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Unraveling Ocular Tissue Biomechanics: Characterizing Collagen Microstructural Features and Introducing Direct Fiber Modeling

Ji, Fengting (2024) Unraveling Ocular Tissue Biomechanics: Characterizing Collagen Microstructural Features and Introducing Direct Fiber Modeling. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Glaucoma, a progressive optic neuropathy, is primarily associated with elevated intraocular pressure (IOP) and mechanical insult on ocular tissues. The optic nerve head (ONH) and lamina cribrosa (LC) are particularly vulnerable to early nerve damage, while the sclera surrounding the ONH, provides essential mechanical support and stability. Understanding the biomechanics of these ocular structures is crucial for unraveling the mechanisms of glaucoma.
The biomechanics of ONH, LC and sclera are intricately connected to their collagen microstructure, necessitating a comprehensive understanding of tissue microstructures and their associated biomechanical properties. However, despite extensive work, several microstructural characteristics have not been considered carefully, largely due to limitations in visualization tools. Furthermore, current modeling approaches in ocular biomechanics often neglect potentially critical fiber characteristics, limiting their ability to describe tissue structure and mechanics, particularly at fiber-level scales.
Using advanced imaging techniques like polarized light microscopy, this dissertation characterizes two critical microstructural features that have been ignored: LC insertions and the in-depth collagen fiber organization of corneoscleral shell. We characterized the spatial variations of LC insertions and variations of insertions among species. The discrete insertions of the LC beam indicate that the interaction between LC and the surrounding load-bearing tissue is discontinuous, leading to localized force concentrations. Diverse insertion shapes suggest varying robustness in the LC periphery, potentially influencing susceptibility to glaucomatous damage. We also present a detailed analysis of the in-depth organization of collagen fibers within the corneoscleral shell for a better characterization of the complex three-dimensional collagen architecture. This, in turn, will enhance the understanding of the out-of-plane tissue mechanical properties.
Leveraging detailed information available from the imaging, this project proposes and validates a novel direct fiber modeling approach that represents fibrous microstructure, accounting for fiber interweaving, interactions, and specimen-specific collagen architecture. The proposed model replicates anisotropic mechanical behavior observed in different loading protocols and across different samples, providing unprecedented details on fiber-level tissue behavior.
In conclusion, this dissertation uncovers crucial microstructural features of ocular tissue and introduces an innovative direct fiber modeling technique. The findings contribute to a deeper understanding of ocular tissue microstructure and biomechanics, advancing our knowledge of glaucoma pathogenesis.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Ji, Fengtingfej9@pitt.edufej9
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee MemberAbramowitch, Steven
Committee MemberDiLeo, Morgan
Committee MemberLathrop, Kira
Committee MemberRobertson, Anne
Committee ChairSigal, Ian
Date: 11 January 2024
Date Type: Publication
Defense Date: 24 August 2023
Approval Date: 11 January 2024
Submission Date: 24 October 2023
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 210
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Glaucoma, Biomechanics, Modeling, Collagen, Sclera, Lamina Cribrosa, Microstructure
Date Deposited: 11 Jan 2024 19:39
Last Modified: 11 Jan 2024 19:39


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