期刊
JOURNAL OF BIOMECHANICS
卷 43, 期 9, 页码 1696-1701出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jbiomech.2010.02.031
关键词
Biaxial testing; Sclera; Stiffness; Tissue mechanical properties; Glaucoma
资金
- Collaborative Health Research Project Program
- Canadian Institutes of Health Research
- Canada Research Chairs Program
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(e(Q)-1), where Q = c(1)E(11)(2)+c(2)E(22)(2)+2c(3)E(11)E(22) and W, c's and E-ij are the strain energy function, material parameters and Green strains, respectively. Fitted material parameters were compared between samples. The parameter c(3) 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*c(1) and c*c(2), 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. (C) 2010 Elsevier Ltd. All rights reserved.
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