The biomechanics of the human posterior sclera and lamina cribrosa in glaucoma
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Wednesday, October 7, 2015 - 1:30pm to 3:00pm
Dr. Thao D. (Vicky) Nguyen, Johns Hopkins University
Glaucoma is characterized by damage to the retinal ganglion cell axons in the optic nerve head. The intraocular pressure (IOP) and age are among the most important risk factors for glaucoma. The incidence of glaucoma increases exponentially with age and those with glaucoma have on average higher IOP than those who don't. Lowering IOP is the only proven strategy to slow the progression of glaucoma damage. From a biomechanics point of view, IOP acts a mechanical loading to the tissues of the optic nerve head. How much stress and strain develop in the optic nerve head is determined by the mechanical properties of the connective tissues of the optic nerve head, namely the lamina cribrosa, and the peripapillary sclera. This could explain why some people with normal IOP have glaucoma while those who have very high IOP don't. Thus it is important to role of the biomechanics of the lamina cribrosa and sclera in the pathophysiology of glaucoma. In this presentation, I will describe our efforts to understand the structure-function relationship of the human sclera and lamina cribrosa and how they change with age and may be changed by glaucoma. For the sclera, we developed methods to map the deformation response of the sclera to controlled pressurization and also to map the collagen structure of the tissue. We then developed finite element models of the inflation-tested specimens, where we incorporated both the digitally reconstructed specimen-specific geometry and collagen structure, and applied inverse methods to evaluate mechanical properties of the tissues of different ages and degree of axonal damage. We are currently developing a similar approach to study the structure-function of the lamina cribrosa. I will present our most recent work to develop an inflation test to map the local deformation response and collagen structure of the tissue.
Thao (Vicky) Nguyen received her S.B. from MIT in 1998, and M.S. and Ph.D. from Stanford in 2004, all in mechanical engineering. She was a research scientist at Sandia National Laboratories in Livermore from 2004-2007, before joining the Mechanical Engineering Department at The Johns Hopkins University, where she is currently a tenured Associate Professor in the Departments of Mechanical Engineering and Materials Science. Dr. Nguyen’s research encompasses the biomechanics of soft tissues and the mechanics of active polymers and biomaterials. Her work in biomechanics integrates the development of novel experimental methods and microstructure-based theoretical and computational models to study the structure, property, and function of ocular tissues and other soft collagenous tissues, as well as the mechanisms for growth and remodeling under physiological and pathological conditions. In 2008, Dr. Nguyen received the Presidential Early Career Award for Scientists and Engineers (PECASE) and the NNSA Office of Defense Programs Early Career Scientists and Engineer Awards for her work on modeling the thermomechanical behavior of shape memory polymers. She was also awared an NSF CAREER award to study the micromechanisms of growth and remodeling of collagenous tissues, the inaugural Eshelby Mechanics Award for Young Faculty for the creative development and applications of mechanics, and the ASME Sia Nemat-Nasser Early Career Award for research excellence in mechanics and materials, all in 2013, and the T.J.R. Hughes Young Investigator Award from the Applied Mechanics Division of ASME in 2015.