Eye movement examination device

Abstract

The present invention discloses an eye movement examination device, which is characterized by comprising a display module; a near-infrared image capturing module; an eye movement point calculation module; an average pursuit deviation calculation module; a total number of rapid eye movement calculation module; a total amplitude of rapid eye movement calculation module; a smooth pursuit eye movement examination result judgment module. The beneficial effects of the present invention are as follows: it can accurately record eye movement data, and can perform automated data statistics and data analysis on the data of eye movement examination, helping doctors to classify the eye movement examination results more objectively and accurately.

Description

Technical Field

[0001] The present invention relates to the field of medical devices, and particularly to an eye movement examination device based on near-infrared eye movement technology. Background Art

[0002] In clinical eye movement examinations, smooth pursuit eye movement (SPEM) is an important examination item. Smooth pursuit, also known as smooth tracking, smooth following, steady tracking, or steady eye tracking, is the process of using the eye's line of sight to follow the movement of a smoothly moving object, reflecting the function of the neural conduction pathway of the visual tracking system.

[0003] The methods for recording eye movement data mainly include the electrode method and the near-infrared video method. In the electrode method, several electrodes are attached around the eyeball. When the eyeball moves, the electric field formed by the potential difference between the cornea and the retina changes in spatial phase, thereby generating a cornea-retina potential, which is recorded by the electrodes and plotted as a waveform, so as to record the trajectory of the eyeball movement. The near-infrared video method is to use a near-infrared camera in cooperation with a near-infrared light source to capture images of the eyes, and record the trajectory of the eyeball movement by analyzing the change in the position of the pupil. In recent years, due to the convenience of the latter, the eye movement recording method based on near-infrared video has gradually become the mainstream technology.

[0004] Currently, the analysis of smooth pursuit eye movement data is still a relatively difficult problem. The commonly used method now is to draw the movement trajectory diagram of the target point and the movement trajectory diagram of the eye movement point at the same time, and the doctor observes and compares them by the naked eye, and makes a qualitative judgment according to the degree of coincidence of the two trajectory diagrams. If the degree of coincidence is good, it is judged as normal; if the degree of coincidence is poor, it is judged as abnormal. Or further, in the case where the degree of coincidence is poor, it is qualitatively subdivided into multiple levels such as slightly abnormal and severely abnormal according to the size of the coincidence error. Currently, this method relies relatively heavily on subjective experience, lacks objective quantitative data, and the judgment results of different people may vary, and it is not easy for new doctors to master. Summary of the Invention

[0005] The object of the present invention is to provide a device for eye movement examination and statistical analysis of the result data.

[0006] To achieve the above object, the technical solution of the present invention is to provide an eye movement examination device, which is characterized by comprising:

[0007] A display module capable of displaying a visual target, the visual target can move smoothly on the display module, the trajectory of the visual target movement is controlled by a program, and the position of the visual target at each moment is known. During the eye movement examination, it is required that the human eye follows the movement of the visual target point to look;

[0008] The near-infrared image capturing module includes at least one near-infrared camera and at least one near-infrared light source, and is capable of continuously capturing images containing at least one human eye;

[0009] The eye movement point calculation module is capable of calculating, through image processing algorithms, the eye images captured by the near-infrared image capturing module to obtain the coordinates of the eye movement points corresponding to each frame of the eye image. Each frame of eye movement point data includes the image acquisition time of this frame and the coordinates of the eye movement points corresponding to this frame of image;

[0010] The average pursuit deviation calculation module is used to calculate the average pursuit deviation Z; after the start of the test, calculate the distance between the coordinates of the eye movement points and the coordinates of the visual target at the corresponding time in each frame of eye movement point data, and accumulate it during the test. After the end of the test, obtain the total deviation distance L. Let the number of frames of the total eye movement point data in this test be M, then Z = L÷M;

[0011] The total number of rapid eye movements calculation module is used to calculate the total number of rapid eye movements C; after the start of the test, calculate the eye movement speed of each frame of eye movement point data in chronological order. For the Nth frame of eye movement point data, define the distance between the coordinates of the eye movement points in the current frame of eye movement point data and the coordinates of the eye movement points in the (N - 1)th frame of eye movement point data as the eye movement distance of the current frame of eye movement point data. Let Δt be the time interval between the image acquisition time of the current frame of eye movement point data and the image acquisition time of the (N - 1)th frame of eye movement point data, and define the eye movement speed of the current frame of eye movement point data as equal to the eye movement distance of the current frame of eye movement point data divided by Δt; set a speed threshold V and a distance threshold D. When the eye movement speed of a certain frame of eye movement point data is greater than V, define the current frame of eye movement point data as a frame of rapid eye movement point data. When the eye movement speed of a certain frame of eye movement point data is less than or equal to V, define the current frame of eye movement point data as a frame of slow eye movement point data; if there are several consecutive frames of rapid eye movement point data between two frames of slow eye movement point data, and the sum of the eye movement distances of these rapid eye movement point data is greater than D, it is recorded as one rapid eye movement, and the sum of the eye movement distances of these rapid eye movement point data is recorded as the amplitude of this rapid eye movement; if there is only one frame of rapid eye movement point data between two frames of slow eye movement point data, and the eye movement distance of this frame of rapid eye movement point data is greater than D, it is also recorded as one rapid eye movement, and the eye movement distance of this frame of rapid eye movement point data is recorded as the amplitude of this rapid eye movement; after the start of the test, accumulate the number of rapid eye movements, and at the end of the test, obtain the total number of rapid eye movements, which is called the total number of rapid eye movements C;

[0012] The total amplitude of rapid eye movements calculation module is used to calculate the total amplitude of rapid eye movements F; after the start of the test, accumulate the amplitude of each rapid eye movement, and at the end of the test, obtain the cumulative value of the total amplitude of rapid eye movements, which is called the total amplitude of rapid eye movements F;

[0013] The smooth pursuit eye movement examination result judgment module sets the judgment threshold PZ for Z, the judgment threshold PC for C, and the judgment threshold PF for F; when Z > PZ, or C > PC, or F > PF, it is judged that the smooth pursuit eye movement examination result is abnormal.

[0014] Preferably, the direction of the smooth movement of the visual target is the horizontal direction, moving along a straight line, and its moving speed is uniform.

[0015] Preferably, the direction of the smooth movement of the visual target is the horizontal direction, moving along a straight line, and its moving speed changes according to a sine function with time.

[0016] Preferably, the direction of the smooth movement of the visual target is the vertical direction, moving along a straight line, and its moving speed is uniform.

[0017] Preferably, the direction of the smooth movement of the visual target is the vertical direction, moving along a straight line, and its moving speed changes according to a sine function with time.

[0018] Preferably, the trajectory of the smooth movement of the visual target is a square, a rhombus, a circle or a Lissajous curve.

[0019] Preferably, the eye movement point coordinates in each frame of eye movement point data are decomposed into the X component in the horizontal direction and the Y component in the vertical direction, and the visual target coordinates corresponding to the time are also decomposed into the X component in the horizontal direction and the Y component in the vertical direction; the Z values, C values, and F values on the X component and the Y component are calculated respectively.

[0020] Preferably, it further includes an automatic blink filtering module, which can automatically judge blinks, filter out abnormal eye movement point data during blinks, and fit the eye movement point data during blinks with the eye movement point data before and after blinks.

[0021] Preferably, the automatic blink filtering module calculates the size of the pupil in real time and detects the presence or absence of the corneal reflection point; when it is detected that the pupil area of a certain frame of image is smaller than the threshold B compared with the pupil area of the previous frame of image, it is recorded as event M1; when it is detected that the corneal reflection point disappears, it is recorded as event M2; when the corneal reflection point can be detected again, it is recorded as event M3; when the pupil area returns to be greater than the threshold B, it is recorded as event M4; when events M1, M2, M3, and M4 occur in sequence within any continuous 500 ms, it is judged as a blink, and the time between M1 and M4 is recorded as the blink time.

[0022] Preferably, a distance threshold W is set, where W > D. If the amplitude of a certain rapid eye movement is greater than D and less than or equal to W, this rapid eye movement is defined as a rapid eye movement with a relatively small amplitude; if the amplitude of a certain rapid eye movement is greater than W, this rapid eye movement is defined as a rapid eye movement with a relatively large amplitude; the total number of rapid eye movements with relatively small amplitudes and the total amplitude of rapid eye movements with relatively small amplitudes are counted, and the total number of rapid eye movements with relatively large amplitudes and the total amplitude of rapid eye movements with relatively large amplitudes are counted.

[0023] Preferably, it further includes an auxiliary display that can display the eye image, the target coordinates, and the eye movement point coordinates in real time.

[0024] The beneficial effects of the present invention are as follows: It can accurately record eye movement data, and can perform automated data statistics and data analysis on the data of eye movement examinations, helping doctors to classify the results of eye movement examinations more objectively and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a function image of the target displacement changing with time (target trajectory diagram);

[0026] Figure 2 is the eye movement trajectory diagram of Subject A;

[0027] Figure 3 is the eye movement trajectory diagram of Subject B;

[0028] Figure 4 is the eye movement trajectory diagram of Subject C;

[0029] Figure 5 is the eye movement trajectory diagram of Subject D;

[0030] Figure 6 is the eye movement trajectory diagram of Subject E;

[0031] Figure 7 is the eye movement trajectory diagram of Subject F;

[0032] Figure 8 is the eye movement trajectory diagram of Subject G. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0034] An eye movement examination device disclosed in this embodiment includes a display module, a near-infrared image capturing module, an eye movement point calculation module, an average pursuit deviation calculation module, a total number of rapid eye movement calculation module, a total amplitude of rapid eye movement calculation module, and a smooth pursuit eye movement examination result judgment module. It also includes an electronic computer. The eye movement point calculation module, the average pursuit deviation calculation module, the total number of rapid eye movement calculation module, the total amplitude of rapid eye movement calculation module, and the smooth pursuit eye movement examination result judgment module are programs running on this electronic computer. In this embodiment, the display module is a display connected to the electronic computer, which can display a smoothly moving visual target for the subject to view. Additionally, this embodiment also includes an auxiliary display, which can display information such as the subject's eye image, visual target coordinates, eye movement point coordinates, and statistical analysis of eye movement examination data in real time, for doctors to view the process and results of the eye movement examination in real time.

[0035] In this embodiment, the near-infrared image capturing module includes 1 near-infrared camera and 2 near-infrared light sources. The 2 near-infrared light sources are located on both sides of the near-infrared camera. The near-infrared camera and the near-infrared light sources are placed inside the casing, below the display module. The near-infrared camera is connected to the electronic computer through a USB data cable. The eye movement point calculation module is a program running on the electronic computer, which can perform real-time image processing on the eye image captured by the near-infrared image capturing module and calculate the eye movement point coordinates in real time. In this embodiment, the near-infrared camera in the near-infrared image capturing module is set to capture 100 frames of eye images per second, that is, capture one frame of eye image every 10 ms. Correspondingly, the eye movement point calculation module calculates the eye movement point coordinates every 10 ms in real time. The calculated eye movement point coordinates can be displayed in real time on the auxiliary display for doctors, and are also saved in the computer's database for statistical analysis.

[0036] This embodiment uses a head fixation bracket to fix the subject's head during the eye movement examination, facilitating more accurate calculation results of the eye movement points.

[0037] According to different application scenarios, it is possible to only capture the image of a single eye and calculate the eye movement points of a single eye, or capture the images of both eyes and calculate the eye movement points of both eyes. This embodiment captures the images of both eyes and calculates the eye movement points of both eyes, and takes the average coordinates of the eye movement points of both eyes as the eye movement point coordinates.

[0038] In this embodiment, the basic principle of the image processing algorithm used by the eye movement point calculation module is as follows: Since the corneal reflection points captured by the near-infrared camera have high brightness and a gray level up to 255, and two corneal reflection points appear in pairs and are close in distance. According to this characteristic, the image areas where the left and right eyes are located can be found from the entire image captured by the near-infrared camera. A gray level threshold higher than the gray level of the pupil and lower than the gray levels of the surrounding iris and skin areas is set, and the areas below the gray level threshold are marked as possible pupil areas; then an area threshold is set to exclude the interference of smaller black objects such as eyelashes, so as to determine the accurate area where the pupil is located. According to the center of the left eye pupil area, the coordinates of the left eye pupil center are obtained; according to the average coordinates of the center coordinates of the two corneal reflection points of the left eye, the center coordinates of the left corneal reflection point are obtained. The coordinates of the left eye pupil center minus the coordinates of the left corneal reflection point obtain the pupil corneal vector of the left eye. Similarly, the pupil center coordinates of the right eye, the center coordinates of each corneal reflection point of the right eye, and the pupil corneal vector of the right eye can be obtained.

[0039] There is a one-to-one correspondence between the pupil corneal vector of the left eye of the subject and the left eye eye movement point coordinates on the display, which is called the left eye mapping function; there is a one-to-one correspondence between the pupil corneal vector of the right eye and the right eye eye movement point coordinates on the display, which is called the right eye mapping function.

[0040] This embodiment uses 9-point calibration. Calibration points are respectively displayed at 9 positions in the center, left, right, top, bottom, upper left, upper right, lower left, and lower right of the display. The positions of these 9 points are known and determined. After calibration of the left and right eyes respectively, the left eye mapping function and the right eye mapping function are obtained. The eye movement point calculation module can calculate the eye movement point coordinates of the left eye according to the left eye pupil corneal vector and substituting it into the left eye mapping function; according to the right eye pupil corneal vector and substituting it into the right eye mapping function, the eye movement point coordinates of the right eye can be calculated. In this embodiment, the coordinates of the eye movement point take the midpoint of the display as the origin (0, 0), the positive direction of the X-axis is to the right in the horizontal direction, and the positive direction of the Y-axis is upward in the vertical direction, with the unit being visual angle (degree). In other embodiments, when the distance between the display and the human eye is known, the visual angle can also be converted into pixels or length units on the display.

[0041] In another embodiment, a binocular camera system can be used in the near-infrared image capture module. The eye movement point calculation module calculates the three-dimensional visual axis through single-point calibration according to the binocular vision principle, and then calculates the intersection point of the visual axis and the display plane to obtain the eye movement point coordinates. This design scheme can complete calibration quickly and conveniently, and is suitable for some subjects who cannot complete 9-point calibration or other multi-point calibrations due to special reasons, such as patients with nystagmus, young children with difficulty concentrating, etc. The near-infrared image capture module can also select devices with a smaller volume and be integrated into a head-mounted device.

[0042] The specific process of eye movement examination is as follows:

[0043] (1) The subject sits in front of the eye movement examination device, places the chin on the head fixation bracket, and looks towards the monitor. The near-infrared image capture module is located directly below the monitor. The distance between the subject's two eyes and the monitor is 60 cm. The near-infrared camera in the near-infrared image capture module is set to capture 100 eye images per second, that is, one eye image is captured every 10 ms. After the 9-point calibration is completed, the eye movement point calculation module calculates the eye images captured by the near-infrared image capture module through an image processing algorithm to obtain the coordinates of the eye movement points corresponding to each frame of the eye image. Each frame of eye movement point data includes the acquisition time of this frame of image and the coordinates of the eye movement point corresponding to this frame of image.

[0044] (2) After the test starts, the computer controls the target on the monitor to move smoothly. Its smooth movement trajectory is continuous without interruption. The doctor can ask the subject to always follow the target to look through the instructions. In this embodiment, the target is a small black dot. In other embodiments, for young children with difficulty concentrating, the target can also be a brightly colored animation, such as a flying butterfly. In this embodiment, the target first starts to be displayed at the midpoint of the monitor screen, and then moves horizontally to the right at a constant speed of 8° / s. When it moves to 10° on the right, it moves horizontally to the left at a constant speed of 8° / s. When it moves to 10° on the left, it moves horizontally to the right at a constant speed of 8° / s again. When it returns to the midpoint, it is a cycle, and the time of each cycle is 5 seconds. After 20 seconds, that is, after 4 cycles of smooth movement in the horizontal direction, the target stops moving and the test ends. Taking time as the X-axis (unit: ms) and the horizontal displacement of the target as the Y-axis (the middle is the 0 point, the right is positive, and the left is negative, unit: visual angle °), the function image of the target displacement changing with time can be obtained, that is, the target trajectory graph, as Figure 1 shown, which is a triangular wave changing with time.

[0045] (3) Calculate and display the eye movement trajectory

[0046] In this embodiment, the total time for the target to move is 20 seconds. An eye movement point coordinate can be obtained every 10 ms. In these 20 seconds, 20,000 eye movement point coordinates can be obtained. Considering the intuitiveness of the display of the eye movement trajectory graph, with time as the X-axis and the horizontal component value of the eye movement point coordinate as the Y-axis value, connecting the horizontal component values of these 20,000 eye movement point coordinates can obtain a function graph of the horizontal component of the eye movement point coordinate changing with time, that is, the eye movement trajectory graph of the horizontal component changing with time. Generally speaking, when the target only moves in the horizontal direction, the vertical component of the eye movement point of the subject and the vertical component of the target coordinate do not differ much. Therefore, when the target only moves in the horizontal direction, the eye movement trajectory graph of the horizontal component of the eye movement point coordinate changing with time can be prominently displayed and analyzed. Similarly, if when the target only moves in the vertical direction, the horizontal component of the eye movement point of the subject and the horizontal component of the target coordinate do not differ much, the eye movement trajectory graph of the vertical component of the eye movement point coordinate changing with time can be prominently displayed and analyzed. If the target moves in both the horizontal and vertical directions, for example, the movement trajectory of the target is circular, the horizontal and vertical components of the eye movement trajectory can be simultaneously displayed and analyzed.

[0047] (4) Calculation of average pursuit deviation

[0048] The average pursuit deviation calculation module is a program running on a computer and is used to calculate the average pursuit deviation Z. After the test starts, that is, after the target starts to move, calculate the distance between the eye movement point coordinate in each frame of eye movement point data and the target coordinate at the corresponding time, and accumulate it during the test. After the test ends, the total deviation distance L is obtained. Let the number of frames of the total eye movement point data in this test be M, then Z = L÷M. In this embodiment, because the test time is 20 seconds and 100 frames of eye movement point data are obtained per second, the number of frames of the total eye movement point data M = 20,000.

[0049] (5) Calculation of the total number of rapid eye movements

[0050] The total number of rapid eye movement calculation module is a program running on a computer, which is used to calculate the total number of rapid eye movements C. After the start of the test, in chronological order, the eye movement speed of each frame of eye movement point data is calculated in turn. Starting from the second frame, for the eye movement point data of the Nth frame, the distance between the eye movement point coordinates of this frame of eye movement point data and the eye movement point coordinates of the (N - 1)th frame of eye movement point data is defined as the eye movement distance of this frame of eye movement point data. Let Δt be the time interval between the image acquisition time of this frame of eye movement point data and the image acquisition time of the (N - 1)th frame of eye movement point data. The eye movement speed of this frame of eye movement point data is defined as the eye movement distance of this frame of eye movement point data divided by Δt. In this embodiment, Δt between every two frames is a fixed time value of 10 ms; a speed threshold V is set, and a distance threshold D is set. When the eye movement speed of a certain frame of eye movement point data is greater than V, this frame of eye movement point data is defined as a frame of rapid eye movement point data. When the eye movement speed of a certain frame of eye movement point data is less than or equal to V, this frame of eye movement point data is defined as a frame of slow eye movement point data; if there are several consecutive frames of rapid eye movement point data between two frames of slow eye movement point data, and the sum of the eye movement distances of these eye movement point data is greater than D, it is recorded as one rapid eye movement, and the sum of the eye movement distances of these rapid eye movement point data is recorded as the amplitude of this rapid eye movement; if there is only one frame of rapid eye movement point data between two frames of slow eye movement point data, and the eye movement distance of this frame of rapid eye movement point data is greater than D, it is also recorded as one rapid eye movement, and the eye movement distance of this frame of rapid eye movement point data is recorded as the amplitude of this rapid eye movement. The first frame of eye movement point data at the start of the test can be specified as slow eye movement point data, and the last frame at the end of the test can be specified as slow eye movement point data. After the start of the test, the number of rapid eye movements is accumulated. At the end of the test, the total number of rapid eye movements is obtained, which is called the total number of rapid eye movements C.

[0051] The speed threshold V should be set to a value greater than the maximum smooth movement speed of the visual fixation point. In this embodiment, the smooth movement speed of the visual fixation point is 8° / second. Considering the influence of image processing measurement noise and the inherent minute jitter of the eye itself, generally speaking, the speed threshold V should be set to be more than 10° / second greater than the maximum smooth movement speed of the visual fixation point to prevent misjudging noise or the inherent minute jitter of the eye itself as rapid eye movement. In this embodiment, the speed threshold V = 30° / second is taken.

[0052] The setting of the distance threshold D should be greater than or equal to V multiplied by the image acquisition time interval. In this embodiment, V = 30° / second and the image acquisition time interval = 10 ms, so D should be set to a distance threshold greater than or equal to 0.3°. The smaller the value of D is set, the more likely the calculated number of rapid eye movements is; the larger the value of D is set, the less likely the calculated number of rapid eye movements is. Considering the limitation of the display resolution or printer resolution, rapid eye movements with a small amplitude are not easily recognizable by the naked eye. In this embodiment, the distance threshold D = 2° is taken.

[0053] In other embodiments, if the total number of rapid eye movements is divided by the test time, the number of rapid eye movements per unit time can be obtained, or the rapid eye movement frequency, which can be mutually converted with the total number of rapid eye movements and is equivalent. Similarly, if the visual target smoothly moves through several cycles, the average number of rapid eye movements per cycle can also be calculated, which can also be mutually converted with the total number of rapid eye movements and is equivalent.

[0054] (6) Calculation of the total amplitude of rapid eye movements

[0055] The module for calculating the total amplitude of rapid eye movements is a program running on a computer, used to calculate the total amplitude F of rapid eye movements. After the test starts, the amplitudes of each rapid eye movement are accumulated. At the end of the test, the accumulated value of the total amplitude of rapid eye movements is obtained, which is called the total amplitude of rapid eye movements.

[0056] In other embodiments, if the total amplitude of rapid eye movements is divided by the test time, the amplitude of rapid eye movements per unit time can be obtained, which can be mutually converted with the total amplitude of rapid eye movements and is equivalent. Similarly, if the visual target smoothly moves through several cycles, the average amplitude of rapid eye movements per cycle can also be calculated, which can also be mutually converted with the total amplitude of rapid eye movements and is equivalent.

[0057] (7) Judgment of the results of smooth pursuit eye movement examination

[0058] The module for judging the results of smooth pursuit eye movement examination is a program running on a computer, setting the judgment threshold PZ for the average pursuit deviation Z, setting the judgment threshold PC for the total number of rapid eye movements C, and setting the judgment threshold PF for the total amplitude F of rapid eye movements. When Z > PZ, or C > PC, or F > PF, it is judged that the results of the smooth pursuit eye movement examination are abnormal. When Z ≤ PZ, and C ≤ PC, and F ≤ PF, it is judged that the results of the smooth pursuit eye movement examination are within the normal range.

[0059] The average pursuit deviation Z reflects the average error between the eye movement point and the visual target during the smooth pursuit of the subject. If the value of Z is large, it often indicates that the subject cannot smoothly pursue the visual target accurately. The value range of the judgment threshold PZ for the average pursuit deviation Z is generally between 0.5° and 2.0°. If the smooth movement speed of the visual target is fast and the movement trajectory of the visual target is complex, a larger value can be taken for PZ; if the smooth movement speed of the visual target is slow and the movement trajectory is simple, a smaller value can be taken for PZ. In this embodiment, PZ is set to 1.2°.

[0060] The total number of rapid eye movements C quantitatively reflects the subject's ability to control the smooth pursuit speed of eye movements in terms of the number of times. If this value is large, it often indicates that the subject cannot smoothly pursue the fixation point stably, and the number of deviations is relatively large. The eye movement trajectory often shows more square waves or step waves, and sometimes appears as a gear-shaped waveform. The judgment threshold PC of the total number of rapid eye movements C is related to the test time, the smooth movement speed of the fixation point, the complexity of the fixation point movement trajectory, the speed threshold V, and the distance threshold D. When the test time is T seconds, if the smooth movement speed of the fixation point is slow, the fixation point movement trajectory is relatively simple, the speed threshold V is set high, and the distance threshold D is set high, PC can be set as low as T / 10 (times); if the smooth movement speed of the fixation point is fast, the fixation point movement trajectory is relatively complex, the speed threshold V is set low, and the distance threshold D is set low, PC can be set as high as 2T (times). In this embodiment, PC is set to 16 (times).

[0061] The total amplitude of rapid eye movements F quantitatively reflects the subject's ability to control the smooth pursuit speed of eye movements in terms of the amplitude. If this value is large, it often indicates that the subject cannot smoothly pursue the fixation point stably, and the amplitude of the deviation is relatively large. The eye movement trajectory often shows large-amplitude square waves or step waves. The judgment threshold PF of the total amplitude of rapid eye movements F is related to the test time, the smooth movement speed of the fixation point, the complexity of the fixation point movement trajectory, the speed threshold V, and the distance threshold D. When the test time is T seconds, if the smooth movement speed of the fixation point is slow, the fixation point movement trajectory is relatively simple, the speed threshold V is set high, and the distance threshold D is set high, PF can be set as low as T / 5 (degrees); if the smooth movement speed of the fixation point is fast, the fixation point movement trajectory is relatively complex, the speed threshold V is set low, and the distance threshold D is set low, PF can be set as high as 6T (degrees). In this embodiment, PF is set to 60°.

[0062] In this embodiment, taking the eye movement examination data of seven subjects, namely A, B, C, D, E, F, and G, as an example:

[0063] Figure 2 is the eye movement trajectory diagram of subject A;

[0064] Figure 3 is the eye movement trajectory diagram of subject B;

[0065] Figure 4 is the eye movement trajectory diagram of subject C;

[0066] Figure 5 is the eye movement trajectory diagram of subject D;

[0067] Figure 6 is the eye movement trajectory diagram of subject E;

[0068] Figure 7 It is the eye movement trajectory diagram of the subject Wu.

[0069] Figure 8 It is the eye movement trajectory diagram of the subject Geng.

[0070] Among them, the X-axis is time (unit: ms), and the Y-axis is the horizontal component of the eye movement point coordinates (unit: visual angle °). For the convenience of comparing the differences between the eye movement point coordinates and the target coordinates at each moment, the target trajectory diagram is also displayed simultaneously. The target trajectory diagram is the triangular wave in the figure. The data sheets of the smooth pursuit eye movement examination results of these seven subjects are shown in the following table:

[0071] Z (unit: degree) C (unit: times) F (unit: degree) Subject A 0.48 0 0 Subject B 0.81 8 25.16 Subject C 1.68 9 39.03 Subject D 0.67 21 56.41 Subject E 0.89 14 68.52 Subject F 1.72 11 75.97 Subject G 2.43 25 143.10

[0072] In this embodiment, the smooth pursuit eye movement examination result judgment module judges, according to the judgment method described above, that the smooth pursuit eye movement examination results of the subjects A and B are within the normal range; the smooth pursuit eye movement examination results of the subjects C, D, E, Wu, and Geng are abnormal. It can also be seen from the data sheet that among the subjects with abnormal smooth pursuit eye movement examination results, there is one with only a high Z value (subject C), one with only a high C value (subject D), one with only a high F value (subject E), one with two of the three results being high (Z and F values of subject Wu), and one with all three values of Z, C, and F being high (subject Geng). Thus, it can be seen that through these three examination data of Z, C, and F, it is possible to comprehensively judge whether the smooth pursuit eye movement examination results of the subject are abnormal.

[0073] In addition, during eye movement examination, if the duration is relatively long, some examinees will blink one or several times during the test. In this embodiment, an automatic blink filtering module is further included. The automatic blink filtering module is a program running on a computer, which can filter out abnormal eye movement point data during blinking, avoid misjudging blinking as rapid eye movement, and also avoid calculation errors of average pursuit deviation caused by coordinate deviation of eye movement points during blinking. The specific method is as follows: during blinking, first, the pupil of the eye will be partially blocked by the eyelid, then completely blocked, then partially blocked again, and finally the pupil will open and return to its normal size. According to statistics, the duration of blinking is generally within 500 ms. According to the principle of the image processing algorithm used by the aforementioned eye movement point calculation module, when blinking starts, when the two corneal reflection points of the eye are not blocked by the eyelid but the pupil is partially blocked, the pupil area will become smaller; then when the two corneal reflection points are completely blocked by the eyelid, the eye movement points cannot be calculated. The automatic blink filtering algorithm used in this embodiment can calculate the size of the pupil in real time. When it is detected that the pupil area of a certain frame of image is less than a certain threshold B compared with the pupil area of the previous frame of image, for example, less than 90% of the area S of the previous frame, it is recorded as event M1; when it is detected that the two corneal reflection points disappear, it is recorded as event M2; when the two corneal reflection points can be detected again, it is recorded as event M3; when the pupil area returns to more than 90% of S, it is recorded as event M4. When these four events M1, M2, M3, and M4 occur in sequence within any continuous 500 ms, it is determined as a blink, and the time between M1 and M4 is recorded as the blink time. The eye movement point data during the blink time will disappear or become abnormal. Therefore, according to the normal eye movement point data of the frame before and after the blink, linear interpolation can be performed during the blink time to fit the eye movement point data during the blink.

[0074] In this embodiment, the moving mode of the visual target is to move back and forth horizontally at a constant speed for 4 cycles, the speed is 8° / s, and the moving range is ±10°. In other embodiments, when the visual target moves horizontally at a constant speed, the number of moving cycles, the moving speed, the moving range, the starting point and the ending point of the movement can be set. The visual target can move back and forth horizontally for one or several cycles, or only move once, for example, move from -10° on the left to 10° on the right.

[0075] In other embodiments, the speed at which the visual target smoothly moves in the horizontal direction can also vary with time according to a sine function. For example, setting the moving speed v of the visual target as a function of time t, v(t) = Asin(ωt), with the midpoint of the display screen as the origin and the right direction as the positive direction, the starting position of the visual target is -A / ω (degrees), and then it starts to move to the right; the visual target moves fastest at the midpoint with a speed of A; when the visual target moves to A / ω (degrees) on the right side, the speed is 0 and it starts to move to the left; the period of the visual target's movement is 2π / ω (seconds). The number of periods of the visual target's movement, the moving speed, the moving range, the starting point and the ending point of the movement can be set. The visual target can move back and forth for one or several periods, or it can move only once, for example, from -A / ω (degrees) on the left side to A / ω (degrees) on the right side. The direction of the smooth movement of the visual target can also be a straight-line movement in the vertical direction, and the moving speed can be uniform or vary according to a sine function. The visual target can move up and down for one or several periods, or it can move only once.

[0076] The trajectory of the smooth movement of the visual target can also be a square, or a rhombus, or a circle, or a Lissajous curve. The visual target can move for one or several periods.

[0077] In other embodiments, a distance threshold W can also be set, where W > D. If the amplitude of a certain rapid eye movement is greater than W and less than or equal to D, this rapid eye movement is defined as a rapid eye movement with a relatively small amplitude; if the amplitude of a certain rapid eye movement is greater than W, this rapid eye movement is defined as a rapid eye movement with a relatively large amplitude; the total number of rapid eye movements with relatively small amplitudes and the total amplitude of rapid eye movements with relatively small amplitudes can be counted, and the total number of rapid eye movements with relatively large amplitudes and the total amplitude of rapid eye movements with relatively large amplitudes can be counted.

[0078] When performing an eye movement examination, the effective eye movement time and the ineffective eye movement time can be counted separately. The ineffective eye movement time is the time of blinking, closing the eyes, and looking at areas outside the display screen. The effective eye movement time is the total test time minus the ineffective eye movement time. If the ratio of the effective eye movement time to the total test time is lower than a certain threshold, such as 80%, it can be considered that the subject did not cooperate attentively in the eye movement examination and needs to do it again to obtain meaningful statistical results. For subjects with relatively low comprehension abilities, such as young children, if they cannot understand the instructions given by the doctor, they can first perform appropriate smooth pursuit eye movement exercises and then do the formal eye movement examination.

Claims

1. An eye movement examination device, characterized in that, Comprising: A display module capable of displaying a visual target, the visual target being able to move smoothly on the display module, the trajectory of the movement of the visual target being controlled by a program, the position of the visual target at each moment being known, and during eye movement examination, it is required that the human eye follow the movement of the visual target point to look; A near-infrared image capturing module, including at least one near-infrared camera and at least one near-infrared light source, capable of continuously capturing images containing at least one human eye; An eye movement point calculation module capable of calculating, through an image processing algorithm, the eye movement point coordinates corresponding to each frame of the eye image captured by the near-infrared image capturing module, and each frame of eye movement point data includes the image acquisition time of this frame and the eye movement point coordinates corresponding to this frame of image; An average pursuit deviation calculation module for calculating the average pursuit deviation Z; after the start of the test, calculate the distance between the eye movement point coordinates in each frame of eye movement point data and the visual target coordinates at the corresponding time, and accumulate it during the test process. After the end of the test, obtain the total deviation distance L. Let the total number of frames of eye movement point data in this test be M, then Z = L÷M; A rapid eye movement total number calculation module for calculating the total number of rapid eye movements C; after the start of the test, calculate the eye movement speed of each frame of eye movement point data in chronological order. For the Nth frame of eye movement point data, define the distance between the eye movement point coordinates of the current frame of eye movement point data and the eye movement point coordinates of the (N - 1)th frame of eye movement point data as the eye movement distance of the current frame of eye movement point data. Let Δt be the time interval between the image acquisition time of the current frame of eye movement point data and the image acquisition time of the (N - 1)th frame of eye movement point data, and define the eye movement speed of the current frame of eye movement point data as equal to the eye movement distance of the current frame of eye movement point data divided by Δt; set a speed threshold V and a distance threshold D. When the eye movement speed of a certain frame of eye movement point data is greater than V, define the current frame of eye movement point data as a frame of rapid eye movement point data. When the eye movement speed of a certain frame of eye movement point data is less than or equal to V, define the current frame of eye movement point data as a frame of slow eye movement point data; if there are several consecutive frames of rapid eye movement point data between two frames of slow eye movement point data, and the sum of the eye movement distances of these rapid eye movement point data is greater than D, it is recorded as one rapid eye movement, and the sum of the eye movement distances of these rapid eye movement point data is recorded as the amplitude of this rapid eye movement; if there is only one frame of rapid eye movement point data between two frames of slow eye movement point data, and the eye movement distance of this frame of rapid eye movement point data is greater than D, it is also recorded as one rapid eye movement, and the eye movement distance of this frame of rapid eye movement point data is recorded as the amplitude of this rapid eye movement; after the start of the test, accumulate the number of rapid eye movements, and at the end of the test, obtain the total number of rapid eye movements, which is called the total number of rapid eye movements C; A rapid eye movement total amplitude calculation module for calculating the total amplitude of rapid eye movements F; after the start of the test, accumulate the amplitude of each rapid eye movement, and at the end of the test, obtain the cumulative value of the total amplitude of rapid eye movements, which is called the total amplitude of rapid eye movements F; The smooth pursuit eye movement examination result judgment module sets the judgment threshold PZ for Z, the judgment threshold PC for C, and the judgment threshold PF for F; when Z > PZ, or C > PC, or F > PF, it is judged that the smooth pursuit eye movement examination result is abnormal.

2. The eye movement examination device according to claim 1, wherein The direction of the smooth movement of the visual target is the horizontal direction, moving along a straight line, and its moving speed is uniform.

3. The eye movement examination device according to claim 1, wherein The direction of the smooth movement of the visual target is the horizontal direction, moving along a straight line, and its moving speed changes according to the sine function over time.

4. The eye movement examination device according to claim 1, characterized in that The direction of the smooth movement of the visual target is the vertical direction, moving along a straight line, and its moving speed is uniform.

5. The eye movement examination device according to claim 1, characterized in that, The direction of the smooth movement of the visual target is the vertical direction, moving along a straight line, and its moving speed changes according to the sine function over time.

6. The eye movement examination device according to claim 1, characterized in that, The smooth movement trajectory of the visual target is a square, a rhombus, a circle or a Lissajous curve.

7. The eye movement examination device according to claim 1, characterized in that, Decompose the eye movement point coordinates in each frame of eye movement point data into the X component in the horizontal direction and the Y component in the vertical direction, and also decompose the visual target coordinates at the corresponding time into the X component in the horizontal direction and the Y component in the vertical direction; Calculate the Z value, C value, and F value on the X component and Y component respectively.

8. The eye movement examination device according to claim 1, wherein It also includes an automatic blink filtering module, which can automatically judge blinks, filter out abnormal eye movement point data during blinks, and fit the eye movement point data during blinks with the eye movement point data before and after blinks.

9. The eye movement examination device according to claim 8, characterized in that, The automatic blink filtering module calculates the size of the pupil in real time and detects the presence or absence of the corneal reflection point; when it is detected that the pupil area of a certain frame of image is less than the threshold B compared with the pupil area of the previous frame of image, it is recorded as event M1; When it is detected that the corneal reflection point disappears, it is recorded as event M2; When the corneal reflection point can be detected again, it is recorded as event M3; When the pupil area returns to be greater than the threshold B, it is recorded as event M4; when the four events M1, M2, M3, and M4 occur in sequence within any continuous 500 ms, it is judged as a blink, and the time between M1 and M4 is recorded as the blink time.

10. The eye movement examination device according to claim 1, wherein, Set a distance threshold W, W > D. If the amplitude of a certain rapid eye movement is greater than D and less than or equal to W, this rapid eye movement is defined as a rapid eye movement with a smaller amplitude; if the amplitude of a certain rapid eye movement is greater than W, this rapid eye movement is defined as a rapid eye movement with a larger amplitude; count the total number and total amplitude of rapid eye movements with a smaller amplitude, and count the total number and total amplitude of rapid eye movements with a larger amplitude.

11. The eye movement examination device according to claim 1, characterized in that, It also includes an auxiliary display, which can display the eye image, visual target coordinates, and eye movement point coordinates in real time.

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