Photovoltaic retinal prosthesis
Abstract/Contents
- Abstract
- Degenerative retinal diseases are among the leading causes of vision loss in the developed world. In these diseases, the "image capturing" photoreceptor layer slowly dies while the "image processing" inner retinal layers are preserved to large extent. One approach to restore vision of patients suffering from the selective photoreceptor loss is to deliver information to the visual system by patterned electrical stimulation of the remaining retinal circuitry. Several retinal prosthetic systems have achieved promising results in clinical studies, with the most successful prostheses allowing blind people to read large letters. However, the current retinal prosthetic designs require a trans-scleral cable to deliver power or data to the retinal stimulating array. We designed a photovoltaic prosthetic system with a silicon photodiode array placed behind the retina, in which each pixel of the array photovoltaically converts patterned pulsed near-infrared light projected from video goggles into pulses of bi-phasic electric current to stimulate the nearby retinal neurons. The light-powered 30-µm thick photodiode array does not require any wired power connections, which greatly simplifies the surgical procedure and reduces chances of infection. Several arrays could be juxtaposed to tile a larger area on the retina and thereby expand the visual field. The local return electrodes in each pixel help to reduce the spatial spread of electric current, thereby reducing the cross-talk between pixels and improving the spatial resolution of the implant. Each pixel contains three photodiodes connected in series to increase charge injection levels. Deep reactive-ion etched trenches are used to isolate the three photodiodes in each pixel. Trenches between the pixels are open to allow perfusion of nutrient, which is essential for in-vitro electrophysiological experiments, and may also help with the in-vivo integration of the implant with the retina. We fabricated 1 and 2 mm wide arrays of photodiode for implantation in small and large animals. Three sizes of pixels (280 µm, 140 µm and 70 µm) were fabricated to explore the resolution that could be achieved by the implant. The development of the fabrication process for the silicon photodiode array is presented, which involves eight mask layers, including deep isolation trench etch, n+ region predeposition, p+ region ion implantation, first via etching, first metal deposition and liftoff, second via etching, polysilicon etching in selected trenches, second metal deposition and liftoff. A detailed optoelectronic characterization of the fabricated photodiode array is also presented. The initial electrophysiological results of retinal stimulation in-vitro and in-vivo show that the fabricated devices are able to reliably elicit retinal responses at safe near-infrared light irradiances, with good acceptance of the photodiode array in the subretinal space.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Wang, Lele |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering |
| Primary advisor | Harris, J. S. (James Stewart), 1942- |
| Thesis advisor | Harris, J. S. (James Stewart), 1942- |
| Thesis advisor | Kamins, Theodore I |
| Thesis advisor | Palanker, Daniel |
| Advisor | Kamins, Theodore I |
| Advisor | Palanker, Daniel |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Lele Wang. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2012. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Lele Wang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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