Nystagmus analysis device, program, and analysis system

Abstract

Provided are a nystagmus analysis device and a program, with which nystagmus in a subject can be analyzed with high accuracy. Also provided is an analysis system using the analysis device and the program. The present invention is provided with: a data acquisition means (corresponding to processing in step S101) for acquiring waveform data representing a change in the line of sight of a subject over time; and an analysis means (corresponding to processing in steps S103 to S106) for analyzing the acquired waveform data to determine the occurrence timing of each of a plurality of times of nystagmus symptoms that occur within a prescribed period to be analyzed.

Description

Nystagmus analyzer, program, and analysis system

[0001] The present invention relates to a nystagmus analyzer and a program, and an analysis system using the same.

[0002] As people age, the ability to control balance declines, leading to increased risk of unsteadiness and falls. It has been reported that there are 150,000 cases of femoral neck fractures due to unsteadiness and falls each year, contributing to rising medical and nursing care costs. Humans have an organ in each inner ear that senses balance, called the vestibular system, and the body maintains balance based on signals transmitted from the left and right vestibular systems to the brain. Therefore, if there is some abnormality in vestibular function and the vestibular nerves are stimulated unevenly on both sides, the brain becomes confused and dizziness occurs.

[0003] Nystagmus testing is known as one type of test for dizziness. Patent Document 1 discloses an analysis system that analyzes nystagmus using video of a subject's pupils and links the results to head position data measured in parallel with the video. The invention disclosed in Patent Document 1 can analyze eye angle and eye velocity by dividing them into horizontal, vertical, and rotational components. Patent Document 2 discloses a recording device that measures a subject's head position and eye movement and records the measurement data from the moment the subject becomes aware of dizziness. The invention disclosed in Patent Document 2 can analyze the frequency of nystagmus, the number of nystagmuses, and the maximum slow phase velocity.

[0004] JP 2020-18704 A JP 2010-207532 A

[0005] Generally, eye movement is represented as sawtooth waveform data. Although nystagmus may occur at the timings when the waveform data reaches its extreme values, since some noise is included, strictly speaking, it cannot be said that nystagmus occurs at all of the timings when the waveform data reaches its extreme values. The inventions disclosed in the above patent documents analyze eye movement without taking into account the above-mentioned findings, and therefore cannot analyze nystagmus with high accuracy.

[0006] In view of the above-mentioned problems, the present invention provides a nystagmus analyzer and a program that can analyze the nystagmus of a subject with high accuracy. Furthermore, the present invention provides an analysis system that uses the nystagmus analyzer and the program.

[0007] According to the present invention, a data acquisition means for acquiring waveform data consisting of a plurality of points representing changes in the position of the subject's gaze over time, and an analysis means for analyzing the acquired waveform data to determine the timing of occurrence of each of a plurality of nystagmuses that occurred within a predetermined period to be analyzed, the analysis means performing a first extreme value detection process for detecting a point among the plurality of points that make up the waveform data as an extreme value when multiplying the front slope and the rear slope with respect to that point as a reference results in a negative value, and performing a second extreme value detection process for detecting a point among the plurality of points detected by the first extreme value detection process and determining whether the difference between the timing indicated by the front point and the timing indicated by the rear point is equal to or less than a threshold value. a second extreme value detection process for detecting a point among the plurality of points remaining after the neighboring point removal process as an extreme value if multiplying the front slope and the rear slope using that point as a reference results in a negative value; and a slope comparison process for comparing the front slope and the rear slope using that point as a reference and detecting that point if the value obtained by subtracting the absolute value of the front slope from the absolute value of the rear slope is equal to or greater than a threshold, and the timing indicated by the plurality of points detected by the slope comparison process is set as the timing of nystagmus occurrence.

[0008] Further, according to the present invention, there is provided a program for causing a computer to execute a data acquisition process for acquiring waveform data made up of a plurality of points that represent changes in the position of the subject's gaze over time, and an analysis process for analyzing the acquired waveform data to determine the occurrence timing of each of a plurality of nystagmuses that occurred within a predetermined period to be analyzed, wherein the analysis process includes a first extreme value detection process for detecting a point among the plurality of points that make up the waveform data as an extreme value when multiplying the front slope and the rear slope with respect to that point as a reference results in a negative value, and a second extreme value detection process for comparing two of the plurality of points detected by the first extreme value detection process to determine the timing indicated by the front point and the timing indicated by the rear point. is equal to or less than a threshold value; a second extreme value detection process that detects a point from among the multiple points left by the nearby point removal process as an extreme value if multiplying the front slope and the rear slope using that point as a reference results in a negative value; and a slope comparison process that compares the front slope and the rear slope using that point as a reference, and detects that point from among the multiple points detected by the second extreme value detection process if the value obtained by subtracting the absolute value of the front slope from the absolute value of the rear slope is equal to or greater than a threshold value, and the program determines each of the timings indicated by the multiple points detected by the slope comparison process as the occurrence timing of nystagmus.

[0009] Further, according to the present invention, there is provided an apparatus comprising: gaze measurement means for measuring at least the position of the gaze of a subject; head position measurement means for measuring the head position of the subject; recording means for recording changes in the gaze and head position of the subject over time; and analysis means for analyzing data recorded by the recording means and outputting an analysis result relating to the equilibrium function of the subject, wherein the analysis means analyzes waveform data consisting of a plurality of points representing changes in the gaze position of the subject over time measured by the gaze measurement means, and determines at least the occurrence timing of each of a plurality of occurrences of nystagmus that occurred within a predetermined period to be analyzed and outputs the analysis result; and the analysis means performs a first extreme value detection for detecting a point among the plurality of points constituting the waveform data as an extreme value when multiplying a front slope and a rear slope based on that point results in a negative value. and a neighboring point removal process that compares two of the multiple points detected by the first extreme value detection process, and if the difference between the timing indicated by the front point and the timing indicated by the rear point is equal to or less than a threshold, removes one point and leaves the other point. A second extreme value detection process that detects a point among the multiple points left by the neighboring point removal process as an extreme value if multiplying the front slope and the rear slope using that point as a reference results in a negative value. A slope comparison process that compares the front slope and the rear slope using that point as a reference, and detects that point if the value obtained by subtracting the absolute value of the front slope from the absolute value of the rear slope is equal to or greater than a threshold, and sets each of the timings indicated by the multiple points detected by the slope comparison process as the occurrence timing of nystagmus.

[0010] According to the above invention, waveform data representing changes in the subject's line of sight is analyzed to determine the timing of each of multiple occurrences of nystagmus within a predetermined period to be analyzed, thereby enabling the subject's nystagmus to be analyzed with high accuracy.

[0011] According to the present invention, there are provided a nystagmus analyzer and a program that can analyze the nystagmus of a subject with high accuracy. Furthermore, the present invention also provides an analysis system that uses the nystagmus analyzer and the program.

[0012] It is a diagram depicting the appearance of a test subject wearing a VR device. It is a configuration diagram of an analysis system according to the present invention. It is a flowchart showing the processing procedure of nystagmus analysis according to the present invention. It is a diagram showing waveform data after each process is executed. It is a diagram showing waveform data after each process is executed.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted where appropriate.

[0014] <Configuration of the Analysis System According to the Present Invention> First, the configuration of the analysis system according to the present invention will be described. The present invention is a system for analyzing the equilibrium function of a subject.

[0015] FIG. 1 is a diagram depicting a subject wearing a VR device 100. When implementing the present invention, the VR device 100 is worn on the head of the subject, as shown in FIG. 1. The VR device 100 is a device that allows the wearer to experience a virtual reality environment, and is a so-called head-mounted display in which, when worn on the head, a display covers the area in front of the wearer's eyes. The VR device 100 displays moving images for testing the subject's balance function, records changes in the subject's line of sight and head position during the display, and collects measurement data for each.

[0016] FIG. 2 is a configuration diagram of an analysis system according to the present invention. As shown in FIG. 2, the VR device 100 includes a display unit 110, a gaze measurement unit 120, and a head position measurement unit 130. The display unit 110 displays moving images for testing the balance function of the subject, allowing the subject to view the moving images. The display unit 110 can be implemented by a liquid crystal display device or the like. The gaze measurement unit 120 measures the gaze of the subject viewing the moving images for testing the balance function of the subject. The gaze measurement unit 120 can be implemented by an eye tracker (a sensor that detects the subject's gaze). The gaze of the subject measured by the gaze measurement unit 120 includes the rotation axis and rotation angle of the subject's eyeball as well as the position of the subject's gaze (the position at which the subject is gazing). The head position measurement unit 130 measures the head position of the subject viewing the moving images for testing the balance function of the subject. The head position measuring means 130 can be realized by a gyro sensor (a sensor that detects angular velocity) or the like.

[0017] As shown in Figure 2, the VR device 100 is communicatively connected to the storage device 200, and the storage device 200 stores data measured by the VR device 100 (data showing changes in the subject's line of sight and head position over time).

[0018] 2, computer device 300 is communicably connected to storage device 200. Computer device 300 includes display means 310 implemented by a liquid crystal display device or the like. Computer device 300 also includes an information processing device such as a CPU (not shown) and storage devices such as ROM and RAM (not shown), and implements data acquisition means 320 and analysis means 330 through cooperation between this hardware and installed software.

[0019] The computer device 300 can read and analyze the measurement data stored in the storage device 200 and output the analysis results regarding the subject's balance function to the display means 310, and is configured as a nystagmus analyzer according to the present invention. The data acquisition means 320 acquires waveform data that represents changes in the subject's gaze over time. The analysis means 330 analyzes the acquired waveform data to determine the occurrence timing of each of the multiple nystagmus events that occurred within a predetermined period to be analyzed.

[0020] In implementing the present invention, communication between the VR device 100, the storage device 200, and the computer device 300 may be wireless or wired, and may be directly connected to each other or indirectly connected via other devices not shown.

[0021] <Flow of nystagmus analysis according to the present invention> Next, the flow of nystagmus analysis according to the present invention will be described. Fig. 3 is a flowchart showing the processing procedure of nystagmus analysis according to the present invention. Figs. 4 and 5 are diagrams showing waveform data after each process has been executed.

[0022] First, the computer device 300 (data acquisition means 320) acquires waveform data representing changes in the subject's line of sight over time from the storage device 200 (step S101).

[0023] 4A shows the waveform data acquired in step S101. Because the waveform data contains a large amount of noise, it is necessary to reduce the influence of noise in order to analyze nystagmus with high accuracy. To reduce the influence of noise, the computer device 300 according to this embodiment smoothes the waveform data acquired in step S101. Specifically, the computer device 300 plots the average value of multiple consecutive points (three points in this embodiment) in the waveform data acquired in step S101 (step S102).

[0024] 4B shows the waveform data smoothed in step S102. The computer device 300 according to this embodiment selects points in the waveform data that represent extreme values. Specifically, the computer device 300 multiplies the leading slope and trailing slope of a target timing by a reference time, and if the resulting value is positive, the computer device 300 omits the timing, and if the resulting value is negative, the computer device 300 retains the timing (step S103). The processing in step S103 corresponds to the "first processing" according to this invention.

[0025] 4C shows waveform data indicating the timings selected in step S103. The computer device 300 according to this embodiment executes a process to remove adjacent points (extreme points occurring within a time period sufficiently shorter than the occurrence time of the nystagmus) from the waveform data. Specifically, when the difference between an earlier timing and a later timing among the timings left in step S103 is equal to or less than a threshold, the computer device 300 removes one timing and keeps the other timing (step S104). The process in step S104 corresponds to the "first second process" according to the present invention.

[0026] 5A shows waveform data in which adjacent points have been omitted in step S104. The computer device 300 according to this embodiment selects points in the waveform data that represent extreme values. Specifically, the computer device 300 omits a timing when the multiplication of the leading slope and trailing slope relative to the target timing results in a positive value, and retains the timing when the multiplication results in a negative value (step S105). The processing in step S105 corresponds to the "second first processing" according to the present invention.

[0027] FIG. 5B shows waveform data indicating the timings selected in step S105. The computer device 300 according to this embodiment executes a process to select points in the waveform data where the slope of the fast phase (later in the time series) is greater than the slope of the slow phase (earlier in the time series). That is, since the definition of nystagmus dictates that the subject's gaze changes more significantly in the fast phase than in the slow phase, the computer device 300 selects points that meet this definition. Specifically, the computer device 300 compares the slope of the forward and backward sides of the waveform data based on the timing detected in step S105, and detects the timing when the absolute value of the backward slope minus the absolute value of the forward slope is equal to or greater than a threshold (step S106). The process in step S106 corresponds to the "second process" of this invention.

[0028] FIG. 5C shows waveform data indicating the timings selected in step S106. Each of these timings corresponds to the nystagmus timing extracted by the present invention. In this embodiment, the sign function is used to plot the nystagmus points at positions slightly separated along the Y axis of the waveform data to enhance the visibility of each nystagmus timing. The sign function returns 1 for positive numbers, -1 for negative numbers, and 0 for 0. Finally, the computer device 300 according to this embodiment outputs the waveform data indicating the nystagmus timings selected in step S106, i.e., the waveform data shown in FIG. 5C, to the display means 310 (step S107).

[0029] As described above, the computer device 300 (analysis means 330) according to this embodiment determines the timing of nystagmus occurrence by alternately executing a first process (steps S103 and S105) that detects extreme values ​​and a second process (steps S104 and S106) that omits some of the timing detected in the first process multiple times. In this way, the computer device 300 according to this embodiment can determine the timing of nystagmus occurrence with high accuracy by executing different types of second process in two stages.

[0030] However, the above content is merely one specific example of implementing the present invention, and the present invention may be implemented by performing processes corresponding to the above-described first and second processes once each to determine the timing of nystagmus occurrence, or by performing processes corresponding to the above-described first and second processes three or more times each to determine the timing of nystagmus occurrence. Thus, it can be said that computer device 300 (analysis means 330) determines the timing of nystagmus occurrence by performing a first process (steps S103 and S105) that detects the timings at which waveform data reaches extreme values, and a second process (steps S104 and S106) that omits some of the timings detected by the first process.

[0031] <Regarding the Program According to the Present Invention> The program according to the present invention, when installed in computer device 300, executes a data acquisition process (corresponding to the process of step S101 above) for acquiring waveform data that represents changes in the subject's gaze over time, and an analysis process (corresponding to the processes of steps S103 to S106 above) for analyzing the acquired waveform data and determining the occurrence timing of each of multiple nystagmus events that occurred within a predetermined period to be analyzed. This makes it possible to realize a program that can analyze the subject's nystagmus with high accuracy.

[0032] <Modifications> The above-described embodiment of the present invention can be modified in various ways within the scope of achieving the object of the present invention.

[0033] The present invention is not limited to being realized by the system configuration illustrated in FIG. 2 , and other configurations may be adopted. For example, in FIG. 2 , the storage device 200 is illustrated as if it were an external configuration of the computer device 300, but a corresponding configuration may be built into the computer device 300. Also, in FIG. 2 , one computer device 300 is illustrated as if one VR device 100 is provided for each computer device 300, but one or both may be realized by multiple devices. Also, in the system configuration illustrated in FIG. 2 , waveform data indicating the subject's gaze is acquired using the VR device 100, but the waveform data may be acquired using a separate device. For example, the waveform data may be acquired by analyzing an image of the subject's eyeball captured by a camera (not illustrated) to generate something equivalent to the waveform data described above.

[0034] The processing procedure described based on FIG. 3 is one specific example of implementing the present invention, and modifications may be made, such as changing the order of processing, omitting some processing, or adding processing not described in the above embodiment, within the scope of achieving the object of the present invention.

[0035] This embodiment encompasses the following technical concepts: (1) A nystagmus analyzer comprising: data acquisition means for acquiring waveform data representing changes in the subject's gaze over time; and analysis means for analyzing the acquired waveform data to determine the timing of occurrence of each of multiple nystagmus events occurring within a predetermined period to be analyzed. (2) The nystagmus analyzer described in (1), in which the analysis means determines the timing of occurrence of nystagmus by performing a first process for detecting the timing at which the waveform data reaches an extreme value and a second process for omitting some of the timings detected by the first process. (3) The nystagmus analyzer described in (2), in which the analysis means determines the timing of occurrence of nystagmus by alternately performing the first process and the second process multiple times. (4) The nystagmus analyzer described in (3), in which the first second process is a process for omitting one of the timings detected by the first first process and retaining the other when the difference between the leading and trailing timings is equal to or less than a threshold. (5) The nystagmus analyzer according to (3), wherein the second processing is a process of comparing the front tilt and the rear tilt using the timing detected by the second first processing as a reference, and detecting the timing when the value obtained by subtracting the absolute value of the front tilt from the absolute value of the rear tilt is equal to or greater than a threshold. (6) The nystagmus analyzer according to (3), wherein both the first processing and the second first processing are processes of omitting a timing when multiplying the front tilt and the rear tilt using a target timing as a reference and obtaining a positive value, and retaining the timing when the value is negative. (7) A program for causing a computer to execute a data acquisition process of acquiring waveform data representing changes in the subject's gaze over time, and an analysis process of analyzing the acquired waveform data to determine the occurrence timing of each of multiple nystagmus events that occurred within a predetermined period to be analyzed.(8) An analysis system comprising: a gaze measurement means for measuring the gaze of a subject; a head position measurement means for measuring the head position of the subject; a recording means for recording changes in the gaze and head position of the subject over time; and an analysis means for analyzing the data recorded by the recording means and outputting an analysis result regarding the equilibrium function of the subject, wherein the analysis means outputs at least the timing of each occurrence of multiple nystagmuses that occur within a predetermined period to be analyzed as the analysis result.

[0036] This application claims priority based on Japanese Patent Application No. 2023-132297, filed on August 15, 2023, the disclosure of which is incorporated herein in its entirety by reference.

[0037] 100 VR device 110 Display means 120 Gaze measurement means 130 Head position measurement means 200 Storage device 300 Computer device 310 Display means 320 Data acquisition means 330 Analysis means

Claims

1. A data acquisition means for acquiring waveform data composed of a plurality of points which indicate changes in the position of the subject's gaze over time; and an analysis means for analyzing the acquired waveform data to determine the occurrence timing of each of a plurality of occurrences of nystagmus which occurred within a predetermined period to be analyzed, the analysis means comprising: a first extreme value detection process for detecting a point among the plurality of points which constitute the waveform data as an extreme value if a negative value is obtained when the forward tilt and rearward tilt of the point are multiplied together; a nearby point removal process for comparing two of the plurality of points detected by the first extreme value detection process, and removing one point and leaving the other point if the difference between the timing indicated by the forward point and the timing indicated by the rearward point is equal to or less than a threshold; and a second extreme value detection process for detecting a point among the plurality of points remaining by the nearby point removal process as an extreme value if a negative value is obtained when the forward tilt and rearward tilt of the point are multiplied together. a tilt comparison process for comparing the tilt of the front side and the tilt of the rear side with respect to the multiple points detected by the second extreme value detection process, and detecting the point when the absolute value of the tilt of the front side subtracted from the absolute value of the tilt of the rear side is equal to or greater than a threshold value, and determining each of the timings indicated by the multiple points detected by the tilt comparison process as the occurrence timing of nystagmus.

2. A program for causing a computer to execute: a data acquisition process for acquiring waveform data composed of a plurality of points that represent changes in the position of the subject's gaze over time; and an analysis process for analyzing the acquired waveform data to determine the occurrence timing of each of a plurality of nystagmus events that occurred within a predetermined period to be analyzed, the analysis process comprising: a first extreme value detection process for detecting a point as an extreme value among the plurality of points that compose the waveform data when a negative value is obtained by multiplying the front tilt and rear tilt of the point as a reference; a nearby point removal process for comparing two points among the plurality of points detected by the first extreme value detection process, and removing one point and leaving the other point when the difference between the timing indicated by the front point and the timing indicated by the rear point is equal to or less than a threshold; and a second extreme value detection process for detecting a point as an extreme value among the plurality of points remaining by the nearby point removal process when a negative value is obtained by multiplying the front tilt and rear tilt of the point as a reference. a tilt comparison process for comparing the front tilt and rear tilt using a point among the multiple points detected by the second extreme value detection process as a reference, and detecting that point when the absolute value of the rear tilt minus the absolute value of the front tilt is equal to or greater than a threshold value; and determining each of the timings indicated by the multiple points detected by the tilt comparison process as the occurrence timing of nystagmus.

3. A system comprising: gaze measurement means for measuring at least the position of the gaze of a subject; head position measurement means for measuring the head position of the subject; recording means for recording changes in the gaze and head position of the subject over time; and analysis means for analyzing the data recorded by the recording means and outputting an analysis result relating to the equilibrium function of the subject, wherein the analysis means analyzes waveform data composed of a plurality of points representing changes in the gaze position of the subject over time measured by the gaze measurement means, and determines at least the occurrence timing of each of a plurality of occurrences of nystagmus that occurred within a predetermined period to be analyzed, and outputs this as the analysis result, wherein the analysis means performs a first extreme value detection process for detecting a point among the plurality of points constituting the waveform data as an extreme value when a negative value is obtained by multiplying a front slope and a rear slope based on that point; and a nearby point removal process for comparing two points out of the plurality of points detected by the first extreme value detection process, and omitting one point and leaving the other point when the difference between the timing indicated by the front point and the timing indicated by the rear point is equal to or less than a threshold value. a second extreme value detection process for detecting a point as an extreme value when, among the multiple points remaining after the nearby point removal process, multiplying the front slope and the rear slope with the point as a reference results in a negative value; and a slope comparison process for comparing the front slope and the rear slope with the point as a reference and detecting the point when the absolute value of the rear slope minus the absolute value of the front slope is equal to or greater than a threshold value, and each of the timings indicated by the multiple points detected by the slope comparison process is set as the occurrence timing of nystagmus.

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