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D. S. Schultz, J. M. Stewart; Structural Factors Mediating Scleral Stiffness. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4420.
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To quantify structurally relevant constituents within sclera and determine their impact on mechanical stiffness.
Posterior strips approximately 6 mm by 25 mm were harvested from 20 pig and 20 human eyes and stored frozen (-20 °C). Mechanical stiffness was determined via quasi-static uniaxial tensile tests by calculating the tangent modulus at a prescribed near-physiologic stress (0.8MPa). Adjacent globe tissue was apportioned for each of five assays: pepsin soluble collagen, acid soluble collagen, soluble crosslink density, elastin content and glycosaminoglycan content.
Preliminary results for porcine sclera (n=6) indicate stiffness values of 47.0 MPa (stdev = 10.7 MPa), water content of 68.0% (stdev = 1.9%) and soluble collagen content of 37.9% (stdev = 9.7%). It is expected that variance in stiffness values will be dependent on collagen content and crosslink density. In contrast, water and glycosaminoglycan content are unlikely to influence a quasi-static measure of stiffness. An analysis of variance will be used to determine the dependence of stiffness on each tissue constituent.
Variation in collagen content and crosslink density will likely have a statistically significant impact on the variation in mechanical stiffness. Elastin is likely to have a lesser role influencing stiffness, while water content and glycosaminoglycan content are expected to be statistically insignificant factors.
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