JPH0586216B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention discharges fluid from a fluid discharge means toward the cornea of an eye to be examined, deforms the cornea based on the discharge of the fluid, and measures the intraocular pressure value. Related to improvement of non-contact tonometer for measurement.

(Prior Art) Conventionally, non-contact tonometers have been equipped with a cylinder device as a fluid discharge means, as disclosed in Japanese Patent Publication No. 54-38437, for example.
A pulse of air as a fluid that draws a predetermined fluid pressure characteristic curve with time as a parameter is generated, the air pulse is emitted toward the cornea of the eye to be examined, and the cornea is changed from a convex state based on the release of the air pulse. Transform it from a flat state to a concave state,
Since the time for deformation and recovery of the cornea to undergo such deformation has a correlation with intraocular pressure, the amount of deformation of the cornea is photoelectrically detected, the time for deformation and recovery is measured, and based on that, the intraocular pressure is There are known devices that measure values.

By the way, in this conventional non-contact tonometer, if the fluid pressure characteristic curve is not constant, the intraocular pressure value obtained by operating the cylinder device will contain an error. Therefore, in conventional non-contact tonometers, since there is a relationship between the moving speed of the piston and the flow pressure characteristic curve of the fluid, the cylinder device is activated in advance before measuring the intraocular pressure value. It is checked whether the moving speed of the piston of the cylinder device matches the reference moving speed, and it is determined whether the fluid is discharged according to a predetermined fluid pressure characteristic curve. When the moving speed of the cylinder matches the reference moving speed, it is determined that the operation of the cylinder device is normal.

(Problem to be Solved by the Invention) However, this conventional checking means is based on the assumption that the fluid pressure characteristic curve is always constant, and in reality, the fluid pressure varies depending on the temperature. ,
It is a function of density, etc., and even if the piston movement speed matches the standard movement speed, the fluid pressure characteristic curve is not necessarily constant, and the cylinder device is essentially operating normally. It contains a problem that it is not possible to check whether or not it is true.

By the way, the intraocular pressure of the eye to be examined and the flow pressure of the fluid are in direct correspondence, so recently, fluid has been released from a fluid discharge means to the cornea of the eye to be examined, and while deforming the cornea, the intraocular pressure of the eye to be examined is reduced. This type of non-intraocular pressure sensor detects changes in the fluid pressure corresponding to the corneal deformation sequentially in response to the corneal deformation using a fluid pressure change detection circuit, and measures the intraocular pressure value based on the relationship between the corneal deformation and the fluid pressure. Contact tonometers have been proposed (e.g.
Utility Model Publication No. 59-143402).

This device has an intraocular pressure measurement circuit that is significantly different from conventional ones.In order to measure the intraocular pressure value by electrically detecting the pressure of the fluid, the fluid pressure detection circuit is used as an electric circuit. This is complicated, and it is required to electrically check whether the operation is normal.

(Object of the Invention) The present invention has been made in view of the above circumstances, and its purpose is to provide a non-contact method that can check whether or not the operation of the electric circuit itself is normal. There is a place that provides a tonometer.

(Means for Solving the Problems) In order to achieve the above object, the non-contact tonometer according to the present invention includes a fluid discharge means for discharging fluid toward the cornea of the eye to be examined, and a fluid discharge means for discharging the fluid toward the cornea of the eye to be examined. a pressure sensor for detecting pressure; a fluid pressure change detection circuit for detecting a change in fluid pressure while deforming the cornea using a signal from the pressure sensor; A non-contact tonometer that measures an intraocular pressure value of an eye to be examined based on a signal from the fluid pressure change detection circuit and a signal from the corneal deformation detection means, the fluid ejection means comprising a corneal deformation detection means. A self-check circuit is provided that automatically checks the operation of the fluid pressure change detection circuit, including the operation of the fluid discharge means, based on a signal from the pressure sensor obtained by driving the fluid pressure sensor. .

(Function) According to the non-contact tonometer according to the present invention, the self-check circuit determines whether the fluid pressure change detection circuit is normal or not based on the signal of the pressure sensor obtained by driving the fluid discharge means. Detecting whether or not the discharge means is operating normally.

(Example) Examples of the non-contact tonometer according to the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a cylinder device as a fluid discharge means, 2 is a cornea of an eye to be examined, 3 is an ejection optical system, and 4 is a detection optical system. Cylinder device 1
has the function of emitting air pulses as a fluid to the cornea 2 of the eye to be examined to deform the cornea 2, and is generally composed of a rotary solenoid 5, a cylinder 6, and a solenoid drive circuit 7, and reference numeral 8 denotes the rotary solenoid. 5 drums are shown.

The cylinder 6 has a cylinder tube portion 9, and the cylinder tube portion 9 is provided with a nozzle tube portion 10 and a sensing tube portion 11. Nozzle cylinder part 10
is formed coaxially with the cylinder tube portion 9, and the sensing tube portion 11 is formed to protrude from the peripheral wall of the cylinder tube portion 9. A piston 12 is provided in the cylinder tube portion 9 so as to be able to reciprocate. This piston 12 is connected to the drum 8 via a piston rod 13. The nozzle cylinder part 10 extends straight toward the cornea 2, and the air as a fluid in the cylinder cylinder part 9 is pulsed from the nozzle cylinder part 10 toward the cornea 2 by the forward movement of the piston 12. It was once released. A pressure sensor 11a is attached to the sensing cylinder portion 11, and the function of this pressure sensor 11a will be described later.

The cornea 2 is deformed from a convex state to a flat state as the flow pressure of the fluid increases, and symbol C indicates a state in which the cornea 2 has been deformed, and symbol m
indicates the amount of deformation. This amount of deformation m is calculated by assuming that the apex of the cornea 2 before undergoing deformation is 0 ₂ and the apex of the cornea C that has undergone deformation is 0 ₃ .
The distance between vertices 0 ₂ and 0 ₃ that exist on the center line 0 ₁ of .

The exit optical system 3 and the detection optical system 4 have a function of detecting the amount of deformation of the cornea 2. Here, the exit optical system 3 and the detection optical system 4 have the function of detecting the amount of deformation of the cornea 2 based on the cylinder device 1. This constitutes a corneal deformation photoelectric detection means that photoelectrically detects the amount of corneal deformation. The exit optical system 3
is composed of a light source 14, a condensing lens 15, an aperture 16, and a projection lens 17, and ₀₄ indicates the optical axis of this exit optical system 3. The diaphragm 16 is provided at the focal point of the lens 17, and the light emitted from the light source 14 is condensed by the condenser lens 15, the amount of light is adjusted by the diaphragm 16, and converted into a parallel beam by the projection lens 17. This is projected onto the cornea 2 as detection light.

The detection optical system 4 includes an imaging lens 18 and an aperture 1
9 and a photoelectric conversion circuit 20, and the photoelectric conversion circuit 20 includes a light receiving element 21 and an amplifier circuit 22. The detection light reflected by the cornea 2 is guided to the light receiving element 21 via the imaging lens 18 and the diaphragm 19, photoelectrically converted by the light receiving element 21, amplified by the amplifier circuit 22, and then converted to the photoelectric converter. Reference numeral 20 has a function of outputting a photoelectric output Vz of the amount of corneal reflected light corresponding to the amount m of deformation of the cornea 2 to an intraocular pressure value conversion circuit to be described later.

The pressure sensor 11a constitutes a part of a fluid pressure change detection circuit 23 that detects a change in fluid pressure corresponding to the intraocular pressure of the eye to be examined, and the detection output Vp detected by the pressure sensor 11a is , are input to the intraocular pressure value conversion circuit 25 via the amplifier circuit 24. This intraocular pressure value conversion circuit 25 uses the detection output Vp of the fluid pressure change detection circuit 23 and the photoelectric conversion circuit 20.
It has a function of determining the relationship between the change in the amount of corneal reflected light corresponding to the change in fluid pressure based on the photoelectric output Vz of , and converting the fluid pressure corresponding to a predetermined amount of deformation m into an intraocular pressure value.

Next, the configuration of the intraocular pressure value conversion circuit 25 will be explained with reference to FIG.

In this FIG. 2, 26 is a CPU. This CPU 26 is turned on by a power switch 27. This CPU 26 is programmed with a self-check mode and an intraocular pressure measurement mode. This CPU26 has a power switch 27
At the same time as the CPU 26 is turned on, it enters a self-check mode and outputs an operation signal to operate a self-check circuit, which will be described later. explain.

When the CPU 26 enters the intraocular pressure measurement mode, it is possible to output an operation signal for operating the intraocular pressure measurement circuit system. That is, when the measurement switch 28 is turned on, the CPU 26 outputs a drive signal as an operation signal to the solenoid drive circuit 7, thereby driving the cylinder device 1. By driving the cylinder device 1, the emission of air pulses toward the cornea 2 is started. By this,
The pressure inside the cylinder 9 changes from static pressure to dynamic pressure and increases. pressure sensor 1
1a detects this pressure increase within the cylinder 9.

The intraocular pressure measurement circuit system includes a fluid pressure change detection circuit 23 and a corneal reflected light amount change detection circuit 29. The fluid pressure change detection circuit 23 includes a comparison circuit 30, a timing pulse generator 31, an address counter 32, an OR circuit 33, an incremental counter 34, a D/A converter 35, and a switching circuit 36. . The detection output Vp of the pressure sensor 11a is input to one terminal of the comparison circuit 30. This detection output Vp is also input to the A/D converter 37;
Since this constitutes a part of the self-check circuit, the explanation here will be limited to the fact that the A/D converter 37 has the function of converting the detection output Vp from analog to digital.

A reference voltage Vs is input to the other terminal of the comparator circuit 30. This comparison circuit 30 has a reference voltage Vs
and the detection output Vp, and when the detection output Vp is larger than the reference voltage Vs, the comparison pulse P becomes high level. This comparison pulse P
is input to a timing pulse generator 31, an address counter 32, and an OR circuit 33.
The functions of the timing pulse generator 31 and the address counter 32 will be described later, and the OR circuit 3
3. The relationship between the incremental counter 34, the D/A converter 35, and the reference voltage Vs will be explained next.

OR circuit 33 and incremental counter 34
and the D/A converter 35 have a function of increasing the reference voltage Vs stepwise. That is, each time a comparison pulse P is input to the incremental counter 34 via the OR circuit 33, the number of comparison pulses P is added up and a count pulse C corresponding to that number is outputted to the D/A converter 35. D/
The A converter 35 outputs a reference voltage Vs corresponding to the count value C to the comparison circuit 30.

The reference voltage Vs is set so that its initial value Vso is equal to the detected output Vpo before driving the cylinder device 1 by an offset removal operation explained in the self-check mode described later.
The setting of the initial value Vso of the reference voltage Vs in the intraocular pressure measurement mode is given by the offset removal pulse PS output from the CPU 26, and this offset removal pulse PS is output from the OR circuit 3.
3 to the incremental counter 34.

For example, assume that the initial value Vso=Vpo and the detection output Vp increases slightly due to the driving of the cylinder device 1. Then, the comparison circuit 30 becomes high level and outputs one comparison pulse P to the incremental counter 34. Assuming that the initial value of the incremental counter 34 is "0", when one comparison pulse P is input, the count value is updated from "0" to "1". Then, incremental counter 3
4 outputs the corresponding count value C to the D/A converter 35. Then, the D/A converter 35 converts the count value C from digital to analog. As a result, the reference voltage Vs output from the D/A converter 35 becomes Vso+ΔVp.
Then, since the detection output Vp becomes lower than the reference voltage Vs, the comparison pulse P of the comparison circuit 30 becomes low level. Since the detection output Vp increases as the air pulse is released, the detection output
The magnitude of Vp exceeds the reference voltage Vs=Vso+ΔVp. Then, the comparison pulse P of the comparison circuit 30 becomes high level. By repeating this, the reference voltage Vs increases stepwise.

The output of the timing pulse generator 31 and the output of the address counter 32 are input to a switching circuit 36. The switching circuit 36 is shown conceptually and includes switch circuits 36a, 36b, 36
It has c. The switch circuit 36a is composed of a movable contact 36d, fixed contacts 36e, 36f,
The switch circuit 36b is composed of a movable contact 36g and fixed contacts 36h and 36i.
C is composed of a movable contact 36j and fixed contacts 36k and 36l.

This switching circuit 36 is controlled by the CPU 26, and its movable contacts 36d, 36
g, 36j are fixed contacts 36f, 36h, respectively when the CPU 26 is in the intraocular pressure measurement mode.
Connected to 36k. The timing pulse generator 31 has a function of sequentially specifying sampling of the photoelectric output Vz as the amount of corneal reflected light, and each time one comparison pulse P of the comparison circuit 30 is input,
Timing pulse via switch circuit 36b
Pt is connected to the control terminal 37a of the A/D converter 37, and the A/D constituting part of the corneal reflected light amount change detection circuit 29
This signal is output to the control terminal 38a of the D converter 38. The photoelectric output Vz of the photoelectric conversion circuit 20 is input to this A/D converter 38 . Note that here, this photoelectric conversion circuit 20 is turned on at the same time as the measurement switch 28 is turned on.

This photoelectric output Vz increases because the reflected light beam from the cornea approaches a parallel light beam from a divergent light beam as the cornea 2 undergoes deformation toward a flattened state. The A/D converter 38 uses a timing pulse
Its photoelectric output Vz is sequentially analog based on Pt.
It has the function of digital conversion. The photoelectric output value Dz as a digital signal is determined by the memory circuit 39
is input. The address counter 32 constitutes an address generation section including peripheral circuits of the comparison circuit 30, and has a function of specifying an address of the memory circuit 39. The designated address value Ia as the address designation signal is the switch circuit 36c.
The signal is input to a memory circuit 39 and a comparison circuit 45 of a self-check circuit to be described later. The contents of the address counter 32 are updated sequentially every time the comparison pulse P is input. As a result, the addresses of the memory circuit 39 can be changed to, for example, "0", "1", "2", ..., "N
”
is specified, and photoelectric output values Dz as light amount data corresponding to changes in detection output Vp are sequentially stored in the specified addresses. In this manner, the memory circuit 39 stores sequentially digitized photoelectric output values at their designated addresses based on the addressing signal. Note that when the timing pulse Pt is input to the A/D converter 37,
The detection output Vp is converted from analog to digital and output as a detection pressure value Dp to the switch circuit 36a, but since the movable contact 36d is connected to the fixed contact 36f, the operation of the self-check circuit described later is stopped. There is.

In this way, the memory circuit 39 sequentially stores changes in the amount of detected light corresponding to changes in the detected pressure in addresses. The CPU 26 outputs a drive stop signal to the solenoid drive circuit 7 when a predetermined time has elapsed. When the solenoid drive circuit 7 stops driving, the detected light amount data stored in the memory circuit 39 is input to the CPU 26. The CPU 26 performs calculations based on the detected light amount data and the specified address value Ia to obtain a pressure-light amount function curve as shown in FIG.
The intraocular pressure value is obtained from Lmax when the amount of light is maximum. In FIG. 3, a correlation function curve Hi shown by a solid line represents a case where the intraocular pressure of the eye to be examined is high, and a correlation function curve Lo shown by a broken line represents a case where the intraocular pressure of the eye to be examined is low.

Next, the self-check circuit will be explained.

In FIG. 2, reference numeral 40 is a self-check circuit. This self-check circuit 40 has an operation detection system 41 for the cylinder device 1 and an operation detection system 42 for the address generation section. The operation detection system 41 includes a comparison circuit 43 and a reference value generation circuit 44, and the operation detection system 42 includes a comparison circuit 45 and a reference value generation circuit 46. One terminal of the comparison circuit 43 is connected to the movable contact 36d, and the other terminals are connected to the reference value generation circuit 44.
One terminal of the comparison circuit 45 is connected to the movable contact 36j, and the other terminals are connected to the reference value generation circuit 46.

The CPU 26 outputs a reference value setting signal to the reference value generation circuits 44 and 46 at the same time as the power switch 27 is turned on. At the same time, the CPU
Reference numeral 26 outputs a switch switching signal Sc to the switching circuit 36. The switching circuit 36 has movable contacts 36d, 36g, and 36j connected to fixed contacts 36f, 36i, and 36l, respectively, in response to the switch switching signal Sc. When the movable contacts 36d, 36j are connected to the fixed contacts 36f, 36l, the output of the CPU 26 is input to the comparison circuits 43, 45, and the comparison circuits 43, 45 are reset.
Note that the comparison circuits 43 and 45 have a digital comparison function.

The CPU 26 outputs a reset signal R which resets the comparison circuits 43 and 45 and at the same time resets the address counter 32 and the incremental counter 34. The count values of the address counter 32 and the incremental counter 34 become "0" by this reset signal.
Next, the CPU 26 outputs an offset removal pulse PS to the incremental counter 34 via the OR circuit 33 for removing the offset between the detection output Vp of the pressure sensor 11a and the reference voltage Vs. This is because the static pressure inside the cylinder 9 is a function of temperature and density, and is not always constant but changes.
This creates a difference between Vso and the detected output Vpo, and an offset operation is required to perform "zero" point alignment.

When the offset removal pulse PS is input, the incremental counter 34 changes the count value C to D/D in response to the offset removal pulse PS.
The signal is output to the A converter 35. The D/A converter 35 performs digital-to-analog conversion on the count value C and outputs it to the comparator circuit 30 as a reference voltage Vs. The comparison circuit 30 becomes low level when the reference voltage Vs becomes larger than the detection output Vpo. The CPU 26 outputs offset removal pulses until this reference voltage Vs becomes larger than the detection output Vpo.
The PS is outputted to the incremental counter 34. The incremental counter 34 sequentially counts this offset removal pulse PS,
The reference voltage Vs is increased stepwise every ΔVs=ΔVp. When the comparison circuit 30 becomes low level, its output is inputted to the CPU 26 as the offset cancellation signal Po, and the CPU 26 receives the offset cancellation pulse.
Stop PS output.

When the offset release signal is input, the CPU 26 outputs a switch switching signal Sc to the switching circuit 36 and also outputs a drive signal to the solenoid drive circuit 7. As a result, the switching circuit 36 has its movable contacts 36d, 36g, and 36j connected to the fixed contacts 36e, 36h, and 36k, respectively, and
The cylinder device 1 is driven. Then, the detection output Vp output from the pressure sensor 11a increases. This detection output Vp is input to the A/D converter 37. The A/D converter 37 performs analog-to-digital conversion on the detection output Vp for each timing pulse Pt, and outputs it to the comparison circuit 43 as a detected pressure value Dp. The comparison circuit 43 digitally compares the reference pressure value Cp and the detected pressure value Dp. This reference pressure value Cp is in one-to-one correspondence with a reference address value Ia, which will be described later, and the cylinder device 1 is manufactured to operate in accordance with this reference pressure value Dp. The comparison circuit 43 uses this reference pressure value Cp
and its detected pressure value Dp match,
The output becomes high level and the AND circuit 47
Output to . If there is a failure in either the timing pulse generator 31 or the A/D converter 37, including the operation of the cylinder device 1, the detected pressure value Dp will not match the reference pressure value Cp. This allows a check to be made as to whether the operating system of the cylinder device 1 is normal or abnormal.

The address counter 32 outputs the specified address value Ia to the comparison circuit 45 every time the comparison pulse P of the comparison circuit 30 is input. The comparison circuit 45 compares the reference address value Ca and the specified address value Ia,
When the reference address value Ca and specified address value Ia match, it becomes high level and the output is
The signal is output to the AND circuit 47. If there is a failure in any of the address counter 32, comparison circuit 30, OR circuit 33, incremental counter 34, and A/D converter 35, the address counter 32
Because the specified address value Ia is not updated or the normal specified address value Ia is not output, the reference address value Ca and the specified address value Ia become inconsistent, and this causes the address generation unit to malfunction. A check will be made to see if it is working.

When the outputs of the comparison circuits 43 and 45 are both at high level, the AND circuit 47 determines that the operation of the cylinder device 1 and the operation of the address generation section are normal, and outputs a determination signal to the CPU 26. When the CPU 26 receives the determination signal from the AND circuit 47, the CPU 26 supplies the reference voltage for the next step from the internal ROM (not shown) to the reference value generation circuits 44 and 46.
Reference pressure value Cp and reference address value Ca corresponding to Vs
Enter and reset to the new standard value. Then, a self-check is executed using the new input reference voltage value Vs, reference pressure value Cp, and reference address value Ca, and if the operation is normal, the AND circuit 47 outputs a determination signal to the CPU 26 again.

The CPU 26 executes predetermined steps for rewriting the reference values Cp and Ca for several minutes, and when a judgment signal is obtained from the AND circuit 47 for all the steps, the CPU 26 judges that the operation is normal.
Based on the all-step determination signal of the circuit 47, a signal for displaying, for example, "SELF CHECK OK" on the display 48 is output, and the mode shifts to the intraocular pressure measurement mode. If the AND circuit 47 does not output a judgment signal for even one step, the CPU 26
The transition to the intraocular pressure measurement mode is canceled and the message ``Problem in operation (unable to measure); please contact the service center.''
The display 4 sends a signal that causes the display 48 to display
Output to 8.

(Effects of the Invention) Since the non-contact tonometer according to the present invention is configured as described above, it is possible to check whether the fluid pressure change detection circuit itself, which is an electric circuit directly related to intraocular pressure measurement, operates normally. You can self-check to see if this is the case.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of a non-contact tonometer as an intraocular pressure measuring instrument according to the present invention, Fig. 2 is a circuit diagram of the main part of the intraocular pressure value conversion circuit of the non-contact tonometer, and Fig. 3 is a schematic diagram of a non-contact tonometer as an intraocular pressure measuring instrument according to the present invention. FIG. 3 is a diagram showing the correlation between the detection output and the amount of detected light used to explain the intraocular pressure measurement. DESCRIPTION OF SYMBOLS 1...Cylinder device, 2...Cornea, 3...Ejection optical system, 4...Detection optical system, 11a...Pressure sensor, 23...Fluid pressure change detection circuit, 26...
CPU, 27...power switch, 28...measuring switch, 29...corneal reflected light amount change detection circuit,
30... Comparison circuit, 31... Timing pulse generator, 32... Address counter, 34... Incremental counter, 35... D/A converter,
36...Switching circuit, 37...A/D converter,
40...Self check circuit, 41, 42...Operation check system, 47...AND circuit.

Claims (1)

[Scope of Claims] 1. A fluid discharging means for discharging fluid toward the cornea of the eye to be examined, a pressure sensor for detecting the pressure of the fluid, and a method for deforming the cornea using a signal from the pressure sensor. a fluid pressure change detection circuit for detecting a change in fluid pressure; and a corneal deformation detection means for detecting a deformation of the cornea of the eye to be examined; A non-contact tonometer that measures the intraocular pressure value of the eye to be examined using a signal from a detection means, including the operation of the fluid ejection means based on a signal from the pressure sensor obtained by driving the fluid ejection means. A non-contact tonometer characterized in that a self-check circuit is provided for automatically checking the operation of the fluid pressure change detection circuit.