Research progress of epiretinal prosthesis based on electrical stimulation

There are currently many experimental efforts to develop a treatment to restore useful vision for blind patients by electrical stimulation at epiretina, which is based on experiments that inner retinal layers can be electrically stimulated and elicit an electrical-evoked response. Generally, various researches on visual prosthesis are mainly focused on two solutions according to the research emphasis. One type is different designs surrounding the hardware circuitry, the other type is function evaluation and physiological test of artificial retina. On the one hand, there are probably three aspects, which are elementary structure, important factors of structure and biocompatible consideration. Among them, main structure generally consists of about three parts in theory. Moreover, it is claimed that other factors such as electrode-retina interface and pulse shape, should be taken into account. And the last is material, electrode shape and production technique. On the other hand, in order to demonstrate that epiretinal stimulation actually helps construct a visual prosthesis, functional evaluation and physiological test of the artificial vision is required. At present, researchers mainly used several kinds of animals for vitro biocompatibility tests and vivo biocompatibility tests. Besides that, there are novel alternative which researchers attempted to find. This paper will begin with general considerations related to all or most of retinal prosthesis, and then concentrate on the epiretinal electrical design. At the end of the paper an outlook of the possible trend of epiretinal electrical stimulation in future is presented.