Fluidics in modern vitrectomy

Highlights from an expert roundtable meeting can be found in the April issue of Ophthalmology Times Europe.

Over the last few years the maintopics of discussion in ophthalmic surgery have tended to concentrate on things like power delivery, ultrasound modulation, cutting rates or even duty cycle rather than on the understanding of fluidics. However, greater understanding of fluidics is something that has only recently been recognised as being important, together with the decrease in sclerotomy size and the development of new instrumentation in terms of size, cutting speed, illumination and pilot tubes.

Oertli Instruments, a Swiss designer and manufacturer of equipment and instruments has been addressing the fluidics issue for some time and the research work of their head physicist, Dr Gregor Jundt has concentrated on looking at two pump concepts, flow controlled and vacuum controlled, or peristaltic and venturi. Knowledge of the concepts is critical to understanding the mechanics of these pumps.

Flow rate control (in an unoccluded state) keeps fluid turnover in the eye exactly at the rate controlled by the pedal while the vacuum adjusts itself to the lowest level required.

Vacuum control (in an unoccluded state) keeps the suction vacuum of the pump exactly at the level controlled by the pedal while the resulting fluid turnover depends on vacuum, size of aspiration path and condition of material being aspirated.

In the occluded state, there is no difference between the two systems. Oertli's research has indicated that surgeons felt that given the development of the changes, which have been highlighted individually, there was a need to look at these in the round and discuss the ideal vitrectomy and vitreoretinal system and ask if there could be a system suitable for all surgical situations.

Subsequently, a meeting was convened for experts to share their experiences and views in a roundtable discussion in Zurich, Switzerland to review where we are today, the surgical situations that arise and what challenges those present. It also aimed to examine the strategies and methods of treatment open to doctors, what instrumentation is available and what their ideal properties are and also what pump systems and settings were most appropriate.

For their preparation, venturi users amongst the assembled expert panel were asked to work for a period of time with the peristaltic pump while peristaltic users did the opposite. The Oertli OS3 system, which offers switching between pumps on the fly, was used for this purpose.