Today, most surgeons use cataract incision sizes between 2.75 and 3 mm (Figure 1) and achieve very good results. The latest trend in cataract surgery is toward smaller incisions. The question is, does it pay to reduce incision size? Is the effort rewarded by superior results?
I have changed to a 2.2-mm microcoaxial approach because I believe it provides better results for my patients. The technique is safe, and it provides me with more predictable outcomes.
ADVANTAGES OF A SMALLER INCISION
A clear corneal 2.2-mm incision has several advantages over larger incisions. The smaller wound reduces postoperative induced astigmatism. It increases immediate postoperative wound watertightness and therefore reduces the associated risk of infection. It also decreases postoperative surface discomfort in the incision area.
Induced astigmatism can make the difference between needing and not needing postoperative cylinder correction, especially in corneas with a small amount of with-the-rule astigmatism. Also, with the advent of multifocal IOLs, minimizing induced cylinder may be an advantage.
Surgeons often use a rectangular incision design to stay peripheral on the cornea, but this shape can reduce the stability and performance of the wound. A smaller incision (2.2 mm) with the same depth gets nearer to a squared configuration, with more resistance to external pressures or eye squeezing. Postmortem studies have shown increasing resistance to external pressure as incision dimensions are reduced.
A waterproof incision in the early postoperative hours makes me feel more confident about reducing the potential for infection. My routine is to overinflate the eye at the end of surgery, stimulating definite adhesion of the two lips of the incision. The desired endpoint is a firm but indentable eye. In every case, intraocular pressure (IOP) returns to an acceptable range (below 30 mm Hg) within a few minutes and below 20 mm Hg within 30 to 40 minutes. In a personal series of 100 consecutive cases, IOP was always between 11 and 24 mm Hg by 2 hours postoperative.
Final injection of ceftazidime in the bag is warranted for additional infection prophylaxis. With a 2.75-mm incision, foreign body sensation for 2 to 3 weeks postoperatively over the temporal limbus was not uncommon among my patients. This has been greatly reduced with the 2.2-mm incision.
DOWNSIDES OF A SMALLER INCISION
There have been some disadvantages to the use of a smaller incision size. Irrigation inflow is reduced by approximately 25% (Figure 2), and the anterior chamber is more susceptible to surge.
With the same phaco tip in a smaller sleeve, there is less space between tip and sleeve, which means reduced irrigation. Therefore, the use of a thinner ultrasound tip is advisable. However, sizable nucleus fragments can obstruct a tip body smaller than 0.8 mm in diameter. Additionally, a smaller tip means less ability to hold onto nucleus fragments, which must be compensated with an increase in vacuum.
Additionally, we need a smaller-diameter cartridge for injection of the IOL as well as smaller capsulorrhexis forceps.
MICROCOAXIAL PHACO
Microcoaxial phaco, introduced by Alcon Laboratories, Inc. (Fort Worth, Texas), has addressed many potential disadvantages of smaller cataract incisions. The company developed a microsleeve, the UltraSleeve, that fits into a 2.2-mm incision. It has a thinner wall and larger infusion bores (Figures 3 and 4).
My initial experience with phaco through a 2.2-mm incision, 2 years ago, was not without reservations. The chamber stability through the smaller wound was not as good as with the Infiniti Vision System (Alcon Laboratories, Inc.) through a 2.75-mm incision. After a learning curve, I chose lower phaco parameters. The bottle height was raised to 130 cm, and fluidics settings were reduced. But I was still unsatisfied.
Before Alcon Laboratories, Inc., launched its microcoaxial technology, so-called bimanual microincision cataract surgery (MICS) was proposed, in which the infusion instrument is separated from the ultrasound and aspiration instrument to reduce incision size. The MICS approach has not shown unambiguous and definite advantages over the more widely used coaxial approach. Although some eminent practitioners currently prefer MICS, there are no signs that most surgeons will adopt this practice.
The release of the Ozil torsional handpiece technology (Alcon Laboratories, Inc.) improved the overall efficiency of fluidics. The reduction of nucleus repulsion without the need to raise the vacuum level significantly increases the followability of nuclear fragments. There is no more chasing pieces around the anterior chamber. I use the burst mode, which reduces power and decreases the chance of incision burn. With its thinner body, the mini-flared tip (Figure 5) stabilizes the inflow, although it is slightly more cumbersome.
My basic technique is vertical chopping. At the beginning of surgery, the superficial cortex is removed using 180 mm Hg vacuum with 30% torsional motion activated when useful.
For chopping, the settings are 100% amplitude, 30 cc flow, 20 milliseconds burst (minimum off-time 350 milliseconds), and a maximum vacuum of 450 mm Hg. Vacuum and Ozil are surgeon-controlled. Bottle height is set at 120 cm.
For very hard 4+ nuclei only, I blend Ozil with 20% longitudinal ultrasound to speed up the procedure. More liberal use of Ozil power on denser nuclei allows more efficiency, reducing the potential for clogging of the line.
A high vacuum and low Ozil power tend to break off larger pieces at the tip opening before they have been completely emulsified. To avoid this, I suggest reducing the excursion of footswitch position three to approximately 20%. When emulsifying chopped fragments, using the power of Ozil before reaching full vacuum significantly reduces the potential for clogging.
After hydrodissection, hydrodelamination helps to disassemble the nucleus from the epinucleus.
I find that chamber stability during I/A is still less than satisfactory. The size of the I/A instrument should be reduced because it is currently too large in the 2.2-mm sleeve.
LENS IMPLANTATION
Alcon Laboratories, Inc., has designed a new D cartridge to facilitate IOL injection through 2.2-mm incisions without losing the simplicity of current inserters (Figure 6).
With the C cartridge, injection of an AcrySof IOL (both manufactured by Alcon Laboratories, Inc.) through a 2.2-mm incision required a wound-assisted procedure. Counterpressure with a spatula through the sideport incision is also required to ensure stable continuity from the cartridge funnel to the corneal tunnel wall. Sometimes, the procedure was not smooth, and I needed to reload the IOL.
The D cartridge has a thinner tip that fits within the 2.2-mm wound, rather than lying over the incision mouth from outside (Figure 7). With this device, AcrySof injection is now trouble-free. The AcrySof IOL can be injected in one motion, with no need for injector rotation or double advancement of the plunger. The thinner profile of the aspheric AcrySof IQ or the new Restor Aspheric (Alcon Laboratories, Inc.) is delivered even better with the D cartridge.
The UltraSleeve, the Ozil torsional handpiece, the microtip, and the D cartridge act as a harmonized surgical system, designed to provide the best performance with a 2.2-mm incision for microcoaxial cataract surgery. With these pieces in place, the learning curve with the new system should not exceed 20 to 30 cases.
I believe 2.2-mm incisions may become a new standard in phacoemulsification. Microcoaxial phaco with this system is safe, provides predictable outcomes, and is as easy as current 2.75-mm incision techniques.
Antonio Scialdone, MD, is Director of the Ophthalmic Hospital, Milan, Italy. Dr. Scialdone states that he has no financial interest in the products or companies mentioned. He may be reached at ocuscialdo@fastwebnet.it.
