A Preliminary Exploration on Ultrasonic Retinal Modulation: A Modelling Study

Conventional retinal prostheses aim to partially restore the visual function of the blind by electrically stimulating retinal neurons with implanted microelectrode array and have progressed into clinical applications. However, they involve invasive surgery for electrode array implantation, which raises chronic safety and stability issues as well as concerns among patients. Therefore, exploring a novel non-invasive method of retinal modulation is of significant importance. Previous studies have shown that ultrasound can elicit responses of retinal neurons, suggesting the potential of ultrasonic stimulation as a non-invasive retinal modulation method. One research found that the retinal ganglion cells (RGCs) can exhibit dual-peak responses to ultrasound, indicating that ultrasound maybe simultaneously activates RGCs directly and indirectly via presynaptic neurons of RGCs. However, there is currently a lack of research on the direct RGC response properties to different ultrasonic stimulation parameters. This study proposed a RGC model that included the mechanosensitive ion channel Piezo1, aiming to simulate the direct ultrasonic response of the RGC. By varying the fundamental frequency, intensity, pulse repetition frequency, and duty cycle of the ultrasound, this study explored the effects of these ultrasonic parameters on the spike number and response latency of the RGC. Our simulation results indicate that within the range of 1 ‘” 10 MHz, the ultrasonic fundamental frequency had small impact on the direct ultrasonic response properties of the RGC, while the sound intensity significantly modulated the direct response properties of the RGC. The ultrasonic pulse repetition frequency and duty cycle had different effects on the direct response properties of the RGC under varying intensities. This study provides a theoretical basis for understanding the mechanism of ultrasound retinal modulation and insight into further optimizing the parameters of ultrasonic retinal modulation.