Retinal prosthesis : Testing prototypes on a dystrophic rat retina

The retina contains a mosaic of photoreceptors coupled to a intelligent neural network extracting important information on object edges, movements. This visual information is then transferred to the brain through the optic nerve. In pathologies like age macular degeneration or retinitis pigmentosa, photoreceptor degeneration leaves the retinal neuronal network unstimulated. Retinal prostheses propose to stimulate electrically this neuronal network to restore a useful vision for locomotion and reading. We are testing prototypes of subretinal prostheses on the retina of dystrophic rats with photoreceptor degeneration. Our experiments have enabled us to introduce reproducibly these prototypes into the subretinal space, to observe regularly the implant in vivo and measure longitudinally the electrode impedance. These in vivo measurements can then be correlated with the histological examination of the retinal tissue. In parallel, techniques were implemented to record retinal ganglion cell activity on the isolated retina to test different stimulation protocols. Classic retinal ganglion cell responses can be recorded with these techniques and allow to measure ganglion cell response to electrical stimulation. These studies should therefore contribute to improving the selectivity in the electrode retinal stimulation by retinal prostheses.