A Treatise of the Physical Aspects of Phosphenes and Single-Cell Selectivity in Retinal Stimulation

Objective: Artificial vision is currently in an early-stage of maturity. This can be understood as a falling short of visual prosthesis to generate a complete visual scene with detail perception. Similarly, the physical aspects of phosphenes or spots of light demand a better understanding. Approach: This study introduces the strategy of the activation area and pinpoints its usefulness to estimate the amount of cells activated and identify the size and shape of the phosphenes. A simulation framework was built by integrating the relevant retinal interface elements and the dynamics of the ionic channels in the ganglion cells. Shape perceptions reported by Keserü in clinical trials were directly compared with our simulation framework. Similarly, the strategy of the activation area is used on a proposed electrode array to activate single cells and to produce a small spot of light required for highresolution vision. Main Results: The wide range of shape responses formerly described by patients is highly correlated with our simulationbased findings. Single-cell selectivity was reached throughout the regions near the fovea, which is necessary in humans for activities where visual detail is of primary importance and thus relevant for high resolution vision. For realistic applications, we provided the dimensions of the electrode carrier for single localized stimulation. Significance: Together of being useful to identify the physical aspects of phosphenes generated by electrical stimulation, the applicability of the activation area can yield valuable strategies to attain single-cell selectivity.