Trends in phacoemulsification

October 1, 2005

The fundamental issue of wound integrity has dissuaded me from pursuing further research and development of this technique

Here, Khiun Tjia, MD of Isala Clinics, Zwolle in The Netherlands shares his experiences of currently available techniques and speaks of an exciting new concept in phacoemulsification, which could change surgeons' attitudes towards microincisional cataract surgery.

Cataract surgery has evolved considerably, from 12 mm incision intracapsular extraction to the modern small incision phacoemulsification with foldable intraocular lenses (IOLs).

Bimanual phacoemulsification: Are two incisions better than one?

Bimanual phaco was developed with this thought in mind - how do we make incisions smaller without compromising efficacy? The answer: make two small incisions instead of one that is larger. This technique has gained a significant amount of attention in recent years, with many surgeons becoming enticed initially by the promise of smaller incisions. The technique uses two rigid instruments with separated irrigation and aspiration cannula pathways introduced through two approximate 1.5–1.8 mm incisions. One benefit is that the instruments seal off both incisions to an extent, assisting the efficiency of fluid streams inside the eye during phacoemulsification.

Further, reduction of incision size is theoretically an improvement in several ways; surgical trauma can be reduced, as well as incidence of induced astigmatism. In certain cases in reality, however, surgical trauma can be equivalent or worse with bimanual phaco compared with coaxial phaco because of extended surgical times and more complex manipulation inside the anterior chamber. In addition, induced astigmatism is no longer a significant issue with suture-less incisions below 2.75 mm.

The greatest drawback of this technique, in my opinion, is the way these rigid instruments stretch and tear the tight incisions during manipulation. This undoubtedly compromises the wound integrity and potentially leads to late leakage and a higher risk of endophthalmitis - a complication which is alarmingly on the increase.

A further disadvantage of a separate irrigation cannula through microincisions is a reduced infusion, which limits the aspiration flow. This lengthens the surgical time and has a negative influence on followability and control of occlusion during nucleus removal.

My personal experience with bimanual phaco was relatively satisfactory, however, the fundamental issue of wound integrity has dissuaded me from pursuing further research and development of this technique.

Micro-coaxial phacoemulsification: Let's use smaller sleeves instead

Micro-coaxial phacoemulsification is a technique that aims to reduce incision size by using a reduced diameter infusion sleeve on the phaco tip. The soft-sleeved phaco tip does not stretch incisions significantly and we know that well constructed 2 or 3 step (near) clear corneal incisions are 100% watertight, even without stromal hydration. Even 0.9 mm incisions with bimanual I/A rigid cannulas need to be stromally hydrated to stop wound leakage. Smaller sleeves also reduce irrigation flow compared with conventional sized sleeves by as much as 35% and this has a negative impact on fluid dynamics.

Ultrasound emulsifies the (hard) nuclear pieces when the metal phaco tip rim comes into direct contact with the nucleus. During sculpting or embedding of the nucleus, this is automatically achieved by a constant pressing of the tip towards the nucleus.

During quadrant removal, however, the longitudinal action of each ultrasonic stroke of the phaco tip, not only destructs material, but it also repels the nucleus away from the phaco tip and the constant aspiration flow and vacuum force upon occlusion needs to keep the nuclear material in close contact with the tip.