Vision testing program, vision testing system, and vision testing method

Abstract

To provide a vision test program in which variations of vision evaluation by an examiner are eliminated by examination using hardware resources, an examination time is shortened as compared to a vision test by preferential looking, and thereby the accuracy of the vision test is improved, and provide a vision test system and a vision test method.SOLUTION: A vision test program is provided for making a computer function as means for displaying an eye target, and means for determining whether or not a subject watches the eye target closely. The vision test program makes the computer perform a first correctness / incorrectness decision to decide whether or not a visual line of a subject stays in the eye target for a predetermined time or more, and a second correctness / incorrectness decision to decide by comparing a time when the visual line of the subject is accumulated and stayed on an area of the eye target and other than the eye target. When decided as the correct answer in any of the first correctness / incorrectness decision and the second correctness / incorrectness decision, the vision test program is made to decide that the eye target is visually recognized. A vision test system and a vision test method using it are provided.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a vision testing program, a vision testing system, and a vision testing method. [Background technology]

[0002] For example, a device for detecting a subject's gaze point is known, as disclosed in Patent Document 1 below. The device in Patent Document 1 is equipped with two cameras and an image processing device, and captures an image of the subject's face with the two cameras. Based on the image of the subject's face, the device calculates the coordinates of the subject's corneal reflection point and the center of the pupil, and calculates the direction of the optical axis based on this. According to predetermined conditions, the device corrects the direction of the optical axis to calculate the direction of the subject's visual axis, and detects the gaze point based on the direction of the visual axis.

[0003] Patent Document 2 discloses a visual acuity evaluation device including a gaze point detection unit that detects the position of the gaze point of a subject, a determination unit that determines whether the gaze point is present in a specific area corresponding to a specific index, which is one of multiple visual targets presented on an index presentation unit, based on the detection result of the gaze point detection unit, and an evaluation unit that evaluates the visual acuity of the subject based on the determination result of the determination unit. The evaluation device calculates an existence ratio, which is the proportion of time the gaze point is present in a specific area set around the specific index relative to the display time of the index. If the existence ratio is equal to or greater than a predetermined value, it is determined that the subject is able to recognize the specific index, i.e., an open Landolt ring. It is also possible to use the existence time of the gaze point in the specific area as a criterion instead of the existence ratio. Furthermore, it is described that a subject is presented with an index of the same size multiple times, and if the subject is first determined to be able to identify the index, i.e., the Landolt ring, 50% or more of the times, it is evaluated that the subject has the visual acuity corresponding to the index of that size. If the number of times that a person is judged to be unable to identify the indicator, i.e., the Landolt ring, exceeds 50% of the multiple attempts, the person is evaluated as not having the visual acuity corresponding to the indicator of that size. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-166101 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-169959 Summary of the Invention [Problem to be solved by the invention]

[0005] When conducting visual acuity tests on infants who have difficulty responding verbally, or on patients with symptoms that make it difficult to respond verbally, the examiner presents cards called Teller acuity cards (TACs) in front of the subject, and determines whether the subject is looking at the target by judging the subject's eye movement and facial tilt. This type of visual acuity test is called the preferential gaze method. Visual acuity tests using the preferential gaze method are subject to variability in judgment depending on the examiner, which can raise questions about the reliability of the test results. Another problem is that each test takes a long time.

[0006] There is also known a method of conducting a visual acuity test using a gaze detection device such as those in Patent Document 1 or Patent Document 2, in which only one of a plurality of Landolt rings is opened as a specific index, as shown in Patent Document 2. The inventor has verified that such a test method does not provide sufficient accuracy in measuring visual acuity, because it determines whether the acuity is correct or not only based on the proportion of the index present in the specific region.

[0007] The present invention aims to provide a vision testing program, vision testing system, and vision testing method that eliminates variations in visual acuity assessments by examiners through testing that utilizes hardware resources, shortens testing time compared to vision testing using the preferential gaze method, and improves the accuracy of vision testing. [Means for solving the problem]

[0008] A visual acuity test program that causes a computer to function as a means for displaying a visual target and a means for determining whether a test subject is gazing at the visual target, the visual acuity test program causing a computer to perform a first true / false judgment to determine whether a test subject is gazing at the visual target and a second true / false judgment to determine whether a test subject is gazing at the visual target, and the first true / false judgment is determined to be correct when at least one of the following is satisfied: the test subject's line of sight stays on the visual target continuously for a predetermined time or more (first condition), or the test subject's line of sight stays on the visual target cumulatively for a predetermined time or more (second condition). The first step is to compare the time (T1) during which the gaze accumulates and fixes on the visual target with the time (T2) during which the gaze accumulates and fixes on an area other than the visual target in the image displayed on the image display unit, and determine whether the answer is correct or not. If the answer is determined to be incorrect in both the first and second correct / incorrect judgments, it is determined that the visual target is not seen, and if the answer is determined to be correct in either the first or second correct / incorrect judgment, it is determined that the visual target is seen. This solves the above problem by a vision test program.

[0009] The visual acuity testing system is equipped with a calculation unit and a memory unit that perform calculations and record information to determine whether or not the subject is gazing at the visual target, and the system performs a first true / false judgment to determine whether or not the subject is gazing at the visual target based on information acquired by the gaze evaluation unit, and a second true / false judgment to determine whether or not the subject is gazing at the visual target, and the first true / false judgment is determined to be correct when at least one of the following is satisfied: the subject's gaze continuously fixates on the visual target for a predetermined time or more (first condition), or the subject's gaze cumulatively fixates on the visual target for a predetermined time or more (second condition). The first step is to judge whether the answer is correct or not by comparing the time (T1) during which the gaze accumulates and fixes on the visual target with the time (T2) during which the gaze accumulates and fixes on an area other than the visual target in the image displayed on the image display unit, and then judge whether the answer is correct or not. The above-mentioned problem is solved by a visual acuity testing system that judges whether the visual target is not seen when the answer is judged to be incorrect in both the first and second correctness judgments, and judges whether the visual target is seen when the answer is judged to be correct in either the first or second correctness judgment.

[0010] This is a method for testing visual acuity using a computer equipped with a calculation unit and a storage unit that performs calculations to determine whether or not a subject is gazing at a visual target and records information, and the method performs a first true / false judgment in which the computer determines whether or not the subject is gazing at a visual target based on information acquired by a gaze evaluation unit, and a second true / false judgment in which the computer determines whether or not the subject is gazing at a visual target, and the first true / false judgment is determined to be correct when at least one of the following is satisfied: the subject's gaze continuously fixates on the visual target for a predetermined time or more (first condition), or the subject's gaze cumulatively fixates on the visual target for a predetermined time or more (second condition). The first step is to judge whether the answer is correct or not by comparing the time (T1) during which the gaze accumulates and fixes on the visual target with the time (T2) during which the gaze accumulates and fixes on an area other than the visual target in the image displayed on the image display unit, and then judge whether the answer is correct or not.The above problem is solved by a visual acuity testing method in which the computer is made to judge whether the visual target is not seen if the answer is judged to be incorrect in both the first and second correct / incorrect judgments, and is made to judge whether the answer is correct or not by comparing the time (T1) during which the gaze accumulates and fixes on the visual target with the time (T2) during which the gaze accumulates and fixes on an area other than the visual target in the image displayed on the image display unit.

[0011] In the above-mentioned visual acuity testing program, visual acuity testing system, and visual acuity testing method, the examiner's subjective opinion does not interfere, and therefore objective visual acuity test results can be obtained. Furthermore, if the first and second correct / incorrect judgments are both judged to be incorrect, it is judged that the optotype is not seen, and if either the first or second correct / incorrect judgment is judged to be correct, it is judged that the optotype is seen, thereby improving the accuracy of the test.

[0012] In the above-described vision testing program, vision testing system, and vision testing method, the indicators may be displayed randomly at any position on the image display unit.

[0013] In the above-described visual acuity testing program, visual acuity testing system, and visual acuity testing method, a mark different from the visual target can be displayed on the image display unit before the visual target is displayed, thereby resetting the subject's line of sight to a predetermined position.

[0014] In the above-mentioned vision testing program, vision testing system, and vision testing method, the visual target is, for example, a striped mark, and the visual target for high vision can be one in which the spacing between the stripes is smaller than that of the visual target for low vision.

[0015] In the above-mentioned vision test program, vision test system, and vision test method, if one of the first and second true / false judgments is incorrect, the other of the first and second true / false judgments can be made, and if one of the first and second true / false judgments is correct, the other of the first and second true / false judgments can be prevented from being made. This can speed up the vision test process and reduce the load on the computer. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a vision testing program, vision testing system, and vision testing method that eliminates variation in visual acuity assessment by examiners through testing that utilizes hardware resources, shortens testing time compared to vision testing using the preferential gaze method, and improves the accuracy of vision testing. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a visual acuity testing system. [Figure 2] FIG. 10 is a flowchart showing an example of the processing flow of a visual acuity test program. [Figure 3] FIG. 10 is an explanatory diagram showing an example of a visual target and an example of a mark different from the visual target. [Figure 4] FIG. 10 is an explanatory diagram showing an example of the display position of the target. [Figure 5] FIG. 10 is a flowchart showing an example of the flow of the first true / false determination. [Figure 6] FIG. 10 is a flowchart showing an example of the flow of the second true / false determination. [Figure 7] FIG. 1 is an explanatory diagram showing an example of a visual acuity testing method. [Figure 8] FIG. 10 is an explanatory diagram showing another example of a visual acuity testing method. [Figure 9] FIG. 10 is an explanatory diagram showing another example of the target. [Figure 10] FIG. 10 is an explanatory diagram showing an example of an optotype with a higher level than the optotype in FIG. 9. [Figure 11] FIG. 10 is an explanatory diagram showing another example of the target. [Figure 12] FIG. 10 is an explanatory diagram showing an example in which the display position of the target is changed randomly. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, an embodiment of the vision testing system, vision testing program, and vision testing method of the present invention will be described. The following embodiments and usage examples are merely examples of the present invention, and the technical scope of the present invention is not limited to the exemplified embodiments.

[0019] <Configuration example of a vision testing system> An example of the configuration of a vision testing system is shown in Fig. 1. The vision testing system 1 in Fig. 1 includes an input unit 13, a line-of-sight evaluation unit 14, and an image display unit 15.

[0020] The vision testing system 1 can be constructed, for example, by installing a vision testing program (described later) on a computer. Examples of computers include desktop computers, laptop computers with an integrated screen display, tablet computers, smartphones, and dedicated computers equipped with hardware for evaluating the gaze position (described later).

[0021] The vision testing system 1 shown in Figure 1 is a personal computer on which the vision testing program described below is installed, and is equipped with a calculation unit 11, a memory unit 12, an input / output interface 16, a bus 17 that connects the calculation unit 11, the memory unit 12, and the input / output interface 16 and serves as a path to enable information exchange between each unit, the above-mentioned input unit 13, the above-mentioned gaze evaluation unit 14, and an image display unit 15.

[0022] As shown in Fig. 1, the input unit 13, the gaze evaluation unit 14, and the image display unit 15 are each connected to an input / output interface 16, and are able to exchange information with the calculation unit 11 and the memory unit 12 via a bus 17. In Fig. 1, a bidirectional arrow indicates that information can be exchanged in both directions, and a unidirectional arrow indicates that data can be exchanged in only one direction.

[0023] A CPU, for example, can be used as the calculation unit 11. The storage unit 12 may be any device capable of storing information, and may be, for example, a main storage device such as a RAM that can read and write information at a relatively high speed, and a non-volatile auxiliary storage device such as an HDD or SSD. If a non-volatile device that can read and write information at a high speed is available, the storage unit may be configured as a single storage device.

[0024] The image display unit 15 displays targets, marks, etc. Examples of the image display unit include a display and a projector that projects an image.

[0025] The input unit 13 is a part where information is input to the vision testing system by predetermined operations such as clicking, key input, tapping, and flicking performed by an operator of the vision testing system. The input unit 13 is not particularly limited, but examples thereof include input devices such as a mouse, keyboard, and microphone. The input unit 13 is used, for example, to start processing by a program, and, if necessary, to set the first threshold, second threshold, third threshold, fourth threshold, etc., which will be described later.

[0026] The image display unit 14 and the input unit 13 may be a combined device such as a touch display that has the functions of both.

[0027] The gaze evaluation unit can use a known device capable of detecting the position of the subject's gaze. For example, the gaze evaluation unit includes a first light source, a second light source, a first image capture unit, and a second image capture unit, and can irradiate light rays from the first light source and the second light source toward the subject's cornea, capture the reflected images with the first image capture unit and the second image capture unit, and calculate a space vector with a calculation unit to determine the position of the subject's gaze. For example, an LED that emits infrared light can be used as the first light source or the second light source. For example, a known camera can be used as the first image capture unit or the second image capture unit.

[0028] The vision testing system 1 configured as described above tests the subject's vision, for example, by starting a vision testing program described below that is stored in the memory unit 12, and having the calculation unit 11, memory unit 12, and image display unit 15 execute the processes necessary to test the vision.

[0029] A gaze testing system may be constructed by connecting the above-mentioned image display unit, input unit, or gaze evaluation unit to a general-purpose computer such as a smartphone, tablet computer, or desktop computer via a wired or wireless connection, and installing the vision testing program described below in the memory unit.

[0030] In addition, since dedicated electronic computers incorporating hardware for evaluating the position of the gaze point are commercially available, a gaze testing system may be constructed by installing the below-described visual acuity testing program in the memory of such dedicated electronic computers. An example of such a dedicated electronic computer is a device (GazeFinder (registered trademark)) manufactured by JVC Kenwood Corporation. This device has a configuration similar to that of the device described in Japanese Patent Application Laid-Open No. 2019-166101, and is an integrated device in which a first light source, a second light source, a first imaging unit, a second imaging unit, a display, a memory unit, and a calculation unit are incorporated into a housing. This device is accompanied by a program that causes the device to execute a process for detecting and evaluating the position of the subject's gaze point.

[0031] [Vision test program, vision test method] 2-8, an embodiment of a vision testing program and an embodiment of a method for testing vision therewith will be described.

[0032] Fig. 2 shows the overall flow of the process that the vision test program causes a computer to execute. Fig. 5 shows an example of the first correctness judgment shown in Fig. 2, and Fig. 6 shows an example of the second correctness judgment shown in Fig. 2.

[0033] The visual acuity test program (hereinafter referred to as the program) of this embodiment is intended to cause a computer to function as a means for displaying a visual target and a means for determining whether the subject is gazing at the visual target.

[0034] When the program is started, as shown in Figure 1, the program executes a process to set the current level to level 1, which is the lowest level of difficulty (s1). The set level is saved in the storage unit. Note that the current level may be set to any level via the input unit.

[0035] Next, the program displays a blank image stored in advance in the storage unit on the image display unit (s2). The blank image is a mark different from the "optotype" described below, and is displayed on the image display unit for the purpose of resetting the subject's gaze position before displaying the optotype. In this embodiment, as shown in FIG. 3, an image of a pig that easily attracts the subject's attention is used, and is displayed in a fixed position, the center of the image display unit, before each test begins.

[0036] The blank image, i.e., a mark different from the optotype, is not limited to an image of a pig, but may be any mark different from the optotype. The mark may be, for example, any character, figure, symbol, or combination thereof. The position where the blank image is displayed is not particularly limited, but it is preferably displayed in the center of the image display unit so that it is easily visible to the subject.

[0037] Next, the program searches for an optotype corresponding to the current level among images of a plurality of optotypes stored in advance in the storage unit, and displays one optotype at a random position on the image display unit (s3).

[0038] Examples of optotypes are shown in Figure 3. Figure 3 shows examples of optotypes 21 at levels 1 to 4. Optotypes at levels 5 and above are omitted. The smaller the level value, the lower the difficulty level, making it easier for subjects with relatively poor visual acuity to recognize. The higher the level value, the higher the difficulty level, making it harder for subjects with relatively good visual acuity to recognize. In the optotype 21 shown in Figure 3, the optotype is a circular image with a striped pattern in which first lines of a given color and second lines of a different color are alternately arranged. The difficulty level is expressed by the thickness and spacing of the lines, with the more difficult the optotype, the thinner the lines and the smaller the spacing. For example, a database containing numerical values indicating visual acuity associated with each level of optotype is stored in a memory unit, and the database can be searched based on the viewed optotype to quantify the visual acuity. Note that the configuration of the optotype is not limited to the above example; it may be configured so that the higher the difficulty level, the harder it is for the subject to recognize it.

[0039] In the example of FIG. 4 , the image 23 displayed on the image display unit, i.e., the background color, and one of the first and second lines constituting the striped pattern of the optotype 21 are easily confusable colors. The confusable color combinations are not particularly limited, but examples include white and gray, white and white, and black and black. In the case of color vision deficiency, examples include red and green and yellow and blue. The other of the first and second lines constituting the striped pattern of the optotype 21 is a different color from the first line. The image 23 and the optotype 21 may be images stored in advance in a storage unit. Alternatively, the image 23 stored in a storage unit may be combined with an image of the optotype stored in a storage unit so that the position of the optotype is random.

[0040] To search for the optotype corresponding to the current level, for example, the file name of each optotype is set to include the level number, and the file name is searched for using the current level value.

[0041] Next, the program executes a first correctness determination, which will be described later (s4).

[0042] If the first true / false judgment in (s4) above is determined to be correct, the program determines whether the current level is the final level (s5-1). If the current level is the final level, the program sets the visual acuity value corresponding to the final level as the visual acuity value of the subject (s6-1). If the current level is not the final level, the program sets the next level based on the current level, sets the current level to "current level + 1", stores the changed current level in the memory unit, returns to step (s2) above, and executes the process from (s2) onwards.

[0043] In the above (s5-1), when determining whether the current level is the final level, for example, the value of the final level may be set in advance or the final level may be set in the input unit and stored in the memory unit, and then it may be determined whether the value of the current level matches the value of the final level.

[0044] If the first correct / incorrect judgment in (s4) above is judged to be incorrect, the program displays a blank image again on the image display unit (s5-2). Next, the program displays only one optotype corresponding to the current level, the same as that displayed in (s3) above, at a random position on the image display unit (s6-3). At this time, the optotype is displayed at a position other than that displayed in the previous (s3). This improves the accuracy of the visual acuity test. For example, as shown in FIG. 4, if the optotype 21 is displayed at the top in the first test, the optotype 21 is displayed at the left in the second test, which is a position other than the top position displayed in the previous first test. In the example of FIG. 4, the optotype 21 is displayed at the bottom in the third test, but it may be displayed at the top position, the same as the first test, as long as it is not displayed at the left position, which is the position displayed in the previous second test. However, the display position is random and has no regularity.

[0045] Next, the program causes the subject to judge in the second correctness judgment (described later) whether or not he or she is gazing at the target displayed in s6-3 (s7).

[0046] If the second correctness test determines that the answer is correct, the program then determines whether the current level is the final level (s5-1). The subsequent processing is the same as above, and therefore will not be described here.

[0047] If the second correctness judgment is judged to be an incorrect answer, the program sets the visual acuity value corresponding to the last correct answer level as the visual acuity value of the subject (s8). In this case, if the subject has never given a correct answer, the visual acuity value is set to be lower than the visual acuity value corresponding to Level 1, which is the lowest difficulty level (s8).

[0048] The program displays the visual acuity value of the subject calculated in (s6-1) or (s8) on the image display unit (s9), and ends the measurement. In (s9), when the visual acuity value of the subject is displayed on the image display unit, the visual acuity value of the subject may be printed by an output unit such as a printer, or the visual acuity value of the subject may be printed by an output unit such as a printer without being displayed on the image display unit.

[0049] First True or False Judgment FIG. 5 shows an example of the first true / false judgment.

[0050] The program then shows the subject the visual target displayed on the image display unit in (s3) above, and acquires coordinates indicating the position of the subject's gaze over time (a1). For example, the coordinates can be expressed as the horizontal direction x and the vertical direction y, with the intersection of the x and y axes as the origin, and the distance from the origin along the x-axis and the distance from the origin along the y-axis. The origin is not particularly limited, but can be, for example, a corner of the image 23 (FIG. 4) displayed on the image display unit. Detecting the coordinates indicating the position of the subject's gaze can be achieved by having the gaze evaluation unit detect the position of the subject's gaze over time.

[0051] Next, the program determines a correct answer if either the subject's gaze stays continuously for a predetermined time or more (first condition) or the subject's gaze stays cumulatively on the visual target for a predetermined time or more (second condition) is met, and determines a wrong answer if neither the first condition nor the second condition is met (a2). Note that a correct answer is assumed to be when the subject is correctly gazing at the displayed visual target, and an incorrect answer is assumed to be when the subject is not gazing at the displayed visual target.

[0052] When the step of determining whether the data is true or false in (a-2) above is completed, the first determination of whether the data is true or false is completed.

[0053] Whether or not the subject's gaze is on the visual target can be determined by storing in advance in a storage unit the range of coordinates of the area where the visual target is present in an image including the visual target, and by the calculation unit judging whether or not the coordinates indicating the position of the subject's gaze detected by the gaze evaluation unit are included in the range of coordinates of the area where the visual target is present that has been stored in advance. In other words, if the coordinates indicating the position of the subject's gaze are included in the range, it is determined that the subject's gaze is on the visual target, and if the coordinates indicating the position of the subject's gaze are not included in the range, it is determined that the subject's gaze is not on the visual target.

[0054] The coordinates indicating the position of the subject's gaze are recorded in a memory unit over time. This makes it possible to evaluate how long the subject's gaze remained within the range of coordinates of the area where the visual target previously stored in the memory unit is located. The time interval for recording the coordinates is not particularly limited and can be determined as appropriate. For example, the coordinates may be recorded at intervals of 0.01 to 0.8 seconds.

[0055] When determining whether the subject's gaze has continuously fixed on the visual target for a predetermined period of time or more (first condition), the time the subject's gaze is on the visual target may be measured and the measured value may be compared with a preset threshold to directly determine whether the subject's gaze has continuously fixed on the visual target for a predetermined period of time or more, or the determination may be made indirectly based on the ratio of the time the subject's gaze continuously fixed on the visual target to the time the visual target was presented to the subject. In other words, when the subject's gaze is continuously fixed on the visual target for a predetermined period of time or more under the first condition, this includes cases where it is determined directly or indirectly as described above whether the gaze is on the visual target for a predetermined period of time or more.

[0056] Similarly, when determining whether the subject's gaze has fixed on the visual target for a predetermined cumulative time (second condition), the time the subject's gaze is on the visual target may be measured and the measured value may be compared with a preset threshold to directly determine whether the subject's gaze has fixed on the visual target for a predetermined cumulative time or more, or the determination may be made indirectly based on the ratio of the cumulative time the subject's gaze has fixed on the visual target to the time the visual target was presented to the subject. In other words, when the subject's gaze has fixed on the visual target for a predetermined cumulative time under the second condition, this includes cases where it is determined directly or indirectly as described above whether the gaze has fixed on the visual target for a predetermined cumulative time or more.

[0057] To make a direct judgment, for example, in the process (s3) above, an image containing a visual target is presented to the subject for 5 seconds, and if at least one of the following conditions is met, the answer is judged to be correct; if neither of the following conditions is met, the answer is judged to be incorrect.

[0058] In this example, the program determines that the first condition is met if the subject's gaze fixates on the visual target for two or more consecutive seconds. The program also determines that the second condition is met if the subject's gaze cumulatively fixates on the visual target for three or more seconds. If at least one of the first and second conditions is met, the program determines that the answer is correct. If neither the first nor the second condition is met, the program determines that the answer is incorrect. The reason why the cumulative gaze fixation on the visual target is used as the criterion for a correct answer is that the subject's gaze point may move between the visual target and parts other than the visual target while an image including the visual target is presented to the subject. The cumulative time the gaze remained on the visual target can be calculated by adding up the time the coordinates indicating the subject's gaze remained within the coordinate range of the visual target.

[0059] Indirect judgments can be made, for example, by determining the correct answer when at least one of the following conditions is met in the process (s3): (1) the ratio of the time the subject's gaze continuously fixates on the visual target divided by the time the visual target is presented to the subject is 40% or more (0.4 or more) (first condition); or (2) the ratio of the time the subject's gaze cumulatively fixates on the visual target divided by the time the visual target is presented to the subject is 60% or more (0.6 or more) (second condition). An example of an incorrect answer is determined when neither of these conditions is met. The ratio of 40% or more (0.4 or more) in the first condition is based on the value obtained by dividing the 2-second period during which the subject's gaze continuously fixates on the visual target by the 5-second period during which the visual target is presented. The ratio of 60% or more (0.6 or more) in the second condition is based on the value obtained by dividing the 3-second period during which the subject's gaze cumulatively fixates on the visual target by the 5-second period during which the visual target is presented.

[0060] In addition, to make an indirect judgment, for example, in the above process (s3), if the ratio obtained by dividing the time the visual target is presented to the subject by the time the subject's gaze continuously fixates on the visual target is 250% or less (2.5 or less) (first condition), or if the ratio obtained by dividing the time the visual target is presented to the subject by the cumulative time the subject's gaze fixates on the visual target is 167% or less (1.67 or less) (second condition), the answer is judged to be correct, and if neither is met, the answer is judged to be incorrect. Note that the ratio of 250% or less (2.5 or less), which is the ratio of the first condition above, is an example based on the value obtained by dividing the 5-second presentation time of the visual target by the 2-second continuous gaze time. Furthermore, the ratio of 167% or more (1.67 or less) for the second condition above is an example based on the value obtained by dividing the presentation time of the visual target, which is 5 seconds, by the cumulative time that the gaze is on the visual target, which is 3 seconds.

[0061] The threshold value for determining whether the second condition is met, i.e., the second threshold, is not particularly limited. For example, a correct answer can be obtained when the subject's gaze is continuously fixed on the optotype for a time corresponding to 50-80% of the time the optotype is presented to the subject. For example, if the optotype is presented for 5 seconds as described above, a reference value of 2.5-4 seconds can be used. Furthermore, the threshold value for determining whether the first condition is met, i.e., the first threshold, is not particularly limited. For example, a correct answer can be obtained when the subject's gaze is continuously fixed on the optotype for a time corresponding to 20-55% of the time the optotype is presented to the subject, and a reference value shorter than the second threshold can be used. For example, if the optotype is presented for 5 seconds as described above, a reference value of 1-2.75 seconds can be used. As described above, whether the threshold is met or not can be determined directly or indirectly using a numerical value or ratio indicating time.

[0062] The time for presenting the target, the first threshold, or the second threshold may be input using an input unit and stored in a storage unit, so that the settings can be changed as desired. Alternatively, the time for presenting the target, the first threshold, or the second threshold may be stored in advance in the storage unit.

[0063] In the first correctness judgment in this embodiment, when the subject's gaze is outside the image displayed on the image display unit, the coordinates of the subject's gaze are not measured, resulting in an error. The same applies when the eyes are closed, and the coordinates of the subject's gaze are not measured, resulting in an error. These errors are not taken into account directly, and the time during which the subject's gaze is on the visual target is used as the basis for judgment. Furthermore, in the first correctness judgment, the time during which the subject's gaze is in an area other than the visual target within the image displayed on the image display unit is not taken into account directly.

[0064] Second Correctness Test FIG. 6 shows an example of the second true / false judgment.

[0065] In the above step (s6-3), a visual target according to the current level is displayed at a random position on the image display unit, and then the visual target is maintained at that position for a certain period of time (b-1). The time for which the visual target is presented is not particularly limited, but can be, for example, 5 to 10 seconds.

[0066] Next, the program compares the time (T1) during which the gaze accumulates and fixates on the target with the time (T2) during which the gaze accumulates and fixates on areas other than the target in the image displayed on the image display unit, and determines whether the answer is correct (b2). In the example of Figure 6, if the time (T1) during which the gaze accumulates and fixates on the target is longer than the time (T2) during which the gaze accumulates and fixates on areas other than the target in the image displayed on the image display unit, the program determines the answer is correct, and if the time (T1) during which the gaze accumulates and fixates on the target is shorter than the time (T2) during which the gaze accumulates and fixates on areas other than the target in the image displayed on the image display unit, the program determines the answer is incorrect. As described above, whether the gaze is fixed on the target can be evaluated by whether the coordinates indicating the subject's gaze detected by the gaze evaluation unit are within the range of coordinates of the area where the target is located, which has been stored in advance.

[0067] Note that the time T2 is not measured when the subject's line of sight is in an area other than the image displayed on the image display unit, such as the edge of the image display unit or the room in which the image display unit is installed. In other words, the time T2 does not include the time when the subject's line of sight is in an area other than the image displayed on the image display unit. Similarly, the time T2 does not include the time when the subject has their eyes closed.

[0068] The time (T1) during which the gaze is cumulatively fixed on the visual target is calculated by adding up the time during which the coordinates indicating the subject's gaze are within the coordinate range of the visual target. The time (T2) during which the gaze is cumulatively fixed on an area other than the visual target is calculated by adding up the time during which the coordinates indicating the subject's gaze are cumulatively fixed on the coordinate range of an area other than the visual target within the image displayed on the image display unit. As mentioned above, T2 does not include the time during which the eyes are closed or the time during which the gaze is located on an area other than the image displayed on the image display unit. For example, using the example of Figure 7, T1 is the total time during which the gaze is located within the range of visual target 21, and T2 is the total time during which the gaze is located within the area of image 23 excluding visual target 21.

[0069] To make a judgment of correctness by comparing the time (T1) during which the gaze accumulatively fixates on the optotype with the time (T2) during which the gaze accumulatively fixates on an area other than the optotype in the image displayed on the image display unit, the comparison may be performed directly, for example, by comparing a numerical value representing the time (T1) during which the gaze accumulatively fixates on the optotype with a numerical value representing the time (T2) during which the gaze accumulatively fixates on an area other than the optotype in the image displayed on the image display unit. Alternatively, the comparison may be performed indirectly, for example, by calculating the ratio of the numerical value representing the time (T1) during which the gaze accumulatively fixates on the optotype to the numerical value representing the time (T2) during which the gaze accumulatively fixates on an area other than the optotype in the image displayed on the image display unit. Thus, "comparing the time (T1) during which the gaze accumulatively fixates on the optotype with the time (T2) during which the gaze accumulatively fixates on an area other than the optotype in the image displayed on the image display unit in the second correctness judgment, and making a judgment of correctness" includes the direct or indirect comparison of T1 and T2 as described above.

[0070] To directly compare T1 and T2 in (b2) above, for example, the time (T1) during which the gaze accumulates and remains on the visual target can be compared with the time (T2) during which the gaze accumulates and remains on an area other than the visual target in the image displayed on the image display unit, and if the value of T1 is equal to or greater than the value of T2, the answer can be determined to be correct, and if the value of T1 is less than the value of T2, the answer can be determined to be incorrect; alternatively, if the value of T1 is greater than the value of T2, the answer can be determined to be correct, and if the value of T2 is equal to or less than the value of T1, the answer can be determined to be incorrect.

[0071] In addition, in (b-2) above, to indirectly compare the time (T1) during which the gaze lingers on the target and the time (T2) during which the gaze lingers on a region other than the target in the image displayed on the image display unit to determine whether the answer is correct, for example, the time (T1) during which the gaze lingers on the target and the time (T2) during which the gaze lingers on a region other than the target in the image displayed on the image display unit may be indirectly compared by dividing a numerical value representing the time (T1) during which the gaze lingers on the target by the time (T2) during which the gaze lingers on a region other than the target in the image displayed on the image display unit and determining whether the ratio exceeds a third threshold. A correct answer may be determined if the ratio exceeds the third threshold, and an incorrect answer may be determined if the ratio is equal to or less than the third threshold. The third threshold is not particularly limited, but may be, for example, 90% (0.9) or 100% (1.00). That is, in this example, the correct answer is when T1 / T2>90% (0.9), or when T1 / T2>100% (1.00).

[0072] Furthermore, in the above (b-2), to indirectly compare (T1) with the time (T2) during which the gaze accumulates and stays on an area other than the target in the image displayed on the image display unit to determine whether the answer is correct or not, the value obtained by dividing T2 by T1 may be determined to be correct if it is less than a fourth threshold, and incorrect if it is equal to or greater than the fourth threshold. The fourth threshold is not particularly limited, but may be set to, for example, 110% (1.1) or 100% (1.00). That is, in this example, the answer is correct when T2÷T1<110% (1.1), and correct when T2÷T1<100% (1.00).

[0073] The time for presenting the visual target, the third threshold value, or the fourth threshold value may be input using an input unit and stored in a storage unit so that the settings can be changed as desired. Alternatively, the time for presenting the visual target, the third threshold value, or the fourth threshold value may be stored in advance in the storage unit.

[0074] When the step of determining whether the answer is correct or not according to (b-2) above is completed, the second determination of whether the answer is correct or not is completed.

[0075] In the above program, if the first true / false judgment is incorrect, a second true / false judgment is performed using a different standard from the first true / false judgment.This allows the test to pick up cases where the subject is gazing at the visual target in the first true / false judgment, but is distracted, blinks excessively, or closes their eyes, resulting in an incorrect answer in the first true / false judgment, as a correct answer, thereby improving the accuracy of the test.

[0076] While the subject closes their eyes due to blinking or other reasons, coordinates indicating the subject's gaze are not acquired, and the coordinates indicating the subject's gaze are lost. In the first correct / incorrect judgment, even if the subject gazes at the visual target, the subject may not be judged as correct because their eyes are closed. Furthermore, if the subject's eyes are distracted by an object or person outside the image display unit during the test, the first correct / incorrect judgment may not be judged as correct because the subject is distracted, even though the subject gazes at the visual target. By performing a second correct / incorrect judgment based on a different criterion than the first correct / incorrect judgment, i.e., comparing the time (T1) during which the gaze accumulates and dwells on the visual target with the time (T2) during which the gaze accumulates and dwells on an area other than the visual target within the image displayed on the image display unit, such cases can be identified as correct.

[0077] In the flowchart of Figure 2, the first and second true / false judgments can be interchanged, with the second true / false judgment being performed first, and if the second true / false judgment is incorrect, the first true / false judgment can be performed again, with similarly high test accuracy. Thus, the terms "first" and "second" in the first and second true / false judgments do not indicate the order in which the true / false judgments are performed. If the second true / false judgment is performed first, a case that is determined to be incorrect in the second true / false judgment can be identified as correct in the first true / false judgment, which uses different criteria for true / false judgment than the second true / false judgment.

[0078] By performing the other of the first and second true / false judgments only when either one of them is judged to be an incorrect answer, it is possible to omit the other judgment when one of the judgments is judged to be correct, thereby speeding up the visual acuity test process and reducing the load on the computer.

[0079] [Vision test method] A method for testing visual acuity using the above system with the above program installed will be described with reference to the image displayed on the image display unit shown in Figure 7. Note that Figures 7 and 8 only show the image displayed on the image display unit.

[0080] The example shown in Figure 7 is a case where the subject answered correctly both times in the first true / false judgment. In this example, the program installed in the computer's memory displays a blank image stored in advance in the memory, i.e., an image of a pig, which is a mark 22 different from the visual target, in the center of the image display unit. Next, the program sets the current level to level 1 and stores the current level in the memory, and also displays a visual target 21 corresponding to level 1 from the visual targets stored in the memory in a random position on the image display unit. Based on the coordinates of the subject's gaze obtained by the gaze evaluation unit, the program determines whether the subject's current coordinates are included in the coordinates of the visual target position stored in advance in the memory.

[0081] As shown in Figure 7, in the first correct / incorrect judgment, the computer determines that at least one of the first and second conditions is satisfied based on the coordinates of the subject's gaze position, and if the answer is determined to be correct, the program displays again the image of a pig, which is a blank image (mark 22) stored in advance in the memory unit, in the center of the image display unit. Next, the program sets the current level to the next higher level, i.e., level 2, and stores the newly set current level in the memory unit, and also displays the optotype 21 corresponding to level 2 from the optotypes stored in the memory unit in a random position on the image display unit.

[0082] In the example of FIG. 7, the answer is correct in the second first true / false judgment, and thereafter the third first true / false judgment is performed in the same manner as above.

[0083] Next, an example in which both the first true / false judgment and the second true / false judgment were incorrect will be described with reference to Figure 8. A program installed in the computer's memory displays an image of a pig (mark 22), which is a blank image stored in advance in the memory, in the center of the image display unit. Next, the program sets the current level to level 1 and stores the current level in the memory, and also displays a visual target 21 corresponding to level 1 from the visual targets stored in advance in the memory at a random position on the image display unit. Based on the coordinates of the subject's gaze obtained by the gaze evaluation unit, the program determines whether the subject's current coordinates are included in the coordinates of the visual target position stored in advance in the memory.

[0084] As shown in Figure 8, in the first correct / incorrect judgment, the computer determines that the answer is correct if at least one of the first and second conditions is met based on the coordinates of the subject's gaze position. If the answer is determined to be incorrect, the program displays again the blank image of a pig (mark 22) stored in advance in the memory unit in the center of the image display unit. Next, the program displays the target 21 corresponding to the same level as the current level set earlier, i.e., level 1, in a random position on the image display unit.

[0085] The program uses the coordinates of the subject's gaze position to have the computer make a judgment in the second correct / incorrect judgment by comparing the cumulative time (T1) that the gaze stays on the visual target with the cumulative time (T2) that the gaze stays on something other than the visual target.If the second correct / incorrect judgment is also judged to be incorrect, the program stores in the memory unit the fact that the visual acuity value is below that corresponding to level 1, which is the lowest level of difficulty, and displays this on the image display unit, ending the measurement.

[0086] [Variations] The input unit, the line-of-sight evaluation unit, and the image display unit may be connected to the computer wirelessly via the communication unit, or may be connected to the computer by wire.

[0087] The communication unit is not particularly limited, but examples include an interface card compliant with standards such as IEEE1394, a network interface card for LAN connection, a wireless LAN router compliant with standards such as IEEE802.11a, 802.11b, and 802.11g, and an interface unit compliant with Bluetooth (registered trademark).

[0088] In the example of FIG. 4, there are four display position patterns: top, bottom, left, and right, but the number of display position patterns may be changed as appropriate to increase the number of patterns.

[0089] The visual target is not limited to the above example, and may be an animal such as a rabbit with eyes as shown in Fig. 9. As shown in Fig. 9, the image display unit displays a rabbit with eyes 81 and a rabbit without eyes 82 as visual targets. The rabbit with eyes 81 is set as the visual target, and the rabbit without eyes 82 is not set as the visual target.

[0090] The subject is instructed to look at the rabbit with eyes. The program determines whether the coordinates of the subject's gaze are within the range of coordinates corresponding to the design of the rabbit with eyes 81, which is the visual target. The display positions of the rabbit with eyes 81 and the rabbit without eyes 82 are changed randomly. After that, the first true / false judgment and the second true / false judgment are performed in the same manner as above, thereby testing the subject's visual acuity. In the above example, there is only one rabbit without eyes 82, but there may be multiple rabbits.

[0091] As shown in Figure 10, the difficulty level of the test can be changed by changing the size of the rabbit's eyes. The larger the eye size, the lower the difficulty level, and the smaller the eye size, the higher the difficulty level.

[0092] 11 and 12, for example, the eye of the animal may be set as the target, and the part of the animal other than the eye may be set as the area other than the target. As shown in Fig. 11 and 12, the image display unit displays the rabbit's eye 83 on the rabbit's face while randomly changing the position. The subject is instructed to look at the rabbit's eye 83.

[0093] The program determines whether the coordinates of the subject's line of sight are within the range of the target, rabbit eye 83. After that, the first true / false judgment and the second true / false judgment are performed in the same manner as above, thereby testing the subject's visual acuity.

[0094] The difficulty level, or level, of the test subject's visual acuity can be changed by changing the size of the rabbit's eye 83. The larger the eye size, the lower the difficulty level, and the smaller the eye size, the higher the difficulty level.

[0095] Other than the above, the index may be a point, a point cloud target, a line target, a hiragana target, a katakana target, an alphabet target, a picture target, a Landolt ring, or a Gabor target. [Example]

[0096] [Example 1] The programs shown in Figures 2, 5, and 6 were installed in a device manufactured by JVC Kenwood Corporation (GazeFinder (registered trademark)) to construct a visual acuity testing system according to Example 1. This system was used to test the visual acuity of the subjects. The presentation time of the target in the first correct / incorrect judgment was set to 5 seconds. The criterion for a correct answer under the first condition was that the subject's gaze continuously fixed on the target for 2 seconds or more, with a time of less than 2 seconds being considered an incorrect answer. The criterion for a correct answer under the second condition was that the subject's gaze cumulatively fixed on the target for 3 seconds or more, with a time of less than 3 seconds being considered an incorrect answer. The presentation time of the target in the second correct / incorrect judgment was set to 5 seconds. The cumulative time (T1) during which the subject's gaze was fixed on the target was compared with the cumulative time (T2) during which the subject's gaze was fixed on an area other than the target in the image displayed on the image display unit. An incorrect answer was determined when T1 was equal to or shorter than T2.

[0097] The visual acuity of three subjects was tested using the visual acuity testing system of Example 1. The average visual acuity (logMAR) of the same three subjects was also measured using a near vision chart (Landolt ring) and used as a reference value. The reference value was subtracted from the average visual acuity measured using the visual acuity testing system of Example 1 to determine the difference in accuracy of the visual acuity test. The time required to perform one test using the visual acuity testing system of Example 1 was also investigated. The results are summarized in Table 1 below.

[0098] [Comparative Example 1] The visual acuity of the three subjects was tested using teller acuity cards (TAC). Two examiners were used for the TAC test. A standard value was calculated using the same method as in Example 1, and the standard value was subtracted from the average visual acuity measured in the TAC test in Comparative Example 1 to determine the difference in accuracy of the visual acuity test. The time required to perform one visual acuity test in Comparative Example 1 was also investigated. The results are summarized in Table 1 below.

[0099] Comparative Example 2 A visual acuity testing system for Comparative Example 2 was constructed by installing a program on a device manufactured by JVC Kenwood Corporation (GazeFinder (registered trademark)) that presented an image of three circular targets and one open Landolt ring to the subject for five seconds, and determining that the subject was gazing at the Landolt ring if the open Landolt ring was cumulatively present for 1.5 seconds or more.

[0100] When the program determines that the subject is gazing at the open Landolt ring, i.e., that the answer is correct, it presents the subject with images of the three circles and one Landolt ring with smaller diameters, gradually increasing the difficulty of the test. If the subject answers correctly twice first, the program determines that the subject is viewing the open Landolt ring, and if the subject answers incorrectly twice first, it determines that the subject is not viewing the open Landolt ring. If the subject answers incorrectly, the program uses the visual acuity value of the most recent correct answer as the measurement result. If the subject answers correctly up to the final level, the program uses the visual acuity value of the final level at which the subject answered correctly as the measurement result.

[0101] The subjects were the three people mentioned above. A standard value was calculated using the same method as in Example 1, and the standard value was subtracted from the average visual acuity measured in the test using the visual acuity testing system of Comparative Example 2 to determine the difference in accuracy of the visual acuity test. The time required to perform one visual acuity test of Comparative Example 2 was also investigated. The results are summarized in Table 1 below.

[0102] [Table 1]

[0103] As is clear from the results in Table 1, the visual acuity testing method using the visual acuity testing system of Example 1 can shorten the time required for one test compared to Comparative Example 1 or Comparative Example 2. It can also be seen that the visual acuity testing method using the visual acuity testing system of Example 1 has higher accuracy in the visual acuity test compared to Comparative Example 2. [Explanation of symbols]

[0104] 11 Arithmetic section 12 Storage section 21 Visual targets 22 marks s4 First True or False Judgment s7 Second True or False Judgment

Claims

1. Computer, means for displaying an optotype; A visual acuity test program that functions as a means of determining whether a subject is gazing at a visual target, The visual acuity test program causes the subject to perform a first true / false judgment to determine whether or not the subject is gazing at a visual target, and a second true / false judgment to determine whether or not the subject is gazing at a visual target, The first correct / incorrect judgment is a step in which, if at least one of the following conditions is satisfied, the answer is judged to be correct: when the subject's gaze continuously fixates on the visual target for a predetermined time or more (first condition), or when the subject's gaze cumulatively fixates on the visual target for a predetermined time or more (second condition), and if neither of these conditions is satisfied, the answer is judged to be incorrect; The second correctness judgment is a step of comparing a time (T1) during which the gaze accumulates and stays on the target with a time (T2) during which the gaze accumulates and stays on an area other than the target in the image displayed on the image display unit, and making a correctness judgment; If the answer is determined to be incorrect in both the first true / false judgment and the second true / false judgment, it is determined that the visual target is not visually recognized. This vision testing program determines that the visual target is being viewed when either the first or second correct / incorrect judgment is determined to be correct.

2. 2. The visual acuity test program according to claim 1, wherein the optotype is displayed randomly at any position on the image display unit.

3. 3. The visual acuity test program according to claim 1, wherein a mark different from the optotype is displayed on the image display unit before the optotype is displayed.

4. 4. The visual acuity test program according to claim 1, wherein the visual targets are striped marks, and the high-visual-sight visual targets have smaller stripe spacing than the low-visual-sight visual targets.

5. The vision testing program When one of the first true / false judgment and the second true / false judgment is an incorrect answer, the other of the first true / false judgment and the second true / false judgment is made; 5. The computer program for visual acuity testing according to claim 1, wherein when one of the first and second true / false judgments is correct, the other of the first and second true / false judgments is not performed.

6. A visual acuity testing system including a calculation unit and a storage unit that perform calculations to determine whether a subject is gazing at a visual target and record information, The system performs a first true / false judgment to determine whether the subject is gazing at the visual target and a second true / false judgment to determine whether the subject is gazing at the visual target, based on the information acquired by the gaze evaluation unit; The first correct / incorrect judgment is a step of judging the answer as correct if at least one of the following conditions is satisfied: the subject's gaze stays on the visual target continuously for a predetermined time or more (first condition), or the subject's gaze stays on the visual target cumulatively for a predetermined time or more (second condition), and judging the answer as incorrect if neither of the following conditions is satisfied; The second correctness judgment is a step of comparing a time (T1) during which the gaze accumulates and stays on the target with a time (T2) during which the gaze accumulates and stays on an area other than the target in the image displayed on the image display unit, and making a correctness judgment; If the answer is determined to be incorrect in both the first true / false judgment and the second true / false judgment, it is determined that the visual target is not visually recognized. A vision testing system that determines that the visual target is being viewed when either the first or second correct / incorrect judgment is judged to be correct.

7. A method for testing visual acuity using a computer having a calculation unit and a memory unit that performs calculations to determine whether a subject is gazing at a visual target and records information, The method includes performing a first true / false determination in which a computer determines whether or not the subject is gazing at a visual target, based on information acquired by the gaze evaluation unit, and a second true / false determination in which the computer determines whether or not the subject is gazing at a visual target; The first correctness judgment is a step in which the computer judges the answer as correct if at least one of the following conditions is satisfied: the subject's gaze stays on the visual target continuously for a predetermined time or more (first condition), or the subject's gaze stays on the visual target cumulatively for a predetermined time or more (second condition), and judges the answer as incorrect if neither of the following conditions is satisfied; The second correctness judgment is a step of comparing a time (T1) during which the gaze accumulates and stays on the target with a time (T2) during which the gaze accumulates and stays on an area other than the target in the image displayed on the image display unit, and making a correctness judgment; If the answer is determined to be incorrect in both the first correct / incorrect judgment and the second correct / incorrect judgment, the computer is made to determine that the visual target is not visually recognized, A visual acuity testing method in which a computer determines that a visual target is being viewed when either the first or second correct / incorrect judgment is determined to be correct.

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