کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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872966 | 910291 | 2010 | 6 صفحه PDF | دانلود رایگان |

The biomechanical environment of the optic nerve head (ONH), of interest in glaucoma, is strongly affected by the biomechanical properties of sclera. However, there is a paucity of information about the variation of scleral mechanical properties within eyes and between individuals. We thus used biaxial testing to measure scleral stiffness in human eyes. Ten eyes from 5 human donors (age 55.4±3.5 years; mean±SD) were obtained within 24 h of death. Square scleral samples (6 mm on a side) were cut from each ocular quadrant 3–9 mm from the ONH centre and were mechanically tested using a biaxial extensional tissue tester (BioTester 5000, CellScale Biomaterials Testing, Waterloo). Stress–strain data in the latitudinal (toward the poles) and longitudinal (circumferential) directions, here referred to as directions 1 and 2, were fit to the four-parameter Fung constitutive equation W=c(eQ−1), where Q=c1E112+c2E222+2c3E11E22 and W, c’s and Eij are the strain energy function, material parameters and Green strains, respectively. Fitted material parameters were compared between samples. The parameter c3 ranged from 10−7 to 10−8, but did not contribute significantly to the accuracy of the fitting and was thus fixed at 10−7. The products c⁎c1 and c⁎c2, measures of stiffness in the 1 and 2 directions, were 2.9±2.0 and 2.8±1.9 MPa, respectively, and were not significantly different (two-sided t-test; p=0.795). The level of anisotropy (ratio of stiffness in orthogonal directions) was 1.065±0.33. No statistically significant correlations between sample thickness and stiffness were found (correlation coefficients=−0.026 and −0.058 in directions 1 and 2, respectively). Human sclera showed heterogeneous, near-isotropic, nonlinear mechanical properties over the scale of our samples.
Journal: Journal of Biomechanics - Volume 43, Issue 9, 18 June 2010, Pages 1696–1701