Photovoltaic subretinal prosthesis for high visual acuity : design, fabrication, and in vivo assessment
Abstract/Contents
- Abstract
- Retinal degenerative diseases, such as atrophic age-related macular degeneration (AMD), are the leading cause of incurable blindness due to the irreversible loss of photoreceptors. Photovoltaic subretinal prostheses have shown promise in restoring vision by electrically stimulating the second- order retinal neurons, specifically the bipolar cells. Clinical trials in AMD patients have demonstrated prosthetic vision with an acuity of up to 20/438, closely matching the 100 μm pixel size of the implant. To further improve and broaden the adoption of this technology, pixel sizes need to be reduced to below 50 μm, surpassing the US legal blindness threshold of 20/200. However, scaling down the pixels of the current design to below 75 μm in patients is not feasible, as the local return electrodes excessively confine the electric field, precluding the stimulation of bipolar cells within a safe charge injection range. In this thesis, I present two alternative pixel design strategies aimed at optimally shaping the electric field with smaller pixels. The objective is to enable effective stimulation of retinal neurons without compromising safety, contrast, or resolution. The first strategy involves a monopolar pixel array with current steering, replacing the circumferential local return electrodes in each pixel with a transient return path through neighboring dark pixels. This design allows for deeper field penetration while maintaining high spatial contrast. The second strategy employs 3-dimensional electrodes, such as honeycomb-shaped walls and pillars, to vertically shape the electric field. Anatomical and electrophysiological studies of these 3D arrays in vivo demonstrate their feasibility and long-term biocompatibility. Grating acuity tests with these new implants - planar and 3D - in blind rats have shown that the prosthetic acuity matches the sensor pitch with 40 μm pixels, while with 20 μm pixels, prosthetic acuity reaches the 28 μm limit of natural resolution in rats. Unlike stimulation mediated by bipolar cells, direct activation of third-order neurons, the ganglion cells, by subretinal implants does not yield high spatial resolution. Therefore, an electric field that is carefully optimized for effective and selective stimulation of bipolar cells is crucial for achieving a high visual acuity of up to 20/80 in AMD patients.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2023; ©2023 |
| Publication date | 2023; 2023 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Wang, Bingyi, (Physics researcher) |
|---|---|
| Degree supervisor | Chu, Steven |
| Degree supervisor | Palanker, Daniel |
| Thesis advisor | Chu, Steven |
| Thesis advisor | Palanker, Daniel |
| Thesis advisor | Hong, Guosong |
| Thesis advisor | Kamins, Theodore I |
| Degree committee member | Hong, Guosong |
| Degree committee member | Kamins, Theodore I |
| Associated with | Stanford University, School of Humanities and Sciences |
| Associated with | Stanford University, Department of Physics |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Bingyi Wang. |
|---|---|
| Note | Submitted to the Department of Physics. |
| Thesis | Thesis Ph.D. Stanford University 2023. |
| Location | https://purl.stanford.edu/dd285nh9182 |
Access conditions
- Copyright
- © 2023 by Bingyi Wang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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