Three-dimensional electrode arrays for retinal prostheses: modeling, geometry optimization and experimental validation

Abstract

Three-dimensional electrode geometries were proposed to increase the spatial resolution in retinal prostheses aiming at restoring vision in blind patients. We report here the results from a study in which finite-element modeling was used to design and optimize three-dimensional electrode geometries. Proposed implants exhibit an array of well-like shapes containing stimulating electrodes at their bottom, while the common return grid electrode surrounds each well on the implant top surface. Extending stimulating electrodes and/or the grid return electrode on the walls of the cavities was also considered. The goal of the optimization was to find model parameters that maximize the focalization of electrical stimulation, and therefore the spatial resolution of the electrode array. The results showed that electrode geometries with a well depth of 30 µm yield a tenfold increase in selectivity compared to the planar structures of similar electrode dimensions. Electrode array prototypes were microfabricated and implanted in dystrophic rats to determine if the tissue would behave as hypothesized in the model. Histological examination showed that retinal bipolar cells integrate the electrode well, creating isolated cell clusters. The modeling analysis showed that the stimulation current is confounded within the electrode well, leading to selective electrical stimulation of the individual bipolar cell clusters and thereby to electrode arrays with higher spatial resolution.

Age-related changes in dynamic moduli of ovine vitreous

“…Finite element (FE) analysis is a valuable computational tool that provides insight into the responses of an eye during trauma. Many FE models exist for investigating ocular injury and pathologies of the adult eye (Amini et al, 2011;Djilas et al, 2011;Girard et al, 2011;Kasi et al, 2011;Nguyen and Boyce, 2011;Opie et al, 2010;Power et al, 2002;Rossi et al, 2011;Roy and Dupps, 2011;Sigal, 2011;Uchio et al, 2004Uchio et al, , 1999Weaver et al, 2011;Yang et al, 2009), but only two FE models exist for pediatric ocular research (Hans et al, 2009;Rangarajan et al, 2009). Both of these models utilize adult material properties, many of which were tested at quasistatic rates, and are likely to be a misrepresentation of the pediatric ocular mechanical response to trauma.…”

Electronic restoration of vision in those with photoreceptor degenerations

“…22 Designing an implant that uses less current to elicit a response is important as high current injection could be problematic in terms of tissue heating and damage over time. To address this distance issue some groups are testing devices with spine electrodes that penetrate into the retina 74,[87][88][89][90] This technique may be most useful for implants placed in the subretinal, suprachoroidal or episcleral space, so that they can deliver enough current to stimulate the ganglion cells. Manufacturing capability will be a determining factor for the development of electrodes that penetrate into the retina, as these electrodes would need to be much smaller (tips approximately one to 10 mm © 2012 The Authors in diameter) than currently available surface electrodes (100 to 400 mm).…”

Image Analysis for Automatically-Driven Bionic Eye

“…In France, at the Institut de la Vision, the team of Pr Picaud has developed a subretinal implant [Djilas (2011)]. They have also set up clinical trials.…”