Do Excitatory and Inhibitory Electrical Fields Result After Stimulation of the Rabbit Retina With a Subretinal Micro–Electrode Array?

Abstract

Abstract: : Purpose: To correlate the electrical evoked potential (EEP) with change in the pattern of electrode stimulation of the rabbit retina with a micro–electrode array (MEA) placed in the subretinal space. Methods: Dutch–belted rabbits (n=3) were used in the study and treated according to the ARVO statement. EEP electrodes were placed onto the dura mater above the visual cortex and forehead. The EEP was recorded following electrical stimulation of the MEA placed beneath the visual streak in the subretinal space using the ab externo approach. The EEP amplitudes were determined in three consecutive trials with each trial containing 100 averaged measurements. The MEA consisted of 25 electrodes (5x5: 4x10^–4 cm²) with each electrode measuring 40µm x 40µm and a center–to–center spacing of 210µm. The EEP was first generated by individual stimulation of each electrode; second, by the simultaneous stimulation of two electrodes with an equal charge density. Statistical analysis with the Mann–Whitney U test with Bonferroni/Dunn correction was performed. Results: After individual stimulation of each electrode in the MEA, electrodes were characterized as producing an average, higher or lower EEP amplitude. The simultaneous stimulation of an electrode which generated the highest EEP amplitude, with each of the other 24 electrodes, led to a statistically significant increase in the EEP amplitude compared to dual stimulation with the average electrode. Similarly, the simultaneous stimulation of an electrode which generated the lowest EEP amplitude, with each of the other 24 electrodes, led to a statistically significant decrease in EEP amplitude compared to dual stimulation with the average electrode. Conclusions: The rabbit retina may contain excitatory and inhibitory electrical fields in the area of the visual streak following stimulation with a MEA placed in the subretinal space. This observation may need to be considered in the design of retinal prostheses to restore vision.

Keywords: retina • electrophysiology: non-clinical