Controllers Field programmable gate arrays (FPGA) 4 Integrated circuit design 4 Controlled drug delivery 3 Cost effectiveness 3 Digital controller designs 3 Digital controllers 3 Field programmables 3 Field-programmable gated array 3 Hexagonal stimulation 3 Implant devices 3 Implants (surgical) 3 Micro/nano 3 Ophthalmology 3 Retinal implant technology 3 Subretinal implants 3 Wireless telemetry systems 3 digital controller 3 field-programmable gated arrays 3 hexagonal stimulation 3 wireless telemetry system 3 Analog to digital conversion 1 Analog to digital converters 1 Boost 1 Boost converter 1 Buck 1 Buck-Boost converter 1 Buck/boost converters 1 Closed-loop FES 1 Computer circuits 1