Getting Familiar With EVA

We have had the EVA vitrectomy system (DORC) in our practice for roughly 3 months at the time of this writing, and we have learned a lot about the machine, including ways to modify it to maximize its efficiency. This article reviews some of this instrument’s key features and offers tips that we have found valuable.

USEFUL FEATURES

Twin Duty Cycle

EVA’s twin duty cycle (TDC) technology (Figure) provides a high cut rate of 16 000 cpm with a constant open duty cycle of 92%. It significantly reduces the time to complete a core vitrectomy when compared with the Associate (DORC) and other non-TDC machines. A complete core vitrectomy with the 23-gauge system and TDC technology takes an average of 3 to 4 minutes.

Given this improvement in efficiency, we have been doing significantly more 27-gauge surgeries with this system. The time to complete a core vitrectomy with the 27-gauge TDC platform comes close to that of a standard 23-gauge procedure with a non-TDC vitrectome. We have found that using 27-gauge instruments requires much less adjustment than initially predicted. As is common with small-gauge surgery, we had an issue with some of the 27-gauge instruments bending, but we resolved the problem with minor adjustments, such as small changes in hand position and the use of a finger on the shaft of the instrument to stabilize it.

The limiting factor in converting more cases to 27-gauge is the finite number of options for forceps, scissors, and other instruments for the 27-gauge ports. Although 27-gauge forceps are evolving, they are not quite as good as our current 23- and 25-gauge forceps. This is more evident when teaching fellows to peel the ILM and ERM, as they have a harder time learning a new skill with more flexible instrumentation. Our solution has been the use of a hybrid system with two 27-gauge ports for the infusion and the light pipe and one 23-gauge port for the dominant hand (Video 1; eyetube.net/v.asp?f=elude). With the 23-gauge port we are able to use the 27-gauge cutter that comes in the pack to perform the vitrectomy, but we can also peel using our standard 23-gauge instruments. The company has stated that it plans to create hybrid packs to fit this model in the future. This will allow us to open a single pack of trocars, so as not to make the hybrid system cost-prohibitive.

Fluid Control

Another particularly useful feature of the EVA is its fluid control system, called VacuFlow VTi, which includes adjustable settings for both peristaltic (flow) control (0-90 cc/min and 0-680 mm Hg at sea level) and venturi (vacuum) control (0-680 mm Hg at sea level). VacuFlow VTi delivers the necessary flow and vacuum without risk of unwanted pulsation or flow.

Video 1: Hybrid System

The EVA software allows the user to create multiple presets, which can be toggled through using the footpedal. We have used the different settings to perform entire vitrectomies for retinal detachments safely and efficiently, all on flow mode. Over an attached retina we can use a flow of 10 cc/min, and the TDC behaves nearly as efficiently as in the vacuum control setting. By switching to a flow of 3 cc/min with a click of a button for a different preset condition, we can easily perform vitrectomy over a detached retina with little mobility (Video 2; eyetube.net/v.asp?=ifahe). We have even created a flow rate setting of 1 cc/min, which we use over particularly mobile retina. This setting allows us to move the cutter right up to the retinal surface with minimal movement of the detached retina.

Software

The EVA software is simple to use, includes voice feedback, and features easy-to-understand graphics on a 19-inch touch screen. Our surgical staff had little difficulty adjusting to the software and was comfortable using it after just a few cases. Additionally, it is easy to program and toggle between unique surgeon settings, such as those described above with regard to multiple flow control settings.

Laser

The EVA vitrectomy system comes with an integrated 532-nm laser tool, which we find offers consistent operation. The settings for the laser are easy to adjust, and the machine includes a wireless laser pedal that can be moved around using a toe hole in the supporting safety guard without having to rely on the circulator. The pedal includes integrated buttons that the surgeon can use to modify the power settings. The EVA also has a setting that allows an indirect laser to be plugged in. This is convenient because it eliminates having to purchase a second laser for the indirect in the OR.

Illumination

There are three independent light output channels with the EVA’s LEDstar technology. This allows surgeons to vary not only the light intensity, but also the color of the light from white to yellow. Some surgeons find operating under gas easier while using a yellow light, but we prefer the white setting for all cases.

Figure. Forward and reverse movements with the EVA’s TDC technology double the cut rate.

MIND THE SETTINGS

When we first began using the EVA, we found that, in some cases, the vitrectomy was not as efficient as predicted. There are many TDC and non-TDC options from which to choose when priming the machine. We learned later that the machine was primed in a non-TDC cutting setting, thus diminishing the efficiency of the cutter. Although it is possible to modify this setting mid-case, the infusion defaults to “off” when this is done, requiring careful attention to the machine at this point in surgery. The TDC cutter is quite efficient, and it is therefore important to keep an eye on the infusion because the port is always open on the cutter. This might lead to using more balanced salt solution than one has used previously; however, it has not been an issue for us.

Video 2: Vitrectomy Over Detached Retina

CONCLUSION

Although we have had the EVA at our surgery center for only a little more than 3 months, we find that it has significantly increased our efficiency and safety in the OR, thanks to the fluidics of the TDC cutter. We have used the EVA in more than 150 cases and we will continue to add to that number with this 27-gauge platform. We also look forward to more innovative features in terms of hardware and software. n

Nicholas D. Chinskey, MD, is a vitreoretinal fellow at The Retina Institute in St. Louis, Mo. He states that he has no relevant disclosures. Dr. Chinskey may be reached at mdchinskey.nicholas@rc-stl.com.

Guarav K. Shah, MD, is the co-director of retina fellowship at The Retina Institute in St. Louis, Mo. He states that he is a paid consultant for DORC, Alcon, Synergetics, Bausch + Lomb, Allergan, and Regeneron. He receives no equity interest or royalties from any company. Dr. Shah may be reached at gkshah1@gmail.com.