Patent Application
20060224212
1. Field of the Invention
The present application relates to retinal prostheses and, more particularly, to an electrode for retinal stimulation.
2. Description of the Related Art
The human eye has a number of components. These include the cornea, iris, pupil, lens, optic nerve, vitreous humor, the sclera and the retina. The cornea is the clear front window of the eye that transmits and focuses light into the eye. The iris is the colored part of the eye that helps regulate the amount of light that enters the eye. The pupil is the dark aperture in the iris that determines how much light is let into the eye. The lens is the transparent structure inside the eye that focuses light rays onto the retina. The vitreous humor is a clear, jelly-like substance that fills the middle of the eye. The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. There is a small area, called the macula, in the retina that contains special light-sensitive cells. The macula allows us to see fine details clearly. The sclera is commonly known as “the white of the eye.” It is the tough, opaque tissue that serves as the eye's protective outer coat. The retina includes several layers of cells. At the light-sensing surface of the retina is a layer of photo-receptor cells referred to as “rods” and “cones.” Beneath the photo-receptor cells several layers of intermediary cells (such as pedicules spherules, horizontal bipolar cells and amacrine cells) that transmit light-induced events from the photo-receptor cells to a layer of ganglion cells. The ganglion cell axons form the optic nerve, which travels from the eye and terminates in various regions of the brain, where the combined input is processed along multiple routes and ultimately results in the experience of sight. Essentially, the axons transmit light-induced events from the retina to the visual cortex in the brain.
Certain patients have healthy ganglion cells, but have degenerated photo-receptor cells. If the photo-receptor cells are substantially degenerated, then blindness results. If the patient's ganglion cells are healthy and intact, then artificial stimulation of the ganglion cells results in impulses being transmitted to the visual cortex, thereby generating perception of light.
Several intraocular retinal prosthetic devices have been proposed to combat the effects of certain types of progressive blindness. Such prostheses are intended to stimulate retinal ganglion cells whose associated photoreceptor cells have fallen victim to degradation by diseases such as macular degeneration or retinitis pigmentosa, two currently incurable but widespread conditions.
Retinal prostheses attempt to bypass degenerated photoreceptors by providing electrical stimulation directly to the underlying ganglion cells. Electrical stimulation of the ganglion cells by a retinal prosthesis attempts to mimic the electrical activity within a retinal ganglion cell corresponding to a visual stimulus of a photo-receptor cell. Direct stimulation of the ganglion cells may restore a measure of sight to patients with substantial photo-receptor cell degeneration.
A retinal prosthesis includes a source of electrical impulses that correspond to light that would be received by the eye. The impulses could be computer generated, using input from a camera to transmit corresponding impulses to an array of electrodes that interface with the ganglion cells in the patient's eye.
Several references disclose systems for the electrical stimulation of the retina by a retinal electrode array held against the retina, including systems for capturing a video image, transferring the image wirelessly into a living body and applying the image to a retinal electrode array. One proposed electrode array includes wire-type electrodes that stick into the layer of ganglion cells. One term for this type of an electrode array is a “pin cushion array.” The wire-type electrodes are held by a non-conductive frame that is implanted in the eye and are electrically connected to a ribbon cable that passes information from the computer to the electrode array. The electrodes themselves must be anchored to the retina with sufficient strength to accommodate physical agitation due to daily activity. One difficulty with such an array is that the anchoring may be insufficient, thereby allowing the electrodes to dislodge from the ganglion cells.
Therefore, there is a need for a retinal electrode array that is stable when applied to the retinal area of an eye.
The present invention, in one aspect, is a neural electrode array that includes an electrode support member, a conductor and at least one anchor structure. The electrode support member is substantially rigid and non-conductive and defines a plurality of spaced-apart holes passing therethrough. An electrically conductive contact is disposed adjacently to each hole. The conductor uniquely connects each contact to a bus. The anchor structure includes a portion for engagement with tissue that is capable of maintaining the support member in a substantially fixed relationship with a neural region.
In another aspect, the invention is a retinal electrode array that includes a substantially rigid and non-conductive electrode support member defining a plurality of spaced-apart holes passing therethrough and an electrically conductive contact disposed adjacently to each hole. A conductor uniquely connects each contact to a bus. At least one sclera anchor structure, including a portion for engagement with sclera tissue, is capable of maintaining the support member in a substantially fixed relationship with a retinal area of an eye.
In another aspect, the invention is a device for transmitting electrical impulses to an optic nerve. A retinal electrode array is configured to receive growth of optic nerve cells into a plurality of electrodes. A bus includes a plurality of conductors, with each conductor in electrical communication with a different electrode of the plurality of electrodes. The bus is capable of transmitting electrical pulses from an electrical pulse source to each of the plurality of electrodes.
In another aspect, the invention is a neural electrode that includes a substrate that defines a hole passing therethrough into which nerve tissue may grow. An electrode contact is exposed to the hole. An electrical conductor electrically couples the electrode contact to a source of electrical stimulation.
In yet another aspect, the invention is a method of transmitting electrical pulses to optic nerve cells, in which a retinal electrode array is applied to a retinal area of an eye. The retinal electrode array includes a rigid and nonconductive support member that defines a plurality of holes passing therethrough. The retinal electrode array also includes a plurality of electrodes, each in contact with a separate one of the plurality of holes, and a plurality of conductors, each conductor capable of placing a different line of a bus in electrical contact with a separate one of the plurality of electrodes. Nerve tissue is allowed to grow into at least a portion of the plurality of holes, thereby establishing contact between nerve cells and the plurality of electrodes. A stimulus is applied to at least one of the electrodes, thereby stimulating a nerve cell.
These and other aspects of the invention will become apparent from the following description of the preferred embodiments taken in conjunction with the following drawings. As would be clear to one skilled in the art, many variations and modifications of the invention may be effected without departing from the spirit and scope of the novel concepts of the disclosure.
A preferred embodiment of the invention is now described in detail. Referring to the drawings, like numbers indicate like parts throughout the views. As used in the description herein and throughout the claims, the following terms take the meanings explicitly associated herein, unless the context clearly dictates otherwise: the meaning of “a,” “an,” and “the” includes plural reference, the meaning of “in” includes “in” and “on.”
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The electrode support member 110 should be rigid and non-conductive. It could be made of materials such as: silica, silicon, amorphous glass, gallium arsenide and certain polymers (such as liquid crystal polymers).
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The retinal electrode array 100 is applied to a retinal area of an eye using established retinal surgical techniques. Once the retinal electrode array 100 has been implanted, nerve tissue is allowed to grow into the plurality of holes 120. This establishes contact between nerve cells and the plurality of electrodes 112 and secures the retinal electrode array 100 to the retinal tissue. Once nerve tissue has grown into the holes 120, stimuli are applied to the electrodes 112 via the bus 140, thereby stimulating nerve cells and causing a sensation of light.
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The invention is not limited to application to the retinal area. The invention can be applied to any neural region that processes multiple spaced-apart stimuli. In one example, as shown in
While the invention has been particularly shown and described with reference to a embodiment shown herein, it will be understood by those skilled in the art that various changes in form and detail maybe made without departing from the spirit and scope of the present invention as set for in the following claims. Furthermore, although elements of the invention may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.
