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Mai Thao, Daniel Perez, James Dillon, Elizabeth Gaillard; The viscosity of the lens. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5730.
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To determine the viscosity of the lens so the diffusion coefficient of oxygen and other nutrients can be calculated using the Stokes-Einstein equation.
The Ocean Optics Foxy Oxygen Sensor probe is air saturated at about 20.8% oxygen (158 mm Hg). It was immediately placed into a container that contains a glycerol/water mixture with approximately 0% oxygen. The Foxy probe is allowed to measure the oxygen tension in the container for 30 minutes at 25°C. This is repeated for a series of different glycerol/water mixtures with known viscosities. The observed curves are fit to a double exponential and then plotted against viscosity to create a standard curve. The same method was applied to measure bovine and sheep lenses and compared to the standard curve to determine the viscosity.
The average bovine and sheep lens viscosity is 7.4 cP ±3.4 and 7.3 cP ±4.2, respectively, at 25°C. Based on the Stokes-Einstein equation, the diffusion coefficient of oxygen is 4.3 x 10-6 cm2/s.
The viscosity of the lens was successfully determined. The range can be attributed to the age of the animal. To date, the lens viscosity has been assumed to be 2 cP but this value is based on a highly concentrated lysozyme solution. Overall, the viscosity can help advance the understanding of the molecular transport within the lens. The diffusion coefficient of oxygen and other nutrients in the lens can now be accurately measured. These properties are essential to explain the metabolism of the lens.
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