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

Clinical Performance and Outcomes of a 20 000 Cuts-per-Minute, 25-Gauge, Beveled-Tip Vitrectomy Probe

Purpose: To report the clinical outcomes and instrument performance of a 25-gauge, 20 000 cuts-per-minute (cpm), beveled-tip vitrectomy probe system. Methods: This prospective consecutive case series comprised eyes having primary pars plana vitrectomy (PPV) using a 20 000 cpm vitrectomy probe system (20 000 cpm group). The main outcome measures were the rate of success, operative times, number of steps, 3-month distance-corrected visual acuity (DCVA), ancillary instruments use, and adverse events (AEs). A comparative analysis with the results of a previously published series of eyes that had PPV with a 10 000 cpm, beveled-tip vitrectomy system (10 000 cpm group) was performed. Results: The study included 55 eyes. The surgical objectives were attained in all eyes. The mean logMAR DCVA improved from 0.96 preoperatively to 0.35 postoperatively (at 3 months) (P < .0001). The mean (±SD) total operative time, core vitrectomy time, shave vitrectomy time, and total vitrectomy time was 1964.27 ± 846.92 seconds, 174.87 ± 116.23 seconds, 478.41 ± 387.30 seconds, and 655.60 ± 397.53 seconds, respectively. The mean number of surgical steps was 4.05 ± 1.06 and of ancillary instrument exchanges, 3.23 ± 1.89. The mean postoperative day 1 pain score was 0.16 ± 0.46. Two eyes had elevated intraocular pressure postoperatively and 1 eye had hypotony. There were fewer ancillary instrument exchanges (P < .001) and fewer AEs (P = .044) in the 20 000 cpm group than in the 10 000 cpm group. Conclusions: Both the 20 000 and 10 000 systems are effective and safe for the treatment of various vitreoretinal indications. The potential advantages of the 20 000 system include reduced use of ancillary instrumentation and lower AE rates.

Optimizing Surgical Performance and Safety in Endoresection of Uveal Melanoma

PURPOSE

To present a standardized surgical technique for endoresection of uveal melanoma minimizing the risk of serious adverse events, including fatal gas embolism.

METHODS

Ten uveal melanoma patients underwent endoresection following proton beam radiotherapy for radiotherapy-related vascular complications. Vortex veins located in correspondence of the tumor base had been cauterized at the time of tantalum markers placement. Endoresection was performed following complete 25-G vitrectomy, endolaser, and endodiathermy. The tumor was removed using a subretinal or transretinal approach depending on retinal infiltration. If needed, perfluorodecalin was injected to stabilize the retina. Fluid-silicone oil or perfluorodecalin-silicone oil exchange was performed, avoiding air.

RESULTS

Endoresection was successfully performed in all eyes with no intraoperative complications. Mean follow-up was 10.8 months ± 3.2 months. One patient was enucleated due to neovascular glaucoma. At the last follow-up, the remaining patients had the eye preserved and no signs of local recurrence or neovascular glaucoma.

CONCLUSION

Our standardized surgical technique for uveal melanoma endoresection appeared to be safe, minimizing the risk of serious intraoperative and postoperative adverse events.

Advances in high-speed vitrectomy - surpassing the speed barrier in retinal surgery: a concise review

INTRODUCTION

There has been a significant improvement in the technique and instrumentation for pars plana vitrectomy systems in the past decades. High-speed vitrectomy has emerged as a transformative advancement in retinal surgery. The use of advanced vitreous cutters operating at significantly higher speeds has revolutionized the approach to complex vitreoretinal procedures.

AREAS COVERED

This paper reviews the latest developments in high-speed vitrectomy, focusing on the technological innovations that have driven its evolution, management systems and visualization techniques. The integration of higher cut rates, now exceeding 10,000 cuts per minute, has substantially reduced vitreous traction, minimized iatrogenic retinal tears, and enhanced the safety profile of these surgeries. Clinical outcomes from recent studies demonstrate that high-speed vitrectomy not only reduces operating time but also improves patient recovery with fewer post-operative complications.

EXPERT OPINION

The continuous evolution of vitrectomy technology is setting new standards in retinal surgery, promising greater improvements in patient care. High-speed vitrectomy offers faster, safer, precise surgical outcomes, enhancing surgical success rates. Further research directions may include optimizing cutter design, exploring novel fluidics systems, and developing augmented reality tools to enhance surgeon performance and patient outcomes.

Efficiency and safety comparison between 20,000 and 10,000 cuts per minute vitrectomy using a 27G cutter in rhegmatogenous retinal detachment: a prospective randomized controlled study

PURPOSE

To compare the efficac and safety of a dual-blade 20,000 cuts per minute (cpm) vitrectomy probe with a single-blade 10,000 cpm probe for primary rhegmatogenous retinal detachment (RRD).

STUDY DESIGN

Prospective, randomized controlled clinical trial.

METHODS

Evaluations were conducted preoperatively, intraoperatively, and at three months postoperatively. The main outcome measure focused on the duration of core vitrectomy, with secondary outcomes including peripheral vitreous shaving duration, balanced salt solution (BSS) consumption, anatomical and functional outcomes, as well as the incidence of surgical procedure-related complications.

RESULTS

Overall, 35 cases in the 20,000 cpm group and 37 cases in the 10,000 cpm group completed the trial without significant differences in baseline demographic characteristics. The 20,000 cpm group demonstrated significantly shorter core vitrectomy duration (161.6 ± 10.4 vs. 206.8 ± 10.1 s) (P = 0.003) and peripheral vitreous shaving time (446.3 ± 20.3 vs. 544.2 ± 22.2 s) (P = 0.002) compared to the 10,000 cpm group. BSS consumption was higher in the 20,000 cpm group but without statistical significance (P = 0.231). There were no significant differences in the need for scleral sutures and the incidence of iatrogenic retinal breaks (P = 0.331 and 0.523). At the 3-month follow-up, there were no statistically significant differences in primary success, final anatomical success, or mean visual acuity (P > 0.9, P = 0.326). Rates of complications, including ocular hypertension, epiretinal membrane formation, and endophthalmitis also showed no statistically significant differences (P > 0.6).

CONCLUSION

The utilization of the new-generation 27-gauge system with a 20,000 cpm probe may herald a new paradigm of high-flow, smaller-diameter instrumentation, thereby enhancing the efficiency of the small gauge technique.

Performance, safety and efficiency comparison between a 25G 20,000 and a 10,000 cuts per minute vitrectomy: a prospective randomized control study

BACKGROUND

The aim of this study was to compare the safety and efficacy of 20,000 cuts per minute (cpm) with 10,000 cpm in vitreous cutters.

METHODS

This was a prospective, parallel, single masked randomized control trial comparing the 25 gauge 20,000 cpm HYPERVIT Dual Blade from Alcon Laboratories, Fort Worth, TX, USA and 10,000 cpm ULTRAVIT vitrectomy cutter from Alcon Laboratories, Inc, Fort Worth, TX. Standard T-test by SPSS version 27 was used to compare efficiency and safety between two groups.

RESULTS

In total 72 patients were recruited for the study and among them 71 patients completed the study. This study did not show any significant difference between 20,000 cpm probe and 10,000 cpm probe (p value = 0.347) for the core vitrectomy duration in all included eyes. The mean of core vitrectomy time was 269.28 s in the 25 gauge 20,000 cpm group and 289.44 s in the 25 gauge 10,000 cpm group. However, by comparing the two systems operated on epiretinal membrane eyes, 20,000 cpm probe had a significantly shorter mean core vitrectomy time than 10,000 cpm group (P = 0.03). The majority of all the patients had no intraoperative retinal tear (98.6.8%) and post-operative retinal tear (95.8%). There were no intraoperative iatrogenic breaks, and 3 postoperative retinal tears with rhegmatogenous retinal detachment (RRD) were documented. All the retinal tears belongs to the 20,000 cpm group but no significant difference was found between the two groups in terms of retinal tear and complications.

CONCLUSIONS

25-gauge 20,000 cpm Hypervit dual blade showed a faster trend in vitrectomy time although this was not statistically significant in all included eyes. By comparing vitrectomy time operated on epiretinal membrane eyes, a significant shorter time was found in 25-gauge 20,000 cpm. With more efficient and faster vitrectomy systems, the effect of surgeon factor likely plays a larger role. Our study suggest that the two devices may have a similar efficacy and safety. However, further studies may be needed to compare the core vitrectomy time between them after excluding the surgeon factor influence.

Characterizing the Field of Fluidic Effect Around Vitrectomy Probes Using Particle Image Velocimetry

Purpose

The shape and characteristics of the velocity fields around vitrectomy probes are unknown, resulting in an incomplete understanding of their surgical effects and behavior. The primary aim of this study was to define and measure with high spatial and temporal resolution the field of fluidic effect induced by vitrectomy probes, with assessment of both convective and temporal acceleration in a range of surgically relevant settings with an optimized particle image velocimetry (PIV) methodology.

Methods

This was a laboratory-based investigation using in vitro testing carried out at Newcastle University. Testing was conducted using a DORC EVA Nexus vitrectomy system with dual cutting action vitrectomy probes in three gauge sizes (23G, 25G and 27G). With the use of balanced salt solution (BSS), PIV measurements were conducted for various flow, vacuum, and cut rates. Experiments were conducted in a range of different probe orientations to reconstruct a three-dimensional representation of the flow fields.

Results

Using a variety of improvements in the PIV setup, including choosing an optimal time delay (dt) between the image pairs, the field of fluidic effect was measured with high spatial resolution up to the probe port. Fluid acceleration in the vicinity of the cutter was accurately resolved with values significantly higher than previously reported values. Two clinically relevant zones, high-flow and low-flow, were identified and defined. The high-flow zone (HFZ) had an acceleration of up to 400 m/s2 and reached velocities of up to 1 m/s close to the port for the maximum aspiration setting. The low-flow zone (LFZ) extended approximately 2 to 2.5 mm from the port, or 3.5 to 4 times the diameter of the cutter (during maximum aspiration), with the mean velocity at the edge of the zone reaching 0.01 m/s. The extent of the HFZ was relatively constant with respect to gauge size and increased only marginally with both increased flow and vacuum settings. The LFZ increased in extent with both flow and vacuum. It varied in extent by gauge size with vacuum but was relatively unaltered by gauge size with fixed flow. Cut rate had no clinically relevant effect on the HFZ and LFZ extents and velocity fields.

Conclusions

Using optimized PIV measurements on an experimental in vitro vitrectomy setup, two clearly defined flow zones could be identified around the vitrectomy port. The study defined the shape of the two flow zones in BSS, outlined influencing factors, and correlated fluctuations with gauge, flow, and cut rates. These parameters enhance surgical understanding and provide a benchmark for future design evaluations. Further study using non-Newtonian fluids would be of interest to outline the differences in flow fields.

Translational Relevance

Understanding the flow patterns around the probe and the effect of key surgical parameters on their extent could assist in optimizing vitrectomy and reducing the risk of iatrogenic retinal trauma.

Factors regulating the gripping force and stiffness of 25- and 27-gauge internal limiting membrane forceps

This study aimed to identify the factors affecting the gripping force and stiffness of 25-gauge and 27-gauge (25G and 27G, respectively) internal limiting membrane (ILM) forceps and to compare the effect of these factors on various ILM forceps manufactured by different companies. This study evaluated 25G and 27G ILM forceps with two different types of tip shapes, Eckardt and Maxgrip, manufactured by Alcon (A), DORC (B), VitreQ (C), and Katalyst (D). The gripping force was defined as the force required to move the ILM forceps away from a thin paper by pulling the paper. Shaft stiffness was determined by measuring the shaft displacement under a known force. Multiple regression analysis revealed that the gripping force showed significant correlations with the gauge (P<0.001), type of shaft tip (Eckardt/Maxgrip) (P<0.001), and contact area of the tip (P<0.001). The shaft stiffness showed significant correlations with the gauge (P<0.001), length of the base (P<0.001), thickness of the metal of the shaft (P = 0.05), and lumen area of the shaft (P = 0.01). The gripping force and shaft stiffness differed for each product. Thus, vitreoretinal surgeons must select the appropriate type of ILM forceps based on their characteristics.

25-GAUGE VERSUS 27-GAUGE VITRECTOMY FOR MANAGEMENT OF VITREORETINAL DISEASES: A Large Prospective Randomized Trial

PURPOSE

To compare the safety and performance clinical outcomes of the 27-gauge (G) two-dimensional cutting vitrectomy probe versus a standard 25-G probe for retinal procedures.

METHODS

In this large randomized prospective study, all candidates for epiretinal membrane or macular hole surgery were randomized to the 27-G group or 25-G group. Outcome measures included surgery time, changes in best-corrected distance visual acuity, intraocular pressure, and central macular thickness between baseline and 1-month and 3-month follow-up time points. Moreover, intraoperative and postoperative complications were evaluated as well as the rate of sutureless vitrectomy.

RESULTS

A total of 463 patients were included in this study, 227 patients in the 27-G group and 236 patients in the 25-G group. A similar total surgery time was found between both groups ( P = 0.0911). Similar best-corrected distance visual acuity and central macular thickness changes were observed between baseline and the 1-month and 3-month follow-up visits. No significant differences were reported in intraoperative and postoperative complications rates. The rate of sutureless vitrectomy was 96.5% for the 27-G group and 91.1% for the 25-G group ( P = 0.0170).

CONCLUSION

These results suggest that 27-G vitrectomy probe is similar to 25-G probe in surgery time and complications, while decreasing the need for vitrectomy sutures.

Long-Term Safety and Efficacy of Pars Plana Vitrectomy for Uveitis: Experience of a Tertiary Referral Centre in the United Kingdom

AIM

To evaluate the effectiveness of pars plana vitrectomy (PPV) without macular intervention on uveitis eyes with persistent vitreous inflammation/opacities in terms of visual acuity (VA), intraocular inflammation and macular profile.

METHODS

We carried out a single-center retrospective study of patients with uveitic eyes that underwent PPV without intervention on the macula due to persistent vitreous inflammation/opacities. The primary outcome measures were best-corrected visual acuity (BCVA), intraocular inflammation and macular profile at 3, 12 and 24 months after surgery.

RESULTS

Twenty-seven eyes of twenty-six patients were analyzed. Overall, 77.8% had an improvement of VA (55% by 0.3 LogMAR or more); 62.5% of patients had no intraocular inflammation, and the number of patients on systemic steroids and second-line immunosuppressives was reduced by 26% at 12 months; 87.5% of patients had resolution of macular oedema at 12 months.

CONCLUSION

PPV for persistent vitreous inflammation/opacities is safe and effective, showing beneficial outcomes in terms of improvement of BCVA and the reduction in inflammation.

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.

Dynamic Pressure Measurements During Vitrectomy in a Model of the Eye

Purpose

To accurately evaluate pressure changes during vitrectomy in a rigid model of the vitreous chamber and to test the efficiency of the EVA phacovitrectomy system (Dutch Ophthalmic Research Center) in terms of compensation of intraocular pressure variations.

Methods

We tested 23-, 25-, and 27-gauge double-blade vitreous cutters in both vented global pressure control and automatic infusion compensation (AIC) modes in a vitreous chamber model, mimicking the real surgical procedure. Balanced salt solution and artificial vitreous, similar to the real vitreous body, were used. We tested both standard-flow (SF) and high-flow (HF) infusion systems, varying the infusion pressure between 20 and 40 mm Hg. In each experiment, flow rate was also measured.

Results

Pressure drop was rapidly and efficiently compensated when 23- and 25-gauge cutters were used in AIC mode, with infusion pressures ranging between 30 and 55 mm Hg. The 27-gauge cutter was less efficient in compensating pressure variations. Pressure fluctuations related to the high-frequency motion of the cutter blade were small compared to the overall pressure variations. The use of the HF infusion system resulted in larger flow rates and lower pressure changes compared to the SF infusion system.

Conclusions

Despite the rigid material of the model, the present pressure measurements are in line with previous studies performed on porcine eye. The use of AIC mode compensates intraoperative pressure drops efficiently, with both 23- and 25-gauge cutters. The HF infusion system is more efficient than the SF infusion system.

Translational Relevance

The AIC infusion mode efficiently compensates intraoperative pressure drops, in both 23- and 25-gauge experimental vitrectomy. The HF infusion system resulted in larger flow rate and lower pressure changes.

TWENTY-THREE-GAUGE HYPERSONIC VITRECTOMY: Real-World Surgical Evidence

PURPOSE

To evaluate the safety, effectiveness, and the best parameters setup of hypersonic vitrectomy.

METHODS

A prospective, multicentric, interventional study on 50 eyes that had undergone hypersonic vitrectomy because of various vitreoretinal diseases. We primarily assessed the effectiveness of vitreous removal, intraoperative complications, and surgical setup. Secondarily, we evaluated single-surgery anatomical success and postoperative best-corrected visual acuity.

RESULTS

Intraoperative complications occurred in 5 eyes (10%), whereas technical problems were detected in 23 eyes (46%), resulting in conversion to guillotine vitrectomy in 15 cases. The most common finding related to the technical problems was an inadequate vitreous liquefaction with the formation of vitreous strands and consequent inadequate vitreous outflow, sometimes complicated by vitreous incarceration in the vitrectomy probe. The best settings were considered a stroke of 60 µm and vacuum of 40 mmHg for both core and peripheral vitrectomy. At 3-month follow-up, primary anatomical success was achieved in 49 eyes (98%) and the mean best-corrected visual acuity overall improved.

CONCLUSION

The availability of hypersonic vitrectomy in the current surgical practice opens a new era in vitreoretinal surgery. Despite the potential advantages in fluidics, the performance of hypersonic vitrectomy system needs to be further optimized, mainly for the occurrence of inadequate vitreous liquefaction and vitreous strands formation.

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.

Experimental assessment of the performance of vitreous cutters with fluids with different rheological properties

PURPOSE

To assess the influence of rheological properties of an artificial vitreous (AV) on the performance of double-blade (DB) and single-blade (SB) guillotine vitreous cutters, with 23-, 25-, and 27-gauge (G) probes.

METHODS

We evaluate the aspiration flow rate, using an optical method, based on image processing. Experiments are conducted using ten viscoelastic vitreous phantoms, with different properties that are measured with rheological tests.

RESULTS

Aspiration rate strongly varies with fluid properties. Regardless of cutter geometry and operational conditions, the flow rate significantly decreases as vitreous viscosity and elasticity increase.

CONCLUSIONS

All tested vitreous probes are very sensitive to changes in fluid rheology. SB cutters produce smaller flow rates compared with DB ones of the same caliber; however, they are less sensitive to fluid properties at low aspiration pressures. The use of vitreous substitutes for test performance guarantees comparability between flow rate results achieved with different vitrectomy systems operating in different media. This outcome is further confirmed by the low values of estimated flow rate relative errors.

Impact of different manufacturers and gauge sizes on the performance of backflush needle

The present study aimed to identify the factors regulating aspiration rate (AR) of backflush needles and to compare those factors across various backflush needles from different manufacturers. The 27-gauge (27G), 25-gauge, and 23-gauge backflush needles from four different manufacturers, Alcon, MedOne, VitreQ, and DORC, were used for this experiment. AR was measured at four different aspiration vacuum levels: 100, 200, 400, and 650 mmHg. AR was significantly increased as the aspiration vacuum level increased when both aspirating balanced salt solution (BSS) and ethylene glycol; however, 27G products from VitreQ and MedOne were unable to aspirate ethylene glycol at the low aspiration vacuum level of 100 mmHg. When aspirating BSS at the high aspiration vacuum level of 650 mmHg, a smaller gauge number generally resulted in a significantly higher AR. AR, inner diameter, and cross-sectional area in Alcon products were significantly larger in any gauge, and the shaft length of Alcon products was significantly shorter than those of other manufacturers’ products in any gauge. Cross-sectional area negatively correlated with the degree of shaft deflection (r² = 0.21, p = 0.042). These results imply that AR differs significantly among backflush needles and among companies depending on the shaft cross-sectional area.

Macro- and Microscale Properties of the Vitreous Humor to Inform Substitute Design and Intravitreal Biotransport

Research on the vitreous humor and development of hydrogel vitreous substitutes have gained a rapid increase in interest within the past two decades. However, the properties of the vitreous humor and vitreous substitutes have yet to be consolidated. In this paper, the mechanical properties of the vitreous humor and hydrogel vitreous substitutes were systematically reviewed. The number of publications on the vitreous humor and vitreous substitutes over the years, as well as their respective testing conditions and testing techniques were analyzed. The mechanical properties of the human vitreous were found to be most similar to the vitreous of pigs and rabbits. The storage and loss moduli of the hydrogel vitreous substitutes developed were found to be orders of magnitude higher in comparison to the native human vitreous. However, the reported modulus for human vitreous, which was most commonly tested in vitro, has been hypothesized to be different in vivo. Future studies should focus on testing the mechanical properties of the vitreous in situ or in vivo. In addition to its mechanical properties, the vitreous humor has other biotransport mechanisms and biochemical functions that establish a redox balance and maintain an oxygen gradient inside the vitreous chamber to protect intraocular tissues from oxidative damage. Biomimetic hydrogel vitreous substitutes have the potential to provide ophthalmologists with additional avenues for treating and controlling vitreoretinal diseases while preventing complications after vitrectomy. Due to the proximity and interconnectedness of the vitreous humor to other ocular tissues, particularly the lens and the retina, more interest has been placed on understanding the properties of the vitreous humor in recent years. A better understanding of the properties of the vitreous humor will aid in improving the design of biomimetic vitreous substitutes and enhancing intravitreal biotransport.

Fluid Dynamic Assessment of Hypersonic and Guillotine Vitrectomy Probes in Viscoelastic Vitreous Substitutes

Purpose

To assess the fluidics of 23-gauge (G) large-port (L) and tear drop-port (TD) hypersonic vitrectomy probes (HVPs) compared with guillotine vitrectomy probes (GVPs) of various calibers (23G, 25G, and 27G) and geometries (single and double blades). Also, to identify the working parameters that provide the best balance between acceleration and flow rate, and, for HVPs, to measure temperature variations in the fluid.

Methods

We used particle image velocimetry to measure flow fields in balanced salt solution and viscoelastic artificial vitreous. We analyzed acceleration, kinetic energy, and volumetric flux. The parameters considered were vacuum pressure, ultrasound stroke, and cut rate. Temperature measurements were taken using an infrared thermal camera.

Results

The flow rate was significantly higher for HVPs than GVPs. With both probes, flow rate and acceleration increased with vacuum pressure. Flow rate depended weakly on the ultrasound stroke or cut rate. In HVPs, the acceleration peaked at a stroke of 30 µm, whereas in GVPs it peaked at a cutting rate of 4000 to 5000 cuts per minute (cpm). The HPV/TD combination generated higher flow rates and lower accelerations than did HPV/L. The increase in temperature was small.

Conclusions

Under the present experimental setup and medium, HVPs offered better fluidics compared with GVPs in terms of flow and acceleration; however, the flow structure for HVPs is more complicated and unsteady. The HPV/TD combination produced larger flows than did the HPV/L combination and slightly smaller accelerations. HPVs generated a small temperature increase.

Translational Relevance

In the tested artificial vitreous, HVPs were found to be more efficient in terms of generating lower acceleration for a given flow rate. The slight increase in temperature observed with HVPs is unlikely to be clinically significant.