gms | German Medical Science

Objective: To investigate a wearable non-invasive retina stimulation methods using printed dry electrodes: First to test the efficacy of dry skin electrodes to evoke phosphenes (human), and second, to explore the potential of temporal interference (TI) for localized retina activation (chick).

Materials and Methods: Non-invasive retina stimulation was performed using both wet and dry skin electrodes to evoke phosphenes. Phosphene localization protocols are developed and tested to improve stimulation precision. Ex vivo experiments involving retina activation from a distance of several hundred microns, as well as stimulation using TI are performed. Retinal responses are measured and analyzed across varying stimulation parameters to evaluate effectiveness and potential adverse effects.

Results: Non-invasive stimulation with dry electrodes demonstrated equivalent efficacy to wet electrodes in evoking phosphenes. Ongoing work aims to optimize phosphene localization protocols for improved spatial accuracy. In contrast, ex vivo TI stimulation failed to induce direct retinal activation. Prolonged TI exposure resulted in reduced retinal sensitivity to subsequent stimulation, suggesting potential inhibitory effects.

Discussion: These findings indicate that non-invasive dry electrode stimulation is a viable alternative to wet electrodes for retinal stimulation, with further development needed for phosphene localization. The application of TI for remote retinal activation remains challenging. Ongoing research focuses on refining stimulation protocols and exploring alternative approaches to precise retinal activation.