JP4959377B2 - Visual reproduction assist device - Google Patents

Description

  The present invention relates to a visual reproduction assisting device installed in a body in order to reproduce a part or all of a patient's vision.

In recent years, as one of the blindness treatment techniques, research has been conducted on a visual regeneration assisting device that attempts to regenerate vision by implanting an in-vivo device having electrodes or the like into the body and electrically stimulating cells constituting the retina. Such a visual reproduction assist device, for example, converts an image captured outside the body into an optical signal or a radio signal, and then transmits it to an in-vivo device installed in the body, and outputs a stimulation pulse signal from the stimulation electrode. There is an apparatus that attempts to reproduce vision by electrically stimulating cells constituting the retina (see, for example, Patent Document 1). It is necessary to use a precious metal having high biocompatibility for the stimulation electrode of such a device.
US Patent Application Publication No. 2006/0111757

  In such an apparatus, a predetermined amount of electric charge is injected into cells and tissues constituting the retina by an electrical stimulation pulse signal output from the stimulation electrode. The injected charge amount at this time is set within a range in which no adverse effect is exerted on the living body (for example, electrolysis of body fluid occurs around the electrode). The amount of charge that can be injected without adverse effects is affected by the electrode potential of the stimulation electrode before the start of energization. However, the stimulation electrode made of noble metal or the like generates various electrode potentials depending on the material and its installation state, etc., so when setting the condition of the injected charge amount in consideration of such a change range of the electrode potential, The injection charge amount is limited more than necessary, and it is difficult to provide the charge injection capability of the stimulation electrode.

  In view of the above-mentioned problems of the prior art, it is a technical problem to provide a visual reproduction assisting device that can efficiently utilize the charge injection capability of a stimulation electrode and that can output a suitable electrical stimulation pulse signal from the stimulation electrode. And

In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) In a visual regeneration assisting device that stimulates cells or tissues that form the visual nervous system that forms the vision of a patient and reproduces the patient's vision, the cells that are implanted in the body of the patient and constitute the visual nervous system A stimulation electrode for electrical stimulation of tissue, a control unit for outputting a bipolar electrical stimulation pulse signal from the stimulation electrode, and a reference for measuring the electrode potential of the stimulation electrode connected to the control unit The control unit, based on the electrode potential of the stimulation electrode obtained using the reference electrode, the peak of the electrode potential of the stimulation electrode at the time of output of the expected electrical stimulation pulse signal The amount of injected charge on the cathode side and the amount of injected charge on the anode side of the electrical stimulation pulse signal output from the stimulation electrode is controlled so as not to exceed the potential window of the stimulation electrode.
(2) In the visual reproduction assisting device of (1), the cathode-side injected charge amount and the anode-side injected charge amount of the cathode side and the anode-side injected charge amount output from the stimulation electrode are different. The inter-pulse potential (IPP) of the stimulation electrode is changed according to the difference in the amount of injected charges.
(3) In the visual reproduction assisting device according to (1) or (2), the stimulation electrode is formed on a substrate made of a biocompatible material, and the reference electrode is formed on the substrate. It is formed near the stimulation electrode.
(4) In the visual reproduction assistance device according to any one of (1) to (3), the control unit outputs a difference in the injected charge amount on the cathode side and the injected charge amount on the anode side from the stimulation electrode, and then the difference It is characterized by flowing a discharge current for canceling the amount of charges.
(5) The visual reproduction auxiliary device according to any one of (1) to (4) includes a reference electrode correction unit that corrects an electrode potential of the reference electrode, and the control is performed based on a command from the reference electrode correction unit. The unit corrects the electrode potential of the reference electrode.

  According to the present invention, the charge injection capability of the stimulation electrode can be utilized efficiently, and a suitable electrical stimulation pulse signal can be output from the stimulation electrode.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing an external appearance of a visual reproduction assisting device, FIG. 2 is a diagram showing an in-vivo device in the visual reproduction assisting device used in the embodiment, and FIG. 3 is a block diagram of a control system.

  Reference numeral 1 denotes a visual reproduction assisting device, as shown in FIGS. 1 and 2, from an extracorporeal device 10 for photographing the outside world and an in-vivo device 20 that applies electrical stimulation to cells constituting the retina and promotes visual reproduction. Become. The extracorporeal device 10 includes a visor 11 worn by a patient, an imaging device 12 including a CCD camera attached to the visor 11, an external device 13, a transmission unit 14 including a primary coil, and the like.

  The external device 13 is provided with a data modulation means 13a having an arithmetic processing circuit such as a CPU, and a battery 13b for supplying power to the visual reproduction assisting device 1 (external device 10 and internal device 20). The data modulation unit 13a performs image processing on the subject image captured by the image capturing device 12, and further converts the obtained image processed data into electrical stimulation pulse data for reproducing vision. The transmission means 14 made of a coil transmits (wireless transmission) the electrical stimulation pulse data converted by the data modulation means 13a and the power for driving the internal apparatus 20 described later to the internal apparatus 20 side as electromagnetic waves. Can do. A magnet (not shown) is attached to the center of the transmission means 14. The magnet is used to fix the position with the receiving means 31 described later.

  The visor 11 has an eyeglass shape, and can be used by being worn in front of the patient's eyes as shown in FIG. Moreover, the imaging device 12 is attached to the front surface of the visor 11 and can image a subject to be visually recognized by the patient.

  The in-vivo device 20 shown in FIG. 2 is roughly divided into a receiving unit 30 for receiving electrical stimulation pulse signal data and power transmitted from the extracorporeal device 10 by electromagnetic waves, and a stimulating unit for electrically stimulating cells constituting the retina. 40. The receiving unit 30 is provided with a receiving unit 31 including a secondary coil that receives electromagnetic waves from the extracorporeal device 10 and a control unit 32. The control unit 32 separates the electrical stimulation pulse data and the power received by the receiving unit 31 and designates the stimulation electrode corresponding to the electrical stimulation pulse signal for obtaining vision based on the electrical stimulation pulse data. It is converted into an electrode designation signal to be transmitted and transmitted to the stimulation unit 40.

  These receiving means 31 and control unit 32 are formed on a substrate 33. The receiving unit 30 is provided with a magnet (not shown) for fixing the position of the transmitting unit 14. Reference numeral 34 denotes a counter electrode (indifferent electrode) placed at a position facing each stimulation electrode 41 when a later-described stimulation unit 40 is placed on the patient's eye.

  In addition, the stimulation unit 40 is provided with a stimulation electrode 41 that outputs an electrical stimulation pulse signal, a stimulation control unit 42, and a reference electrode 44. Each stimulation electrode 41 is connected to the stimulation control unit 42, and the reference electrode 44 is connected to the control unit 32. This connection form will be described later. The stimulation control unit 42 has a multiplexer function that distributes the corresponding electrical stimulation pulse signal to each of the stimulation electrodes 41 based on the electrode designation signal sent from the control unit 32.

  The reference electrode 44 is a reference electrode for measuring the electrode potential of the stimulation electrode 41. The reference electrode 44 is preferably produced with a size equal to or larger than that of the stimulation electrode 41. For the reference electrode 44, a metal having high biocompatibility and high electrode potential stability, for example, silver silver chloride, platinum, iridium oxide, or the like is used. The stimulation electrode 41 is made of a noble metal with high biocompatibility, such as gold, platinum, iridium oxide, or the like. The stimulation electrode 41 and the reference electrode 44 are formed on the substrate 43, and the stimulation control unit 42 is flip-chip mounted on the substrate 43. In the present embodiment, the stimulation electrode 41 and the reference electrode 44 are made of iridium oxide. If the stimulation electrode 41 and the reference electrode 44 are made of the same material, the stimulation unit 40 can be easily manufactured. In addition, when the stimulation electrode 41 and the reference electrode 44 are integrally manufactured, the manufacturing operation is simplified. In the present embodiment, the stimulation electrode 41 and the reference electrode 44 are made of iridium oxide. The substrate 43 has a base portion made of a material that is highly biocompatible, such as polypropylene or polyimide, and is processed into a long plate shape that can be bent at a predetermined thickness. The substrate 43 is manufactured so as to have flexibility so as to follow the curved surface of the eyeball when implanted in the vicinity of the eyeball. A plurality of stimulation electrodes 41 are installed on the substrate 43, and a reference electrode 44 is installed in the vicinity of the stimulation electrode 41 on the installation surface of the stimulation electrode 41. Each of the stimulation electrode 41 and the reference electrode 44 is electrically connected to the stimulation control unit 42 through a lead wire 43a. A voltage measurement circuit is incorporated in the control unit 32, and the control unit 32 measures the potential difference between the reference electrode 44 and the stimulation electrode 41, whereby the electrode potential of the stimulation electrode 41 based on the reference electrode 44 is determined. Acquired by the control unit 32. At this time, the reference electrode 44 is set to 0 V (zero level), and the potential difference of the stimulation electrode 41 from 0 V is measured.

  In addition, the receiving unit 30 and the stimulation unit 40 are electrically connected by a plurality of wires 50. The wire 50 uses a precious metal having good biocompatibility, and the plurality of wires 50 are bundled together by a tube 51 so as to be easily handled. Each wire 50 is provided with an insulating coating except for the connecting portion. In addition, the intracorporeal device 20 is embedded with a highly biocompatible resin, such as silicone, parylene, etc., except for the places where electricity such as the stimulation electrode 41, the reference electrode 44, and the tip of the counter electrode 34 is discharged or introduced. Is done. Thereby, the contact of body fluid etc. with respect to the in-body apparatus 20 is reduced.

  In addition, the control unit 32 reduces power loss as much as possible, and also has a biphasic pulse signal composed of a rectangular wave (for example, a bipolar pulse having a voltage waveform on the + side (anode side) and − side (cathode side)). (Signal), the circuit configuration can suppress the deviation of positive and negative charges. Here, hereinafter, it is expressed that a positive current flows when the electrode of interest discharges a current, and a negative current flows when the current is sucked. That is, the control unit 32 is configured to perform control for canceling out the amount of charge injected into the cells constituting the retina between the plus side and the minus side (details will be described later). Thereby, the damage by the long-term charge balance difference can be reduced with respect to the cell which comprises a retina. Further, the positive and negative pulse signals have a pulse signal intensity and duration (such as an injection charge amount that does not cause electrolysis of a body fluid or the like in the vicinity of the charge discharge portion, that is, in the vicinity of the stimulation electrode 41. Pulse width).

  The intracorporeal device 20 having such a configuration is installed at a predetermined position in the patient's body. FIG. 3 is a diagram illustrating an example in which the stimulation unit 40 is installed in the patient's eye E. As shown in the figure, a part of the substrate 43 is placed between the sclera E3 and the choroid E2 with the stimulation electrode 41 formed on the substrate 43 in contact with the choroid E2. Further, the stimulation control part 42 portion of the substrate 43 is placed outside the sclera E3. The substrate 43 is placed by incising a part of the sclera E3 to form a sclera pocket, inserting the electrode portion of the substrate 43 into the sclera pocket (outside the choroid E2), and then sewing. This is done by fixing the substrate 43 by, for example.

  The counter electrode 34 is placed at a position from the anterior eye portion in the center of the eye as shown in the figure. As a result, the retina E1 is located between the stimulation electrode 41 and the counter electrode 34. Therefore, the stimulation current from the stimulation electrode 41 efficiently passes through the retina.

  On the other hand, the receiving means 31 is installed at a predetermined position in the living body that can receive signals (electric stimulation pulse data signal and power) from the transmitting means 14 provided in the extracorporeal device 10. For example, as shown in FIG. 1, the receiving unit 30 (only the receiving unit 31 is shown in the figure) is embedded under the skin of the patient's temporal region and transmitted to a position facing the receiving unit 30 through the skin. The means 14 is installed. Since the magnet is attached to the receiving unit 30 similarly to the transmitting unit 14, the transmitting unit 14 and the receiving unit 30 are adhered to each other by magnetic force by positioning the transmitting unit 14 on the implanted receiving unit 30. Therefore, the transmission means 14 is held on the temporal region.

  In addition, the tube 51 which bundles the wire 50 extends under the skin toward the patient's eye along the temporal region from the receiving unit 30 embedded in the temporal region and is inserted into the eye socket. As shown in FIG. 3, the tube 51 placed in the eye socket passes through the outer side of the sclera E <b> 3 and is connected to the stimulation control unit 42 installed on the substrate 43.

  In the present embodiment, the reference electrode 44 is formed on the substrate of the stimulating unit 40. However, the present invention is not limited to this. The reference electrode 44 may not be provided in the stimulation unit 40, and the counter electrode 34 may function as the reference electrode 44. One or more electrodes of the stimulation electrode 41 may be used as a reference electrode.

  Next, an electrical stimulation pulse signal output from the stimulation electrode and a change in the electrode potential accompanying this will be described. FIG. 4 is a schematic diagram schematically showing a change in potential of the stimulation electrode when a pulse signal (rectangular single-phase electrical stimulation pulse signal) of equal charge amount is output from the stimulation electrode to the cathode side and the anode side. 4A shows the waveform of the stimulation current, and FIG. 4B shows the time change of the electrode potential at the stimulation electrode when the current pulse of FIG. 4A is energized from the stimulation electrode. It is a schematic diagram. In FIG. 4A, the horizontal axis represents time t and the vertical axis represents current i. In FIG. 4B, the horizontal axis represents time t, and the vertical axis represents the electrode potential, that is, the potential difference between the reference electrode and the stimulation electrode. FIG. 4 is a schematic diagram assuming a case where iridium oxide, which has a wide potential window and has a high charge injection capability, is used as a stimulating electrode and the reference electrode is silver / silver chloride. Note that the potential window refers to a potential region where an electrochemical reaction that is not focused on, such as decomposition of a solvent, does not occur in a certain electrochemical system (a combination of a solvent and an electrode). In the present invention, a potential region where water electrolysis does not occur in the in vivo environment is expressed as a potential window.

  As shown in FIG. 4 (a), the pulse signal S1 output to the cathode side and the pulse output to the anode side, with the waveform of the stimulation pulse signal output from the stimulation electrode as the duration tp and the current intensity Ap. The signal S2 has a biphasic (bipolar) pulse waveform. Here, for the sake of simplicity of explanation, a sufficient interval is provided between the pulse signals S1 and S2.

  When such a pulse signal is output from the stimulation electrode, the temporal change in the electrode potential of the stimulation electrode has a shape as shown in FIG. The electrode potential of the stimulation electrode changes with the release of the pulse signal (charge), and returns to the vicinity of the electrode potential when the current is not energized when the pulse signal is no longer emitted. Comparing the case where the pulse signal is output to the cathode side and the case where the pulse signal is output to the anode side, the electrode potential is Vc at the output to the cathode, and the electrode potential drops greatly, but the electrode potential is Va at the output to the cathode. Thus, the increase in electrode potential is small. In this way, even if a pulse signal having the same waveform is output to both poles, the stimulation electrode has an asymmetric electrode potential with respect to the charge amount (product of duration tp and current intensity Ap) of each of the pulse signals S1 and S2. Showing change. Such asymmetry is due to the characteristics of the electrode material.

  Note that Vmax and Vmin in FIG. 4B indicate the upper and lower limit values of the potential window of the stimulation electrode 41. In the case of iridium oxide, Vmax is about + 0.8V and Vmin is about -0.6V with respect to the silver / silver chloride reference electrode. Therefore, in electrical stimulation, it is necessary to output an electrical stimulation pulse signal within an electrode potential such that the potential of the stimulation electrode does not exceed the potential window (Vmin to Vmax) shown in FIG. . Here, in FIG. 4B, the electrode potential at which the pulse signal is not output or just before the output is referred to as IPP (Inter Pulse Potential). In the case of stimulation that makes the best use of the charge injection capability of the electrode, Va = Vmax and Vb = Vmin in FIG. 4B, but this is rarely the case, and Va = Vmax or Vb = Vmin. In many cases, the charge injection capability is limited in either state. In order to satisfy Va = Vmax and Vb = Vmin, it is necessary to set the inter-pulse potential IPP to a suitable value so that this state is realized.

  For this reason, in this embodiment, the output of the electrical stimulation pulse signal from the stimulation electrode is controlled as follows to efficiently utilize the charge injection capability of the stimulation electrode. FIG. 5 is a diagram schematically showing one stimulus of the electrical stimulation pulse signal output from the stimulation electrode 41 in the visual reproduction assisting device of the present embodiment. 5A shows the waveform of the electrical stimulation pulse signal, and FIG. 5B shows the electrode potential of the stimulation electrode 41 from which the electrical stimulation pulse signal shown in FIG. 5A is output. The stimulating electrode 41 is made of the same material (iridium oxide) as the electrode shown in FIG. The electrode potential of the stimulation electrode 41 is measured by the control unit 32 with reference to the reference electrode 44. As shown in FIG. 5, the electrical stimulation pulse signal includes a rectangular first phase pulse output on the cathode side having a duration tc and a current intensity Ac, and a current smaller than the current intensity Ac of the first phase pulse. An electrical stimulation phase P1 having an asymmetric bipolar pulse signal composed of a second phase pulse output to the anode side having an intensity Aa and a duration ta longer than the duration tc, and output after output of the electrical stimulation phase P1 And a short circuit phase P2 composed of small pulses. In the electrical stimulation phase P1, the second pulse has a role of canceling out the charge injected into the cell or the like by the first pulse to some extent.

  The amount of charge released (or inflow) by the first and second phase pulses is determined from the pulse duration and the intensity (here, current value). Therefore, the charge amount of the first phase pulse (injection charge amount) is Ac · tc, and the charge amount of the second phase pulse is Aa · ta. Here, in this embodiment, the electrical charge pulse signal is generated so as to satisfy Ac · tc <Aa · ta so that the charge amounts are different between the first phase pulse and the second phase pulse, and output from the stimulation electrode 41. . If the charge amounts of the first phase pulse and the second phase pulse are different, any combination of duration and current intensity may be used, for example, Ac = Aa and tc ≠ ta.

  The electrode potential of the stimulation electrode 41 from which an electrical stimulation pulse signal with an asymmetric charge amount is output is as shown in FIG. OP1 in the figure indicates an electrode potential and an open circuit potential (Open Circuit Potential) measured when the stimulation electrode 41 is left in the in vivo environment without being energized for a long time. At the time tc when the first phase pulse is output from the stimulation electrode 41, the current is sucked into the stimulation electrode 41, so that the electrode potential decreases (falls to the cathode side and the minus side). At the time ta when the second phase pulse is output from the stimulation electrode 41, since the current is discharged from the stimulation electrode 41, the electrode potential increases (increases toward the anode side and the plus side). As described above, since the charge amount of the second phase pulse exceeds the charge amount of the first phase pulse, the IPP of the stimulation electrode 41 does not become the open potential OP1, but is shifted to the anode side, and the bias potential BP Become. The amount of change in potential from the open potential OP1 to the bias potential BP is determined by the difference between the charge amounts of the first phase pulse and the second phase pulse.

  At this time, the charge balance is biased toward the anode in the electrical stimulation phase P1. In the short-circuit phase P2, the electric charge amount imbalance (positive charge bias) generated in the electrical stimulation phase P1 is discharged by short-circuiting the counter electrode 34 and the stimulation electrode 41 to cancel the charge bias ( This is a phase in which the difference charge amount is removed by the discharge current. The pulse of the short circuit phase P2 becomes a discharge current having a peak at the duration ts and the current intensity As. The polarity of the current intensity As is in a direction to eliminate the positive bias of the charge generated in the electrical stimulation phase P1.

  In the short-circuit phase P2, the charge imbalance in the electrical stimulation phase P1 is eliminated, but the IPP of the stimulation electrode 41 does not change in the electrode potential accompanying the change in the amount of charge. This phenomenon has been confirmed experimentally. This phenomenon is considered to be due to the high possibility that the current in the short-circuit phase P2 is a discharge current of the electric double layer in the vicinity of the stimulation electrode 41 and is not a Faraday current accompanied by a change in electrode potential.

  The IPP set to the bias potential BP decreases with time and becomes the open-circuit potential OP2. The open potential OP2 is higher than the previous open potential OP1 by the electrical stimulation phase P1. Here, the open-circuit potential OP <b> 2 becomes the IPP immediately before the next electrical stimulation pulse signal is output from the stimulation electrode 41.

  By repeatedly outputting such an asymmetric electrical stimulation pulse signal from the stimulation electrode 41, the potential of the stimulation electrode 41 is set to the open potential OP2 via the bias potential BP. Increasing the output (current intensity Ac) of the first phase pulse in the electrical stimulation phase P1 by changing the potential of the stimulation electrode 41 from the open potential OP1 to the bias potential BP and finally shifting to the open potential OP2. Can do. When the first phase pulse (cathode pulse) is output from the stimulation electrode 41, the potential of the stimulation electrode 41 is lowered. At this time, it is necessary that the electrode potential does not drop beyond the potential window Vmin. The potential difference from the open potential OP2 to the lower limit potential window Vmin is larger than the potential difference from the open potential OP1 to the potential window Vmin. Therefore, when starting the output of the next electrical stimulation pulse signal, the output of the first phase pulse can be increased, and the characteristics of the electrode having a wide potential window can be fully utilized (the potential window can be used for the peak of the electrode potential). It is possible to output an electrical stimulation pulse signal (without exceeding). Preferably, when the characteristics of the electrode potential change of the stimulating electrode are asymmetric as in the case of iridium oxide mentioned above (when the asymmetry is strong), the electrode potential is intermediate between the peak on the anode side and the peak on the cathode side. The neighborhood is positioned around the middle of the potential window (Vmax to Vmin). Thereby, the range (upper and lower limit values) of the potential window becomes a range in which the electrode potential of the stimulation electrode can be changed.

  In the present embodiment, the IPP is shifted to the open potential OP2 in the electrical stimulation phase P1, but in the control of the in-vivo device 20 driven in the living body, the electrical stimulation pulse signal is output a plurality of times, It is preferable that the IPP be gradually shifted to the open circuit potential OP2.

  Such control for making the electrical stimulation pulse signal asymmetric is performed by the control unit 32. The control unit 32 acquires the electrode potential of the stimulation electrode 41 with reference to the reference electrode 44, and when the acquired IPP of the stimulation electrode 41 is output from the stimulation electrode 41 by the method described above, An electrical stimulation pulse signal that makes IPP a predetermined potential is obtained, and a control signal for the stimulation control unit 42 is generated. At this time, the control unit 32 obtains the electrical stimulation pulse signal in consideration of the change characteristic of the electrode potential of the stimulation electrode 41. The acquisition of the change characteristic of the electrode potential by the control unit 32 is, for example, a method of acquiring the change characteristic of the electrode potential based on the electrical stimulation pulse signal output in the previous stage of the electrical stimulation phase P1, or the acquisition of the change characteristic of the electrode potential. For example, a method of outputting a pulse characteristic (for example, a symmetric bipolar pulse) from the stimulation electrode 41 and acquiring a change characteristic of the electrode potential from the change of the electrode potential at that time. The stimulation control unit 42 is controlled by the control signal for the stimulation control unit 42 generated by the control unit 32, and an expected asymmetric electrical stimulation pulse signal is output from the stimulation electrode 41. The control unit 32 is provided with a memory (storage means) for storing characteristic information of electrode potential change based on the material of the stimulation electrode 41, and the control unit 32 generates an electrical stimulation pulse signal based on the characteristic information. It is good. The characteristic information referred to here is a change characteristic of the electrode potential of the stimulation electrode 41 that differs depending on the material, and electrode potentials on the cathode side and anode side when a current (for example, a symmetric bipolar pulse) is output from the stimulation electrode 41. Any change ratio may be used.

  The above description is a method of setting the IPP to the predetermined bias potential BP and the open potential OP2. However, in actual electrical stimulation, the electrical stimulation pulse signal is periodically output from the stimulation electrode 41. In such a case, the control unit 32 generates an appropriate electrical stimulation pulse signal in a range not exceeding the potential window, and outputs the electrical stimulation pulse signal from the stimulation electrode 41. During this operation, the control unit 32 acquires the IPP of the stimulation electrode 41, shifts the IPP to the predetermined bias potential BP, and sets the open potential OP2 by the method described above. At this time, electrical stimulation is continued using the asymmetric electrical stimulation pulse signal generated by the control unit 32. Even while the electrical stimulation is continued with the generated asymmetric electrical stimulation pulse signal, the control unit 32 monitors the IPP (for example, once every 100 electrical stimulations), and the current IPP has a predetermined potential. If it is deviated from, the electrical stimulation pulse signal is generated and outputted from the stimulation electrode 41 so as to correct the displaced electric potential. Such a series of operations is repeated, and the IPP is maintained at a predetermined potential (open potential OP2) even during electrical stimulation of the cells constituting the retina.

  As described above, the IPP of the stimulation electrode 41 (its value is the open-circuit potential OP1) is acquired, and the electrical stimulation pulse signal is asymmetrical bipolar pulse in consideration of the characteristics of the electrode potential change of the electrode material. By making the waveform, a bias potential can be applied to the electrode of the stimulation electrode 41 from which this electrical stimulation pulse signal is output, and the IPP can be set to a predetermined potential (open potential OP2). Thereby, in the output of the electrical stimulation pulse signal from the stimulation electrode 41, the output of the electrical stimulation pulse (charge amount per pulse) can be increased within the range of the potential window of the stimulation electrode 41. In this way, the efficiency of electrical stimulation of cells, tissues, etc. can be improved within a range that does not adversely affect the living body. In addition, electrical stimulation of cells, tissues, and the like can be suitably performed regardless of the IPP generated by the material of the stimulation electrode 41 and installation conditions. Further, by making the charge amount of the anode and the cathode of the electrical stimulation pulse signal asymmetric, the IPP of the stimulation electrode 41 is set to a predetermined value (open potential) without applying a voltage in order to shift the IPP of the stimulation electrode 41. OP2). As a result, the IPP (electrode potential) can be controlled with a simple configuration in which a power source for applying a bias potential is not provided in the apparatus.

  The operation of the visual reproduction assisting apparatus having the above configuration will be described with reference to the control system block diagram shown in FIG. The setting of the electrode potential of the reference electrode 44 where the in-vivo device 20 is installed in the patient's body will be described.

  The electrode potential of the reference electrode 44 is obtained by the following procedure. An electrode is produced with the same material and the same size as the reference electrode 44 (not shown). This electrode is implanted in a place that is relatively close to the environment when an in-vivo device 20 such as the head of an experimental animal or the vicinity of an eyeball is implanted in a human body. An electrode implanted in the body and a silver-silver chloride electrode serving as a reference electrode for this electrode are connected to a voltmeter, and the electrode potential of the electrode is measured using the silver-silver chloride electrode as a reference (0 V). The electrode potential thus obtained is regarded as the electrode potential of the reference electrode 44 placed in the body.

  The potential difference corresponding to the electrode potential of the reference electrode 44 is reflected on the control unit 32 by the electrode potential correction unit 60 (see FIG. 6). The electrode potential correction unit 60 is connected to the control unit 32, sets the electrode potential of the reference electrode potential 44 with respect to the silver chloride electrode by operating switches, and stores the set value in a memory (not shown) of the control unit 32. To correct the electrode potential of the reference electrode 44 during operation in the body. For example, if the potential difference between the electrodes when the silver / silver chloride electrode is used as a reference is + 1V, the controller 32 adds + 1V correction to the electrode potential of the stimulation electrode 41 measured using the reference electrode 44 as a reference. In this way, the electrode potential of the reference electrode 44 is calibrated by the silver-silver chloride electrode, and the electrode potential of the stimulation electrode 41 is substantially measured based on the silver-silver chloride electrode under the operation of the intracorporeal device 20, that is, Is substantially 0V. After the electrode potential of the reference electrode 44 is corrected (calibrated), the reference electrode correction unit 60 is removed from the control unit 32. The electrode potential correction unit 60 may be configured to send a signal to the control unit 32 by wireless communication via the receiving unit 31. In addition to the method described above, an electrode equivalent to the reference electrode 44 is prepared in advance, the electrode potential of the electrode with respect to the silver-silver chloride electrode is obtained, and the correction based on the value is performed. A configuration of a reference electrode potential measurement unit that measures the electrode potential of the implanted reference electrode 44 based on an extracorporeal electrode (for example, a silver-silver chloride electrode) is added to the unit 60, and the in-vivo device 20 is installed in the body of the patient. Thereafter, the electrode potential of the reference electrode 44 may be obtained with reference to the extracorporeal electrode (not shown).

  The photographing data (image data) of the subject photographed by the photographing device 12 shown in FIG. 1 is sent to the data modulation means 13a. The data modulation means 13a converts the photographed subject into predetermined data parameters (electric stimulation pulse data) necessary for the patient to recognize, further modulates the modulated subject into a modulation signal suitable for transmission as an electromagnetic wave, and transmission means 14 is transmitted as an electromagnetic wave to the in-vivo device 20 side.

  At the same time, the data modulation means 13a transmits the power supplied from the battery 13b to the in-vivo device 20 side together with the modulation signal as an electromagnetic wave having a band different from the band of the modulation signal (electric stimulation pulse data) described above. .

  On the in-vivo device 20 side, the modulation signal and power sent from the extracorporeal device 10 are received by the receiving means 31 and sent to the control unit 32. The control unit 32 extracts a signal in a band used by the modulation signal from the received signal, forms an electrical stimulation pulse signal and an electrode designation signal based on the modulation signal, and sends the electrode designation signal to the stimulation control unit 42. Send. At this time, the control unit 32 measures the electrode potential (especially IPP) of the stimulation electrode 41 with the calibrated reference electrode 44 as a reference, and can preferably electrically stimulate the cells constituting the retina by the method described above. An electrical stimulation pulse signal is generated. The stimulation control unit 42 outputs an electrical stimulation pulse signal from each stimulation electrode 41 by the method described above based on the received electrode designation signal. The cells constituting the retina are electrically stimulated by the electrical stimulation pulse signal output from each stimulation electrode 41, and the patient obtains vision (light sense). The control unit 32 obtains electric power for driving the in-vivo device 20 by the receiving unit 31.

  In the embodiment described above, a rectangular pulse to the anode (plus) side is output after the rectangular pulse to the cathode (minus) side as the electrical stimulation pulse signal. However, the present invention is not limited to this. Absent. Any device capable of applying a bias to the IPP of the stimulation electrode 41 due to the bias of the electric charge generated by the electrical stimulation pulse signal may be used. For example, one electrical stimulation pulse signal is obtained by reversing the polarity of a rectangular pulse, using a monophasic pulse whose potential changes only on the anode side or the cathode side, or combining three or more rectangular pulses. In addition, a single-phase (one-phase) pulse may be a non-rectangular sine wave, triangular wave, or the like.

  Furthermore, in the present embodiment, the installation position of the in-vivo device 20 is positioned on the sclera side, and the cells constituting the retina E1 are electrically stimulated from the sclera side (choroid side). However, the present invention is not limited to this. Instead, any structure may be used as long as it electrically stimulates cells or tissues constituting the visual nervous system that forms the vision of the patient. For example, the stimulation electrode may be arranged in the eye of the patient's eye (on the retina or below the retina). Further, the stimulating electrode may be disposed on the optic nerve head in the eye or the optic nerve part outside the eye to electrically stimulate the optic nerve, or the stimulating electrode may be a visual nerve system such as the optic chiasm, outer knee, and cerebral cortex. It is good also as a structure which arrange | positions to the structure | tissue which performs high-order visual processing, and stimulates the cell which comprises each structure | tissue.

It is the schematic which showed the external appearance of the visual reproduction auxiliary | assistance apparatus. It is the schematic which showed the in-vivo apparatus of the visual reproduction assistance apparatus in this embodiment. It is the figure which showed the state which installed the in-vivo apparatus in the body. It is a figure explaining the characteristic of the electrode potential of the stimulation electrode. It is the figure which showed the electrical stimulation pulse signal output from the stimulation electrode 41, and the electrode potential of the stimulation electrode 41 at that time. It is the block diagram which showed the control system of the visual reproduction auxiliary | assistance apparatus in this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Visual reproduction | regeneration assistance apparatus 10 External apparatus 20 In-vivo apparatus 30 Receiving part 32 Control part 34 Counter electrode 40 Stimulation part 41 Stimulation electrode 42 Stimulation control part 44 Reference electrode

Claims (5)

In a visual reproduction assisting device for stimulating cells or tissues constituting the visual nervous system that forms the vision of a patient and reproducing the vision of the patient,
A stimulating electrode implanted in a patient's body for electrically stimulating cells or tissues constituting the visual nervous system;
A controller for outputting a bipolar electrical stimulation pulse signal from the stimulation electrode;
A reference electrode connected to the control unit for measuring the electrode potential of the stimulation electrode,
Based on the electrode potential of the stimulation electrode obtained by using the reference electrode, the control unit determines that the peak of the electrode potential of the stimulation electrode at the time of outputting the expected electrical stimulation pulse signal is the potential window of the stimulation electrode. The visual regeneration assisting apparatus is characterized in that the injection charge amount on the cathode side and the injection charge amount on the anode side of the electrical stimulation pulse signal output from the stimulation electrode are controlled to be different from each other. 2. The visual regeneration assisting device according to claim 1, wherein the cathode-side injected charge amount and the anode-side injected charge amount of the electrical stimulation pulse signal, which are different from the cathode-side injected charge amount and the anode-side injected charge amount output from the stimulation electrode. The visual regeneration assisting device is characterized in that the interpulse pulse potential (IPP) of the stimulation electrode is changed by the difference between the two. 3. The visual reproduction assisting device according to claim 1, wherein the stimulation electrode is formed on a substrate made of a biocompatible material, and the reference electrode is in the vicinity of the stimulation electrode formed on the substrate. A visual reproduction assisting device characterized by being formed. 4. The visual reproduction assistance device according to claim 1, wherein the control unit outputs the cathode side injected charge amount and the anode side injected charge amount differently from the stimulation electrode, and then cancels the difference charge amount. A visual reproduction auxiliary device characterized by flowing a discharge current for the purpose. The visual reproduction assisting device according to any one of claims 1 to 4 , further comprising reference electrode correction means for correcting an electrode potential of the reference electrode, wherein the control unit is configured to control the reference electrode based on a command from the reference electrode correction means. A visual reproduction assisting device which corrects the electrode potential of the visual display.