RU2291661C1 - Device for measuring lability of vision system of patient - Google Patents

Abstract

FIELD: medical equipment.

SUBSTANCE: device has nanosecond pulse oscillator, generator, first single-pulse vibrator, second single-pulse vibrator with controlled pulse duration, third and fourth single-pulse vibrators, OR gate, first and second AND gates, scale-of-ten circuit, scale-of-thousand circuit, programmed divider, first and second flip-flops, first and second counters, register, point light source, indication unit and control board.

EFFECT: improved truth of measurement.

4 dwg

Description

The invention relates to medical equipment and is intended to determine the lability of the human visual system.

According to N.E. Vvedensky, the measure of lability is the maximum frequency of reactions that tissue can reproduce in exact accordance with the rhythm of the applied irritations [1]. The lability value is determined by the critical fusion frequency of flickering phosphene [2], the critical flicker frequency [3,4] and the critical frequency of sound clicks [5].

The well-known device is "Fosphen" - an electronic digital device for studying the lability of nervous processes at the critical fusion frequency of flickering phosphene, the critical frequency of light flicker and the critical frequency of sound clicks [5].

Known neurochronometer [5], DPPI apparatus [6] and IRIS device [7] for studying the properties of the nervous system, including lability at the critical frequency of light flicker.

A disadvantage of the known technical means is an unreliable determination of the true value of lability, since during rhythmic stimulation, the continuous activation of a neuron, which is a structural-morphological functional unit of the brain [8], is observed only at frequencies of no more than 13-15 Hz [9].

Closest to the technical nature of the present invention is a device for determining the lability of the human visual system, containing a control panel and a point source of light [10].

The disadvantage of this device is the inaccurate determination of the value of the lability of the human visual system.

The inventive device improves the reliability of determining the lability of the human visual system.

The technical result is achieved by the fact that the device contains a control panel and a point source of light, and the new one is that an additional counter, an indication unit, a second pulse generator, a first one-shot, a second one-shot with an adjustable pulse duration, a third shot and a fourth shot, a OR element , element And, second generator, second element And, divider by 10, divider by 1000, programmable divider, first and second triggers, second counter and register, while the output of the And element is connected with the first input of the counter, the first output of the control panel is connected to the first input of a point light source, the second output is with the second input of the display unit, the third output is with the second input of the second one-shot with an adjustable pulse duration, the output of the second pulse generator is connected to the input of the first one-shot, the output which is connected to the first input of the OR element and to the first input of the second one-shot with an adjustable pulse duration, the output of which is connected to the input of the third one-shot, the output of which is connected with the second input of the OR element, the output of which is connected to the second input of the point light source, the input of the fourth one-shot is connected to the output of the second pulse generator, and the output is connected to the first input of the first trigger and the second input of the first counter, the output of which is connected to the first input of the register, the output the third one-shot is also connected to the second inputs of the first and second triggers, divider by 1000, programmable divider, second counter and register, the output of the second generator is connected to the first inputs of the second element And and a divider by 1000 and an input of a divider by 10, the output of which is connected to the first input of the first element And, the second input of which is connected to the output of the first trigger, the output of the divider by 1000 is connected to the first input of the second trigger, the output of which is connected to the second input of the second element And, the output which is connected to the third input of the programmable divider, the first input of which is connected to the output of the register, and the output to the first input of the second counter, the output of which is connected to the first input of the display unit.

The inventive device due to the introduction of a counter, an indication unit, a second pulse generator, a first one-shot, a second one-shot with an adjustable pulse duration, a third one-shot and a fourth one-shot, an OR element, an And element, a second generator, a second And element, a divider by 10, a divider by 1000, the programmable divider, the first and second triggers, the second counter and register can improve the reliability of determining the lability of the human visual system.

Thus, the claimed device differs from the known new property, which determines the receipt of a positive effect.

Figure 1 presents the structural diagram of the inventive device, figure 2 is a timing diagram explaining its operation.

Figure 3 presents a timing diagram of a sequence of paired light pulses presented to determine the lability of the human visual system, where

- τ _imp - the duration of the light pulse;

- τ _mission - the duration of the interpulse interval;

- T is the time interval for the repetition of a sequence of paired light pulses.

Figure 4 presents the timing diagrams of two light pulses separated by the interpulse interval t of the _mission and the visual sensations caused by them, where

- figa is a timing diagram of two light pulses separated by an interpulse interval t _mission , causing a visual sensation of separation of pulses;

- figb - time diagram of the visual sensation of the two light pulses shown in figa;

- FIG. 4c is a timing diagram of two light pulses separated by a threshold inter-pulse interval t _then , at which a subjective sensation of fusion of two light pulses in a pair into one is achieved;

- Fig.4g is a timing diagram of the visual sensation of two light pulses shown in Fig.4B;

- τ ₁ - the time of visual sensation is the time between the moment of exposure of light to the retina and the moment of occurrence of the corresponding visual sensation [1, 2] (fig.4b);

- τ ₂ is the recovery time is the time between the moment of termination of the effect of light on the retina and the moment the corresponding visual sensation disappears [1, 2] (Fig. 4b).

The inventive device contains a generator of 1 second pulses, a generator 2, the first 3 one-shot, the second 4 one-shot with an adjustable pulse duration, the third 5 and fourth 6 one-shot, element OR 7, the first 8 and second 9 elements And, the divider 10 by 10, the divider 11 by 1000, programmable divider 12, first 13 and second 14 triggers, first 15 and second 16 counters, register 17, point source of light 18, display unit 19 and control panel 20.

The generator of 1 second pulses is designed to generate pulses with a frequency of 1 Hz, providing a given repetition time of a sequence of two light pulses, and can be performed according to the known scheme.

Generator 2 is designed to generate a sequence of pulses with a frequency of 10 kHz and can be performed according to the known scheme.

Single vibrators 3, 5 are designed to generate light pulses with a duration of 50 ms, single vibrator 4 is designed to form an adjustable pause between two light pulses in a pair in the range from 5 to 150 ms. Single vibrator 6 is designed to generate a short pulse.

Single vibrators 3-6 can be performed according to the scheme [11, Fig. 4.20, p.216] using the K155AG1 microcircuit, which can be launched both on the leading and trailing edges of the incoming pulses.

The 10 by 10 divider is designed to generate counting pulses with a frequency of 1 kHz, providing a measurement accuracy of 1 ms, and can be performed, for example, on the K155IE1 chip.

The divider 11 by 1000 is designed to form a time interval of 0.1 s and can be performed, for example, on K155IE1 microcircuits by connecting the counting inputs of subsequent cascades with the outputs of the previous ones [12, p. 42].

Programmable divider 12 is designed to divide 1000 pulses by a number equal to the value of the total duration of the light pulse τ _imp and the inter-pulse interval t of the _mission between the light pulses in a pair. The divider can be performed, for example, on K155IE8 microcircuits according to the scheme [12, Fig. 32, p. 48].

The first 13 and second 14 triggers are standard RS triggers.

The first counter 15 is designed to determine the value of the total duration of the light pulse τ _imp and the interpulse interval t of the _mission between the light pulses in a pair, in ms.

The second counter 16 is designed to determine the value of the result of the division at the output of the divider 12, in Hz.

Register 17 is designed to store the value of the total duration of the light pulse τ _imp and the interpulse interval t of the _mission between the light pulses in a pair, ms. The register can be performed, for example, on chips K555IR22.

The point light source 18 is intended for the presentation of light pulses and can be performed, for example, on a LED type AL307EM.

The indicators in the display unit 19 are intended to display the lability of the visual system and can be performed, for example, on indicators of the type ALS333A.

The remaining functional units of the structural diagram of the device are well known.

The device operates as follows.

When the power is turned on, the dividers 11 and 12, the first 13 and second 14 triggers, the first 15 and second 16 counters are reset (chains are not shown). Power is supplied from the control panel 20 to a point light source 18, the generator 1 generates pulses with a frequency of 1 Hz (Fig. 2a), which are fed to the input of the first 3 single-vibrator, which generates a pulse of a given duration of 50 ms along the leading edge of each pulse (Fig. 2b) and the generator 2 generates a sequence of pulses with a frequency of 10 kHz supplied to the first input of the second element And 9 and to the counting inputs of the dividers 10 and 11. From the output of the divider 10 pulses with a frequency of 1 kHz arrive at the first input of the first element And 8 (fig.2z )

At the same time, pulses from generator 1 are fed to the fourth 6 single-shot, which generates a short pulse along the leading edge of each pulse (Fig.2c), which resets the first 15 counter and sets the first 13 trigger to "1" (Fig.2g). From the output of the first 13 trigger, the level of the logical unit goes to the second input of the first element And 8, while the pulses from the output of the divider 10 through the first element And 8 go to the counting input of the first 15 counter.

The pulse from the output of the first 3 single vibrator through the element OR 7 enters the point source of light 18 (Fig.2E) and the trailing edge starts the second 4 single vibrator. The duration of the pulse at the output of the one-shot 4 is regulated by the test subject from the remote control 20 within the specified limits (Fig.2g). On the trailing edge of the pulse from the output of the second 4 single-shot, a third 5 single-shot is launched, generating a pulse of a given duration of 50 ms (Fig.2d), which through the element OR 7 enters a point source of light 18 (Fig.2e).

On the front of the pulse from the output of the third 5 single-shot, the first 13 trigger is reset and the logic zero level is set at its output (Fig.2g), which is fed to the second input of the first element And 8, while the passage of pulses from the output of the divider 10 through the first element And 8 on the counting input of the first 15 counters is blocked.

At the output of the first element And 8 a packet of pulses will be formed (Fig. 2i), the number of pulses in the packet is equal to the pulse duration at the output of the first 13 trigger (Fig. 2g) or the sum of the pulse durations at the outputs of the first 3 and second 4 one-shots in ms. The number of pulses in the packet is considered the first 15 counter, the counting result is recorded by the pulse from the output of the third 5 single-shot in register 17, from the output of which goes to the control inputs of the divider 12.

At the same time, the pulse from the output of the third 5 single-vibrator resets the dividers 11 and 12, the second 16 counter and sets the second 14 trigger to “1” (Fig.2k). From the output of the second trigger 14, the level of the logical unit goes to the second input of the second element And 9, while the pulses from the output of the second 2 generator through the second element And 9 are fed to the counting input of the divider 12 (Fig.2l). At the end of the pulse from the output of the third 5 single-vibrator, the operation of the dividers 11, 12 and second 16 of the counter is allowed. After 0.1 with a pulse from the output of the divider 11, the second 14 trigger is reset and the logic zero level is set at its output (Fig.2k), which is fed to the second input of the second element And 9, while the passage of pulses from the output of the generator 2 through the second element And 9 to the counting input of the divider 12 is blocked (Fig.2L). During 0.1 s, a packet of 1000 pulses will arrive at the counting input of the divider 12 (Fig. 2m).

The divider 12 divides a pack of 1,000 pulses per value of the total duration of the light pulse τ _imp on the output of the first monostable multivibrator 3 and the pulse interval t between the light _mission pulses in a pair at the output of the second monostable multivibrator 4, whereby at the output pulse train is formed. The number of pulses in the packet is considered the second 16 counter, the calculation result is sent to the display unit 19.

The test of the rotation of the handle of the potentiometer of the remote control 20 reduces the pulse duration at the output of the second 4 one-shot until the moment of subjective merging of two light pulses in a pair into one (figv, d). The reciprocal of the sum of the pulse durations at the outputs of the first 3 and second 4 single-vibrators is taken as the value of the lability of the human visual system and is calculated by the divider 12 and the second 16 counter according to the formula

where F is the lability of the human visual system, Hz; τ _imp - the duration of the light pulse, ms; t _then - the duration of the interpulse interval at which the subject has a feeling of subjective fusion of two light pulses in a pair of one, ms.

To read the lability value, the subject switches the key on the control panel 20, removes power from the point light source 18 and supplies it to the display unit 19, which displays the lability value in Hz.

The lability of the human visual system is explained by its inertia, that is, the presence of visual sensation time τ ₁ and recovery time τ ₂ .

When a subject presents two light pulses with a duration of τ _imp > τ ₁ separated by an interpulse interval t of a _mission > t _then (Fig. 4a), he experiences a subjective sensation of separation of two light pulses in a pair (Fig. 4b). With a decrease in the duration of the interpulse interval t of the _mission between two light pulses in a pair to a value of t _mission = t _then (Fig. 4c), the subject experiences a sensation of subjective fusion of two light pulses in a pair into one (Fig. 4 g). The sum of the duration of the light pulse τ _imp and the duration of the threshold interpulse interval t _then between two light pulses in a pair, at which a subjective sensation of fusion of two light pulses in a pair into one is achieved, determines the threshold value of the period above which the visual system can sense light pulses in exact accordance with their frequency.

During the action of a light stimulus, receptive fields (RP) of neurons undergo three phases of restructuring [13]. During the first phase with a duration of the order of 10 ms, the spatio-temporal accumulation of signals and the formation of the excitation zone of the RP occur. During the second phase, lasting from 50 to 60 ms, depending on the parameters of the stimulus, the process of narrowing the zone of summation of the RP proceeds. During the third phase of perestroika, the zones of summation of fields expand and the functional disorganization of RP. Neural structures come to their original state and become ready for a new cycle of perception. Since the second phase of the formation of RP neuron ends in 60-70 ms after the presentation of the light stimulus, the duration of the light pulses is taken equal to 50 ms.

The disappearance of RP neurons occurs in the period from 100 to 200 ms after the presentation of the light stimulus [14]. Therefore, two light pulses will be felt separate if the second light pulse is presented 100-200 ms after the start of the presentation of the first light pulse. Then the total duration of the light pulse and the interpulse interval should be

τ _imp + t _missions ≥ (100 ... 200) ms.

With the duration of the light pulse τ _imp = 50 ms, the initial duration of the inter-pulse interval should be

t _NMI ≥ (50 ... 150) ms

and taken equal to 150 ms.

The perception of a visual stimulus is hampered under the conditions of reverse masking, which consists in a deterioration in the perception of the first time stimulus due to the presentation of the second stimulus in the immediate spatiotemporal proximity to the first. It was shown that there is not only a reverse effect, but also direct masking, in which the first stimulus affects the quality of perception of the second [15]. At an interstimulus interval of 500 ms, masking effects are absent or weakly expressed [16]. To eliminate the masking effect, the sequence of paired light pulses is repeated at a constant time interval of 1 s.

Thus, the claimed device allows to increase the reliability of determining the lability of the human visual system.

Information sources

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2. Semenovskaya E.N. Electrophysiological studies in ophthalmology. - M .: Medgiz, 1963 .-- 279 p.

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9. Supin A.Ya. Neural mechanisms of visual analysis. - M .: Nauka, 1974. - 192 p.

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11. The calculation of the elements of digital devices: Textbook. allowance / L.N. Presnukhin, N.V. Vorobiev, A.A. Shishkevich; Ed. L.N. Presnukhina. - 2nd ed., Revised. and add. - M.: Higher School, 1991 .-- 526 p.

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Claims (1)

A device for determining the lability of the human visual system, comprising a control panel and a point light source, characterized in that it additionally includes a counter, an indication unit, a second pulse generator, a first one-shot, a second one-shot with an adjustable pulse duration, a third one-shot and a fourth one-shot, element OR, element AND, second generator, second element AND, divisor by 10, divisor by 1000, programmable divider, first and second triggers, second counter and register, while the output is ele And is connected to the first input of the counter, the first output of the control panel is connected to the first input of a point light source, the second output to the second input of the display unit, the third output to the second input of the second one-shot with an adjustable pulse duration, the output of the second pulse generator is connected to the input of the first one-shot, the output of which is connected to the first input of the OR element and to the first input of the second one-shot with an adjustable pulse duration, the output of which is connected to the input of the third one-shot, the output to which is connected to the second input of the OR element, the output of which is connected to the second input of a point light source, the input of the fourth one-shot is connected to the output of the second pulse generator, and the output to the first input of the first trigger and the second input of the first counter, the output of which is connected to the first input of the register , the output of the third one-shot is also connected to the second inputs of the first and second triggers, the divider by 1000, the programmable divider, the second counter and register, the output of the second generator is connected to the first inputs of the second of the first element AND and the divider by 1000 and the input of the divider by 10, the output of which is connected to the first input of the first element And, the second input of which is connected to the output of the first trigger, the output of the divider by 1000 is connected to the first input of the second trigger, the output of which is connected to the second input of the second element And, the output of which is connected to the third input of the programmable divider, the first input of which is connected to the output of the register, and the output to the first input of the second counter, the output of which is connected to the first input of the display unit.

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