Artificial retina system for improving contrast sensitivity

Abstract

Provided is an artificial retina system for improving contrast sensitivity. The artificial retina system includes an artificial retina which is installed under the retina and includes a plurality of photodiode cells and a microcomputer. The microcomputer compares, with at least one reference value, the magnitude of an electric signal outputted from a photodiode in each of the photodiode cells. The microcomputer controls to amplify or reduce the electric signal outputted by each of the photodiode cells according to the result of comparison. Visual cells corresponding to each of the photodiode cells can be stimulated with an electric signal controlled by the microcomputer.

Claims

1. An artificial retina system for improving a contrast sensitivity, comprising: an artificial retina configured to be installed under a retina, the artificial retina including a plurality of photodiode cells; and a microcomputer configured to compare a magnitude of an electric signal output from a photodiode in each of the photodiode cells with a plurality of reference values and control to amplify or attenuate the electric signal output from each of the photodiode cells according to a result of the comparison, wherein each of the photodiode cells includes: the photodiode configured to convert light introduced from outside into the electric signal and output the electric signal; a copier configured to copy the electric signal output from the photodiode; an amplifier configured to amplify or attenuate the electric signal output from the copier; and a stimulation electrode configured to stimulate visual cells with the electric signal output from the amplifier, wherein the microcomputer adjusts gain of the amplifier to control to amplify or attenuate the electric signal output from the photodiode cell, wherein the microcomputer stores a gain value corresponding to a value equal to or greater than one of the plurality of reference values and less than another reference value, wherein the visual cells corresponding to each of the photodiode cells are stimulated with an electric signal controlled by the microcomputer.

2. The system of claim 1, wherein each of the photodiode cells further includes a converter configured to cause the electric signal output from each of the photodiode cells to have a form of a biphasic electric signal.

3. The system of claim 1, wherein when the number of the plurality of reference values is N, the number of the gain values is NH+1.

4. The system of claim 3, wherein the microcomputer includes: a transimpedance amplifier configured to convert the electric signal copied by the copier into a voltage signal; a comparator configured to compare a magnitude of the voltage converted by the transimpedance amplifier with the plurality of reference values; a controller configured to control the amplifier in accordance with the result of the comparison by the comparator; and a memory configured to store a gain value of the amplifier determined by the controller.

5. The system of claim 1, further comprising: a user input unit configured to receive a user command; and an external computer configured to execute the microcomputer according to the user command.

6. The system of claim 5, wherein the microcomputer further includes a communication unit configured to wirelessly communicate with the external computer.

7. An artificial retina system for improving a contrast sensitivity, comprising: an artificial retina configured to be installed under a retina and include a plurality of photodiode cells; and a microcomputer configured to compare a magnitude of an electric signal flowing from a first photodiode of each of the photodiode cells with a magnitude of an electric signal flowing from a second photodiode which is adjacent to the first photodiode, the microcomputer configured to control to amplify or attenuate an electric signal output from each of the photodiode cells in accordance with a result of the comparison, wherein each of the photodiode cells includes: the photodiode configured to convert light introduced from outside into the electric signal and output the electric signal; and a copier configured to copy the electric signal output from the photodiode, wherein the microcomputer includes: a comparator configured to compare a magnitude of a copied electric signal output from the first photodiode and a magnitude of a copied electric signal output from the second photodiode; and a controller configured to open a first switch connected to the first photodiode that outputs a first electric signal and wherein the controller is configured to close a second switch connected to the second photodiode that outputs a second electric signal, the second signal being larger than the first signal, and wherein visual cells corresponding to each of the photodiode cells are stimulated with the electric signal controlled by the microcomputer.

8. An artificial retina system for improving a contrast sensitivity, comprising: an artificial retina configured to be installed under a retina and include a plurality of photodiode cells; and a microcomputer configured to compare a magnitude of an electric signal flowing from a photodiode of each of the photodiode cells with plurality of reference values and controls such that a current is output through a current generator in accordance with a result of the comparison, wherein each of the photodiode cells includes: the photodiode configured to convert light introduced from outside into the electric signal and output the electric signal; and a stimulation electrode configured to stimulate visual cells with the current generated by the current generator, wherein the microcomputer includes: a transimpedance amplifier configured to convert the electric signal output from the photodiode into a voltage signal; a comparator configured to compare the voltage signal converted by the transimpedance amplifier and the plurality of reference values and determine a magnitude of the current according to a comparison result; and the current generator configured to generate the current having the magnitude determined by the comparator and output it through the stimulation electrode, and wherein the visual cells corresponding to each of the photodiode cells are stimulated with the current controlled by the microcomputer.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1 and 2 are views for explaining the structure of the retina.

(2) FIG. 3 is a view for explaining the lateral inhibition phenomenon by the horizontal cells that improve contrast sensitivity of the retinal cells.

(3) FIG. 4 is a block diagram illustrating an artificial retina system according to an embodiment of the present invention.

(4) FIG. 5 is a schematic view of a location of an artificial retina according to an embodiment of the present invention.

(5) FIG. 6 is a conceptual diagram for explaining a structure of an artificial retina according to an embodiment of the present invention.

(6) FIG. 7 is a block diagram for explaining a configuration of a microcomputer according to an embodiment of the present invention.

(7) FIG. 8 is a diagram for explaining an operation of an artificial retina system according to an embodiment of the present invention.

(8) FIG. 9 is a diagram for explaining an operation of a comparator of the artificial retina system of FIG. 8.

(9) FIG. 10 is a diagram for explaining an operation of an artificial retina system according to another embodiment of the present invention.

(10) FIG. 11 is a diagram for explaining an operation of an artificial retina system according to still another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

1. Artificial Retina System According to First Embodiment

(11) First, an artificial retina system according to a first embodiment of the present invention will be described with reference to FIG. 4. FIG. 4 is a diagram illustrating the overall configuration of an artificial retina system. The artificial retina system according to the present invention includes an artificial retina 100, a microcomputer 200, a battery 300, an external power 400, a user input unit 500, and an external computer 600.

(12) The artificial retina 100 is a part which is installed on the visual cells layer of the retina and converts the light into an electric signal to stimulate the visual cells V with the converted electric signal, and the artificial retina 100 will be described in detail below.

(13) The microcomputer 200 is a part which controls each of the photodiode cells 110 of the artificial retina 100, and, specifically, it is a part that compares the magnitude of the electric signal flowing from a photodiode 111 with reference values R.sub.1 and R.sub.2, and controls to amplify or attenuate the electric signal output from each of photodiode cells 110 based on the result of the comparison. In this example, the control to amplify or attenuate the electric signal is performed by adjusting the gain of an amplifier 113 of the photodiode cell 100, and this process of gain adjustment by the microcomputer 200 will be described below.

(14) The battery 300 is a part that supplies power to the artificial retina 100 and the microcomputer 200. The battery 300 is inserted into the human body, connected to the artificial retina 100 and the microcomputer 200 through a cable, and charged by resonance with an external power 400 located outside the human body. The charging process of the battery 300 by the external power 400 is not a feature of the present invention, so a detailed description thereof will be omitted.

(15) The external computer 600 is a part that controls the artificial retina 100 and the microcomputer 200 from outside through communication with the microcomputer 200. It is possible to turn on/off each of the photodiode cells 110 of the artificial retina 100 through the operation of the external computer 600, and it is also possible to operate a switch S.

(16) The user input unit 500 is a part that inputs a command to the external computer 600 through the user input unit 500. The command input through the user input unit 500 and the external computer 600 controls the microcomputer 200.

(17) Next, the artificial retina 100 will be described in detail with reference to FIG. 5. FIG. 5 is a view for explaining a location where the artificial retina 100 is implanted in the retina.

(18) Light introduced into the eyeball from the outside reaches the visual cells through the ganglion cells and bipolar cells, and the visual cells V convert the light into electric signals to stimulate the bipolar cells B. These electric signals then travel through the bipolar cells B and the ganglion cells G, and then through the optic neuronal fibers connected to the ganglion cells G to be transmitted to the brain, which perceives the vision. However, patients with RP or AMD disease cannot perceive vision because these visual cells layer is damaged and cannot function properly. The artificial retina is a device that replaces damaged visual cells, which converts light introduced from the bipolar cells into electric signals to stimulate the visual cells to restore vision.

(19) Referring to FIG. 5, the artificial retina 100 is installed on the visual cells layer and electrically stimulates, with an electric signal, the visual cells V corresponding to the artificial retina 100. The artificial retina 100 is provided in the form of a chip, and a plurality of photodiode cells 110 are provided on the chip. Resolution of the implanted artificial retina 100 is proportional to the number of pixels of the photodiode cells. That is, the larger the number of the photodiode cells, the higher the resolution performance.

(20) The photodiode cell 110 will be described in detail with reference to FIG. 6. Referring to FIG. 6, the photodiode cell 110 includes a photodiode 111, a copier 112, an amplifier 113, a converter 114, and a stimulation electrode 115.

(21) The photodiode 111 is a part that senses the light introduced from the outside and converts the light into an electric signal corresponding thereto and outputs the same.

(22) The electric signal converted by the photodiode 111 is copied by a copier 112. One of the electric signals copied by the copier 112 flows into an amplifier 113 and the other flows into a transimpedance amplifier 210 of the microcomputer 200 to be described below.

(23) The electric signal flowing into the amplifier 113 is amplified or attenuated by the amplifier 113. The gain of the amplifier 113 is adjusted by the microcomputer 200 described below and it is possible to electrically stimulate the visual cells V by controlling the gain of the amplifier 113 so that the contrast sensitivity is improved.

(24) The converter 114 is a part that converts the electric signal amplified or attenuated by the amplifier 113 into a biphasic current pulse corresponding thereto. This is a part that makes the electric signal output from the photodiode cell 110 in the form of a biphasic electric signal, as the electric signal past through the amplifier 113 alone cannot stimulate the visual cells V and it is thus necessary to convert it into a biphasic current pulse by the converter 114. The converter 114 generates a biphasic current pulse corresponding to the magnitude and duration of the electric signal past through the amplifier 113.

(25) The stimulation electrode 115 is a part that stimulates the visual cells V with the biphasic current pulse generated by the converter 114. This is a part that stimulates the visual cells V with an electric signal output from the photodiode cell 110, and the patient with the artificial retina 100 can have a restoration of the vision by the stimulating electrode 115 stimulating the visual cells V.

(26) Next, the microcomputer 200 will be described in detail with reference to FIGS. 7 to 9.

(27) Referring to FIG. 7, the microcomputer 200 includes a transimpedance amplifier 210, a comparator 220, a controller 230, a memory 240, and a communication unit 250. Specifically, this is a part that compares the magnitude of the electric signal flowing from the photodiode 111 with the reference values R.sub.1 and R.sub.2, and controls, through gain control of the amplifier 113, to amplify or attenuate the electric signal output from each of the photodiode cells 110 based on the result of the comparison.

(28) Referring to FIGS. 8 and 9, a process of comparing the magnitude of the electric signal with the reference values R.sub.1 and R.sub.2 and adjusting the gain of the amplifier 113 will be described.

(29) When light enters the eyeball from the outside, the photodiode 111 of each of the photodiode cells 110 outputs an electric signal corresponding to the magnitude of the introduced light.

(30) The electric signals output from the photodiode 111 are copied by the copier 112, and at this time, one of the copied electric signals flows into the amplifier 113 and the other flows into the transimpedance amplifier 210.

(31) The electric signal flowing into the transimpedance amplifier 210 is converted into a voltage signal V.sub.N by the transimpedance amplifier 210. The voltage signal V.sub.N converted by the transimpedance amplifier 210 flows into the comparator 220.

(32) The comparator 220 compares the voltage signal V.sub.N with the predetermined reference values R.sub.1 and R.sub.2. In this example, the reference values R.sub.1 and R.sub.2 are stored in the memory 240 in advance. In the present description, it is exemplified that there are two reference values, but the number of reference values is not limited. Since the larger number of reference values enables the more precise gain adjustment, the further improved contrast sensitivity can be provided. Referring to FIG. 9, when there are two reference values, there are three gain values of the amplifier 113. In other words, when there are N reference values, there are N+1 gain values of the amplifier 113.

(33) When the voltage signal V.sub.N is greater than 0 and less than R.sub.1, the gain value is G.sub.1, when the voltage signal V.sub.N is greater than R.sub.1 and less than R.sub.2, the gain value is G.sub.2, and when the voltage signal V.sub.N is greater than R.sub.2, the gain value is G.sub.3.

(34) The gain of the amplifier 113 is adjusted through the controller 230 based on the result of the comparison of the voltage signal V.sub.N and the reference value through the comparator 220. That is, the controller 230 adjusts the gain of the amplifier 113 of each of the photodiode cells 110 through the gain value assigned by the comparator 220. Each of the photodiode cells 110 stimulates the visual cells V with electric signals having different magnitudes according to the magnitude of the introduced light, so that the contrast sensitivity of a patient with the artificial retina 100 can be improved.

2. Artificial Retina System According to Second Embodiment

(35) The artificial retina system according to the second embodiment of the present invention will be described with reference to FIG. 10. In the artificial retina system according to the first embodiment, the electric signal output from the photodiode 111 of each of the photodiode cells 110 is compared with a reference value, and the amplifier 113 is adjusted to have the gain value corresponding thereto, thus improving the contrast sensitivity, but in the artificial retina system according to the second embodiment, the contrast sensitivity is improved in the manner of comparing the electrical signals output from the photodiodes 111a and 111b of the adjacent photodiode cells 110 and controlling switches S.sub.1 and S.sub.2.

(36) While the configuration is identical to that of the artificial retina system according to the first embodiment, there is a difference in the method for improving the contrast sensitivity. Description of the same elements as those of the artificial retina system according to the first embodiment will be omitted, and only different elements will be described.

(37) First, when light enters the eyeball from the outside, the photodiodes 111a and 111b of each of the photodiode cells 110 output an electric signal corresponding to the magnitude of the introduced light.

(38) The copiers 112a and 112b copy electric signals output from the respective photodiodes 111a and 111b, and the copied electric signals flow into the comparator 220a.

(39) The comparator 220a compares the magnitudes of the two electric signals and the controller 230 closes the switch S.sub.2 on the side that outputs a larger electric signal and opens the switch S.sub.1 on the side that outputs a smaller electric signal. Among the adjacent photodiode cells 110, one is turned on and the other is turned off, so that the contrast sensitivity can be improved.

3. Artificial Retina System According to Third Embodiment

(40) The artificial retina system according to the third embodiment of the present invention will be described with reference to FIG. 11.

(41) The configuration is identical to that of the artificial retina system according to the first embodiment, but there is a difference in that a current generator 260 is additionally provided. The same elements as those of the artificial retina system according to the first embodiment will be omitted, and only different elements will be described.

(42) First, when light enters the eyeball from the outside, the photodiode 111 outputs an electric signal corresponding to the magnitude of the introduced light.

(43) The electric signal output from the photodiode 111 is converted into a voltage signal by the transimpedance amplifier 210, and the converted voltage signal is compared with a plurality of predetermined reference values by the comparator 220b. The current value is determined according to the result of the comparison, and the determined value is input to the current generator 260 to select the biphasic current having various magnitudes stored in advance, and the selected current is output through the stimulation electrode 150. Similarly to the artificial retina system according to the first embodiment, the artificial retina system according to the third embodiment can improve the contrast sensitivity in that the manner of comparing a plurality of reference values with output signals and adjusting the signals output from the stimulus electrodes 150 based on the result of the comparison.

(44) It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. Accordingly, the scope of protection of the present invention should be determined by the claims.

DESCRIPTION OF THE REFERENCE NUMERALS

(45) 100: artificial retina

(46) 111: photodiode

(47) 112: copier

(48) 113: amplifier

(49) 114: converter

(50) 115: stimulation electrode

(51) 200: microcomputer

(52) 210: transformer impedance amplifier

(53) 220: comparator

(54) 230: controller

(55) 240: memory

(56) 250: communication unit

(57) 260: current generator

(58) 300: battery

(59) 400: external power

(60) 500: user input unit

(61) 600: external computer

(62) 1000: artificial retina system