Visual field testing device, visual field testing method, and program

Abstract

Provided is a visual field testing device that enables measurement of retinal sensitivity without increasing the burden on a subject. The present invention is provided with: a light irradiation unit that irradiates the retina of a subject with stimulation light; a projection control unit that causes the light irradiation unit to perform irradiation with the stimulation light with a testing pattern in which the intensity of the stimulation light is increased to a predetermined luminance over time; a switch that is operated by the subject having visually recognized the stimulation light; and a calculation unit that calculates the intensity of the stimulation light that can be visually recognized by the subject on the basis of the timing at which the switch is operated in the testing pattern.

Description

Visual field testing device, visual field testing method, and program

[0001] The present disclosure relates to a visual field testing device, a visual field testing method, and a program.

[0002] A visual field testing device has been known in the past that presents a fixation point in a housing that covers the visual field of a subject, randomly displays bright spots (targets) in the subject's visual field while the subject is looking at the fixation point, and tests whether the subject can see them. Note that Patent Literature 1 discloses a technology that determines the intensity of stimulus light to be used during the test based on a threshold value measured in advance from the subject's response.

[0003] Japanese Patent Application Publication No. 8-117186

[0004] In conventional visual field testing devices, the intensity of the stimulus light applied to each part of the retina is fixed, making it impossible to measure the retinal sensitivity of each individual subject. It is also possible to switch the intensity of the stimulus light and test whether the subject was able to see at each intensity. However, this would increase the test time and place a greater burden on the subject.

[0005] Therefore, in one aspect, the present invention aims to provide a visual field testing device that can measure retinal sensitivity without increasing the burden on the subject.

[0006] In one aspect, a visual field testing device is provided, comprising: a light irradiation unit that irradiates stimulus light onto the retina of a subject; a projection control unit that causes the stimulus light to be irradiated from the light irradiation unit in a test pattern that increases the intensity of the stimulus light to a predetermined brightness over time; a switch that is operated by the subject who views the stimulus light; and a calculation unit that calculates the intensity of the stimulus light that is visible to the subject based on the timing at which the switch is operated in the test pattern.

[0007] According to one aspect of the present invention, the absolute value of retinal sensitivity can be measured without increasing the burden on the subject.

[0008] 5 is a diagram showing the configuration of the visual field testing device of the present embodiment. FIG. 6 is a diagram illustrating the appearance of a testing instrument to which the visual field testing device of the present embodiment is applied. FIG. 7 is a diagram showing the configuration of a light irradiation unit. FIG. 8 is a diagram showing a site on the retina to which stimulus light (laser light) is presented. FIG. 9 is a flowchart showing visual field testing processing in the visual field testing device of the present embodiment. FIG. 10 is a flowchart showing reaction time measurement processing for measuring the reaction time of a test subject. FIG. 11 is a flowchart showing calculation processing in a calculation unit. FIG. 12 is a diagram showing an example of the arrangement of a test pattern for stimulus light and a reaction time measurement pattern when a visual field test is performed. FIG. 13 is a diagram showing the count value of the irradiation duration obtained in the reaction time measurement processing of FIG. 5. FIG. 14 is a diagram showing a method for calculating the retinal sensitivity of a specified site on the retina of a test subject. FIG. 15 is a diagram showing an example of advancing the timing of moving the test target to the next site on the retina in accordance with the operation of a switch.

[0009] FIG. 1 is a diagram showing the configuration of a visual field examination device according to this embodiment.

[0010] As shown in Figure 1, the visual field testing device of this embodiment includes a light irradiation unit 11 that irradiates stimulus light onto the retina of the subject, a projection control unit 12 that causes the stimulus light to be irradiated from the light irradiation unit 11 in a test pattern that increases the intensity of the stimulus light to a predetermined luminance over time, a switch 13 that is operated by the subject who views the stimulus light, and a calculation unit 14 that calculates the intensity of the stimulus light that is visible to the subject based on the timing at which the switch 13 is operated in the test pattern.

[0011] In addition, the visual field examination device of this embodiment is equipped with a memory unit 15 that stores data related to the examination and data such as the examination results calculated by the calculation unit 14, and an output unit 16 that outputs the examination results stored in the memory unit 15.

[0012] The visual field examination apparatus of this embodiment can be configured using a computer on which a predetermined program is installed.

[0013] FIG. 1A is a diagram illustrating the appearance of an examination instrument to which the visual field examination device of this embodiment is applied. In the example of FIG. 1A, the light irradiation unit 11 is housed inside the examination instrument. Note that while FIG. 1A shows an examination instrument compatible with both the left and right eyes, an examination instrument compatible with testing each eye separately can also be used. The configuration of the examination instrument is arbitrary, and for example, an examination instrument in which the light irradiation unit 11 is built into a device shaped like goggles or glasses that can be worn by the subject can also be used.

[0014] 1A includes a frame 102, adjustment members 103 and 104, a base 105, support units 106a and 106b, image projection units 107a and 107b, a pedestal 108, and image capture units 109a and 109b. The pedestal 108 is provided on the base 105, and both ends of the frame 102 are fixed to the upper surface of the base 105.

[0015] The image projection units 107a and 107b are supported by the support units 106a and 106b. The image projection units 107a and 107b irradiate the left and right eyes of the test subject, whose visual field, visual acuity, visibility, etc. are to be tested, with stimulus light by the light irradiation unit 11, and project a projection image including a test image onto the retina of the test subject.

[0016] The adjustment member 103 moves the support portions 106a and 106b, which support the image projection portions 107a and 107b, in the Y-axis direction shown in Fig. 1A. The adjustment member 104 moves the image projection portion 107 along the support portions 106 in the Z-axis direction shown in Fig. 1A.

[0017] The visual inspection device 100 is configured such that the subject's chin and forehead are in contact with the base 108 and the frame 102, respectively, and the image projection unit 107 is brought close to the eyeballs by the adjustment members 103 and 104 so that the subject is looking into the image projection units 107a and 107b, and the inspection is performed with this state in mind.

[0018] 2 is a diagram showing the configuration of the light irradiating unit 11. The light irradiating unit 11 irradiates stimulating light (laser light) onto the retina 22 of the eyeball 20 of the subject by utilizing Maxwell's vision.

[0019] 2, the light irradiation unit 11 includes a light source 111, an adjustment unit 112, and an optical system 113. The optical system 113 includes a scanning unit 114, a plane mirror 115, and lenses 116 and 117. The scanning unit 114 is, for example, a two-axis MEMS (Micro Electro Mechanical Systems) mirror.

[0020] In the light irradiation unit 11, the numerical aperture (NA) and / or beam diameter of the laser light L emitted by the light source 111 is adjusted in the adjustment unit 112. The laser light L is a visible laser light such as a red laser light, a green laser light, or a blue laser light.

[0021] The laser light L is reflected by a plane mirror 115 and scanned two-dimensionally by the scanning unit 114. The scanned laser light L is irradiated onto the eyeball 20 of the subject via lenses 116 and 117. The laser light L converges near the crystalline lens 21, passes through the vitreous body 23, and is irradiated onto the retina 22. As a result, an image is projected onto the retina 22. The scanning unit 114 oscillates at a relatively high frequency, such as 28 kHz, at which 60 frames of image are projected per second.

[0022] The position of the eyeball 20 relative to the light irradiation unit 11 is adjusted by, for example, adjustment members 103 and 104 so that the laser light L is not eclipsed (blocked) at the position of the pupil of the eyeball 20. For example, by obtaining a positional relationship in which the laser light L diffused by scanning converges near the crystalline lens 21 of the eyeball 20 in the optical axis direction, it becomes possible to form an image over the entire field of view without missing any peripheral portions of the image.

[0023] 3 is a diagram showing the areas on the retina where the stimulating light (laser light) is presented, in which each area is represented by a drawn dot 51.

[0024] As shown in FIG. 3 , stimulus light is presented to a total of 28 locations on the retina 22. The spacing between adjacent locations, both vertically and horizontally, corresponds to a 6-degree angle of the stimulus light projected onto the retina 22 from a convergence point near the center of the crystalline lens 21. A background 52 of a predetermined brightness (gray color) is projected onto a rectangular area containing the 28 locations. While any brightness value can be selected for the background 52, the following description will illustrate an example in which the brightness of the background 52 is set to, for example, a brightness corresponding to a value of 100 out of a total of 256 gradations. Furthermore, a mark 53 indicating the location where the subject will centrally fixate is presented in the center of the area where the 28 locations are distributed. While fixating on the mark 53, the subject operates the switch 13 when he or she recognizes the stimulus light at the 28 locations, thereby performing a visual field test on the subject.

[0025] Next, the operation of the visual field examination device of this embodiment will be described.

[0026] FIG. 4 is a flowchart showing the visual field examination process in the visual field examination device of this embodiment.

[0027] In step S102 of FIG. 4, the projection control unit 12 selects one region from among candidates corresponding to regions on the retina 22 that have not yet been examined.

[0028] In step S104, the projection control unit 12 starts an operation of irradiating the selected area on the retina 22 with stimulus light from the light irradiation unit 11 using a test pattern in which the intensity of the stimulus light is increased over time to a predetermined luminance. For example, in the test pattern, the amount of light at the area is continuously increased by continuously increasing 256 8-bit gradation values ​​from 100 to 256, which corresponds to the luminance of the background 52. The time required to increase the amount of light can be set, for example, within a range of 2 to 4 seconds.

[0029] In step S106, the projection control unit 12 starts counting the time that has elapsed since the operation was started in step S104.

[0030] In step S108, the projection control unit 12 acquires the count value of the elapsed time since counting began in step S106.

[0031] In step S110, the projection control unit 12 determines whether the intensity of the stimulus light has increased to the above-mentioned predetermined brightness based on the count value of the elapsed time acquired in step S108, and if the determination is affirmative, the process proceeds to step S114, and if the determination is negative, the process proceeds to step S112.

[0032] In step S112, the projection control unit 12 determines whether or not the switch 13 has been operated, and if the determination is affirmative, the process proceeds to step S114, and if the determination is negative, the process proceeds to step S110.

[0033] In step S114, the storage unit 15 stores the count value of the elapsed period acquired in step S108 in association with the site on the retina 22.

[0034] In step S118, the projection control unit 12 deletes the region on the retina 22 that is currently being examined from the candidates (regions that can be selected in step S102).

[0035] In step S120, the projection control unit 12 determines whether any candidate areas on the retina 22 (areas that can be selected in step S102) remain, and if the determination is positive, the processing proceeds to step S122, and if the determination is negative, the processing ends.

[0036] In step S122, the projection control unit 12 determines whether or not the irradiation of the stimulus light on the test pattern has finished based on the count value of the elapsed time acquired in step S108, and if the determination is affirmative, the process proceeds to step S102, and if the determination is negative, the process of step S122 is repeated.

[0037] 4, the count values ​​of the elapsed time are acquired and stored for all 28 locations on the retina 22. If the count values ​​of the elapsed time indicate an abnormality (error), the test (steps S104 to S114) may be performed again for that location on the retina 22 to acquire a valid count value of the elapsed time.

[0038] 4 may be performed multiple times (e.g., three times) to improve the accuracy of the test results. In this case, the average value of the count values ​​over the elapsed period acquired for each site on the retina 22 may be used as the final result (count value over the elapsed period) corresponding to that site.

[0039] In this embodiment, stimulus light is emitted from the light emitting unit 11 in a reaction time measurement pattern at a predetermined timing during execution of the process shown in FIG. 4, and the reaction time of the subject is measured.

[0040] 5 is a flowchart showing a reaction time measurement process for measuring the reaction time of a subject. The reaction time measurement process is executed at random timing, for example, during the execution of the process shown in FIG.

[0041] In step S202 of FIG. 5 , the projection control unit 12 causes the light irradiation unit 11 to irradiate a predetermined region on the retina 22 with stimulus light in a reaction time measurement pattern in which the intensity of the stimulus light increases more steeply than in the test pattern. The reaction time measurement pattern is, for example, a pattern in which the luminance of the stimulus light rises instantaneously from the luminance of the background 52 to a predetermined luminance (e.g., a luminance of 256 as a gradation value) and continues for a predetermined duration. Furthermore, the region on the retina 22 to which the reaction time measurement pattern is applied is, for example, a region in the central region 51A shown in FIG. 3 (one of four regions in the example of FIG. 3 ). This allows for more accurate measurement of the subject's reaction time.

[0042] In step S204, the projection control unit 12 starts counting the duration of irradiation of the stimulus light, which has been started to be irradiated in step S202.

[0043] In step S206, the projection control unit 12 acquires the count value of the duration of irradiation started in step S204.

[0044] In step S208, the projection control unit 12 determines whether the above-mentioned predetermined duration has elapsed based on the duration count value obtained in step S108, and if the determination is positive, proceeds to step S212, and if the determination is negative, proceeds to step S210.

[0045] In step S210, the calculation unit 14 determines whether the switch 13 has been operated. If the determination is affirmative, the process proceeds to step S212, and if the determination is negative, the process proceeds to step S206.

[0046] In step S212, the storage unit 15 stores the count value of the irradiation duration acquired in step S206, and the process ends.

[0047] In this embodiment, the reaction time measurement process shown in Fig. 5 is performed multiple times while the process shown in Fig. 4 is being performed, and multiple count values ​​of the irradiation duration are obtained. This allows the reaction time of the subject to be accurately determined. The reaction time measurement process may be performed any number of times, but may be performed, for example, three to five times. If the count value of the irradiation duration obtained in step S206 indicates an abnormality (error), the number of times the reaction time measurement process is performed may be increased to ensure a number of valid count values ​​of the irradiation duration.

[0048] FIG. 6 is a flowchart showing the calculation process in the calculation unit.

[0049] In step S302 of Fig. 6, the calculation unit 14 acquires the data of the corresponding subject stored in the process of Fig. 4 from the storage unit 15. The data of the subject includes a count value of the irradiation duration (step S212) and a count value of the elapsed period (step S114).

[0050] In step S304, the calculation unit 14 calculates the reaction time of the subject based on the count values ​​of the irradiation durations acquired in step S302. The reaction time can be calculated, for example, as the average value of the count values ​​of the irradiation durations. Furthermore, if the count values ​​of the irradiation durations include values ​​that are considered to be erroneous (values ​​that are too small or too large), the count values ​​may be excluded, and the average value of the remaining count values ​​may be calculated as the reaction time.

[0051] In step S306, the calculation unit 14 calculates the retinal sensitivity (the intensity of the stimulus light visible to the subject) for each part on the subject's retina 22 based on the count value of the elapsed period acquired in step S302, and then ends the processing.

[0052] FIG. 7 is a diagram showing an example of the arrangement of a stimulus light test pattern and a reaction time measurement pattern when a visual field test is performed.

[0053] In the example of FIG. 7 , basically, the irradiation of stimulus light by the test pattern is repeated sequentially at different sites on the retina 22 at a fixed cycle (e.g., 2 to 4 seconds) (see step S122). However, within that cycle, the reaction time measurement process shown in FIG. 5 is inserted as an interrupt process (not shown in FIG. 4 ). In FIG. 7 , irradiation of stimulus light by the test pattern begins at times t0, t1, and t3, and irradiation of stimulus light by the reaction time measurement pattern is performed between times t2 and t3. The intensity of the test pattern continuously increases from a gradation value of 100, which corresponds to the luminance of the background 52 ( FIG. 3 ), to a gradation value of 256. The intensity of the stimulus light by the reaction time measurement pattern corresponds to a gradation value of 256.

[0054] FIG. 8 is a diagram showing the count value of the irradiation duration acquired in the reaction time measurement process of FIG.

[0055] In the example of Fig. 8, at time t11, the intensity of the stimulus light from the reaction time measurement pattern rises from a gradation value of 100 to 256, and at time t3, the intensity returns from a gradation value of 256 to 100. If the switch 13 is operated at time t12 (if the determination in step S210 is positive), the count value of the duration of irradiation is acquired (stored) as a count value Δt.

[0056] FIG. 9 is a diagram showing a method for calculating the retinal sensitivity of a predetermined site on the retina of a subject.

[0057] As described above, in the calculation process shown in FIG. 6, the reaction time of the subject is calculated based on the count value of the irradiation duration.

[0058] In the example of FIG. 9, the reaction time of the subject corresponding to the count value of the irradiation duration is shown as reaction time ΔT.

[0059] 9 , the intensity of the stimulus light generated by the test pattern gradually increases from a gradation value of 100 at time t1, and reaches a gradation value of 256 at time t2. If the switch 13 is operated at time t21, the calculation unit 14 determines that the subject recognized the stimulus light at time t22, which is a reaction time ΔT before time t21. Therefore, the calculation unit 14 calculates the gradation value X of the stimulus light corresponding to time t22 as the retinal sensitivity (the intensity of the stimulus light visible to the subject) of the corresponding site on the retina 22.

[0060] Note that the switch 13 may be operated after the intensity of the stimulus light from the test pattern reaches the gradation value 256, i.e., after the time when irradiation of the stimulus light from the test pattern ends (time t2). In Fig. 9, if the switch 13 is operated at time t23, the calculation unit 14 considers that the subject recognized the stimulus light at time t24, which is a time point that is a reaction time ΔT before time t23. Therefore, in this case, the gradation value X0 of the stimulus light corresponding to time t24 is calculated as the retinal sensitivity (the intensity of the stimulus light visible to the subject) of the corresponding site on the retina 22.

[0061] The retinal sensitivity of each site on the retina 22 calculated by the calculation unit 14 is stored in the storage unit 15, and the stored data is output by the output unit 16. For example, each site on the retina 22 can be displayed as a two-dimensional chart as shown in Fig. 3, and the retinal sensitivity of each site in the chart, i.e., the intensity (gradation value) of the stimulus light visible to the subject, can be displayed in a display mode corresponding to the retinal sensitivity of the corresponding site. For example, each area in the chart may be displayed in a display color (e.g., a display color with different gradations) corresponding to the retinal sensitivity of the corresponding site.

[0062] FIG. 10 is a diagram showing an example in which the timing of shifting the test subject to the next part on the retina is advanced in response to the operation of a switch.

[0063] When the switch 13 corresponding to the selected area is operated, the projection control unit 12 may move the test object to the next area on the retina 22 before increasing the brightness of the stimulus light from the test pattern to the end.

[0064] In the example of FIG. 10 , the stimulus light from the test pattern is initially set to gradually increase in tone value from 100 starting at time t0 and reach a tone value of 256 at time t1. However, if the subject operates the switch 13 at time t31, it is assumed that the subject recognized the stimulus light at time t32, which is a reaction time ΔT before time t31. The tone value X1 of the stimulus light corresponding to time t32 is calculated as the retinal sensitivity (the intensity of the stimulus light visible to the subject) of the corresponding area on the retina 22. In this case, there is no longer any need to continue irradiating the stimulus light from the test pattern after time t31, when the switch 13 is operated. Therefore, in the example of FIG. 10 , irradiation of the stimulus light from the test pattern is stopped at time t33, and the test subject is moved to the next area on the retina 22.

[0065] By adopting such an operation, if the subject operates the switch 13 early, the subject can quickly move on to the next area on the retina 22. This makes it possible to shorten the examination time and reduce the burden on the subject.

[0066] As described above, the visual field testing device of this embodiment uses a test pattern that increases the intensity of stimulus light over time to a predetermined luminance, and calculates the intensity of stimulus light that the subject can see based on the timing at which the subject operates the switch. This makes it possible to calculate the retinal sensitivity of each part of the retina 22 of each subject without increasing the burden on the subject. This also makes it easy to distinguish between diseases caused by opacity, such as cataracts, and diseases caused by visual field defects, such as glaucoma.

[0067] Furthermore, even for subjects with low sensitivity, it is possible to prevent cases where they are unable to see anything from start to finish during the examination, thereby avoiding frustration and burden on the subject.

[0068] Although each embodiment has been described in detail above, it is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of components of the above-described embodiments.

[0069] 11 Light irradiation unit 12 Projection control unit 13 Switch 14 Calculation unit 15 Storage unit 16 Output unit

Claims

1. A visual field testing device comprising: a light irradiation unit that irradiates stimulating light onto a subject's retina; a projection control unit that causes the light irradiation unit to irradiate the stimulating light in a test pattern that increases the intensity of the stimulating light over time to a predetermined luminance; a switch that is operated by the subject who views the stimulating light; and a calculation unit that calculates the intensity of the stimulating light visible to the subject based on the timing at which the switch is operated in the test pattern.

2. The visual field testing device of claim 1, wherein the projection control unit causes the light irradiation unit to irradiate the stimulus light in a reaction time measurement pattern in which the intensity of the stimulus light increases more steeply than in the test pattern, and the calculation unit calculates the intensity of the stimulus light visible to the subject based on the timing at which the switch is operated in the reaction time measurement pattern and the timing at which the switch is operated in the test pattern.

3. The visual field examination device of claim 2, wherein the projection control unit randomly and sequentially selects one of a plurality of locations on the retina and causes the light irradiation unit to irradiate the selected location with the stimulus light in the test pattern.

4. The visual field examination device according to claim 3, wherein the projection control unit inserts the reaction time measurement pattern at random timing during the examination using the test pattern.

5. A visual field testing device as described in claim 3, wherein, when the switch corresponding to the selected area is operated, the projection control unit shifts the test subject to the next area selected from among multiple areas on the retina before increasing the intensity of the stimulus light to the specified brightness.

6. A visual field testing method comprising: a projection control step of irradiating a stimulus light in a test pattern in which the intensity of the stimulus light is increased over time to a predetermined luminance; and a calculation step of calculating the intensity of the stimulus light visible to a subject based on the timing at which a switch operated by the subject who visually recognizes the stimulus light in the test pattern is operated.

7. A program that causes a computer to execute the following steps: a projection control step of irradiating a stimulus light in a test pattern in which the intensity of the stimulus light is increased over time to a predetermined luminance; and a calculation step of calculating the intensity of the stimulus light visible to a subject based on the timing of the operation of a switch operated by the subject who visually recognizes the stimulus light in the test pattern.

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