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Up Front | Apr 2008

Ultrasmall-Incision Cataract Surgery

With slight procedure modifications and oval shaped instruments, true MICS can be achieved.

Microincision cataract surgery (MICS) has been a revolutionary development for ophthalmology. MICS is a procedure that allows smaller, better-healing phaco wounds and provides superior fluidics control. Although MICS continues to become more widely accepted for cataract surgery, many are still unsure of its benefits. Additionally, many surgeons remain uncertain as to exactly what a true MICS procedure is.

The first sub–2-mm incisions for phaco were created using a biaxial, sleeveless phaco technique. In recent years, several companies have adjusted their coaxial technology to provide smaller incisions using what is being termed microcoaxial phaco technology, using a sleeve on thinner needles. Microcoaxial technology, however, essentially dismisses the biaxial technique at the expense of its key advantages. In my opinion, separation of irrigation and aspiration is at the heart of the MICS technique, unfortunately, the biaxial nature of MICS is daunting enough to cause surgeons to shy away from the technique.1

In this article, I will discuss the evolution of MICS and provide my personal perspective on why I prefer a modified biaxial MICS technique.

THE EVOLUTION OF MICS
Phaconit, bimanual, biaxial, and MICS are all meant to refer to a single technique. When Amar Agarwal, MS, FRCS, FRCOphth, used a bent needle as an irrigating chopper and removed the sleeve from the phaco tip in 1998, he indeed sparked a revolution. He called the procedure phaconit, meaning phaco with needle incision technology.2

Subsequently, several dedicated choppers were invented, and more surgeons started to perform the technique, now calling it bimanual because a second hand was used for the irrigation line. It was in 2000 that Jorge L. Alió, MD, PhD, of Spain, coined the term MICS, now widely accepted as the standard term for this technique.

The small incision achieved with MICS, although significant, is only one component of this advanced procedure. The second, and perhaps the even more significant, component to MICS is the separation of irrigation and aspiration into two axes. The irrigating axis held in the surgeon's second hand provides a third instrument in surgery. Provided that the chopper has frontal open-ended irrigation, the surgeon can freely direct the fluid in several directions during the procedure, move the nuclear fragments from the angle to the aspirating tip, or use the flow to push away the posterior capsule.

It is important to note that only recently was the term MICS adopted by phaco machine manufacturers to refer to microcoaxial surgery. While microcoaxial intends to allow for sub–2-mm incisions, it is not a true MICS procedure because (a) irrigation and aspiration are married, just as with a regular coaxial procedure, eliminating that crucial component of irrigation as the third instrument, and (b) it does not necessarily allow for sub–1.5-mm incisions. Perhaps a solution to the confusion surrounding the term MICS could be resolved by dividing it into two subtechniques: microcoaxial and microbiaxial. I have coined my own term for a true biaxial MICS procedure: ultrasmall incision cataract surgery (USICS), which is based on the evolution of cataract surgery in the last 25 years.

SMALL-INCISION HISTORY
For ophthalmology and other surgical specialties, surgery performed under a microscope is termed microsurgery. As a cataract surgeon for nearly 30 years—and skipping the generation of intracapsular cataract surgery—I recall that when surgeons started using extracapsular extraction, a microscope was used. This was microsurgery!

After the first cataract microsurgeries, our incisions became smaller and more IOLs came to the forefront. When foldable, silicone IOLs were introduced, incisions again got smaller. By then, a cataract surgeon was expected to perform small-incision surgery. Now, with biaxial procedures it is logical that what we are doing is actually ultrasmall-incision surgery. This is why I came up with the term USICS.

INITIAL EXPERIENCE WITH MICS
When I started performing biaxial MICS in 2001, I was using a standard chopper and a bare phaco needle; both were round. With this technique, I experienced unstable anterior chambers that became too shallow for safe surgery. A closer look revealed several problematic factors. First, by removing the silicone sleeve from the phaco needle, the gap created between the incision and the needle resulted in excessive fluid loss. Second, the choppers I was using were compounding the loss of fluid—there was an incongruity of shapes created by inserting the round choppers made for coaxial phaco into planar or oval incisions, creating even more leakage.1 The third and final insult was that the so-called small incision needed to be enlarged for IOL insertion, becoming not small enough to warrant the difficulties that I was experiencing.

Faced with these challenges, I stopped performing MICS after 1 year—although I did not completely dismiss the technique because I liked the concept of biaxial. I went on to modify the MICS procedure with new instrumentation to accommodate what would become my USICS procedure.

MODIFICATIONS TO INSTRUMENTATION
In 2004, I designed an oval-shaped chopper and phaco needle to more closely match the wound architecture. I presented these instruments at a meeting in Moscow that year.3 The chopper, in addition to being oval, featured frontal irrigation to assist with flow. Alessandro Franchini, MD, of Italy, explained the advantages of open-ended frontal-irrigating choppers over lateral-opening choppers in "Why Bimanual is Better," in the September 2007 issue of CRST Europe.4

These oval instruments are manufactured by Buerki Innomed (Berneck, Switzerland; Figure 1). Together with an oval aspiration cannula, they constitute the A. Gomes USICS Kit (Figure 2). These instruments allow me to make incisions of 1.4 mm for a 20-gauge needle or chopper, and 1.2 mm for a 21-gauge set (Figure 3). The improved instruments resulted in a better fit of instrument to incision, less leakage, and a more stable anterior chamber.1,3 In turn, these resulted in deeper chambers, shorter phaco times, and microincisions that allowed the implantation of IOLs through sub–2-mm incisions.5

Although I consider the round choppers for sub–2-mm incisions to be the wrong shape, there are reports of good results when they are used for MICS.6

Why have I have I switched from standard phacoemulsification to USICS? The simple explanation is threefold: First, I am able to achieve smaller incisions (1.4 mm with specialized oval instruments);1,3,5 second, I use irrigation as my third surgical instrument; and third, as a result of the separation of irrigation and aspiration, I achieve better fluidics in the anterior chamber.

MY USICS TECHNIQUE
I begin surgery by creating two incisions of 1.4 mm, separated by 90?. After creating the capsulorrhexis, nuclear hydrodissection is performed normally, except that the efficiency is improved due to the closed chamber—the nucleus frequently pops out of the capsular bag, assuring that it will rotate freely and correctly. The closed chamber ensures that the nucleus rotates freely and correctly. This is important because without a free rotating nucleus, one can rupture the posterior capsule or cause zonular weakness. (In fact, if the nucleus is not free, I recommend not proceeding to phacoemulsification—if necessary, a viscodissection can be made.)

After hydrodissection, I introduce the oval phaco needle and the oval chopper and perform a regular phacoemulsification. Normally I use quick chop. I have noticed that a sleeveless phaco needle makes quick chop more efficient than the original technique for coaxial phaco.7 After completing emulsification, I stop ultrasound and remove the instruments. Again, because of the efficiency of the closed chamber, I can perform epinucleus removal with irrigation and aspiration alone.

A pearl for this step is to use a 20-gauge oval irrigating cannula. For aspiration, a 21-gauge oval cannula can be used, evoking a differential between irrigation and aspiration and increasing stability in the anterior chamber as well as maximizing efficiency with even the hardest epinucleus. The safety of the I/A procedure is also improved because a blunt tip, rather than a needle, is used for the procedure.

After aspirating the remnants of cortex, I have completed cataract surgery through two 1.4-mm or even 1.2-mm incisions (Figure 4).

PREFERRED TECHNOLOGY
Although the instruments I use for USICS can be used with any phaco machine (because the oval needle can fit any handpiece), I prefer peristaltic vacuum technology over Venturi. In general, I find that surge undermines any benefits that Venturi machines have in terms of powerful aspiration or software improvements.

I use the Sovereign WhiteStar Increased Control and Efficiency (ICE; Advanced Medical Optics Inc., Santa Ana, California) with Chamber Stabilization Environment (CASE) software. The machine and its upgrades provide the safety of peristaltic technology, better control over chamber stability, modulation of surge, and a cooler phaco needle. Together with the oval instruments, this machine works perfectly and gives me peace of mind. I am in the process of switching to the new WhiteStar Signature (Advanced Medical Optics, Inc.), which appears to be more user-friendly, while keeping the same concepts of chamber stability and cold technology.

My pump velocities are set at 35 to 45 cc, with a regular vacuum of 350 mm Hg. Ultrasound is set according to nucleus density. With the use of ICE technology, my effective phaco times are short, and because I am working in a closed chamber, the emulsification is highly efficient. Most importantly, the excellent surge control provided by the CASE software, as well as the increased efficiency from the oval instrumentation, means that I never have to place my bottle higher than 75 cm.

PREFERRED IOL
I began performing presbyopic IOL exchange using the Array Multifocal IOL (SA40; Advanced Medical Optics, Inc.; no longer available). At the time, I was still performing conventional phaco because of my unsatisfactory first encounter with MICS. Because refractive multifocal IOLs, including the ReZoom (Advanced Medical Optics, Inc.), have consistently caused the side effect of halos, I started using diffractive IOLs because the newest generation is much improved over earlier versions, such as the 3M Multifocal IOL (3M Corporation, St. Paul, Minnesota), which was associated with several problems.8

Nevertheless, a problem persisted: diffractive IOLs, such as the Tecnis ZM 900 (Advanced Medical Optics, Inc.) required incisions of 3 mm or larger. Despite their good visual performance, these lenses never fit through an incision less than 3 mm. As I was developing a preference for biaxial surgery, it seemed to me a waste of good technology to complete phaco through a 1.4-mm incision and then enlarge the wound to 3 mm to insert the IOL. Additionally, enlarging the incision for IOL insertion can induce postoperative astigmatism. For a surgeon performing presbyopic IOL surgery using sophisticated microincisions, this made no sense.

Opinions are split about which multifocal IOL is better—diffractive or refractive—and even more division exists over mixing the two types.9 There is little evidence in the literature as to what incision size is best for implanting multifocal IOLs, so it seems that polemics surround not only the debate of which type of optics is best for multifocal IOLs, but also the best incision size.

To my knowledge, the only diffractive multifocal currently on the market that is implantable through a 1.8-mm (or at least sub–2-mm) incision is the Acri.Tec Acri.LISA diffractive multifocal IOL (Carl Zeiss Meditec AG, Jena, Germany) (Figure 5).10 While not perfect, the Acri.LISA is the only IOL that puts together the advantages of MICS and multifocality, with no halos and no induced astigmatism. In sum, I believe this IOL is better for me and for my patients.

USICS: A TRUE MICS PROCEDURE
In my opinion, the technology and technique employed in a USICS procedure improves on the revolutionary technique that Dr. Argawal created in 1998. With a biaxial technique combining oval instruments, an open-ended chopper, user-friendly machines, and multifocal IOLs that can be inserted through sub–2-mm incisions, MICS, as I understand it, is the procedure we have been waiting for—truly modern cataract surgery.

Fernando Araujo-Gomes, MD, is in private practice at ClÌnica de Santo António, Amadora, Portugal, and in office-based practice in Lisbon, Portugal. Dr. Araujo-Gomes developed his own technique and instrumentation for bimanual ultrasmall incision cataract surgery and states that he has a royalty agreement with Buerki Innomed. Dr. Araujo-Gomes may be reached at tel: +35 1919545845; fax: +351212322464; or e-mail: fernando.gomes@netvisao.pt.

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