In vivo optogenetic stimulation of the primate retina activates the visual cortex after long-term transduction

Various therapeutic strategies for vision restoration have been developed, including retinal prostheses [1:4], stem cell transplantation [5:8] and optogenetic therapies [9,10,19,11:18]. In optogenetic therapy, the residual retinal neurons surviving the pathological degenerative process are rendered light-sensitive. Using this approach, we targeted the retinal ganglion cells (RGCs) through the in vivo expression of an ectopic light-sensitive ion channel, ChrimsonR [13] coupled to the fluorescent reporter tdTomato. The application of this strategy to blind patients [20] suffering from retinal dystrophies raises important concerns about the long-term functional expression of efficient signal transmission to higher brain centers (i.e. the visual cortex). We have previously shown that the transfected retina displays high spatiotemporal resolution ex vivo, compatible with the perception of highly dynamic visual scenes at light levels suitable for use in humans. Other studies have provided evidence of retinal activation in vivo [17]. Here, we demonstrate, in non-human primates, sustained functional efficacy ~20 months after delivery of an AAV2.7m8-ChrimsonR-tdTomato vector similar to that currently undergoing clinical evaluation. Our results reveal a persistence of expression in the perifovea, mediating information transfer to higher brain centers. Indeed, we recorded visually evoked potentials in the primary visual cortex of anesthetized animals in response to optogenetic retinal activation. We used an intravitreal injection of synaptic blockers to isolate the cortical component resulting from the in vivo optogenetic stimulation of primate RGCs. Our findings demonstrate the long-term functional efficacy of optogenetic retinal information transfer to the brain in vivo.