VITREORETINAL SURGERY
Insights

Transition Toward Flow-based Vitrectomy

Interview with Brian C. Joondeph, MD, Colorado Retina Associates, Denver, CO, USA

Q. In your hands, why does the method of aspiration fluid control matter in vitrectomy surgery?

Aspiration vacuum and flow control do matter during posterior surgery because your are removing vitreous from the eye and in many cases the vitreous is attached to the retina somewhere. As you remove vitreous you are pulling on it and perhaps pulling on the retina: so the goal is to remove the vitreous as efficiently and as safely as possible without exerting undue retinal traction, which could lead to retinal tears or retinal detachment.

Many of the principles underlying the new EVA aspiration platform are already in place in the earlier-generation Associate ophthalmic surgery machine for example. We are therefore familiar with the benefits of flow control during vitrectomy.

The advantage of venturi-style aspiration vacuum control is that you achieve high levels of suction, allowing you to remove the vitreous relatively quickly. The disadvantage is that once the vitreous is in and through the probe and you are aspirating, there is much less resistance during the surge; if you are working near a detached mobile retina, that surge can draw the retina into the cutter probe. So that is one of the dangers of having that sudden surge when you encounter anything with less or reduced resistance.

That is where the flow-based aspiration approach offers a distinct advantage, because the flow through the tubing is constant whether it is vitreous or saline that is being aspirated. Also, faster vitreous cut rates draw less vitreous into the vitrectome before cutting, meaning lower traction. With current generation vitrectomy machines, the higher cut rates now achievable are advantageous, allowing smaller bites of vitreous and exerting less traction on the retina as a result.

Q. What’s your experience using aspiration vacuum and flow control?

I certainly agree that aspiration vacuum control allows slightly faster vitreous removal during a core vitrectomy procedure. However, even during a core vitrectomy procedure, a surgeon might suddenly hit a pocket of saline and experience a surge of fluid, which can then create fluid currents in the eye or even collapse the eye with potential adverse effects. So my preference personally is to use a flow-based mode for vitrectomy most of the time, and thereby eliminate this potential problem entirely.

But that hasn’t been my approach all the time, as earlier-generation vitrectomy machines didn’t provide an option for aspiration flow control - all we could do then was control aspiration with the foot pedal and keep the cut rate high. So this has involved a kind of paradigm shift in transitioning toward a flow-control vitrectomy technique, which I believe to be a safer technique and without any sacrifice in surgical efficiency.

Q. Notable trends in equipment and practice?

Having the option of vacuum control and flow aspiration control available during vitrectomy is nonetheless valuable, as a retina surgeon will encounter different situations where one particular aspiration control mode may be preferable to another. One example is in the creation of a posterior vitreous detachment where high suction may be needed to engage and hold on to the posterior hyaloid while elevating it from the retinal surface.

Flow controlled aspiration is particularly useful in cases with retinal detachment and mobile, elevated retina. Flow control allows the surgeon to pass the vitrectomy tip close to the surface of the detached retina to trim the vitreous as close to the vitreous base as possible, including around the retinal tear. With flow-based aspiration, there is minimal movement of the underlying retina whereas in vacuum based aspiration, the retina can ‘jump’ into the tip of the cutter leading to an iatrogenic retinal break. Even in areas of attached retina, excessive aspiration during peripheral vitreous removal can cause new retinal breaks. Flow-based aspiration reduces this risk and makes the overall procedure safer.

There is a trend toward faster vitrectomy techniques and safer vitrectomy to minimize the risk of complications and poor outcomes. Part of the explanation, at least for macular surgery, is a practice shift toward limiting the extent of the vitrectomy in order to leave some vitreous in the eye, especially posterior to the lens, to reduce cataract progression. Membrane staining makes peeling faster too. Smaller-gauge sutureless vitrectomy surgery, by eliminating the need to create and suture sclerotomies, and expanded instrumentation choice have also undoubtedly contributed to this momentum toward faster effective vitreoretinal surgery. ■