Sight can be restored in patients who lost photoreceptors due to atrophic AMD by substituting them with a photovoltaic array. Subretinal pixels convert pulsed NIR light projected from augmented-reality glasses into electric current, stimulating the nearby inner retinal neurons. Patients with such implants can simultaneously use their residual peripheral sight and central prosthetic vision, and its acuity closely matches the 100um pixel size of the implant. We present two approaches to selective neural stimulation with pixel sizes down to 20um – optically configurable current steering and 3-dimensional honeycomb-shaped electrodes, both providing prosthetic acuity matching the natural resolution in rats.
Photovoltaic retinal prosthesis is designed to restore sight in patients who lost central vision due to atrophic AMD. Subretinal pixels convert pulsed NIR light projected from augmented-reality glasses into electric current, stimulating the nearby inner retinal neurons. In patients with geographic atrophy, such prosthetic central vision coexists with natural peripheral sight, and its acuity closely matches the 100um pixel pitch of the implant. We present a progress toward 20um pixels based on honeycomb configuration of the stimulating arrays with return electrodes elevated on vertical walls, designed to leverage retinal migration for decoupling the stimulation threshold from pixel size.
Macular degeneration leads to blindness due to loss of the “image capturing” photoreceptors, while neurons in the “image-processing” inner retinal layers are relatively well preserved. Photovoltaic subretinal prosthesis converts light into pulsed electric current, stimulating the nearby inner retinal neurons. Clinical trial with such implants having 100um pixels, as well as preclinical measurements with 75 and 55um pixels, confirm that spatial resolution of prosthetic vision can reach the pixel pitch. For a broad acceptance of this technology, visual acuity should exceed 20/100, which requires pixels smaller than 25um. I will present 3-dimensional electro-neural interface scalable down to cellular-scale pixel size.
To restore vision in patients who lost photoreceptors due to retinal degeneration, we developed a photovoltaic subretinal prosthesis which converts light into pulsed electric current, stimulating the 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 and allows scaling the implants to thousands of electrodes.
We found that similarly to normal vision, retinal response to prosthetic stimulation exhibits flicker fusion at high frequencies (>20Hz), adaptation to static images, antagonistic center-surround receptive fields with non-linear summation of its subunits. In rats, photovoltaic arrays with 55um pixels provided grating visual acuity up to a pixel pitch, which corresponds to about 20/200 acuity in a human eye. In patients with geographic atrophy, implants with 100um pixels provided retinotopically correct pattern percepts with resolution matching the pixel size.
With flat pixels of 40um and smaller, stimulation thresholds are becoming prohibitively high. To reduce the pixel size further, we developed a novel honeycomb configuration of the stimulating electrode array with vertical walls separating the active and return electrodes, designed to leverage retinal migration for reducing the subretinal stimulation threshold and electrical cross-talk between neighboring pixels. Scalability, ease of implantation, and high resolution of these arrays open the door to highly functional restoration of sight in retinal degeneration.
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