title: The role of 3-D collagen organization in stromal elasticity: a model based on X-ray diffraction data and second harmonic-generated images.
abstract: Examining the cross-section of the human cornea with second harmonic-generated (SHG) imaging shows that many lamellae do not lie parallel to the cornea's anterior surface but have inclined trajectories that take them through the corneal thickness with a depth-dependent distribution. A continuum mechanics-based model of stromal elasticity is developed based on orientation information extracted and synthesized from both X-ray scattering studies and SHG imaging. The model describes the effects of inclined lamella orientation by introducing a probability function that varies with depth through the stroma, which characterizes the range and distribution of lamellae at inclined angles. When combined with the preferred lamellar orientations found from X-ray scattering experiments, a fully 3-D representation of lamella orientation is achieved. Stromal elasticity is calculated by a weighted average of individual lamella properties based on the spatially varying 3-D orientation distribution. The model is calibrated with in vitro torsional shear experiments and in vivo indentation data and then validated with an in vitro inflation study. A quantitative explanation of the experimentally measured depth dependence of mechanical properties emerges from the model. The significance of the 3-D lamella orientation in the mechanics of the human cornea is demonstrated by investigating and contrasting the effects of previous modeling assumptions made on lamella orientation.
authors.affiliation: Department of Mechanical Engineering, Stanford University, 226 Durand Building, 496 Lomita Mall, Stanford, CA, 94305, USA, petsche@stanford.edu.
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Petsche
authors.forename: Peter M
authors.initials: PM
authors.lastname: Pinsky
mesh_terms: D003094:Collagen / Q000378:metabolism*; D003319:Corneal Stroma / Q000502:physiology* / Q000648:ultrastructure; D004548:Elasticity; D006801:Humans; D021621:Imaging, Three-Dimensional; D008954:Models, Biological; D011509:Proteoglycans / Q000378:metabolism; D033081:Shear Strength; D054159:Torsion, Mechanical; D014961:X-Ray Diffraction
chemical_list: D011509:Proteoglycans; D003094:Collagen