RU2217039C1 - Method for carrying out ophthalmologic examination of vision field - Google Patents

Abstract

FIELD: medicine. SUBSTANCE: method involves concentrating patient sight on fixation point. Visual stimulus of variable brightness is shown to a patient in various vision field points. Each time after the patient has detected the visual stimulus, sight concentration point is selected as the point where the visual stimulus detected by the patient has been shown. The fact the visual stimulus has been detected by the patient is determined by checking eye-moving response. After having selected patient sight concentration point as the point the previous visual stimulus had been detected by the patient, showing visual stimulus in any next point on the vision field starts. Eye-moving response is recorded by using eye turn gage to fix the fact the visual stimulus has been detected by the patient. In recording the eye-moving response and selecting the next point the patient sight is to be concentrated, patient sight concentration point coordinate changes are determined and compared to the point the next visual stimulus is to be shown relative to the point the previous visual stimulus has been shown. EFFECT: wide range of observation angles; high quality of images produced. 4 cl, 1 dwg

Description

 The invention relates to medicine, in particular to the field of ophthalmic studies of the visual field, and can mainly be used to determine the boundaries of the visual field and identify localized fields of view with dysfunction of the brightness contrast sensitivity of the organs of vision in the diagnosis of pathology of the retina, optic nerve and central nervous system.

 Known methods for perimetric and campimetric studies of the field of view and their devices according to the copyright certificates of the USSR 810209, 1981; 982646, 1982; 1205890, 1986; 1297793, 1987; 1671261, 1991; 1782530, 1992; USSR patent 1489572, 1989; the application of the Russian Federation 94008967, published on 10.20.96, and the application of Germany 2428481, 1976, as well as from the medical literature (Multivolume Guide to Eye Diseases. Volume 1, Book 2. - M .: Medgiz, 1962, pp. 120-127, 133 -135. Sequential images in the norm and in diseases of the optic-nervous pathway. - Bulletin of Ophthalmology, 1970, 4, pp. 44-49; Urmacher L. S., Aizenshtat L. I. Ophthalmic devices. - M .: Medicine, 1988 , p. 45). These known methods include in their common part fixing the patient’s gaze at the fixation point invariably located in the center of the field of view, presenting to the patient one or more test objects or light stimuli moving, most often, along the meridian of the field of view from its center to the periphery or in the opposite direction, the patient's perception of moving test objects or light stimuli, the patient's message about the results of his perception of test objects or light stimuli orally or using the signal button and obtaining information about the position of the boundaries of the field of view, as well as the position and size of the sections of the field of view with dysfunction of brightness contrast sensitivity based on the results of recording the position of moving test objects or light stimuli at the time of receipt of the corresponding patient messages.

 The disadvantage of these known methods of studying the field of view is the low accuracy of determining the position of the boundaries of the field of view and the position and size of the sections of the field of view with a dysfunction of brightness contrast sensitivity, which is caused by the delay in the moments of registration of the position of moving test objects or light stimuli with respect to the moments when they cross the borders field of vision or its defective areas, which is due to the duration of the visuomotor reaction of the patient when he performs the message, to As a rule, growing during the examination due to its fatigue. In this case, the lowest accuracy of the research results is ensured when examining elderly patients with, as a rule, a delayed visual-motor reaction, as well as in the case of detecting small isolated visual field defects, especially when they are central and paracentral.

 In addition, these known methods allow you to determine the threshold value of the brightness contrast sensitivity of the studied sections of the field of view only in the case of multiple examinations of the patient in full operations provided by known methods, with different values (not less than 6-8) of the brightness of the used moving light stimuli. This leads, on the one hand, to a significant increase in the time taken to complete the examination and, on the other hand, as a result, to greater fatigue of the patient, which causes a decrease in the accuracy of the results of the study.

 Known methods for ophthalmic research of the field of view according to the copyright certificates of the USSR 1217406, 1986; 1222269, 1986; 1553045, 1990; 1642996, 1991; 1711812, 1992; 1766361, 1992 and patents of the Russian Federation 2053702, 1996; 2127543, 1999, as well as from the literature (Volkov V.V., Sukhinina L. B., Ustinova E. I. Glaucoma, perglaucoma and ophthalmic hypertension. - L .: Medicine, 1985, p. 75-88). These known methods provide for the general part of fixing the patient’s gaze at the fixation point invariably located in the center of the field of view, alternating static presentation of light stimuli to the patient at various points of the field of view with increasing or decreasing brightness over time, the patient’s perception of the presented light stimuli, and the patient’s message about the appearance or disappearance of the perceived light stimulus using the signal button and the determination of the threshold value of the brightness contrast is sensitive STI at each point in the presentation of the light stimulus on the basis of the luminance values of the light stimulus at time of receipt of the corresponding patient messages.

 Since when using these known methods a static presentation of light stimuli to a patient is carried out at various points of the field of view, the final value of the duration of his hand-eye reaction does not lead to an error in determining the position of the boundaries of the field of view and the position and size of sections of the field of view with dysfunction of brightness contrast sensitivity. Therefore, these methods provide higher accuracy in determining the indicated results of the study, which is limited, in addition to the error in fixing the patient’s gaze at the fixation point, only by the discreteness of the location within the field of view of the points of presentation of light stimuli and their sizes.

 However, the use in these known methods for determining the threshold value of the luminance contrast sensitivity of the field of view based on the brightness value of the light stimulus with increasing or decreasing in time brightness at the time of receiving the patient’s message causes an error that occurs due to a change in the brightness of the light stimulus over a time equal to the final duration of the visuomotor reaction of the patient when he implements a message using the signal button. The indicated error takes on the most significant values in the case of examination of elderly patients, who, as a rule, have a delayed visual-motor reaction, as well as in case of patient fatigue.

 In addition, the need for constant fixation of the patient’s gaze on the same, permanently located fixation point contributes over time to patient fatigue during the examination, which, as practice shows, leads to an involuntary deviation of the patient’s gaze from the fixation point and therefore causes an increase in determination errors the position of the boundaries of the field of view and the position and size of the sections of the field of view with dysfunction of brightness contrast sensitivity.

 The closest in terms of the actions taken and the achieved result should be considered the method of studying the field of view according to the author's certificate of the USSR 1528434, 1989, A 61 B 3/02, A 61 F 9/00. The prototype method involves fixing the patient’s gaze at a fixation point that is invariably located in the center on the inner surface of the screen applied to the examined eye in the form of a hollow spherical segment, alternately presenting the patient with visual stimulus at various points of the visual field of the screen, including with a changing brightness, the patient’s perception of the presented visual stimulus, the patient’s message about the appearance of the visual stimulus perceived by him using the signal button and is determined the threshold value of the brightness contrast sensitivity at the indicated points of the field of view based on the brightness value of the visual stimulus at the time of receipt of the patient's message.

 Provided by the prototype method, as well as all other known methods of studying the visual field, the patient’s execution of a message about the appearance of a visual stimulus perceived by him, most often using a signal button, causes a delay in the time of receipt of the patient’s message in relation to the time of perception of the visual stimulus, which arises due to the finite duration of the visuomotor reaction proceeding from the retina of the eye through the brain to the arm, which controls the signal button at the t muscle reaction. The long length of the opto-neural path and the inertia of the muscular reaction of the patient’s hands lead to a significant duration of the indicated visual-motor reaction, especially in elderly patients and people with pathology of the nervous and muscular systems, as well as the musculoskeletal system. The delay in the time of receipt of the patient’s message causes an error in determining the threshold value of the brightness contrast sensitivity of the visual field sections, which occurs due to a change in the brightness of the visual stimulus over a time equal to the duration of the given visual-motor reaction of the patient when he implements a message using the signal button.

 Moreover, as in the case of the implementation of all known methods of similar purpose, the constant fixation of the patient’s gaze on the same, invariably located fixation point leads to fatigue of the patient during the examination, which, as practice shows, causes an involuntary deviation of the patient’s gaze from the point fixation and therefore leads to an increase in errors in determining the position of the boundaries of the field of view and the position and size of sections of the field of view with dysfunction of brightness contrast sensitivity. In addition, this requires the doctor-researcher to periodically monitor the correct fixation of the patient’s gaze and in case of violation of the interruption of the examination to restore the correct fixation of the gaze.

 The disadvantages of the method of studying the field of view selected for the prototype are insufficiently high accuracy in determining the threshold value of brightness contrast sensitivity and the position of the boundaries of the field of view and its sections with dysfunction of brightness contrast sensitivity, as well as the complexity of the method associated with the need for periodic monitoring of the correctness of fixing the patient’s gaze research physician.

 The objectives of the invention are to increase the accuracy of determining the threshold value of the luminance contrast sensitivity and the position of the boundaries of the field of view and its sections with the dysfunction of luminance contrast sensitivity, as well as simplifying the implementation of the method.

 The goals are achieved, according to the invention, in that the proposed method of ophthalmic examination of the visual field, including, in accordance with the prototype, fixing the patient’s gaze at the fixation point, alternately presenting the patient with different brightness field visual stimulus, the patient’s perception of the visual stimulus and determination of the brightness threshold of perception of a visual stimulus by a patient differs from the prototype in that after each perception by a patient of a visual stimulus, nnogo in another point of the field of view, the selected fixation point of view of the patient at the point of presentation of the visual stimulus perceived by the patient and the fact that the perception by the patient of the visual stimulus is determined based on its registration oculomotor reaction. In this case, the presentation of the visual stimulus at the next point of view begins to be carried out after selecting the point of fixation of the patient’s gaze at the point of presentation of the previous visual stimulus received by the patient, and the oculomotor reaction of the patient is recorded to determine the perception of the visual stimulus using the eye rotation sensor, during registration oculomotor reaction of the patient when choosing the next fixation point of the patient’s gaze determine changes in the coordinates of the fixed point The patient gaze ratios and compare them with the coordinates of the next point of presentation of the visual stimulus relative to the previous point of presentation of the visual stimulus.

 The choice of the point of fixation of the patient’s gaze at the point of presentation of the patient’s visual stimulus after each perception of the patient’s visual stimulus presented at the next point of view, the fact of the patient’s perception of the visual stimulus based on the recording of his oculomotor reaction using the eye rotation sensor by determining changes in the coordinates of the point of fixation the patient and comparing them with the coordinates of the next point of presentation of the visual stimulus relative to the previous the point of presentation of the visual stimulus, as well as the implementation of the presentation of the visual stimulus at the next point of the field of view after selecting the fixation point of the patient’s gaze at the point of presentation of the patient’s previous visual stimulus, increase the accuracy of determining the threshold value of the contrast contrast sensitivity and the position of the boundaries of the field of view and its sections with dysfunction brightness contrast sensitivity, as well as simplifying the implementation of the method. This provision is confirmed by the following circumstances.

 The transfer by the patient, appropriately instructed before the examination, of the point of fixation of the gaze to the point of the next presentation of the visual stimulus perceived by the patient last, leads to the rotation of his eye in the direction of the newly selected fixation point. The significantly shorter length of the nerve path, the significant thickness of the optic nerve, and therefore its high throughput, as well as the low inertia of the ocular muscle ensure the rotation of the eye at a sufficiently high speed with a short duration of the oculomotor reaction of the patient. In this case, the determination of the patient’s perception of the visual stimulus based on the registration of his oculomotor reaction using the eye rotation sensor occurs automatically, does not require the participation of a research physician and therefore does not delay the time of recording the fact of the patient’s perception of the visual stimulus associated with subjective data of a research doctor. All of the above provides an increase in the accuracy of determining the threshold value of luminance contrast sensitivity on the basis of recording the current value of the changing brightness of the presented visual stimulus at the time of registration of the oculomotor reaction of the patient during its perception.

 Determining the coordinates of the patient’s gaze fixation point coordinates and comparing them with the coordinates of the next visual stimulus presentation point relative to the previous visual stimulus presentation point makes it possible to control the patient’s oculomotor reaction when changing the gaze fixation point in accordance with the position of the next presented visual stimulus perceived by the patient. This circumstance, together with the presentation of the visual stimulus at the next point of the field of view only after choosing the point of fixation of the patient’s gaze at the point of presentation of the visual stimulus perceived by the patient, provides the correct fixation of the patient’s gaze and increases the accuracy of determining the position of the boundaries of the visual field and its sections with dysfunction of brightness contrast sensitivity.

 In addition, the need to periodically change the position of the chosen point of fixation of the gaze after each subsequent perception by the patient of a visual stimulus leads to forced movement of the patient’s eye and, as a result, to less fatigue when fixing the gaze during the examination, which provides higher accuracy of fixing the gaze at the next fixation point and, therefore, improving the accuracy of determining the position of the boundaries of the field of view and its sections with dysfunction of brightness contrast sensitivity.

 Since the implementation of the proposed method does not require fixing the patient’s gaze on one permanently located fixation point, there is no need for periodic monitoring of the accuracy of fixation of the patient’s gaze by the doctor-researcher, which simplifies the method and therefore allows the doctor-researcher, without being distracted by secondary operations, directly in the process surveys evaluate the results of studies and analyze them. Moreover, the simplification of the method allows you to perform with it the study of the field of view of the patient by a person who does not have the qualifications of an ophthalmologist.

 The above indicates the achievement of the stated objectives of the present invention due to the presence of the proposed method of these distinctive features.

The essence of the proposed method of ophthalmic examination of the visual field in the case of using visual stimuli with increasing brightness over time is as follows:
- instruct the patient to be attentive and each time to translate and fix the look on the visual stimulus that reappears in the field of view;
- close the patient’s unexplored eye, for example, with a bandage or a shutter;
- present to the patient in one of the points of view the first visual stimulus;
- after the patient perceives the first presented visual stimulus at the time of the patient’s transfer of the gaze and fixes it at the point of presentation of the perceived visual stimulus, the oculomotor reaction of the patient is recorded using the eye rotation sensor, thereby determining the fact that the patient perceived the presented visual stimulus;
- present to the patient at one of the points of the field of view or his investigated area the next (second) visual stimulus with increasing brightness over time;
- after the patient’s perception of the next (second) presented visual stimulus at the time of the patient’s transfer of gaze and fixation of it at the point of presentation of the perceived next (second) visual stimulus, the oculomotor reaction of the patient is recorded using the eye rotation sensor, thereby determining the fact that the patient perceived the presented next (second) visual stimulus, after which the presentation of the previous (first) visual stimulus is completed;
- at the time of registration of the oculomotor reaction of the patient, the brightness value of the perceived next (second) visual stimulus is determined and recorded;
- on the basis of the patient’s oculomotor reaction recorded by the eye rotation sensor, changes in the coordinates of the fixation point when the patient transfers the gaze and fixes it at the point of presentation of the perceived next (second) visual stimulus;
- compare the obtained changes in the coordinates of the fixation point of the patient’s gaze on the next (second) visual stimulus with the coordinates of the point of presentation of the next (second) visual stimulus relative to the point of presentation of the previous (first) visual stimulus;
- register the coordinates of the presentation point of the next (second) visual stimulus relative to the presentation point of the previous (first) visual stimulus.

 Next, the operations of the method are periodically repeated, starting with the fifth step, upon presentation of the next visual stimulus, that is, the third, fourth, fifth, and so on, within the field of view or its investigated area. In this case, the presentation of visual stimuli is performed at all points of the field of view necessary for the examination or its studied areas, selected with the required discreteness. The results of the study for each studied point of view are two coordinates of the point of view relative to the center of the field of view (registered coordinates of the point of presentation of the next visual stimulus relative to the point of presentation of the previous visual stimulus) and the threshold value of brightness contrast sensitivity corresponding to the brightness of the visual stimulus perceived at this point.

 The drawing shows a structural diagram of a device with which the proposed method of ophthalmic examination of the field of view can be implemented, where 1 is the patient’s examined eye, 2 is the eye of a research doctor, 3 is a sectional view of the screen, 4 is a screen opening 3, 5 - sight glass, 6 - spectro-splitting glass, 7 - clock pulse generator, 8 - frequency divider, 9, 10 - first and second pulse counters, 11, 12 - first and second digital-to-analog converters, respectively, 13, 14 - first and second registers, respectively ry, 15, 16 - respectively, the first and second decoders, 17, 18 - respectively, the first and second blocks of the current key 19 - eye rotation sensor, 20 - ADC, 21 - trigger 22 - and 23 disjunctors - computer.

The screen 3 is made in the form of a hollow spherical segment of opaque material and is equipped with LEDs (not shown in Fig. 1) mounted on its inner surface, designed to generate optical radiation in the visible wavelength range and to provide visual stimuli. The number of LEDs and the discreteness of the position of the places of their installation on the inner surface of the screen 3 are determined by the discreteness of the location of the presentation points in the visual field of visual stimuli necessary in the study. In the center of the screen 3, a hole 4 of the screen 3 is made, closed by a sight glass 5, transparent for optical radiation, with a mark applied on it, for example, in the form of a crosshair. From the side of the outer surface of the screen 3 opposite the opening 4 of the screen 3 is installed at an angle of, for example, 45 ^° to the axis of the screen 3 passing through the center of the opening 4 of the screen 3 and the center of the patient’s eye 1, spectro-splitting glass 6 transmitting visible optical radiation and reflecting infrared optical radiation. Spectrodividing glass 6 is also marked, for example, in the form of a crosshair, the center of which is located on the axis of the screen 3, passing through the center of the hole 4 of the screen 3 and the center of the examined eye 1 of the patient. In a more simplified embodiment of this device, instead of spectro-splitting glass 6, a translucent mirror can be used. On the side of the inner surface of the screen 3 is located not shown in the figure frontal chin support for the patient, installed with the ability to move in two coordinates in a plane perpendicular to the plane of the drawing, and subsequent fixation. Moving the frontal-chin support provides the initial installation of the patient’s head in a position in which the center of the patient’s eye 1 is located on the axis of the screen 3 passing through the center of the opening 4 of the screen 3. This alignment is carried out when the researcher examines the patient’s eye 1 using marks in in the form of crosshairs, which are equipped with sight glass 5 and spectrodividing glass 6. When the patient’s head is first set to a position in which the center of the examined eye of 1 patient p positioned on the axis of the screen 3, passing through the center of the hole 4 of the screen 3, the eye 2 of the research doctor should be located on the specified axis behind the spectro-splitting glass 6 from the side opposite to the screen 3.

 The eye rotation sensor 19 is made optoelectronic, has a sensitivity to optical radiation of the infrared wavelength range and is mounted with its optical axis located in a plane perpendicular to the axis of the screen 3 connecting the patient’s eye 1, the center of the opening 4 of the screen 3 and the eye 2 of the research doctor so that the infrared optical radiation reflected from the patient’s examined eye 1 after passing through the sight glass 5 and reflected from the spectro-splitting glass 6 falls into the field of view of the sensor 19 the one eye. The eye rotation sensor 19 is provided with an infrared radiation source not shown in the figure, which is based on, for example, an LED for emitting infrared optical radiation, and is mounted so that its optical axis is parallel to the optical axis of the eye rotation sensor 19. As the sensor 19 of the rotation of the eye can be used currently known from the prior art devices for measuring angles of rotation of the eye, for example, according to copyright certificates of the USSR 1438691, 1988; 1507313, 1989 and 1581268, 1990.

 If it is necessary to provide a higher angular resolution when recording the oculomotor reaction of the patient, a video camera sensitive to infrared optical radiation can be used as an eye rotation sensor 19. In the latter case, the initial alignment of the studied eye of the patient 1 may be performed not by direct observation by the eye of the research doctor 2 through the spectro-splitting glass 6 and the opening 4 of the screen 3 closed by the sight glass 5, but based on the observation of the image of the studied eye 1 of the patient formed by the video camera on the screen the computer display 23. Therefore, provided that the camera’s eye rotation is used as the sensor 19, it is mounted so that its optical axis passes through the center of the hole 4 of the screen 3 and npt study eye 1 of the patient. In this case, this allows not to use spectro-splitting glass 6 in the device.

The eye rotation sensor 19 through an analog-to-digital converter 20 is connected to the first input of the computer 23. The output of the clock pulse generator 7 is connected through the frequency divider 8 to the inputs of the counting pulses of the first and second counters 9 and 10 pulses. The output of the parallel digital code of the first counter 9 pulses is connected to the inputs of the first digital-to-analog converter 11 and the first register 13, and a similar output of the second counter 10 pulses is connected to the inputs of the second digital-to-analog converter 12 and second register 14. The overflow outputs of the first and second counters 9 and 10 pulses are connected with the inputs of the disjunctor 22, the output of which is connected to the second input of the computer 23. The first and second outputs of the computer 23 are connected to the inputs of the first and second decoders 15 and 16, respectively, each of which has 2 ^N inputs and N outputs, where N is the number of 3 LEDs placed on the screen. Each of the N outputs of the first and second decoders 15 and 16 is connected to one of two inputs of one of the N current keys included in each of the current key blocks, respectively, of the first and second current key blocks 17 and 18. The output of each of the N current keys of the first and second blocks of current keys 17 and 18 is connected to one of the N LEDs located on screen 3, and the second inputs of N current keys of the first and second blocks 17 and 18 of current keys are connected to the outputs of the first and second digital-analog converters 11 and 12. The input of the trigger 21, which is used as a trigger with a counting input, is connected to the third output of the computer 23, the direct output of the trigger 21 is connected to the recording input of the first register 13 and the input of the beginning of the counting of the second pulse counter 10, and trigger output version 21 is connected to the recording input of the second register 14 and the input of the beginning of the counting of the first counter 9 pulses. The outputs of the first and second registers 13 and 14 are connected respectively to the third and fourth inputs of the computer 23. The fourth output of the computer 23 is connected to the second input of the frequency divider 8. As a computer 23 can be used a personal computer equipped with a keyboard, display and printer.

 A device that implements the proposed method of ophthalmic examination of the visual field, works as follows.

 The research doctor instructs the patient to be attentive and each time to shift and fix his gaze on the visual stimulus that reappears in the field of view, sets the patient on a chair facing the inner surface of the screen 3, sets the patient’s face in the frontal chin support and closes the patient with a blind eye or damper, which can be equipped with frontal chin support. Then, observing with eye 2 through spectrodividing glass 6, sight glass 5 and opening 4 of screen 3 under conditions of illumination by visible optical radiation of the internal cavity of screen 3, the doctor-researcher pre-centers the examined eye 1 of the patient relative to the axis passing through the center of the opening 4 of screen 3, ensuring the alignment of the center of the pupil of the studied eye of 1 patient and the centers of the marks in the form of crosshairs on spectrodividing glass 6 and sight glass 5. This alignment is carried out by moving the frontal selection one support in two coordinates in a plane perpendicular to the plane of the drawing, after which the position of the frontal-chin support is fixed.

 In the case of using a video camera that is sensitive to optical radiation of the infrared range as the eye rotation sensor 19, upon preliminary centering of the examined eye of the patient 1, the infrared radiation source (not shown) is turned on, which is equipped with the eye rotation sensor 19. Infrared optical radiation from this source passes through the sight glass 5 and the opening 4 of the screen 3, is reflected from the studied eye 1 of the patient, again passes through the opening 4 of the screen 3 and the sight glass 5, and is detected by the eye rotation sensor 19. The video camera that performs the function of the eye rotation sensor 19 converts infrared optical radiation into an analog electric image signal of the patient’s examined eye 1, which, after being converted by an analog-to-digital converter 20 into a digital image signal, is input into a computer 23. Computer 23 converts the digital image signal of the patient’s examined eye 1, for example, in a digital image signal with three gradations of brightness corresponding to the values of the infrared optical radiation flux reflected unit of area, respectively, of the pupil, iris and sclera of the studied eye of 1 patient, and reproduces this tri-graded image of the studied eye of 1 patient on the screen of its display to the doctor-researcher. This becomes possible, since the optical radiation is reflected to the greatest extent by the sclera, to a slightly lesser extent, by the iris, and to the least extent, by the pupil of the examined eye of 1 patient. Observing on the display screen of the computer 23 the image of the examined eye 1 of the patient and the mark in the form of a crosshair on the sight glass 5, the doctor investigates the combination of images of the center of the crosshair with the center of the pupil of the studied eye of the patient 1 by moving the frontal chin support in two coordinates, and then fixes it position.

 Then, the doctor-researcher enters into the computer 23 from the keyboard such necessary parameters for conducting a patient examination, such as, for example, the position of the boundaries of the studied area of the field of view, the discreteness of the location of the points of presentation of visual stimuli in this area, and the value of the necessary rate of increase in brightness of the presented visual stimulus. In accordance with the entered value of the required rate of increase in brightness of the presented visual stimulus, the computer 23 generates a binary digital code and feeds it to the frequency divider 8, in accordance with the value of which the internal connections of the frequency divider 8 are switched, providing the required pulse frequency division coefficient corresponding to the necessary speed increase in brightness of the visual stimulus presented. In accordance with the entered parameters of the position of the boundaries of the studied field of view and the discreteness of the location in this area of the presentation points of visual stimuli, the computer 23 using the program stored in its storage device determines the presentation of visual stimuli at various points of the field of view selected for the study and the corresponding sequence of numbers LEDs installed on screen 3 and providing visual stimuli in the specified order.

 Before the presentation of visual stimuli to the patient, the first and second counters of 9 and 10 pulses, the first and second registers 13 and 14, and trigger 21 are reset. A clock pulse generator 7 generates clock pulses and feeds them to a frequency divider 8, which transmits clock pulses in accordance with a set division factor, providing a predetermined clock frequency value corresponding to the required rate of increase in brightness of the presented visual stimulus. The clock pulses missed by the frequency divider 8 are fed to the inputs of the counting pulses of the first and second counters 9 and 10 pulses.

 From the direct output of the trigger 21, the logic zero voltage is supplied to the input of the counting of the second counter 10 pulses, and therefore, the second counter 10 pulses does not count pulses from the frequency divider 8. Since the logic unit voltage is supplied from the inverse output of trigger 21 to the input of the counting of the first counter 9 pulses, the first counter 9 of pulses counts the clock pulses coming from the output of the frequency divider 8. The binary digital code that increases in time during the counting of clock pulses at the output of the first counter 9 pulses is converted by the first digital-to-analog converter 11 into the analogue value of the voltage supplied to the second inputs N of the current keys of the first block 17 of the current keys corresponding to this digital code. Therefore, the voltage at the output of the first digital-to-analog converter 11 increases stepwise in time, and with a large number of steps, determined by the resolution of the first counter 9 pulses, this voltage increase in time occurs almost linearly.

 At the same time, the computer 23, for example, according to a deterministic program, on the basis of information entered earlier by the doctor-researcher on the position of the boundaries of the studied field of view, selects a binary digital code for the number of the LEDs installed on screen 3, which ensures the formation of the first visual stimulus presented. This parallel digital code of the number of the LED from the first output of the computer 23 is fed to the input of the first decoder 15, which is decrypted, providing the formation of the voltage level of the logical unit at the output of the first decoder 15, the number of which corresponds to the selected computer 23 binary digital code number of the LED. This voltage of the logic unit level from the specified output of the first decoder 15 will open the corresponding current switch of the first block 17 of the current keys, through which the voltage from the output of the first digital-to-analog converter 11, which increases almost linearly in time, goes to the LED installed on the screen 3, the digital code of which number has arrived from the computer 23 to the first decoder 15. As a result, the indicated LED installed on the screen 3 will emit visible optical radiation, forming a visual stimulus l, with its brightness will increase substantially linearly with time.

 At the moment when the patient sees the first visual stimulus presented by the examined eye 1, he, acting according to the instructions of the doctor-researcher, will translate and fix his gaze on the perceived first visual stimulus.

 At the same time, the infrared radiation source of the eye rotation sensor 19 forms a luminous flux, which either directly through the opening 4 of the screen 3, closed by the sight glass 5, or after preliminary reflection from the spectro-splitting glass 6 falls on the examined eye 1 of the patient. After reflection from the studied eye 1 of the patient, the luminous flux of infrared optical radiation in the same way returns to the eye rotation sensor 19, which converts it into an analog electrical signal.

 In the case of using the above-known devices for measuring eye rotation angles as the eye rotation sensor 19 of the prior art, the eye rotation sensor 19 receives a stream of infrared optical radiation reflected from the cornea of the patient’s examined eye 1, and forms an image on the sensitive surface of its coordinate-sensitive optical radiation receiver corneal flare (corneal reflex), the position of which moves when the patient's eye 1 is rotated due to an eccentric the cornea relative to the eyeball, and converts it into an electrical signal. In this case, the analog-to-digital converter 20 converts the analog electrical signals from the eye rotation sensor 19, which are proportional to the rotation angles of the examined eye 1 of the patient, into digital codes that are entered into the computer 23.

 In the case of using a video camera that is sensitive to optical radiation of the infrared range of the spectrum as an eye rotation sensor 19, as in the case of preliminary centering of the studied eye of a patient 1, the video camera converts infrared optical radiation reflected by the studied eye of a patient 1 into an analog electric signal image of the studied eye of a patient 1 which, after being converted by an analog-to-digital converter 20 into a digital image signal, is input into a computer 23. The computer 23 converts the numbers the output image signal of the patient’s examined eye 1, for example, into a digital image signal with three gradations of brightness and reproduces this tri-gradation image of the studied eye of the patient 1 on the screen of its display to the doctor-researcher. Based on the processing of the digital three-gradation image signal, the computer 23 determines the coordinates of the center of the pupil of the studied eye 1 of the patient, proportional to the angles of rotation.

In both of these cases, after the patient perceives the presented visual stimulus, translates and fixes his gaze on him, the computer 23 determines the changes Δx ₁ and Δy _{1 of the} coordinates of the fixation point of the patient’s gaze when he looks at this first visual stimulus and compares them accordingly with the differences coordinates (x ₁ ⁰ -x ₀ ⁰ ) and (y ₁ ⁰ -y ₀ ⁰ ), where x ₁ ⁰ , y ₁ ⁰ are the coordinates stored in the computer memory 23 of the LED forming the first visual stimulus on screen 3; x ₀ ⁰ , y ₀ ⁰ - stored in the computer memory 23 coordinates of the point of initial fixation of the patient’s gaze. In case of equality of the indicated corresponding values for a given comparison accuracy, the signal from the third output of the computer 23 sets the trigger 21 to a single state, according to the voltage drop at its direct output from the logic zero level to the logic unit level, a parallel digital signal is written to the first register 13 from the first pulse counter 9 the code corresponding to the last count of pulses calculated and, therefore, the brightness of the first visual stimulus at the time of its perception by the patient. Then, the specified parallel digital code from the first register 13 is entered into the computer 23 for registration and subsequent assessment of the threshold value of the brightness contrast sensitivity of the examined eye of the patient 1 at the point of the field of view corresponding to the point of presentation of this first visual stimulus. The signal of the logic zero level from the inverse output of the trigger 21 stops counting pulses by the first counter 9 pulses, the digital code at its output stops increasing and therefore the voltage at the output of the first digital-to-analog converter 11 stops being supplied through one of the N current keys of the first block 17 of the current keys to 3 LED mounted on the screen, reproducing the first visual stimulus. Therefore, the brightness of the LED and, therefore, the visual stimulus presented and perceived by the patient ceases to increase.

 According to the signal of the logical unit level coming from the direct output of trigger 21 to the input of the start of counting of the second counter 10 pulses, the last one begins to count clock pulses from the frequency divider 8. The binary digital code that increases in time during the counting of clock pulses at the output of the second pulse counter 10 is converted by the second digital-to-analog converter 12 into the analog value of the voltage supplied to the second inputs N of the current keys of the second block 18 of the current keys corresponding to this digital code. Therefore, the voltage at the output of the second digital-to-analog Converter 12 increases stepwise in time, and with a large capacity of the second counter 10 pulses, this increase in voltage in time occurs almost linearly.

 At the same time, the computer 23 selects the binary digital code of the number of the LEDs installed on the screen 3, which ensures the formation of the second visual stimulus presented. This parallel digital code of the LED number from the second output of the computer 23 is fed to the input of the second decoder 16, which is decrypted, providing the formation of the voltage level of the logical unit at the output of the second decoder 16, the number of which corresponds to the selected binary number 23 digital digital code of the LED number. This voltage of the logical unit level from the specified output of the second decoder 16 will open the corresponding current switch of the second block 18 of the current keys, through which the voltage from the output of the second digital-to-analog converter 12, which increases almost linearly in time, goes to the LED installed on the screen 3, the digital code of which number has arrived from the computer 23 to the second decoder 16. As a result, the indicated LED installed on the screen 3 will emit visible optical radiation, forming the second visual th stimulus, and its brightness will increase almost linearly in time.

 When the patient sees the presented second visual stimulus by the examined eye 1, he, acting according to the instructions of the doctor-researcher, will translate and fix his gaze on the perceived second visual stimulus.

 Further, similar to what was described for the stage of presenting the first visual stimulus to the patient, the eye rotation sensor 19 together with the analog-to-digital converter 20 provide, depending on the design of the eye rotation sensor 19, input into the computer 23 or digital codes of the angles of rotation of the examined eye 1 patient, or a digital signal of his image.

After the patient perceives the presented second visual stimulus, translates and fixes his gaze on it, the computer 23 determines the changes Δx ₂ and Δy ₂ and the coordinates of the fixation point of the patient’s gaze when he looks at this second visual stimulus and compares them accordingly with the coordinate differences ( x ₂ ⁰ -x ₁ ⁰ ) and (y ₂ ⁰ -y ₁ ⁰ ), where x ₁ ⁰ , y ₁ ⁰ are the coordinates of the LED forming the first visual stimulus stored in the computer 23; x ₂ ⁰ , y ₂ ⁰ - stored in the computer memory 23 coordinates of the LED forming the second visual stimulus. In the case of equality of the indicated corresponding values for a given accuracy of comparison, the signal from the third output of the computer 23 sets the trigger 21 to zero, the voltage drop across the inverse output of which is from the logic zero to the level of the logical unit in the second register 14 from the second counter 10 pulses written in parallel the code corresponding to the number of pulses calculated by the second counter of 10 pulses and, therefore, the brightness of the second visual stimulus at the time of its perception by the patient. Then, the specified parallel digital code from the second register 14 is entered into the computer 23 for registration and subsequent assessment of the threshold value of the brightness contrast sensitivity of the studied eye of 1 patient at a point of the field of view corresponding to the point of presentation of this second visual stimulus.

 The signal of the logic zero level from the direct output of the trigger 21 stops counting pulses by the second counter 10 pulses, the digital code at its output stops increasing and therefore the voltage at the output of the second digital-to-analog converter 12 stops being supplied through one of the N current keys of the second block 18 of the current keys to 3 LED mounted on the screen, reproducing the second visual stimulus. Therefore, the brightness of this LED and. consequently, the second visual stimulus presented and perceived by the patient ceases to increase.

 Now, from the inverted output of trigger 21, the logic unit level voltage again comes to the input of the counting of the first counter 9 pulses, and therefore, the first counter 9 of pulses is reset and then begins to count clock pulses coming from the output of the frequency divider 8. At the same time, the computer 23 selects a binary digital code of the number of the LEDs installed on the screen 3, which ensures the formation of the third visual stimulus presented. This parallel digital code of the number of the LED from the second output of the computer 23 is fed to the input of the first decoder 15, which is decrypted, providing the formation of voltage level of the logical unit at the output of the first decoder 15, the number of which corresponds to the selected computer 23 binary digital code number of the LED that forms the third visual stimulus . Since the binary digital code of the LED number supplied to the first decoder 15 has changed, the presentation of the first visual stimulus to the patient ends. Further, the device likewise ensures the presentation of a third visual stimulus to the patient and registration of his oculomotor reaction during the perception of the third visual stimulus. In this case, the operation of the device at the stage of presentation of each next visual stimulus with an odd number in the order of presentation is similar to the operation of the device at the stage of presentation of the first visual stimulus, and the operation of the device at the stage of presentation of each next visual stimulus with an even number is similar to the operation of the device at the stage presentation of a second visual stimulus.

 Thus, visual stimuli are presented at various points in the entire field of view or only in the studied area, the oculomotor reaction of the patient is recorded upon perception of the presented visual stimuli, and the current brightness values of the presented visual stimuli are recorded at the moments of their perception by the patient.

 If at the stage of presenting one of the visual stimuli, for example, the second or subsequent visual stimuli with an even serial number of their presentation, the threshold value of the brightness contrast sensitivity of the examined eye of 1 patient at the point of view where the indicated visual stimulus is presented is pathologically so high that the patient does not will be able to perceive the visual stimulus presented, and therefore translate and fix on it a look even at its maximum brightness, the eye rotation sensor 19 and E M 23 does not register the oculomotor patient response. Therefore, at the third output of the computer 23, a signal that changes the state of the trigger 21 will not occur, and the second pulse counter 10 will continue to count clock pulses from the frequency divider 8 until it is full, providing an increase in the brightness of the presented visual stimulus to the maximum possible value. At the moment when the brightness of the presented visual stimulus reaches the maximum possible value, the overflow pulse from the output of the second counter 10 pulses through the disjunctor 22 will go to the second input of the computer 23, which will register that at this point of the field of view the brightness contrast sensitivity of the studied eye of 1 patient is below the established permissible values. After that, the computer 23 selects a binary digital code of the number of the LEDs installed on the screen 3, which ensures the formation of the next visual stimulus presented at another point of the field of view. This parallel digital code of the LED number from the second output of the computer 23 is fed to the input of the second decoder 16, and the second pulse counter 10 reset to zero when overflowing will again begin to count clock pulses from the frequency divider 8, which ensures the presentation of the next visual stimulus with increasing brightness at another next point in the field view of the examined eye of 1 patient.

 Similarly, if upon presenting the first or subsequent visual stimuli with an odd serial number of their presentation, the patient does not receive the visual stimulus when the digital code reaches 9 pulses in the first counter and, therefore, the brightness of the visual stimulus presented is the maximum possible value, the overflow pulse of the first counter is 9 pulses through the disjunctor 22 it will go to the second input of the computer 23, which will register that at a given point of the field of view the brightness contrast sensitivity is studied the edible eye of 1 patient is below the set acceptable value. Next, the computer 23 likewise selects the binary digital code of the number of the LEDs installed on the screen 3 and provides using the first counter 9 pulses, the first digital-to-analog converter 11, the first decoder 15 and the first block of current keys 17 the formation of the next visual stimulus presented at another point of the field of view.

As a result of the operation of this device in the study of the field of view in the main memory of the computer 23 for each point of the field of view at which the visual stimulus was presented, two coordinates of this point of the field of view are recorded in the coordinate system, the beginning of which lies in the center of the field of view, and the threshold brightness contrast sensitivity of the studied eye of 1 patient, calculated by the computer 23 on the basis of the recorded brightness of the presented visual stimulus at the time of perception by the patient, or I that the brightness contrast sensitivity 1 patient study eye is below the permissible value. When using the Cartesian coordinate system, the specified coordinates of the i-th point of the field of view at which the i-th visual stimulus was presented are calculated by the computer 23 according to the expressions x _i = x _i ⁰ -x _i-1 ⁰ , y _i = y _i ⁰ -y _i-1 ⁰ , where x _i ⁰ , y _i ⁰ are the coordinates of the LED on screen 3 stored in the computer memory 23, which forms the next i-th visual stimulus presented; x _i-1 ⁰ , y _i-1 ⁰ are the coordinates of the LED on screen 3, which formed the previous (i-1) th visual stimulus, stored in the computer memory 23. In the case of using the polar coordinate system, the specified coordinates of the i-th point of the field of view in which the i-th visual stimulus was presented can be calculated by the computer 23 according to the expressions r _i = ((x _i ⁰ -х _i-1 ⁰ ) ² + ( y _i ⁰ -y _i-1 ⁰ ) ² ) ^1/2 , φ _i = arctan ((y $\genfrac{}{}{0ex}{}{\text{0}}{\text{i}}$ -y $\genfrac{}{}{0ex}{}{\text{0}}{\text{i-1}}$ ) / (x $\genfrac{}{}{0ex}{}{\text{0}}{\text{i}}$ -x $\genfrac{}{}{0ex}{}{\text{0}}{\text{i-1}}$ )).
The listed results of the study are displayed for operational visual analysis to the doctor-researcher on the display screen of the computer 23 using, for example, a degree coordinate grid and various colors corresponding to different values of the threshold brightness contrast sensitivity of the studied eye of the patient 1, and are also printed on the ophthalmic examination card of the patient using printer 23, where, in addition, the coordinates and absolute values of the threshold brightness contrast feel can be indicated the identity of the studied points of view.

 The stated materials confirm the possibility of practical implementation of the proposed method of ophthalmic examination of the visual field.

 Thus, the application of the proposed method of ophthalmic examination of the field of view provides increased accuracy in determining the threshold value of brightness contrast sensitivity and the position of the boundaries of the field of view and its sections with dysfunction of brightness contrast sensitivity, and also simplifies its implementation.

Claims (4)

1. The method of ophthalmological research of the visual field by fixing the patient’s gaze at the fixation point, alternately presenting the patient with a varying brightness of a visual stimulus at different points of the visual field, perceiving the visual stimulus by the patient and determining the brightness threshold of the patient’s visual stimulus perception, characterized in that after each patient’s perception visual stimulus presented in the next point of view, choose the point of fixation of the patient’s gaze at the point of presentation of the patient’s perceived visual stimulus and the fact that the patient perceives the visual stimulus is determined based on the registration of his oculomotor reaction. 2. The method according to claim 1, characterized in that the presentation of the visual stimulus at the next point of the field of view begins to be carried out after selecting the fixation point of the patient’s gaze at the point of presentation of the previous visual stimulus received by the patient. 3. The method according to claim 1, characterized in that the registration of the oculomotor reaction of the patient to determine the fact of perception by him of a visual stimulus is carried out using an eye rotation sensor. 4. The method according to claim 1, characterized in that during registration of the oculomotor reaction of the patient when choosing the next fixation point of the patient’s gaze, the coordinates of the fixation point of the patient’s gaze are determined and compared with the coordinates of the next point of presentation of the visual stimulus relative to the previous point of presentation of the visual stimulus.