Controllers Field programmable gate arrays (FPGA) 6 Cost effectiveness 5 Digital controllers 5 Implants (surgical) 5 Ophthalmology 5 Computer circuits 4 Integrated circuit design 4 Power amplifiers 4 Battery management systems 3 Charging (batteries) 3 Controlled drug delivery 3 Digital controller designs 3 Digital storage 3 Field programmables 3 Field-programmable gated array 3 Fuzzy logic 3 Fuzzy logic controllers 3 Hexagonal stimulation 3 Implant devices 3 Ions 3 Lithium-ion batteries 3 Micro/nano 3 Retinal implant technology 3 Subretinal implants 3 Wireless telemetry systems 3 digital controller 3 field-programmable gated arrays 3 hexagonal stimulation 3 lithium-ion battery 3