Subretinal electrical stimulation of the rabbit retina

A number of disorders results in photoreceptor degeneration, yet spare the inner retinal layers. We are investigating the possibility that retinal function may be restored in such a situation by electric current applied from the subretinal space. In the present study, bipolar strip electrodes receiving electric current from external photodiodes were implanted into the subretinal space of adult rabbits. Recordings were made from the scalp overlying the visual cortex in response to photic flash stimulation of one eye before surgery. This was compared to the visual cortex response caused by subretinal electrical stimulation of the same eye from an implanted strip electrode. Electric current to the strip electrode was provided by an externally connected photodiode that was stimulated at a remote location with a photoflash. The electrical stimulus was recordable as a brief electrical implant spike during stimulation. In addition, after the implant spike, cortical responses were obtained in response to subretinal electrical stimulation that resembled closely the normal light induced visual evoked potential produced by the pre-implanted eye. These results indicate that the visual system can be activated by electrical stimulation from the subretinal space and indicate that this approach may provide a means to restore vision to eyes blinded by outer retinal disease.