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J. Zhou, D. J. K. Abulon, D. C. Buboltz; Relationships of Duty Cycle versus Cut Rate for Two Commercially Available Vitrectomy Systems. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3608.
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© ARVO (1962-2015); The Authors (2016-present)
Duty cycle is the percentage of time a cutter port is open, relative to the complete cutting cycle. Duty cycles affect flow rates in vitreoretinal surgery. This study compared the relationships between duty cycle and cut rate among commercially available vitrectomy systems.
Two vitrectomy systems were tested: the Millennium Microsurgical System (Bausch & Lomb, Inc.) with the Millennium Vitrectomy Enhancer (MVE), and the Constellation Vision System (Alcon). Six probes each of 25+-, 23-, 20-, and 25-gauge diameters were tested (per availability) across the full range of cut speeds with each system. Duty cycles were calculated from high-speed video files of probes operating while suspended in cuvettes that were filled with balanced salt solution.
With the MVE system, and the "core" setting of the Constellation Vision System, duty cycles were biased open (values >85%) at lower cut rates, and duty cycles decreased as cut rate increased. Minimum duty cycle for the MVE was 46 +/- 1 percent at a maximum cut rate of 2500 cpm. The Constellation Vision System in "core" mode at 2500 cpm was 72 +/- 2 percent duty cycle at 2500 cpm. At a maximum cut rate of 5000 cpm, the Constellation Vision System duty cycle was 52 +/- 2 percent in "core" mode. With the "shave" mode of the Constellation Vision System, duty cycle was <15% at lower cut rates and duty cycle increased to an 52 +/- 3 percent at the maximum cut rate of 5000 cpm. With the "50/50" mode of the Constellation system, duty cycle was essentially constant across the range of cut speeds; duty cycle values were 52 +/- 2 percent (range, 49% to 56%).
The Constellation Vision System in the "core" mode had higher duty cycles than the MVE for the same cut rates. While the MVE maximum cut rate was 2500 cpm, the Constellation Vision System maximum cut rate was 5000 cpm. The Constellation Vision System also had additional duty cycle control that could be advantageous for controlling flow during different phases of vitreoretinal surgery. With duty cycle control, the performance of the system can be tailored to the surgical objective.
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