Abstract:
A neural electrode array 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.

Description:
BACKGROUND  
       [0001]     1. Field of the Invention  
         [0002]     The present application relates to retinal prostheses and, more particularly, to an electrode for retinal stimulation.  
         [0003]     2. Description of the Related Art  
         [0004]     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&#39;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.  
         [0005]     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&#39;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.  
         [0006]     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.  
         [0007]     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.  
         [0008]     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&#39;s eye.  
         [0009]     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.  
         [0010]     Therefore, there is a need for a retinal electrode array that is stable when applied to the retinal area of an eye.  
       SUMMARY OF THE INVENTION  
       [0011]     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.  
         [0012]     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.  
         [0013]     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.  
         [0014]     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.  
         [0015]     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.  
         [0016]     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. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS  
       [0017]      FIG. 1  is a schematic diagram of an electrode matrix implanted in an eye.  
         [0018]      FIG. 2  is a cross sectional diagram of an electrode matrix in which ganglion cells have grown into holes in the array.  
         [0019]      FIG. 3A  is a top plan view of a portion of an electrode matrix connected to a ribbon cable.  
         [0020]      FIG. 3B  is a top plan view of a portion of an alternative electrode matrix connected to a receiver.  
         [0021]      FIG. 4A  is a plan view of an electrode matrix.  
         [0022]      FIG. 4B  is a cross-sectional view of the electrode matrix shown in  FIG. 4A , taken along line  4 B- 4 B.  
         [0023]      FIG. 5A  is a cross-sectional view of one electrode arrangement.  
         [0024]      FIG. 5B  is a cross-sectional view of a second electrode arrangement.  
         [0025]      FIG. 6A  is a top plan view of a mono-polar electrode arrangement.  
         [0026]      FIG. 6B  is a top plan view of a bipolar electrode arrangement.  
         [0027]      FIG. 7  is a schematic diagram of one embodiment of the invention being applied to a visual cortex. 
     
    
     DETAILED DESCRIPTION  
       [0028]     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.” 
         [0029]     As shown in  FIG. 1 , one exemplary embodiment of the invention is a retinal electrode array  100  that is placed in the ocular system  10  of a user. The ocular system  10  includes a sclera  12 , a retina  20  and an optic nerve  22 . The retinal electrode array  100  includes an electrode support member  110  that is made of a substantially rigid non-conductive material that is non-reactive with surrounding eye tissues. The electrode support member  110  defines a plurality of holes  120  passing therethrough. The holes  120  are spaced apart in an ordered manner. The electrode support member  110  may be held in place against at least a portion of the retina  20  with at least one anchor pin  130 . In one illustrative embodiment, the holes  120  are about 10 microns in diameter and are spaced apart in a range of about 10 to 200 microns.  
         [0030]     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).  
         [0031]     As shown in  FIG. 2 , a plurality of electrodes  112  are disposed adjacent to each of the holes  120 . Ganglion cells  22  grow into the holes  120  and achieve contact with the electrodes  112 . As the ganglion cells grow through the holes  120  they further stabilize the retinal electrode array  100  relative to the retina  20 . To encourage the ganglion cells  22  to grow into the holes  120 , a nerve growth factor, such as brain-derived neurotropic factor (BDNF) or ciliary neurotropic factor (CNTF), may be applied to the electrode support member  110  in the region of substantially each of the holes  120 . A basement membrane matrix, such as MATRIGEL™, available from Becton, Dickenson and Company, 1 Becton Drive, Franklin Lakes, N.J. 07417, may be applied prior to applying the nerve growth factor. The basement membrane matrix will adhere to the electrode support member  110  and adsorb the nerve growth factor, thereby stabilizing it in the region of the holes  120 .  
         [0032]     As shown in  FIG. 3A , each of the electrodes  112  is electrically coupled to a different electrical lead  114 . All of the leads  114  form a data bus  140  that exits the eye  10 . Impulses from a computer interface can then be applied to the electrodes  112  via the data bus  140 . As shown in  FIG. 3B , data can be transmitted to the electrodes  112  via a radio frequency receiver unit  300 . The radio frequency receiver unit  300  could include an antenna  302 , a receiver  304 , processor  308  and an induction-coil driven power source  306 .  
         [0033]     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.  
         [0034]     As shown in  FIGS. 4A and 4B , one arrangement for an electrode array  100  has the holes  120  space apart evenly. They could be distributed in other patterns, such as circular, or even concentrated in predetermined areas of the electrode support member  110 .  
         [0035]     As shown in  FIG. 5A , the electrodes  112  may be disposed along a top surface  111  of the electrode support member  110 . In this arrangement, a ground electrode (not shown) would also be in electrical contact with the patient. Alternately, as shown in  FIG. 5B , each hole  120  could include an electrode  512  and a spaced-apart ground  514 , so that electrical impulses would be transmitted primarily along a path between the electrode  512  and the ground  514 . A shown in  FIG. 6A , the electrode  112  could encircle the hole  120 . Alternately, as shown in  FIG. 6B , the electrode  612  could be disposed around only a portion of the hole  120 , with the ground  614  being disposed along an opposite portion of the hole  120 . In this arrangement, the signal would stimulate nerve tissue primarily in the region between the electrode  612  and the ground  614  (which would be connected to a ground wire  618 ). The arrangements shown in  FIGS. 5B and 6B  may reduce the amount of cross-talk between electrodes.  
         [0036]     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  FIG. 7 , one embodiment of a neural electrode array  710 , including a plurality of spaced-apart holes  720 , is applied to the visual cortex  702  of a brain using established neurosurgical techniques. As is evident to those of skill in the neurological arts, the neural electrode may be used in many neural-computer interface applications, including those involving sensing neural impulses and stimulating motor neurons.  
         [0037]     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.