Retinal electrostimulation is promising a successful therapy to restore functional vision. However, a narrow stimulating current range exists between retinal neuron excitation and inhibition which may lead to misperformance of visual prostheses. As the conveyance of representation of complex visual scenes may require neighbouring electrodes to be activated simultaneously, electric field summati...

PURPOSE To evaluate the contrast sensitivity of a degenerate retina stimulated by a photovoltaic subretinal prosthesis, and assess the impact of low contrast sensitivity on transmission of visual information. METHODS We measure ex vivo the full-field contrast sensitivity of healthy rat retina stimulated with white light, and the contrast sensitivity of degenerate rat retina stimulated with a ...

Purpose: To evaluate the contrast sensitivity of a degenerate retina stimulated by a photovoltaic 12 subretinal prosthesis, and assess the impact of low contrast sensitivity on transmission of visual 13 information. Methods: We measure ex-vivo the full-field contrast sensitivity of healthy rat retina stimulated with 15 white light, and the contrast sensitivity of degenerate rat retina stimulate...

Wireless powering of a retinal prosthesis is necessary for continuous operation of the implanted device in a blind patient. Inductive link has the potential for transferring power wirelessly to such an implanted device inside the eye. However, constant motion of the eye and changes in electrode-tissue impedance results in a decrease in the inductive link efficiency. In this paper, we present a ...

For successful visual perception by visual prosthesis using electrical stimulation, it is essential to develop an effective stimulation strategy based on understanding of retinal ganglion cell (RGC) responses to electrical stimulation. We studied RGC responses to repetitive electrical stimulation pulses to develop a stimulation strategy using stimulation pulse frequency modulation. Retinal patc...

Natural vision relies on spatiotemporal patterns of electrical activity in the retina. We investigated the feasibility of veridically reproducing such patterns with epiretinal prostheses. Multielectrode recordings and visual and electrical stimulation were performed on populations of identified ganglion cells in isolated peripheral primate retina. Electrical stimulation patterns were designed t...

Retinal prostheses are promising tools for recovering visual functions in blind patients but, unfortunately, with still poor gains in visual acuity. Improving their resolution is thus a key challenge that warrants understanding its origin through appropriate animal models. Here, we provide a systematic comparison between visual and prosthetic activations of the rat primary visual cortex (V1). W...

By a retinal prosthesis, the researchers have been able to stimulate a limited number of neurons (around 100) by biphasic current stimulus to reproduce an image spatially by multiplexing technique. For functional restoration of sight (visual acuity 20/80), we are to stimulate at least 2500 neurons/mm². We are far behind that target. The time required by biphasic current stimulus, the sequential...

This paper presents a highly flexible and complete 256-electrode retinal prosthesis chip, which is small and ready for packaging and implantation. The chip contains 256 separate programmable drivers each of which is dedicated to its own electrode for flexible stimulation. The stimulator possesses a wide range of stimulation features, supporting various stimulation strategies. Many safety featur...

Long-term success of an implantable retinal prosthesis depends on the ability to hermetically seal sensitive electronics from a saline environment with an encapsulant material. Furthermore, the retinal implant project's proposed laser-driven prosthesis requires that the encapsulation material be transparent. The device itself has two components that must protrude out of the encapsulation materi...