Zukünftige Entwicklungen bei implantierbaren Netzhautprothesen

Abstract

Implantable retinal prostheses for the blind are already in use. In blind subjects suffering from retinitis pigmentosa (RP), these systems are able to induce phosphenes. However, the measurable gain in vision is limited. This is due to degeneration in the retina itself and to the technology, which is used in the currently available systems. Research groups and companies are working on solutions and prototypes to improve the outcome of electrical stimulation in the visual system. One improvement will be to enlarge the electrode array in order to restore a larger visual field. A second approach is to enlarge the number of electrodes and to place them at a higher density to improve the spatial resolution of the system. A third concept is to develop a recording unit within the electrode array to analyse ganglion cell behaviour underneath the electrode. This information can than be used to optimise the stimulation pattern. Not only retinal prostheses are under development but also systems to stimulate the retina from the suprachoroidal space, to directly stimulate the optic nerve or the lateral geniculate body or even the primary visual cortex.

Development and in vitro validation of flexible intraretinal probes

“…To avoid bias in the insertion impact evaluations, only Si-60 and Pa-C-100 insertions with clear shank insertion and no holder impact were evaluated. 8,9,12 www.nature.com/scientificreports/ materials such as polyimide and parylene C, and the establishment of an intraretinal insertion model, allowed us to: (i) tailor the probes to the dimensions of the thin retina, (ii) predict the insertion feasibility of flexible intraretinal probes, and (iii) reduce the biological impact of intraretinal insertions. Even more, the reduction of the effective length of the shanks proved an alternative to the application of an insertion aid to successfully insert the flexible shanks into the neural tissue, an approach that can also benefit the insertion strategies of different neural implants, such as intracortical probes 13,38 .…”

“…To date, retinal implants have shown the restoration of useful vision in blind patients 5 . However, current retinal implants do not provide feedback on the ongoing retinal activity and the efficiency of the stimulation and do not adjust to the remodelling processes within the degenerated retina [6][7][8][9] . Thus, the development of penetrating silicon (Si) bidirectional microelectrode arrays (BiMEAs) for retinal applications has opened a new door to access different retinal layers, thereby allowing access to electrically stimulate the residual inner retina while monitoring not only the local field potentials (LFPs) and spontaneous spiking activity, but also the responses of the remaining retinal network to electrical and/or optical stimulation.…”

“…To further develop a bidirectional communication strategy using penetrating BiMEAs 8,9 in retinal applications, and given the stiffness of Si-based implants 10,11 , the goal of this work is to reduce and evaluate the acute biological impact of intraretinal devices. To this end, BiMEAs based on flexible materials were developed and tested for the first time in vitro in wildtype and degenerated mouse retinae.…”

Toward a Bidirectional Communication Between Retinal Cells and a Prosthetic Device – A Proof of Concept

“…With the aim to facilitate the improvement and adjustment of ES parameters in retinal implants and to provide means to examine in real-time the electrical activity within the retina, a bidirectional communication strategy between retinal cells and a prosthetic device using a penetrating MEA has been proposed (Heil et al, 2014; Brusius, 2015; Walter, 2016). In this way, the possibility for simultaneous recording and stimulation is opened.…”