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David C. Buboltz, Dina Joy K. Abulon; Analysis of Porcine Vitreous Flow during Simulated Vitrectomy. Invest. Ophthalmol. Vis. Sci. 2011;52(14):6134.
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© ARVO (1962-2015); The Authors (2016-present)
To examine the effects of high speed cutting on flow rate of aspirated porcine vitreous using dual pneumatic vitrectomy probes.
Vitreous flow rates of 23-gauge cutters (n=6) were analyzed at 500-5000 cuts per minute (cpm), 250-650 mmHg vacuum, and at various duty cycles. An electronic balance measured the mass of vitreous aspirated from a porcine eye. A computer converted real-time mass measurements into flow rates. All data were analyzed using linear regression and Student’s t-test.
Vitreous flow of 23-gauge probes was relatively constant for all cut rates in the biased open mode (R2≤0.2). At 650 mmHg vacuum, biased open vitreous flow rates ranged from 3.82 ± 1.08 (at 500 cpm) to 3.69 ± 0.92 cc/min (at 5000 cpm cut rate). In the 50% and bias closed duty cycle, vitreous flow increased with increasing cut rate. At 650 mmHg vacuum, vitreous flow at 50% duty cycle increased from 1.83 ± 0.63 cc/min (500 cpm) to 4.12 ± 0.81 cc/min (5000 cpm). In the bias closed duty cycle, vitreous flow at 650 mmHg increased from 0.56 ±0.76 (500 cpm) to 4.82 ± 0.77 cc/min (5000 cpm). The rate of increase in the bias closed mode was higher than the 50% duty cycle. The slope of trendlines in the bias closed duty cycle at 250, 450, and 650 mmHg vacuum were 0.1, 0.2, and 0.5 µL/, respectively (R2≥0.7). Trendline slopes for vitreous flow at 50% duty cycle at 250, 450, and 650 mmHg vacuum were 0.2, 0.5, 0.9 µL/cut, respectively (R2≥0.9).
In comparison to previously published clear fluid flow rates, the data suggests that the effects of high speed cutting (reduced bite size) reduces the resistance to flow and allows for more efficient vitreous removal. This study helps characterize vitreous flow behavior during vitrectomy and demonstrates that vitreous aspiration cutters may be improved at high rates.
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