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Charge recovery during concurrent stimulation for a vision prosthesis
M Mohd Addi1, S Dokos, P J Preston
1Graduate School of Biomedical Engineering, University of New South Wales, Sydney, 2052, Australia.
Summary
Concurrent stimulation in epiretinal neuroprostheses is crucial for vision restoration. This study found that while total charge is recovered, individual electrodes may not recover charge, especially with imbalanced currents, impacting device safety and efficacy.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Ophthalmology
Background:
- Epiretinal neuroprostheses aim to restore vision by stimulating retinal neurons.
- Concurrent stimulation is necessary for effective phosphene generation but presents challenges like current leakage and charge recovery.
- Understanding charge recovery is critical for the safe and effective design of visual prosthetics.
Purpose of the Study:
- To investigate the effect of concurrent stimulation on charge recovery in hexagonal platinum electrode arrays.
- To analyze charge recovery at individual electrodes and the total charge recovery for dual arrays.
- To assess the impact of balanced versus imbalanced current delivery on charge recovery.
Main Methods:
- Utilized both computational simulations and experimental setups in physiological saline.
- Employed two hexagonally arranged platinum electrode arrays for concurrent stimulation.
- Delivered both balanced and imbalanced currents to the electrode arrays.
Main Results:
- Charge was not recovered at individual electrodes during concurrent stimulation, particularly with imbalanced currents.
- Significant current leakage or 'cross-talk' between adjacent electrodes was observed.
- Despite individual electrode limitations, the total charge injected across both hexagonal arrays was fully recovered.
Conclusions:
- Individual electrode charge recovery is a significant concern in concurrent stimulation paradigms for epiretinal implants.
- Imbalanced current delivery exacerbates charge recovery issues at the electrode level.
- Future designs must address individual electrode charge recovery to ensure device safety and optimize visual prosthetic performance.
