A photovoltaic retinal implant

Degenerative retinal conditions, such as age-related macular degeneration, lead to the light-sensitive photoreceptor cells dying off, while the inner retinal neurons are relatively well preserved. Electrical stimulation of the surviving retinal neurons can elicit visual responses in patients. Here we are developing a photovoltaic implant chip that takes the place of the photoreceptors and receives power and the visual information wirelessly via IR pulses. The image on the right shows the concept, where a camera mounted on a set of glasses monitors the visual scene. This dynamic image is converted to pulses of patterned IR light and focussed onto the silicon implant. Individual pixels absorb the IR light and convert it to electrical stimulation pulses that activate inner retinal neurons.
The project is led by the Palanker Lab at Stanford University, who have produced an animation of the concept.

Photovoltaic Retinal Implant

a System concept: An optoelectronic chip replaces diseased photoreceptors. The visual information and power are transmitted via pulsed IR light patterns.

b Photovoltaic retinal implant: We fabricate 30 µm thin Si devices that can be implanted in the subretinal space and are stable for many years in vivo. Resolution is linked to the pixel size, which we are pushing down to 20 µm in pitch.

Current Research Focus

We are currently developing novel electrode interface structures to enhance the performance of the retinal implant and reduce the pixel size. The goal is to improve the restored visual acuity in patients to around 20/80.

3D electrodes for interfacing with the retina. We are investigating 3D structures that may be more efficient at interfacing with retinal neurons as they shape the E-field profile. A) Hexagonal electrode structures integrated on to a retinal prosthesis test device. B) Close-up of the hexagonal electrodes, designed to couple into the bipolar retinal neurons. C) Pillar electrodes that can penetrate into the inner nuclear layer of retinal neurons. D) Close-up of pillar structures.

Commercialisation

The technology is being commercialised by Pixium Vision (PRIMA system), who have conducted successful clinical trials. 

Recent Retinal Implant Publications

The Strathclyde funding for this research comes from the Royal Academy of Engineering through their Chair in Emerging Technology scheme.
The Rhona Reid Charitable Trust kindly helped fund a PhD studentship for Emma Butt.