Retinal microstimulation

A method for stimulating a plurality of retinal ganglion cells in a retina without penetrating the retinal basement membrane at the surface of the retina, comprising:

• (a) positioning a plurality of ganglion cell stimulating electrodes on or above the retinal basement membrane, the electrodes being laterally spaced apart from one another;
• (b) providing a ground electrode in operative association with each of the ganglion cell stimulating electrodes, with the ground electrode positioned on or above the retinal basement membrane and positioned for capturing electric current produced by its associated stimulating electrode;
• and
• (c) applying an electrical signal to selected ones of said stimulating electrodes sufficient to produce an electric current which penetrates the retina and produces an action potential in retinal ganglion cells.

A retinal microstimulator for stimulating retinal ganglion cells without penetrating the retinal basement membrane at the surface of the retina, comprising:

• (a) a substantially flat planar basement membrane contact portion;
• (b) an electrode carrier having an upper and lower surface, said basement membrane contact portion connected to said electrode carrier upper surface;
• (c) a plurality of stimulating electrodes having upper and lower portions, said stimulating electrode lower portions connected to said electrode carrier upper surface, and with said stimulating electrode upper portions projecting outward from said electrode carrier upper surface a distance not greater than said basement membrane contact portion;
• and
• (d) a ground electrode operatively associated with each of said stimulating electrodes;
• said ground electrode having an upper and lower portion, said ground electrode lower portion connected to said electrode carrier upper surface, and with said ground electrode upper portion projecting outward from said electrode carrier upper surface a distance not greater than said basement membrane contact portion.

A sensory prosthesis for a vision-impaired patient, comprising:

• (a) photodetector means for detecting a light signal;
• (b) a retinal microstimulator for stimulating retinal ganglion cells without penetrating the retinal basement membrane at the surface of the retina, comprising:
• (i) a substantially flat basement membrane contact portion;
• (ii) an electrode carrier having an upper and lower surface, said basement membrane contact portion connected to said electrode carrier upper surface;
• (iii) a plurality of stimulating electrodes having upper and lower portions, said stimulating electrode lower portions connected to said electrode carrier upper surface, and with said stimulating electrode upper portions projecting outward from said electrode carrier upper surface a distance not greater than said basement membrane contact portion;
• and
• (iv) a ground electrode operatively associated with each of said stimulating electrodes;
• said ground electrode having an upper and lower portion, said ground electrode lower portion connected to said electrode carrier upper surface, and with said ground electrode upper portion projecting outward from said electrode carrier upper surface a distance not greater than said basement membrane contact portion;
• and
• (c) means operatively associating said photodetector means with said retinal microstimulator for translating a light signal detected by said photodetector means into an electrical signal at said plurality of stimulating electrodes.