gms | German Medical Science

Artificial Vision 2024

The International Symposium on Visual Prosthetics

05. - 06.12.2024, Aachen, Germany

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A roadmap to in-vivo validation of intraretinal implants

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  • Viviana Rincón Montes - Institute of Biological Information Processing (IBI-3) - Bioelectronics, Forschungszentrum Jülich, Jülich
  • M. Jung - Institute of Biological Information Processing (IBI-3) - Bioelectronics, Forschungszentrum Jülich, Jülich; RWTH Aachen, Aachen
  • M. Kasavetov - Institute of Biological Information Processing (IBI-3) - Bioelectronics, Forschungszentrum Jülich, Jülich
  • N. Nruthyathi - Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich
  • F. Balcewicz - Department of Ophthalmology, University Hospital RWTH Aachen, Aachen
  • T. Lohmann - Department of Ophthalmology, University Hospital RWTH Aachen, Aachen
  • F. Müller - Institute of Biological Information Processing (IBI-1), Molecular and Cellular Physiology, Forschungszentrum Jülich, Jülich
  • P. Walter - Department of Ophthalmology, University Hospital RWTH Aachen, Aachen
  • A. Offenhäusser - Institute of Biological Information Processing (IBI-3) - Bioelectronics, Forschungszentrum Jülich, Jülich

Artificial Vision 2024. Aachen, 05.-06.12.2024. Düsseldorf: German Medical Science GMS Publishing House; 2025. Doc24artvis27

doi: 10.3205/24artvis27, urn:nbn:de:0183-24artvis275

Published: May 9, 2025

© 2025 Montes et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.

Outline

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Objective: To enhance the efficiency and specificity of visual prostheses that electrically stimulate the retina, our group has proposed the development of bidirectional microelectrode arrays for the simultaneous recording and stimulation from within the retina. A roadmap for a functional in vivo proof of concept of such strategy requires the development of tailored devices for intraretinal placement, functional in vitro testing, and the development of surgical strategies.

Materials and methods: We developed fully flexible parylene-C based three-dimensional (3D) penetrating and multisite microelectrode arrays, consisting of multiple penetrating shanks, each one containing three 15-µm diameter-recording electrodes and one 25-µm diameter-stimulating electrode. Both iridium oxide and PEDOT:PSS electrodes were tested. Functional testing was conducted in explanted rodent retinas in vitro, and surgical feasibility was assessed in rat cadavers.

Results: 3D intraretinal implants accurately placed in explanted retinas demonstrated bidirectional communication by enabling recording and stimulation at different intraretinal layers in vitro. PEDOT:PSS electrodes outperformed iridium oxide electrodes, delivering twice the charge. This allowed us to increase stimulation currents to 20 µA for 0.1 ms pulses and 1.6 µA for 5 ms pulses, enabling a broader range of neural responses and selective stimulation within the retina. Surgical feasibility for acute implantation was proven through open-sky surgery, confirmed by measuring the electrical resistivity profile across retinal layers in rodent cadavers.

Discussion: 3D intraretinal implants hold the potential to enhance the electrical stimulation capabilities of retinal prostheses. In vitro and cadaveric testing of these devices paves the way for upcoming in vivo functional testing of intraretinal implants.