GSC Webinar, Vicky Nguyen, Biomechanics of the Tissues of the Eye Wall and Applications to Glaucoma

Professor Vicky Nguyen, Marlin U. Zimmerman Jr. Faculty Scholar, Department of Mechanical Engineering, Johns Hopkins University
Title: Biomechanics of the Tissues of the Eye Wall and Applications to Glaucoma

Abstract
The sclera and optic nerve head, along with the cornea, are connective tissues that form the outer wall of the eye in humans. These stiff and tough tissues serve to mechanically support the delicate retinal and neural tissues of the eye while maintaining an optimal shape for refraction. The mechanical properties of the sclera arise from the fiber-reinforced microstructure of the extracellular matrix, which is composed mainly of collagen and elastin fibers arranged in a proteoglycan-rich matrix. The extracelullar matrix structure in the human optic nerve head is called the lamina cribrosa for its fenestrated appearance. The lamina cribrosa is composed of a stack of perforated plates that resemble a collagen beam network structure when viewed en face. The collagen beams support a network astrocytes and axons of the retinal ganglion cells as they exit the eye. Variations in the mechanical properties of the lamina cribrosa, sclera and cornea may contribute to the susceptibility and progression of glaucoma.
In this presentation, I will describe our efforts to understand the structure-properties relationship of the sclera and optic nerve head tissues of human eyes using an integrated experimental and computational method. To measure the mechanical behavior of the tissues under physiological conditions, we have developed ex-vivo inflation tests with optical imaging and 3D digital image correlation (3D-DIC). We also developed methods to measure the anisotropy of the collagen microstructure of the sclera and the beam network microstructure of the lamina tissue of our inflation tested specimens. This has allowed us to develop specimen specific computational models to study the structure-properties relationship of these tissues and extract their anisotropic nonlinear elastic properties using inverse analysis. Recent advances have focused on developing mechanical tests for in vivo measurements of the strain response of the optic nerve head tissues in glaucoma patients and non-glaucoma subjects.
Biography
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 and The Marlin U. Zimmerman Faculty Scholar 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. Dr. Nguyen has received the 2008 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 received the 2013 NSF CAREER award and 2016 JHU Catalyst Award to study the micromechanisms of growth and remodeling of collagenous tissues. She was also awarded 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 in 2013, and the T.J.R. Hughes Young Investigator Award from the Applied Mechanics Division in 2015. She is currently serves as an Associate Editor for the Journal of Biomechanical Engineering and is the 2020 President of the Society of Engineering Science.