Two-Dimensional Cutting (TDC) Vitrectome: In Vitro Flow Assessment and Prospective Clinical Study Evaluating Core Vitrectomy Efficiency versus Standard Vitrectome

FLUIDIC PERFORMANCE OF A DUAL-ACTION VITRECTOMY PROBE COMPARED WITH A SINGLE-ACTION PROBE

PURPOSE

To assess flow rates, nearfield effects, and traction of a dual-cutting 20,000 cpm vitrectomy probe (HYPERVIT, Alcon) versus a single-cutting 10,000 cpm probe (Advanced ULTRAVIT, Alcon).

METHODS

Flow rates were evaluated for 25+ and 27+ gauge probes using balanced salt solution or porcine cadaver vitreous (biased open, 50/50, and biased closed duty cycles). Probes were suspended in an open beaker, and flow rates were calculated using a precision balance. Nearfield effects and flow pulsatility were assessed using a validated simulation model based on experimental microparticle image velocimetry. Traction was assessed by attaching vitreous to a cantilever beam and measuring the deflection of the beam.

RESULTS

For HYPERVIT probes, aqueous flow rates were similar across all cutting rates. Vitreous flow rates increased with increasing cutting rates. At maximum cutting rates, aqueous flow was 62%-67% greater (25+) and 63% greater (27+) with HYPERVIT versus Advanced ULTRAVIT ( P < 0.05); vitreous flow was 44%-47% greater (25+) and 26%-32% greater (27+) with HYPERVIT versus Advanced ULTRAVIT ( P < 0.05). Nearfield effects were reduced, and peak traction forces were significantly lower for HYPERVIT versus Advanced ULTRAVIT ( P < 0.05).

CONCLUSION

Significantly greater aspiration flow, reduced nearfield effects, and reduced traction were observed with dual-action versus single-action probes.

Comparisons of flow dynamics of dual-blade to single-blade beveled-tip vitreous cutters

INTRODUCTION

To compare the flow dynamics of the dual-blade to the single-blade beveled-tip vitreous cutters.

METHODS

The aspiration rates of balanced salt solution (BSS) and swine vitreous were measured for the 25-gauge and 27-gauge dual- and single-blade vitreous cutters. The flow dynamics of BSS and diluted vitreous mixed with fluorescent polymer at the maximal cutting rates and the reflux of BSS were measured in images obtained by a high-speed camera. The distal end of the cutter was defined as the head end.

RESULTS

The aspiration rates of BSS and vitreous by the 25- and 27-gauge dual-blade cutters were significantly higher than those of both single-blade cutters at the maximal cutting rate (all P≤0.01). The mean aspiration flow of BSS in front of the port from a lateral view was significantly faster for both dual-blade cutters than for both single-blade cutters (P=0.003, P=0.019). The angle of the mean flow of BSS of both dual-blade cutters was from the distal end (P<0.001, P<0.001) but that of the single blade-cutters was from the proximal end. The velocity and angle of the mean reflux flow of both types of cutters were not significantly different. The mean aspiration flow of diluted vitreous was significantly faster for 25-gauge dual-blade cutters with the angle more from the proximal end and 27-gauge dual-blade cutters more from the distal end than both single-blade cutters (P=0.018, P=0.048).

CONCLUSION

The dual-blade beveled-tip vitreous cutters improve the efficiency of the vitrectomy procedures and maintain the distal aspirating flow by the beveled-tip.

In Vitro Comparison of Various High-Speed Vitrectomy Machines Using Dual Blade Cutters

Objectives

The objective of this study is to compare various dual blade vitrectomy cutters for their efficiency in an in vitro setting.

Methods

In this in vitro experimental study, we compared various vitrectomy systems including EVA (Dutch Ophthalmic Research Center, Zuidland, The Netherlands), REVOLUTION (Optikon 2000, Inc., Rome, Italy), and OS4 (Oertli Instrumente AG, Berneck, Switzerland) in terms of efficiency in vitreous cutting and aspiration for various vitreous substitutes. These substitutes included water, chicken egg albumin, and goat vitreous. We only used 23-gauge dual blade cutters across all platforms to maintain uniformity. The cutting and aspiration efficiency was measured across various cut and vacuum settings of vitrectomy machines and measured as mass aspirated in a given time. Data analysis included comparing the amount of mass aspirated by these machines at preset cut and vacuum settings.

Results

Scatter plots showed a comparable mass of water aspirated by the EVA and REVOLUTION at 1000 to 5000 cuts per minute at a constant vacuum of 500 mm Hg whereas OS4 aspirated lesser mass at similar settings. Same trends were noted for goat vitreous for EVA and REVOLUTION but aspirated mass of albumin fluctuated widely across various platforms. At peak machine settings, REVOLUTION showed superiority across all three vitreous models due to its higher peak settings. The area under curve (AUC) analysis showed no significant differences among machines for water and goat vitreous at comparable settings but results were fluctuating for egg albumin.

Conclusion

Employing higher cut rates for dual blade cutters results in better efficiency of vitrectomy machines.

Comparison of modern high-speed vitrectomy systems and the advantages of using dual-bladed probes

Purpose

This study analyzes the efficiency of different vitrectomy systems and compares single with double-bladed cutters.

Methods

The systems EVA™ (DORC), Constellation^® Vision System (ALCON), megaTRON S4^HPS (Geuder) and Stellaris^® PC (Bausch and Lomb) were used. We chose 20G and 23G probes, since not all systems had switched to a smaller G at the time the study was conducted in 2016. Cut rates were varied in increments of 1000 cuts/min from 500 cpm to the system’s maximum and vacuum pressures were varied in increments of 100 mmHg, from 100 to 600 mmHg up to the individual system’s maximum. In this study water, egg white, Pluronic^®−F127 gel and isolated porcine vitreous were used as models of human vitreous. The vitrectomy efficiency was calculated from the aspirated mass (g) within 30 s. The aperture of the different vitrectomy probes was filmed with a high-speed camera.

Results

The area under the curve analysis showed differences in efficiency between vitrectomy systems. For water, a reverse relationship between the aspirated mass and cut rate was shown. By contrast, for most systems aspirated egg white and porcine vitreous showed a non-linear increase or decrease for 4000 cpm and above. For all vitreous surrogates, EVA™’s double-bladed probe aspirated significantly (p < 0.001) more vitreous than its mono-bladed probe. Video recordings showed less vitreous traction for double- in contrast to single-bladed probes.

Conclusion

We can demonstrate differences in the efficiency of vitrectomy depending on the vitrectomy system used. Double-bladed probes were more efficient and probably safer than single-bladed probes.

Comparison of Characteristics and Clinical Outcomes in 27-Gauge versus 23-Gauge Vitrectomy Surgery

Purpose

To compare characteristics, clinical outcomes and complication profiles of a cohort of patients undergoing 27-gauge versus 23-gauge vitrectomy surgery at a tertiary medical center in the Middle East.

Methods

This is a retrospective comparative study of indication-matched patients undergoing 27-gauge versus 23-gauge pars plana vitrectomy for a set of predetermined diagnoses. Data including indications for surgery, clinical exams, visual outcomes, and complications were documented and analyzed.

Results

A total of 22 patients who had 27-gauge pars plana vitrectomy were compared with 44 patients who had 23-gauge surgery for matched indications by a single retina surgeon. Mean follow-up was 14 months after surgery. Indications included macular pucker, macular hole, and vitreous hemorrhage. Both the rate of hypotony at postoperative day 1 and the need for sclerotomy stitching at the end of surgery were significantly more frequent in 23-gauge compared to 27-gauge cases (25% in 23-gauge compared to 0% in 27-gauge (p=0.012) and 18% in the 23-gauge compared to 0% in the 27-gauge (p=0.045), respectively). The mean duration of surgery was similar among groups (35 mins in the 27-gauge group versus 39 mins in the 23-gauge group (p=0.116)), and all eyes achieved anatomic success. In the 27-gauge group, best-corrected visual acuity improved from a mean of 20/90 at baseline to a mean of 20/40 at 1 month (p=0.005) and in the 23-gauge group from a mean of 20/95 to 20/50 (p=0.001) with no statistical difference between the groups.

Conclusion

In this cohort of patients undergoing vitrectomy at a tertiary eye center, the rate of hypotony and the need for sclerotomy suturing were significantly less in the 27-gauge group versus the 23-gauge group. Surgical outcomes were similar in both study groups. The use of the novel 27-gauge instrument system is useful in selected vitreoretinal diseases and appears comparable to the widely used 23-gauge system.

Multicenter survey of sutureless 27-gauge vitrectomy for primary rhegmatogenous retinal detachment: a consecutive series of 410 cases

PURPOSE

To evaluate the surgical outcomes of the 27-gauge (G) vitrectomy system for the treatment of primary rhegmatogenous retinal detachment (RRD).

METHODS

This retrospective consecutive series multicenter study involved a total of 410 eyes of 406 patients who underwent 3-port transconjunctival 27G pars plana vitrectomy (PPV) for RRD between November 2014 and December 2016 and who were followed for a minimum of 3 months postoperative. The main outcome measure was primary reattachment, with the secondary outcome measures being final reattachment, improvement of visual acuity (VA), intraocular pressure (IOP), intraoperative and postoperative complications, and surgery time.

RESULTS

Of the 410 treated eyes, primary reattachment was achieved in 392 (95.6%) and final reattachment was achieved in 410 (100%). In 226 eyes (55.1%) with macula-on RRD, the mean logarithm of the minimum angle of resolution (logMAR) VA improved from 0.16 ± 0.51 pre-surgery to 0.02 ± 0.14 post-surgery (P = 0.11). In 184 eyes (44.9%) with macula-off RRD, logMAR VA improved from 1.06 ± 0.77 pre-surgery to 0.26 ± 0.35 post-surgery (P < 0.001). Following surgery, the mean IOP was highest at 1 day (15.7 ± 7.0 mmHg) postoperative. In all eyes, surgery was concluded without the use of sutures or the need of conversion to a larger-gauge instrument. Although hypotony was observed in 14 (3.4%) of the 410 treated eyes at 1 day postoperative, it spontaneously resolved within 1 week without additional surgical intervention. No postoperative complications such as infectious endophthalmitis were observed throughout the follow-up period.

CONCLUSION

Our findings show that 27G PPV is both safe and effective for the treatment of primary RRD.

IN VITRO FLOW ANALYSIS OF NOVEL DOUBLE-CUTTING, OPEN-PORT, ULTRAHIGH-SPEED VITRECTOMY SYSTEMS

PURPOSE

To analyze the performance and flow characteristics of novel double-cutting, open-port, 23-, 25-, and 27-gauge ultrahigh-speed vitrectomy systems.

METHODS

In vitro fluidic measurements were performed to assess the volumetric aspiration profiles of several vitrectomy systems in basic salt solution and egg white.

RESULTS

Double-cutting open-port vitrectomy probes delivered stable aspiration flow rates that were less prone to flow variation affected by the cutting speed. Increase in cutting frequency to the maximum level resulted in flow reduction of less than 10% (0.0%-9.5%). Commercially available 23-, 25-, and 27-G double-cutting probes exhibited higher egg-white and basic salt solution flow rates at all evaluated cut rates, with aspirational efficiencies being 1.1 to 2.9 times the flow rates of standard single-blade vitrectomy probes of the same caliber at the maximum preset vacuum. The highest relative differences were observed at faster cut rates.

CONCLUSION

The newly introduced double-cutting open-port vitrectomy probes delivered stable aspiration flow rates that were less prone to flow variation affected by the cutting speed. The fluidic principle of constant flow even at the highest cut rates and low vacuum levels might impact surgical strategies, especially when performing manipulations close to the retina.

Fluidics of Single and Double Blade Guillotine Vitrectomy Probes in Balanced Salt Solution and Artificial Vitreous

PURPOSE

To assess the fluidics of double-vitreous cutter blade (DB) compared with single-blade (SB) guillotine with 23-, 25-, and 27-gauge vitrectomy probes. To assess flow characteristics and flow rates in viscous and viscoelastic fluids.

METHODS

We used Particle Image Velocimetry to measure the flow field close to the tip of each cutter probe and we derived kinematic quantities of interest, such as kinetic energy and acceleration. We performed measurements both on a balanced salt solution (BSS) and on a viscoelastic artificial vitreous (AV).

RESULTS

The flow rate is significantly higher with DB than SB vitrectomy probes, for a given pumping pressure and cutting rate. The fluid flow observed is very different between BSS and AV tests.

CONCLUSIONS

The DB has more efficient fluidics than SB vitrectomy probe in all tested conditions. Fluid acceleration depends on the cutting frequency, especially in the case of measurements in AV. The flow rate strongly depends on the pressure and it is little affected by the cutting frequency, in a range of clinical interest. The 27-G DB produces flow rates similar to the 23- and 25-G SB, with significantly smaller acceleration. The flow induced in the AV is different from that in BSS and oscillates at different frequencies.

TRANSLATIONAL RELEVANCE

DB cutters prove to be more efficient in terms of lower acceleration for a given flow rate. The latter is mainly controlled by aspiration pressure and less by cut rates. The influence of vitreous rheology deserves further investigations.

Advancements of vitreoretinal surgical machines

PURPOSE OF REVIEW

This article reviews current advancements in vitreoretinal surgical machines.

RECENT FINDINGS

The most recent advancement in vitreoretinal surgical machines include 27-gauge vitrectomy probes, new cutter designs, higher cut rate, improved intraocular pressure control, new endoillumination technologies, and combined anterior/posterior segment capabilities.

SUMMARY

With recent advancements in vitreoretinal surgical machines, surgical incisions have become less traumatic and fluidics control has led to a more controlled posterior segment vitrectomy.

Vitreoretinal instruments: vitrectomy cutters, endoillumination and wide-angle viewing systems

There have been many advances in vitreoretinal surgery since Machemer introduced the concept of pars plana vitrectomy, in 1971. Of particular interest are the changes in the vitrectomy cutters, their fluidics interaction, the wide-angle viewing systems and the evolution of endoillumination through the past decade and notably in the last few years. The indications of 27-gauge surgery have expanded, including more complex cases. Cut rates of up to 16,000 cuts per minute are already available. New probe designs and pump technology have allowed duty cycle performances of near 100% and improved flow control. The smaller vitrectomy diameter can be positioned between narrow spaces, allowing membrane dissection and serving as a multifunctional instrument. Enhanced endoillumination safety can be achieved by changing the light source, adding light filters, increasing the working distance and understanding the potential interactions between light and vital dyes commonly used to stain the retina. Wide-angle viewing systems (contact, non-contact or a combination of both) provide a panoramic view of the retina. Non-contact systems are assistant-independent, while contact systems may be associated with better image resolution. This review will cover some current aspects on vitrectomy procedures, mainly assessing vitrectomy cutters, as well as the importance of endoillumination and the use of wide-angle viewing systems.