NL8204887A - SYSTEM FOR EXAMINING AND CALCULATING THE FIELD OF VISION. - Google Patents

Description

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MEL, S.A., Güimar (Tenerife), Spain

System for examining and calculating the field of view.

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The invention relates to a system for examining and calculating the field of view for diagnosing and for clinical-experimental purposes of the research in the field of ophthalmology, neurology and neurophysiology.

The subject of the present patent application is a system for the examination and calculation of the field of view, which has substantially new properties and considerable advantages over the hitherto known and used for the same purpose.

The system according to the invention (and the campimeter, respectively) has a design and design that is absolutely new and is based on clinical research, using the technology of the microprocessor and the clinical technology of medical science.

The system of the invention can be applied to that field of medicine related to the visual organ, such as, for example, ophthalmology, neurology and physiology. The system according to the invention can be used in clinical neuro-ophthalmological research for diagnosis and for clinical experimental research for research purposes.

The system according to the invention is both new as a concept and in terms of its physical structure and its functioning. At present no other system is known which has similar properties.

The idea underlying the invention is that an electron beam tube having a large image plane which generates a background and light stimuli capable of producing a positive response from the patient under investigation is used as the campimeter display. , cause.

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Furthermore, a new method in generating and amplifying the image signal makes it possible to simultaneously have a background, which occupies the entire surface of the screen and has a variable brightness, and also examination light stimuli, the position and brightness of which are also variable. and also make visible the points necessary for maintaining the fixation, which are necessary according to the nature of the examination to be carried out. This is achieved by a triple actuation of the cathode of the electron beam tube by an output amplifier specially designed for this purpose.

The basic brightness and the research stimuli independently assume a range of discrete values, ranging from highest to lowest, within a linear light flux ratio of 10,000: 1 within a scale that allows for high resolution. which is sufficient to perform practically all perimetric examinations. The values chosen within the scale can be freely adapted to the nature of the research to be carried out.

The background brightness and the brightness of the research stimuli are automatically calibrated by means of a logarithmic photometer mounted directly on the screen.

One of the advantages, which results from the use of an electron beam tube as a campimetric screen and the electronic image processing according to the invention, is that a high resolution of the angle up to 0.2 ° is possible. A likewise new method for changing the position of the fixed points on the scanning surface of the cathode ray tube makes it possible to extend the investigation to edge zones.

For a screen with a diagonal of 50.8 cm. and a distance of 30 cm. between the screen and the head of the patient, the size of this field is sufficient to 60 ° horizontally and 48 ° vertically. For such an examination of the edge zones, 4 fixed points in the corners of the 8204887 • 4 - 3 screen are made visible one after the other. The further composition of the quadrants examined is automatically carried out according to a program.

Finally, using a cathode ray tube to generate light stimuli offers the opportunity to perform a range of research techniques in a new way, such as, for example, perimetric methods, methods for determining the sharpness of vision, optokinetic methods, adaptometric methods 10 and methods for determining the critical fusion frequency. Perimetric methods determine the absolute achromatic or chromatic threshold value of the retinal sensitivity and its topographic distribution. To this end, the stimulus, the brightness of which can be changed from 0 to its perception by the patient with positive inclusions, appears in front of a background whose brightness is equal to 0. The following parameters are used: - Basic brightness: 0- value; - 20 - Brightness of the research stimulus: from 0 to its detection with positive, discrete inclusions, the value of which can be selected according to a program; - The dimensions of the research stimulus: variable; shape and size according to a program; 25 - The color of the research stimulus: to be chosen according to a program; - Fixed points: a) Number: 1 in 5 different positions depending on the area of the retina to be examined; 30 4 in the pericentral position for the examination of the yellow spot; b) Clarity: It cannot be changed during the examination.

The perimetric methods also make it possible to determine the achromatic and the chromatic differential threshold. For this purpose, for a background with a certain brightness, the brightness of the research stimulus is changed 8204887 ♦ * - 4 - until it differs from the background.

For a given basic brightness value, the increase in the brightness of the research stimulus can be positive or negative.

5 So far, thresholds for a positive increase have been established. However, with the electron beam tube according to the invention it is also possible to measure the differential thresholds in the event of a negative increase in the research stimulus, so that a new technique of perimetry is achieved. The following parameters are used: - Basic brightness: adjustable from 0 to 1,000 apostilb: takes place according to a program; - Fixed points: see above; Brightness of the stimulus: from the value of the brightness of the background can be changed according to program with discrete, positive or negative intervals; - Stimulus dimensions: can be changed according to program from a minimum of 0.2 squared degree; - Stimulus color: to be selected according to a program.

The system according to the invention automatically performs the perimetric examination of the field of view by determining the differential thresholds. By the chosen change of the positions of the fixed points, the area of the field of view to be examined is chosen, ie in the center of the screen for an examination of the central area or in the 4 corners for an examination of the outer areas .

When examining the central area, the perimetry can be limited to a certain length circle, which is chosen according to the clinical or scientific requirements. The thresholds thus obtained are compared with a table of normal values stored in a calculator and the operator is thus informed of the existing correlation.

The solution of the angle can be chosen arbitrarily according to whether more or more information about a particular area of the field of view is desired. In those cases, where loss of sensitivity of the retina can be detected as a result of pathological processes, the resolving difference at the edges of the skin becomes larger, in order to facilitate the delineation.

5 The graphical representation takes place on the monitor of the console or on the printer in the form of a density map according to a scale of gray colors, which shows the degree of sensitivity of the retina and the deviations thereof from normal values. Also, sensitivity 10 of the different points of a longitude circle or a latitude circle in an X-Y coordinate system can be displayed.

With regard to the methods for determining the visual acuity, the system according to the invention, in cooperation with the patient, automatically determines the acuity for viewing angles according to the method of the smallest separation. To this end, light stimuli are shown on the screen, the distance of which is increased or decreased relative to each other, until the patient perceives it as a double or single stimulus and at that moment gives his answer to the calculator by operating a push button. This method of measuring the visual acuity can be applied to any investigative area of the field of view with an arbitrarily variable angle resolving power, or can be limited to a certain length circle.

After the examination has been performed, the console monitor (or printer) displays the graphical representation of the visual acuity value and its topographic distribution on the retina by areas or by longitudinal circles, respectively.

The results thus obtained are compared with a table of normal values stored in the calculator, thereby providing a statistical criterion for the normal values.

In the field of adaptometric methods, the system according to the invention determines the local adaptation to light values and the topographic distribution thereof 8204887-6 on the retina.

When a continuous basic brightness above the barbed threshold is maintained for a certain period of time, a corresponding adjustment of the retinal photo-receivers takes place. Re-adapting the photo receivers to light stimuli that fade over time determines the patient's positive response and stores the value of the perceived stimulus over time. The adapto-10 metric is output to areas or longitudinal circles, with the results appearing on the screen or on the printer, as with the other survey techniques, and compared with tables for normal values.

With regard to the optokinetic research methods 15, the system according to the invention generates luminescent strips on the screen, the width and angular distance of which are variable and which give the impression of a horizontal, vertical or skewed movement and thereby the so-called "nistagmus optokineticist" 20 cause to the observer. The observer's positive reaction to this can be recognized by the reflex movement of the apple of the eye. An additional recognition of the electro-okulographic reaction can take place by the microprocessor and from the periphery, so that an evaluation and registration of the movements of the eye is possible.

With regard to the critical fusion frequency, the system according to the invention generates intermittent stimuli on the screen, the shape, size, brightness, color and frequency of which can be controlled by means of an appropriate programming and with which the values of the critical fusion frequency is measured in the different areas of the retina or on longitudinal circles, which can also be selected using a program.

The results appear on the monitor screen 35 or in the printer and are always automatically compared with the normal values table.

A further advantage of the system lies in the simple operation 8204887 - 7, in which the operator, who guides the patient on a console, has an image monitor and an alphanumeric keyboard at his disposal, which enable him to have a dialogue with the calculator and where he already has Depending on the research technique to be used, the different options are chosen, while at the same time he can observe the progress of the research.

Depending on the options selected, the results of the research will be displayed either graphically or alphanumerically on the screen of the console monitor.

The console is equipped with a printer for printing paper, on which the patient's data and the results of the examination are printed in the form of graphs or alphanumeric characters.

The system according to the invention will next be described with reference to the drawings, in which a preferred embodiment of the system according to the invention is shown, in which:

Fig. 1 shows a block diagram of the central data processing unit (CPU);

Fig. 2 shows the block diagram of an image generating circuit;

Fig. 3 shows the block diagram of an image mixer; and FIG. 4 shows the schematic of the output amplifier according to the invention.

In FIG. 1 shows the block diagram of the central data processing unit (CPU). This shows the micro-processor 1, the memory building block RAM 2 and the EPROM 3 as well as the address decoder 4. The addressing, data and control channels are buffered over the integrated building blocks 5 and 6.

It will be clear to the skilled person that the mikro processor 1 executes each program stored in the memories 2 or 3. The random access memory 2 has a capacity of 4 Kbytes, the erasable, programmable read-out memory 3 has a capacity of 8 Kbytes.

The central processing unit also includes the 8204887-8 logic for addressing the two memory blocks, the decoder 4 and the necessary ports so that it can be operated in time with the video circuit (division of the machine cycle of the mikro processor). .

FIG. 2 shows the block diagram of an image generator.

Here you can see how the integrated building block 7 is fitted, which is formed as a control unit of the electron beam tube and thus is provided with an output for the horizontal synchronization and an output for the vertical synchronization. The selected image shows how the further logic for this module is arranged around the control module 7.

This includes a control clock 8 consisting of a closed phase-locked loop and a sub-circuit for generating signals which are synchronous with the clock signal of the mikro processor 1, so that with the mikro processor 1 a multiplex operation of the memory space is possible. Thereby a transparent functioning of the control unit 7 of the electron beam tube is given 20 and admittedly without waiting times or interruptions for the mikro processor 1 (the machine cycle of the mikro processor is divided into 2 parts, one for the mikro processor 1 and one for reading). of the control unit 7).

Furthermore, the additional logic for this circuit 25 includes a time logic which the control unit 7 configures, the time logic being initiated in the desired manner of scanning at the start of each program. In the graphical way of scanning, a configuration is made with a solution of 340 x 256 points. The alphanumeric scan set of characters is provided in an EPROM memory 9 and additionally contains the additional logic required for mixing graphic and alphanumeric images output on a second monitor, as well as the necessary ports intended for have to generate switch signals, output graphic and alphanumeric image signals, and output inverted image signals for two monitors with control signals, which are independent of each other 8204887-9.

The additional logic for the control circuit 7 further includes a text memory 11 with a sufficiently large memory for the programmed text configuration and several 5-stage buffers 12 and 13, which are for reading the text and image memories of the control unit 7 of the cathode ray tube. needed. Due to the division of the machine cycle, the buffers 12 and 13 also make it possible for the same memory spaces to be read in and read out by the micro-processor 1.

The release outputs of said buffers are controlled by the clock for the image signal and the read / write line. Finally, an address decoder 14 is also provided.

FIG. 3 shows the block diagram of an image mixer, which forms the various image signals and conditions them for supply to the monitor, with which the patient is examined. These signals include the following signals: - Generation of fixed points: this takes place over the integrated building block 15. The generated fixed points can be applied anywhere within the research area; moreover, the form in which they are displayed is variable, so that the monitor allows both a central investigation and an investigation of the periphery. A special way of generating the 4 points at the edges of a square, which is located in the center of the screen, allows the recognition of "skotomes" directly in the center of the research area. The nature and form of these points are determined by means of a program.

- Changing the clarity of the research stimulus; the combination of a digital-to-analog converter 16 and the response of the tube allow the light flashes of this stimulus to be output in excess of 10,000: 1. Under all these values, 40 points can be calibrated with different brightness for each program and adjusted to a logarithmic scale from 0.1 to 8204887 - 10 - 1,000 apostilb. These values can also cover the basic brightness.

- Control of the basic brightness: control is also carried out according to program via a digital-analog converter 17, whereby a certain basic value of the brightness can be set with great precision.

- Buffering: buffering of the pulses for the horizontal and vertical synchronization and the graphic 10 image signals to the research monitor takes place over the integrated building block 18.

Fig. 4 shows the schematic of the image output amplifier. In view of the special properties of these amplifiers, a concrete embodiment is shown in this case. About these amplifiers, the. electric drive of the cathode into the tube of the examination monitor. These amplifiers are capable of converting a series of correspondingly summed currents into a cathode signal. The summation of these currents takes place in transistor 19. The aforementioned amplifier clearly distinguishes the four following parts.

- research stimulus amplifier: it consists of transistors 20, 21 and 22. This amplifier circuit receives two different signals, ie a signal in the form of a voltage which is generated by the digital-analog converter 16 for the research stimulus, which switches the transistor 22 and converts it into a current proportional to this voltage, so that this current 19 flows to the transistor and thus determines the brightness of the total stimulus; the second signal switches the emitter of the transistor 21 and switches the current generated in the previous stage with the speed of the graphical survey image signal.

35 - Fixed point pulse amplifier: This amplifier consists of transistor 23, which supplies a peak current to transistor 19 when the fixed point pulse 8204887-11 occurs.

- Ground current amplifier: this consists of the operational amplifier 24 and the vertical field effect transistor (FET) 25. When a signal from the digital-analog converter 17 arrives at the non-inverting input of the operational amplifier 24, a current is generated, the value of which corresponds to the value of this signal, which flows to the transistor 19.

The extinguishing transistor: this concerns the transistor sistor 26, the object of which is to displace the current which is supplied to the transistor 19 during extinguishing pulses. .

Compared to the hitherto known systems, the arrangement described above has a series of 15 advantages, of which the following in particular can be mentioned.

- An active collaboration between patient and doctor. For this purpose, the physician is provided with a suitable keyboard with preferably 24 keys and a high-level function mapping, as well as two cathode ray tubes, which ensure dialogue with the physician and conducting the examination to the patient. The physician's monitor can simultaneously display the information alphanumerically and graphically, while the patient's monitor preferably works graphically.

- Simple operation: this is mainly based on the already mentioned assignment of the work routines and the program directly on the keyboard and on the automatic monitoring of the answers given by the patient 30. Once the working method has been chosen, further cooperation by the doctor is practically unnecessary.

- Versatility: Since the entire electronics of the device consist of separate building blocks and work with 35 plug-in cards, the device can be used to perform various types of work and calculations by adding further program components.

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- 12 - - High resolution for the angle: The graphic scan provides 340 horizontal and 256 vertical points within the survey range, ie approximately 87,000 points in total, which corresponds to a boundary solution of 0.2 squared degree.

- Printing of the results: the result of the examination can be automatically printed together with the data desired by the doctor after the conclusion of the examination.

10 - Communication capacity: the establishment can forward data and results about a suitable coupling system to a central unit of account.

- Low maintenance and repair costs: since the total electronics of the device are constructed according to the building block principle, a card can be exchanged quickly and easily. Defective parts or circuits can be found with the help of a module with a fault finding program. In many cases, certain errors can be eliminated without technical assistance.

It will be clear to the skilled person that many changes can be made in detail within the scope of the invention and the essential features of the system of the invention. Such changes are also within the scope of the invention and may relate to the individual parts of the device, the type of parts used, the external connections and connections between the cards and all kinds of other parts, without, however, influencing the essence of the invention.

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Claims (4)

2. A system as claimed in Claim 1, characterized in that the amplifier comprises 4 different parts, which respectively fulfill the following tasks: 1. amplification of the test stimulus, in which a circuit 30 with three transistors 20, 21 is provided, which two different signals are provided. received, one of which is a voltage coming from a digital-to-analog converter 16, which switches the transistor 22 and converts it into a current proportional to this voltage, which runs to the summing transistor 19 and so on the brightness of the stimulus determines, while the second signal switches the emitter of a further transistor 21 and converts the current generated by the first signal 8204887-1.5 at the speed of the graphical survey image signal, 2. amplification of the pulse for the fixed point with the aid of a transistor 23, which supplies a spot current to the transistor 19, which drives the cathode of the tube. 3. amplification of the ground current with the aid of p of an operational amplifier 24 and a field effect transistor (FET) 25, wherein a signal originating from the digital-analog converter 17 is converted into a current corresponding in magnitude to this signal, which current flows to the transistor 19, which is the cathode of the tube, 4. an extinguishing section, consisting of a transistor 26, which displaces the current supplied to the transistor 19, which drives the cathode of the tube, with extinguishing pulses. System according to any one of the preceding claims, characterized in that a limit torque or angular solution of 0.2 square degree is given. 4. Field of view and calculation system for the field of view, characterized in that it comprises an electron beam tube with an image plane and means for generating a background and light stimuli on the image plane, which are capable of producing a positive reaction of the patient to be examined. 25 Bladel, December 17, 1982 8204887