JP4827480B2 - Visual reproduction assist device - Google Patents

Description

  The present invention relates to a visual reproduction assisting device installed in the body for visual reproduction.

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 auxiliary device, for example, converts an image captured outside the body into an optical signal or a radio signal, and then transmits the signal to an in-vivo device installed in the body, and outputs a stimulation pulse signal from the electrode to output the retina. There is a device that attempts to regenerate vision by electrically stimulating the cells that make up (see, for example, Patent Document 1). In this way, when visual regeneration is promoted using the electrical stimulation pulse signal from the electrodes, it is necessary to increase the number of electrodes and ensure a high frame rate in order to obtain a clearer vision.
JP 2004-298298 A

In order to maintain a certain frame rate while arranging a large number of electrodes in such a visual reproduction auxiliary device, it is necessary to simultaneously output stimulation pulse signals from a plurality of electrodes. However, when stimulating at the same time with a plurality of electrodes, the current easily flows between the electrodes due to the difference in the intensity of the stimulation current. As a result, interference between stimulation currents is likely to occur, which affects visual reproduction.
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 suitably reproduce visual without causing current to flow between electrodes even when stimulation is performed simultaneously from a plurality of electrodes. To do.

In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) In the vision regeneration assisting apparatus for reproducing visual by electrically stimulating the cells constituting the retina by using a plurality of electrodes, and a control unit connected to said plurality of electrodes, electricity from the plurality of electrodes A control unit for outputting a stimulation pulse signal, and when the electrical stimulation pulse signal is output from the second electrode while the electrical stimulation pulse signal is output from the first electrode, the control unit A bevel trajectory is obtained for controlling the output of the electrical stimulation pulse signal so that the electrode potential of the first electrode is equal to the electrode potential of the second electrode.

  According to the present invention, even if stimulation is simultaneously performed from a plurality of electrodes, current can be reproduced suitably without current flowing between the electrodes.

  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 can transmit (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. 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 electrode corresponding to the electrical stimulation pulse signal for obtaining vision based on the electrical stimulation pulse data. It has a role for converting into an electrode designation signal and transmitting it to the stimulating unit 40. The control unit 32 minimizes power loss as much as possible, and positive and negative charges for each stimulus in a biphasic pulse signal (for example, a bipolar pulse signal having a voltage waveform on the + side and − side). The circuit configuration can maintain the balance. That is, the control unit 32 is configured to perform control to cancel the amount of charge injected into the cells constituting the retina on the plus side and the minus side. Thereby, the damage by the ion balance difference with respect to the cell which comprises a retina can be reduced.

  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 an indifferent electrode.

  The stimulation unit 40 is provided with an electrode 41 that outputs an electrical stimulation pulse signal, a stimulation control unit 42, and a reference electrode 44. Each electrode 41 and the reference electrode 44 are connected to the stimulus control unit 42. This connection form will be described later. The stimulation control unit 42 serves to distribute the corresponding electrical stimulation pulse signal to each of the 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 electrode 41. The reference electrode 44 is preferably produced with a size equal to or larger than that of the electrode 41. For the reference electrode 44, a metal having high biocompatibility and high electrode potential stability, such as silver silver chloride or iridium oxide, is used. The electrode 41 is made of a noble metal having high biocompatibility, such as gold or platinum. The electrode 41 and the reference electrode 44 are formed on the substrate 43, and the stimulus control unit 42 is flip-chip mounted on the substrate 43. 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 electrode 41 and the reference electrode 44 are disposed on the substrate 43, and are further electrically connected to the stimulation control unit 42 through a lead wire 43a.

  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.

  The intracorporeal device 20 having such a configuration is installed at a predetermined position in the patient's body. FIG. 4 is a diagram illustrating an example in which the stimulation unit 40 is installed on the patient's eye E. As shown in the drawing, a part of the substrate 43 is placed between the sclera E3 and the choroid E2 in a state where the electrode 41 formed on the substrate 43 is 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 indifferent electrode 34 is placed at a position from the anterior eye portion at the center of the eye as shown in the figure. As a result, the retina E1 is positioned between the electrode 41 and the indifferent electrode 34 (counter electrode). Therefore, the electrical stimulation pulse signal from the 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.

  The tube 51 that bundles the wires 50 extends from the receiving unit 30 embedded in the temporal region to the patient's eye along the temporal region, and is inserted into the eye socket through the inside of the patient's upper eyelid. As shown in FIG. 4, the tube 51 placed in the eye socket passes through the outer side of the sclera E3 and is connected to the stimulation control unit 42 installed on the substrate 43.

  In the present embodiment, the installation position of the in-vivo device 20 (stimulation unit 40) is positioned on the sclera E3 side, and the cells constituting the retina E1 are electrically stimulated from the sclera side (choroid side). However, it is not limited to this. It is only necessary that the electrode can be installed at a position where cells constituting the retina of the patient's eye can be suitably stimulated. For example, the internal device is placed in the eye of the patient's eye (on the retina or below the retina), and the tip of the substrate on which the electrode is formed is placed under the retina (between the retina and choroid) or on the retina. You can also

  In the present embodiment, the reference electrode 44 is used in the stimulation 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 indifferent electrode 34 may function as the reference electrode 44.

  Next, the schematic circuit and operation of this embodiment will be described. FIG. 5 is a schematic circuit diagram showing the connection between the electrode 41 and the indifferent electrode 34 and the reference electrode 44. FIG. 6 is a diagram showing a timing chart at each electrode 41. 42a is a power source and 42b is a switch part. The power source 42a schematically shows what becomes a power source when the stimulation control unit 42 outputs the electrical stimulation signal pulse signal. The switch unit 42b is incorporated in the stimulus control unit 42 and has a function of switching on / off of the electrodes 41a and 41b connected to the power source 42a under the control of the stimulus control unit 42. Reference numerals 41a and 41b denote electrodes of the electrode 41, which are referred to as an electrode A (first electrode) and an electrode B (second electrode), respectively. Reference numeral 34 is an indifferent electrode, and 44 is a reference electrode. The indifferent electrode 34 is connected to the control unit 32 in FIGS. 2 and 3, but here it is schematically connected to the power source 42 a. The electrodes 41a and 41b are each connected in parallel to the power source 42a. Both the electrodes 41a and 41b use the indifferent electrode 34 and the reference electrode 44 as a pair of electrodes.

  When the electrical stimulation pulse signal is output from one or both of the electrodes 41a and 41b, the switch unit 42b is controlled to open and close the switch. This switching control is performed by each switch. Here, it is assumed that electrical stimulation is performed with one electrode. When the switch is in the “open” state, the high input resistance state described above is entered, and even if an electrical stimulation pulse signal is output from the other electrode, no current flows into the switch in the “open” state. That is, a high input resistance (high input impedance) state is realized by disconnecting the electrode from the circuit (opening the electrode). Next, it is assumed that electrical stimulation is performed simultaneously from two electrodes. When both of the switch portions 42b are in the “closed” state, the electrodes 41a and 41b are both connected in parallel to the power source 42a. At this time, the electrode potentials of the electrodes 41a and 41b are equal to the reference electrode 44 (or the indifferent electrode 34). For this reason, a potential difference does not occur between the electrode 41a and the electrode 41b, and no current flows between the electrodes.

  Next, an example of a timing chart of the electrical stimulation pulse signal output from the electrode 41 will be described. The upper part of FIG. 6 shows a timing chart of the electrode A, and the lower part shows a timing chart of the electrode B. The horizontal axis of each chart indicates time, and the vertical axis indicates voltage. Here, a case is considered in which a biphasic electrical stimulation pulse signal is output simultaneously (at the same time) between the electrode A and the electrode B. In FIG. 6, one stimulus is composed of square waves on the plus side and the minus side. Here, the vertical axis in FIG. 6 indicates the potential difference between the reference electrode 44 and the stimulation electrode 41, that is, the electrode potential of the stimulation electrode 41. Further, the potential IPP (Inter-Pulse Potential) in FIG. 6 indicates the electrode potential when no stimulation pulse is output. At this time, the stimulation electrode 44 is maintained in a high input resistance state by the control unit 42.

As shown in the figure, a voltage of + V is applied by the stimulus control unit 42 to the electrodes A and B at time t ₀ . In the electrode A, the voltage + V is kept constant during the times T ₀₁ and T ₀₂ . On the other hand, in the electrode B, the voltage + V is kept constant during the time T ₀₁ , but is in a high input resistance state during the time T ₀₂ . At time T ₀₁ , since the electrodes A and B are at the same voltage + V, no potential difference occurs between the electrodes (equal electrode potential state). For this reason, no current flows between the electrodes. At time T ₀₂ , the voltage of the electrode A is + V, and the electrode B is in a high input resistance state. In general, since the applied voltage + V and IPP are different, a potential difference is generated between the electrode A and the electrode B, but no current flows between the electrodes. This is because the stimulus control unit 42 places the electrode B in a high input resistance state. For this reason, even if a potential difference arises between the electrode B that does not pass current and the electrode A that passes current, no current flows between the electrodes. In this way, even if electrical stimulation pulse signals are simultaneously output from different electrodes, no current flows between the electrodes.

Next, a method of adjusting the intensity of electrical stimulation with each electrode when simultaneously stimulating with different electrodes 41 will be described. Since the current does not flow between the electrodes when performing simultaneous stimulation, the current flow time, here, the duration at the voltage + V is changed at each electrode to give a difference in the intensity of the electrical stimulation. . The amount of charge injected from the electrode to the cells constituting the retina is changed by changing the current flow time at a constant voltage. As shown in FIG. 5, the electrode A passes a current at a voltage + V during a time T ₀₁ + T ₀₂ . The electrode B is _passing a current at a voltage + V during the time T ₀₁ . Comparing the amount of injected charge between the electrode A and the electrode B, the number of the electrode A in which the voltage + V is maintained longer is larger. In this way, the amount of injected charge is controlled by the duration of the electrical stimulation, thereby changing the intensity of the electrical stimulation. In addition, in the simultaneous stimulation of FIG. 5, the electrical stimulation to the minus side is the same concept as the method described above, and thus the description is omitted.

  Here, since it is assumed that the cells (biological tissues) constituting the retina are electrically stimulated, it is difficult to specify the waveform of the current value when the electrical stimulation is actually performed with a constant voltage. During electrical stimulation at a constant voltage, a transient response of current including a capacitive current component is observed. The integral value of the current obtained for each electrode is the amount of charge injected into the cells constituting the retina.

  As described above, each electrode that outputs an electrical stimulation pulse signal is connected in parallel to the power source, and the stimulation control unit controls the switching of each electrode, so that the electrical stimulation pulse signal of each electrode can be used during simultaneous stimulation. Can be made equal. By adopting such a configuration, it is possible to make the electrode potentials of the respective electrodes equal during simultaneous stimulation and to reduce the flow of current between the electrodes. Moreover, the intensity | strength of electrical stimulation is changed by changing the duration in each electrode of an electrical stimulation pulse signal.

  In the present embodiment described above, the electrical stimulation is started at the same time using different electrodes, but the present invention is not limited to this. As long as the electrode potential during electrical stimulation is constant, the timing of stimulation may be any combination.

  In the present embodiment described above, the first and second electrodes are provided one by one. However, the present invention is not limited to this. Since the present invention also assumes simultaneous stimulation using a plurality of electrodes, the present invention includes a case where a plurality of first electrodes and a plurality of second electrodes are provided.

  The operation of the visual reproduction assisting apparatus having the above-described configuration will be described based on the control system block diagram shown in FIG. 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. The stimulation control unit 42 outputs bipolar electrical stimulation pulse signals from each electrode 41 simultaneously or individually by the method described above based on the received electrode designation signal. When the electrical stimulation pulse signals are output simultaneously from the plurality of electrodes 41, the simultaneous output is performed so as not to prevent visual reproduction. By simultaneously outputting electrical stimulation pulse signals from the plurality of electrodes 41, the time required to recognize one image can be shortened and the frame rate can be increased. Each electrode 41 is connected in parallel to the power source, and the applied voltage is the same in each electrode. Therefore, even if electrical stimulation pulse signals are simultaneously output from the plurality of electrodes 41, no potential difference is generated, and interference between the electrodes hardly occurs, and visual reproduction can be suitably performed.

  The cells constituting the retina are electrically stimulated by the electrical stimulation pulse signal output from each 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 present embodiment described above, the electrical stimulation pulse signal is a biphasic pulse, and the charge amount is offset between plus and minus. However, the present invention is not limited to this. It may be a monophasic pulse in which the potential changes only on the plus side or the minus side, or a biphasic pulse in which the charge amount is not offset between plus and minus. In such a case, a process for bringing the total injected charge amount close to zero may be performed separately from the electrical stimulation pulse signal. As an example, a configuration is conceivable in which a capacitor is provided in the control unit or the stimulation control unit, the electric charge for each stimulation is accumulated, and discharged appropriately. Actually, even if electrical stimulation is performed with a biphasic pulse in which the positive and negative charge amounts cancel each other, the charges may not be offset somewhat. In order to cancel this, the charge generated during one pulse of electrical stimulation is accumulated in the capacitor and discharged, thereby bringing the charge balance in the eye close to zero. Thereby, the bias | inclination of the electric charge in an eye can be reduced.

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 block diagram which showed the control system of the visual reproduction auxiliary | assistance apparatus in this embodiment. It is the figure which showed the state which installed the in-vivo apparatus in the body. It is the figure which showed typically the circuit structure of this embodiment. It is the figure which showed the timing chart in the electrical stimulation of 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 Indifferent electrode 40 Stimulation part 41 Electrode 42 Stimulation control part 42a Power supply 42b Switch part 44 Reference electrode

Claims (1)

In a visual reproduction assisting device that reproduces vision by electrically stimulating cells constituting the retina using a plurality of electrodes ,
A control unit connected to said plurality of electrodes, and a control unit for outputting an electrical stimulation pulse signals from said plurality of electrodes, and outputs the electrical stimulation pulse signals from the first electrode In the case where the electrical stimulation pulse signal is output from the second electrode in the meantime, the control unit outputs the electrical stimulation pulse signal so that the electrode potential of the first electrode is equal to the electrode potential of the second electrode. Visual reproduction assisting device characterized by controlling.

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