Examination device and examination method

Abstract

This examination device (100) comprises: a projection unit (20) that projects an examination image onto a subject's retina by directly irradiating the subject's retina with light rays emitted by a light source; an acquisition unit (12) that acquires a response of the subject with respect to the examination image; and a determination unit (13) that makes a determination regarding dry eye on the basis of the subject's response. An examination method comprises: a step for projecting an examination image onto a subject's retina by directly irradiating the subject's retina with light rays emitted by a light source; a step for acquiring a response of the subject with respect to the examination image; and a step for making a determination regarding dry eye on the basis of the subject's response.

Description

Inspection device and inspection method

[0001] The present invention relates to an inspection device and an inspection method.

[0002] With the widespread use of personal computers, smartphones, and the like, an increasing number of people are becoming aware of eye disorders. One such eye disorder is dry eye, which is caused by tear film instability. Known methods for testing dry eye include the tear film breakup time test, the fluorescein staining test, and the Schirmer test. Furthermore, a method for accurately testing dry eye, even when fixational eye movements are present, is known (see, for example, Patent Document 1).

[0003] JP 2009-178174 A

[0004] Although the above-mentioned method is known as a method for testing dry eye, it is desired to test dry eye using a simpler method.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a simple test for dry eye.

[0006] The present invention is an examination device that includes a projection unit that directly irradiates the light beam emitted from a light source onto the subject's retina to project a test image onto the retina, an acquisition unit that acquires the subject's response to the test image, and a judgment unit that judges whether or not there is dry eye based on the response.

[0007] In the above configuration, the determining unit may be configured to determine whether or not there is a dry eye based on a response time from when the projection of the test image starts until the response.

[0008] The above configuration may further include a storage unit that stores information indicating a correspondence relationship between time and dry eye, and the determination unit may determine whether or not there is a dry eye based on the response time and the information.

[0009] In the above configuration, the acquisition unit can be configured to acquire the response from the subject when the subject continues to look at the visual target in the test image without blinking and feels that the appearance of the visual target has changed.

[0010] In the above configuration, the projection unit may be configured to project the test image with the number of seconds from the start of projection of the test image displayed as the visual target.

[0011] In the above configuration, the projection unit can be configured to project the test image in which a Landolt ring corresponding to the subject's visual acuity is displayed as the visual target, and the acquisition unit can be configured to acquire the response from the subject when the subject feels that it is becoming difficult to distinguish the orientation of the Landolt ring.

[0012] In the above configuration, the projection unit projects the test image in which a Landolt ring whose orientation changes every predetermined time is displayed as an optotype, the acquisition unit acquires the response in which the subject continues to look at the Landolt ring without blinking and answers the orientation of the Landolt ring, and the judgment unit can be configured to judge whether or not there is dry eye based on the time from the start of projection of the test image to the time when the Landolt ring is displayed when the answer has been incorrect a predetermined number of times.

[0013] In the above configuration, the projection unit projects the test image in which a visual target is repeatedly illuminated, the acquisition unit acquires the response of the subject for each of the repeatedly illuminated visual targets, and the judgment unit calculates a response time difference, which is the difference between the response time from when the visual target is illuminated until the acquisition unit acquires the response during the nth (n is an integer of 2 or more) illumination of the visual target and the response time from when the visual target is illuminated until the acquisition unit acquires the response during the (n-1)th) illumination of the visual target, calculates an average value and a standard deviation of the response time differences during the repeated illumination of the visual target, and makes a judgment about dry eye based on the average value of the response time differences and the standard deviation of the response time differences.

[0014] In the above configuration, the determination unit may be configured to calculate the square root of the sum of the square of the average value of the response time differences and the square of the standard deviation of the response time differences, and determine whether or not there is a dry eye based on the value of the square root.

[0015] In the above configuration, if the acquisition unit is unable to acquire the response between the lighting of the visual target and the lighting of the next visual target, the determination unit may be configured to specify as the response time a time that is longer than the sum of the lighting time of the visual target and the extinguishing time until the lighting of the next visual target.

[0016] The present invention provides an examination method comprising the steps of: irradiating a light beam emitted from a light source directly onto a subject's retina to project a test image onto the retina; acquiring the subject's response to the test image; and assessing dry eye based on the response.

[0017] According to the present invention, dry eye can be easily examined.

[0018] FIG. 1 is a diagram showing the configuration of an inspection device according to Example 1. FIG. 2 is a diagram showing a projection unit in Example 1. FIG. 3(a) is a diagram showing light rays irradiated onto a retina in retinal projection, and FIG. 3(b) is a diagram showing light rays irradiated onto a retina in natural vision. FIG. 4(a) is a diagram showing an experimental setup assuming natural vision, and FIG. 4(b) is a diagram showing an experimental setup assuming retinal projection. FIG. 5(a) is a diagram showing an image captured by a camera in the experimental setup assuming natural vision, and FIG. 5(b) is a diagram showing an image captured by a camera in the experimental setup assuming retinal projection. FIGS. 6(a) and 6(b) are diagrams showing the experimental setups in FIGS. 4(a) and 4(b) in which a thread or a wrinkled transparent vinyl sheet is placed in front of the pseudo-eye optical system. FIGS. 7(a) and 7(b) are diagrams showing images captured by a camera in the experimental setup assuming natural vision when a thread or a wrinkled transparent vinyl sheet is placed in front of the pseudo-eye optical system. 8(a) and 8(b) are diagrams showing images captured by a camera when a thread or a wrinkled transparent vinyl sheet is placed in front of a pseudo-ocular optical system in an experimental device simulating retinal projection. FIG. 9 is a flowchart showing an example of a dry eye examination method in Example 1. FIGS. 10(a) to 10(c) are diagrams showing example examination images. FIG. 11 is a flowchart showing an example of a dry eye examination method in Example 2. FIG. 12(a) is a time chart showing control of the illumination of the optotype by the projection control unit, and FIG. 12(b) is a time chart showing illumination of the optotype and responses. FIG. 13(a) is a diagram showing experimental results of the average value of response time differences versus the NG rate, and FIG. 13(b) is a diagram showing experimental results of the standard deviation of response time differences versus the NG rate. FIG. 14(a) is a diagram showing experimental results of the standard deviation of response time differences versus the average value of response time differences, and FIG. 14(b) is a diagram showing experimental results of the frequency of response time differences versus vectors.

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0020] 1 is a diagram illustrating a configuration of an inspection device 100 according to Example 1. As illustrated in FIG. 1 , the inspection device 100 includes a control unit 10, a projection unit 20, a display unit 30, a storage unit 40, and an input unit 50.

[0021] The control unit 10 controls each component of the testing device 100. The control unit 10 includes a processor such as a central processing unit (CPU), a random access memory (RAM), and a read-only memory (ROM). The control unit 10 realizes the following functions by having the CPU read and execute programs stored in the storage unit 40 or the ROM. The control unit 10 includes a projection control unit 11, an acquisition unit 12, and a determination unit 13. The projection control unit 11 controls the projection unit 20 based on image data stored in the storage unit 40 to project a test image onto the subject's retina. The acquisition unit 12 acquires the subject's response to the test image input by the subject using the input unit 50. The determination unit 13 determines whether the subject has dry eye based on the subject's response acquired by the acquisition unit 12. The determination unit 13 displays the test results for dry eye on the display unit 30. The control unit 10 may also include a communication device that transmits and receives data via a communication line such as a LAN, the Internet, or a dedicated line.

[0022] The projection unit 20 projects a test image onto the subject's retina based on instructions from the projection control unit 11. The projection unit 20 is a retinal projection type projector that uses Maxwell's vision, and projects the test image directly onto the subject's retina by directly irradiating the retina with light rays (laser light) that form the test image. Details of the projection unit 20 will be described later.

[0023] The display unit 30 is a display device such as a liquid crystal display, etc. The display unit 30 displays the test results for dry eye based on instructions from the determination unit 13.

[0024] The storage unit 40 is a non-volatile storage device such as a flash memory, and stores data for the determination unit 13 to determine whether or not there is dry eye, image data of the test image projected by the projection control unit 11, and the like.

[0025] The input unit 50 is an input device such as a keyboard, a mouse, a touchpad, a button, a switch, and an audio microphone. The input unit 50 is used by an examiner to input instructions to the inspection device 100. The input unit 50 is also used by an examinee to respond to an inspection image.

[0026] FIG. 2 is a diagram illustrating the projection unit 20 in the first embodiment. As shown in FIG. 2, the projection unit 20 includes a light source 21, a lens 22, a scanning unit 23, a reflecting mirror 24, a projection mirror 25, and a lens 26. The light source 21 emits a light beam 70 (laser light) based on instructions from the projection control unit 11. The light source 21 emits the light beam 70, which is visible light, for example, red laser light (wavelength: approximately 610 nm to 660 nm), green laser light (wavelength: approximately 515 nm to 540 nm), and blue laser light (wavelength: approximately 440 nm to 480 nm). An example of the light source 21 that emits red, green, and blue laser light is a light source that integrates RGB (red, green, and blue) laser diode chips and a three-color combining device. Note that the light source 21 may also emit a light beam 70 of a single wavelength.

[0027] The light beam 70 emitted by the light source 21 passes through the lens 22. The lens 22 is a condenser lens that converts the light beam 70 from diffused light to focused light. The lens 22 is provided between the light source 21 and the scanning unit 23 to convert the light beam 70 reflected by the reflecting mirror 24 into substantially parallel light. The light beam 70 that passes through the lens 22 enters the scanning unit 23. The scanning unit 23 (scanner) scans the light beam 70 in two dimensions, the horizontal and vertical directions. For example, the scanning unit 23 scans the light beam 70 at high speed (e.g., raster scan) from the upper left to the lower right of the image based on instructions from the projection control unit 11. The scanning unit 23 is, for example, a microelectromechanical system (MEMS) mirror. Note that the scanning unit 23 may be a mirror other than a MEMS mirror, such as potassium tantalate niobate (KTN).

[0028] The plurality of light beams 70 scanned in two dimensions by the scanning unit 23 and emitted in different directions from the scanning unit 23 at different times are incident on the reflecting mirror 24. The reflecting mirror 24 is a concave mirror having a reflective surface formed of a curved surface such as a free-form surface, and has positive focusing power. The plurality of light beams 70 reflected by the reflecting mirror 24 converge at a convergence point 74 in front of the projection mirror 25. A lens 26 is provided at the convergence point 74. The lens 26 is a condenser lens that converts each of the plurality of light beams 70 from approximately parallel light into focused light. The lens 26 is provided at the convergence point 74 to convert each of the plurality of light beams 70 reflected by the projection mirror 25 into approximately parallel light.

[0029] The multiple light rays 70 pass through the lens 26 and are incident on the projection mirror 25. The projection mirror 25 is disposed in front of the subject's eye 60. The projection mirror 25 reflects the multiple light rays 70 toward the subject's eye 60. The projection mirror 25 is a concave mirror having a reflective surface formed of a curved surface such as a free-form surface, and has positive focusing power. The multiple light rays 70 reflected by the projection mirror 25 pass through the subject's pupil 62 and converge at a convergence point 72 on or near the crystalline lens 63, before being projected onto the retina 61. This allows the subject to view the test image formed by the light rays 70.

[0030] [Differences Between Retinal Projection and Natural Vision] The differences in light rays irradiated onto the retina between retinal projection and natural vision will be described. FIG. 3( a) is a diagram showing light rays 70 irradiated onto the retina 61 in retinal projection, and FIG. 3( b) is a diagram showing light rays 70a irradiated onto the retina 61 in natural vision. As shown in FIG. 3( a), in retinal projection, multiple light rays 70 scanned by the scanning unit 23 converge at a convergence point 72 on or near the crystalline lens 63, and then diverge and irradiate the retina 61. Because the light rays 70 cannot irradiate the retina 61 unless they pass through the pupil 62, the diameter of the light rays 70 is set to be sufficiently smaller than the diameter of the pupil 62. For example, since the diameter of the pupil 62 is typically about 4 mm, the diameter of the light rays 70 is set to about 1 mm. Because the diameter of the light rays 70 is thus small, if a small foreign object 75 is present on the surface of the cornea 64, the light rays 70 may be largely blocked by the foreign object 75. In this case, the user will perceive variations in shading and the like in the image projected onto the retina 61. Furthermore, because retinal projection has a deep focal depth, a focus-free image is projected across the entire image area. This is also a factor that makes it easier for the user to perceive variations in shading and the like in the projected image.

[0031] 3B , in natural vision, the diameter of light rays 70 a incident on the pupil 62 from various directions is determined by and equal to the diameter of the pupil 62. Therefore, the diameter of the light rays 70 a is, for example, approximately 4 mm. For this reason, if a small foreign object 75 is present on the surface of the cornea 64, only a portion of each of the multiple light rays 70 a will be blocked by the foreign object 75, and most of the light rays will be irradiated onto the retina 61. For this reason, it is difficult for the user to perceive differences such as shading in the image projected onto the retina 61.

[0032] As described above, with natural vision, even if there is an abnormality on the surface of the cornea, the image projected onto the retina 61 is unlikely to change, making it difficult to grasp the surface condition of the cornea from this image. On the other hand, with retinal projection, if there is an abnormality on the surface of the cornea, the image projected onto the retina 61 changes, making it possible to grasp the surface condition of the cornea from this image. Because dry eye is caused by an instability of the tear film on the surface of the cornea, it is possible to test for dry eye by using retinal projection, which makes it easy to grasp the surface condition of the cornea.

[0033] [Experiment 1] An experiment was conducted to examine how the image projected onto the retina differs between retinal projection and natural vision. FIG. 4(a) shows an experimental setup that simulates natural vision. As shown in FIG. 4(a), a screen 92 was photographed using a camera 90 equipped with a pseudo-eye optical system 91. The pseudo-eye optical system 91 is the same as the pseudo-eye optical system described in Japanese Patent Application Laid-Open No. 2022-000153, and therefore a description thereof will be omitted. A plurality of characters were arranged in a grid pattern on the screen 92. Since natural vision was simulated, the pseudo-eye optical system 91 and the screen 92 were spaced a sufficient distance apart.

[0034] Fig. 4(b) shows an experimental setup assuming retinal projection. As shown in Fig. 4(b), a retinal projection device 93 was placed in front of a camera 90 equipped with a pseudo-eye optical system 91, and the image projected by the retinal projection device 93 was captured by the camera 90 via the pseudo-eye optical system 91. The configuration of the retinal projection device 93 is the same as that of the projection unit 20 shown in Fig. 2, so a description thereof will be omitted.

[0035] 5(a) shows an image captured by a camera 90 in an experimental device simulating natural vision, and FIG. 5(b) shows an image captured by a camera 90 in an experimental device simulating retinal projection. As shown in FIG. 5(a), the peripheral areas of the image are out of focus in natural vision, whereas as shown in FIG. 5(b), the entire image is in focus in retinal projection. This is because, as described above, retinal projection has a deep depth of focus. Thus, because the entire image is in focus in retinal projection, as described above, if shading or other irregularities occur in the projected image due to an abnormality in the corneal surface, the user can easily detect the irregularities.

[0036] Next, in the experimental setup shown in Figures 4(a) and 4(b), a thread or a wrinkled transparent vinyl sheet was placed in front of the pseudo-eye optical system 91, and an image projected by the screen 92 or retinal projection device 93 was photographed. Figures 6(a) and 6(b) are diagrams showing the experimental setup shown in Figures 4(a) and 4(b), in which a thread 95 or a wrinkled transparent vinyl sheet 96 was placed in front of the pseudo-eye optical system 91. The thread 95 and the transparent vinyl sheet 96 were placed 2.5 mm away from the lens of the pseudo-eye optical system 91, a position optically equivalent to the corneal surface.

[0037] 7(a) and 7(b) are diagrams showing images captured by a camera 90 when a thread 95 or a wrinkled transparent vinyl sheet 96 was placed in front of a pseudo-eye optical system 91 in an experimental device designed to simulate natural vision. As shown in FIG. 7(a), in the case of natural vision, even when a thread 95 was placed in front of the pseudo-eye optical system 91, an image was captured in which the influence of the thread 95 did not appear. As shown in FIG. 7(b), in the case of natural vision, when a wrinkled transparent vinyl sheet 96 was placed in front of the pseudo-eye optical system 91, the entire image became dark due to a decrease in transmittance caused by the transparent vinyl sheet 96, but the influence of the wrinkles in the transparent vinyl sheet 96 was not captured.

[0038] In this way, in the case of natural vision, the image of the screen 92 was captured without being affected by the wrinkles in the thread 95 and transparent vinyl sheet 96 placed in front of the pseudo-eye optical system 91, which is thought to be due to the reason explained in Figure 3 (b).

[0039] 8(a) and 8(b) are diagrams showing images captured by a camera 90 when a thread 95 or a wrinkled transparent vinyl sheet 96 is placed in front of a pseudo-eye optical system 91 in an experimental device designed for retinal projection. As shown in FIG. 8(a), in the case of retinal projection, a shadow caused by the influence of the thread 95 placed in front of the pseudo-eye optical system 91 is captured. As shown in FIG. 8(b), in the case of retinal projection, a shadow caused by the influence of the wrinkles in the transparent vinyl sheet 96 placed in front of the pseudo-eye optical system 91 is captured.

[0040] In this way, in the case of retinal projection, the image captured was affected by the wrinkles in the thread 95 and transparent vinyl sheet 96 placed in front of the pseudo-eye optical system 91, which is thought to be due to the reasons explained in Figure 3(a).

[0041] Therefore, from the above experimental results, it can be seen that in the case of retinal projection, if there is an abnormality on the surface of the cornea, a change occurs in the image projected onto the retina 61. In other words, since the optically unstable state of the corneal surface is reflected in the image projected onto the retina 61, it can be seen that the state of the corneal surface can be understood from the appearance of the projected image. Therefore, it can be seen that by using retinal projection, it is possible to test for dry eye caused by an instability of the tear film on the corneal surface.

[0042] 9 is a flowchart showing an example of a dry eye testing method in Example 1. In testing for dry eye, first, the subject is instructed to place his / her face at the measurement position of the testing device 100. Then, the subject is instructed to continue gazing at the test image without blinking during the test, and to operate the input unit 50 (for example, press a switch) when he / she senses that a change has occurred in the optotype (letters, numbers, or designs) displayed on the test image (for example, that the optotype has become difficult to distinguish).

[0043] As shown in FIG. 9 , the projection control unit 11 controls the projection unit 20 in response to a signal to start the test given by the examiner operating the input unit 50 to project a test image 80 onto the subject's retina 61 (step S10). FIGS. 10( a) to 10(c) are diagrams showing examples of the test image 80. As shown in FIG. 10(a), the test image 80 may be an image in which a number 82 is displayed as a visual target against a background 81. In this case, a constant number 82 (e.g., "5") may be continuously displayed, or the number 82 may represent the time since the start of projection of the test image 80. That is, the number 82 becomes "2" when two seconds have elapsed since the start of projection of the test image 80, and becomes "4" when four seconds have elapsed. Furthermore, as shown in FIGS. 10(b) and 10(c), the test image 80 may be an image in which a letter 83 is displayed as a visual target against a background 81, or an image in which a design 84, such as a Landolt ring, is displayed as a visual target against the background 81. When the design 84 is a Landolt ring, it is desirable to display the Landolt ring in a size that corresponds to the visual acuity of the subject. The background 81 may be gray, and the optotypes such as the numbers 82, letters 83, and design 84 may be white.

[0044] 9 , the subject continues to gaze at the test image 80 projected onto the retina 61 without blinking, and when the subject feels that the appearance of the optotype displayed in the test image 80 has changed, the subject makes an input using the input unit 50 (step S12). For example, if numbers 82 or letters 83 are displayed in the test image 80, the subject makes an input using the input unit 50 when the subject feels that the numbers 82 or letters 83 have become difficult to distinguish or can no longer be distinguished. If a Landolt ring is displayed as the design 84, the subject makes an input using the input unit 50 when the subject feels that the orientation of the Landolt ring has become difficult to distinguish or can no longer be distinguished.

[0045] Next, the acquisition unit 12 acquires a response to the test image 80 input by the subject using the input unit 50 (step S14).

[0046] Next, the determination unit 13 calculates the response time from the start of projection of the test image 80 in step S10 to the acquisition of the subject's response in step S14, and determines whether the subject has dry eye based on the calculated response time and the data stored in the memory unit 40 (step S16). Because the subject continues to stare at the test image 80 without blinking, the change in the appearance of the target in the test image 80 is likely due to the breakdown of the tear film on the corneal surface. Therefore, the degree of dry eye can be determined from the response time until the change in the appearance of the target in the test image 80. For example, data such as that shown in Table 1 is stored in the memory unit 40. Table 1 associates time with dry eye symptoms. If the calculated response time is less than a seconds, the tear film on the corneal surface is rapidly broken down, and the determination unit 13 determines that the subject has severe dry eye. If the response time is between a and b seconds, the condition is determined to be moderate dry eye, and if the response time is between b and c seconds, the condition is determined to be mild dry eye. If the response time is longer than c seconds, the condition is determined to be non-dry eye.

[0047] The method for determining the symptoms of dry eye from the response time is not limited to the method using Table 1, but may be a method using, for example, a mathematical formula.

[0048] Next, the determination unit 13 displays the test results of dry eye determined in step S16 on the display unit 30 (step S18). The examiner and the subject can know from the test results displayed on the display unit 30 whether the subject has dry eye and the extent of the dry eye symptoms.

[0049] [Modification] The flowchart of the dry eye examination method in the modification of Example 1 is the same as that in Fig. 9, and will be described using Fig. 9. As shown in Fig. 9, the projection control unit 11 controls the projection unit 20 to project an examination image 80 onto the subject's retina 61 (step S10). In the modification of Example 1, the examination image 80 displays a Landolt ring pattern 84 as shown in Fig. 10(c), and the orientation of the Landolt ring changes at predetermined intervals (for example, every second).

[0050] The subject answers by inputting the orientation of the Landolt ring, which changes every predetermined time, using the input unit 50 (step S12).

[0051] The acquisition unit 12 acquires a response regarding the orientation of the Landolt ring input by the subject using the input unit 50 (step S14).

[0052] The determination unit 13 determines whether the answer regarding the orientation of the Landolt ring obtained in step S14 is correct or incorrect. Then, the determination unit 13 calculates the time from the start of projection of the test image 80 to the time when the Landolt ring is projected when a predetermined number of consecutive incorrect answers (e.g., three consecutive incorrect answers) occur, and determines whether or not the patient has dry eye based on this time and the data stored in the memory unit 40 (e.g., data such as those in Table 1). Next, the determination unit 13 causes the display unit 30 to display the test results for dry eye determined in step S16 (step S18).

[0053] According to the first embodiment and its modifications, as shown in FIG. 9 , the projection unit 20 directly irradiates the light beam 70 emitted by the light source 21 onto the subject's retina 61 to project the test image 80 onto the retina 61 (step S10). The acquisition unit 12 acquires the subject's response to the test image 80 (step S14). The determination unit 13 determines whether or not there is dry eye based on the response acquired in step S14 (step S16). In this way, by utilizing retinal projection to determine whether or not there is dry eye, dry eye can be easily tested. Furthermore, because the determination of whether or not there is dry eye is based on the subject's response, the test is based on the subject's awareness, making it easier for the subject to accept the dry eye test results.

[0054] 9, the determination unit 13 determines whether or not the subject has dry eye based on the response time from the start of projection of the test image 80 to the subject's response to the test image 80 (step S16). This allows for a simple test for dry eye.

[0055] Furthermore, in Example 1, the storage unit 40 stores information indicating the correspondence relationship between time and dry eye, as shown in Table 1. The determination unit 13 determines whether or not there is dry eye based on the response time from when the projection of the test image 80 begins until the subject's response to the test image 80 and the information stored in the storage unit 40. This allows for a simple test for dry eye.

[0056] 9 , the acquisition unit 12 acquires the subject's response when the subject continues to look at the optotype (number 82, letter 83, or design 84) in the test image 80 without blinking and feels that the appearance of the optotype has changed. This allows for dry eye testing based on the time it takes for the tear film to break down and expose the cornea (tear film breakup time).

[0057] 10A, the projection unit 20 projects the test image 80 displaying the number of seconds since the start of projection of the test image 80. This allows the subject to know their own tear film breakup time, making it easier for them to accept the dry eye test results.

[0058] In Example 1, as shown in Fig. 10(c), the projection unit 20 projects a test image 80 displaying a Landolt ring according to the subject's visual acuity. The acquisition unit 12 acquires a response from the subject when the subject feels that it has become difficult to distinguish the orientation of the Landolt ring. This clarifies the criteria for determining whether the appearance of the optotype has changed, making it easier for the subject to respond.

[0059] In a modification of Example 1, the projection unit 20 projects a test image 80 in which the orientation of the Landolt ring is changed every predetermined time. The acquisition unit 12 acquires a response from the subject in which the subject continues to look at the Landolt ring without blinking and answers the orientation of the Landolt ring. The determination unit 13 determines whether or not the subject has dry eye based on the time from the start of projection of the test image 80 to the time when the Landolt ring is displayed when the subject's answer has been incorrect a predetermined number of times. This causes the subject to consciously look at the Landolt ring, the orientation of which changes every predetermined time, thereby improving the accuracy of the dry eye test.

[0060] In Example 2, another example of a dry eye examination method will be described. In a dry eye examination, the subject is instructed not to blink during the examination, but depending on the severity of the dry eye, the subject may blink unconsciously or consciously during the examination because they cannot resist it. Therefore, in Example 2, a dry eye examination method that focuses on blinking during the examination will be described. Note that the configuration of the examination device according to Example 2 is the same as that of Example 1, and therefore illustrations and descriptions thereof will be omitted.

[0061] 11 is a flowchart showing an example of a dry eye examination method in Example 2. In the dry eye examination, first, the subject is instructed not to blink during the examination and, because the optotype will repeatedly light up, to operate the input unit 50 when he or she recognizes that the optotype has lighted up.

[0062] As shown in FIG. 11 , the projection control unit 11 controls the projection unit 20 to start projecting a test image onto the subject's retina 61 (step S20). Next, the projection control unit 11 controls the projection of the test image to light up a visual target at a predetermined position on the retina 61, and then turns off the visual target after a predetermined time has elapsed (step S22). The predetermined position is preferably near the fovea centralis, where the subject's reaction time is fast and visual field defects are unlikely to occur. The visual target may be a bright spot, or may be a number 82, a letter 83, or a design 84 as shown in FIGS. 10( a) to 10(c). The dynamic range of brightness between the background of the test image and the visual target may be, for example, 20 dB to 30 dB.

[0063] FIG. 12(a) is a time chart showing the control of the illumination of the optotype by the projection control unit 11. In FIG. 12(a), the horizontal axis represents elapsed time, and the vertical axis represents ON / OFF of the illumination of the optotype. As shown in FIG. 12(a), the projection control unit 11 illuminates the optotype (ON) for a predetermined time T1, and then turns it off (OFF). After a predetermined time T2 has elapsed since the illumination of the optotype was turned off, the projection control unit 11 turns the optotype back on (ON). The projection control unit 11 repeatedly turns the optotype on and off in this manner. The predetermined time T1 is, for example, a fixed time between 0.1 and 0.3 seconds, e.g., 0.2 seconds. The predetermined time T2 may be a fixed time (e.g., 1.0 seconds), but is preferably a time determined by a random number to prevent the subject from operating the input unit 50 at regular intervals based on intuition even when they cannot see the optotype. For example, the predetermined time T2 is determined by a random number between 0.7 and 1.0 seconds.

[0064] 11 , the subject operates the input unit 50 when recognizing the optotype, and the acquisition unit 12 therefore determines whether or not a response input by the subject using the input unit 50 has been acquired (step S24). If the acquisition unit 12 has not acquired a response (if No), the acquisition unit 12 proceeds to step S26 and determines whether or not it is time to turn on the next optotype. The acquisition unit 12 attempts to acquire a response until it is time to turn on the next optotype. If a response has been acquired in step S24 (if Yes), or if it is time to turn on the next optotype in step S26 (if Yes), the acquisition unit 12 proceeds to step S28.

[0065] In step S28, the determination unit 13 calculates the response time from when the optotype is illuminated until the acquisition unit 12 acquires a response. FIG. 12(b) is a time chart showing the illumination of the optotype and the response. In FIG. 12(b), the horizontal axis represents elapsed time, and the vertical axis represents the illumination of the optotype and the ON / OFF of the subject's response. As shown in FIG. 12(b), when the subject recognizes that the optotype is illuminated, the subject operates the input unit 50, turning the response ON. Therefore, the determination unit 13 calculates the times T10, T12, and T14 from when the optotype is illuminated until the acquisition unit 12 acquires a response as the response time. Generally, the response times T10, T12, and T14 are not constant and vary. Furthermore, if the acquisition unit 12 has not acquired a response, the determination unit 13 determines a time longer than the sum of the predetermined times T1 and T2 as the reaction time. For example, if the predetermined time T1 is 0.2 seconds, the predetermined time T2 is 0.7 to 1.0 seconds, and no response is obtained when the target is lit for the third time, the judgment unit 13 determines that the response time when the target is lit for the third time is 1.3 seconds.

[0066] Even if the subject is instructed not to blink during the test, if the dry eye symptoms are severe, the subject may blink unconsciously or consciously out of curiosity. In the case of natural vision, the subject may be able to recognize the optotype even if the eyes are slightly open, such as with half-closed eyes. However, when the optotype is projected directly onto the retina 61 using Maxwellian vision, the optotype in that part of the visual field becomes invisible when the eyes are half-closed. In addition, by shortening the interval between illumination of the optotype, the subject will not be able to respond to the illumination of the optotype if they blink. Therefore, when the acquisition unit 12 fails to acquire a response, it can be assumed that the subject has blinked.

[0067] Next, the projection control unit 11 determines whether to end the projection of the test image (step S30). For example, the projection control unit 11 determines to end the projection of the test image when a predetermined time (e.g., 20 seconds) has elapsed since the initial (first) lighting of the optotype. The projection control unit 11 may also determine to end the projection of the test image when the number of times the optotype has been lit reaches a predetermined number. If the projection of the test image is not to be ended and the illumination of the optotype continues (if No), the process returns to step S22.

[0068] On the other hand, if the projection of the test image is to be terminated (if Yes), the determination unit 13 uses the response times calculated in step S28 for each illumination of the optotype to calculate a response time difference, which is the absolute value of the difference between the response time for the nth illumination of the optotype (n is an integer equal to or greater than 2) and the response time for the (n-1)th illumination of the optotype (step S32). For example, if the response time T12 for the second illumination is 0.6 seconds and the response time T10 for the first illumination is 0.3 seconds, the response time difference is calculated to be 0.3 seconds. For example, if the response time T14 for the fourth illumination is 0.5 seconds and the response time for the third illumination is 1.3 seconds (when no response was obtained), the response time difference is calculated to be 0.8 seconds.

[0069] Next, the determination unit 13 calculates the average value and standard deviation of the response time differences for all of the targets that have been repeatedly illuminated (step S34).

[0070] Next, the determination unit 13 determines whether the subject has dry eye based on the average value and standard deviation of the response time differences calculated in step S34 (step S36). Next, the determination unit 13 causes the display unit 30 to display the test results of dry eye determined in step S36 (step S38).

[0071] [Experiment 2] Here, an experiment verifying that dry eye can be diagnosed based on the average value and standard deviation of response time differences will be described. In the experiment, the visual target was repeatedly illuminated for each of multiple subjects, and the average value and standard deviation of response time differences were calculated. Furthermore, cases in which a response could not be obtained from the subject despite the visual target being illuminated were identified as a non-response, and the ratio of the number of times a response was not obtained to the number of times the visual target was illuminated (number of times a response was not obtained / number of times the visual target was illuminated) was calculated as the NG rate. As described above, when a response could not be obtained, it is considered that the subject was blinking, and therefore a high NG rate is considered to indicate severe dry eye symptoms.

[0072] 13(a) shows the experimental results of the average value of the response time difference versus the NG rate, and FIG. 13(b) shows the experimental results of the standard deviation of the response time difference versus the NG rate. As shown in FIGS. 13(a) and 13(b), it can be seen that there is a correlation between the NG rate and the average value and standard deviation of the response time difference. Therefore, when the average value and standard deviation of the response time difference are large, it can be said that the symptoms of dry eye are severe.

[0073] 14(a) shows the experimental results of the standard deviation of response time differences relative to the average value of response time differences. As shown in FIG. 14(a), the average value and standard deviation of response time differences were highly correlated, and the results were divided into three groups. Group A had a small average value and standard deviation of response time differences, so it can be determined that it did not have dry eye (negative). Group C had a large average value and standard deviation of response time differences, so it can be determined that it had severe dry eye symptoms. Group B had an average value and standard deviation of response time differences between Group A and Group C, so it can be determined that it had mild or moderate dry eye symptoms.

[0074] Figure 14(b) shows the experimental results of the frequency of response time difference vectors. The response time difference vector is the square root of the sum of the square of the average value of the response time difference and the square of the standard deviation of the response time difference. As shown in Figure 14(b), the response time difference vectors were divided into three groups A, B, and C. Therefore, when determining whether or not there is dry eye, the response time difference vector can be used as a determination index for dry eye.

[0075] Therefore, in step S36 of FIG. 11, the determining unit 13 can determine whether the subject has dry eye based on the average value and standard deviation of the response time differences.

[0076] According to the second embodiment, as shown in FIG. 11 , the projection unit 20 projects a test image in which a visual target is repeatedly illuminated (steps S20 to S30). The acquisition unit 12 acquires the subject's response for each of the repeatedly illuminated visual targets (step S24). The determination unit 13 calculates a response time difference, which is the difference between the response time from illumination of the visual target for the nth time (n is an integer equal to or greater than 2) until acquisition of the response by the acquisition unit 12, and the response time from illumination of the visual target for the (n-1)th time until acquisition of the response by the acquisition unit 12 (step S32). The determination unit 13 calculates the average and standard deviation of the response time differences for the repeated illumination of the visual target (step S34). The determination unit 13 determines whether or not the subject has dry eye based on the average and standard deviation of the response time differences (step S36). This allows for dry eye testing even when the subject blinks unconsciously or consciously. Furthermore, since the dry eye test is performed based on the subject's response, the dry eye test is performed in accordance with the subject's awareness, making it easier for the subject to accept the dry eye test results.

[0077] In Example 2, the determination unit 13 calculates the square root of the sum of the square of the average value of the response time differences and the square of the standard deviation of the response time differences, and determines whether or not there is dry eye based on the square root value. This allows for easy testing for dry eye, as shown in Figure 14, by dividing the patients into groups based on the severity of dry eye symptoms.

[0078] In Example 2, when the acquisition unit 12 cannot acquire a response from the time when the optotype is lit to the time when the next optotype is lit (the third time when the optotype is lit in FIG. 12( b )), the determination unit 13 determines, as the response time, a time that is longer than the sum of the time when the optotype is lit and the time when the next optotype is turned off. This makes it possible to test for dry eye even if the subject blinks unconsciously or consciously.

[0079] In Example 1, its modified example, and Example 2, the cases where the examination device acquires the subject's response to the examination image (step S14 in FIG. 9 , step S24 in FIG. 11 ), determines whether or not there is dry eye based on the subject's response (step S16 in FIG. 9 , step S36 in FIG. 11 ), and displays the dry eye examination results on the display unit 30 (step S18 in FIG. 9 , step S38 in FIG. 11 ) have been described as examples, but the present invention is not limited to this. These operations may also be performed by the examiner.

[0080] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

[0081] 10...controller, 11...projection controller, 12...acquisition unit, 13...determination unit, 20...projection unit, 21...light source, 22...lens, 23...scanning unit, 24...reflection mirror, 25...projection mirror, 26...lens, 30...display unit, 40...storage unit, 50...input unit, 60...eye, 61...retina, 62...pupil, 63...crystalline lens, 64...cornea, 70, 70a...light rays, 72...convergence point, 74...convergence point, 75...foreign matter, 80...inspection image, 81...background, 82...numbers, 83...letters, 84...pattern, 90...camera, 91...pseudo-eye optical system, 92...screen, 93...retinal projection device, 95...thread, 96...transparent vinyl sheet, 100...inspection device

Claims

1. An examination device comprising: a projection unit that projects a test image onto a subject's retina by directly irradiating the retina with light emitted from a light source; an acquisition unit that acquires the subject's response to the test image; and a judgment unit that judges whether or not there is dry eye based on the response.

2. The examination device according to claim 1, wherein the determination unit determines whether or not there is dry eye based on the response time from the start of projection of the examination image to the response.

3. The testing device according to claim 2, further comprising a memory unit that stores information indicating the correspondence between time and dry eye, wherein the judgment unit judges whether or not there is dry eye based on the response time and the information.

4. The examination device described in claim 2 or 3, wherein the acquisition unit acquires the response from the subject when the subject continues to look at the visual target in the examination image without blinking and feels that the appearance of the visual target has changed.

5. The inspection device according to claim 4, wherein the projection unit projects the inspection image with the number of seconds from the start of projection of the inspection image displayed as the visual target.

6. The examination device described in claim 4, wherein the projection unit projects the examination image in which a Landolt ring corresponding to the subject's visual acuity is displayed as the visual target, and the acquisition unit acquires the response from the subject when the subject feels that it is becoming difficult to distinguish the orientation of the Landolt ring.

7. The examination device described in claim 1, wherein the projection unit projects the test image displaying a Landolt ring as a visual target whose orientation changes every predetermined time, the acquisition unit acquires the response in which the subject continues to look at the Landolt ring without blinking and answers the orientation of the Landolt ring, and the judgment unit judges whether or not there is dry eye based on the time from the start of projection of the test image to the time when the Landolt ring is displayed when the answer has been incorrect a predetermined number of times.

8. The examination device of claim 1, wherein the projection unit projects the test image in which a visual target is repeatedly illuminated; the acquisition unit acquires the subject's response for each of the visual targets that are repeatedly illuminated; and the judgment unit calculates a response time difference that is the difference between the response time from when the visual target is illuminated for the nth time (n is an integer of 2 or more) until the acquisition unit acquires the response, and the response time from when the visual target is illuminated for the (n-1)th time until the acquisition unit acquires the response, calculates an average value and standard deviation of the response time differences for the repeated illumination of the visual target, and makes a judgment about dry eye based on the average value of the response time differences and the standard deviation of the response time differences.

9. The testing device according to claim 8, wherein the determining unit calculates the square root of the sum of the square of the average value of the response time differences and the square of the standard deviation of the response time differences, and determines whether or not there is dry eye based on the value of the square root.

10. The inspection device according to claim 8 or 9, wherein, if the acquisition unit is unable to acquire the response between the time when the target is lit and the time when the next target is lit, the determination unit determines the response time to be a time longer than the sum of the time when the target is lit and the time when the target is turned off until the next target is lit.

11. An examination method comprising the steps of: irradiating a light beam emitted from a light source directly onto a subject's retina to project a test image onto the retina; acquiring the subject's response to the test image; and determining whether or not the subject has dry eye based on the response.

Images