FR2518782A1 - DEVICE FOR STUDYING AND CALCULATING THE VISUAL FIELD - Google Patents

Abstract

THE INVENTION RELATES TO AN ELECTRONIC DEVICE FOR STUDYING AND CALCULATING THE VISUAL FIELD. ACCORDING TO THE INVENTION, THE DEVICE INCLUDES A CENTRAL PROCESSING UNIT CPU, SUITABLE TO USE RAM 2 AND EPROM 3 MEMORIES OF A MICRO-COMPUTER 1, INCLUDING BUFFERISATION MEANS 5 AND 6, A VIDEO GENERATOR SYSTEM, ALPHANUMERIC MEMORIES AND GRAPHICS, DRIVERS TO PLAY THEM, A VIDEO MIXER MODIFYING THE CHARACTERISTICS OF THE CATHODIC TUBE AND A VIDEO OUTPUT AMPLIFIER. THE DEVICE IS APPLICABLE FOR DIAGNOSIS OR CLINICAL RESEARCH PURPOSES IN THE OPHTHALMOLOGICAL, NEUROLOGICAL AND NEUROPHYSIOLOGICAL FIELDS.

Description

The present invention relates to a device

  of study and calculation of the visual field, which gives

  essential novelty characteristics and remarkable advantages over the currently known means employed for this purpose. The device of the invention (or apparatus for measuring the visual field) has been conceived and constructed in a completely novel way, based on prior clinical studies.

  during which micro-ordination technology was applied.

  and the Medical Sciences Clinic.

  Its scope includes medical specialties

  those who take care of the organ of vision such as the ophthalmic

  mology, neurology or neurophysiology Its use includes clinical neuro-ophthalmological exploration for diagnostic purposes and experimental clinical research in a

scientific purpose.

  The originality of the device in accordance with this

  tion lies both in its conception and in its structure.

  physical fitness and its usefulness, as there is currently no

  other device that has similar characteristics.

  The basic principle is the use as a measurement screen of the field of a cathode ray tube (CRT) to

  large area, to achieve the background and light stimulations

  which are capable of provoking the positive response of the

subject explored.

  Likewise, an original system of generation and amplification

  application of the video signal, allows the simul-

  ous; a background with variable brightness, light stimulations

  its test, with location and brightness also varied

  the points needed to maintain the fixation, depending on the type of exploration to be

  to a triple excitation of the cathode of the cathode ray tube

  using a specially designed output amplifier

for this reason.

  The brightness of the background and the test stimulations, independently takes a range of discrete values, to a scale that allows a high resolution, traversing a linear luminous flux ratio of maximum to minimum of 10,000: 1, which is sufficient for embrace virtually all perimeter surveys The values chosen throughout the scale

  can freely adapt to the type of study to be carried out.

  The brightness of the background and the light stimulation are automatically calibrated by means of a logarithmic photometer.

placed on the same screen.

  One of the advantages of using the CRT as the field measurement screen and the electronic video system of the invention is that it provides a high angular resolution of up to 0.2 degrees.

  original way of placing the fixing points in different

  rights of the explorable area of the TRC makes it possible to widen the stave

  exploration to peripheral areas.

  The extension of this field reaches the 60 degrees horizon

  rate and the 48 verticals, with a tube 54.14 cm diagonal, placing the patient's eye at 30 centimeters from the screen For peripheral exploration, one places sequentially-four

  fixing points at the corners of the screen

  of the quadrants explored is automatically done

ming.

  Finally, the use of a cathode ray tube

  as a generator of light stimulations allows

  take an original set of exploration techniques such as, for example, 1 Perimetry Techniques 2 Acuity Measurement Techniques 3 Optokinetic Techniques 4 Techniques for Measuring Adaptation Techniques for the critical melting frequency. Perimetric techniques are used to determine the absolute achromatic or chromatic threshold of the sensitivity of the retina and its topographic distribution. For this, on a zero luminous background, increase until it is perceived by the patient. The parameters used are the following

L uminosity of the bottom: zero value.

  Brightness of test pacing: from scratch

  until it is perceived, in positive increments

  peaks whose value is chosen by program.

  Dimensions of test stimulation: form and

  variable size, depending on the program.

  Color of the trial stimulation: chosen by

  gram. Fixation points a) number: 1 to 5 different positions, depending on the retinal zone to be explored 4 in a pericentral position for the study of the zone of the

macula.

  b) brightness: invariable during exploration.

  The perimetry techniques also make it possible to determine the achromatic or chromatic differential threshold and to do this, the brightness of the test stimulation is varied on a certain brightness of the background until the contrast on the background is perceived by the Patient For a given degree of background brightness, the brightness increase of the

  test stimulation may be positive or negative.

  Until now only the thresholds for positive increase have been established. However, with the use of the TRC according to the invention, it is possible to measure the differential thresholds with negative increases in the stimulation.

  test, thereby creating a new technique for

  rimetry The parameters used are as follows: Bottom brightness: adjustable between O 60 and 1000

  "apostilbios" is done by program.

  Fixing points: As in the previous paragraph

ing.

  Brightness of stimulation: variable in interval

  the discrete positive or negative from the

  value of the brightness of the background, by program.

  Dimensions of stimulation-: variable by program-

  me from a minimum of 0.2 square degrees.

  Color of the stimulation selected by program.

  The system of the invention performs automatically

  in record time, perimeter exploration, determined

  When changing the choice of the position of the fixation point, we choose the field of view field to be explored, that is to say in the middle of the screen.

2518782-

  the central field or at the four extreme angles for the peripheral fields. When we explore the central field, we can limit the perimetry to a determined meridian that we choose as we want, sell the clinical or scientific needs Values

  thresholds are compared with a table of normal values.

  stored in the computer and the operator will be informed of the

report obtained.

  The angular resolution can be transformed at will to obtain information-more or less ample of a zone of

  determined field of view In the event of a loss of

  due to pathological processes, the resolution increases

  on the edges of the scotome to facilitate its delimitation.

  The graphic representation is obtained on the monitor of the console or by means of a printer, in the form of a card

  of densities according to a gray scale which represents the degree of

  sensitivity of the retina or its deviation from

  normal fres, or by representing on an X-Y axis system

  the sensitivity of the various points of a meridian or paral-

the the.

  With regard to the measurement techniques of the

  In this way, the system of the invention automatically determines, with the active help of the patient, the angular acuity of the patient, using the method of the separable minimum. To do this, the screen is projected on the screen. light stimulations

  the difference-increases or decreases, until the patient

  as a double or single stimulation, and in this case pushes the button and communicates its response to the computer -This measurement of visual acuity can be done in any explorable area of the visual field, with a resolution angular

  variable at will, or it may be limited to a specific meridian

  mine. Once the exploration is complete, the graph of the value of visual acuity and its retinal topographic distribution can be seen on the monitor (or printer).

by zones or meridians.

  The results obtained are compared with an array of normal values stored in the computer, to obtain a

  statistical criterion of normality -

  Compared to the techniques of measuring acuity, the

  system of the invention determines the values of the adaptation

  hold in light and their retinal topographic distribution.

  By using a fixed threshold brightness for the background for a certain time, retinal photoreceptors are adapted. The photoreceptors are adapted to gradually decreasing luminosity stimulations.

  during the time determines the positive response of the patient and ac-

  cumulates the value of perceived stimulation as a function of time.

  The measurement of the adaptation is done by zones or by meridians, and the results are seen on the screen or on the printer as for the other exploration techniques, in comparison with a

table of normal values.

  With regard to the optokinetic techniques, the system of the invention makes visible on the screen luminous fringes of variable width and angular separation which, by producing a sensation of horizontal, vertical or oblique movement, trigger in the patient who observes them what is called the "optokinetic nistagmis" whose positive response is detected visually by the reflex movement of the

eye-ball.

  Finally, finally, with regard to the frequency

  fusion system, the system of the invention provokes on the

  intermittent stimulations of shape, size,

  minosity, color and frequency controllable by program

  which measure the value of the critical melting frequency

  in the different areas of the retina or on meridians de-

  completed also selectable by program The results

  shown on the monitor screen or on the printer,

  the table of normal values automatically, in

all cases.

  The system has the added advantage of

  felt by its easy handling, so that the operator

  that assists the patient has on a side console a mod-

  video editor and an alphanumeric keyboard that allows him to interact with the computer, choosing the various possible options-depending on the exploration technique to be used,

6 -2518782

  > 6 while being able to follow the progress of the exploration process at the same time The results of each exploration are presented on the screen in graphical or alphanumeric form according to the options established beforehand The console mentioned will have a printer on paper

  which will make it possible to draw the graphical characters or characters

  corresponding to the patient's data or the results obtained

  Other features and advantages of the invention

  will emerge from the detailed description that follows

  attached drawings that schematically and simply illustrate

  for example, a preferred embodiment of the

  Fig. 1 shows a block diagram of the Central Processing Unit (CPU). Fig. 2 shows the block diagram of a block diagram of the central processing unit (CPU).

video generator circuit.

  Figure 3 shows the block diagram of a

video mixer set.

  Figure 4 illustrates the electrical diagram of

  the video output amplifier of the invention.

  According to Figure 1, one can see the representation of the block diagram of the central processing unit (CPU) on

  said figure, we see the microcomputer '1, the modules of

  memory RAM 2 and EPROM 3, and the decoder of directions 4

  management, data and control have been

  "by means of integrated modules 5 and 6.

  The experts in the field will understand it easily,

  the microcomputer will be responsible for executing programs containing

  in memory 2 and 3 RAM 2 provides a

  4 Kbytes, while the EPROM 3 will be

city of 8 Kbytes.

  The central processing unit will also include

  the logic for the control of the two memory modules, the de-

  encoder 4 and the necessary gates that will allow him to

  valiant in time distributed scheme with video circuit 251878 th

  (splitting the machine cycle of the microcomputer).

  Figure 2 shows the block diagram of a

  seems video generator In this figure we can see the

  arrangement of the integrated circuit 7 which is used as a control

  their cathode ray tube and which consequently has outputs with horizontal and vertical synchronism On this

  same figure, it can be seen that all around the control circuit

  their 7, is all the additional logic of service for this circuit, which includes among others A control clock 8 formed by a loop of

  phase (PLL) and a frequency division chain, to produce

  re signals in synchronism with the clock of the microcomputer

  1, which allows to achieve this way with this micro-computer

  multiplexed use of memory space

  this way, without there being any waiting or inter-

  ruptions for the microcomputer 1, the controller 7 TRC acts transparently (the machine cycle of the microcomputer is divided into two parts, one for the microcomputer 1 and a

  other for the reading activity of the controller 7.

  A logic of time, which configures the controller 7,

  accompanied by an initiation by program in the form of

  selected graphically, it is configured by a resolution of 340 X 256 dots The character set necessary for the alphanumeric scanning is stored on an EPROM memory 9 and, in addition, it contains the additional logic necessary for the mixing of alphanumeric and graphic video for output to a second monitor, as well as the set of gates responsible for providing the erasure signals, the graphical and alphanumeric video outputs, and the

  reverse video for two monitors with independent control signals

  counterparts. An alphanumeric memory 11 that provides the space

  sufficient memory for the alphanumeric configuration

  grammed. Various "drivers" with three states, 12 and 13, which are

  necessary to read alphanumeric memories.

  chart and graph from TRC controller 7 -

  They also make it possible, thanks to the distribution of said machine cycle, to read and write the memory spaces from the microcomputer 1 The "enable" outputs of the mentioned drivers are directed by the video clock and by the reading line /writing. Finally, the decoder of

corresponding directions 14.

  In FIG. 3, the block diagram is shown

  of a video mixer set responsible for provoking and pre-

  parse the various video signals for the patient's exploration monitor Among these signals, we find the following Generation of fixation points: this function

  is achieved by means of the integrated circuit 15 Fixing points

  products can be placed freely at any point in the exploration zone and, in addition, their presentation mode can be modified, which gives the monitor the capacity for central and peripheral exploration A special generation modality of four points placed on the edges of a square in the center of the screen makes it possible to notice the scotomes at the very center of the zone of exploration The control of

  modality and presence of these points is by program.

  Variation in luminosity of the test pacing The combination of a digital / analog converter 16 and the response of the tube allow an excursion of the value of the luminous flux of this stimulation greater than 10 000: 1 It is possible to calibrate by program, among all these values, 40 points of different brightness and adjusted according to a logarithmic scale

  from 0.1 to 1,000 "apostilbios" These values can, moreover, be se-

superimpose on the shine of the background.

  Control of the background gloss: It is also done programmatically by means of a digital-to-analog converter 17 which makes it possible to precisely adjust a determined value

for the shine of the background.

  - "Bufferisation": Buffering-pulses of

  horizontal and vertical synchronism is achieved by the integrated circuit

  according to 18, as well as that of the video signal of the monitor

-exploration of the patient.

  Figure 4 shows the electrical diagram of the

  In this case, given the special characteristics of this amplifier, we preferred

  present a concrete realization of it.

  By means of this amplifier, the electrical excitation of the cathode of the probe of the exploration monitor is provoked and it has the capacity of converting into a cathodic signal a set of currents suitably summed. These currents add up in the transistor. said amplifier, four well-defined sections can be distinguished which are: The amplifier of the test stimulation: it is formed by the set of transistors 20, 21, and 22 This set

  amplifier receives two different signals, the first

  voltage from the analogue digital converter

  a test stimulator 16, which drives the transistor 22 and which is converted to a current proportional to said voltage, so that this current is supplied to the transistor 19 and determines the brightness of this stimulation; the second signal

  drives the emitter of transistor 21 and switches the current

  in the previously described step at the speed of the graphic video.

  An amplifier of the point pulse of fixa-

  This amplifier is formed by the transistor 23 and delivers a maximum current to the transistor 19 when the pulse of

fixation is presented.

  A bottom current amplifier: it is formed by the operational amplifier 24 and the transistor type

  Vertical FET 25 When the non-inverting input of the amplification

  24 receives a signal from the digital-to-analog converter 17, a proportional current is produced.

  to this signal which is delivered to the transistor 19.

  An erase transistor: it is formed by the transistor 26 and its mission is to move the injected current

  to transistor 19 in the presence of erasure pulses.

  The assembly described by all the foregoing, has compared to the known systems a series of advantages, among which we can distinguish: The interaction with the patient and the doctor: it has for this purpose a suitable keyboard , preferably 24 keys, with high level functional assignment, as well as two cathode ray tubes to establish dialogue with the doctor and the patient's exploration work The doctor's monitor can simultaneously present the information in the form of alphanumeric and graphical, while the monitor

  patient works mostly graphically.

  Simplicity of handling: it is mainly determined by the assignment already commented of work routines and programmed directly with the keyboard, as well as by the automatic monitoring of the response of the patient Once the mode of work was chosen, the intervention the doctor is not

practically not necessary.

  Universality: Since all electronics in the equipment are modular and mounted on punched cards, the equipment can perform different types of work and calculation if the programming modules are simply added.

  The high angular resolution: the graphical

  that provides 340 horizontal points and 256 vertical points within the exploration area, which implies a total of approximately 87,000 points, which means a limiting resolution

0.2-square degrees.

  The impression of the results: the result of the explo-

  ration, as well as the data required by the doctor, may

  be printed automatically and graphically at the end of the ex-

  ploration. Communication capability: It is possible to transmit data or results to a central computer

  by means of a suitable interphase system.

  A relatively low maintenance and repair cost: all electronics of the equipment being modular, the replacement of a card is an easy and quick task One can identify the zone or the circuit damaged by means of a module of Diagnostic Routine Programming In many cases, technical assistance is not required.

to repair some faults.

  It goes without saying that the device has been described and represented only for explanatory purposes, in no way limiting,

  and that various modifications of detail might be

  in the embodiment shown without departing from the scope of the invention.

  Thus, the constituent elements of the

  the type of components used, the internal connections and the connections between cards, could be modified to the extent that they do not alter the fundamental principle of

the invention.

Claims (4)

  1 A device for studying and calculating the field   visual, applicable for the purposes of diagnosis or research   experimental program in the field of ophthalmology, neurology or neurophysiology, characterized in that it comprises in combination: A) a central processing unit (CPU) having a   microcomputer (1) suitable for the execution of the programs   held in RAM (2) and EPROM (3) memory modules, -   of a direction decoder (4) and means (5), (6) for buffering the directional channels', data and contrdle.   B) A generator system vi deo made from a   integrated means (7) for the control of a cathode ray tube   equipped with outputs for horizontal and vertical synchronisms   tical, and where provision has been made for the logic of servitude   cathode ray tube brazier: a) a control clock (8) formed by a phase loop (PLL) and a frequency division chain   which produces signals in synchronism with the clock of the micro-   computer (1) of the central processing unit (CPU) b) a time logic, which configures said control means (7), accompanied by a programmatic beginning of the selected scan form and which, so graphic, is configured by a resolution of 340 X 256 points, while, in alphanumeric scanning, the necessary character set   stored in a memory (9), of the EPROM type, preferably   in addition to the additional logic required to   for the mixing of graphic and alphanumeric   reverse video, for two monitors, with con- independent control;   (c) an alphanumeric memory (11) for the configuration programmed alphanumeric ration;   d) three-state drivers (12,13) for   alphanumeric and graphical memories from the controller means (7) of the tube and for reading and writing the same memory spaces from the microcomputer (1), and e) the direction decoder (14) which is necessary . C) A video mixer assembly, responsible for producing and preparing the various video signals for the patient's exploration monitor and capable of performing the following functions: 1) generating, by means of an integrated module (15), the   fixing points which can be placed freely in   which part of the exploration area and which can   the manner of presentation;   2) change the brightness of the stimulation of   sai, allowing, by means of the combination of a digital-to-analog converter (16) and the response of the tube, an excursion of the value of the luminous flux of the upper stimulation to 10,000: 1;   3 e) control background brightness, by program,   by means of a digital-to-analog converter (17), which   makes it possible to adjust with a great precision a determined value of this background brightness, and   4) buffer the pulses of horizontal synchronism   zontal and vertical, as well as the graphic video signal of the patient's exploration monitor by means of an integrated module (18)   D) Finally, a video output amplifier   for the electrical excitation of the monitor tube of   which has the capacity to convert to a cathodi-   that a set of currents suitably added to the medium a transistor (19) adequate.   2 Device according to claim 1, characterized in that, in the video output amplifier, there are four differentiated sections, the missions of which are as follows: 1 Amplification of the test stimulation, for which there is arranged a a set of three transistors (20 to 22) which receive two different signals, the first of these signals consisting of a voltage from a digital-to-analog converter (16) which drives a transistor (22) and which is converted into a proportional current h this one, this current   is then injected into the adder transistor (19) to determine   the brightness of the stimulation, then read the second signal   the transmitter of another transistor (21) and switches the   produced by the first signal at the speed of video than exploration.   2 Amplification of the fix point pulse   by means of a transistor (23) which injects a maximum current   the transistor (19) for exciting the cathode of the tube.   3 Background current amplification by means of an operational amplifier (24) and a transistor (25) of the type   FET, for which a signal from a digital converter   tal / analog (17) converts to a current proportional to   the latter which is injected into the transistor (19) which excites the cathode of the tube.   4 Erasing section, consisting of a transistor   (26) which moves the injected current to the transistor (19) which excites   the cathode of the tube when the erasing pulses are presented tent.   3 Device according to the preceding claims,   characterized by the fact that it offers an angular resolution mite of 0.2 square degrees.   4 Application to the study and measurement of the field   visual device according to claims i to 3.