Visual prostheses based on electrical stimulation of the retina are an effective approach for treating blindness in individuals with photoreceptor degenerative diseases (e.g., retinitis pigmentosa). The epiretinal strategy, which was pioneered by our team, involves implanting the stimulating electrodes near the inner retinal surface. Compared with other strategies, epiretinal implantation surgeries are easier and are at risk of fewer complications. Epiretinal stimulation electrodes consist of metallic micro-disks of platinum, iridium, or titanium and their oxides, embedded in a flexible insulating polymer substrate such as polyimide, parylene, or silicone elastomer. The electrode array can be monitored with funduscopy and removed or readjusted post-implantation with minimal surgery. Our experience with chronic implantation suggests that mechanical damage to the retina is a significant concern for epiretinal prosthesis patients with electrical stimulation. Furthermore, preclinical studies hae shown that prolonged electrical stimulation can damage the retina. However, detailed knowledge of how this damage manifests in retinal implant patients is currently lacking. Ocular imaging technologies available in the clinic, such as optical coherence tomography (OCT), are useful for patient monitoring but provide only limited information about retinal structure. Thus, there is a need for novel imaging modalities that can measure the fundamental mechanical properties of the retina over time in retinal prosthesis patients. The goal of this study is to develop and characterize novel tools for imaging the elastic properties of the retina under prosthetic electrical stimulation. To address this goal, we propose to use phase-resolved OCT to detect minute displacements induced by acoustic radiation force (ARF) in the retinal tissue layers. This will enable us to generate images depicting local displacements with nanometer resolution, providing details about the elastic properties of the retina that cannot be obtained with current imaging methods. We will also develop ultrasound (US) convex transducer arrays that can monitor retinal detachment and edema through the thin stimulating electrodes in areas where tissue damage is most likely to occur. We'll design and develop two convex single crystal arrays for imaging and an ARF transducer and integrated convex array ARF-optical coherence elastography (OCE) system that enables co-registered OCT, US, and ARF- OCE imaging; Model and measure the elastic properties of the retina with electrode array and conduct ex-vivo and in-vivo rabbit eye imaging to assess performance. Use ARF-OCE to detect retinal damage caused by mechanical stress and electrical stimulation.
Despite significant advance in medicine, retinal prosthesis is very important to help blind people. We propose to use phase-resolved OCT to detect minute displacements induced by acoustic radiation force (ARF) in the retinal tissue layers. This will enable us to generate images depicting local displacements with nanometer resolution, providing details about the elastic properties of the retina that cannot be obtained with current imaging methods. We will also develop ultrasound (US) convex transducer arrays that can monitor retinal detachment and edema through the thin stimulating electrodes in areas where tissue damage is most likely to occur. The proposed technology can potentially provide such a clinical tool.
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