Compared with the larger incisions required in one-handed coaxial phacoemulsification, the sum of the two incisions used in bimanual phacoemulsification is not equal to the sum of their length. The arc length of the widest incision in both cases should also be compared. The sideport incision used in bimanual phaco causes virtually no astigmatism of its own, and when placed at 90° it even compensates for part of the astigmatism induced by the main incision.
Coaxial surgery requires that a larger incision be made to compensate for the wider diameter of the phaco tip. Reducing the diameter of the tip means using more suction, raising the bottle height, and increasing the flow inside the eye. These elevated parameters may possibly cause more damage to the corneal endothelial cells and the retina, which may lead to microcystic macular edema.
The main reason I chose to convert to microincision cataract surgery (MICS) is simply because the main incision is smaller. A smaller incision leads to less iris prolapse, and to less induced astigmatism.
Second, similar to why I prefer eating with a knive and fork, I believe that operating bimanually is simply easier to perform. With bimanual phaco (Figure 1), the second handpiece can be used either as a manipulator or a cracking device, and the inflow itself acts as an extra tool to direct the lens fragments toward the aspirating handpiece (Figure 2).
MY MICS PROCEDURE
I call the technique I am using now the biaxial bimanual cool mini incision technique (BICONI). Most cases are done under topical anestesia.
I make my main incision (1.75 mm wide) temporally. The sideport incision, located at the 12-o'clock hour, is then made 1 mm wide. I keep sitting at the 12-o'clock position and hold the phaco handpiece in my right hand when working in a right eye and in my left hand when working in a left eye—this is the best position for bimanual surgery. This hand arrangement creates the most possible room for my phaco handpiece and avoids the task of changing positions or programming for right and left eyes.
I perform the capsulorrhexis with a bent needle through the sideport incision. Phaco is then performed with the Megatron (Geuder AG, Heidelberg, Germany), on cool phaco mode with a maximum phaco power of 55%. The foot pedal is set up for dual linear use, delivering phaco energy only when necessary by moving the foot pedal sideways. This setup has dramatically reduced my effective phaco time.
The settings I use to carve the nucleus are low vacuum (110 mm Hg) and bottle height (55 cm). I am currently using the divide and conquer technique for hard nuclei and a modified single-split technique for softer (Figures 3 and 4). In my other hand, I am using a high-flow irrigation handpiece (Katena Products, Inc., Denville, New Jersey).
In my second mode, I use a high linear vacuum (250 mm Hg) and a bottle height set at a maximum of 65 cm. My preferred phaco tip for normal as well as hard nuclei is 1 mm in diameter and has a slightly widened end (Geuder AG). Usually, my effective phaco time is between 0.5 and 2 seconds, except for very hard nuclei where I sometimes need up to 4 seconds. Using very low parameters and a slower phaco time helps me to maintain better control. The setup of these parameters is more critical in small-incision surgery because they depend on the phaco machine, the size of the phaco tip, the irrigation device, the height of the infusion, and of course on the size of the incisions.
I am currently using bottle small-incision len models, including the Acri.Tec 46LC plate lens (Carl Zeiss Meditec AG, Jena, Germany), MicroSlim (PhysIOL, LiÈge, Belgium), and MI60 (Bausch & Lomb, Rochester, New York). For most cases, I use the Medicel (Luchten, Switzerland) injector with a 1.8-mm cartridge.
I still enlarge the incision up to 2 mm for IOL insertion because forcing a lens through a smaller incision may damage the lens or its haptics. The future of MICS shall bring us better cartridges for a safer implantation through an incision size less than 1.8 mm.
Robert J. Van Horenbeeck, MD, is President of the Belgian Society of Cataract and Refractive Surgery, is Head of the Anterior Segment Department at the St. Augustinus Ziekenhuis Hospital, and is in private practice at Oogkliniek-Antwerpen, Anwerp, Belgium. Dr. Van Horenbeeck states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +32 3 239 6767; fax: 32-3-239 8300; e-mail: rob.vanhorenbeeck@skynet.be.
