The field of retinal prosthetic research, now more than 20 years old, has produced many high-quality technical options that have the potential to restore vision to patients with acquired disease of the outer retina. Five companies have performed Phase I clinical trials demonstrating that blind patients can reliably report basic elements of visual percepts induced by electrical stimulation. However, at present patients and observers generally do not consider the results to be useful enough in the performance of tasks of daily living to justify the risks of surgery and chronic implantation or the costs. Having developed a wireless device implanted in the subretinal space, the Boston Retinal Implant Project has focused its efforts on developing scalable technologies to create a hermetic device that can deliver individually controlled pulses of electrical stimulation to each of hundreds of electrodes. An advanced device with such attributes will be needed to justify the risks of implantation. An assessment of long-term biocompatibility for all devices remains to be done.