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. 2015 Feb 5:9:253-61.
doi: 10.2147/OPTH.S71387. eCollection 2015.

Vitreous flow rates through dual pneumatic cutters: effects of duty cycle and cut rate

Dina Joy K Abulon  1
Affiliations

Vitreous flow rates through dual pneumatic cutters: effects of duty cycle and cut rate

Dina Joy K Abulon. Clin Ophthalmol. .

Abstract

Purpose: We aimed to investigate effects of instrument settings on porcine vitreous flow rates through dual pneumatic high-speed vitrectomy probes.

Methods: The CONSTELLATION(®) Vision System was tested with 250, 450, and 650 mmHg of vacuum using six ULTRAVIT(®) vitrectomy probes of each diameter (25+(®), 25, 23, and 20 gauge) operated from 500 cuts per minute (cpm) up to 5,000 cpm. Duty cycle modes tested included biased open, 50/50, and biased closed. Flow rates were calculated by assessing the change in weight of porcine eyes during vitreous aspiration. Volumetric flow rate was measured with a computer-connected electronic scale.

Results: At lower cut rates, the biased open mode produced higher flow than did the 50/50 mode, which produced higher flow than did the biased closed mode. In the biased closed and 50/50 modes, vitreous flow rates tended to increase with increasing cut rate. Vitreous flow rates in the biased open duty cycle mode remained relatively constant across cut rates.

Conclusion: Vitreous flow rates through dual pneumatic vitrectomy probes could be manipulated by changing the duty cycle modes on the vitrectomy system. Differences in duty cycle behavior suggest that high-speed cut rates of 5,000 cpm may optimize vitreous aspiration.

Keywords: 20-gauge vitrectomy; 23-gauge vitrectomy; 25-gauge vitrectomy; Constellation Vision System; aspiration; enhanced 25-gauge vitrectomy.

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Figures

Figure 1
Figure 1
Vitreous flow through enhanced 25-gauge probes. Notes: Each data point represents the average flow rate calculated from six probes, with error bars representing 95% CIs. The asterisks mark flow rate values that are significantly higher than the corresponding values obtained with 25-gauge probes (P<0.05). (A) Biased closed duty cycle; (B) 50/50 duty cycle; (C) biased open duty cycle. Bold lines indicate linear regression trends. Abbreviations: CI, confidence interval; cpm, cuts per minute.
Figure 2
Figure 2
Vitreous flow through 25-gauge probes. Notes: Each data point represents the average flow rate calculated from six probes, with error bars representing 95% CIs. (A) Biased closed duty cycle; (B) 50/50 duty cycle; (C) biased open duty cycle. Bold lines indicate linear regression trends. Abbreviations: CI, confidence interval; cpm, cuts per minute.
Figure 3
Figure 3
Vitreous flow through 23-gauge probes. Notes: Each data point represents the average flow rate calculated from six probes, with error bars representing 95% CIs. (A) Biased closed duty cycle; (B) 50/50 duty cycle; (C) biased open duty cycle. Bold lines indicate linear regression trends. Abbreviations: CI, confidence interval; cpm, cuts per minute.
Figure 4
Figure 4
Vitreous flow through 20-gauge probes. Notes: Each data point represents the average flow rate calculated from six probes, with error bars representing 95% CIs. (A) Biased closed duty cycle; (B) 50/50 duty cycle; (C) biased open duty cycle. Bold lines indicate linear regression trends. Abbreviations: CI, confidence interval; cpm, cuts per minute.
Figure 5
Figure 5
Comparison of flow for vitreous body and for buffered saline solution (“aqueous”). Notes: All results are for the biased open duty cycle mode and represent average flow rate calculated from six probes. Fold differences between vitreous and aqueous flow are provided. (A) 20-gauge probe; (B) 23-gauge probe; (C) 25-gauge probe; (D) enhanced 25-gauge probe. Abbreviation: cpm, cuts per minute.
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