JPH04272740A - Moving body detection contrast threshold inspecting device - Google Patents

Abstract

PURPOSE:To always show the target of an exact constant value to a person to be examined, and to detect the abnormality in an early stage of a visual field fault by adjusting the light quantity of a light source of at least one of an illumination optical system and a stripe target projection optical system, based on an output from a photodetector. CONSTITUTION:When a power source switch of the device is turned on, halogen lamps 1, 14 are turned on, and also, by a pulse motor 5, a disk 4 is set to an initial position. Subsequently, by moving a stripe target plate 7 by a stripe target driving part 8, a bright part and a dark part of a stripe target are projected successively to a light intake window, and luminance of each projection light is measured. Based on the measured luminance of the projection light, a contrast is calculated and compared with a prescribed regulation value, and when an error of both of them is within a prescribed range, the calibration is finished. When the error is outside of the prescribed range, whether it is larger or smaller than the regulation value is discriminated and an impressed voltage of the halogen lamp 1 is raised or lowered by a prescribed step. Such an operation is repeated until the error to the regulation value becomes within the prescribed range.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a testing device for testing the visual function of the eye.

0002

BACKGROUND OF THE INVENTION Visual field testing has been conventionally performed as a method for testing eye diseases that cause visual field impairment, such as glaucoma. This visual field test involves positioning the subject's eye in the vicinity of the spherical center of a hemispherical projection screen, and measuring the visual field while changing the presentation location of the optotype projected onto the projection screen. This is what we do. Although this method is also useful as a visual field test, it has been reported that in the case of glaucoma, by the time this test shows that visual field damage has occurred, half of the optic nerve cells have already been lost; It has been desired to detect subjective abnormalities in advance and use them for screening. Furthermore, it has been desired to detect abnormalities at an early stage in diabetic retinopathy and the like, and to utilize this method in screening. Based on such a request, the present applicant has filed the patent application No. 2-11
In No. 4450, a moving object detection threshold testing device was proposed.

0003

[Problem to be Solved by the Invention] In this test, the subject must be presented with an optotype with a contrast value that is accurately controlled, but the above-mentioned device is difficult to overcome the effects of the brightness of the test environment and the deterioration of the light source. Unavoidably, there is a problem in that it is difficult to always present visual targets with accurate contrast values to the subject.

[0004] The present invention was devised based on the above-mentioned requirements, and it provides visual targets with accurate contrast values to the subject at all times, thereby preventing visual field impairment caused by diseases such as glaucoma and diabetic retinopathy. The technical challenge is to provide a device that can detect abnormalities at an early stage.

[Means for Solving the Problems] In order to solve the above problems, a moving object detection contrast threshold testing device of the present invention has the following configuration. That is, (1)
A stripe target projection optical system that projects a stripe target onto a projection screen, a contrast switching means that switches the contrast of the stripe target, a drive unit that vibrates the stripe target, and a drive unit that vibrates the stripe target; an illumination optical system that illuminates uniformly; a photodetector that detects the amount of light disposed near the projection screen; and at least one of the illumination optical system and stripe target projection optical system based on the output from the photodetector. It is characterized by comprising an adjusting means for adjusting the light amount of at least one light source.

(2) The contrast switching means in (1) is a switchable filter disposed in the stripe target projection optical system or a switching means for adjusting the light intensity of the projection light source for the stripe target. It is a feature.

(3) The photodetector of (1) is arranged approximately at the center of the striped target projected on the projection screen and is used as a fixation target.

(4) The photodetector for detecting the amount of light in (1) is equipped with a light receiving window smaller than the width of each of the bright and dark areas of the projected striped target, and moves the striped target to detect the striped target. It is characterized by detecting the amount of light when the bright and dark portions of the mark cover the light receiving window, and adjusting the amount of light from the light source based on the detected amount of light.

[0009]

[Embodiment] Prior to a detailed explanation of the embodiment, the inspection principle on which the present inspection apparatus is based will be explained. Examining the visual function of the eye reveals that there are vertical connections made up of photoreceptor cells, bipolar cells, and ganglion cells, and horizontal connections made up of horizontal cells and amacrine cells. The vertical connections convert the light that reaches the photoreceptor cells into electrical signals, which transmit image information to the brain via the optic nerve. On the other hand, horizontal connections are composed of horizontal cells located between photoreceptor cells and bipolar cells, and amacrine cells located between bipolar cells and ganglion cells, and are responsible for contrast enhancement, motion detection, stereoscopic perception, etc. . This horizontal connection allows humans to accurately see objects under a wide range of illumination ranging from 1 to 1011, and is said to be able to detect even the slightest stain or dirt on a white wall.

[0010] Incidentally, in diabetic retinopathy, it is known that rhythmic wavelets related to lateral function become abnormal at an extremely early stage, and disturbances in lateral function occur in the early stages of visual field impairment. Focusing on the fact that this is estimated to be the case, this device attempts to detect subjective abnormalities in visual function that can be associated with abnormalities in lateral function. in particular,
A striped pattern with an appropriate spacing (the optimal width for one horizontal cell to connect, that is, approximately 200 μm on the retina) is imaged on the retina, and the striped pattern is swayed to provide stimulation. The amplitude of this vibration should be at least 1/2 of the stripe width, and the frequency should be within a range that does not affect the static detection ability (
It is easy to detect if the threshold value (to be described later) is easily set when the stopping distance is 300 mm and the frequency is set to about 4 Hz. The test examines how low the contrast the subject can recognize the movement (fluctuation) of the striped pattern projected at the center of the adaptation field. If horizontal cells and amacrine cells are functioning normally,
It can be recognized even when the contrast is low, below a certain threshold set as the boundary between a normal person and an abnormal person. However, if these do not function properly, low-contrast striped patterns cannot be recognized.

[0011] Details of an embodiment of the present invention based on the above measurement principle will be explained with reference to the drawings. Configuration FIG. 1 is an optical system layout diagram showing the configuration of the optical system of the inspection apparatus of this embodiment. Reference numeral 1 denotes a halogen lamp which is a light source of the optotype projection optical system. Light from the halogen lamp 1 enters a disk 4 via a condenser lens 2 and an aperture 3. A wedge-type filter that changes the transmittance steplessly on the projection optical path is arranged on the disk-shaped disk 4, and the disk 4 is rotated by a pulse motor 5 to change the transmittance. In this embodiment, the transmittance changes stepwise, and the contrast of the striped target is designed to have a resolution of 200 steps in the range of 0.1% to 10%.

The light transmitted through the disk 4 illuminates the striped optotype plate 7 almost uniformly through the projection lens 6. On the striped optotype plate 7, a striped pattern is drawn in which the transmittance in bright areas is 80% or more and the transmittance in dark areas is 0%. The stripe optotype plate 7 is constructed so that the stripe optotype (see FIG. 2) projected onto the screen 13 has a visual angle of 5 degrees and a stripe pitch of 0.5 degrees. The striped optotype plate 7 is vibrated by the striped optotype drive unit 8 in a direction perpendicular to the stripe direction. The frequency of this vibration is 4Hz and the amplitude is 0.2
It is 5 degrees. The striped target drive unit 8 in this embodiment employs the following simple mechanism in consideration of the fact that the amplitude of vibration is sufficiently small. That is, by vibrating a vibration shaft having one end fixed to the striped optotype plate 7 and the other end fixed to the shaft of a pulse motor, the striped optotype plate 7 is vibrated by the forward and reverse rotation of the pulse motor.
vibrate.

The projection lens 10 includes an aperture 9 and a mirror 11.
, 12, the image of the striped optotype plate 7 is formed at the center of the screen 13. The shape of the screen 13 is hemispherical,
The screen size is 20 degrees, and the gaze distance from the eye to be examined is 3
It is set to 00mm. The front of the screen 13 is covered to block light from the outer periphery, and the subject looks at the striped target projected onto the screen 13 with his or her left or right eye through an opening in the center. ing.

Reference numeral 14 denotes halogen lamps, two of which are placed on the left and right sides of the opening, and illuminate the screen 13 uniformly. The background brightness of this screen is 500 cd/m2, and the background brightness corresponds to the brightness of the dark part of the striped optotype. It is designed to.

15 is a light receiving element. The light receiving element 15 detects changes in brightness due to the influence of ambient light, deterioration of the light source, etc.
This is to accurately maintain the contrast of the striped optotype. The light intake window of the light receiving element 15 is 1/2 or less of the stripe pitch. Although it is not essential that it be 1/2 or less, it is desirable that it be 1/2 or less of the fringe pitch to simplify processing.

Next, the main parts of the electrical system for driving this apparatus will be explained by dividing them into a calibration mechanism for accurately maintaining contrast and a mechanism for testing the eye to be examined. FIG. 3 is a block diagram of the electrical system of the calibration mechanism. The striped optotype drive unit 8 moves the striped optotype plate 7 to sequentially project the bright and dark parts of the striped optotype, and the brightness (light amount) of each is measured. The light incident on the light receiving element 15 is converted into an electrical signal and amplified by the amplifier 16. The amplified signal is converted into a digital signal by an A/D converter 17 and then input to a microcomputer 18. Microcomputer (also controls the operation of the entire device) 1
8, the contrast is calculated from the brightness of the bright and dark areas. Contrast is expressed by the following formula. Here, A is the brightness of the bright part of the striped pattern, and B is the brightness of the dark part of the striped pattern (brightness of the adaptation field).

The microcomputer 18 compares the contrast thus obtained with a specified value, and instructs the PWM pulse generator 19 to brighten the halogen lamp 1 when the contrast is small, and to darken it when the contrast is large. Generate a pulse signal. Lamp driver 2 based on pulse signal
0 controls the voltage applied to the halogen lamp 1.

FIG. 4 is a block diagram of an electrical system that controls the operation for testing the eye to be examined (the illumination circuit for the halogen lamp 1 is shown in FIG. 3 and will therefore be omitted). The microcomputer 18 controls the on/off of the halogen lamp 14 via a lamp driver 21, the drive of the pulse motor 5 via a motor driver 22, and the drive of the striped target drive unit 8 via a motor driver 23, respectively. . Signals from patient response switch 24 are input to microcomputer 18 for processing. 25 is a printer driver that outputs the test results, and 26 is a printer. 27 is the control
It specifies the contrast and presentation speed.

Operation The operation of the apparatus of the embodiment configured as described above will be explained based on a flowchart. FIG. 5 is a flowchart of contrast calibration. When the power switch (not shown) of the apparatus is turned on, the halogen lamps 1 and 14 are turned on, and the pulse motor 5 sets the disk 4 to the initial position. Striped target drive unit 8
The striped optotype plate 7 is moved, the bright and dark parts of the striped optotype are sequentially projected onto the light intake window, and the brightness of each projected light is measured (step 1-1). Contrast is calculated based on the measured brightness of the projection light (step 1-2), and the calculated value is compared with a predetermined standard value (step 1-3).
. If both errors are within a predetermined range, the calibration ends. If the error is outside the specified range, determine whether it is larger or smaller than the specified value (step 1-4), and turn on the halogen lamp 1.
The applied voltage is increased or decreased in predetermined steps (steps 1-5, 1-6). Such operations are repeated until the error from the specified value falls within a predetermined range.

FIG. 6 is a flowchart of the inspection. When the examination starts, the eye to be examined is first made to look at the screen for 1 to 2 minutes (step 2-1). This is to make the subject's eye photopic. Next, drive the disk 4 and set the contrast of the striped target to 10% (step 2-2).
, set the test loop count to 0 (step 2
-3). Here, one loop represents one test using one contrast.

When this step is completed, the examiner presses the start switch on the controller 27, and measurements are automatically performed thereafter. Present a stationary stripe optotype (step 2-
4) The subject is asked to respond whether or not the striped optotype is visible to the subject's eye (step 2-5). If the response is correct, proceed to step 2-6; if the response is incorrect, step 2-7
Proceed to.

In step 2-6, the controller 27 is operated to vibrate the striped optotype board 7 and the subject responds (step 2-8). When the vibrating striped optotype is recognized, Proceed to step 2-9. If this response is incorrect, the process proceeds to step 2-7.

In step 2-9, the contrast of the striped target is lowered by one step. Determine whether the contrast decreased by one level is the lowest contrast (step 2-10), and if the contrast is the lowest, step 2
Proceed to -11.

If the contrast is not the lowest, the test routine
Determine whether the count of taps is 10 or more (
Step 2-12). If the desired detection result is obtained after 10 or more inspection loops, the process proceeds to step 2-11.

If the number of inspection loops is less than 10, it is determined whether the contrast variation width is 0.1% or less (step 2-13). If it is 0.1% or less, it is determined that the test result is correct and the process proceeds to step 2-11. 0.
If it is less than 1%, add 1 to the inspection loop count and proceed to A (step 2-14).

On the other hand, in step 2-7, the contrast is increased by 1/2 step and the process proceeds to 2-15, where it is determined whether the contrast is at the maximum value, and if it is not the maximum contrast, the process proceeds to step 2-12.

In step 2-11, the test results are printed out. It has been clinically confirmed that test results are considered normal if the contrast is 1% or less, and abnormal if it is higher than that.

[0028] Although the above-described measurement is performed in auto mode, it is also possible to adopt a method in which the contrast setting and the like are set by the examiner. Furthermore, accuracy can be increased by repeating this test several times by changing the direction of the stripes and calculating the average of the measured values.

In the embodiments described above, the contrast is changed by changing the disk 4 disposed in the stripe optotype projection optical system, but it can also be done by adjusting the light intensity of the projection light source itself. can. Also, instead of calibrating the contrast by adjusting the light intensity of halogen lamp 1,
The light amount of the disk 4 may be adjusted, or the control data of the disk 4 may be converted. As described above, this embodiment can be modified in various ways, and these modifications are also included in the present invention within the scope of keeping the same technical idea.

[0030]

Effects of the Invention According to the moving object detection contrast threshold testing device of the present invention, it is possible to always present a visual target with an accurate contrast value to a subject, thereby preventing visual field impairment caused by diseases such as glaucoma and diabetic retinopathy. Abnormalities can be detected early.

[Brief explanation of the drawing]

FIG. 1 is an optical system layout diagram showing the configuration of an optical system of an inspection apparatus according to the present embodiment.

FIG. 2 is an explanatory diagram of a striped optotype.

FIG. 3 is a block diagram of the electrical system of the calibration mechanism.

FIG. 4 is a block diagram of an electrical system that controls operations for testing an eye to be examined.

FIG. 5 is a flowchart of contrast calibration.

FIG. 6 is an inspection flowchart.

[Explanation of symbols]

1,14 Halogen lamp 2 Condenser lens 3,9 Aperture 4 Disc 5 Pulse motor 6,10 Projection lens 7　Striped optotype board 8 Striped target drive unit 11,12 Mirror 13 Screen 15 Photo receiving element

Claims (4)

[Claims] 1. A stripe target projection optical system for projecting a stripe target onto a projection screen, a contrast switching means for switching the contrast of the stripe target, a drive unit that vibrates the stripe target, and a projection system comprising: an illumination optical system that illuminates the screen almost uniformly; a photodetector that detects the amount of light disposed near the projection screen; 1. A moving object detection contrast threshold testing device, comprising: adjusting means for adjusting the light intensity of at least one light source of a projection optical system. 2. The contrast switching means of claim 1 is characterized in that it is a switchable filter disposed in the stripe optotype projection optical system or a switching means for adjusting the light intensity of the projection light source of the stripe optotype. A moving object detection contrast threshold testing device. 3. A moving object detection contrast threshold testing device according to claim 1, wherein the photodetector is arranged approximately at the center of a striped target projected on a projection screen and used as a fixation target. 4. The photodetector for detecting the amount of light according to claim 1 is provided with a light-receiving window smaller than the respective widths of the bright and dark parts of the projected striped optotype, and moves the striped optotype to detect the striped optotype. 1. A moving object detection contrast threshold testing device that detects the amount of light when a bright portion and a dark portion of the object cover a light receiving window, and adjusts the amount of light of a light source based on the detected amount of light.