The Role of the Eye's Peri-limbal Tissue and Integral Veins on Intraocular Pressure

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The mechanical properties of the eye tissues around the outer rim of the cornea (peri-limbal scleral tissue) contains veins that allow drainage from the clear jelly (aqueous humor) of the inside of the eye. The peri-limbal tissues are part of the mechanism that the eye uses to control eye pressure. This research will test whether the mechanical properties of the peri-limbal tissues changes how the veins control eye pressure. The research goals are to: (1) measure the deformation in the tissues supporting the veins as outflow occurs; (2) determine the relationships between peri-limbal tissue mechanical properties and deformation with the eye's intraocular pressure; (3) determine the mechanical mechanisms by which the peri-limbal scleral tissues influence the veins' ability to carry fluid from the eye. The objectives will be pursued through microscopic imaging of the deforming peri-limbal sclera of eyes under experimental perfusion. Fluorescent nanospheres in artificial aqueous infused into the eye will create trackable markers that will be used to measure deformation. A computer model of the fluid-structure interaction based on the experimental data will be created for the microstructural anatomy of the peri-limbal sclera and the included veins. Elevated eye pressure is often implicated in glaucoma and affects about 10% of the population over age 40, making it one of the leading causes of irreversible blindness. This research will further public health by discovering some of the basic causes of eye pressure increase in glaucoma. Capstone design projects and educational module for the principal investigators soft tissue class will be developed based on the research. More than six students will work on this interdisciplinary project, as well as two undergraduates for each year of the project. These students will come from engineering, natural science and medicine on the two University of Michigan campuses and neighboring institutions to expand the project's impact.The imaging will be conducted within the eye's tissues, not on the surface. This will produce new knowledge about the interaction of veins and the surrounding soft tissue as well as the transfer of intraocular pressure through the sclera and to the veins. Other than understanding that the aqueous venous system creates a back-pressure, little is known about the relationship between its structural details and outflow; such knowledge will be developed in this project. Knowledge will also result on the relationships between the viscoelastic tissue properties, strains and eye pressure. This knowledge has direct relevance to glaucoma in eyes having high pressure. Furthermore, because the viscoelastic tissue properties are strongly tied to components of the extracellular matrix and its remodeling, knowledge will occur that has application to aging and tissue disorders. The techniques and knowledge produced in normal peri-limbal sclera can be applied to diabetic tissues to better understand the differences in biomechanics and deformation in tissues with advanced glycation end products, a suspected cause of tissue stiffening. The methods used and knowledge gained will inform understanding of other tissues of the body where soft tissue and fluid acconveying vessels interact such as the renal tubules, cerebral veins, and retinal veins.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.