Machelle Pardue, Ph.D. (Georgia Institute of Technology)
C. Ross Ethier, Ph.D. (Georgia Institute of Technology)
Brandon Dixon, Ph.D. (Georgia Institute of Technology)
Wilbur Lam, Ph.D. (Georgia Institute of Technology)
Rafael Grytz, Ph.D. (University of Alabama at Birmingham)
Biomechanics and Biochemistry of the Myopic Mouse Sclera
Most cases of human myopia, colloquially known as “nearsightedness”, are due to an excessive axial elongation of the eye that disrupts its balance of geometry and optics. Previous research has implicated the sclera (the white part of the eye) as the main determinant of overall eye shape and size through its role in mechanically resisting the imposed tensile stresses from the persistent and fluctuating intraocular pressure. It is widely accepted that visual cues guide changes in scleral composition, structure, and biomechanics through the development of most mammalian myopia. Importantly, the ultrastructure of collagen, the main tension-bearing biological molecule, has been observed to remain largely unchanged until after the eye has already elongated, which raises questions about how visual cues are being transmitted to the sclera and what structural molecules are changing to facilitate axial elongation. Altered dynamics of the charge-dense proteoglycan aggrecan have been observed in eyes developing myopia, but how this contributes to biomechanics, eye geometry, and myopia progression is not known. To explore aspects of these questions, I will be utilizing the mouse model. My first aim will address the applicability of compression testing and the application of a poroelastic material model to determine compressive, tensile, and hydraulic properties in the very small and thin mouse sclera, whose size precludes most standard biomechanical tests. With this methodology established, my second aim will focus on characterizing biomechanical and biochemical changes to the sclera through the development of myopia. In my third aim, I will use previously established methods to probe a mechanistic question about a potential signaling molecule, retinoic acid, and how it alters scleral composition and biomechanics.