DESCRIPTION (provided by applicant): Reduction of intraocular pressure (IOP) is currently the only effective treatment for glaucoma. However, most patients with elevated IOP do not develop glaucoma, and many patients with glaucoma do not have elevated IOP. The reason for this apparent discrepancy may be related to abnormalities in the biomechanical properties of the eye that predispose towards glaucoma. However, there is currently no available method for in vivo measurement of common ocular biomechanical properties including elasticity and viscosity. As a result, no previous studies have compared these properties in normal and glaucomatous human eyes of living subjects. In this study, we propose to assess ocular biomechanical properties by using a novel non-invasive technique termed ultrasound surface wave elastography (USWE). With this technique, a probe is used to create gentle vibrations in the tissue, and viscoelasticity is determined based on the speed of wave propagation. A unique advantage of USWE is that different tissue layers can be assessed, and viscosity can be calculated along with elasticity. Using this technique, we propose to assess the importance of ocular biomechanical properties in glaucoma. The project will be conducted in three specific aims. Specific Aim 1 (SA1): Develop a normative database of ocular elasticity and viscosity; SA2: Characterize ocular biomechanical properties in newly diagnosed glaucoma patients and compare with normal controls; SA3: Refine the technique in order to optimize its ability to capture ocular data. Characterization of in vivo ocular biomechanical properties is critical to understanding glaucoma pathogenesis. As well, the development of a novel method for measuring elasticity and viscosity in different ocular tissues would enable new avenues of research into other ocular conditions that may be affected by tissue biomechanics. Further, this technology could potentially provide a new diagnostic tool for patient care. The information obtained in this project will be an important step in achieving the long-term goals of enhancing understanding of glaucoma risk, improving patient management, and the development of novel therapies.

PUBLIC HEALTH RELEVANCE: Glaucoma is a significant public health issue, affecting over 2.5 million people in the United States alone, and is the second most common cause of blindness in the United States and worldwide. The only treatment for glaucoma at this time is reduction of intraocular pressure (IOP). However, most patients with high IOP do not develop glaucoma, and up to half of patients with glaucoma have IOP in the normal range. The biomechanical properties of the eye may help explain this apparent discrepancy. This project will use a novel technique to non-invasively compare ocular biomechanics in normal subjects and glaucoma patients, and further develop the technology to enable investigation of other eye diseases.