CN100528070C

CN100528070C - Perimeter

Info

Publication number: CN100528070C
Application number: CNB200580030851XA
Authority: CN
Inventors: 田舍片悟; 村上宗司; 福岛省吾; 福永秀雄; 田渊昭雄; 可儿一孝; 前田史笃
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 2004-09-15
Filing date: 2005-09-05
Publication date: 2009-08-19
Anticipated expiration: 2025-09-05
Also published as: CN101018501A

Abstract

A diopsimeter comprises a display (1), an infrared light-emitting diode (2), a CCD camera (3), a half-silvered mirror (4), an image processing device (5), a computer (6), and an operation switch (7). The computer (6) displays a fixing target for fixing the line of sight of a subject and light stimulus targets for giving light stimulus to the pupil of the subject at predetermined positions of the display (1). The infrared light-emitting diodes (2) projects infrared radiation toward the eye ball of the subject. The CCD camera (3) images the eye ball of the subject by using the projected infrared radiation. The image processing device (5) detects the diameter of the pupil of the subject from captured image. The computer (6) measures the field of view from the variation of the detected pupil diameter. The characteristic point of the invention is that the display (1) is so constructed that the luminance of the background of the screen and the luminances of the light stimulus targets can be independently adjusted.

Description

Perimeter

Technical Field

The present invention relates to a perimeter for measuring the visual field of a subject.

Background

Visual field examination (i.e., visual field measurement) is performed to diagnose the contraction of the visual field, which is a symptom of diseases such as glaucoma. In conventional visual field measurement, the visual field of a subject is measured by displaying an eye-target at a specific position in front of the subject's eye and then letting the subject answer whether or not the eye-target is seen. This examination is a subjective examination based on subjective answers of the subject, and the visual field range of the subject is determined by measuring the visual field a plurality of times while changing the display position of the optotype one by one. In such a subjective examination, there is a problem in that the examination result is easily affected by the physical condition and attention of the subject, and the like, and accurate examination cannot be performed. Further, since a series of operations of displaying the optotypes and then letting the subject answer must be repeated a plurality of times, there is also a problem in that it takes a long time to perform such examination and the subject is burdened.

The Japanese ophthalmic society (Folia opthalmologica Japonica) (Vol.49, No. 9, page 733 and 737, 1998) discloses a perimeter that enables objective perimeter measurements independent of subjective responses of subjects. In such a perimeter, in order to measure the visual field of a subject, a fixed optotype is projected on a screen provided in front of the eye of the subject, then light stimulation optotypes are projected one by one on a plurality of positions on the screen under the condition that the subject gazes at the fixed optotype, thereby providing light stimulation to the retina of the subject, and then a miotic response of the pupil due to the light stimulation (i.e., light reflection of the pupil) is detected.

Further, japanese unexamined patent publication No.5-146404 and japanese unexamined patent publication No.2004-216118 disclose a perimeter that objectively measures the visual field of a subject by displaying a fixed optotype and a light stimulation optotype with a light emitting device such as a light emitting diode, and detecting whether or not light reflection of the pupil occurs when the light stimulation is provided to the subject.

In such an objective perimeter, the darker the background brightness relative to the light-stimulated optotype, the easier it is to detect the light reflection at the pupil. However, if the background brightness is too dark, the light of the light stimulation optotype is scattered, and thus the light stimulation cannot be provided to the accurate position of the retina of the subject. In addition, the pupil of the subject needs a long time to adapt to the darkness of the background, so that the examination time becomes long. On the other hand, if the background luminance is too bright, the luminance difference between the background and the light stimulus optotype becomes small, the light reflection of the pupil also becomes small, and therefore, the detection of the response becomes difficult. Further, it is preferable to change the size of the light stimulation optotype and the stimulation intensity thereof according to the subject.

As described above, in the objective perimeter, it is preferable that the background brightness, the optotype size, and the like can be arbitrarily adjusted. However, in the above-described conventional perimeter, since the optotype is projected on the screen or the light-emitting diode is used to display the light-stimulated optotype, there is a problem in that the background brightness, the optotype brightness, and the optotype size cannot be easily adjusted.

Disclosure of Invention

In view of the above problems, it is an object of the present invention to provide an objective perimeter capable of easily adjusting background brightness, target size, and the like, and capable of quickly and accurately measuring a field of view.

The perimeter of the present invention comprises: the visual target measuring device comprises a display device, a visual target control device, an infrared light-emitting device, an image pick-up device, a shell, a pupil detection device and a visual field measuring device. The optotype control device displays a fixed optotype for fixing a line of sight of a subject and a light stimulation optotype for providing light stimulation to a pupil of the subject at a plurality of predetermined positions on the display device. The infrared light emitting device emits infrared light to the eye of the subject. The image pickup device picks up an image of the eye of the subject by using the infrared light emitted by the infrared light emitting device. The housing accommodates the display device, the infrared light emitting device, and the image pickup device therein, and has a peephole through which the examinee views the fixed optotype and the light stimulation optotype displayed on the display device from the outside. The pupil detection device detects the pupil diameter of the subject based on the image captured by the imaging device. When the optotype control device displays the light stimulus optotype under the condition that the subject looks at the fixed optotype, the visual field measuring device measures the visual field of the subject based on the change in the pupil diameter of the subject detected by the pupil detecting device.

The invention is characterized in that: the display device comprises a display device capable of adjusting the background brightness of a screen and the brightness of the light stimulation sighting target respectively. Therefore, the perimeter of the present invention can easily adjust the background brightness of the screen and the brightness of the light stimulus optotype, and can set the background brightness of the screen and the brightness of the light stimulus optotype to optimum values. Of course, the perimeter of the present invention can display the optimal optotype according to the subject, because the size of the optotype and the display time of the optotype can be easily changed. Therefore, the perimeter of the invention can measure the field of view quickly and accurately.

Preferably, the perimeter further comprises a display position adjustment means capable of adjusting the position of the display means in a vertical direction and/or a horizontal direction and/or a front-rear direction with respect to the peephole. By providing the display position adjusting means, it is possible to move the display means to the optimum position according to the positions of the eyes of the examinee and the eyesight of the examinee.

Preferably, the perimeter further includes an image pickup apparatus adjustment device capable of adjusting an image pickup position and an image pickup direction of the image pickup device. By providing the image pickup apparatus adjusting means, the position and angle of the image pickup means can be adjusted according to the pupil of the subject. In this case, it is more preferable that the perimeter further includes an imaging apparatus control means for adjusting an imaging position and an imaging direction of the imaging means by the imaging apparatus adjustment means based on a detection result of the pupil detection means so that a pupil diameter of the subject reaches a peak. By providing the camera control means, the camera means can be automatically adjusted to the optimal position and the optimal orientation.

Preferably, the perimeter further includes an operation switch that outputs an operation signal to the perimeter measurement device in response to an operation of the subject, the perimeter measurement device measuring the perimeter based on a change in pupil diameter of the subject and the operation signal input from the operation switch. In this case, subjective visual field inspection can be performed in addition to objective visual field inspection, thereby improving the reliability of the measurement result.

Preferably, the emissivity of the inner surface of the housing is generally 1 (i.e. its reflectivity is zero). In this case, the light emitted from the display device in the housing is almost entirely absorbed by the inner surface of the housing, so that the light stimulus can be prevented from being provided to an unnecessary position of the pupil, and the accuracy of measurement can be improved.

For light-stimulated optotypes, light stimulation that flashes briefly in pulses is typically used. Preferably, the optotype control means continuously displays the pulsed light-stimulated optotype on the display means at least twice. By displaying the pulsed light stimulation continuously at least twice, the change in the pupil diameter can be enlarged even when the light quantity is the same, as compared with the case where the pulsed light stimulation is displayed only once. Therefore, the field of view is easily measured.

Incidentally, even in a state without light stimulation, the size of the pupil diameter drifts, and therefore such a situation may occur: it is difficult to judge whether the change in pupil diameter is caused by light stimulation. In this case, preferably, the optotype control means displays a light stimulus optotype whose light intensity periodically changes on the display means. By the light stimulating optotype showing the periodical change of the light intensity, when the change of the pupil diameter is caused by the light stimulating optotype, the pupil diameter is periodically changed in a manner synchronized with the period of the light. Therefore, it is easy to judge whether or not the change in pupil diameter is caused by the light stimulus, and the reliability of the measurement result can be improved.

The light stimulation optotype of which the light intensity varies periodically may be a light pulse train or an optotype of which the light intensity varies in a sine wave manner.

In this case, it is preferable that the optotype control means has a function of changing a light intensity cycle of the light stimulation optotype or a function of changing a size of the light stimulation optotype. By providing such a function, an optimal optotype can be displayed according to the subject.

Further, when a light stimulus target in which the light intensity periodically changes is displayed, it is preferable that the visual field measuring device has a function of calculating the change width of the pupil diameter from the fluctuation range of the pupil diameter or the amplitude of the pupil diameter. When the pupil diameter varies periodically with the light intensity, local minima and maxima of the pupil diameter are easily obtained. Therefore, by defining the difference between the local minimum value and the local maximum value of the pupil diameter, that is, the fluctuation range of the pupil diameter (or the amplitude of the pupil diameter, that is, half of the fluctuation range) as the variation width of the pupil diameter, the variation width of the pupil diameter can be easily obtained. When a plurality of fluctuation ranges are available, the average thereof may be defined as the variation amplitude of the pupil diameter. In this case, fluctuation (unevenness) of data can be alleviated.

Further, preferably, the visual field measuring device calculates a ratio between the above-obtained variation width of the pupil diameter and the light intensity of the light stimulation optotype, and measures the visual field sensitivity of the subject based on the ratio. That is, when the change in the pupil diameter is small relative to the light intensity, it is possible to judge that the sensitivity of the visual field has degraded, and in this way, measure the sensitivity of the visual field based on the ratio.

Further, it is preferable that the visual field measuring device has a function of calculating synchronism between a light intensity cycle of the light stimulation optotype and a change cycle of the pupil diameter of the subject. In this case, the synchronicity may be used as one of information for judging the reliability of the measurement result.

Further, it is preferable that the visual field measuring device has a function of determining whether or not the position of the light stimulation optotype is displayed in a normal visual field region of the subject based on a change in pupil diameter of the subject. In this case, it is possible to automatically judge whether or not the position of the display light stimulus optotype is a normal visual field region of the subject.

Preferably, the optotype control means has a function of changing the color of the light stimulation optotype. In this case, the retinal cells can be examined for cone cells that respond to color.

Drawings

Fig. 1 is a schematic view showing the constitution of a perimeter according to an embodiment of the present invention;

FIG. 2 is a schematic view illustrating an internal configuration of the perimeter shown in FIG. 1;

FIG. 3 is a schematic view illustrating a method of mounting a liquid crystal display of the perimeter shown in FIG. 1;

fig. 4A is a schematic view illustrating a method of mounting a CCD camera of the perimeter shown in fig. 1;

FIG. 4B is a schematic view for explaining a method of mounting a CCD camera of the perimeter shown in FIG. 1

FIG. 5 is a schematic diagram showing one example of a screen of a liquid crystal display of the perimeter shown in FIG. 1;

fig. 6A is a schematic view showing an example of an image taken by the CCD camera in the perimeter shown in fig. 1;

FIG. 6B is a schematic diagram illustrating an example of pupil diameters detected in the perimeter of FIG. 1;

FIG. 7 is a schematic view illustrating the measurement principle of the perimeter shown in FIG. 1;

FIG. 8 is a schematic view showing an example of the position of the displayed visual target in the perimeter of FIG. 1;

FIG. 9A is a diagram illustrating an example of a miosis ratio measured in the perimeter of FIG. 1;

FIG. 9B is a diagram illustrating another example of the miosis measured in the perimeter of FIG. 1;

fig. 10 is a schematic diagram showing measurement results of static field of view measurements on the subject of fig. 9A and 9B simultaneously in gray scale;

FIG. 11A is a diagram showing another example of the miosis measured in the perimeter of FIG. 1;

fig. 11B is a schematic diagram showing measurement results at gray scale while performing static field of view measurements on the subject of fig. 11A;

FIG. 12A is a schematic view showing an example of a photostimulation optotype in the perimeter of FIG. 1;

FIG. 12B is a schematic view showing another example of the photostimulation optotype in the perimeter of FIG. 1;

FIG. 13 is a schematic view showing another example of the photostimulation optotype in the perimeter of FIG. 1;

FIG. 14 is a schematic view showing another example of the photostimulation optotype in the perimeter of FIG. 1;

fig. 15 is a schematic view showing another example of the photostimulation optotype in the perimeter of fig. 1.

Detailed Description

Hereinafter, the present invention is described in detail with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the configuration of the perimeter of the present embodiment. The perimeter includes: a liquid crystal display 1, an infrared light emitting diode 2, a CCD camera 3, a half mirror 4, an image processing device 5, a computer 6, and an operation switch 7. As shown in fig. 2, the liquid crystal display 1, the infrared light emitting diode 2, the CCD camera 3, and the half mirror 4 are housed in a box-shaped case 8. A peephole 10 is formed on one side surface of the case 8, and the subject can see the liquid crystal display 1 mounted in the case 8 through the peephole 10; a chin rest base 9 is also mounted on this side for supporting the subject's chin.

The liquid crystal display 1 (display device) displays a fixation optotype F for fixing the line of sight of the subject and a light stimulation optotype L for providing light stimulation to the pupil of the subject. The display contents of the liquid crystal display 1 are controlled by a computer 6. As an example, the liquid crystal display 1 has a 19-inch diagonal screen, SXGA resolution (1280X 1024 dots), and maximum luminance of 400cd/m²The contrast ratio was 450 to 1 (450: 1), the display color was about 16.77M, the viewing angle in the vertical and horizontal directions was 160 degrees, and the reaction speed was 12 ms. The distance between the liquid crystal display 1 and the peephole 10 is about 29cm, and therefore the field of view that can be measured in the vertical direction is ± 26 degrees and the field of view that can be measured in the horizontal direction is ± 21 degrees. With the liquid crystal display 1as a display device, the background brightness of the screen and the brightness of the light stimulus optotype can be adjusted separately. Therefore, by providing a required luminance difference to the background luminance and the luminance of the light stimulus optotype, thereby providing sufficient light stimulus to the pupil P of the subject, light reflection of the pupil is easily generated. Further, since it is not necessary for the perimeter to darken the background brightness for more than necessary, the time for the subject to adapt to the background darkness (i.e., the darkness adaptation time) is short, so that the time to check the field of view can be shortened. Of course, since the size, shape, and movement of the optotype can also be changed at will, the optimum optotype can be displayed according to the subject. Preferably, the background brightness is set at about 3.18 × 10^-1To 3.18cd/m²(i.e., 1 to 10asb (1asb ═ 1/pi cd/m)²) ) is used. Preferably, the luminance of the photostimulation optotype is set at about 286 to 382cd/m²(i.e., 900 to 1200 asb).

The infrared light emitting diodes 2 (infrared light emitting devices) are installed at a position obliquely upward and a position obliquely downward with respect to the eyes E of the subject S, respectively, so as not to obstruct the line of sight of the subject. The infrared light emitting diode 2 emits infrared light having a wavelength of about 850nm to the eye E of the subject.

The CCD camera 3 (image pickup device) has a 400000 pixel resolution and is sensitive to infrared light, and therefore, in a dark environment where the light of natural light is little, the CCD camera 3 can take an image of the eye E of the subject using infrared light of the infrared light emitting diode 2. Since the human retina cannot sense infrared light, the infrared light of the infrared light emitting diode 2 does not cause light reflection of the pupil.

The half mirror 4, a so-called hot mirror, is formed by coating the surface of a glass plate with a filter layer having characteristics of reflecting infrared light having a wavelength of about 850 ± 50nm and transmitting visible light having a wavelength of 450 to 650 nm. The half mirror 4 is disposed between the eye E of the examinee and the liquid crystal display 1, for example, in front of the eye E of the examinee so that the normal direction of the half mirror 4 is inclined by about 45 degrees with respect to the optical path. Since the light from the liquid crystal display 1 passes through the half mirror 4 and enters the eye E of the examinee, the examinee can see the screen of the liquid crystal display 1 through the half mirror 4. The light rays emitted by the infrared light emitting diode 2 and reflected by the eye E of the subject are all reflected by the one-way half mirror 4, and enter the CCD camera 3 disposed above the one-way half mirror 4.

The image processing apparatus 5 (pupil detection means) processes the image taken by the CCD camera 3, and measures the pupil diameter by extracting a pupil portion from the image of the eye E, and then outputs the measurement result of the pupil diameter to the computer 6.

The computer 6 is connected to the image processing apparatus 5 and the liquid crystal display 1, and has the following functions: the computer 6 controls the display content of the liquid crystal display 1, and displays a fixed optotype and a light stimulation optotype at a plurality of predetermined positions on the liquid crystal display 1 (optotype control means); when the light stimulus optotype is displayed under the condition that the subject looks at the fixed optotype, the computer 6 measures the visual field based on the pupil diameter change of the subject detected by the image processing apparatus 5 (visual field measuring device). These functions are realized by software (program). The computer 6 is also connected to an operation switch 7, and can receive an operation signal from the operation switch 7 according to the operation of the subject.

The inner surface of the housing 8 and all parts of the housing 8 except the viewing area of the liquid crystal display 1, the emitting surface of the infrared light emitting diode 2, the receiving surface of the CCD camera 3 and the half mirror 4 are coated with a black body coating having an emissivity of about 1.0. The light emitted by the liquid crystal display 1 is absorbed by the black body coating, thereby preventing the following: the light is reflected by other components and enters unnecessary parts of the examinee's eye, and thus accurate visual field measurement cannot be performed. Instead of applying a black body coating, an anti-reflection coating having a low reflectance may also be applied.

As shown in fig. 2 and 3, the liquid crystal display 1 is mounted on a display position adjustment mechanism 11 (display position adjustment means), and the display position adjustment mechanism 11 can adjust the position of the liquid crystal display 1 in the vertical direction and/or the horizontal direction and/or the front-rear direction with respect to the peephole 10. The display position adjustment mechanism 11 includes: an X-axis table 11A driven by a stepping motor 12A and movable in a horizontal direction (X-axis direction) with respect to the peephole 10; a Y-axis table 11B mounted on the X-axis table 11A, driven by a stepping motor 12B, and movable in the front-rear direction (Y-axis direction) with respect to the peephole 10; and a Z-axis table 11C mounted on the Y-axis table 11B, driven by a stepping motor 12C, and movable in a vertical direction (Z-axis direction) with respect to the peephole 10. The liquid crystal display 1 is mounted on the Z-stage 11C. By adjusting the positions of the X-axis table 11A and the Z-axis table 11C with the subject S placing the lower jaw thereof on the lower jaw support base 9, the center of the liquid crystal display 1 can be adjusted to the center of the right or left eye of the subject S, whereby the visual field can be measured with the liquid crystal display 1 having a small screen. Further, even if the subject S is nearsighted or farsighted, the liquid crystal display 1 can be moved to a position where the subject S can be seen clearly by moving the Y-axis table 11B in the front-rear direction. Therefore, the subject S can perform a visual field examination without glasses or contact lenses, so that the visual field can be measured more accurately.

As shown in fig. 4A and 4B, the CCD camera 3 is attached to the link plate 13, and the link plate 13 is disposed at an almost horizontal position on the half mirror 4 so that the CCD camera 3 can move in the front-rear direction and can rotate about the X-axis. By moving the CCD camera 3 in the front-rear direction and rotating about the X-axis by an image pickup device adjusting means (not shown) such as a servo motor, the image pickup position and the image pickup direction of the CCD camera 3 can be adjusted so that the center of the CCD camera 3 corresponds to the position of the pupil P of the subject. Further, by rotating the CCD camera 3 about the X axis, the reflection angle of the eye E in the half mirror 4 can be adjusted. Therefore, by adjusting the image pickup angle of the CCD camera 3 to an angle at which the CCD camera looks up the eyes from below, it is possible to pick up the image of the pupils so that the eyelashes do not overlap with the pupils P, whereby the eyelashes can be prevented from decreasing the detection accuracy of the pupil diameter. Preferably, the computer 6 includes an image pickup apparatus control function (image pickup apparatus control means) for controlling an image pickup apparatus adjusting means such as a servo motor and adjusting the image pickup position and the image pickup direction of the CCD camera 3 so that the pupil diameter of the subject reaches a peak (in other words, the pupil diameter of the subject reaches a maximum). Thus, the position and the image pickup direction of the CCD camera 3 can be automatically adjusted to the optimum position and the optimum image pickup direction.

The measurement principle of the perimeter of the present invention is explained below. Fig. 5 shows the screen of the liquid crystal display 1, with a fixed optotype F displayed in the center of the screen. The subject is instructed to gaze the fixation optotype F with one eye, and when the subject gazes the fixation optotype F with one eye, the computer 6 displays the light stimulation optotypes L one by one at a plurality of predetermined positions of the screen at random. In fig. 5, a symbol "●" represents one example of the currently displayed light stimulation optotype L, and a symbol "o" represents other examples of the display position of the light stimulation optotype L.

When the light stimulation optotype L is displayed, the CCD camera 3 takes an image of the eye E by using the infrared light of the infrared light emitting diode 2. Fig. 6A shows an example of a captured image.

As shown in fig. 6B, the image processing apparatus 5 extracts a pupil P from the captured image, and detects a pupil diameter D.

Incidentally, the size of the pupil is regulated by the sphincter pupillae and the dilated pupillary muscle, which is controlled by the parasympathetic nervous system, and the dilated pupillary muscle is controlled by the sympathetic nervous system. Thus, when light stimulation is provided to the eye E at any position in the normal visual field region, information is transmitted to the parasympathetic nervous system, and then the pupil sphincter muscle is reflexively contracted. Thereafter, when the light stimulus is removed, the pupil dilates. This neurotransmission is a brainstem reflex, and therefore, it is generally impossible for the subject to autonomously control, and it occurs discontinuously with light stimulation. This is called the light reflection of the pupil, the stronger the light stimulus, the greater the response of the light reflection of the pupil becomes. In other words, it can be said that the display position of the light stimulation optotype has high retinal sensitivity in a place where the response is large and low retinal sensitivity in a place where the response is small.

Fig. 7 shows an example of a change in pupil diameter due to light reflection by the pupil. When the computer 6 displays the light-stimulated optotype at an arbitrary position for 0.1 second, miosis (contraction of the pupil) occurs after a delay time dt (latency) of about 0.2 to 0.3 second. After a time ta elapses from the beginning of miosis, the pupil diameter reaches its maximum constriction point (minimum). After reaching a minimum, the pupil diameter gradually dilates (so-called dilation of the pupil). In fig. 7, curves C1 and C2 represent the change in pupil diameter when light stimulating objectives are provided to two different locations in the visual field area. Curve C2 has a small range of pupil diameter variation relative to light stimulation (i.e., D1 > D2) compared to curve C1. When the change in the pupil diameter is small, as in the curve C2, it is considered that there is some abnormality in the optic nerve at the position where the light-stimulated visual target is displayed, thereby decreasing the sensitivity of the visual field.

The computer 6 (visual field measuring device) calculates a maximum miosis amount, a miosis rate (pupil contraction rate, i.e., a ratio between the maximum miosis amount and an initial pupil size), a pupil contraction speed, and a pupil expansion speed based on a change in the pupil diameter detected by the image processing apparatus 5.

An example of the result of actually measuring the visual field of a glaucoma subject using the above principle is explained below by fig. 8 to 11B. In this measurement, a fixed optotype F is displayed in the center of the screen, the subject is instructed to gaze at the fixed optotype F with one eye, and as shown in fig. 8, when the subject gazes at the fixed optotype F, light stimulation optotypes L of white pulses are randomly displayed at a plurality of predetermined positions M0 to M20 on a straight line running in the left oblique direction in the visual field of the subject, and then the computer 6 calculates the miosis rate from the pupil diameter D measured by the image processing device 5. The background luminance of the liquid crystal display 1 is about 0.5cd/m²The brightness of the optical stimulation sighting target is about 300cd/m²The size of the light stimulation optotype is 2.0deg, and the display time of the light stimulation optotype is about 0.2 seconds.

Fig. 9A is a measurement result of the upper visual field of the right eye of the subject. That is, the relationship between the miosis ratio when the light stimulation optotype is displayed at the respective positions M0 to M10 of fig. 8 and the display position (irradiation angle) of the light stimulation optotype is graphically represented. The solid line indicates the measurement result, and the broken line indicates the miosis ratio of a normal person. Fig. 9A shows that the subject's miotic ratio is greater than or equal to that of a normal person for all illumination angles. Therefore, it can be judged that the upper visual field of the right eye of the subject is normal.

On the other hand, fig. 9B is a measurement result of the lower visual field of the right eye of the subject. That is, the relationship between the miosis ratio when the light stimulation optotype is displayed at the respective positions M11 to M20 of fig. 8 and the display position (irradiation angle) of the light stimulation optotype is graphically represented. As in fig. 9A, the solid line indicates the measurement result, and the broken line indicates the miosis ratio of the normal person. Fig. 9B shows that in the nasal region of the subject (i.e., positions M11 to M15) and a part of the ear region of the subject (i.e., positions M17 to M20), the miotic ratio of the subject is smaller than that of a normal person. That is, it can be considered that in these regions, the sensitivity of the subject's visual field has degraded.

Fig. 10 shows the results of simultaneous static perimeter (subjective perimeter) measurements on the same subject. In examination using a static perimeter, the subject is instructed to press an operation switch when he/she sees a light stimulation target, and if the subject presses the operation switch when the light stimulation target is displayed, the display position is determined to be a normal visual field region of the subject, and if the subject does not press the operation switch when the light stimulation target is displayed, the display position is determined to be an abnormal visual field region. The visual field of the subject is represented by a gray scale, in which a normal visual field region is represented by white and an abnormal visual field region is represented by black. Fig. 10 shows that, as in the measurement results of fig. 9A and 9B, the upper region of the subject is a normal visual field region, and the lower region of the subject is an abnormal visual field region.

In the perimeter of the present invention, it is also possible to perform the same inspection as the above-described inspection using the static perimeter by using the operation switch 7, and to improve the reliability of the measurement result by performing the subjective perimeter measurement in combination with the objective perimeter measurement.

Incidentally, fig. 11A shows the objective measurement result of the lower visual field of the subject's left eye using the perimeter of the present invention, and fig. 11B is the subjective measurement result of the visual field of the subject's left eye using a static perimeter. Referring to fig. 11A, in the region on the ear side of the subject (around M13), the miosis rate decreases, and therefore it can be considered that the visual field sensitivity of the subject has degraded. However, referring to fig. 11B, the lower region on the ear side of the subject is white, that is, the region is judged to be a normal visual field region. In other words, although the region is judged to be a normal visual field region in the subjective result, it is judged that the visual field sensitivity of the region has degraded in the objective result. This is believed to be before subjective symptoms appear in the subject, and objective examination can capture symptoms early. As described above, objective perimeter is expected to catch symptoms early and halt their development.

Although in the above measurement example, the computer 6 calculates the miosis rate from the change in the pupil diameter as an instruction to measure the visual field of the subject, the computer 6 (visual field measuring apparatus) may have a function of judging whether or not the position of the display light stimulus optotype is a normal visual field region of the subject in addition to the function of calculating the miosis rate. For example, the computer 6 compares the miosis rate with a predetermined threshold, and if the miosis rate is greater than the predetermined threshold, the computer determines a normal visual field region, and if the miosis rate is less than the predetermined threshold, the computer determines an abnormal visual field region. In this case, preferably, the threshold value varies with the age and/or sex of the subject. Alternatively, the visual field region of the subject may be divided into four regions (for example, four regions including a first quadrant (upper right quadrant) to a fourth quadrant (lower right quadrant)), and a divided region in which the visual field sensitivity degradation density is high may be determined as an abnormal visual field region.

The computer 6 (optotype control means) may have a function of changing the color of the light-stimulated optotype. In this case, since the sensitivity of the retina varies with the color wavelength, a specific retinal area can be checked by changing the color of the light stimulation optotype. That is, in general, retinal cells can be classified into rod cells responding to black and white and cone cells responding to color, and thus, by displaying a colored light-stimulated visual target, the response of various cone cells can be examined.

Although the light stimulation optotype is displayed only on the straight line running in the left oblique direction in the visual field of the subject in the above examination, the display position of the light stimulation optotype is not limited to the above example.

Incidentally, the miosis rate decreases with age, and therefore, for some subjects, even if pulsed light stimulation is provided, the light reflection of the pupil may be small. In this case, preferably, the pulsed light-stimulated optotypes are displayed continuously at least twice within the latency time. Fig. 12A shows the change in pupil diameter when 0.2 second pulsed light stimulus L1 is displayed (see curve C3), and fig. 12B shows the change in pupil diameter when 0.1 second pulsed light stimulus is displayed twice consecutively at intervals of 0.1 second (see L2 and L3) (see curve C4). When comparing fig. 12A and 12B, the total time of light stimulation in each graph is 0.2 seconds, equal to each other, but the change in pupil diameter in fig. 12B is larger than that in fig. 12A. As described above, by displaying the pulsed light stimulus at least twice in succession, it is expected that a large light reflection of the pupil is obtained.

Further, even in a steady state without light stimulation, the size of the pupil diameter drifts, so that there may be cases where: it is difficult to judge whether the change in pupil diameter is caused by light stimulation. In this case, preferably, the light stimulation optotype whose light intensity varies periodically is displayed on a liquid crystal display. Fig. 13 shows an example of the change in pupil diameter when the light pulse train L4 is displayed at the center of the visual field as a light stimulus icon whose light intensity periodically changes, in the light pulse train L4, pulses are displayed 5 times in succession at intervals of 2 seconds. In fig. 13, although it is shown that the pupil diameter drifts even before the light stimulation optotype is displayed, when the pulse sequence L4 having 5 pulses is displayed, the pupil diameter also changes 5 times in synchronization with the pulse sequence L4 (see curve C5). As described above, when the light intensity varies periodically, if the visual field of the subject is normal, the induced pupil diameter variation also has periodicity. Therefore, when a change in pupil diameter is observed with periodicity as in fig. 13, then such a change is likely due to light stimulation. Although fig. 13 shows an example of a light stimulus icon in which the light intensity periodically changes at the center of the visual field, the same holds true for a light stimulus icon in which the light intensity periodically changes at other regions of the visual field. Therefore, by displaying the light stimulus optotype in which the light intensity periodically changes at a plurality of predetermined positions on the liquid crystal display while measuring the change in the pupil diameter, the visual field of the subject can be measured.

By checking whether the number of changes of the light stimulus P corresponds to the number of changes of the pupil diameter (in other words, the number of repetitions of the local minimum and the local maximum), it is possible to judge the synchronism between the light intensity period of the light stimulus optotype and the change period of the pupil diameter. Alternatively, the synchronism can be judged by performing autocorrelation analysis on the data string of the pupil diameter and checking the periodicity thereof.

Further, it is preferable that the computer 6 (visual field measuring device) has a function of calculating the synchronism between the light intensity period of the light stimulation optotype and the change period of the pupil diameter by using, for example, autocorrelation analysis, and notifying the calculated synchronism to a measurer (i.e., a doctor or the like). In this case, the measurer can judge the reliability of the measurement result by checking the synchronism between the light intensity period of the light stimulation optotype and the change period of the pupil diameter.

In the case of a periodic variation of the pupil diameter, local minima and local maxima of the pupil diameter are easily obtained. Therefore, the computer 6 (visual field measuring device) preferably defines the difference between the local minimum value and the local maximum value of the pupil diameter, that is, the fluctuation range of the pupil diameter, as the variation width of the pupil diameter. Alternatively, the amplitude of the pupil diameter, that is, half of the fluctuation range, is defined as the variation width of the pupil diameter. As shown in fig. 13, when the differences between the plurality of local minimum values and the local maximum values can be obtained, the average thereof can be defined as the variation width of the pupil diameter at the display position of the light stimulation optotype. In this case, fluctuation (unevenness) of the pupil diameter can be alleviated.

Preferably, the computer 6 (visual field measuring device) calculates the ratio between the above-obtained variation width of the pupil diameter and the light intensity of the light stimulation optotype, and measures the visual field sensitivity of the subject based on this ratio. In the case where a very minute retina area is abnormal and its surrounding area is normal, if the range of emission of the light stimulus optotype to the retina crosses the abnormal area and the normal area, a pupillary reaction occurs. In this case, it is considered that the magnitude of the pupillary response varies with the ratio between the magnitude of the abnormal region and the magnitude of the normal region, and therefore, the sensitivity of the visual field can be calculated by measuring the magnitude of the pupillary response. The magnitude of the pupillary response depends on the intensity of the light stimulus, with the stronger the light stimulus, the greater the pupillary response. Therefore, the computer 6 can measure the visual field sensitivity of the subject by calculating the ratio between the variation amplitude of the pupil diameter and the light intensity of the light stimulus optotype (i.e., the size of the pupil response/the size of the light stimulus optotype). If this ratio is small, it means that the pupillary response to intense light is small, and thus it can be considered that the sensitivity of the retina has deteriorated.

In the case of a light stimulus optotype showing a periodical change in light intensity, the computer 6 (optotype control means) preferably has a function of changing the period of light intensity. Fig. 14 shows an example when the light pulse train L5 is displayed, in which one pulse is displayed at one-second intervals in the light pulse train L5. Comparing figure 14, which shows one pulse at one second intervals, with figure 13, which shows one pulse at 2 second intervals, the amplitude of the pupil diameter of figure 14 is smaller than that of figure 13, and the periodic nature of figure 14 is not evident. The earlier the next light stimulus is displayed before the pupil is fully dilated, the shorter the period becomes and the smaller the change in the magnitude of the pupillary response becomes. Therefore, in order to improve the readability of the change width of the pupil diameter, it is preferable that the period is not too short. On the other hand, if the period is long, the examination time is also long, and therefore the burden on the subject is increased. Therefore, it is preferable that the computer 6 has a function of changing the light intensity period, and when the periodicity of the pupil diameter change is significant, the computer 6 shortens the light intensity period to shorten the examination time, and when the periodicity of the pupil diameter change is not significant, the computer 6 lengthens the period in which the light stimulus appears to increase the visibility of the waveform.

Although the light intensity varies at a constant period in fig. 13 and 14, the light intensity does not have to vary at a strictly constant period. By measuring the change in pupil diameter D in real time, changing the light intensity period according to the pupil response period, and displaying the light stimulus optotype at the appropriate time, the change in pupil diameter can be magnified.

Although, in fig. 13, the light pulse train L4 is shown as the light stimulation optotype whose light intensity varies periodically, an optotype L6 whose light intensity varies in a sine wave manner may be used as an alternative to the light pulse train, as shown in fig. 15. Referring to fig. 15, when the optotype L6 in which the light intensity varies in a sine wave manner is displayed, although the variation of the pupil diameter (see the curve C7) is somewhat deviated from the sine wave, the variation of the pupil diameter still corresponds to the light stimulus. When the change in pupil diameter is observed to have a periodicity as in fig. 15, it is considered that the change is likely due to light stimulation. As described above, when the optotype L6, in which the light intensity changes in a sine wave manner, is used as a substitute for the light pulse train, it is easy to judge whether or not the change in the pupil diameter is caused by the light stimulus.

In fig. 15, the offset component (DC value) of the pupil diameter is in a downward trend. When the change in the pupil diameter has such a tendency, if a single light stimulus is used, it is not obvious whether the change in the pupil diameter is caused by such a tendency or by the single light stimulus. However, since the pupil diameter periodically changes in fig. 15, it is easy to judge that this change is due to light stimulation, and the corresponding retinal region is normal.

Further, it is preferable that the computer 6 (optotype control means) has a function of changing the size of the light stimulation optotype. Generally, the larger the light-stimulating optotype, the larger the light reflection amplitude of the pupil, and the improved readability of the waveform. However, if the optotype is large, the stimulation area to the retina is also large, and accurate measurement is impossible. On the other hand, if the angle of view of the optotype is small, the readability of the waveform is reduced, but accurate measurement can be performed, and early diagnosis of diseases such as glaucoma is expected. That is, there is a trade-off between the readability of the waveform and the accurate measurement. Therefore, it is preferable that the computer 6 has a function of changing the size of the optical stimulus optotype, and when it is desired to accurately measure, the computer 6 makes the optotype smaller in the observation direction, and when it is desired to improve the readability of the data, the computer 6 makes the optotype larger. In order to improve the readability of the waveform, when the optotype is small, it is preferable to increase the number of repetitions of the light-stimulated optotype or decrease the background luminance so that the change of the pupil becomes large.

It should be noted that: as described above, since the perimeter of the present embodiment employs the liquid crystal display 1as the display device, it is easy to change the intensity, the period, and the size of the light stimulation optotype as described above.

Although the present embodiment employs the liquid crystal display 1as the display device, other display devices such as CRT, PDP, ELD, FED, and the like may be used as the substitute for the liquid crystal display 1.

In addition, a head mounted perimeter can be constructed with a small liquid crystal display in a goggle-shaped housing.

As described above, the various embodiments of the present invention may be broadly constructed without departing from the spirit and scope thereof, and it should be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.

Claims

1. A perimeter, comprising:

a display device;

an optotype control device that displays, at a plurality of predetermined positions on the display device, a fixed optotype for fixing a line of sight of a subject and a light stimulation optotype for providing light stimulation to a pupil of the subject;

an infrared light emitting device for emitting infrared light to the eye of the subject;

an imaging device that takes an image of the eye of the subject using the infrared light emitted by the infrared light emitting device;

a housing in which the display device, the infrared light-emitting device, and the image pickup device are housed, the housing having a peephole through which the subject views the fixed optotype and the light stimulation optotype displayed on the display device from outside;

a pupil detection device that detects a pupil diameter of the subject based on the image captured by the imaging device;

a visual field measuring device that measures a visual field of the subject based on a change in pupil diameter of the subject detected by the pupil detecting device when the optotype controlling device displays the light stimulus optotype under a condition that the subject looks at the fixed optotype;

wherein,

the display device comprises a display device capable of adjusting the background brightness of a screen and the brightness of the light stimulation sighting target respectively.

2. The perimeter of claim 1, further comprising:

a display position adjustment device capable of adjusting a position of the display device in a vertical direction and/or a horizontal direction and/or a front-rear direction with respect to the peephole.

3. The perimeter of claim 1, further comprising:

and the camera equipment adjusting device can adjust the camera position and the camera direction of the camera equipment.

4. The perimeter of claim 3, further comprising:

and the image pickup equipment control device is used for adjusting the image pickup position and the image pickup direction of the image pickup device through the image pickup equipment adjusting device based on the detection result of the pupil detection device, so that the pupil diameter of the examinee reaches the peak value.

5. The perimeter of claim 1, further comprising:

an operation switch that outputs an operation signal to the visual field measuring device in response to an operation of the subject,

the visual field measuring device measures a visual field based on a change in pupil diameter of the subject and an operation signal input from the operation switch.

6. The perimeter of claim 1,

the emissivity of the inner surface of the housing is 1.

7. The perimeter of claim 1,

the sighting target control device continuously displays the pulse-shaped optical stimulation sighting target on the display device at least twice.

8. The perimeter of claim 1,

the visual target control device displays the light stimulation visual target with periodically changed light intensity on the display device.

9. The perimeter of claim 8,

the optical stimulation sighting mark is an optical pulse sequence.

10. The perimeter of claim 8,

the light intensity of the light stimulation optotype varies in a sine wave manner.

11. The perimeter of claim 8,

the sighting mark control device has the function of changing the light intensity period of the light stimulation sighting mark.

12. The perimeter of claim 8,

the optotype control device has a function of changing the size of the light stimulation optotype.

13. The perimeter of claim 8,

the visual field measuring device has a function of calculating a change width of the pupil diameter from a fluctuation range of the pupil diameter or an amplitude of the pupil diameter.

14. The perimeter of claim 13, wherein,

the visual field measuring device has a function of calculating a ratio between a variation width of the pupil diameter and the light intensity of the light stimulation optotype, and measuring the visual field sensitivity of the subject based on the ratio.

15. The perimeter of claim 8,

the visual field measuring device has a function of calculating synchronism between a light intensity cycle of the light stimulation optotype and a change cycle of the pupil diameter of the subject.

16. The perimeter of claim 1,

the visual field measuring device has a function of determining whether or not the position of the light stimulation optotype is displayed in a normal visual field region of the subject based on a change in pupil diameter of the subject.

17. The perimeter of claim 1,

the optotype control device has a function of changing the color of the light stimulation optotype.