anterior chamber, the anterior soft portion of epinuclear material is aspirated without ultrasound. Then, the needle is impaled into the lens nucleus, holding it with high vacuum while the second instrument chops it. Vertical chopping is preferred because it avoids more peripheral placement of the chopper and subsequent risk of anterior capsule rupture. When the chopper is pulled toward the phaco tip, a short burst of ultrasound is activated. Just before the two instruments come into contact, they are sufficiently separated to create the fracture. After chopping the nucleus into half, it is rotated clockwise and each half is divided into two or three, depending on the lens hardness. Segments are removed with the ultrasound-assisted phaco aspiration technique, with minimal ultrasound energy. The mechanical force of the chopper mashes the smaller nucleus pieces into the phaco tip, further decreasing the amount of ultrasound required.
Dense or very dense nucleus. The stop and chop technique, first described by Paul S. Koch, MD, of Rhode Island, works best in this situation. First, the central groove is created and the nucleus is cracked in half. Then, each half is chopped into bite-size pieces. Creating a central groove makes room for the subsequently chopped fragments easing their mobilization within the capsular bag.
In cases of a very dense nucleus, the posterior nucleus contains bridging leathery bands that prevent its complete separation. When operating on a hard, brown lens, I prefer to use the stop-and-chop technique. First, a very deep central groove is etched until the red reflex can be visible through the remaining posterior nucleus layers. I have found it convenient to work with the microcoaxial tip in the deep groove. The sleeve is transparent, and the lens tissue is seen through it, adding a margin of safety. The lens is cracked in half. After rotating the nucleus 90?, each half is sliced into six to 10 pieces, depending on the nucleus. More fragments are needed in extremely hard nuclei. Using dual linear foot pedal control, I can achieve a tremendous grasping force that results in immediate emulsification and rapid evacuation of the nucleus fragments.
Even hard fragments are rapidly attracted and easily aspirated by the phaco tip. Proponents of torsional phaco point out that longitudinal ultrasound causes repulsion of nuclear fragments, but I believe that phenomenon occurs only if the fluidics parameters are not properly selected, causing inadequate vacuum and therefore inadequate aspiration.
During the final step, the remaining nucleus fragments are removed. I position my ultrasound needle at the center of the pupil, below the level of the iris. This positions the needle at the optimal distance from the most delicate anterior chamber structures. I prefer not to move the handpiece but rather to wait for the fragments to move directly to the needle. From time to time, I assist and conduct the pieces with the chopper.
SURGICAL SETTINGS
All my surgeries with the Stellaris were performed through a 1.6- X 1.8-mm trapezoidal incision (Figure 1) with an infusion bottle height of 100 cm and using dual linear control. Ultrasound settings were 30% maximum, 80 pulses per second, and a 50% duty cycle. Aggressive vacuum settings were used, with 400 mm Hg during ultrasound, 550 mm Hg during irrigation and aspiration, and the maximum vacuum rise time of 1. The main steps of nucleus removal are presented in Figures 2 through 5.
For many years now, I have not used separate settings for sculpting, chopping, and epinucleus removal. It is unnecessary to restrict myself to preset parameters, and I prefer to set the highest limits for ultrasound and flow, where I am confident that a rock-stable anterior chamber and sufficient power to emulsify the lens nucleus are guaranteed. The dual linear foot pedal control allows me to be flexible and instantly change surgical parameters depending on the intraoperative environment and stage of surgery.
A microcoaxial approach makes it easier to operate in an eye with a hard nucleus. The smaller phaco needle penetrates more readily into a dense lens compared with a standard tip. With a small-diameter ultrasound needle, it is easier to engage and aspirate the epinuclear material with less chance of accidental aspiration and rupture of the posterior capsule.
Intraocular visualization is improved when operating in eyes with small pupils, and the silicone sleeve between the vibrating phaco needle and the incision enhances corneal thermal protection to ensure a watertight incision postoperatively.
Transitioning to a new technique or new equipment is always challenging. The C-MICS chop technique is notmuch different from many other techniques using standard equipment. It is fast, reduces phaco time, minimizes corneal endothelial damage caused by excessive ultrasonic energy, and lessens the stress of the lens-zonular apparatus.
The evolution of modern phaco has eliminated or substantially decreased our reliance on ultrasound. The efficiency provided by the combination of hyperpulse with excellent fluidics and chamber stability makes the use of transverse oscillations of the phaco tip seems to add little or nothing to the overall efficiency and safety profile of the procedure. The learning curve with the Stellaris is short and intuitive.
The advanced technology of the Stellaris Vision Enhancement System enables safe and effective coaxial surgery through a 1.8-mm incision, regardless of lens density. An ultrasound needle and sleeve system designed specifically for C-MICS provides sufficient inflow and, in conjunction with the advanced fluidics system of the Stellaris, ensures safe, surge-proof surgery. Followability is excellent. Surgery is efficiently completed using energy comparable with that delivered when performing a coaxial procedure through a larger incision. This experience supports the conclusion that C-MICS with the Stellaris Vision Enhancement System is friendly to the eye, the patient, and the surgeon. This is an invaluable addition to the ophthalmic surgeon's armamentarium.
Boris Malyugin, MD, PhD, is the Chief of the Department of Cataract and Implant Surgery, and the Chief Deputy Director General of the S.Fyodorov Eye Microsurgery Complex State Institution, Moscow, Russia. He is a member of the CRST Europe Editorial board. He may be reached at tel: +7 495 488 8511; fax +7 495 905 8051; or e-mail boris.malyugin@gmail.com.
