Threshold suprachoroidal-transretinal stimulation current required by different-size electrodes in rabbit eyes

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Neuroscience

Background:

• Suprachoroidal-transretinal stimulation (STS) is an emerging technology for visual prostheses.
• Optimizing electrode parameters is crucial for effective and safe device function.

Purpose of the Study:

• To determine the optimal electrode size and stimulus parameters for STS in rabbit eyes.
• To evaluate threshold currents for different electrode sizes and pulse durations.

Main Methods:

• Electrode arrays with varying diameters (50, 150, 350, 500 μm) were implanted in rabbit eyes.
• Electrically evoked potentials were recorded, and threshold currents measured using biphasic pulses (0.25–1.0 ms) at 1, 2, and 4 Hz.

Main Results:

• Smaller electrodes (50 μm) required high currents, exceeding safe limits.
• 150-μm electrodes showed lower thresholds at 1 Hz compared to larger electrodes.
• The 150-μm electrode exhibited the most significant threshold change with increased frequency and short pulses.

Conclusions:

• Larger surface area electrodes with longer pulse durations appear preferable for STS prostheses.
• Low-frequency stimulation is indicated as a safer approach for STS applications.