Elasticity of the lens capsule as measured by osmotic swelling.
2010-06
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Elasticity of the lens capsule as measured by osmotic swelling.
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2010-06
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Abstract
As an alternative to purely mechanical methods, optical tracking of passive osmotic
swelling was used to assess mechanical properties of the ocular lens capsule. Although
limited by being a single measurement on a heterogeneous tissue, osmotic swelling
provides a quantitative assessment of the stiffness of the lens capsule without requiring
dissection or manipulation of the lens. A simple model was developed accounting for the
permeability of the lens fiber cells and capsule to water, the concentration of fixed
charges in the fiber cells, and the capsuleās resistance to the swelling of fiber cells.
Fitting the model solution to experimental data provided an estimate of the elastic
modulus of the lens capsule under the assumption of linear isotropic elasticity. The
model was developed with the porcine lens to provide validity and was extended to a
mouse model with X-linked Alport Syndrome, the most common form of the human
disease that results in the absence of a collagen IV monomer normally present in the lens
capsule. The calculated elastic moduli for the porcine lens is comparable to previously
reported moduli of elasticity for the porcine lens capsule at small strains (<10%), and a
slight increase with hypotonicity is consistent with the nonlinear mechanical behavior of
the lens capsule. The calculated elastic moduli for the mouse lenses were similar between
wild type and Alport and are comparable to a reported modulus of elasticity for rat lens
capsules at small strains. The mouse lens modulus of elasticity showed a similar
response to bath concentrations as the porcine lenses, increasing with hypotonicity.
However, the difference in the tendency to rupture of the Alport and wild type lens
capsules were statistically significant; for lenses that reached 14% strain in the equatorial direction, the Alport lenses had a greater tendency to rupture. This work will be extended
to investigate the temporal effects of Alport syndrome on the elastic modulus and rupture
mechanics of lens capsules. Osmotic challenge overcomes the size limitations of
previously employed techniques for measuring the elastic modulus of the lens capsule
and can provide insight into the properties of basement membranes through its
application to other mutant mice.
Description
University of Minnesota M.S. thesis. June 2010. Major: Biomedical Engineering. Advisor: Victor Howard Barocas. 1 computer file (PDF); vii, 66 pages, appendices A-D. Ill. (some col.)
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Powell, Tracy A. (2010). Elasticity of the lens capsule as measured by osmotic swelling.. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/93310.
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