Restoration of sight with subretinal photovoltaic arrays
Daniel Palanker
(Stanford University)
Date: March 9, 2017
Description:
Retinal degenerative diseases lead to blindness due to loss of the “image capturing” photoreceptors, while neurons in the “image-processing” inner retinal layers are relatively well preserved. Information can be reintroduced into the visual system using electrical stimulation of the surviving inner retinal neurons. Some electronic retinal prosthetic systems have been already approved for clinical use, but they provide low resolution and involve very difficult implantation procedures.
We developed a photovoltaic subretinal prosthesis which converts light into pulsed electric current, stimulating the nearby inner retinal neurons. Visual information is projected onto the retina by video goggles using pulsed near-infrared (~880nm) light. This design avoids the use of bulky electronics and wiring, thereby greatly reducing the surgical complexity. Optical activation of the photovoltaic pixels allows scaling the implants to thousands of electrodes, and multiple modules can be tiled under the retina to expand the visual field.
We found that similarly to normal vision, retinal response to prosthetic stimulation exhibits flicker fusion at high frequencies (>20 Hz), adaptation to static images, antagonistic center-surround organization and non-linear summation of subunits in the receptive fields, providing high spatial resolution. Photovoltaic arrays with 70m pixels restored visual acuity up to a single pixel width, which is only two times lower than natural acuity in rats. If these results translate to human retina, such implants could restore visual acuity up to 20/250. Higher resolution arrays (40m pixels), which are currently being tested, may provide acuity up to 20/130. Ease of implantation and tiling of these wireless modules to cover a large visual field, combined with high resolution opens the door to highly functional restoration of sight.
Created: Friday, March 10th, 2017