Jason D. Jensen

Porcine lens nuclei as a model for comparison of 3 ultrasound modalities regarding efficiency and chatter

Purpose To validate a porcine lens model by comparing density and ultrasound (US) with known human standards using the Infiniti Ozil with Intelligent Phacoemulsification (torsional), Whitestar Signature Micropulse (longitudinal), and Ellips FX (transversal) modalities. Setting Department of Ophthalmology and Visual Sciences, John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. Design Experimental study. Methods Lens nuclei were formalin soaked in hour‐based intervals and divided into 2.0 mm cubes. Density was characterized by crushing experiments and compared with known human measures. Efficiency and chatter were examined. Results The mean weight to cut thickness in half ranged from 16.9 g ± 5.5 (SD) in the 0‐hour group to 121.3 ± 47.5 gm in the 4‐hour group. Lenses in the 2‐hour group (mean 70.2 ± 19.1 g) best matched human density (P=.215). The mean efficiency ranged from 0.432 ± 0.178 seconds to 9.111 ± 2.925 seconds; chatter ranged from zero to 1.85 ± 1.927 bounces. No significant difference was detected when comparing the 2‐hour formalin group with human lenses in torsional and transversal US. There was no significant difference between transversal and torsional modalities, consistent with human studies. Although longitudinal (6 milliseconds on, 12 milliseconds off) was significantly more efficient at 50% power than at 25%, there was no significant difference compared with transversal or torsional US. Conclusions Animal lenses soaked for 2 hours in formalin were most comparable to human lenses. Longitudinal US may be an acceptable alternative to torsional and transversal US. Financial Disclosure Dr. Olson has been a consultant to Abbott Medical Optics, Inc., Becton, Dickinson and Co., and Allergan, Inc., and received grant support from Abbott Medical Optics, Inc. and Allergan, Inc. No author has a financial or proprietary interest in any material or method mentioned.

Objective comparison of 4 nonlongitudinal ultrasound modalities regarding efficiency and chatter.

PURPOSE: To compare efficiency and chatter of Infiniti Ozil with and without Intelligent Phacoemulsification (IP) and the Signature Ellips with and without FX. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Brunescent 2.0 mm human lens cubes were created by an instrument devised for this study. Cubes were tested (10 per test) for time of particle removal (efficiency) and for the number of times the lens particle bounced off the tip (chatter) at 300 mm Hg and 550 mm Hg, 50% and 100% power, and 50% and 100% amplitudes (amplitude for Ozil only). RESULTS: Of the ultrasound settings, efficiency varied from a mean of 3.3 seconds ± 1.4 (SD) to 50.4 ± 11.7 seconds and chatter from 0.0 to 52.0 ± 16.7 bounces per run. The Ozil‐IP was generally more efficient than the Ozil and the Ellips FX more efficient than the Ellips. At optimized values, the Ozil‐IP and Ellips‐FX were similar. In general, efficiency and chatter were better at 550 mm Hg and at 50% power. The amplitude effect was complex. Efficiency closely correlated with chatter (Pearson r2 = .31, P<.0001). CONCLUSIONS: Objective comparison of phacoemulsification efficiency and chatter found that optimized Ozil‐IP and Ellips‐FX were similar in both parameters and in general, both performed better than preceding technology. The study parameters can significantly affect efficiency and chatter, which strongly correlate with each other. Financial Disclosure: Dr. Olson has been a consultant to Abbott Medical Optics, Inc., Becton, Dickinson and Co., and Allergan, Inc., and has received grant support from Abbott Medical Optics, Inc., and Allergan, Inc. 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.

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 (R2 = .87, P = .24). A significant linear decrease in efficiency was observed with 6 to 20 ms (R2 = .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.

Phacoemulsification efficiency with a radiused phaco tip

Purpose To evaluate radiused and nonradiused phacoemulsification tips to determine which tip is more efficient in removal of lens fragments using 3 ultrasound (US) modalities. 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 or 3 hours and then divided into 2.0 mm cubes. Thirty‐degree, 0.9 mm beveled radiused tips and nonradiused tips were used with torsional, transverse, and micropulsed US modalities. Bent tips were used with torsional and transversal US, and straight tips were used with micropulsed US. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined. Results The mean phacoemulsification efficiency was statistically significantly decreased (increased time for removal) with the radiused tip compared with the nonradiused tip for torsional US only (2‐hour soaked lenses: 2.14 seconds ± 1.94 [SD] versus 1.18 ± 0.69 seconds [P < .05]; 3‐hour soaked lenses: 5.07 ± 4.2 seconds versus 2.52 ± 1.99 seconds [P < .05]). There was no difference in chatter results. Conclusion The radiused tip showed decreased efficiency with torsional US only. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

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 (R2 = 0.41, P = .046), which was more substantial between 30% and 100% power (R2 = 0.71, P = .004). The mean number of chatter events did not differ significantly between power settings (R2 = 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.

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.

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

Intraocular pressure study using monitored forced-infusion system phacoemulsification technology

Purpose To optimize phacoemulsification efficiency by varying the intraocular pressure (IOP) using the Centurion Vision System, a monitored forced‐infusion system. Setting John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. Design Laboratory investigation. Methods Porcine lenses were soaked in formalin and divided into 2.0 mm cubes; 0.9 mm balanced tips were used. Intraocular pressure levels were tested from 30 to 110 mm Hg at 10 mm Hg intervals. Vacuum was set at 500 mm Hg, aspiration at 35 mL/min, and torsional power at 60%. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were measured. Results There was a linear relationship between efficiency and IOP. Increasing IOP led to an increase in efficiency (ie, to a decrease in time necessary to remove the lens fragment) (R2 = .5769, P = .0176). Chatter correlated with IOP in the range of 30 to 50 mm Hg (R2 = .4506, P = .0448) and was minimal at higher IOPs. Conclusions Increasing IOP in the monitored forced‐infusion system improved efficiency. Chatter was also decreased or eliminated with increasing IOP. Additional studies will be required to understand the reasons for these findings. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned.

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.