Determination device, inspection system, determination method, and program

Abstract

It can accurately determine whether or not there is an abnormality in cognitive function. [Solution] The judgment device comprises an acquisition unit that acquires the change in pupil diameter over time of a subject performing a task of finding a first object of interest from an examination image containing the first object; an identification unit that identifies a target section from the change in time; and a judgment unit that uses the target section to determine whether there is an abnormality in the subject's cognitive function, wherein the change in time has an examination section that includes a first section that represents the pupillary reaction due to changes in light intensity from when the examination image is displayed, and a second section that follows the first section and continues until the first object is found, and the target section is the second section.

Description

[Technical Field]

[0001] The present invention relates to a technique for assessing the cognitive function of a subject. [Background technology]

[0002] In recent years, cognitive decline, including dementia, has become a major problem throughout society. Early detection of dementia can slow the progression of symptoms and alleviate them. Therefore, early detection of dementia is becoming increasingly important.

[0003] Currently, the detection of dementia is mainly performed by medical interviews conducted by doctors at medical institutions. However, the increase in the elderly population is increasing the burden on medical institutions and doctors, and there is a need for simple and less burdensome methods of testing cognitive function. Therefore, various technologies for testing cognitive function have been proposed.

[0004] For example, Patent Document 1 discloses a physical condition estimation device that estimates the cognitive function of a subject. Specifically, the technology in Patent Document 1 acquires pupil diameter as eye movement data of the subject using a visual stimulus test pattern, and estimates the cognitive function of the subject based on the eye movement data. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-083328 Summary of the Invention [Problem to be solved by the invention]

[0006] However, pupil diameter can change depending on various factors other than the visual stimulus test pattern (for example, changes in light intensity). Therefore, the technology of Patent Document 1, which uses pupil diameter to estimate cognitive function, has room for improvement from the perspective of estimating cognitive function with high accuracy. In consideration of the above circumstances, the present invention aims to determine with high accuracy whether or not there is an abnormality in cognitive function. [Means for solving the problem]

[0007] [1] A determination device comprising: an acquisition unit that acquires the change in pupil diameter over time of a subject performing a task of finding a first object of interest from an examination image including the first object; an identification unit that identifies a target section from the change in time; and a determination unit that uses the target section to determine whether or not there is an abnormality in the cognitive function of the subject, wherein the change in time has an examination section that includes a first section that represents the pupillary response due to a change in light intensity from when the examination image is displayed, and a second section that follows the first section and continues until the first object is found, and the target section is the second section.

[0008] [2] The judgment device of [1], wherein the inspection image is displayed on a display device of a head-mounted display.

[0009] [3] A determination device according to [1] or [2], wherein the first section includes the time point at which the pupil diameter reaches its minimum value due to pupillary light reflex in the examination section, and the identification unit sets the time point at which the pupil diameter reaches its first maximum value after the time point at which the pupil diameter reaches its minimum value as the starting point of the second section.

[0010] [4] A determination device according to [1] to [3], wherein the identification unit sets the end point of the second section according to the start point of a third section in which the subject continues to look at the first object for a predetermined period of time after the start point of the second section.

[0011] [5] The determination device according to any one of [1] to [4], wherein the inspection image includes a plurality of second objects different from the first objects.

[0012] [6] The judgment unit judges that there is no abnormality in the cognitive function if the duration of the second interval is shorter than a predetermined duration, and judges whether there is an abnormality in the cognitive function depending on the pupil diameter in the second interval if the duration of the second interval is longer than the predetermined duration. [1] A judgment device according to any one of [1] to [5].

[0013] [7] The judgment unit judges that there is no abnormality in the cognitive function if the pupil diameter in the second interval is greater than a reference value, and judges that there is an abnormality in the cognitive function if the pupil diameter in the second interval is less than the reference value, and the reference value is a value corresponding to the maximum value. [3] The judgment device.

[0014] [8] The judgment unit judges that the patient has early dementia if the pupil diameter in the second interval is below the standard value and above a predetermined threshold, and judges that the patient has dementia that is more advanced than early dementia if the pupil diameter in the second interval is below the threshold, wherein the threshold is a value smaller than the standard value and is set according to the minimum value of the pupil diameter in the first interval. [7] The judgment device

[0015] [9] The determination device according to [8], wherein the threshold value is set according to the difference between the maximum value and the minimum value.

[0016]

[10] A detection device comprising an imaging device that generates a pupil image including the pupil of the subject, the pupil image being used to generate the time change acquired by the acquisition unit of the determination device of [1] to [9].

[0017]

[11] An inspection system comprising the determination device of [1] to [9] and the detection device of

[10] .

[0018]

[12] A control method implemented by a computer, comprising: acquiring a change in pupil diameter over time of a subject performing a task of finding a first object of interest from a test image including the first object; identifying a target interval from the change in time; and using the target interval to determine whether or not there is an abnormality in the subject's cognitive function; the change in time having an examination interval including a first interval representing the pupillary response to a change in light intensity from when the test image is displayed, and a second interval following the first interval until the first object is found; and the target interval being the second interval.

[0019]

[13] A program that causes a computer to function as an acquisition unit that acquires the change in pupil diameter over time of a subject performing a task of finding a first object of interest from an examination image containing the first object, an identification unit that identifies a target section from the change in time, and a judgment unit that uses the target section to determine whether there is an abnormality in the cognitive function of the subject, wherein the change in time has an examination section that includes a first section representing the pupil reaction due to a change in light intensity from the time the examination image is displayed, and a second section after the first section until the first object is found, and the target section is the second section. [Effects of the Invention]

[0020] The present invention makes it possible to determine with high accuracy whether or not there is an abnormality in cognitive function. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a configuration diagram of an inspection system according to an embodiment. [Figure 2] FIG. 1 is a configuration diagram of a head-mounted display according to an embodiment. [Figure 3] 10 is an example of an inspection image according to the embodiment. [Figure 4] FIG. 1 is a configuration diagram of a determination device according to an embodiment. [Figure 5] FIG. 2 is a block diagram illustrating a functional configuration of a determination device according to an embodiment. [Figure 6]10 shows a change in pupil diameter over time according to an embodiment. [Figure 7] 10 shows a change in pupil diameter over time focusing on an examination section according to an embodiment. [Figure 8] 10 is a flowchart of a determination process according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] 1 is a configuration diagram of an examination system 1 according to this embodiment. The examination system 1 is a computer system for determining whether or not there is an abnormality in the cognitive function of a subject U. The examination system 1 of this embodiment includes a head-mounted display (hereinafter referred to as "HMD100") and a determination device 200.

[0023] In summary, the examination system 1 of this embodiment identifies a change in pupil diameter over time of the subject U when a test image is displayed, and determines whether or not there is an abnormality in cognitive function using the change over time. In this embodiment, an example configuration is shown in which the test image is displayed by the HMD 100, and the cognitive function is determined by the determination device 200. The HMD 100 and the determination device 200 are connected to each other so as to be able to communicate with each other via wire or wirelessly.

[0024] The HMD 100 is a device worn over the eyes of the subject U, and displays information while blocking out the external environment. Figure 1 illustrates a case where the HMD 100 is a stationary type, and is used by the subject U by bringing it close to his / her face so that he / she looks into the HMD 100.

[0025] Fig. 2 is a configuration diagram of an example of the HMD 100. As illustrated in Fig. 2, the HMD 100 of this embodiment includes a control device 11, a storage device 12, a communication device 13, a display device 14, an imaging device 15, and a housing R (Fig. 1).

[0026] 1, the housing R in this embodiment has a shape that blocks the outside world by covering the field of view of the subject U. However, the shape of the HMD 100 and the structure for wearing it are not particularly limited, and for example, a glasses-type or goggle-type HMD 100 may also be used.

[0027] The control device 11 is one or more processors that control each element of the HMD 100. Specifically, the control device 11 is configured by one or more types of processors, such as a central processing unit (CPU), a graphics processing unit (GPU), a sound processing unit (SPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0028] The storage device 12 is a recording medium that stores programs executed by the control device 11 and various data used by the control device 11. For example, a known recording medium such as a semiconductor recording medium or a magnetic recording medium, or a combination of multiple types of recording media, is used as the storage device 12.

[0029] The communication device 13 is a communication device that communicates with the determination device 200. The communication device 13 of this embodiment transmits to the determination device 200 a pupil image G captured by an imaging device 15, which will be described later.

[0030] The display device 14 displays an image under the control of the control device 11. For example, a flat display such as a liquid crystal display panel or an organic EL (Electroluminescence) display panel is used as the display device 14. The display device 14 is provided inside the housing R so as to be positioned in front of both eyes of the subject U. The subject U then views the display device 14 by looking into the housing R. The test image may be a flat image or a stereoscopic image that allows a three-dimensional perception. A stereoscopic image is an image composed of an image for the right eye and an image for the left eye to which binocular parallax has been applied, and is an image in a so-called VR (Virtual Reality) space.

[0031] The display device 14 of this embodiment sequentially displays a preparatory image and a test image. The preparatory image is, for example, an image with only a black background (an image in which external light stimuli are sufficiently reduced), and is an image for stabilizing the pupil response of the subject. Looking at the preparatory image tends to stabilize the pupil diameter of the subject. For example, the preparatory image is displayed for 2 to 4 seconds. After displaying the preparatory image, the display device 14 displays the test image.

[0032] Fig. 3 is an example of an inspection image F. As illustrated in Fig. 3, the inspection image F of this embodiment includes one target first object M1 and multiple second objects M2 different from the first object M1. In the following description, when there is no need to distinguish between the first object M1 and the second object M2, they will simply be referred to as "object M."

[0033] The object M is, for example, a graphic or a character. Typically, the type of object M (graphic or character) is the same between the first object M1 and the second object M2. FIG. 3 illustrates an example in which the objects M are arranged in 7 columns and 7 rows. That is, the test image F includes one first object M1 and 48 second objects M2. For example, a plurality of objects M are arranged at predetermined intervals on a background of a color brighter than black (for example, white). Therefore, when displayed on the display device 14, the test image F will emit a greater amount of light than the preparation image.

[0034] In this embodiment, the object M is a ring-shaped figure (a so-called Landolt ring) with one notch cut out at each of the top, bottom, left, and right. The first object M1 and the second object M2 are Landolt rings with the notch cut out in different places. The subject is given the task of finding the first object M1 from among multiple objects M. The subject finds the first object M1 by moving their line of sight. After a preparatory image is displayed on the display device 14, the test image F is displayed, and the subject begins the task of finding the first object M1 from among multiple objects M.

[0035] The imaging device 15 is an imaging device (e.g., an infrared camera) that captures an image of the subject's pupil. The imaging device 15 generates a pupil image G that includes the subject's pupil. The imaging device 15 is installed inside the housing R at a position where it can capture an image of the subject's pupil. The pupil image G is transmitted to the determination device 200 via the communication device 13. The imaging device 15 continuously generates pupil images G at very short intervals while the preparatory image and the test image F are displayed, and transmits the pupil images G to the determination device 200. The HMD 100 is an example of a "detection device" that generates pupil images G used to acquire changes in pupil diameter over time.

[0036] In this embodiment, a configuration is illustrated in which a pupil image G is analyzed by a determination device 200 to identify the pupil diameter and gaze position of a subject. FIG. 4 is a configuration diagram of an example of the determination device 200. The determination device 200 is configured by an information device such as a smartphone, a tablet terminal, or a personal computer. The determination device 200 of this embodiment includes, for example, a control device 21, a storage device 22, a communication device 23, a display device 24, and an operation device 25.

[0037] The display device 24 displays an image under the control of the control device 21. For example, various display panels such as a liquid crystal display panel or an organic EL (Electroluminescence) panel are used as the display device 24. For example, a time series of pupil diameter is displayed by the display device 24. The operation device 25 is an input device that accepts instructions from the user of the determination device 200. The operation device 25 is, for example, a plurality of operators operated by the user, or a touch panel that detects contact by the user.

[0038] The storage device 22 is one or more memories that store programs executed by the control device 21 and various data used by the control device 21. The storage device 22 is configured from a known recording medium such as a magnetic recording medium or a semiconductor recording medium, or a combination of multiple types of recording media.

[0039] The control device 21 is a single or multiple processors that control each element of the determination device 200. Specifically, the control device 21 is configured with one or more types of processors, such as a central processing unit (CPU), a graphics processing unit (GPU), a sound processing unit (SPU), a digital signal processor (DSP), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC).

[0040] Fig. 5 is a block diagram illustrating an example of the functional configuration of the determination device 200. As illustrated in Fig. 5, the control device 21 of this embodiment realizes functions (an acquisition unit 211, an identification unit 213, and a determination unit 215) for determining whether or not there is an abnormality in cognitive function.

[0041] The acquisition unit 211 acquires the pupil diameter and gaze position of the subject. In this embodiment, the acquisition unit 211 acquires the pupil diameter and gaze position of the subject by identifying them from the pupil image G transmitted from the HMD 100. Any known image analysis technique or gaze tracking technique is used to identify the pupil diameter and gaze position. The pupil diameter and gaze position are continuously identified in a very short cycle. Therefore, the acquisition unit 211 acquires the change over time in pupil diameter and the change over time in gaze position.

[0042] FIG. 6 shows an example of the change in pupil diameter over time D(t) of a subject. As shown in FIG. 6, the change in pupil diameter over time D(t) includes a preparation interval Ta and an examination interval Tb, in this order. The examination interval Tb includes a target interval used to assess the cognitive function of the subject. The identification unit 213 of this embodiment identifies the target interval from the change in pupil diameter over time D(t). In practice, the change in pupil diameter over time D(t) is smoothed, and the following processing is performed by the identification unit 213 and the determination unit 215 on the smoothed change in pupil diameter over time D(t).

[0043] First, the preparation interval Ta is an interval corresponding to the interval in which the preparation image is displayed. In this embodiment, the preparation interval Ta is an interval representing the interval from time t0 when the display of the preparation image starts to time when the display of the preparation image ends (i.e., time t1 when the display of the inspection image F starts). Specifically, the preparation interval Ta is an interval whose start point is time t0 and whose end point is time t1.

[0044] As described above, the preparatory image is an image in which external light stimuli are reduced, and therefore, as illustrated in FIG. 6, the pupil diameter during the preparatory period Ta is stable with little change.

[0045] The test section Tb is a section from when the test image F is displayed until the test subject finds the first object M1. In this embodiment, the test section Tb represents a section from time t1 when the display of the test image F begins to time t2 when the test subject finds the first object M1. Specifically, the test section Tb is defined as a section whose starting point is time t1 and whose ending point is time t2.

[0046] When switching from the preparatory image to the test image F, the amount of light generated by the display device 14 changes. Therefore, the subject experiences a pupillary response in response to the change in light amount. As illustrated in FIG. 6, the test period Tb includes a first period T1 that represents the pupillary response associated with the change in light amount after the test image F is displayed. In the pupillary response of this embodiment, the test image F generates a greater amount of light than the preparatory image, and therefore a pupillary light reflex occurs, causing the pupil diameter to contract. Then, after contracting due to the pupillary light reflex, the pupil diameter gradually expands and then stabilizes (i.e., the pupillary response weakens). The first period T1 of this embodiment represents the above pupillary response.

[0047] Specifically, the first section T1 is the section from time t1 when the display of the test image F starts to time tw when the change in pupil diameter (contraction and expansion) due to the pupillary response stabilizes. The first section T1 includes time tmin when the pupil diameter reaches its minimum value due to the pupillary light reflex in the test section Tb.

[0048] Next, the test section Tb includes a second section T2 after the first section T1, during which the test subject finds the first object M1. Specifically, the second section T2 includes the time t2 at which the first object M1 is found. In this embodiment, the second section T2 is a section from the time tw at which the pupil diameter stabilizes to the time t2 at which the first object M1 is found.

[0049] Here, the first section T1 of the test section Tb is a section in which the pupil diameter changes unstably depending on the amount of light, making it difficult to see the test image F. Therefore, although the test image F is displayed, this section cannot be said to be a section in which the test subject is concentrating to find the first object M1. Therefore, the identification unit 213 identifies the second section T2, which follows the first section T1 of the test section Tb, as the target section. In other words, the second section T2 is a section in which the test subject is concentrating to find the first object M1.

[0050] An example of a method for identifying the second interval T2 from the change in pupil diameter over time D(t) will be described below. The identification unit 213 of this embodiment identifies the second interval T2 (target interval) starting from the time tw when the change in pupil diameter due to the pupillary response stabilizes and ending at the time t2 when the first object M1 is found.

[0051] First, the identification unit 213 identifies the time tmin at which the pupil diameter reaches its minimum value after time t1 when the display of the test image F begins, and then identifies the time at which the pupil diameter reaches its first maximum value after time tmin as time tw. Any known method can be used to identify the maximum value. For example, if the sign of the slope at a point immediately before a critical point where the slope is 0 is positive and the sign of the slope at a point immediately after the critical point is negative, the critical point is determined to be the maximum value.

[0052] Next, the identification unit 213 determines the start point of a fixation interval Tc after the start point (time tw) of the second interval T2 as time t2. The fixation interval Tc (an example of the "third interval") is an interval during which the subject continues to look at the first object M1 for a predetermined time (for example, 2 to 5 seconds). Once the subject finds the first object M1, the subject usually stares at the first object M1. Therefore, the start point of the fixation interval Tc corresponds to time t2 when the first object M1 is found. The length of time the subject continues to look at the first object M1 can be identified using the gaze position acquired by the acquisition unit 211.

[0053] The determination unit 215 determines whether or not there is an abnormality in cognitive function using the second interval T2 (target interval). FIG. 7 shows an example of the change in pupil diameter over time D(t) focusing on the test interval Tb (first interval T1, second interval T2). Here, if there is no abnormality in cognitive function (i.e., if the subject is healthy), the pupil diameter tends to expand in the second interval T2. On the other hand, if there is an abnormality in cognitive function (i.e., if the subject has dementia), the pupil diameter tends to contract in the second interval T2. For convenience, FIG. 7 illustrates the change in pupil diameter over time D(t) in the second interval T2 for both a healthy subject and a dementia subject.

[0054] Furthermore, for example, a young, healthy person may find the first object M1 before they start concentrating and their pupil diameter expands.

[0055] Taking the above into consideration, the identification unit 213 of this embodiment first determines whether or not there is an abnormality in cognitive function based on the duration of the second interval T2. Specifically, if the duration of the second interval T2 is shorter than a predetermined duration (hereinafter referred to as the "designated duration"), it is determined that there is no abnormality in cognitive function. On the other hand, if the duration of the second interval T2 exceeds the designated duration, it is determined whether or not there is an abnormality in cognitive function based on the time change D(t) in the second interval T2. In other words, if the duration of the second interval T2 is shorter than the designated duration, it is determined that the subject is healthy, regardless of whether the pupil diameter is tending to dilate or contract during the second interval T2. The designated duration is set to, for example, 5 to 15 seconds, preferably 7 to 12 seconds, and more preferably 9 to 11 seconds.

[0056] If the duration of the second interval T2 exceeds the specified duration, the judgment unit 215 judges that there is no abnormality in cognitive function if the pupil diameter in the second interval T2 exceeds the reference value, and judges that there is an abnormality in cognitive function if the pupil diameter in the second interval T2 is below the reference value.

[0057] In this embodiment, the pupil diameter in the second interval T2 (the pupil diameter to be compared with the reference value) is the average value for the second interval T2. The method for calculating the average value for the second interval T2 is not particularly limited, and may differ depending on whether the pupil diameter data is discrete or continuous.

[0058] The reference value to be compared with the pupil diameter in the second interval T2 is, for example, a value corresponding to the pupil diameter (i.e., the maximum value Dw) at the start point (time tw) of the second interval T2. In this embodiment, the maximum value Dw is used as the reference value.

[0059] In this embodiment, when the pupil diameter in the second section T2 is below a reference value, it is further determined whether the dementia is in an early stage or dementia more advanced than the early stage. Note that Fig. 7 separately shows the time change D(t) for early dementia (early stage) and dementia more advanced than the early stage (mid-stage or later). Specifically, when the pupil diameter in the second section T2 is below a reference value (maximum value Dw) and exceeds a predetermined threshold, the determination unit 215 determines that the dementia is in an early stage, and when the pupil diameter in the second section T2 is below the threshold, it determines that the dementia is more advanced than the early stage.

[0060] The threshold value to be compared with the pupil diameter in the second section T2 is a value smaller than the reference value and is set according to the minimum value Dmin of the pupil diameter in the first section T1. In this embodiment, the threshold value is set to a value between the maximum value Dw and the minimum value Dmin. Specifically, the threshold value is set according to the difference between the maximum value Dw and the minimum value Dmin. For example, the threshold value is set to a value (Dw-(Dw-Dmin)×α) obtained by subtracting a predetermined percentage of the difference between the maximum value Dw and the minimum value Dmin from the maximum value Dw. α is a value greater than 0 and less than 1, for example, 0.1 to 0.45, and preferably 0.15 to 0.3. In this embodiment, α is set to 0.2.

[0061] The assessment of cognitive function described above is performed multiple times (for example, three times). That is, the test image F is displayed three times, and the time change D(t) of the pupil diameter is identified and the cognitive function is assessed each time the test image F is displayed. Note that a different test image F is used for each assessment of cognitive function. For example, test images F in which the position of the first object M1 is different are used. Furthermore, a preparatory image may be displayed each time the test image F is displayed.

[0062] The final assessment is made using the three cognitive function assessment results (healthy / early dementia / mid-stage or later dementia). For example, if the same assessment result is obtained two or more times out of the three, that assessment result will be used as the final assessment of cognitive function. If the first assessment shows a healthy individual, the second assessment shows early dementia, and the third assessment shows a healthy individual, the final assessment will be a healthy individual.

[0063] 8 is a flowchart showing an example of a process (hereinafter referred to as "determination process") executed by the control device 21 of the determination device 200. The determination process is a process for determining whether or not there is an abnormality in the cognitive function of the subject. The determination process is started, for example, when a preparatory image is displayed after the subject wears the HMD 100.

[0064] For example, an instruction signal instructing the display of images (preparatory image, test image F) is transmitted from the determination device 200 to the HMD 100 in response to an operation of the operation device 25 by an administrator of the determination device 200. Then, upon receiving the instruction signal, the HMD 100 sequentially displays the preparatory image and test image F.

[0065] When the determination process starts, the control device 21 acquires a pupil image G from the HMD 100 via the communication device 23 (Sa1). The acquisition unit 211 of the control device 21 acquires the pupil diameter and gaze position from the acquired pupil image G (Sa2). The pupil diameter and gaze position are identified by various processes (e.g., image analysis) on the pupil image G.

[0066] The processing of step Sa1 (processing to acquire pupil image G) and the processing of step Sa2 (processing to acquire pupil diameter and gaze position) are repeatedly executed in a very short cycle until it is determined that the subject has found the first object M1 (Sa3; YES). By repeatedly executing steps Sa1 and Sa2, the change in pupil diameter over time D(t) (FIG. 6) is generated. When it is detected from the gaze position that the subject has continued to look at the first object M1 for a predetermined time (3 seconds), it is determined that the subject has found the first object M1. In other words, when the gaze position does not change from the first object M1 for 3 seconds, it is determined that the subject has found the first object M1. Steps Sa1-Sa3 are executed in parallel with the display of the preparation image and test image F on the HMD 100.

[0067] The change in pupil diameter over time D(t) obtained by repeating steps Sa1 and Sa2 includes a preparation period Ta, a test period Tb, and a fixation period Tc, as illustrated in FIG. 6. The preparation period Ta is the period during which a preparation image is displayed. The test period Tb (first period T1, second period T2) is the period from when the test image F is displayed until the subject finds the first object M1. The first period T1 is the period representing the pupillary response to changes in light intensity, and the second period T2 is the period during which the subject is concentrating to find the first object M1. The fixation period Tc is the period during which the subject continues to look at the first object M1 for a predetermined period of time (3 seconds).

[0068] Next, the identification unit 213 identifies a second interval T2 (target interval) from the change in pupil diameter over time D(t) (Sa4). Specifically, the second interval T2 is identified, starting from time tw when the change in pupil diameter due to pupillary response stabilizes, and ending from time t2 when the first object M1 is found. The method for identifying time tw and time t2 is as described above.

[0069] If the duration of the second interval T2 is less than the specified duration (Sa5; YES), the determination unit 215 determines that the subject is a healthy individual (Sa6). On the other hand, if the duration of the second interval T2 is greater than the specified duration (Sa5; NO), the determination unit 215 identifies the pupil diameter for the second interval T2 (Sa7). In this embodiment, the pupil diameter for the second interval T2 is the average value for the second interval T2.

[0070] If the pupil diameter in the second interval T2 exceeds the reference value (maximum value Dw at time tw) (Sa8; YES), the determination unit 215 determines that the subject is a healthy individual (Sa6). On the other hand, if the pupil diameter in the second interval T2 is below the reference value (Sa8; NO), the determination unit 215 determines whether the pupil diameter in the second interval T2 exceeds a predetermined threshold (Sa9).

[0071] If the pupil diameter in the second section T2 exceeds a predetermined threshold (Sa9; YES), the determination unit 215 determines that the subject has early-stage dementia (Sa10). On the other hand, if the pupil diameter in the second section T2 is below a predetermined threshold (Sa9; NO), the determination unit 215 determines that the subject has dementia that is more advanced than early stage (Sa11). Note that the predetermined threshold is set according to the minimum value Dmin of the examination section Tb (first section T1), as described above.

[0072] The determination process exemplified above is repeated multiple times (three times). Note that the process of steps Sa1-Sa3 may be executed three times prior to the process of step Sa4 and subsequent steps, and the process of step Sa4 and subsequent steps may be executed together at a later time. In this configuration, the discovery of the first object M1 (Sa3; YES) triggers the display of the next test image F (or the preparatory image and test image F).

[0073] As can be understood from the above explanation, in this embodiment, in the test section Tb including the first section T1 representing the pupillary response to changes in light intensity and the second section T2 in which the subject is concentrating on finding the first object M1, the second section T2 is used to assess cognitive function. In a configuration in which cognitive function is assessed using the entire test section Tb (hereinafter referred to as the "comparative example"), cognitive function is assessed by taking into account the pupillary response to changes in light intensity. Therefore, cognitive function cannot be assessed with high accuracy. In contrast, in this embodiment, the second section T2 of the test section Tb is used to assess cognitive function, so cognitive function can be assessed with high accuracy.

[0074] In this embodiment, the end point of the second section T2 is set according to the start point of the fixation section Tc in which the subject continues to look at the first object M1 for a predetermined period of time, so that the second section T2 used to assess cognitive function can be appropriately identified.

[0075] If the duration of the second interval T2 is shorter than the specified time length, it is determined that there is no abnormality in cognitive function, and if the duration of the second interval T2 is longer than the specified time length, cognitive function is determined based on the change in pupil diameter over time D(t) in the second interval T2.This embodiment has the advantage that it can properly determine cognitive function even for subjects who quickly find the first object M1 before the pupil diameter changes in the second interval T2.

[0076] Furthermore, if the pupil diameter in the second section T2 exceeds the standard value, it is determined that there is no abnormality in cognitive function, and if the pupil diameter in the second section T2 is below the standard value, it is determined that there is an abnormality in cognitive function.Therefore, taking into account the tendency for pupil diameter changes to differ between healthy individuals and people with dementia, cognitive function can be determined with high accuracy.

[0077] Here, the size of pupil diameter varies from person to person, and the amount of change in pupil diameter (expansion / constriction) also varies from person to person. This embodiment employs a configuration in which cognitive function is assessed by comparing the pupil diameter in the second interval T2 with a threshold set according to the minimum value Dmin. This configuration allows a threshold to be set for each subject, thereby reducing the influence of individual differences in pupil diameter and enabling more accurate assessment of cognitive function compared to, for example, using a common threshold across subjects. This embodiment, in particular, has the advantage that the threshold is set according to the difference between the maximum value Dw and the minimum value Dmin, allowing a threshold to be set that appropriately reflects the change characteristics of pupil diameter for each subject. However, the present invention also includes a configuration in which a common threshold is used across subjects.

[0078] <Modification> The above-described exemplary embodiments can be modified in various ways. Specific modified embodiments that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate to the extent that they are not mutually contradictory.

[0079] (1) Each object M is not limited to a Landolt ring. The object M may be, for example, any figure or character other than a Landolt ring. Furthermore, the first object M1 and the second object M2 may have, for example, a common figure or character and differ only in color.

[0080] (2) The number of first objects M1 is typically one, but may be two or more. However, the number of first objects M1 is less than the number of second objects M2. Note that if the number of second objects M2 is too small, there is a possibility that no change in pupil diameter will occur, particularly in healthy individuals. Therefore, from the perspective of assessing cognitive function with high accuracy, for example, 10 or more objects are preferable, and 40 or more objects are more preferable. Furthermore, the test image F may include objects other than the first object M1 and the second object M2.

[0081] (3) As long as the test image F contains a first object M1 (i.e., the target object), the second object M2 is not required. For example, an animal may be found as the first object M1 in a test image F depicting a streetscape. However, test image F, which contains a first object M1 and multiple second objects M2 different from the first object M1, has the advantage of being a simple image, which reduces the influence of each subject's visual characteristics (e.g., difficult-to-see colors) and allows cognitive function to be assessed.

[0082] (4) In the second section T2, it is sufficient that the start point is a time point that is substantially time tw and the end point is a time point that is substantially time t2. In other words, as long as it does not affect the assessment of cognitive function, it is not necessary for time tw to exactly coincide with the start point and time t2 to exactly coincide with the end point. In the second section T2, the start point may be a point immediately (just before or just after) time tw, and the end point may be a point immediately before time t2. As can be understood from the above explanation, it is sufficient that the start point of the second section T2 is set according to time tw, and the end point of the second section T2 is set according to time tw.

[0083] (5) The pupil diameter in the second interval T2 (the pupil diameter to be compared with the reference value) is not limited to the average value in the second interval T2. For example, the pupil diameter at any time point in the second interval T2 (e.g., time point t2) may be used. Cognitive function may also be assessed based on the change in pupil diameter in the second interval T2 (e.g., pupil diameter at time point tw - pupil diameter at time point t2).

[0084] (6) In the above-described embodiment, when there is an abnormality in cognitive function, the abnormality is classified into one of two stages (early dementia, dementia more advanced than early dementia), but the classification method is not limited to the above example. For example, the abnormality in cognitive function may be classified into more detailed stages (e.g., very early, early, middle, and late). Similarly, even when there is no abnormality in cognitive function, the abnormality may be classified into one of multiple stages.

[0085] (7) A configuration may also be adopted in which the pupil diameter and gaze position are identified from the pupil image G in the HMD 100. In the above configuration, the change in pupil diameter over time D(t) is generated in the HMD 100, and the acquisition unit 211 functions as an element that acquires the change in pupil diameter over time D(t) from the HMD 100 via communication.

[0086] (8) In the above embodiment, a configuration in which a preparatory image and a test image F are displayed on the display device 14 of the HMD 100 is exemplified, but the device used to display the preparatory image and the test image F is not limited to the HMD 100. For example, the preparatory image and the test image F may be displayed on a monitor display device. However, a configuration in which the preparatory image and the test image F are displayed by the HMD 100 makes it possible to obtain the change in pupil diameter over time D(t) while reducing the effects of ambient light, etc. Furthermore, the imaging device that generates the pupil image G may be integrated with or separate from the device equipped with the display device that displays the preparatory image and the test image F.

[0087] (9) In the above-described embodiment, it is not essential to display a preparatory image. However, if the preparatory image is displayed and then the test image F is displayed, the test image F can be displayed after the pupil has settled.

[0088] (10) In the above-described embodiment, the first section T1 included a pupillary response due to a light reflex, but the pupillary response due to changes in the amount of light included in the first section T1 differs depending on the type of test image F and the external environment.

[0089] (11) "Changes in pupil diameter over time of the subject" includes not only the changes in pupil diameter over time itself, but also the changes in various information (such as pupil area) over time that change in conjunction with pupil diameter.

[0090] (12) The functions of the inspection system according to each of the above-described aspects are realized by cooperation between a computer (e.g., a control device) and a program. A program according to a preferred aspect of the present invention is provided in a form stored on a computer-readable recording medium and installed on a computer. The recording medium is, for example, a non-transitory recording medium, and a good example is an optical recording medium (optical disk) such as a CD-ROM, but also includes any known type of recording medium, such as a semiconductor recording medium or a magnetic recording medium. Note that a non-transitory recording medium includes any recording medium except for a transient, propagating signal, and does not exclude volatile recording media. The program may also be provided to a computer in the form of distribution via a communication network. [Explanation of symbols]

[0091] 1: Inspection system 11: Control device 12:Storage device 13: Communication equipment 14:Display device 15: Imaging device 21: Control device 22: Storage device 23: Communication equipment 24:Display device 25: Operating device 100: HMD 200: Judgment device 211: Acquisition Department 213: Specific part 215: Judgment section Dmin: Minimum value Dw: maximum value F: Inspection image G: Pupil image M1: First object M2: Second object R: Housing T1: First section T2: Second section Ta: Preparation section Tb: Test section Tc: fixation interval U: Subject

Claims

1. an acquisition unit that acquires a change in pupil diameter over time of a subject who executes a task of finding a first object of interest from an examination image including the first object; an identification unit that identifies a target section based on the time change; a determination unit that determines whether or not there is an abnormality in the cognitive function of the subject using the target section, the time change includes an examination period including a first period representing a pupillary reaction due to a change in light amount from when the examination image is displayed, and a second period following the first period until the first object is found, The target section is the second section. Judgment device.

2. The inspection image is displayed on a display device of a head-mounted display. The determination device of claim 1.

3. the first section includes a time point at which the pupil diameter becomes a minimum due to a light reflex in the examination section, The specifying unit sets a time point at which the pupil diameter first reaches a maximum value after a time point at which the pupil diameter reaches a minimum value as a start point of the second interval. The determination device of claim 1.

4. The identification unit sets an end point of the second section according to a start point of a third section in which the subject continues to look at the first object for a predetermined time after the start point of the second section. The determination device of claim 1.

5. The inspection image includes a plurality of second objects different from the first objects. The determination device of claim 1.

6. The determination unit If the time length of the second section is shorter than a predetermined time length, it is determined that there is no abnormality in the cognitive function; If the time length of the second interval exceeds the predetermined time length, whether or not there is an abnormality in the cognitive function is determined based on the pupil diameter during the second interval. The determination device of claim 1.

7. The determination unit If the pupil diameter in the second section exceeds a reference value, it is determined that there is no abnormality in the cognitive function; If the pupil diameter in the second interval is less than the reference value, it is determined that there is an abnormality in the cognitive function; The reference value is a value corresponding to the maximum value. The determination device of claim 3.

8. The determination unit When the pupil diameter in the second section is less than the reference value, If the pupil diameter in the second interval is less than the reference value and greater than a predetermined threshold, it is determined that the subject has early-stage dementia; If the pupil diameter in the second section is below the threshold, it is determined that the dementia is more advanced than the early stage. The threshold value is a value smaller than the reference value and is set in accordance with the minimum value of the pupil diameter in the first section. The determination device of claim 7.

9. The threshold value is set according to the difference between the maximum value and the minimum value. The determination device of claim 8.

10. The determination device of claim 1 an imaging device for generating a pupil image including the pupil of the subject, the pupil image being used to generate the time change acquired by an acquisition unit of the determination device; An inspection system comprising:

11. acquiring a change in pupil diameter over time of a subject performing a task of finding a first object from a test image including the first object; Identifying a target section from the time change; Using the target section, determine whether or not there is an abnormality in the cognitive function of the subject; the time change includes an examination period including a first period representing a pupillary reaction due to a change in light amount from when the examination image is displayed, and a second period following the first period until the first object is found, The target section is the second section. A computer-implemented determination method.

12. an acquisition unit that acquires a change in pupil diameter over time of a subject performing a task of finding a first object of interest from an examination image including the first object; an identification unit that identifies a target section based on the time change; and causing a computer to function as a determination unit that determines whether or not there is an abnormality in the cognitive function of the subject using the target section; the time change includes an examination period including a first period representing a pupillary reaction due to a change in light amount from when the examination image is displayed, and a second period following the first period until the first object is found, The target section is the second section. program.

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