Device for performing FDT perimetry

Abstract

The invention relates to the field of ophthalmology and is intended for testing the differential light sensitivity of the retina in different areas of the visual field using FDT perimetry. The present device comprises the following interconnected units: a unit for generating stimuli and establishing a testing procedure; a unit for displaying stimuli; and a feedback unit. The unit for generating stimuli and establishing a testing procedure is configured to be capable of generating stimuli and establishing a topographical model of stimuli which is based on a radial coordinate system, wherein the stimuli are provided in the form of curvilinear trapezoids and one circular central diagnostic stimulus. The stimuli in the form of curvilinear trapezoids are filled with alternating dark and light stripes that are arcs of concentric circles, the centre of which lies at the middle of the radial coordinate system used. The result of the invention is an increase in the reliability of testing of the differential light sensitivity of the retina of the eye using FDT perimetry, and an increase in the accuracy of detection of potential central visual field defects caused by depression of the light sensitivity of the retina.

Description

[0001] FDT PERIMETRY DEVICE

[0002] Field of technology to which the invention relates

[0003] The invention relates to the field of medicine (in particular, but not only, ophthalmology), as well as for determining professional suitability, in particular, but not only, sports, driving vehicles and complex systems, etc. and is intended for conducting a study of differential light sensitivity of the retina in different areas of the visual field, using the FDT perimetry (Frequency Doubling Technology Perimetry) method.

[0004] State of the art

[0005] The ability of the eye to distinguish light and fix objects of different brightness under a certain background illumination is called differential light sensitivity. One of the most common methods for studying the differential light sensitivity of the retina at different points within the visual field is perimetry. The results obtained during perimetry are of great importance in diagnosing various diseases, in particular glaucoma. It is known that in glaucoma, early changes more often occur in the central zone of the visual field [Erichev V.P., Antonov A.A., Vitkov A.A., Grigoryan L.A. Static perimetry in the diagnosis of glaucoma. Part 1. Basic principles. Bulletin of ophthalmology. 2021 ;137(5):281-288. https: / / doi.org / 10.17116 / oftalma2021137052281]. This is due to the uneven distribution of ganglion cells in the retina.The central zone contains approximately 66% of the ganglion cells and receives 83% of all information entering the visual area of ​​the brain.

[0006] FDT-perimetry (Frequency Doubling Technology Perimetry) is a non-standard perimetry method that uses a specific stimulus in the form of vertical and horizontal alternating dark and light stripes with a given spatial frequency to assess the visual field function, the brightness of which smoothly changes along the axis according to a sinusoidal law and the phase of which changes to the opposite with a given temporal frequency. Unlike the stimuli of other perimetry methods, the FDT-perimetry stimulus is based on the visual illusion of doubling a low spatial frequency, which occurs in humans normally, but is disrupted at the very beginning of the development of a certain pathology of the visual organ, which allows, due to the higher sensitivity of the method, to detect defects in the central visual field earlier. The concept of stimulus topography in FDT-perimetry tests refers to the distribution and characteristics of the stimuli used in this method of studying the visual field.

[0007] The FDT-perimeter (Frequency Doubling Technology Perimeter) "Humphrey FDT Model 710" is known from the state of the art [https: / / www.digitaleyecenter.com / wp-content / uploads / 2015 / 11 / fdt-710-user-manual.pdf]. The device is a stationary hardware and software complex designed to study the differential light sensitivity of the eye using the FTD-perimetry method. Visualization of stimuli occurs on a screen located in the stationary housing of the device. Also known from the prior art are solutions in which the visualization of stimuli occurs on a screen located in a head-mounted device body, for example, the FDT perimeter (Frequency Doubling Technology Perimeter) PALMSCAN VF2000 NEO from MicroMedicalDevices [https: / / micromedinc.com / vf2000-neo / ] or the FDT (Frequency Doubling Technology) perimeter MVP FDT, developed at the Bascom Palmer Eye Institute [https: / / pubmed.ncbi.nlm.nih.gov / 31530566 / ].

[0008] The disadvantage of these and similar devices is the uneven study of differential light sensitivity of the retina in different areas of the visual field. This disadvantage occurs due to the fact that the tested ganglion cells are unevenly distributed on the retina. The density of these cells increases significantly towards the center. In addition, their density in the nasal area is greater than in the temporal area. At the same time, the area of ​​the simultaneously tested areas is always the same due to the same area of ​​stimuli. Thus, in each studied segment (square) there is a different number of tested ganglion cells, which can lead to a decrease in the parameter "sensitivity" of the study during screening and insufficiently high accuracy of determining the differential light sensitivity of the retina during a threshold study.Numerous publications show that when conducting a study of differential light sensitivity of the retina using the standard (white stimulus on a white background) perimetry method, it is possible to record disturbances only when at least a certain percentage (25-35%) of retinal ganglion cells die. FDT perimetry, due to its higher stimulus sensitivity, reveals the death of retinal ganglion cells much earlier, but its stimulus has the disadvantage described above. Thus, when a certain number of cells die, this percentage can be reached and detected in the peripheral (or temporal) areas, where the cell density is lower, and, consequently, the percentage of dead cells is higher with their equal number, and is not reached, and, consequently, is not detected closer to the center of the retina (or in the nasal area), where the ganglion cell density is higher, and, consequently, the percentage of dead cells is lower with their equal number.

[0009] In all currently existing FDT perimeters, the test topography is based on the Cartesian (orthogonal) coordinate system. The diagnostic stimuli are shaped as squares of the same size. Additionally, there is an optional central stimulus in the form of a circle. All stimuli except the central one are of the same size. Most often, 10x10 angular degrees (16 stimuli, 4x4) or 5x5 angular degrees (64 stimuli, 8x8) and are located close to each other. Thus, the examined central visual field has the shape of a square measuring 40x40 angular degrees with the center in the middle, coinciding with the center of the macula of the retina. The principle of constructing the topography of the study is that each stimulus allows you to examine a segment of the retina identical in size and shape in the form of a square measuring 10x10 angular degrees or 5x5 angular degrees. But at the same time, each stimulus has a different and multidirectional distance from the center of the retina.

[0010] Disclosure of the essence of the invention

[0011] The technical task is to create an FDT perimeter device with an original topographic model of stimuli based on a radial (polar) coordinate system, designed in such a way that each stimulus allows one to study a region of the retina containing approximately the same number of ganglion cells being studied, which allows one to detect with equal probability disturbances in the differential light sensitivity of the retina in each segment being studied with the death of an almost equal number of ganglion cells, which in turn increases the reliability of the study of differential light sensitivity of the retina using the FDT perimetry method.

[0012] The technical result consists in increasing the reliability of the study of differential light sensitivity of the retina of the eye using the FDT perimetry (Frequency Doubling Technology Perimetry) method, increasing the accuracy of detecting defects in the central field of vision that arise due to depression of the light sensitivity of the retina.

[0013] The technical result is achieved due to the fact that the FDT perimeter with a topographic model of stimuli based on a radial (polar) coordinate system contains a stimulus generation and test procedure formation unit, a stimulus visualization unit and a feedback unit, interconnected with each other, wherein the stimulus generation and test procedure formation unit is designed with the possibility of generating diagnostic stimuli and forming a topographic model of diagnostic stimuli based on a radial (polar) coordinate system, wherein the diagnostic stimuli are made in the form of curvilinear trapezoids, and one round central diagnostic stimulus, wherein the diagnostic stimuli made in the form of curvilinear trapezoids are filled with alternating dark and light stripes, which are arcs of concentric circles with a center in the middle of the radial (polar) coordinate system used.

[0014] In addition, the stimulus strips are designed with the ability to smoothly change brightness according to a sinusoidal law in the direction of vectors that have an origin in the center of the coordinate system and pass through the middle of the stimuli.

[0015] In addition, the stimulus strips are designed with the ability to change the phase of the alternation of the strips to the opposite one with the required time frequency.

[0016] In addition, the area of ​​the stimuli, which have the shape of curvilinear trapezoids, is made to increase as they move away from the center of the retina.

[0017] In addition, the area of ​​stimuli in the form of curvilinear trapezoids can be made to decrease in the nasal region.

[0018] In addition, additional stimuli may be introduced into the nasal area.

[0019] In addition, the number of stripes in the stimuli, which have the shape of curvilinear trapezoids, is made the same.

[0020] In addition, the FDT perimeter additionally contains a block for monitoring the execution of the study, which can be performed either in a single block with the block for generating stimuli and forming the test procedure, or separately.

[0021] In addition, the FDT perimeter additionally contains a block for analyzing the obtained results and forming the probability of a diagnosis, implemented both in a single block with a block for generating stimuli and forming a test procedure or with a block for monitoring the execution of the study, and separately.

[0022] In addition, the feedback unit is designed as a button that provides a yes / no response from the subject, or as a joystick that controls the response in the form of movement in space, or as a neurointerface that controls the change in signals in the channels of visual analyzers, or as a device that analyzes visual reactions.

[0023] In addition, the blocks are connected to each other by wired communication and / or by using wireless information transmission technology.

[0024] In addition, wireless information transmission technology is implemented through, but not limited to, Wi-Fi, Bluetooth, loT.

[0025] In addition, the FDT perimeter is designed as a stationary device, as well as with the ability to be placed on the head, in the form of a virtual reality helmet or augmented or mixed reality glasses. Brief description of the drawings

[0026] The details, features, and advantages of the present invention follow from the following description of the claimed technical solution using the drawings, which show:

[0027] Fig. 1 - Block diagram of the device. The dotted line indicates optional blocks;

[0028] Fig. 2 - Density of ganglion cells depending on their distance from the center of the retina. Data obtained from the source - Christine A. Curcio et al. [Human Photoreceptor Topography],

[0029] Fig.3 - Stimulus topography based on the Cartesian (orthogonal) coordinate system, using the perimeter of the Humphrey FDT Model 710 as an example.

[0030] Fig. 4 - FDT perimetry stimulus topographies known from the art based on the Cartesian (rectangular) coordinate system. The squares are 10x10 or 5x5 angular degrees. Additional squares in the nasal region are shown.

[0031] Fig. 5 - Cell density curve used to calculate the area of ​​the curvilinear trapezoidal stimuli. Data for plotting the curve were obtained from Table 1 of Sjostrand, J., Olsson, V., Popovic, Z., & Conradi, N. (1999). Quantitative estimations of foveal and extra-foveal retinal circuitry in humans. Vision Research, 39(18), 2987-2998. doi:10.1016 / s0042-6989(99)00030-9.

[0032] The diagram shows the fourth-degree trend line polynomial y=f(x) used in the calculations and its reliability value R.

[0033] Fig. 6 - The number of ganglion cells in each square (stimulus) depending on its location relative to the center (macula) of the retina in the topography of FDT perimetry stimuli based on the Cartesian (rectangular) coordinate system. The square sizes are 10x10 angular degrees. Such uneven distribution of ganglion cells can lead to a decrease in the "sensitivity" parameter of the study during screening and insufficiently high accuracy in determining the loss of differential light sensitivity of the retina during a threshold study.

[0034] Fig. 7 - The number of ganglion cells in each square (stimulus) depending on its location relative to the center of the retina in the topography of FDT perimetry stimuli based on the Cartesian (rectangular) coordinate system with a central round stimulus. The squares are 10x10 angular degrees, the diameter of the central stimulus is 8 degrees. The uneven distribution of ganglion cells inside the grid is less than in the previous case, but not by much, the problem is not solved.

[0035] Fig. 8 - The number of ganglion cells in each sector (stimulus) depending on its location relative to the center of the retina in the topography of FDT perimetry stimuli based on the proposed radial grid (coordinate system) without correction of the nasal regions. It is evident that in all sectors (stimuli) the number of ganglion cells is the same with the exception of the nasal regions.

[0036] Fig. 9 - The number of ganglion cells in each sector (stimulus) depending on its location relative to the center of the retina in the topography of FDT perimetry stimuli based on a radial grid (coordinate system) with correction for nasal areas. It is evident that the number of ganglion cells is the same in all sectors (stimuli), including the nasal areas. Two additional stimuli for studying the nasal areas are shown.

[0037] Fig. 10 - Example of the structure of a radial stimulus. Stimuli in the form of curvilinear trapezoids are filled with alternating dark and light stripes, which are fragments of arcs of concentric circles with a center in the middle of the used system of angular coordinates. The brightness of the stripes changes smoothly according to a sinusoidal law in the direction of the vectors, having an origin in the center of the coordinate system and passing through the middle of the stimuli (the sinusoidal change in brightness is not shown in the figure) with the possibility of changing the phase to the opposite with the required time frequency. In this way, the problem of the diversity of perception of stimuli is eliminated, all stimuli are uniform for perception.

[0038] The following positions are indicated by numbers on the figures:

[0039] Pos. 1 - block for generating stimuli and forming the test algorithm;

[0040] Pos. 2 - stimulus visualization block;

[0041] Pos. 3 - feedback block;

[0042] Pos. 4 - control unit for the execution of the study;

[0043] Pos. 5 - block for analyzing the obtained results and forming the probability of diagnosis;

[0044] Pos. 6 - density of ganglion cells in the nasal and temporal regions at a distance of less than 1 mm;

[0045] Pos. 7 - density of ganglion cells in the nasal and temporal regions at a distance of less than 20 mm (from the graph it is clear that the density in the nasal region is higher);

[0046] Pos. 8 - density of ganglion cells in the superior and inferior regions at a distance of less than 1 mm;

[0047] Pos. 9 - density of ganglion cells in the superior and inferior regions at a distance of less than 20 mm;

[0048] Pos.10 - a grid of 16 cells (4x4) with a size of 10x10 angular degrees on the device screen. The cell with the active stimulus is colored black;

[0049] Pos.11 - a grid of 16 cells (4x4) with a size of 10x10 angular degrees in the test results report;

[0050] Pos.12 - visualization of some stimuli on the grid above; Pos.13 - segment for a stimulus with a grid of 16 cells (4x4) with a size of 10x10 angular degrees;

[0051] Pos.14 - segment for a stimulus with a grid of 64 cells (8x8) measuring 5x5 angular degrees;

[0052] Pos.15 - additional stimuli in the nasal zone;

[0053] Pos. 16 - stimuli located in the nasal zone, with a 42% increased density of ganglion cells;

[0054] Pos.17 - additional round-shaped stimuli in the central zone;

[0055] Pos. 18 - stimuli located in the nasal zone, the area of ​​which is corrected by reducing the height of the curvilinear trapezoids in the direction of the radius vectors in such a way as to equalize the number of ganglion cells located in them;

[0056] Pos. 19 - stimuli in the form of curvilinear trapezoids are filled with alternating dark and light stripes, which are arcs of concentric circles with a center in the middle of the used system of angular coordinates. The brightness of the stripes changes smoothly according to a sinusoidal law in the direction of the vectors, having their origin in the center of the coordinate system and passing through the middle of the stimuli (the sinusoidality of the change in brightness is not shown in the figure);

[0057] Pos. 20 - the spatial frequency of stimuli, as their location moves away from the center of the retina, decreases in such a way that the same number of dark and light stripes are preserved in the stimulus field.

[0058] Implementation of the invention

[0059] The claimed device is designed to perform FDT perimetry with the topography of diagnostic stimuli based on the radial (polar) coordinate system. Regardless of the design features (stationary or mobile), the device is a hardware and software complex capable of performing a full set of actions necessary to determine the differential light sensitivity of the retina and detect defects in the central field of vision that occur due to depression of the retinal light sensitivity. Or, in other words, a hardware and software complex capable of performing a full set of actions that fit the definition of "FDT perimetry". In addition, if necessary (but not necessarily), based on the results of the studies, the device is capable of determining, based on the embedded algorithms or a specially trained machine learning (ML) or artificial intelligence (AI) system, the probability of the presence of a particular disease and / or its stage.The device consists of a stimulus generation and test procedure formation unit, a stimulus visualization unit, and a feedback unit. Additionally, there may be a study execution control unit and a unit for analyzing the obtained results and forming the probability of diagnosis.

[0060] As stated earlier, unlike the known solutions, the claimed device is capable of generating stimuli for conducting FDT perimetry using a topographic model of stimuli based on a radial (polar) coordinate system. In this case, the stimuli have the form of curvilinear trapezoids, the area of ​​which increases as they move away from the center of the retina. At the same time, the area of ​​the said stimuli can be made decreasing in the nasal region. Additional stimuli can be introduced in the nasal region. In addition, a new, original structure of the stimuli themselves is proposed for the new topography.

[0061] The topography of stimuli in FDT perimetry includes the following characteristics:

[0062] 1. Spatial frequency: the frequency of distribution of vertical or horizontal alternating dark and light stripes (grids), the brightness of which smoothly changes along the axis according to a sinusoidal law, the step of which is usually 0.25 - 0.5 degrees.

[0063] 2. Temporal frequency: FDT perimetry stimuli consist of continuously changing antiphase gratings and have a specific refresh rate, which is typically greater than 25-30 Hz.

[0064] 3. Size and shape: FDT perimetry stimuli at this level of technology are usually squares, which can be of different sizes, most often 10x10 angular degrees or 5x5 angular degrees. The size of the stimuli can vary depending on the area of ​​the visual field being examined.

[0065] 4. Brightness (contrast): FDT perimetry stimuli have different brightness (contrast), which allows assessing the sensitivity of the visual field in different areas. The brightness (contrast) of the stimuli can be adjusted according to the needs of the study.

[0066] 5. Arrangement: FDT perimetry stimuli are arranged on a special grid or matrix that allows the examination of the desired area of ​​the central visual field. The arrangement of the stimuli can be adapted to the specific needs of the study. FDT perimetry stimuli at this level of technology are usually arranged in the cells of a rectangular grid with equal cell sizes.

[0067] The essence of the proposed solution for the topography of FDT perimetry stimuli concerns, among other things, such parameters as size, shape and location and is based on the results of two known types of studies: 1. The studied ganglion cells are located unevenly on the retina. The density of these cells increases significantly towards the center. In addition, their density in the nasal region is greater than in the temporal region (Fig. 2);

[0068] 2. When conducting a study of differential light sensitivity of the retina using the perimetry method, it is possible to record disturbances in the central visual field only when at least a certain percentage (or share) of the cells being studied perish. In other words, it is not the number of dead cells that matters, but their percentage (or share) relative to those being studied at the given moment using one stimulus.

[0069] In addition, for the new topography, a new, original structure of the stimuli themselves is proposed in the form of fragments of arcs of concentric circles with the possibility of changing the phase to the opposite with the required time frequency.

[0070] Let's take a closer look.

[0071] The first type of research is counting the number of ganglion cells in different areas of the retina. In 1990, Christine A. Curcio et al. published an article [Human Photoreceptor Topography], and in 1999, Johan Sjostrand et al. published an article [Quantitative estimations of foveal and extra-foveal retinal circuitry in humans], in which they provide figures and visual graphs showing an increase in the density of ganglion cells as they approach the center of the retina. According to the published data, at a distance of 2 degrees from the center of the retina, the density of ganglion cells is 16 times greater than at a distance of 20 degrees. It is also shown that in the nasal region, the density of ganglion cells is 42% higher than in the temporal region. Similar results have been published based on the results of a number of other studies [Curcio CA, Allen KA. Topography of ganglion cells in human retina. The Journal of Comparative Neurology. 1990;300(1):5-25. https: / / doi.orq / 10.1002 / cne.903000103].

[0072] The second type of research provides an understanding that when conducting a study of differential light sensitivity of the retina using the perimetry method, it is possible to record disturbances only when at least a certain percentage of the cells being studied perish. It is generally accepted that perimetric studies with a white stimulus on a white background allow one to record disturbances when more than 25-35% of the retinal ganglion cells perish. In other words, it is not the number of dead cells that matters, but their percentage (or share) relative to those being studied in a given place using one stimulus.Thus, when a certain number of cells die, this percentage (share) can be achieved and detected in the peripheral (or temporal) region, where the density of ganglion cells is lower, and not achieved, and therefore not detected, closer to the center of the retina (or in the nasal region), where the density of ganglion cells is higher, and, therefore, the percentage of dead cells is lower with an equal number of them.

[0073] The combined effect of these two facts leads to an important drawback of the traditional FDT perimetry stimulus topography - uneven study of differential light sensitivity of the retina in different areas of the visual field. Traditional FDT perimetry topography involves the use of a topographic model of stimuli based on the Cartesian (orthogonal) coordinate system. The studied area is divided into squares of equal size. Most often, the squares are 10x10 or 5x5 angular degrees. The stimuli are shown on the same topographic grid and have a shape and size equal to the shape and size of the squares. Accordingly, the stimulus sizes are also 10x10 or 5x5 angular degrees. The number of stimuli in the test depends on their size. With a stimulus size of 10x10 angular degrees, there are usually 16 stimuli (4x4 square grid). With a stimulus size of 5x5 angular degrees, there are usually 64 stimuli (8x8 square grid).

[0074] Since, when using the topographic model of stimuli based on the Cartesian (orthogonal) coordinate system, all squares (stimuli) of one test have the same area (100 or 25 sq. angular degrees, depending on the stimulus size), each square (stimulus) contains a different number of examined cells, depending on its location relative to the center of the retina, which, as was said above, can lead to a decrease in the “sensitivity” parameter of the study during screening and insufficiently high accuracy of determining the loss of differential light sensitivity of the retina during a threshold study. Thus, in a 4x4 test, cells measuring 10x10 angular degrees in each of the four central squares (stimuli) contain approximately 141,000 cells, the upper, lower and temporal squares contain 31,000 cells, the corner squares contain 29,000 cells, and the nasal squares contain 46,000 cells (Figs. 6 and 7).Accordingly, a perimetric test capable of recording the death of more than 25-35% of cells will give a result when more than 35,000-49,500 cells die in the central squares; when more than 8,000-11,000 cells die in the upper, lower and temporal squares; when more than 7,000-10,000 cells die in the corner squares; when more than 11,500-16,000 cells die in the nasal squares.

[0075] The given example clearly demonstrates the main drawback of the traditional FDT perimetry stimulus topography based on the Cartesian (orthogonal) coordinate system - uneven study of the differential light sensitivity of the retina in different zones of the central visual field.

[0076] To eliminate this drawback, it is proposed to use a radial (polar) coordinate system instead of the Cartesian (orthogonal) coordinate system to construct the topography of FDT perimetry stimuli. The baselines of such a system consist of radius vectors originating in the center of the retina and concentric circles with a common center also in the center of the retina. The areas formed as a result of the intersection of these baselines are curvilinear trapezoids, the area of ​​which increases with distance from the center. Accordingly, it is possible to select such parameters of the baselines (radii and circles) that with distance from the center of the retina, the increase in the area of ​​the sectors compensates for the decrease in the density of the studied (in this case, ganglion) cells. With complete compensation, the number of studied cells in each sector (stimulus) will be the same (Fig. 8).This in turn will make the study of differential light sensitivity of the retina in different areas of the visual field uniform and will eliminate the above-mentioned disadvantage inherent in traditional topography. The exception will be the central sector of a circular shape. This is due to the fact that the density of the ganglion cells in the center is so high that its compensation will require a stimulus of such a small size that significant errors will arise during the study due to involuntary eye movement. An example of such a grid based on the radial (polar) coordinate system is shown in Fig. 8. It is evident that due to the increase in the area of ​​the segments with distance from the center of the retina, the number of ganglion cells located in each sector is the same. The exception is the segments located in the nasal region (Pos. 16), in which a greater number of these cells are located.

[0077] To compensate for the denser location of ganglion cells in the nasal region, two methods can be used:

[0078] 1. The radius vectors are distributed unevenly around the circumference, that is, more densely in the nasal region;

[0079] 2. in the nasal region the height of the curvilinear trapezoids decreases in the direction of the radius vectors (Fig. 9).

[0080] Fig. 9 shows the second variant. Such a technique allows creating multiple stimulus topographies for FDT perimetry depending on the tasks set by the researchers.

[0081] This patent shows a 17-stimuli topography (16 radial trapezoid stimuli plus a circular central stimulus) (Fig. 9). It is intended to replace the traditional 4x4 square array plus a circular central stimulus.

[0082] The given topography is only an example of the use of the proposed topographic model for FDT perimetry based on the radial (polar) coordinate system, and does not exhaust the possibilities of this model.

[0083] The change in the form of stimuli also required a revision of their structure. In the traditional Cartesian system, stimuli have the form of squares and a structure in the form of vertical or horizontal alternating dark and light stripes, the brightness of which smoothly changes along the axis according to a sinusoidal law (Pos. 12) with the possibility of changing the phase to the opposite with the required time frequency. The use of such a structure of stimuli in the proposed "radial" topography will lead to their non-uniform perception due to the fact that most of the stimuli are at different angles to the horizontal and vertical. For this reason, filling the stimuli with horizontal or vertical stripes will be perceived by the subjects as a variety of figures and can lead to a distortion of the study result.

[0084] To eliminate this effect, a new original structure of radial stimuli was developed (Fig. 9). Stimuli in the form of curvilinear trapezoids are filled with alternating dark and light stripes with a given spatial frequency, which are fragments of arcs of concentric circles with a center in the middle of the used system of angular coordinates. The brightness of the stripes smoothly changes according to a sinusoidal law in the direction of the vectors, having an origin in the center of the coordinate system and passing through the middle of the stimuli with the possibility of changing the phase to the opposite with the required temporal frequency. In this way, the problem of the diversity of perception of stimuli is eliminated, all stimuli are uniform for perception (Fig. 10, Pos. 19 and Pos. 20).

[0085] When implementing such a system, it is necessary to take into account the change in the linear dimensions of the stimuli. As the distance from the center increases, the length of the stimuli in the direction of the radius vectors increases. In order to obtain an identical visual illusion of doubling the spatial frequency, the number of bands in the stimuli must be the same. For this reason, as the stimulus moves away from the center, the spatial frequency of the grating must decrease proportionally to the increase in its length (Fig. 10, Item 20).

[0086] To implement the stimulus generation procedure for conducting FDT perimetry with a topographic stimulus model based on a radial (polar) coordinate system, the following FDT perimeter elements were used:

[0087] • block for generating stimuli and forming the test procedure;

[0088] • stimulus visualization unit;

[0089] • feedback block.

[0090] Additionally, the following may be present:

[0091] • control unit for the implementation of the study;

[0092] • block for analyzing the obtained results and forming the probability of diagnosis.

[0093] The stimulus generation and test procedure formation unit is designed with the ability to provide stimulus generation and formation of a research algorithm in accordance with the selected FDT perimetry strategy, using a topographic stimulus model based on a radial (polar) coordinate system.

[0094] The stimulus visualization unit is designed to provide visualization of stimuli generated by the stimulus generation unit and test procedure generation unit on a stationary monitor or screen, or, but not limited to, on monitors or screens of a head-mounted device.

[0095] The device can be placed on the head and can be implemented, but not limited to, in the form of a virtual reality helmet or augmented or mixed reality glasses. The feedback unit is implemented with the ability to provide information about the moment when the patient saw the generated stimulus. The feedback unit can be implemented in the form of a button providing a yes / no response, or in the form of a joystick controlling the response in the form of movement in space, or in the form of a neurointerface controlling the change of signals in the channels of the visual analyzers of the brain, or in the form of a device analyzing visual reactions. The feedback unit can be located in the patient's hands or another part of the patient's body or on the patient's head.

[0096] The combined use of these units enables FDT perimetry with topography of diagnostic stimuli based on a radial (polar) coordinate system.

[0097] The block for monitoring the execution of the study can be implemented either in a single block with the block for generating stimuli and forming the test procedure, or separately. Using the block for monitoring the execution of the study allows the researcher to monitor the course of the study and, if necessary, make the necessary adjustments.

[0098] The block of analysis of the obtained results and formation of the probability of diagnosis can be performed either in a single block with the block of stimulus generation and formation of the test procedure, or with the block of control over the execution of the study, or separately. Using the block of analysis of the obtained results and formation of the probability of diagnosis allows after the end of the study to obtain an independent "third opinion" on the probability of the presence of a particular diagnosis or its stage.

[0099] Communication between all units is accomplished via wired communication and / or by using wireless information transmission technology.

[0100] Wireless information transmission technology is implemented through, but not limited to, Wi-Fi, Bluetooth, loT.

[0101] In the particular case of implementation of the declared technical solution, the patient and the researcher may be one and the same person.

[0102] Fig. 1 shows a block diagram of the device, which shows a block for generating stimuli and forming the test procedure (Pos. 1), a block for visualizing stimuli (Pos. 2), a feedback block (Pos. 3), and an additional block for monitoring the execution of the study (Pos. 4) and a block for analyzing the obtained results and forming the probability of a diagnosis (Pos. 5).

[0103] Fig. 2 shows the density of ganglion cells as a function of their distance from the center of the retina to the source - Christine A. Curcio et al. Human Photoreceptor Topography.

[0104] Fig. 3 shows the grid and stimuli of the prior art FDT perimeter "Humphrey FDT Model 710" [https: / / www.digitaleyecenter.com / wp-content / uploads / 2015 / 11 / fdt-710-user-manual.pdf]. In Fig. 4, Pos. 13 is a 16-cell (4x4) stimuli grid of 10x10 angular degrees on the screen of this device (the cell with the active stimulus is colored black); Pos. 14 is a 16-cell (4x4) stimuli grid of 10x10 angular degrees in the test results report; Pos. 12 in Fig. 3 is a visualization of some stimuli on the above grid.

[0105] Fig. 4 shows the currently known stimulus topographies of FDT perimetry. In the solutions known from the prior art, the test topography is based on a Cartesian (orthogonal) coordinate system. The diagnostic stimuli have the form of squares of the same size. Additionally, there is an optional central stimulus in the form of a circle. All stimuli except the central one have the same size, usually 10x10 angular degrees (16 stimuli, 4x4) (Pos. 13) or 5x5 angular degrees (64 stimuli, 8x8) (Pos. 14) and are located close to each other. Thus, the examined central visual field has the form of a square of 40x40 angular degrees with the center in the middle of the retina. Often, for a more detailed examination of the nasal areas, additional stimuli are added in these areas (Pos. 15).

[0106] Figure 5 shows the curve of the change in the density of the ganglion cells used in the calculations of the area of ​​the stimuli in the form of curvilinear trapezoids. The data for constructing the curve were obtained from Table 1 of the source - Sjostrand, J., Olsson, V., Popovic, Z., & Conradi, N. (1999). Quantitative estimations of foveal and extra-foveal retinal circuitry in humans. Vision Research, 39(18), 2987-2998. doi:10.1016 / s0042-6989(99)00030-9. The diagram shows the fourth-degree trend line polynomial y=f(x) used in the calculations and the value of its reliability R.

[0107] The principle of constructing the currently known from the state of the art research topography based on the Cartesian (orthogonal) coordinate system is that each stimulus allows to study the light sensitivity of an identical in size and shape segment of the retina in the form of a square measuring 10x10 angular degrees or 5x5 angular degrees. But at the same time, each stimulus has a different and multidirectional distance from the center of the retina.

[0108] The disadvantage of this solution is the uneven study of differential light sensitivity of the retina in different areas of the central visual field. This disadvantage is a consequence of the fact that the studied ganglion cells are unevenly distributed on the retina. The density of these cells increases significantly towards the center. In addition, their density in the nasal region is greater than in the temporal region. This unevenness is illustrated in Fig. 2, which clearly shows the change in the density of the ganglion cells with a change in the distance from the center of the retina. Item 6 - in the nasal and temporal regions at a distance of less than 1 mm; Item 7 - in the nasal and temporal regions at a distance of less than 20 mm (it is clear from the graph that their density in the nasal region is higher); Item 8 - in the superior and inferior (interior) regions at a distance of less than 1 mm; Pos. 9 - in the upper (superior) and lower (interior) areas at a distance of less than 20 mm;

[0109] Thus, it is obvious that each segment (square) under study contains a different number of ganglion cells, which may lead to a decrease in the parameter "sensitivity" of the study during screening and insufficiently high accuracy of determining the differential light sensitivity of the retina during a threshold study. Numerous publications show that when conducting a study of differential light sensitivity of the retina by the perimetry method, it is possible to record violations only when at least a certain percentage of the cells under study die.Thus, when a certain number of ganglion cells die, this percentage can be reached and detected in the peripheral (or temporal) areas, where the density of ganglion cells is lower, and, consequently, the percentage of dead cells is higher with an equal number of them, and not reached, and, consequently, not detected closer to the center of the retina (or in the nasal area), where the density of these cells is higher, and, consequently, the percentage of dead cells is lower with an equal number of them.

[0110] The topography of the stimuli in FDT perimetry is an important aspect of this research method, since it allows obtaining information on the differential light sensitivity of the retina and detecting possible defects or changes in the central visual field arising due to depression of retinal light sensitivity.

[0111] The above-described claimed FDT perimeter solution, containing the said blocks, designed with the ability to generate an original topographic model of stimuli based on a radial (polar) coordinate system and planned in such a way that each stimulus allows for the study of an area of ​​the retina containing approximately the same number of cells being studied, allows for the detection of disturbances in the differential light sensitivity of the retina in each segment being studied with the same high probability when the same number of cells being studied die, which in turn increases the reliability of the study of the differential light sensitivity of the retina by the FDT perimetry method.

Claims

CLAUSE OF INVENTION 1. An FDT perimeter with a topographic model of stimuli based on a radial polar coordinate system, characterized in that it contains a stimulus generation and test procedure formation unit, a stimulus visualization unit, and a feedback unit, interconnected with each other, wherein the stimulus generation and test procedure formation unit is configured to generate diagnostic stimuli and form a topographic model of diagnostic stimuli based on a radial polar coordinate system, wherein the diagnostic stimuli are made in the form of curvilinear trapezoids, and one round central diagnostic stimulus, wherein the diagnostic stimuli made in the form of curvilinear trapezoids are filled with alternating dark and light stripes, which are fragments of arcs of concentric circles with a center in the middle of the radial polar coordinate system used.

2. An FDT perimeter according to claim 1, characterized in that the stimulus strips are designed with the possibility of a smooth change in intensity according to a sinusoidal law in the direction of vectors having an origin in the center of the coordinate system and passing through the middle of the stimuli.

3. The FDT perimeter according to item 1, characterized in that the area of the stimuli, having the shape of curvilinear trapezoids, is made to increase as they move away from the center of the retina.

4. The FDT perimeter according to item 1, characterized in that the area of the stimuli, having the shape of curvilinear trapezoids, is made to decrease in the nasal region.

5. The FDT perimeter according to item 1, characterized in that stimuli are additionally performed in the nasal region.

6. The FDT perimeter according to item 1, characterized in that the number of stripes in the stimuli is made the same.

7. The FDT perimeter according to item 2, characterized in that the strips are designed with the possibility of changing the phase to the opposite one with the required time frequency.

8. The FDT perimeter according to item 1, characterized in that it additionally contains a block for monitoring the execution of the study, which is implemented both in a single block with the block for generating stimuli and forming the test procedure, and separately.

9. The FDT perimeter according to item 1, characterized in that it additionally contains a block for analyzing the obtained results and generating the probability of a diagnosis, which is performed either in a single block with a block for generating stimuli and generating a test procedure or with a block for monitoring the execution of the study, or separately.

10. The FDT perimeter according to item 1, characterized in that the feedback unit is designed in the form of a button that provides a yes / no response from the test subject, or in the form of a joystick, controlling the reaction in the form of movement in space, or in the form of a neurointerface that controls the change of signals in the channels of visual analyzers, or in the form of a device that analyzes visual reactions.

11. The FDT perimeter according to item 1, characterized in that the blocks are connected to each other by means of a wired connection and / or by using wireless information transmission technology.

12. The FDT perimeter according to item 8, characterized in that the wireless information transmission technology is implemented by means of, but not limited to, Wi-Fi, Bluetooth, loT.

13. The FDT perimeter according to item 1, characterized in that it is designed both stationary and with the possibility of being placed on the head, in the form of a virtual reality helmet or augmented or mixed reality glasses.

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