Abstract
Purpose :
Recently electrical stimulation using temporally interfering (TI) electric fields has been attracting attentions for its ability to stimulate neural tissues distant from stimulation electrodes. This feature is advantageous for suprachroidal retinal prosthesis in which electrodes are relatively distant from the retina. The purpose of this study is to understand the spatiotemporal transients of electric fields at the retina caused by TI stimulation via suprachroidally implanted stimulation electrodes.
Methods :
Two-dimensional eye model consisting of sclera, choroid, retina, vitreous body and surrounding tissue was developed. Two-channel electrode array was placed in the sclera. Sinusoidal 1 mA-amplitude current waves were applied to the two electrodes. The frequencies of sinusoidal waves were 2 kHz for ch1 and 2.05 kHz for ch2 respectively. Evoked current distribution inside the eye was calculated and visualized by numerical analysis software (COMSOL Multiphysics).
Results :
At the RGC layer of the retina located on the centerline between two stimulation electrodes, a peak of the envelope (formed by superimposition of electric fields from two electrodes) of Y component was observed at 10 ms after the onset of TI stimulation (Fig. 1, red, green, and blue lines represent current from Ch. 1, from Ch. 2, and superposed current respectively). On the other hand, for X component, minimum value of the envelope was observed at 10 ms after the onset of TI (Fig. 1).
Conclusions :
Maximum value of the X component of envelope and minimum value of Y component was observed at the same time, suggesting that TI causes non-uniform, direction-dependent electric field. We will directly measure the electric field caused by TI in the saline as the next step.
This is a 2020 ARVO Annual Meeting abstract.