Electrical stimulation of isolated rabbit retina

Area of Science:

• Biomedical Engineering
• Neuroscience
• Ophthalmology

Background:

• Degenerative retinal diseases like retinitis pigmentosa (RP) and age-related macular degeneration (ARMD) cause vision loss.
• Retinal prostheses are being developed to restore vision for patients with these conditions.
• Optimizing electrical stimulation parameters is crucial for effective retinal prosthesis function.

Purpose of the Study:

• To determine optimal voltage parameters for stimulating isolated retinas in the context of a Korean retinal prosthesis project.
• To investigate the relationship between voltage amplitude, stimulus duration, and ganglion cell response.
• To assess the impact of on-bipolar cell blockade on electrically evoked responses.

Main Methods:

• Electrical stimulation was delivered to isolated retinas using a microelectrode array (MEA).
• Ganglion cell activity was recorded across 59 channels while varying voltage amplitude (0.5 V to 3 V) and stimulus duration (100 µs to 1200 µs).
• The effect of L-(1)-2-amino-4-phosphonobutyric acid (APB) on cell-bipolar cells was evaluated.

Main Results:

• A threshold voltage of 1.5 V was identified for reliable ganglion cell response, with associated charge densities of 2123 µC/cm² and 15 nC/phase.
• A stimulus duration threshold of 300 µs was found at a fixed voltage of 2 V, with charge densities of 1698 µC/cm² and 12 nC/phase.
• Electrical stimulation evoked ganglion cell activity even after blocking on-bipolar cells with APB.

Conclusions:

• Preliminary experimental results provide key voltage parameter insights for retinal prosthesis development.
• The study establishes critical thresholds for voltage amplitude and stimulus duration for effective retinal stimulation.
• Ganglion cell responses to electrical stimuli are achievable independent of on-bipolar cell function, suggesting alternative pathways for visual signal processing.