MICS: no need to compromise on lenses

April 1, 2008

Modern cataract surgery requires the implantation of a lens with design features that ensure stability, excellent biocompatibility and minimal posterior capsule opacification (PCO), using an injector which is safe and predictable, through an incision that is as small as possible. Is this possible without compromising standards? I would argue that it is.

Modern cataract surgery requires the implantation of a lens with design features that ensure stability, excellent biocompatibility and minimal posterior capsule opacification (PCO), using an injector which is safe and predictable, through an incision that is as small as possible. Is this possible without compromising standards? I would argue that it is.

Surgeons should not be reluctant to accept MICS

Progression from extracapsular cataract extraction (ECCE) to phacoemulsification surgery was arduous with a steep learning curve. However, the advantages of better anterior chamber depth control and the smaller incision sizes were so obvious that all surgeons completed the progression sooner or later.

Even after realizing the advantages of MICS, many surgeons have remained reluctant to adapt to it simply because of the paucity of a reliable lens-injector platform which would allow implantation through a 2 mm incision.

The advances of phacoemulsification techniques have continuously placed pressure on lens implant technology to refine the ways and means of implanting lenses through smaller and smaller incisions. In the 1990s, the IOL industry responded with foldable lenses, thereby reducing the final incision size to around 3 mm. Now, in response to the MICS technique, there is a trend towards modifying the design of the lens to allow implantation through sub 2 mm incisions. It has not, however, received universal acceptance.

The MICS advantage

While MICS can reduce incision sizes to around 1.4 mm, the main advantages of MICS lie in the improved fluidics throughout surgery rather than the smaller incision itself. The alternative microcoaxial technique can offer incisions of 2.2 mm but cannot offer such good fluidics because there is no separation of the irrigating port from the phaco tip. In my experience with MICS over the last four years, the following advantages have become obvious to me:

1. The coaxial phaco tip has a fluid jet which may push the lens material away from the tip, the opposite of what the surgeon needs. MICS separates the jet to a side port which can be used to advantage by directing the fluid current in a way which brings the lens material towards the phaco tip. Thus the nucleus fragments engage efficiently and the epinucleus floats away from the posterior capsule safely.

2. In eyes with 'floppy iris', keeping the fluid jet in front of the iris plane will prevent iris ballooning towards a port and risk of a subsequent prolapse. This is not easy to achieve with coaxial phaco.

3. When zonules are compromised, lens fragments and epinucleus can be removed safely without causing additional strain on the zonules by directing the fluid jet to move the nucleus fragments and the epinucleus towards the phaco tip.

4. In eyes with a small pupil, the removal of nuclear fragments and the epinucleus are facilitated by the fluid stream thus reducing the need to venture in to the recesses of the capsule bag.

5. The overall phaco energy used inside the eye is reduced because significant work can be done by the fluid jet.

6. A small incision remains watertight and may reduce the incidence of endophthalmitis.

7. The surgically-induced astigmatism is reduced with smaller incisions.

Almost every modern phaco machine has a mechanism for keeping the phaco tip cool and very few additional instruments are required with MICS. Even if the incision has to be extended just before lens implantation, better fluidic control during the surgery is a good enough reason alone to perform MICS routinely.