Ultrasonic-generated fluid velocity with Sovereign WhiteStar micropulse and continuous phacoemulsification

Simulation of fluid dynamics and turbulence during phacoemulsification using the new propeller turbo tip

PURPOSE

To investigate the fluid dynamics and turbulence in the anterior chamber during phacoemulsification with a new propeller turbo tip using computational fluid dynamics methods.

METHODS

A theoretical study, three-dimensional model with the corresponding mathematical equations for the propeller turbo phaco tip, anterior chamber and lens capsular bag was developed. A simulation was performed for the new propeller turbo tip with various parameter settings (vacuum, irrigation bottle height and phaco power). Fluid dynamics and turbulence in the anterior chamber, lens capsular bag and phaco tip were evaluated. The linear relationship between the different setting parameters and a stable anterior chamber pressure was assessed.

RESULTS

The fluid dynamic turbulence was mainly symmetrically distributed in the anterior chamber. Propeller turbo phaco tip vibration caused increased fluid velocity and asymmetrical fluid turbulence in the metal lumen but had little influence on dynamic intraocular pressure. Reasonable phaco machine parameter settings can maintain a stable intraocular pressure during phacoemulsification.

CONCLUSIONS

Evaluation of phacoemulsification fluid dynamics using computational simulation methods could provide detailed information about the influence of the propeller on dynamic intraocular pressure during phacoemulsification, which is useful for a better understanding of this procedure.

Characterization of Ultrasound Surgical Devices

This article is a review of the techniques for characterizing ultrasound surgical devices, as a guide to those undertaking a program of measurement, and as a basis for further standardization of those methods. The review covers both acoustic and nonacoustic measurements, with an emphasis on proper techniques, devices, and analyses according to the IEC Standard 61847. Low-frequency hydrophone measurements are presented, which are centered on simple acoustic theory. Inertial cavitation measurements are described based on detailed analyses of shock wave propagation. Cutting force tests are also presented as a basis for determining relative performance characteristics and determining mechanisms of action. Example data from each type of test are given. Comparison between acoustic output measurements, in vitro data, and clinical outcomes help establish that inertial cavitation is the predominant mechanism of soft tissue erosion and emulsification. The test results also demonstrate approaches to improving efficiency while minimizing undesired effects. Finally, recommendations are made for updates to the 61847 Standard and for other device labeling that would improve patient safety.

Experimental study of occlusion break surge volume in 3 different phacoemulsification systems

PURPOSE

To evaluate surge volume after occlusion breaks in 3 different phacoemulsification systems.

SETTING

Alcon Research LLC, Lake Forest, California.

DESIGN

Experimental study.

METHODS

A mechanical spring eye model was used to test the Centurion with Active Sentry, WhiteStar Signature Pro, and Stellaris PC. Raw oscilloscope data were converted to volumetric and pressure measurements. Fitted average surge traces were generated for each test condition and used to develop an interpolation algorithm to predict transient occlusion break surge events. Two-dimensional heat maps were generated.

RESULTS

During occlusion break surge, the Centurion with Active Sentry had smaller aqueous volume losses than the WhiteStar or Stellaris PC. Maximum surge volumes within the mechanical spring eye model displacement limit were 74.7 μL, 157.5 μL, and 151.7 μL using Centurion with Active Sentry, WhiteStar, and Stellaris PC, respectively. In the aphakic state, heat maps showed that Centurion with Active Sentry had less than 20% aqueous volume loss across all vacuum limits and target intraocular pressure; WhiteStar and Stellaris PC systems had up to 35% and 50% aqueous volume losses, respectively, at the higher vacuum limits. In the phakic state, Centurion with Active Sentry had up to 30% aqueous volume loss and WhiteStar and Stellaris PC systems had up to 50% aqueous volume losses. In addition, predicted transient traces demonstrated that Centurion with Active Sentry had the lowest percentage simulated aqueous volume loss compared with WhiteStar or Stellaris PC.

CONCLUSIONS

Centurion with Active Sentry had lower aqueous volume losses after occlusion break than WhiteStar and Stellaris PC systems at all surgical settings.

Comparison of semicircular and bent tips regarding regional differences in oscillation amplitude under various torsional power settings

PURPOSE

To analyze the difference between the behavior of semicircular (balanced) and bent (mini) tips at 20 incremental torsional power settings.

SETTING

Tsukazaki Hospital, Himeji, Japan.

DESIGN

Experimental study.

METHODS

Using an ultra-high-speed video camera HPV-X2, the 2 tips during torsional oscillation were recorded, comparing tip behavior at power settings from 5% to 100% by tracking points 1 to 5 (tip end and at 1325, 2650, 3975, and 5035 μm from the tip end).

RESULTS

Both tips increased their amplitude widths, drawing an S-curve at all points as the torsional power setting was increased, reaching their upper limits from 70% to 90% torsional power. At all 20 power settings, both tips showed significantly different amplitudes (all P < .01), and the difference of the amplitude increased as the power setting increased. Although, at points 1 and 3, the balanced tip amplitude was nearly 1.5 times larger than the mini tip amplitude, the amplitude difference was 10 μm or less at points 2 and 4. At point 5, the mini tip amplitude was at least 3 times more than the balanced tip amplitude.

CONCLUSIONS

The amplitude does not increase proportionally and varies markedly with the tip shape on reaching the upper limit, suggesting that a higher power setting might not contribute greatly to nuclear fragmentation. The balanced tip might cause greater damage to surrounding tissues if it is inserted at approximately 3 mm from the wound site. To obtain maximum shaft stability using the balanced tip, it is important to insert at least 5 mm.

Determining optimal ultrasound percent on time with long-pulse torsional phacoemulsification

OBJECTIVE

To evaluate the optimum percent on time for the most efficient lens fragment removal using long-pulse torsional ultrasound (US).

DESIGN

In vitro laboratory study.

METHODS

Porcine lens nuclei were incubated in formalin for 2 hours and then cut into 2 mm cubes. Phacoemulsification was performed using the Centurion^® Vision System and Infiniti OZil handpiece with the balanced tip. Vacuum was set at 500 mm Hg, aspiration rate at 50 mL/min, and intraocular pressure (IOP) at 50 mm Hg. Pulse rate was 26 pulses/second. Studied parameters were percent power: 60%, 80%, and 100%, and percent on times: 50%, 60%, 70%, and 80%. Efficiency was the total time for a cube to be emulsified. Chatter was the number of times the lens fragment bounced off the tip.

RESULTS

There was no significant difference in efficiency between 50%, 60%, and 70 % on-time settings (p = 0.17 and 0.08, respectively); however, there was significant increase in efficiency when the on time was increased from 70% to 80% (p = 0.03). Increasing power from 60% to 100% showed a statistically significant efficiency increase (p = 0.001). There was no significant change in chatter with increasing on time; however, there was a statistically significant increase in chatter with every power level increase.

CONCLUSION

Increasing on-time percent does not improve efficiency under torsional long-pulse US. There is no significant change in chatter with increasing on-time percent. Increasing power increases efficiency despite chatter increase. Long-pulse US does not appear to influence torsional action in a clinically meaningful way.

Optimum on-time duty cycle for a transversal ultrasound machine

PURPOSE

To evaluate the optimum on-time setting for the most efficient removal of lens fragments using micropulse ultrasound (US) and Ellips FX transversal US in the Whitestar Signature Pro phacoemulsification machine.

SETTING

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

Porcine lens nuclei were soaked in formalin for 2 hours and cut into 2.0 mm cubes. The US machine was used with a bent 0.9 mm phaco tip and a 30-degree bevel. The off time was set to 6 milliseconds (ms) and the on time varied from 4 to 10 ms in 1 ms increments. Efficiency (time for fragment removal) and chatter (number of times the fragment bounced from the tip) were measured.

RESULTS

A linear incremental increase in efficiency was observed between 4 ms and 6 ms. The most statistically significant efficiency was achieved with an on time of 6 ms. On times shorter than 6 ms were significantly less efficient (P = .05). Greater on times (7 to 10 ms) did not result in a significant difference in efficiency (P = .72), but did appear to have more chatter events when comparing on-time settings of 7 to 10 ms with 4 to 6 ms (P = .02).

CONCLUSIONS

With micropulse transversal US, 6 ms of on time was as efficient as longer on times. To maximize phacoemulsification efficiency and minimize chatter events, an on time of 6 ms is recommended.

Effects of Cataract Surgery on Endothelium in Transplanted Corneal Grafts: Comparison of Extracapsular Cataract Extraction and Phacoemulsification for Complicated Cataract after Penetrating Keratoplasty

Background:

The endothelium should be carefully evaluated when choosing a surgical technique for cataract removal. Therefore, we aimed to study the effects of different cataract surgery techniques on endothelial cell loss in transplanted corneal grafts.

Methods:

A total of 54 patients who received complicated cataract surgery in post-penetrating keratoplasty (PKP) eyes at the Shandong Eye Institute between February 2001 and June 2014 were included, and clinical records were reviewed. Baseline demographic details, clinical characteristics, endothelial cell density (ECD), and best-corrected visual acuity (BCVA) were recorded. Wilcoxon rank-sum test and Wilcoxon signed-rank test were used to test the equality of medians. A regression model was constructed to compare the reduced rate of ECD.

Results:

Of the 54 eyes included in this study, extracapsular cataract extraction (ECCE) was performed in 34 eyes of 33 patients (ECCE group) whereas phacoemulsification was performed in 20 eyes of 20 patients (phacoemulsification group). There was no significant difference in the median age (P = 0.081) or preoperative ECD (P = 0.585) between the two groups. At 6 months after cataract surgery, ECD in ECCE group was significantly higher than that in phacoemulsification group (P = 0.043). In addition, the endothelial cell loss rate in ECCE group was significantly lower than that in phacoemulsification group at 2 months (P = 0.018), 4 months (P < 0.001), and 6 months (P < 0.001) after cataract surgery. Endothelial cell loss rate after cataract surgery increased over the 6-month study duration in both ECCE group (P < 0.001) and phacoemulsification group (P < 0.001), but phacoemulsification resulted in a greater reduction in ECD than that of ECCE in transplanted corneal grafts (P < 0.001). There was no significant difference in postoperative BCVA between the two groups (P = 0.065).

Conclusion:

ECCE is more suitable than phacoemulsification in cataract surgery in complicated cataract after PKP.

Difference in torsional phacoemulsification oscillation between a balanced tip and a mini tip using an ultra-high-speed video camera

PURPOSE

To evaluate the behavior of 2 types of torsional phaco tips, the newly developed balanced tip and the current mini tip, using an ultra-high-speed video camera.

SETTING

Tsukazaki Hospital, Himeji, Japan.

DESIGN

Experimental study.

METHODS

The HPV-X2 camera was used to capture how the 2 types of tips with torsional oscillation behave in artificial aqueous humor. The following 5 points on the tips were tracked to compare their behaviors: the tip end (point 1) and distances from the tip end of 1325 μm (point 2), 2650 μm (point 3), 3975 μm (point 4), and 5035 μm (point 5).

RESULTS

The mean amplitude time for the balanced tip and the mini tip was 16.29 μsec ± 1.11 (SD) and 15.86 ± 1.21 μsec, respectively (P = .54). The mean amplitude ranges for 2 tips were, respectively, 189.69 ± 4.12 μm and 132.89 ± 7.90 μm (P = .002) at point 1, 20.54 ± 2.12 μm and 23.23 ± 1.68 μm (P = .041) at point 2, 42.54 ± 1.36 μm and 31.00 ± 1.20 μm (P = .002) at point 3, 53.01 ± 8.13 μm and 47.40 ± 10.46 μm (P = .443) at point 4, and 15.15 ± 2.05 μm and 46.40 ± 9.12 μm (P = .002) at point 5.

CONCLUSION

The results suggest that the balanced tip can greatly increase the amplitude range at the tip end and reduce shaft movement compared with the mini tip, resulting in less damage to the wound and surrounding tissue.

FINANCIAL DISCLOSURES

Proprietary or commercial disclosures are listed after the references.

Effect of pulsing ultrasound on phacoemulsification efficiency

PURPOSE

To evaluate pulse type technology used to remove lens fragments during phacoemulsification.

SETTING

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

Lens nuclei soaked in 10 mL of 10% neutral buffered formalin for 2 hours were placed in 10 mL of balanced salt solution. Lenses were cut into 2 mm × 2 mm cubes; no more than 36 hours later, cubes were randomly selected for testing. Two aspiration and 2 vacuum settings were assessed at moderate- and high-flow and vacuum (30 mL/min and 300 mm/Hg, low-flow vacuum; 50 mL/min and 500 mm/Hg, high-flow vacuum), with continuous 50 milliseconds on and off (long pulse) and 6 milliseconds on and off (micropulse) ultrasound.

RESULTS

There was a significant difference in efficiency favoring micropulse compared with combined long pulse and continuous pulse in high-flow vacuum at 80% power (P = .018) and between combined long pulse and continuous pulse versus micropulse in high-flow vacuum at 20% power (P = .019). Low-flow vacuum micropulse was more efficient than continuous (19.7%) (P < .0001) and long pulse (22.7%) (P < .0001). Continuous and long pulses were not significantly different from one other. There was a significant difference in chatter rates between high-flow vacuum and low-flow vacuum when all results were compared (P < .0001), with no additional significant differences found.

CONCLUSION

Micropulse technology was better than continuous and long pulse at moderate but not high-flow and vacuum settings. At the higher setting, chatter was observed less often, with all modalities more efficient than the lower setting.

Determining optimal ultrasound off time with micropulse longitudinal phacoemulsification

PURPOSE

To evaluate the optimum off time for the most efficient removal of lens fragments using micropulse ultrasound (US).

SETTING

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

Porcine lens nuclei were soaked in formalin for 2 hours and then cut into 2.0 mm cubes using the Signature US machine with a bent 0.9 mm phaco tip with a 30-degree bevel. The on time was 7 milliseconds (ms), and the off time was varied from 2 to 20 ms in 2 ms steps. Phacoemulsification efficiency (time for fragment removal) and chatter (number of times the fragment bounced from the tip) were measured.

RESULTS

A nonsignificant linear increase in efficiency was observed with 2 to 6 ms of off time (R(2) = .87, P = .24). A significant linear decrease in efficiency was observed with 6 to 20 ms (R(2) = .74, P = .006).

CONCLUSIONS

With micropulse longitudinal US, 6 to 7 ms of off time was as efficient as shorter off times; longer off times (8 to 20 ms) showed decreased efficiency. Chatter was minimal and statistically similar throughout. To maximize phacoemulsification US efficiency, an off-time setting of 6 ms is recommended.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Optimum on-time duty cycle for micropulse technology

PURPOSE

To evaluate the optimum on time for the most efficient removal of lens fragments using micropulsed ultrasound (US).

SETTING

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA.

DESIGN

Experimental study.

METHODS

Twenty porcine lens nuclei were soaked in formalin for 2 hours and then divided into 2.0 mm cubes. Using an US machine with a 0.9 mm bent and a 30-degree bevel tip, the on time was varied every millisecond (ms) from 2 ms to 10 ms with the off time kept constant at 10 ms. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined.

RESULTS

The most efficient phacoemulsification was achieved with an on time of 6 ms. On times shorter than 6 ms were significantly less efficient (R2=.82, P=.04). Greater on times did not result in a significant difference in efficiency (R2=.03, P=.78) but did appear to have more chatter events when comparing 9 to 10 ms with 2 to 8 ms (P<.0001).

CONCLUSIONS

With micropulsed longitudinal US, a 6 ms on time was equally as efficient as longer on times, while shorter on times (2 to 5 ms) had decreased efficiency. At 9 ms and 10 ms on time, significantly more chatter was noted. Therefore, to maximize phacoemulsification, an on-time setting of 6 ms is recommended.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Visualization of irrigation fluid flow and calculation of its velocity distribution in the anterior chamber by particle image velocimetry

PURPOSE

To visualize irrigation fluid flow and calculate its velocity distribution in the anterior chamber during phacoemulsification by particle image velocimetry.

METHODS

Porcine eyes were fixed in a glass chamber filled with balanced salt solution. An ultrasound handpiece was fixed to the glass chamber, and its tip was inserted into the anterior chamber through a corneal incision. Irrigation fluid was mixed with fluorescein-labeled liposomes as tracer particles. During phacoemulsification without ultrasound, a sheet-like Nd-YAG pulsed laser beam was emitted and moved from the iris plane to the top of the cornea continuously. Images of illuminated liposomes in the anterior chamber were captured at short intervals with a CCD camera, and the velocity distribution of irrigation fluid flow was calculated by particle image velocimetry.

RESULTS

By particle image velocimetry, the flow velocity distribution could be calculated in any plane of the anterior chamber. Dynamic flow of the irrigation fluid, ejected from the tip of the ultrasound handpiece and returned to an aspiration port, was visualized clearly in the anterior chamber. The maximum flow velocity in the anterior chamber was 342 ± 131 mm/s.

CONCLUSIONS

Particle image velocimetry enabled the visualization of irrigation fluid flow and quantification of its velocity distribution in different planes of the anterior chamber during cataract surgery. These data are essential for evaluating the safety and efficacy of new surgical settings and devices during phacoemulsification.

Innovations in phacoemulsification technology

PURPOSE OF REVIEW

A working knowledge of the principles guiding recent technologic upgrades in phacoemulsification units will help the surgeon to maximize clinical benefits from the latest machines.

RECENT FINDINGS

Reduced thermal energy combined with more efficient emulsification resulting from microfractionation of ultrasound energy, and improved chamber stability from automatic fluidic adjustments are achievable with the recent technological advances.

SUMMARY

Improved safety and efficiency can be achieved with the most current advances in phacoemulsification technology.