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Pooria Sharif-Kashani, Kentaro Nishida, Ryan Freeman, H.Pirouz Kavehpour, Steven D. Schwartz, Jean Pierre Hubschman; Effect of Cut Rates on Fluidity of Chopped Vitreous. Invest. Ophthalmol. Vis. Sci. 2012;53(14):2598.
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To analyze the rheological properties of the chopped vitreous (cut using vitrectomy) at different cut rates to better understand the effects of instrument setting such as cut rate on fluid flow of vitrectomy.
20 and 25 gauge cutters were used to cut 107 porcine eyes at different cut rates of 500, 1000, 1500, 2000, and 2500 cuts per minute (cpm) with a fixed vacuum pressure of 500 mmHg. Each sample was immediately tested using a shear rheometer to obtain its fluidic properties such as viscosity and elasticity.
Chopped vitreous demonstrated significantly lower viscosity (0.039 ± 0.01 Pa•s) than intact vitreous (908.1 ± 421.6 Pa•s). However, cut rate did not have any significant impact on viscosity. In addition, chopped vitreous presented elastic behavior, which directly effect the fluid flow of vitrectomy. It was shown that the compliance, the inverse of stiffness, of chopped vitreous is much higher than that of intact vitreous (1.836 ± 0.627 1/Pa) for intact vitreous and 85.3 ± 28.7 1/Pa for chopped vitreous) and varies in a nonlinear fashion when cut at different cut rates.
Cut rate significantly affects the rheological properties of the chopped vitreous and therefore, its flow inside the vitrectomy system. It is essential to account for physical properties of chopped vitreous including viscosity and elasticity to understand and optimize fluidics in vitrectomy.
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