Jeff H. Pettey

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.

Evaluation of variables affecting intraoperative aberrometry

PURPOSE: To understand some of the variable refractive changes that occur during routine cataract surgery that could affect the accuracy and effectiveness of intraoperative aberrometry as it relates to the postoperative refractive state. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA. DESIGN: Comparative case series. METHODS: Phase 1 of this study assessed the cylinder induced by 2 eyelid speculums (open wire and closed wire) with corneal topographic images from participants without cataract. Phase 2 assessed the refractive change in cylinder, its axis, and the spherical equivalent (SE) in cataract patients within 1 hour of cataract surgery compared with 1 week after surgery. These measurements were taken using wavefront aberrometry, manual refraction, and corneal topography. RESULTS: Phase 1 evaluated 99 corneal topographic images from 5 participants. The presence of a speculum induced erratic changes in cylinder and a statistically significant difference in axis when comparing the open‐wire speculum and the closed‐wire speculum (both P<.0001). In phase 2, which evaluated 10 patients, there was a significant change in the SE within 1 hour of cataract surgery compared with 1 week after surgery (P=.039). CONCLUSION: Cataract surgery induced changes in cylinder, its axis, and the SE. This suggests that decisions based on intraoperative aberrometry may be inaccurate. 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.

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.

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.

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.

Effect of increased vacuum and aspiration rates on phacoemulsification efficiency

Purpose To evaluate the effect of vacuum and aspiration rates on phacoemulsification efficiency. Setting John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. Design Experimental study. Methods Formalin‐soaked porcine lenses were divided into 2.0 mm cubes, and 0.9 mm 30‐degree beveled 20‐degree bent tips were used with micropulse ultrasound (US) (6 milliseconds on and 6 milliseconds off) and a peristaltic flow system. Vacuum levels were tested at 200, 300, 400, and 500 mm Hg, and aspiration rates were tested at 20, 35, and 50 mL/min. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were determined. Results Increasing vacuum increased efficiency only when going from 200 mm Hg to higher vacuum levels. Increasing aspiration increased efficiency at all points measured (25 mL/min versus 35 mL/min, P < .0001; 35 mL/min versus 50 mL/min, P = .012; 25 mL/min versus 50 mL/min, P < .0001). Chatter was highest at 200 mm Hg and decreased when vacuum was increased from 200 mm Hg to 300 mm Hg and up. Chatter decreased with increasing flow. Conclusions Vacuum improved efficiency only up to 300 mm Hg and was more dependent on increasing flow. Similarly, chatter correlated with 200 mm Hg vacuum only and was more correlated with flow. Limitations of this study include use of only 1 US power modulation and hard nuclear material. 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.