VITREORETINAL SURGERY
Insights

The Next Step in the Evolution of Vitrectomy Surgery Technology

By Asheesh Tewari, MD, Kresge Eye Institute, Wayne State University School of Medicine, Detroit, MI, USA

I had the opportunity of using the Enhancing Visual Acuity (EVA) vitrectomy system during a live surgery meeting last year in Frankfurt, Germany. Learning to use the EVA was very simple due to its intuitive design and numerous built-in safety features.

Two-dimensional cutting system with EVA fluid control platform

Combining the novel two-dimensional cutting (TDC) system — for use with a range of small-gauge instrumentation — together with the EVA platform elevates the efficiency of the posterior vitrectomy procedure, allowing cut rates up to 16,000 per minute, and without diminishing the amount of flow that is going through the cannula ports. This means that you can perform vitrectomy more efficiently without compromising safety.

Many of my vitreoretinal surgical cases involve diabetic tractional retinal detachments, which require careful maneuvers at the vitreoretinal interface. I want to be able to position the vitrectomy probe right in between the fibrovascular membrane and the surface of the retina. If there is too much vacuum at a particular cut rate, there is the risk that part of the retina may enter the port, creating an iatrogenic retinal break. Using the EVA system set at a low flow control rate and the TDC system, the risk of creating a retinal break is minimized.

Vacuum response time
EVA vacuum control mode (0-680 mmHg @ sea level) allows fast rise time of 300 msec.
Source: DORC International

Choice of vitrectomy machine and cutter matters

Choice of vitrectomy machine and vitreous cutter does matter in vitreoretinal surgical practice. Using the EVA platform, the surgeon has more precision and control because of VacuFlow fluidics control technology. This provides an advanced fluid control-based system and a choice of vacuum and flow modes. The EVA VacuFlow VTi technology represents a big step forward, as you don’t see the same level of sophisticated flow control capability in other vitrectomy machines.

The engineering technology behind earlier-generation and even current vitrectomy machines is built on either a venturi-based or peristaltic pump system. Using venturi-based vitrectomy machines, the surgeon can control cut rates and vacuum levels in a way to try to control the amount of flow channeled through the instrumentation port — but you never actually really knew how much flow was coming through, it was largely based on guesswork. But with a flow control approach featured in the EVA system, you can precisely set the flow rate coming through the port and the machine will adapt to the proper cutting rate and the proper vacuum needed to maintain consistent flow. It is a more elegant and sophisticated way of having that precision and control while you are performing surgery. For delicate intraoperative maneuvers on the surface of the retina or at the vitreoretinal interface in the retinal periphery, having the extra level of control means that there is a decreased chance of developing intraoperative complications.

Constant aspiration flow at the end of the probe tip offers the benefit of steady flow throughout the entire surgery. The amount of flow produced traditionally with a venturi pump system will vary depending on the viscosity of the substance involved, because you are controlling just two variables, cut rate and vacuum, but the variable that you really want to control is how much flow you have. With the EVA system, when you set the flow to say 4 cc/min, it doesn’t matter whether you’re in vitreous or in fluid, the machine automatically adjusts the variables to ensure that the desired flow rate is carefully maintained.

I use predominantly 23-gauge procedures for vitrectomy surgery, although I have started to adopt a hybrid approach in some of my diabetic patients — the 27-gauge instrument tip is so small that it allows the surgeon to access the small planes between the retina and fibrovascular membranes. I have performed some hybrid 23/27-gauge vitrectomy surgery, using a 23-gauge procedure for vitreous removal and then for working on the surface of the retina, use a 27-gauge vitrectomy probe. It adds extra precision and control when dissecting these membranes. As a retina surgeon, my goal is to perform an efficient surgery that provides the best anatomic and visual outcomes, while minimizing any intraoperative complications.

Safe, simple and effective

In my mind, one of the leading features of the EVA platform is the VacuFlow VTi precision control technology. But other notable features are the LEDStar light source, Automatic Infusion Compensation (AIC), and the integrated 532 nm laser with wireless foot pedal.

The case that I performed using EVA in Frankfurt involved a diabetic tractional retinal detachment patient and I found the built-in LEDStar endoillumination to be impressive. This LED light source provides many lumens of light but has a safety profile that is highly favorable compared to xenon light sources. LED-based illumination is also an asset when using chandelier illumination for bimanual surgical cases, freeing up both hands to perform complex peeling procedures and having more than sufficient light to illuminate the entire inside of the eye.

The machine’s AIC ensures safe and stable IOP control throughout vitreous surgery procedures.

When you increase the amount of vacuum/aspiration rate within the eye, there is risk of creating hypotony if the infusion pressure is too low. With the AIC system, hypotony is avoided since EVA will adjust the infusion pressure automatically in response to the amount of fluid being removed from the eye. It is sophisticated enough that it will maintain the correct pressure even if lens fragments or silicone oil bubbles obstruct the infusion line. Operationally, the AIC system has a great safety record and is effective as a safety measure against hypotony.

EVA platform is easy to learn

The EVA vitrectomy machine will not involve a steep learning curve for surgeons migrating from other commercially available vitrectomy surgery platforms. Whether you have been using the DORC Associate previously or using a different vitrectomy machine, the ergonomic design, integrated touch screen and setting control system are all highly intuitive.

With regard to fluidics stability, in my mind, I feel vitrectomy surgery can be done more safely using flow control. Surgery involves many different variables, and the vitrectomy machine used is just one of many influencing components that can help add a protective dimension.

Overall, the EVA vitrectomy machine is very efficient at removing vitreous. It allows you to do so in a controlled fashion, and with decreased risk of vitreous traction and iatrogenic retinal breaks. ■