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M. Girard, J.–K.F. Suh, R.T. Hart, C.F. Burgoyne, J.C. Downs; Effects of Storage Time on The Mechanical Properties of Rabbit Peripapillery Sclera after Enucleation . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2177.
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Purpose: Following enucleation, human donor eyes are typically stored in phosphate buffered saline (PBS) solution before they are released for research. An unknown factor in biomechanics research of the human eye is the effect of post–enucleation storage time on the material properties of ocular tissues. In this study, we tested the effect of storage time on the biomechanical properties of the sclera from NZW rabbit eyes. Methods: Twelve rabbits were sacrificed and their eyes storad at 4 °C in PBS solution immediately after enucleation. The eyes were randomly divided into six groups based on post–enucleation storage times of 3, 8, 24, 36, 48 and 72 hours. A tensile specimen (gage length of 8 mm, gage width of 3 mm, and an average thickness of 750 µm) was prepared from the inferior quadrant of the sclera near the optic nerve of each eye, and was subjected to uniaxial preconditioning in tension (1 % strain at a stain rate of 1 %/sec for 10 cycles), followed by a stress relaxation test (1 %/sec strain ramp to 1% strain with the displacement held for 1000 sec). Each specimen was tested in an environment chamber maintained at 37 °C and 100% humidity, and an extensometer was used to accurately measure the strain in the sample. The data were then analyzed using linear viscoelastic theory based on a relaxation spectrum with a Gaussian distribution function. From the experimental data, four viscoelastic material property parameters (Eo and E<font face="symbol">¥</font>, the instantaneous and equilibrium moduli; τm, the mean relaxation time constant; ß, the logarithmic bandwidth of relaxation spectrum distribution) were determined by a nonlinear least squares regression analysis using a genetic optimization algorithm. Results and Conclusions: No statistically significant differences were found in the mechanical properties of each group, which showed that the samples did not undergo systemic degradation of material properties for storage times up to 72 hours. This data suggests that donor eyes can be stored up to three days at 4 °C in PBS without risking biomechanical deterioration of the ocular tissues.
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