Honeycomb-shaped electro-neural interface enables cellular-scale pixels in subretinal prosthesis

Thomas Flores,Roopa Dalal,Daniel Palanker,Elton Ho,Ludwig Galambos,Zhijie Chen,Theodore Kamins,Keith Mathieson,Tiffany Huang,Mohajeet Bhuckory

doi:10.1038/s41598-019-47082-y

Thomas Flores, Roopa Dalal + Show 8 more

Open Access

https://doi.org/10.1038/s41598-019-47082-y

Copy DOI

Journal: Scientific Reports	Publication Date: Jul 23, 2019
Citations: 53	License type: open-access

Affiliation: Stanford University, University of Strathclyde

Abstract

High-resolution visual prostheses require small, densely packed pixels, but limited penetration depth of the electric field formed by a planar electrode array constrains such miniaturization. We present a novel honeycomb configuration of an electrode array with vertically separated active and return electrodes designed to leverage migration of retinal cells into voids in the subretinal space. Insulating walls surrounding each pixel decouple the field penetration depth from the pixel width by aligning the electric field vertically, enabling a decrease of the pixel size down to cellular dimensions. We demonstrate that inner retinal cells migrate into the 25 μm deep honeycomb wells as narrow as 18 μm, resulting in more than half of these cells residing within the electrode cavities. Immune response to honeycombs is comparable to that with planar arrays. Modeled stimulation threshold current density with honeycombs does not increase substantially with reduced pixel size, unlike quadratic increase with planar arrays. This 3-D electrode configuration may enable functional restoration of central vision with acuity better than 20/100 for millions of patients suffering from age-related macular degeneration.

Highlights

Visual acuity of 20/200, the limit of legal blindness in the United States, geometrically corresponds to a pixel pitch of about 50 μm[6]
Our results indicate that such technology opens the door to prosthetic vision with acuity better than 20/100, which would be highly beneficial for patients completely blinded by RP, and for restoration of central vision in the much larger population of patients with AMD
Our study provides a path toward improvement in spatial resolution of retinal prostheses far beyond the limits of the current systems

Summary

Introduction

Visual acuity of 20/200, the limit of legal blindness in the United States, geometrically corresponds to a pixel pitch of about 50 μm[6]. Cross-talk between neighboring electrodes increases with decreasing pixel size[6] The latter issue can be addressed by providing a circumferential return electrode in each pixel[6] or utilizing sequential activation with current steering techniques to shape the electric field[7]. We present a novel 3-D geometry for a subretinal prosthesis, which we call the honeycomb configuration, to overcome these limitations and enable scaling the pixels down to cellular dimensions In this approach, return electrodes are elevated on vertical insulating walls surrounding each pixel (Fig. 1), which align the electric field vertically, matching the orientation of bipolar cells in the retina, and thereby reducing the stimulation threshold. Our results indicate that such technology opens the door to prosthetic vision with acuity better than 20/100, which would be highly beneficial for patients completely blinded by RP, and for restoration of central vision in the much larger population of patients with AMD

Methods

Results

Conclusion