Outer Retinal Degeneration

Objective To review progress toward an electronic retinal prosthesis for outerretinal degeneration. Method Literature review. Results Retinal degenerations such as retinitis pigmentosa result in a lossof photoreceptors. There is a secondary loss of inner retinal cells, but significantnumbers of bipolar and ganglion cells remain for many years. Electrical stimulationcan produce phosphenes in the eyes of individuals who are blind as a resultof retinitis pigmentosa. Several research groups are trying to exploit thisphenomenon to produce artificial vision with electronic retinal prostheses.Two groups, with private company sponsorship, have recently implanted first-generationdevices in subjects with advanced retinitis pigmentosa. They have reportedlimited preliminary results. This article seeks to put these results in abroader context and review potential obstacles to successful prosthesis development.These include inner retinal cell viability, high thresholds, signal encoding,power requirements, biocompatibility, and device encapsulation. Conclusion There has been substantial progress toward an electronic retinal prosthesis,but fully functional, long-lasting devices are not on the immediate horizon.