Objective comparison of 4 nonlongitudinal ultrasound modalities regarding efficiency and chatter

Efficiency of a polymer-coated phacoemulsification tip in cataract surgery

PURPOSE

To determine whether there is a difference in efficiency during phacoemulsification when using the hybrid polymer tip compared with the metal balanced tip, as measured by cumulative dissipated energy (CDE) and total procedure time.

SETTING

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

DESIGN

Experimental study.

METHODS

Phacoemulsification was performed with the Centurion Vision System and Infiniti OZil handpiece, with a 30-degree bevel metal balanced tip and hybrid polymer tip. The vacuum was set at 500 mm Hg and the aspiration flow rate at 50 mL/min. Power was changed for torsional and longitudinal ultrasound (US) at 20%, 40%, 60%, 80%, and 100%. Hardened porcine lenses were cut into 200 two mm cubes, 10 for each specified tip/power setting. They were placed into an artificial anterior chamber filled with a balanced salt solution, and phacoemulsification was performed. A second observer randomly assigned the US type and power. The same observer timed trials with a stopwatch, and CDE was recorded.

RESULTS

There were no significant differences in time or CDE for any power levels or US modes when comparing the 2 tips.

CONCLUSIONS

No significant difference in efficiency was observed when comparing the metal balanced tip with the hybrid polymer tip. Given the known improved safety profile and the overall equivalent efficiency of the hybrid tip, it could improve the performance of beginning and advanced surgeons in the future. Future study is needed to evaluate other setting combinations and to evaluate the hybrid tip in clinical settings.

Effect of Modified Peristaltic Phacoemulsification Device on Efficiency and Post-Occlusion Pressure Surge

Purpose

To evaluate efficiency of grooving, nuclear fragment removal, and changes in pressure control in the Oertli Faros using traditional peristaltic and Speed and Precision (SPEEP) features. The SPEEP mode uses novel peristaltic technology permitting independent control of flow and vacuum.

Methods

A porcine lens model was used with an enclosed chamber simulating the anterior segment. Grooving efficiency is evaluated with flow rates of 10, 30, and 50 mL/min using whole lenses. Lens cubes were emulsified at 20, 40, 60, 80, and 100% power with both SPEEP and non-SPEEP modes. Surge was evaluated with pressure gauges placed on the irrigation tubing and aspiration tubing. Pressure readings were recorded per the following: fluid and vacuum were initiated for 15 seconds, vacuum tubing was occluded for 5 seconds, tubing patency was then re-introduced for 15 seconds. Differences between sensors were recorded.

Results

No significant increase in efficiency was seen with increasing flow rate from 30 to 50 mL/min using SPEEP. No significant differences were shown in lens fragment removal in SPEEP and non-SPEEP modes at any power tested. Pressure difference measurements were not significantly different with SPEEP and non-SPEEP modes.

Conclusion

We showed that lower flow rates show comparable efficiency of grooving when using the SPEEP mode. The SPEEP function did not show increased efficiency in nuclear fragment removal when compared to traditional mode. Surge control was also comparable with both SPEEP and non-SPEEP modes. We suggest that the SPEEP function included in the Oertli Faros may have some advantages.

Comparison of Phacoemulsification Grooving Efficiency in Longitudinal vs Transversal Handpieces

Purpose

To determine the difference, if any, in grooving efficiency at various settings on the Whitestar Signature Pro phacoemulsification (phaco) system.

Methods

Cataractous lenses were simulated by exposing porcine lenses to formalin for 2 hours. A total of 120 lenses were analyzed at various power settings on both longitudinal and transversal handpieces. Twenty trials each were performed with power set to 25%, 50%, and 75% on both handpieces. A Whitestar Phaco Handpiece System was used to provide longitudinal power, and a Whitestar Signature Ellipsis Handpiece provided transversal power. Lenses were placed within a plastic chamber and grooved by an investigator blinded to settings. A second investigator recorded times and adjusted settings. The Whitestar Signature Pro phaco system was used for grooving.

Results

There was no significant difference in grooving times between the longitudinal and transverse handpieces at any power setting (P > 0.05). There was a significant decrease in grooving times when comparing the 25% power setting with the 75% power setting for the transversal handpiece (P=0.021).

Conclusion

Both longitudinal and transversal handpieces on the Whitestar Signature Pro phaco system produce similar results to one another at each power setting. There is a general trend toward shorter grooving times, reflecting greater efficiency, at higher power settings. Grooving efficiency on the transversal handpiece may be more affected by changes in the power settings as compared with the longitudinal settings.

Measurement of Phacoemulsification Vacuum Pressure in the Oertli CataRhex3

Purpose

To determine the actual vacuum pressure generated by the Oertli CataRhex 3^® (Oertli), using an external measuring system.

Methods

The effective vacuum pressure created by the Oertli was measured with a pressure device that was continuous with the vacuum tubing system while closed to the external environment. Measurements were taken with the machine set to 300 and 500 mmHg at flow rates of 20, 35, and 50 mL/min and at bottle heights of 60, 80, and 100 cm. Pressures were recorded after the foot pedal was depressed to vacuum setting (second position), and the pressure was allowed to stabilize. Subsequently, it was compared to the pressure value displayed by the machine.

Results

Externally measured vacuum pressure was on average 13.02% greater (39.05 mmHg) than displayed vacuum pressure at 300 mmHg (P < 0.005) and 8.60% greater (42.98 mmHg) than displayed vacuum at 500 mmHg (P < 0.005). The average difference between displayed and measured pressure increased with increasing bottle heights.

Conclusion

On average, the vacuum pressure generated in the Oertli was found to be significantly higher than the machine’s reading when the machine was set at 300 mmHg and 500 mmHg. Adjusting vacuum had variable effects on the measured versus displayed pressure readings.

Optimization of Phacoemulsification Tip Gauge on the Oertli CataRhex3 in an in vitro Setting

Purpose

To evaluate the effect of each of the tip sizes available for the Oertli CataRhex3^® phacoemulsification machine on efficiency.

Methods

Porcine lenses were fixed in formalin for 2 hours, then cut into 3.0 mm cubes. We studied three Oertli tips, all of which had a 30-degree bevel: easyTip 2.2 mm (20G), easyTip 2.8 mm (19G), and CO-MICS (21G). For the 19G and 20G tips, vacuum was set at 600 mmHg, irrigation rate at 50 mL/min, continuous power 70%, and bottle height 85 cm. For the 21G tip, vacuum was set at 450 mmHg; irrigation and power settings were identical to those used for the easyTip tips. We measured time to removal and chatter events to determine efficiency.

Results

Results from 20 trials for each tip showed that the larger the gauge size, the more quickly lens fragments were removed. Chatter events demonstrated an increasing trend with smaller tip gauge. The 19G tip used an average time to fragment removal of 2.8 seconds; the 20G, 3.2 seconds; and the 21G, 4.6 seconds. Increasing tip diameter from 21G to 20G decreased emulsification time by 33% (P = 0.02). Increasing the diameter from 21G to 19G further decreased time to emulsification by 42% (P = 0.003). The 21G tip had a mean 1.4 events/cube; 20G, 0.35 events; and 19G, 0.1 events. Differences in mean chatter events for each tip were each statistically significant.

Conclusion

These data suggest that when evaluated by chatter events and emulsification time, the 2.8 mm (19G) easyTip proves to have greatest efficiency.

Optimizing Tip Diameter in Phacoemulsification of Varying Lens Sizes: An in vitro Study

Purpose

We assessed the effect of two lens cube sizes, three tip sizes, and two ultrasound (US) approaches on phacoemulsification efficiency and chatter.

Methods

After porcine lens nuclei were soaked in formalin, we divided them into cubes measuring 2.0 mm or 3.0 mm. We collected efficiency and chatter data for 30-degree bent 19 G, 20 G, and 21 G tips with a continuous torsional US system; and for straight 19 G, 20 G, and 21 G tips with a micropulse longitudinal US system.

Results

The average time needed for removal was always higher for the 3.0 mm lens cube than for the 2.0 mm lens cube. Statistically significant differences were observed between the 19 G and 21 G tips with micropulse longitudinal US using a 2.0 mm cube and a 3.0 mm cube, and with continuous transversal US using a 2.0 mm lens cube and a 3.0 mm cube. We did not observe significant differences between 19 G and 20 G tips with either cube size in either US system. However, we noted identical trends for both cube sizes with both US approaches; 19 G tips performed better than 20 G and 21 G tips.

Conclusion

Regardless of the lens size, 19 G needles were the most efficient, and had both the fewest outliers and the smallest standard deviations.

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.

Effects on phacoemulsification efficiency and chatter at variable longitudinal ultrasound settings when combined with constant torsional energy

PURPOSE

To evaluate longitudinal power settings for optimally efficient lens fragment removal, using the Centurion machine.

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine lens nuclei were cut into 2.0 mm cubes. Experiments were conducted at 100% torsional power; vacuum set at 500 mm Hg, aspiration 50 mL/min, and intraocular pressure 110 mm Hg. A 20-degree tip with a 30-degree bevel was used. Longitudinal power was tested between 20% and 100%. Efficiency (time for fragment removal) and chatter (the number of times the fragment bounced from the tip) were measured.

RESULTS

A linear increase in efficiency was observed from 20% to 100% longitudinal power (R = 0.9281, slope = -0.0271). An efficiency slope change occurred at 60% power, with the largest incremental change in efficiency between 20% and 60% (R = 0.9756, slope = -0.0394) and a lesser change between 60% and 100% (R = 0.9827, slope = -0.0121). Chatter analysis showed minimal events at 20% to 60%, but a significant increase at >80% (P = .005). This increase appeared to be incremental (R = 0.8929).

CONCLUSIONS

Increasing longitudinal power, with all other settings constant, increased efficiency. Greatest efficiency gains were observed between 20% and 60%. At 80% and 100%, chatter events increased significantly. With a goal of recommending optimally efficient settings while minimizing excess energy and chatter, adding 60% of longitudinal power to 100% torsional power was shown to be the best setting to increase efficiency and avoid repulsion in these vacuum and aspiration settings.

Assessment of Learning Curve in Phacoemulsification Surgery Among the Eastern Province Ophthalmology Program Residents

Purpose

To assess residents’ performance of phacoemulsification surgery and determine which steps of the procedure are most difficult to learn, and to measure rate of intraoperative complications.

Design

This was a prospective observational study.

Methods

Phacoemulsification surgery was divided into steps and each step was given a proficiency grade by the attending consultant. All intraoperative complications were recorded and analyzed.

Results

200 cases performed by the Eastern Province ophthalmology program residents were evaluated. The most commonly encountered difficulty factors were hard nucleus (20.7%), small pupil (12.6%), and white cataract (10.3%). Capsulorhexis, nucleus disassembly and removal, and cortex removal were the most difficult steps to learn. General complication rate was 17.5%, and posterior capsular rupture was the most common complication (40%). Proficiency more than 90% of the time in each step was noted in residents with prior experience of more than 40 cases, except for nucleus disassembly.

Conclusion

The study showed that nucleus disassembly remained the major obstacle in the residents’ exponential learning curve of phacoemulsification surgery. Majority of complications occurred at level of capsulorhexis and cortical removal steps.

Optimum on-time and off-time combinations for micropulse phacoemulsification in venturi vacuum mode

PURPOSE

To measure the time to fragment removal and number of chatter events using various combinations of micropulse on times and off times (measured in milliseconds) of longitudinal ultrasound (US) using a venturi-based phacoemulsification system.

SETTING

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

DESIGN

Experimental study.

METHODS

Pig lenses were hardened with formalin and cut into 2.0 mm cubes. The time to fragment removal (efficiency) and frequency of fragments bouncing off the tip (chatter) were measured with the venturi-based system. Micropulse longitudinal US was tested. Parameters were combinations of 5, 6, and 7 milliseconds on, with 5, 6, and 7 milliseconds off. Twenty runs each of 9 combinations were completed.

RESULTS

There was a statistically significant difference between on/off duty cycle combinations. The 6 on/7 off group had higher efficiency than the 5 on/6 off and 7 on/7 off groups. Six on/5 off was more efficient than 5 on/6 off. When data were pooled and on times alone were used, 6 milliseconds on time was more efficient than 5 or 7 milliseconds. No efficiency differences in off times were found. No significant chatter differences were observed.

CONCLUSIONS

Using micropulse longitudinal US in venturi vacuum mode, 6 milliseconds on was the most efficient on time. Five, 6, and 7 milliseconds off times had similar efficiency. These data suggest that the most efficient setting with lowest US energy use is 6 milliseconds on and 7 milliseconds off.

Impact of torsional micropulse on phacoemulsification efficiency and chatter

OBJECTIVE

Evaluate the effect of increasing ultrasound (US) power on chatter events and efficiency under both continuous and micropulse torsional US to reduce total cataract extraction times.

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. Both US modalities were studied at 60%, 80%, and 100% power. Micropulse rate was 83 pulses per second with 50% on time. Each combination comprised 20 runs. Efficiency was considered as 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 significant decrease in efficiency when power was increased from 60% to 100% (1.33-1.97 s; p < 0.001) under micropulse US and significant increase in chatter when power was further increased to 100% from 60% (0.15-0.94 s; p < 0.001). There was no significant efficiency change with increased power under continuous US. Comparing the phacoemulsification efficiency between continuous and micropulse US, we found no significant difference at 60% and 80% power; at 100% power, continuous was significantly more efficient than micropulse (1.48 and 1.97 s, respectively; p = 0.001).

CONCLUSIONS

Increasing power above 60% decreased efficiency under torsional micropulse US. We believe that this was due to the chatter increase observed with increasing US power. Torsional continuous US was significantly more efficient than micropulse US at 100% power.

Optimization of the Oertli CataRhex 3® phacoemulsification machine

Purpose

The aim of this study was to determine optimal bottle height, vacuum, aspiration rate, and power settings of the Oertli CataRhex 3^® phacoemulsification machine.

Methods

Porcine lens nuclei were hardened with formalin and cut into 2.0 mm cubes. Lens cubes were emulsified using the easyTip^® 2.2 mm at 30°. Fragment removal time (efficiency) and fragment bounces off the tip (chatter) were measured. Settings tested included bottle height of 60, 80, 100 and 120 cm; aspiration rate of 40, 45, and 50 mL/min; vacuum of 400, 500, and 600 mmHg; and power of 50, 60, 70, 80, 90, and 100%.

Results

Efficiency and chatter increased in a linear fashion with increasing vacuum to 600 mmHg (P=0.017, P=0.046, respectively). The most efficient aspiration rate was 50 mL/min, although this finding lacked statistical significance (P=0.66). Increasing power increased efficiency up to 80% without increasing chatter (P=0.042, P=0.71, respectively). Compared to all other power settings, chatter was increased at 100% (P=0.014).

Conclusion

The most efficient machine settings were vacuum at 600 mmHg, aspiration rate at 50 mL/min, and power at 80%.

Phacoemulsification in review: Optimization of cataract removal in an in vitro setting

Phacoemulsification, initially used in the late 1960s, continues to be the standard of care for cataract removal. An animal model was developed so that, in a controlled research setting, all the various machines, handpieces, tips, and settings could be investigated. As a general rule, the higher power, vacuum, and aspiration settings lead to optimally efficient phacoemulsification. In addition, both new phacoemulsification platforms and newly developed devices have been shown to improve efficiency. As a result, we recommend that the integration of these recent developments should be considered in future investigations.

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.

The effect of increasing power when grooving using phacoemulsification

PURPOSE

To determine optimal power settings on the Centurion Vision System during the grooving step in cataract surgery.

METHODS

Intact porcine lenses hardened by formalin and placed in a chamber designed to simulate the anterior chamber of the eye were used to test longitudinal power at 40%, 70%, and 100% and torsional power at 0%. Flow rate was set at 40 mL/min. Vacuum was set at 400 mmHg, intraocular pressure was set at 50 mmHg, and a balanced phacoemulsification tip with a 20 degree tip and a 30 degree bevel was used. Efficiency (time to groove the lens in half) was determined.

RESULTS

Increasing longitudinal power from 40% to 70% increased efficiency by 28% (P<0.05), and by 32% (P<0.05) when increasing longitudinal power from 40% to 100%. There was no statistically significant increase in efficiency from 70% to 100%.

CONCLUSION

For the tested variables, a longitudinal power of 70% was determined to be most efficient during the grooving step of cataract surgery for equivalent 3-4+ nuclei. Further increases in power demonstrated no statistically significant improvement in efficiency.

High vacuum and aspiration on phacoemulsification efficiency and chatter for Centurion

OBJECTIVE

To compare relative efficiency and chatter of high aspiration and vacuum settings.

DESIGN

In vitro laboratory study.

METHODS

The John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Porcine nuclei were fixed in formalin and cut into 2.0 mm cubes. Lens cubes were phacoemulsified with Balanced tips at 50 and 60 mL/min aspiration with 500, 600, and 700 mm Hg vacuum with monitored forced infusion. Experiments were conducted at constant torsional power, longitudinal power, and intraocular pressure.

RESULTS

No significant change was observed in average chatter across each tested setting. Increasing aspiration rate did not increase efficiency. Increasing vacuum up to 600 mm Hg from 500 mm Hg did not change efficiency. However, increasing vacuum to 700 mm Hg decreased efficiency (p = 0.008 for 500 mm Hg vs 700 mm Hg and p = 0.05 for 600 mm Hg vs 700 mm Hg). Increasing aspiration and increasing vacuum did not significantly improve chatter.

CONCLUSIONS

Increasing aspiration above 50 mL/min did not improve phacoemulsification efficiency. Increasing vacuum settings to 700 mm Hg decreases efficiency. Chatter did not significantly change with increasing aspiration and vacuum settings.

[Comparison of ultrasound and hydrodynamic parameters in phacoemulsification]

Modern phacoemulsifiers have the widest selection of ultrasound parameters. Existing approaches to comparing the settings of the phaco machines have shortcomings and thus cannot be considered objective.

PURPOSE

To find a technique that would allow objective in vivo evaluation of various ultrasound and hydrodynamic parameters after performing phacoemulsification. To compare the two types of phaco settings using the proposed technique.

MATERIAL AND METHODS

The principle of the 'Femtocomparison' method is to have each patient undergo femtolaser pretreatment before phacoemulsification, in which the lens is divided by laser into equal parts and a corneal incision and capsulotomy are performed with the same settings. Then, during the manual part, basic ultrasound and hydrodynamic data is recorded after the removal of each quadrant of the lens. The study included 58 patients with cataracts of varying densities who underwent femtosecond laser-assisted cataract surgery. In each case, one half of the nucleus was removed using torsional ultrasound with IP technology, while the other half - using a combination of torsional and longitudinal ultrasound.

RESULTS

The 'Femtocomparison' technique allowed objective in vivo comparison of two types of ultrasound settings. When assessing these parameters, no significant differences were found in any of the patients regardless of the density of the lens nucleus (p>0.05). In soft nuclei group (NC 1-3) CDE were significantly lower when using torsional ultrasound and IP (p<0.05). In the group with dense nuclei (NC 6+), CDE and aspiration time were significantly lower when using combination ultrasound (p<0.05).

CONCLUSION

The 'Femtocomparison' technique has shown that torsional ultrasound with IP technology is preferable for aspiration of soft cataracts, while combined use of torsional and longitudinal ultrasound is better when removing dense lenses.

Effect of high vacuum and aspiration on phacoemulsification efficiency and chatter using a transversal ultrasound machine

PURPOSE

To examine the role of high vacuum and aspiration settings on efficiency using a transversal ultrasound (US) machine.

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine lens nuclei were incubated in formalin for 2 hours and then cut into 2.0 mm cubes. Phacoemulsification was performed using the Whitestar Signature machine. Settings were bottle height 50 cm, on-time 6 milliseconds, and off-time 6 milliseconds. One hundred percent power was used for all 240 runs. Tested parameters were aspiration of 50 mL/min and 60 mL/min and vacuum of 500, mm Hg, 600 mm Hg, and 650 mm Hg.

RESULTS

With continuous US, increasing aspiration from 50 mL/min to 60 mL/min significantly increased efficiency (23%). Increasing vacuum from 500 mm Hg to 650 mm Hg and from 600 mm Hg to 650 mm Hg significantly increased efficiency (20.2% and 13.6%, respectively). Higher vacuum and aspiration parameters did not influence the incidence of chatter events. In the micropulse US group, there was no significant efficiency increase with increasing vacuum or aspiration levels. There was a significant efficiency increase of continuous over micropulse US at an aspiration setting of 60 mL/min and vacuum settings of 600 mm Hg and 650 mm Hg.

CONCLUSIONS

As aspiration and vacuum increased, efficiency increased under continuous transverse US. No significant efficiency improvement occurred at high aspiration and vacuum settings under micropulse US. At 60 mL/min aspiration and more than 600 mm Hg vacuum, continuous power was significantly more efficient than micropulse transverse US.

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.

Effect of increasing flow when grooving during phacoemulsification

PURPOSE

To determine optimum flow settings on the Centurion Vision System during the grooving step in cataract surgery.

SETTING

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

DESIGN

Experimental study.

METHODS

Intact porcine lenses hardened by formalin and placed in a chamber designed to simulate the anterior chamber of the eye were used to test flow rate settings at 20 mL/min, 40 mL/min, and 60 mL/min. Vacuum was set at 400 mm Hg, longitudinal power at 80%, torsional power at 80%, and intraocular pressure at 50 mm Hg. A balanced phaco tip with a 20-degree tip and a 30-degree bevel was used. Efficiency (time to groove the lens in half) was determined.

RESULTS

Increasing flow from 20 to 40 mL/min during grooving increased efficiency by 17% (P = .05), with no significant improvement shown at 60 mL/min.

CONCLUSIONS

A flow rate of 40 mL/min was determined to be most efficient during the grooving step of cataract surgery. Further increases in flow rate showed no statistically significant improvement in efficiency, and with only 17% improvement flow rates less than 40 mL/min might be almost as efficient and might be safer.

Effect of chamber stabilization software on efficiency and chatter in a porcine lens model

PURPOSE

To evaluate the effects of the use of programmable chamber stabilization software (Chamber Stabilization Environment) settings on efficiency and chatter in a porcine lens model.

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine eyes were dissected and the lenses extracted. The lenses were then hardened and processed for the experiment. Phacoemulsification of the lens fragments was performed with the Whitestar Signature Pro with the Whitestar handpiece and a 0.9 mm straight Dewey tip with a 30-degree bevel. All arms of the study were run in peristaltic mode with 50 mL/minute aspiration, 100 cm bottle height, and on 100% power. The chamber stabilization software setting was used for each of the 4 study arms with a maximum vacuum of 500 mm Hg. Arm 1 included 20 runs with the up time set to 2000 milliseconds. Arm 2 was performed with similar settings but with an up time of 0 millisecond. Arms 3 and 4 were run with up times of 1000 milliseconds and 500 milliseconds, respectively.

RESULTS

The mean efficiency time of each run was as follows: 0 millisecond = 1.4 seconds, 500 milliseconds = 0.95 seconds, 1000 milliseconds = 0.88 seconds, 2000 milliseconds = 0.93 seconds. When compared with 0 millisecond, each of the other arms were significantly faster. Chatter events were comparable between the study arms.

CONCLUSION

The chamber stabilization software does not decrease efficiency when compared with full vacuum on if at least 500 milliseconds of up time is maintained.

The Effect of Pulsing on Transverse Ultrasound Efficiency and Chatter

PURPOSE

To evaluate the effects of micropulse, long pulse, and continuous ultrasound on transverse ultrasound using Abbott Medical Optics' (AMO) WhiteStar Signature Pro with the Ellips FX handpiece.

DESIGN

In vitro laboratory study.

METHODS

This study was conducted at the John A. Moran Eye Center Laboratory, University of Utah, Salt Lake City, Utah, USA. Porcine lenses were hardened in formalin for 2 hours and equilibrated in basic salt solution (BSS) over a 24-hour period. The lenses were then cubed in 2.0 × 2.0-mm pieces. These pieces were stored in BSS until the time of experimentation. The AMO WhiteStar Signature Pro machine (Abbott Medical Optics) with the Ellips FX handpiece and a 0.9-mm bent Dewey tip with a 30-degree bevel (Microsurgical Technology Inc) were used for phacoemulsification. Three runs of 20 lenses each were performed, measuring efficiency and chatter. Transverse ultrasound varied in the 3 runs and included continuous, 6 ms on/off micropulse, and 50 ms on/off long pulse.

RESULTS

Micropulse was more efficient than long pulse by 43% (P = .00003) and continuous by 42% (P = .000387). There were also less chatter events with micropulse than with long-pulse and continuous ultrasound. However, this difference did not reach significance.

CONCLUSION

The 6 ms on and 6 ms off micropulse transverse 3-dimensional ultrasound is more efficient and produces fewer chatter events than both long-pulse and continuous ultrasound.

Optimization of transversal phacoemulsification settings in peristaltic mode using a new transversal ultrasound machine

PURPOSE

To determine the optimum bottle height, vacuum, aspiration rate, and power settings in the peristaltic mode of the Whitestar Signature Pro machine with Ellips FX tip action (transversal).

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine lens nuclei were hardened with formalin and cut into 2.0 mm cubes. Lens cubes were emulsified using transversal and fragment removal time (efficiency), and fragment bounces off the tip (chatter) were measured to determine optimum aspiration rate, bottle height, vacuum, and power settings in the peristaltic mode.

RESULTS

Efficiency increased in a linear fashion with increasing bottle height and vacuum. The most efficient aspiration rate was 50 mL/min, with 60 mL/min statistically similar. Increasing power increased efficiency up to 90% with increased chatter at 100%.

CONCLUSION

The most efficient values for the settings tested were bottle height at 100 cm, vacuum at 600 mm Hg, aspiration rate of 50 or 60 mL/min, and power at 90%.

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.

Comparison of Vacuum and Aspiration on Phacoemulsification Efficiency and Chatter Using a Monitored Forced Infusion System

PURPOSE

To evaluate the effect of vacuum and aspiration rates on phacoemulsification efficiency and chatter using a monitored forced infusion system.

DESIGN

In vitro animal study.

METHODS

SETTING

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

PROCEDURES

Formalin-soaked porcine lenses were divided into 2 mm cubes (tip diameter, 0.9 mm). Vacuum levels were tested at 200, 300, 400, and 500 mm Hg; aspiration rates at 20, 35, and 50 mL/min. Torsional power was set at 60% and intraocular pressure at 50 mm Hg.

RESULTS

Increasing vacuum increased efficiency regardless of aspiration rates (R(2) = 0.92; P = .0004). Increasing aspiration further increased efficiency when vacuum was at 400 and 500 mm Hg (P = .004 for 20 vs 35 mL/min, P = .0008 for 35 vs 50 mL/min). At 200 and 300 mm Hg, efficiency only improved when increasing aspiration to 35 mL/min (P < .0001 with 20 vs 35 + 50 mL/min). Chatter improved with increasing vacuum, up to 400 mm Hg (P = .003 for 200 vs 300 mm Hg and P = .045 for 300 vs 500 mm Hg). A similar trend of improved chatter was seen with increasing levels of aspiration.

CONCLUSIONS

Vacuum improved efficiency up to 500 mm Hg independent of flow. Flow has an additive effect on efficiency through 50 mL/min, when vacuum is at 400 mm Hg or higher, and only up to 35 mL/min at vacuums less than 400 mm Hg. Chatter correlated with both vacuum and flow such that increasing either parameter decreases chatter, up to 400 mm Hg with vacuum.

Heat Generation and Efficiency of a New Modified Phaco Tip and Sleeve

PURPOSE

To compare a modified phacoemulsification tip with the established micro tip, in terms of temperature at the corneal wound, efficiency, and chatter events, using the Centurion® Vision system.

METHODS

Eighty porcine eyes were randomized into 4 groups: 1)sleeveless conventional 45D MiniFlared ABS® Kelman tip (1.1-mm incision); 2)sleeveless new modified 45D ABS® INTREPID® balanced tip(1.1-mm incision); 3) Kelman tip with own sleeve (2.2-mm incision); 4)Balanced tip with modified 4-rib sleeve (2.2-mm incision). Measurements were taken with 2 settings: longitudinal(power 40% and 70%) and torsional mode (power 40% and 100%). Peak temperatures were measured 0, 10, 30, and 60 seconds after continuous ultrasound power. For the efficiency test, porcine lens nuclei were formalin soaked and cut into 2.0 mm3 cubes. Efficiency and chatter were examined.

RESULTS

In all longitudinal settings, the sleeveless groups(1 and 2) showed lower temperatures than the sleeved groups(3 and 4) (P = 0.003). In 100% torsional mode, groups 3 and 4 produced significantly different temperatures(37.13 ± 1.44 and 35.14 ± 0.54, respectively; P = 0.007).The efficiency, in a 100% power torsional setting, was13.52 ± 2.60 sec for group 4, and 44.45± 14.75 sec for group 3 (P<0.001).

CONCLUSIONS

The two different bare tips show no significant differences in thermogenesis. However, the balanced tip with sleeve produces lower temperaturesat100% torsional power and better efficiency than the Kelman tip.

Comparison of a torsional and a standard tip with a monitored forced infusion phacoemulsification system

PURPOSE

To compare the relative efficiency and chatter of the 30-degree 0.9 mm Kelman tip (standard tip) and Ozil Intrepid Balanced tip (torsional tip) with identical optimum settings.

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine nuclei were fixed in formalin and cut into 2.0 mm cubes. Lens cubes were phacoemulsified with standard and torsional tips at 60% and 100% torsional amplitude with 0%, 25%, 50%, 75%, and 100% longitudinal power with monitored forced infusion. Experiments were performed at a constant vacuum, aspiration rate, and intraocular pressure.

RESULTS

Linear regression showed increased efficiency with up to 75% longitudinal power at 60% torsional amplitude for both tips (P = .046 standard; P = .0093 torsional). Longitudinal did not significantly increase efficiency at 100% torsional power for either tip. Torsional tips were on average 29% more efficient than standard tips throughout the range tested (P < .0001), and 100% torsional power was on average 45% more efficient than 60% torsional power (P = .0028). Chatter was minimal except at 100% longitudinal power, which was greater than at 75% longitudinal power (P < .0001). At 100% longitudinal power, torsional tips had more chatter than standard tips (at 60% torsional, P < .0001; at 100% torsional, P = .0022).

CONCLUSIONS

Increasing up to 75% longitudinal power increased the efficiency at 60% torsional for standard and torsional tips. Torsional tips were more efficient than standard tips. Chatter was generally minimal. Torsional tips showed more chatter than standard tips at 100% longitudinal power.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Torsional power study using CENTURION phacoemulsification technology

BACKGROUND

To evaluate the effect of varying levels of power on phacoemulsification efficiency using the CENTURION Vision System.

METHODS

Formalin-soaked porcine lenses were divided into 2-mm cubes; 0.9-mm, balanced tips were used. Torsional power levels were tested from 10% to 100% at 10% intervals. Vacuum was set to 550 mmHg, aspiration to 50 ml/min, and intraocular pressure at 50 mmHg. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined.

RESULTS

Increasing torsional power up to 60% increased efficiency. This effect was linear from 30 to 60% power (R²  = .90; P < 0.05). There were no significant differences in efficiency past 60%. Chatter was highest at 10% power and decreased linearly (R²  = .87; P = 0.007) as power was increased up to 60% power, and chatter did not improve above this power level.

CONCLUSIONS

Power improved efficiency only up to a 60% power level, and then was negligible. Chatter correlated well with power up to the 60% level, so that as power was increased, chatter decreased. Because there are no additional benefits in efficiency past 60% power, and because chatter is minimal at 60% power, we recommend torsional ultrasound at 60% as the optimal power setting for using the CENTURION System for phacoemulsification.l.

Thermal evaluation of two phacoemulsification systems

OBJECTIVE

To compare thermal profiles of new transversal ultrasound power modulation to torsional ultrasound in an artificial chamber and cadaver eye.

DESIGN

Laboratory investigation.

METHODS

John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Temperature increase after 30 seconds was measured at the needle midshaft in an artificial chamber and at maximal friction point in a cadaver eye. Ellips FX (transverse) was tested at 100% power, as was Signature with micropulse settings (6 milliseconds on and off). OZil (torsional only) was tested at 100% power in the artificial chamber and cadaver eye. Runs were completed with aspiration blocked. Temperature was continuously measured on the phacoemulsification sleeve using a microthermistor probe connected to the BAT-10 multipurpose thermometer, with an accuracy of ±0.1°C.

RESULTS

Transversal FX had a greater temperature increase than micropulse (p < 0.001) and torsional (p < 0.001). Micropulse had a greater temperature increase than torsional (p < 0.001). The cadaver eye had a greater temperature increase than the artificial chamber for torsional (p < 0.001).

CONCLUSIONS

Higher heat accumulation and potential for incisional burn occurred with the cadaver model than with the artificial chamber, suggesting the need for caution when using 100% torsional ultrasound with aspiration blocked. Transversal FX generated more heat than was reported originally. Further study is needed to determine the incidence of incisional burn with varied power settings for this new model. Micropulse generated more heat than previous reports, but the increased efficiency is likely to negate potentially increased incisional burn risk.

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.

Bent versus straight tips in micropulsed longitudinal phacoemulsification

OBJECTIVE

The aim of this study was to evaluate bent and straight phacoemulsification tips to determine which tip is more efficient in removal of lens fragments, using micropulsed longitudinal ultrasound in phacoemulsification.

DESIGN

In vitro laboratory study.

METHODS

The John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Pig lenses hardened in a manner comparable with dense human cataracts were cut into 2-mm cubes and removed with micropulsed longitudinal ultrasound using settings previously shown to be optimally efficient (6 milliseconds on and 6 milliseconds off for a bent tip). To verify this time as most efficient for a straight tip, we also tested times of 5, 6, and 7 milliseconds time on and off. The tips were either straight or with a 20-degree bend. Twenty cubes were used for each comparative run.

RESULTS

For the straight tip, 6 milliseconds on (1.56 ± 0.815 seconds) was significantly more efficient than 7 milliseconds on (2.45 ± 1.56 seconds, p = 0.001) and not significantly more efficient than 5 milliseconds on (1.69 ± 0.86 seconds, p = 0.43). Five milliseconds off time (1.45 ± 0.76s) was more efficient than 6 milliseconds (2.06 ± 1.37 seconds, p = 0.004) and 7 milliseconds off (2.18 ± 1.24s, p = 0.001). The straight tip was more efficient than the bent tip (1.38 ± 0.83 versus 2.93 ± 2.14 seconds, p = 0.006).

CONCLUSIONS

Results are contrary to accepted common belief. Micropulsed longitudinal phacoemulsification is more efficient with a straight rather than a bent tip.

Comparison of venturi and peristaltic vacuum in phacoemulsification

PURPOSE

To evaluate the efficiency of peristaltic-based and venturi-based vacuums.

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine lenses were hardened with formalin and cut into 2.0 mm cubes. Time to fragment removal (efficiency) and fragment bounces off the tip (chatter) were measured using a Signature machine with the ability to switch between peristaltic-based and venturi-based vacuum. Micropulse longitudinal and transversal ultrasound motions were tested.

RESULTS

Venturi-based vacuum had increased efficiency and decreased chatter compared with peristaltic-based vacuum at lower vacuum levels.

CONCLUSION

Use of a venturi-based vacuum, when available, may result in reduced clearance time of lens material and mitigate chatter even under noisy conditions.

FINANCIAL DISCLOSURE

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

Safety Profile of Venturi Versus Peristaltic Phacoemulsification Pumps in Cataract Surgery Using a Capsular Surrogate for the Human Lens

PURPOSE

To compare the risk of capsular rupture of the human lens during cataract surgery from contact by phacoemulsification needles using different vacuum pumps, ultrasound modalities, and contact angles.

DESIGN

Experimental laboratory investigation.

METHODS

The John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, was the setting for this study. A Signature (Abbott Medical Optics, Inc) phacoemulsification machine was used in peristaltic and Venturi vacuum modes with transversal and micropulsed ultrasound. Contact was made with a capsular surrogate to achieve tip occlusion or tip contact only. Breakage rates were calculated by analyzing the capsular surrogate under a surgical microscope.

RESULTS

Venturi and peristaltic pump modes had similar risk of capsular rupture, regardless of whether the data were analyzed with tip occlusion data included (44.2% peristaltic vs 40.2% Venturi, P = .047) or excluded from the analysis (66.3% peristaltic vs 60.3% Venturi, P = .013). Transversal ultrasound was significantly more likely to cause capsular rupture than micropulsed ultrasound (69.8% vs 56.8%, P < .0001). Tip contact was significantly more likely than tip occlusion to cause capsular rupture (63.3% vs 0%, P < .0001).

CONCLUSIONS

There is no significant difference in risk of capsular rupture using Venturi rather than peristaltic vacuum pumps, while transversal seemed to increase the risk when compared to micropulsed ultrasound. Tip occlusion is not a risk factor for capsular rupture, as all breaks in the capsular surrogate occurred with tip contact.

Impact of micropulsed ultrasound power settings on the efficiency and chatter associated with lens-fragment removal

PURPOSE

To determine the optimum power settings in micropulsed ultrasound (US).

SETTING

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

DESIGN

Experimental study.

METHODS

Pig lenses hardened to be comparable to dense human cataracts were cut into 2.0 mm cubes and removed using micropulsed longitudinal US with previously optimized settings (6 milliseconds on and 6 milliseconds off and using a 0.9 mm 30-degree beveled bent phaco tip). The aspiration was set at 40 mL/min and the vacuum level at 550 mm Hg. Twenty lens cubes were tested with the power set from 10% to 100% in increments of 10%. Primary outcome measures were efficiency time (time to lens removal) and chatter (number of times the lens fragment visibly bounced off the tip).

RESULTS

Efficiency time decreased with increasing power. There was a correlation between power and efficiency time (R(2) = 0.41, P = .046), which was more substantial between 30% and 100% power (R(2) = 0.71, P = .004). The mean number of chatter events did not differ significantly between power settings (R(2) = 0.012, P = .1195).

CONCLUSIONS

There was a 5-fold increase in efficiency between 10% power and 20% power, which likely indicates that there is a minimum power threshold for efficient breakup of the lens. Between 20% and 100% power, there was a linear, strong, and statistically significant improvement in efficiency in these lens fragments. In addition, with micropulsed US there was little chatter or microchatter throughout the power range.

FINANCIAL DISCLOSURE

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

The Impact of Reused Phaco Tip on Outcomes of Phacoemulsification Surgery

PURPOSE

To evaluate the impact of reused phaco tip on intraoperative performance and postoperative outcomes after 2.2 mm micro-coaxial torsional and transversal phacoemulsification.

MATERIAL AND METHODS

This prospective randomized study enrolled 136 eyes of 136 cataract patients; 68 eyes in torsional group (34 eyes with single use tip, 34 eyes with reused tip) and 68 eyes in transversal group (34 eyes with single use tip, 34 eyes with reused tip). Intraoperative measurements were total ultrasound (U/S) time, torsional U/S time, cumulative dissipated energy (CDE), estimated fluid use (EFU) in the torsional group and total phacoemulsification time (TPT), and effective phacoemulsification time (EPT) in transversal phacoemulsification. The central endothelial cell density (ECD) and the central corneal thickness (CCT) were evaluated preoperatively and postoperatively at 1 and 30 days using noncontact specular microscopy.

RESULTS

Intraoperative measurements in torsional phacoemulsification showed significant increase in total U/S time (p = 0.01), torsional U/S time (p = 0.01), and CDE (p = 0.01) with the reused tip. The EFU was similar in both tip groups (p = 0.36). The total U/S time, torsional U/S time, and CDE in torsional group were significantly increased with the reused tip for grade III (p = 0.03 for all parameters) and grade IV cataracts (p = 0.005 for torsional U/S time and CDE; p = 0.006 for total U/S time). Intraoperative measurements in transversal phacoemulsification showed no differences in TPT and EPT between tip groups (p > 0.05). The change in ECD and CCT in torsional and transversal phacoemulsification groups were similar in both tip groups (p > 0.05).

CONCLUSIONS

This study showed that sharpness of phaco tip edge increases the efficiency of torsional phacoemulsification for hard cataracts. This result does not mean that reused phaco tip may be used in soft and medium cataracts. As the timing of tip's change is a user-dependent procedure, a new single phaco tip should be used in each case if possible.

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.

Determining optimal torsional ultrasound power for cataract surgery with automatic longitudinal pulses at maximum vacuum ex vivo

PURPOSE

To determine the optimal longitudinal power settings for Infiniti OZil Intelligent Phaco (IP) at varying torsional amplitude settings; and to test the hypothesis that increasing longitudinal power is more important at lower torsional amplitudes to achieve efficient phacoemulsification.

DESIGN

Laboratory investigation.

METHODS

setting: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. procedure: Individual porcine nuclei were fixed in formalin, then cut into 2.0 mm cubes. Lens cube phacoemulsification was done using OZil IP at 60%, 80%, and 100% torsional amplitude with 0%, 10%, 20%, 30%, 50%, 75%, or 100% longitudinal power. All experiments were done using a 20 gauge 0.9 mm bent reverse bevel phaco tip at constant vacuum (550 mm Hg), aspiration rate (40 mL/min), and bottle height (50 cm). main outcome measure: Complete lens particle phacoemulsification (efficiency).

RESULTS

Linear regression analysis showed a significant increase in efficiency with increasing longitudinal power at 60% torsional amplitude (R(2) = 0.7269, P = .01) and 80% torsional amplitude (R(2) = 0.6995, P = .02) but not at 100% amplitude (R(2) = 0.3053, P = .2). Baseline comparison of 60% or 80% vs 100% torsional amplitude without longitudinal power showed increased efficiency at 100% (P = .0004). Increasing longitudinal power to 20% abolished the efficiency difference between 80% vs 100% amplitudes. In contrast, 75% longitudinal power abolished the efficiency difference between 60% vs 100% torsional amplitudes.

CONCLUSIONS

Results suggest that longitudinal power becomes more critical at increasing phacoemulsification efficiencies at torsional amplitudes less than 100%. Increasing longitudinal power does not further increase efficiency at maximal torsional amplitudes.

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.

Effect of phaco tip diameter on efficiency and chatter

PURPOSE

To evaluate 3 phacoemulsification tips of different sizes and determine which size is most efficient in lens fragment removal using 3 ultrasound (US) approaches.

SETTING

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

DESIGN

Experimental study.

METHODS

Porcine lens nuclei were formalin-soaked for 2 hours then divided into 2.0 mm cubes; 1.1 mm, 0.9 mm, and 0.7 mm phaco tips were used with torsional and micropulsed US. The 1.1 mm tips were unavailable for torsional US, so 0.9 mm and 0.7 mm tips were used. Efficiency (amount of time for lens removal) and chatter (number of lens-fragment repulsions from the tip) were determined.

RESULTS

The mean phacoemulsification efficiency was highest with the 0.9 mm tip for all US variations. There were statistically significant differences between the 0.9 mm and 0.7 mm tips with micropulsed US (0.8 seconds ± 0.29 [SD] versus 1.4 ± 0.93 seconds; P=.0112) and transversal US (0.8 ± 0.17 seconds versus 1.4 ± 0.89 seconds; P=.0065). There was no significant difference between 0.9 mm and 0.7 mm tips with torsional US or between the 1.1 mm and 0.9 mm tips with micropulsed or transversal US; however, trends were identical, with 0.9 mm tips performing better than 0.7 mm and 1.1 mm tips.

CONCLUSION

With all 3 systems, the 0.9 mm tip was most efficient, with the fewest outliers and smallest standard deviation.

FINANCIAL DISCLOSURE

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

Thermal imaging comparison of Signature, Infiniti, and Stellaris phacoemulsification systems

Background

To compare the heat production of 3 different phacoemulsification machines under strict laboratory test conditions. More specifically, the thermal behavior was analyzed between the torsional modality of the Infiniti system and longitudinal modalities of the Abbot WhiteStar Signature Phacoemulsification system and Bausch and Lomb Stellaris system.

Methods

Experiments were performed under in-vitro conditions in this study.

Three phacoemulsification handpieces (Infiniti, Signature, and Stellaris) were inserted into balanced salt solution-filled silicone test chambers and were imaged side-by-side by using a thermal camera. Incision compression was simulated by suspending 30.66-gram weights from the silicone chambers. The irrigation flow rate was set at 0, 1, 2, 3, 4, and 5 cc/min and the phacoemulsification power on the instrument consoles was set at 40, 60, 80, and 100%. The highest temperatures generated from each handpiece around the point of compression were measured at 0, 10, 30, and 60 seconds.

Results

Under the same displayed phacoemulsification power settings, the peak temperatures measured when using the Infiniti were lower than when using the other two machines, and the Signature was cooler than the Stellaris. At 10 seconds, torsional phacoemulsification with Infiniti at 100% power showed data comparable to that of the Signature at 80% and the Stellaris at 60%. At 30 seconds, the temperature from the Infiniti at 100% power was lower than the Signature at 60% and the Stellaris at 40%.

Conclusions

Torsional phacoemulsification with the Infiniti generates less heat than longitudinal phacoemulsification with the Signature and the Stellaris. Lower operating temperatures indicate lower heat generation within the same fluid volume, which may provide additional thermal protection during cataract surgery.