Personnel: Neal S. Peachey, Sherry Ball, Brett Hanzlicek, Marc Schiavone, Jiang Wu, Li Xu and Minzhong Yu
(a) Prostheses for the Restoration of Visual Function: We hypothesize that a photodiode-based device permanently below the retinal will respond to light with an electric current capable of artificially stimulating the visual system, and thereby restore function to a retina blinded by photoreceptor degeneration.
(b) Evaluation of the Retina with a Sub-retinal Microphotodiode Array: This project concerns the tissue compatibility of a subretinal microphotodiode array that has been developed in an attempt to restore vision in patients blinded by diseases causing photoreceptor degeneration. In these diseases, only the photoreceptors degenerate, sparing the inner retinal neurons. The microphotodiode approach relies on electrical stimulation of these inner retinal layers to propagate the visual signal centrally. In the course of evaluating several implant designs, we have developed a body of data indicating that the implant has good biocompatibility and have found that the use of specific materials for implant fabrication results in a device that will respond consistently for up to 3 years following implantation. While the implant induces disorganization of the inner retinal cell layers, there is no loss of inner retinal neurons in the implanted retina. In addition, the use of cytochemical markers has identified subtle but reproducible changes in the distribution of inhibitory neurons in the inner retina. We are now trying to determine the time course over which these changes occur. The data derived from these studies will provide valuable information on how the inner retina responds to the implant, and may also define areas for implant design improvements.