Subretinal electronic chips allow blind patients to read letters and combine them to words

Abstract

A light-sensitive, externally powered microchip was surgically implanted subretinally near the macular region of volunteers blind from hereditary retinal dystrophy. The implant contains an array of 1500 active microphotodiodes (‘chip’), each with its own amplifier and local stimulation electrode. At the implant's tip, another array of 16 wire-connected electrodes allows light-independent direct stimulation and testing of the neuron–electrode interface. Visual scenes are projected naturally through the eye's lens onto the chip under the transparent retina. The chip generates a corresponding pattern of 38 × 40 pixels, each releasing light-intensity-dependent electric stimulation pulses. Subsequently, three previously blind persons could locate bright objects on a dark table, two of whom could discern grating patterns. One of these patients was able to correctly describe and name objects like a fork or knife on a table, geometric patterns, different kinds of fruit and discern shades of grey with only 15 per cent contrast. Without a training period, the regained visual functions enabled him to localize and approach persons in a room freely and to read large letters as complete words after several years of blindness. These results demonstrate for the first time that subretinal micro-electrode arrays with 1500 photodiodes can create detailed meaningful visual perception in previously blind individuals.

Optogenetic therapy for retinitis pigmentosa

“…Patients who are legally blind are the key target population of these therapies. Three different strategies are being investigated: (1) the implantation of differentiated or undifferentiated photoreceptors, 19 (2) electronic retinal implants, [20][21][22] and (3) the subject of this review, so-called 'optogenetic' approaches, [23][24][25] which use genetically encoded light sensors to make cells light responsive. [26][27][28] The success of cellimplantation approaches depends on the formation of functional synapses between the implanted photoreceptors and endogenous bipolar cells, and on functional retinal pigment epithelium to supply photoreceptors with 11-cis-retinal.…”

“…Some blind patients can read letters and even words. 22 In optogenetic approaches, a genetically encoded light sensor sits in the membrane of a retinal cell. The generated current flows across the cell membrane and thus activates or inactivates that particular cell.…”

Neural Activation for Different Electrode Designs in Subretinal Implants: a Modeling Study

“…1C) which replaces the vitreous body in retinal implant patients after vitrectomy [4]. The distant return electrode used in the retinal implant [5] was simulated by setting the outer boundary conditions of the retinal layer to ground potential (Fig. 1D) [6].…”

Stem Cells as Tools for Studying the Genetics of Inherited Retinal Degenerations

“…In contrast to traditional gene therapy approaches whose goal is to correct a mutated gene and restore normal protein function, optogenetics introduces novel light sensitive proteins into neurons like bipolar cells and ganglion cells to cause them to function as photoreceptors to restore some visual function (Garg and Federman 2013;Packer et al 2013;Yonehara et al 2013). Retinal prostheses typically consist of arrays of photodiodes that are surgically implanted beneath or above the retina to electrically stimulate the remaining inner retinal cells (Loudin et al 2007;Zrenner et al 2011). Another strategy that is being pursued for patients with very advanced disease is a three-dimensional transplants consisting of stem-cell-derived sheets of photoreceptors and RPE cells grown on a biocompatible polymer scaffold (Zhang et al 2007;Yao et al 2011;Tucker et al 2011a;Shepherd et al 2013).…”