Abstract
Retinal prostheses that seek to restore vision to those suffering from degeneration of photoreceptors are now being employed for some patients. Current technology is built upon the ability to excite residual retinal circuitry through electrical stimulation. We have been exploring the feasibility of using chemical stimulation as an alternative approach since it offers the potential advantage of providing the brain with a more natural neural signal as OFF and ON pathways can potentially be activated differentially.
A preliminary study using focal injection of glutamate to the subretinal surface of photoreceptor degenerate rats has demonstrated that differential stimulation of retinal ganglion cells occurs. A corresponding study in wild-type rats has shown that this is likely differential stimulation of the OFF and ON pathways. The spatial spread of glutamate stimulation suggests that visual acuity within the legal limit of blindness will be possible with the envisaged chemical retinal prosthesis and the time-course of glutamate induced responses indicates that stimulation at a rate satisfactory for reading is achievable.