Subretinal implants for the recovery of vision

The German `SubRet´ consortium has fabricated various types of microphotodiode arrays, the photovoltaic response of which will induce a retina response after implantation in the subretinal space. Ultrathin and flexible devices have been designed as well as CMOS-based chips with different pixel sizes and electrode configurations. From in-vitro electrostimulation studies, it becomes clear that a purely photovoltaic mode of operation will not be feasible, but an additional energy input by near-infrared radiation or radio frequency power transmission needs to be incorporated. Implantation experiments on pigs and rabbits prove the biocompatibility, general function and local stability of the implants. The inner retina architecture is well preserved, and literally no glia proliferation is found from long-term monitoring and histological examination. In conclusion, the subretinal approach is very promising and our results are encouraging, although major obstacles cannot be excluded concerning the application in human