Subretinal photovoltaic prosthesis

A wireless subretinal implant tiled with photodiode pixels that convert projected light directly into local stimulation current, so each pixel is an independent photovoltaic stimulating unit with no external wiring. Because the natural lens cannot drive the diodes, the wearer looks through goggles that project a near-infrared image (around 880 nm) onto the chip while ambient visible light is blocked.

The leading example, PRIMA, uses roughly 100-micron pixels and has restored letter reading (with digital zoom) in people with geographic-atrophy AMD, the best form vision yet from an electronic retinal implant. Acuity is bounded near the pixel pitch; shrinking pixels raises resolution but lowers per-pixel current and demands closer bipolar-cell coupling.