Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical therapeutic systems
Reexamination Certificate
2001-04-02
2003-08-26
Schaetzle, Kennedy (Department: 3762)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical therapeutic systems
Reexamination Certificate
active
06611716
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is a medical product that can be used to correct vision loss or even complete blindness caused by certain retinal diseases. A variety of retinal diseases cause vision loss or blindness by destruction of the vascular layers of the eye including the choroid, choriocapillaris, and the outer retinal layers including Bruch's membrane and retinal pigment epithelium. Loss of these layers is followed by degeneration of the outer portion of the inner retina beginning with the photoreceptor layer. Variable sparing of the remaining inner retina composed of the outer nuclear, outer plexiform, inner nuclear, inner plexiform, ganglion cell and nerve fiber layers, may occur. The sparing of the inner retina allows electrical stimulation of this structure to produce sensations of light.
Prior efforts to produce vision by electrically stimulating various portions of the retina have been reported. One such attempt involved an externally powered photosensitive device with its photoactive surface and electrode surfaces on opposite sides. The device theoretically would stimulate the nerve fiber layer via direct placement upon this layer from the vitreous body side. The success of this device is unlikely due to it having to duplicate the complex frequency modulated neural signals of the nerve fiber layer. Furthermore, the nerve fiber layer runs in a general radial course with many layers of overlapping fibers from different portions of the retina. Selection of appropriate nerve fibers to stimulate to produce formed vision would be extremely difficult, if not impossible.
Another device involved a unit consisting of a supporting base onto which a photosensitive material such as selenium was coated. This device was designed to be inserted through an external scleral incision made at the posterior pole and would rest between the sclera and choroid, or between the choroid and retina. Light would cause a potential to develop on the photosensitive surface producing ions that would then theoretically migrate into the retina causing stimulation. However, because that device had no discrete surface structure to restrict the directional flow of charges, lateral migration and diffusion of charges would occur thereby preventing any acceptable resolution capability. Placement of that device between the sclera and choroid would also result in blockage of discrete ion migration to the photoreceptor and inner retinal layers. That was due to the presence of the choroid, choriocapillaris, Bruch's membrane and the retinal pigment epithelial layer all of which would block passage of those ions. Placement of the device between the choroid and the retina would still interpose Bruch's membrane and the retinal pigment epithelial layer in the pathway of discrete ion migration. As that device would be inserted into or through the highly vascular choroid of the posterior pole, subchoroidal, intraretinal and intraorbital hemorrhage would likely result along with disruption of blood flow to the posterior pole. One such device was reportedly constructed and implanted into a patient's eye resulting in light perception but not formed imagery.
A photovoltaic device artificial retina was also disclosed in U.S. Pat. No. 5,024,223. That device was inserted into the potential space within the retina itself. That space, called the subretinal space, is located between the outer and inner layers of the retina. The device was comprised of a plurality of so-called Surface Electrode Microphotodiodes (“SEMCPs”) deposited on a single silicon crystal substrate. SEMCPs transduced light into small electric currents that stimulated overlying and surrounding inner retinal cells. Due to the solid substrate nature of the SEMCPs, blockage of nutrients from the choroid to the inner retina occurred. Even with fenestrations of various geometries, permeation of oxygen and biological substances was not optimal.
Another method for a photovoltaic artificial retina device was reported in U.S. Pat. No. 5,397,350, which is incorporated herein by reference. That device was comprised of a plurality of so-called Independent Surface Electrode Microphotodiodes (ISEMCPs), disposed within a liquid vehicle, also for placement into the subretinal space of the eye. Because of the open spaces between adjacent ISEMCPs, nutrients and oxygen flowed from the outer retina into the inner retinal layers nourishing those layers. In another embodiment of that device, each ISEMCP included an electrical capacitor layer and was called an ISEMCP-C. ISEMCP-Cs produced a limited opposite direction electrical current in darkness compared to in the light, to induce visual sensations more effectively, and to prevent electrolysis damage to the retina due to prolonged monophasic electrical current stimulation.
These previous devices (SEMCPs, ISEMCPs, and ISEMCP-Cs) depended upon light in the visual environment to power them. The ability of these devices to function in continuous low light environments was, therefore, limited. Alignment of ISEMCPs and ISEMCP-Cs in the subretinal space so that they would all face incident light was also difficult.
SUMMARY OF THE INVENTION
This invention is, among other things, a system that allows for implantation of microscopic implants into the diseased eye so that the system can function in continuous low light levels, and also produce improved perception of light and dark details. This invention has two basic components: (1) multi-phasic microphotodiode retinal implants (“MMRIs”) of microscopic sizes that are implanted into the eye, and (2) an externally worn adaptive imaging retinal stimulation system (“AIRES”) that, among other things, uses infrared light to stimulate the MMRIs to produce “dark current” in the retina during low light conditions, and to improve perception of light and dark details.
In its basic form, a MMRI of this invention has, depending upon its orientation, a PiN configuration where the P-side of the implant has light filter layer that permits visible light to pass, and where the N-side of the implant has a light filter that permits only infrared (“IR”) light to pass, and preferably only selected wavelength(s) of IR light. In practice, a population of such MMRIs are implanted in the so-called “subretinal space” between the outer and inner retina in the eye such that, randomly, about half of them (i.e. the first subpopulation) will be oriented so that their P sides face light incident to the eye, and about the other half (i.e. the second subpopulation) will be oriented so that their N-sides face light incident to the eye.
In this location and orientation, the first subpopulation of MMRIs convert energy from incoming visible light into small electrical currents to stimulate the sensation of light in the eye to produce formed vision. In other words, the first subpopulation converts visible light to electrical current to stimulate the retina with “light currents” to induce the perception of visible light. The second subpopulation of MMRIs converts infrared light provided by AIRES into electrical currents to stimulate the retina with “dark currents” during low light conditions to induce the perception of darkness.
The adaptive imaging retinal stimulation system or AIRES is comprised of a projection and tracking optical system (“PTOS”), a neuro-net computer (“NNC”), an imaging CCD camera (“IMCCD”), and an input stylus pad (“ISP”).
In one embodiment of this invention, each microscopic implant comprises plural paired MMRI subunits disposed together in a single flattened cubic unit. The microscopic implants are fabricated so that each MMRI member of each pair has its positive pole electrode on one of the flattened surfaces, and its negative pole electrode on the other flattened surface. Each MMRI member of each pair is disposed so that it is oriented in the opposite direction from the other MMRI member of the pair, the negative (N) electrode of the first MMRI pair member being on or close to the same surface as the positive (P) electrode of the second MMRI pair member, and t
Chow Alan Y.
Chow Vincent
Brinks Hofer Gilson & Lione
Optobionics Corporation
Schaetzle Kennedy
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