RESUMEN
·Age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are common outer retinal degenerative problems, which are also the predominant causes of most blinding retinal diseases. Retinal prosthesis is a promising solution for such photoreceptor degeneration diseases.Most of current concepts for a retinal prosthesis are based on neuronal electrical stimulation. In the past twenty years, retinal prosthesis has been developed in two different directions: epiretinal prosthesis and subretinal prosthesis. Each prosthesis technique has its advantages and disadvantages. For epiretinal prosthesis, it is easier to be implanted and has the advantage of keeping most of the electronics in the vitreous cavity, off the retinal surface, which greatly helps in dissipating the heat generated by the implant device. In this paper, a brief overview of retinal prostheses concepts is introduced. After that, several important aspects of epiretinal electrical stimulation will be discussed. Moreover, some practical epiretinal prosthesis devices developed by researchers in United States, Germany and Japan in the past have been reviewed. We hope that the devices will be used widely in the near future.