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Yau Kei J. Chan, Theodor Stappler, David Wong; What Influences The Shear Rate Acting On Silicone Oil To Cause It To Emulsify?. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3770.
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Emulsification of silicone oil is caused by the shear force generated by eye movement. In the past, we investigated the effect of shear- and extensional-viscosities of silicone oil on the shear rate. We now study the extent of silicone oil filling and the presence of indentation within the vitreous cavity.
A model eye chamber made of surface-modified polymethymethacrylate (capacity 6ml) was driven by a stepper-motor to mimic large-amplitude eye movements (amplitude 90o, angular velocity 360o/s and a duration 300ms). Two indents made of agarose were introduced to simulate an encircling scleral buckling. Two silicone oils (1,300 and 5,000mPa.s), three volumes (3, 4 and 5ml) and two eye chambers (with and without indents) were tested. The movements of the oils inside the model chamber were captured by video recordings.
The presence of indentation significantly reduced the velocity of the oil relative to the eye chamber. The extent of fill and the viscosity also had a significant but lesser effect. The peak velocity of the oil relative to the eye chamber was recorded at 349o/s. This occurred when there was no indentation in the chamber and when it was filled with 3 ml of 1,300mPa.s oil.
Of the three factors investigated, the presence of indent seemed to have the greatest influence on the shear rate. Scleral buckling and a more complete fill of an eye cavity may be as important as the use of high viscosity oils in preventing emulsification.
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