The quest for astigmatically neutral incisions has gained significant interest in recent years. Several studies have shown that incisions smaller than 2.2 mm are astigmatically neutral,1,2 suggesting that there is a significant benefit to microincision cataract surgery (MICS) techniques. MICS brings incision sizes down to 1.8 mm, regardless of the whether the surgeon uses a bimanual MICS or a microcoaxial technique.
This shift to smaller incisions has caused the need for changes to existing technology. First, the fluidics on phacoemsulsification systems, as well as the sensors and processors controlling the fluidics, required adjustments to avoid surge and anterior chamber instability. Second, the heat produced by the friction of the phaco needle during smaller incisions needed to be controlled. Third, smaller IOLs that fit through these microincisions were not available—thus, new IOL designs and injectors needed to be designed. Finally, surgeons had to adjust their mindsets that smaller incisions help patients only if the postoperative visual results and safety were consistent with what we were able to offer with traditional, larger-incision cataract surgery.
INSTRUMENTS FOR MICROCOXIAL
At the Belgian Society of Cataract and Refractive Surgery meeting in January 2008, the new Intrepid Microcoaxial System (Alcon Laboratories, Inc., Fort Worth, Texas) was introduced. The Intrepid system is a chain of instruments for microcoaxial phaco that include the incision knife, phaco needle and sleeve, as well as an IOL and injector that are matched to each other for microincision insertion. The minimum incision size recommended by the company is currently 2.2 mm, but surgery through incision sizes as small as 1.8 mm have been reported anecdotally.
IMPROVED FLUIDICS
The Infiniti Vision System (Alcon Laboratories, Inc.; Figure 1) will soon be available with the new Intrepid Fluid Management System (FMS). The ingenuity of the Intrepid FMS lies in its tubing. The collapsing and expanding of the tubing during occlusion and occlusion break under high vacuum conditions are controlled by changing the stiffness of the tubing material. Together with the excellent pump and processor available on the Infiniti Vision System, surge and anterior chamber collapse during small incision coaxial surgery are reduced.
The Ozil torsional handpiece (Alcon Laboratories, Inc.) addresses the problem of heat by delivery of side-to-side oscillating ultrasonic movement. The addition of Ozil has enhanced the efficiency of the phaco needle and dramatically reduced the heat produced by the needle to a low, cornea-safe level. The only possible drawback to the Ozil handpiece is the learning curve that some surgeons may have in using the bent Kelman tip. Alcon will soon release mini-flared tips to accommodate those surgeons who prefer less angle.
IOL, INJECTOR FOR MICROINCISIONS
The AcrySof IQ IOL (Alcon Laboratories, Inc.) platform has been widened with the introduction of aspheric and toric designs. These IOLs can be introduced through the same small incision size of 2.2 mm with the aid of the Monarch III D cartridge (Alcon Laboratories, Inc.; Figure 2) and appropriate injectors, such as the Royale II Unihand Spring Injector (ASICO, Westmont, Illinois) and the DK7797-2 (Duckworth & Kent, Hertfordshire, UK). The nozzle tip of the Monarch III D cartridge is 33% smaller than the Monarch II C and fits snugly in the entrance of the 2.2-mm incision.
The smaller nozzle tip is important because it reduces the counteraction required for IOL injection. The heavy pushing of the injector and consequent squeezing of the eye required to inject the IOL have long been my personal reasons not to reduce my incision size. Now that I am using the Duckworth & Kent injector with the Monarch III D cartridge (Figure 3) through a 2.2-mm clear corneal incision, I no longer hesitate to perform microcoaxial phaco (Figure 4).
Johan Blanckaert, MD, is a Cataract Surgery Consultant in the Ophthalmology Department of the University Hospital UZ Leuven, and in private practice at The Eye & Refractive Center, Belgium. Dr. Blanckaert states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +32 57- 202300; fax: +32 57 221656; e-mail: oogartsen@pandora.be.
