JPH0414971B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for searching for a scotoma in the eye of a subject.

BACKGROUND OF THE INVENTION In visual field examination, differences in light sensitivity of different parts of the retina are examined. In this case, two different methods are known, one of which is dynamic perimetry, in which the examination is performed with moving test marks, and the other is static perimetry, In this static perimetry, differences in light sensitivity at fixed locations are precisely measured starting from dark luminance. Currently, multiple computer-supported systems are used, in which systems operate according to the so-called raster perimetry method. In this case, the test point raster is automatically scanned according to a program, in this way matched test point brightness or accurate threshold measurements are measured, and these measurement results are then stored and used in the examination. printed at the end of. Locations where nothing is perceived or where the light sensitivity difference is reduced are identified separately. The outcome of the examination is better the earlier such defects are detected.

For visual field examination, spherical perimetry is often used, in which the examination point is projected onto a sphere via an adjustable projection system or a diode or glass fiber light transmission. The body is attached to a sphere. All these known systems are expensive and mechanically very sensitive, since the demands on accuracy are very high.

A visual field examination method is known from US Pat. No. 4,634,243, in which a noise pattern image is shown to the patient, in which noise pattern images are geometrically isomorphic and restricted. It contains a regular arrangement of pixels in the form of a pattern. This pattern, which is small compared to the total area of the pixels, has regularly spaced and identical density of points, which differ both in arrangement and density from the points in the noise image. This geometrically arranged dot pattern is shifted across the entire image to examine scotomas or similar visual defects. In this way, scanning of the subject's central visual field is performed up to 30°. This method has also been found to be inadequate, as it is expensive and requires scanning the entire field of view during a lengthy examination.

The problem with all of these visual field examinations is that the subject himself or herself cannot confirm whether a visual field defect is present. Therefore, the entire retina must be examined in each examination.
The examination can be made much easier and faster if it is known at the beginning of the examination where such visual field defects are to be expected.

Problem to be Solved by the Invention An object of the present invention is to provide a device for searching for a scotoma in the eye of a subject, which allows the subject to point out such a visual field disorder in a very short time. It is to be.

Means for Solving the Problem This problem is solved by the features described in the characterizing part of claim 1.

EFFECTS OF THE INVENTION According to the invention, the eye of the subject is therefore provided with an image consisting of a number of points closely adjacent to each other on the screen and continuously alternating in brightness, this image being It additionally has a fixation point for
The alternation of brightness of individual pixels may be irregular or periodic. A simple device for performing perimetry examinations is a high-resolution video monitor, which contains a large amount of noise with very small particles, similar to the noise area that appears when a disturbance occurs in a television. It has a regularly flickering surface. The subject's eyes are located at a predetermined distance from the video screen, with the eyes fixed at a predetermined fixation point on the image screen. The subject can immediately see where the scotoma is present by looking at the noise area.

The pathological scotoma described above is evident when the patient sees, instead of a uniform surface, a bright and dark surface that flickers at a high frequency due to small particles, similar to the noisy areas that appear on a television monitor that is switched on and no program is received. You can make it so that you can see it. The patient's gaze
When fixed to a clearly visible point in the center of the television screen or programmed into it, the scotoma appears as a surface that is less or less flickering and whose brightness differs significantly from its surroundings. . The observer can trace the border of the scotoma on the television screen with a finger. This marking of one's darkening is often done voluntarily, because
This is because the limited "cloud" within the noise area makes a strong impression on the patient. All the above-mentioned absolute scotomas caused by damage to the retina or optic nerve or optic chiasm or optic tract can be noted by the patient in the same way as damage due to glaucoma, with temporary However, it is not yet known whether scotomas are perceived as brighter or darker clouds. However, in any case, a scotoma is identified by the fact that within the region of the scotoma, the flickering of the noise area is perceived to be absent or less compared to the surrounding area.

A prerequisite for the patient's reproducible perception of the scotoma and for rapid perimetry control and registration of the perceived visual field defect is a standardized, computer-generated noise whose only parameters can be varied. It is a video monitor capable of displaying both an area and a contourless surface with inspection points that are freely movable and can be selected as either bright or dark points. Furthermore, it is advantageous to insert a visual field diagram with a power display on the video monitor in order to ascertain the location and extent of the obstruction.

It is possible in a very simple way to combine the perception of a scotoma in a noise area with a measured perimetry examination as a test area on the screen of the same monitor. In doing so, perceiving the scotoma within the noisy area is the first orienting test that quickly informs the ophthalmologist whether and where a defect exists within the 30° visual field. , that is, it plays the role of a screening method. A conventional type of manual dynamic perimetry or automatic raster perimetry can then be performed within the scotoma region. The advantage of such a two-pronged method is that the perimetry only needs to be carried out within the defective area, thus resulting in significant time savings compared to conventional methods.

The simultaneous use of high-resolution video monitors for both noise area and regular perimetry allows for accurate comparison of the obtained examination results. Contrast and brightness and color can be varied in similar ways in both examination methods. In this case, both dynamic and static perimetry can be carried out manually, with free movement, or automatically. In this case, the form of the planar perimetry method can be perfectly matched to the shape and size of the visual field defects previously found by noise area perimetry. In this way, the advantages of rapid scotoma detection can be combined with the accuracy of a situation-adapted planar perimetry method.

Depending on the size of the video monitor, the viewing area to be examined is obtained. This viewing area is 60° on a typical video monitor.

However, this viewing area can be enlarged by shifting the fixation point.

It has been found to be very advantageous to project the noise area into the perimetry sphere, since in this way the advantages of the two-sided perimetry method can be implemented in the form of hemispheric perimetry. It is from.

In the device according to the invention, it has proven particularly advantageous if the brightness compensation of the image or image screen can be carried out at predetermined measurement points. This compensation can be performed, for example, by a photodiode,
The current flowing through the photodiode is then used as a measure of the brightness of the image screen. This compensation can be done continuously or at regular intervals during the visit. Therefore, accurate brightness levels can be adjusted and tested to obtain reproducible examination results. With the present invention, it is also possible to perform brightness compensation in many pixels.

With the device of the present invention, it is also possible to display a noise pattern only in visual field areas that are already recognized as visually impaired by the subject. If the remaining images do not show noise and the subject declares that all images do not display noise, no visual field defects are proven. In order to ensure that the noise image appears only on predetermined surfaces, the device is equipped with a light pen or a mouse or a touch screen.

In the present invention, the fixation point is adjusted by shifting the image in order to align the fixation point with the position of the subject's eyes. This shift can be carried out by means of a calculation program, in which case the subject's eyes are provided with, for example, a coordinate system. The advantage offered by this method of adjustment is that it does not require the use of previously known and expensive devices for fixing and adjusting the subject's head. Furthermore, adjustment of the fixation point can be accomplished much more quickly and easily.

With the present invention, it is possible to vary the diameter of the pixels so that a subject with visual impairment can recognize the individual pixels. Furthermore, the present invention allows the pixel colors to be varied or varied in order to prevent the subject's eyes from adapting to the noise area. Furthermore, it is possible to vary the intensity alternation frequency of the pixels to eliminate patient habituation. When changing the color of a pixel, it is also possible to simultaneously test the subject's visual perception of color.

In the apparatus of the present invention, it is possible to inspect the position of a dark spot by switching the brightness of each pixel between positive and negative.

In the present invention, for example, sequences of numbers are inserted into images controlled by a computer, and the subject points out which one or more digits in these sequences he can see. This allows the fixation point to be determined, allowing the patient to easily fixate his or her eyes. This fixation control can be achieved by aligning the fixation point or region with a blind area where the subject cannot see anything. The size of this fixation point or fixation region, ie the fault image generated by the computer, is in this case slightly smaller than the blind surface itself. The subject can therefore immediately detect a shift by slightly changing the fixation of the eyes.

Another advantage of the present invention is to add gray values to an image.
For example, on a regular television screen,
The point is that it can be displayed in fine steps, which are 256 gray value steps.

Therefore, it is possible to perform threshold measurement in a very simple manner.

In a particularly advantageous embodiment of the invention, the examining person, for example the doctor, is provided with a second screen, so that the examining person is always aware of the location and size of the respective defect area.

It has been found to be particularly advantageous to use the device of the invention to artificially increase the intraocular pressure of a subject for early detection of glaucoma. This can be done, for example, by means of a suction pump or drug treatment. In this way, visual disturbances that may occur due to natural changes in intraocular pressure can be predictively diagnosed.

Another advantage arises from being able to easily recognize one's own visual impairment within a noisy area.
That is, interested patients can control their scotoma from their home television screen. To do this, it must be noted that the patient must always maintain the same distance from the screen (approximately 30 cm), cover one eye and stabilize the fixation by the fixation point. In this way, if the absolute scotoma enlarges or a new scotoma develops, the observant patient will be able to detect this on their home television. EXAMPLES Next, the present invention will be explained based on examples using figures.

In FIG. 1 a side view of a video monitor 1 is shown. A collar support member 3 is used to determine the distance from the video monitor 1 to the subject's eyes 2 precisely and in a predetermined measuring method, measurably but changeably. The distance to the collar support member 3 is determined such that the field of view to be examined has a diameter of 60°.

In FIG. 2, which shows a front view of the screen 4, a fixation point 5 is shown, which is normally located at the center of the screen 4. However, fixation point 5
can be shifted laterally and in height, so that the viewing area can be shifted towards the edges and thus enlarged. It is not necessary at all for the fixation point 5 to shift if the dimensions of the video monitor 1 are so large that the video monitor 1 can display the entire field of view of the subject.

In practice, we have found that scotomas are most clearly visible when provided with a high flicker frequency, high contrast, and a noisy area with small particles. For this reason, many medical examinations use bright elements with a frequency of 50 Hz and a brightness of 60 cd/m ² m. It is performed by a dark element with a brightness of 8 cd/ ^m2 . The ratio of dark elements to bright elements is preferably 50% or 70% for dark elements. These elements are
It is a small square and measures 15 angles.

In the apparatus shown in Figure 1, the patient's head is approximately 30 cm from the monitor. The test area of the monitor measures, for example, 25 x 38 cm, so the viewing area is approximately 35° horizontally and 24° vertically. With the device of the invention it is possible to insert polar coordinates with a circular shape with a viewing angle interval of 5° into the monitor. The present invention not only shows noise areas and polar coordinates in the test area, but also
It is also possible to represent a uniform area for conventional perimetry. This area can be provided with various brightness levels between 60 and 0.8 cd/m ² .

Next, the diagnosis method of the present invention will be explained based on FIGS. 3a, 3b, and 3c. The examination begins by displaying the noise area on the monitor (Figure 3a). After the subject's eyes have been fixed on the fixation point shown in the center of the screen, the patient can very quickly indicate the scotoma area to the doctor. Once the scotoma area is indicated, the doctor will, as shown in Figure 3a,
For example, a scotoma region can be inserted into a noise area using a mouse. Polar coordinates are then displayed on the screen, into which a scotoma appears inserted, as shown in FIG. 3b. Then, by static or dynamic perimetry,
This area can be further examined with a uniform background. In dynamic perimetry, the doctor can move the test point freely on the monitor, for example with a mouse (FIG. 3c), and display visual field defects by pressing a key. This method is illustrated in the lower half of the screen in Figure 3c. The perimetry is performed automatically by the method of raster perimetry, in which the inspection points are randomly distributed in a previously selected area, as shown in the upper half of Figure 3c. provided. The subject counts the pixels seen at that time by pressing a button.

The method of the invention provides an excellent screening method by which only the pathological area within the visual field can then be examined on the same monitor by means of quantitatively measured perimetry. Consultation time is thus significantly reduced compared to all previous methods.

Another advantage is that the method is simple and easy to implement. The doctor and patient sit next to each other and look at the monitor screen together.
The noise area, the polar coordinates, and the perimetry area can appear on this screen sequentially or in any order. With this method, visual field examination is no longer a painful test, and there is no need for patients to feel stressed.

In FIG. 4, an apparatus for forming a video image suitable for threshold perimetry from a microcomputer video signal is shown.

For video images suitable for threshold perimetry,
It was found that two graduated gray values for the background and the test points and a fixed (gaze) symbol, freely selectable as either black or white, were needed. With additional electronics for the microcomputer, images suitable for threshold perimetry can be generated from the four TTL video signals by simple means. A prerequisite for this method to be possible is that the microcomputer supplies a digital video signal consisting of more than 3 bits. The advantage of this method is that the residual video signal of the computer allows a further black and white image to be formed, for example on a second viewing monitor.

Both finely graded gray values are transmitted as digital values (the data bus transmits 8 or more bits depending on the number of gray steps required) from a microcomputer and then sent to an electronic controller (latch). is memorized. Furthermore, the microcomputer has four video processors.
Send out TTL signal via TTL output side. The first of these four TTL signals (A) switches a multiplexer, each of which switches one of the electronic registers to a digital-to-analog converter (D/A converter). Connect to. It is therefore possible to form a video image in which the gray values vary very strongly from a binary image sent out by the microcomputer and taken off from the corresponding video output.

The second TTL signal (B) switches the multiplexer to three-state, so that the D/
A pull-up resistor connected to the input of the A converter supplies the maximum digital word to this converter. This second TTL signal (B) allows the gray value to insert a fixed symbol corresponding to the maximum digital input value of the D/A converter.

Corresponding the fixed symbol to the minimum digital value is possible by a third TTL signal (C), which controls the inversion bit present in the D/A converter. In this way it is possible to represent a fixation (gaze) symbol corresponding to the smallest digital value.

The D/A converter supplies an analog signal to which the required video synchronization pulses can be mixed by means of an analog switch. These pulses are also sent out as a fourth TTL signal from the video processor of the host computer.

[Brief explanation of drawings]

1 is a side view schematically showing an embodiment of the device according to the invention; FIG. 2 is a section along the section line in FIG.
3a and 3b
3c and 3c are diagrams illustrating the actual method in the examination, and FIG. 4 is a block circuit diagram of a device for forming a video image for threshold perimetry. 1... Video monitor, 2... Subject's eyes, 3
...Tsuba support member, 4...Screen, 5...Gaze point.

Claims (1)

[Scope of Claims] 1. A device for searching for a scotoma in an eye of a subject, comprising a screen forming an image, the device comprising a number of closely adjacent black and white spots on the screen. or means for forming an image with colored pixels; means for varying the brightness of the pixels at a high frequency; and means for generating a fixed point 5 on the image for the eye to be examined of the subject. A search device for a scotoma in the eye of a subject, characterized by: 2. The scotoma in the eye of a subject according to claim 1, characterized in that it has means for shifting the fixation point both horizontally and vertically on the screen in order to examine the central and peripheral areas. Search device. 3. The device for searching for a scotoma in the eye of a subject according to claim 1, further comprising means for changing the size of the pixel within the noise pattern. 4. The device for searching for a scotoma in the eye of a subject according to claim 1, further comprising means for generating a high contrast image. 5. The method according to claim 1, further comprising means for compensating the brightness of an image in order to accurately measure the difference in light sensitivity of each retinal location using a photosensor. Point search device. 6. The scotoma search device in the subject's eye according to claim 1, further comprising means for forming an image having pixels only on a predetermined plane. 7. The device for searching for a scotoma in the subject's eye according to claim 1, further comprising means for controlling the pixel distribution and/or brightness by a random function or a program. 8. The device for searching for a scotoma in the eye of a subject according to claim 7, further comprising means for changing the frequency of alternating brightness changes of the pixels. 9. The device for searching for a scotoma in the eye of a subject according to claim 1, further comprising means for forming pixels in various colors or alternating colors. 10. Any one of claims 1 to 9, further comprising means for adjusting the position of the fixed point 5 with respect to the subject's eye to the shape and position of the scotoma in the subject's eye. A search device for a scotoma in the eye of a subject described in . 11. Device for searching for a scotoma in the eye of a subject according to any one of claims 1 to 10, characterized in that it has second image screen means for control by the examiner. 12. The device for searching for a scotoma in the eye of a subject according to claim 1, wherein the brightness variation means is configured to periodically vary the brightness. 13. The apparatus for searching for a dark spot in the eye of a subject according to claim 1, further comprising means for forming a reproducible noise pattern in which the dark part is larger than the bright part. 14. The test object according to claim 1, further comprising means for matching the size and/or brightness of the test point to the position on the flat image screen so that conditions similar to those for a sphere are satisfied. A device that searches for scotomas in people's eyes. 15. The device for searching for a scotoma in the eye of a subject according to claim 14, further comprising means for projecting a noise image onto a sphere. 16. The device for searching for a scotoma in the eye of a subject according to claim 1, further comprising means for inserting a visual field diagram on which a power is displayed on the screen. 17. The subject's eye according to claim 1, characterized in that the luminance is statistically varied by the luminance variation means and is displayed on a monochromatic or multicolored background. Search device for scotoma inside. 18. The apparatus for searching for a scotoma in an eye of a subject according to any one of claims 1 to 17, characterized in that the pixels are uniformly distributed in the form of a noise pattern.