JPS62122630A - Non-contact type tonometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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. The present invention relates to an improvement in a non-contact tonometer for measuring tonometers, and more specifically, to emit fluid from a fluid discharge means toward the cornea of the eye to be examined, and to deform the cornea while releasing fluid corresponding to the intraocular pressure of the eye to be examined. A change in the state quantity is detected by a state quantity change detection circuit, and a physical quantity corresponding to the amount of deformation of the cornea is detected sequentially in response to the change in the state quantity, and based on the correlation between the physical quantity and the state quantity. This invention relates to a non-contact tonometer that measures intraocular pressure values.

(Prior art) Conventionally, non-contact tonometers have been used, for example, in
As disclosed in Japanese Patent No. 38437, a cylinder device as a fluid discharge means is driven to generate an air pulse as a fluid that draws a predetermined fluid pressure characteristic curve with time as a parameter. The air pulse is emitted toward the cornea of the subject's eye, and the cornea is deformed from a convex state to a flat state to a concave state based on the emitted air pulse. Since there is a correlation, it is known that the amount of deformation of the cornea is photoelectrically detected, the deformation/recovery time is measured, and the intraocular pressure value is measured based on this.

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. Check whether the moving speed of the piston of the cylinder device matches the standard moving speed, determine whether the fluid is released according to a predetermined fluid pressure characteristic curve, and check whether the piston moves. When the speed matches the reference moving speed, it is determined that the cylinder device is operating normally.

(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 is , is a function of density etc.
Even if the piston movement speed matches the standard movement speed, the fluid pressure characteristic curve is not necessarily constant, so it is essential to check whether the cylinder device is operating normally. It contains a defect that makes it impossible to do so. In addition, before measuring the intraocular pressure value, the cylinder device is configured to check whether it is operating normally or not by operating a dedicated switch, so this check may be forgotten. In addition to being inconvenient, there is also the problem that if the intraocular pressure value is measured without checking, the measurement result may contain errors.

By the way, the intraocular pressure of the eye to be examined and the state quantities of the fluid such as the flow pressure and flow velocity of the fluid are in direct correspondence.

Recently, a state quantity change detection circuit detects a change in the state quantity of the fluid corresponding to the intraocular pressure of the subject eye while deforming the cornea by discharging fluid from a fluid discharge means to the cornea of the subject's eye. A type of non-contact tonometer that detects a physical quantity corresponding to the amount of deformation of the cornea by sequentially corresponding to a change in its state quantity, and measures the intraocular pressure value based on the correlation between the physical quantity and the state quantity. are being proposed (for example, Japanese Patent Application No. 59-24227
(See No. 8). This device has a circuit for measuring intraocular pressure values that is significantly different from conventional ones, and conventional checking means are not applied to measure intraocular pressure values by electrically detecting the state quantity of the fluid. Therefore, a new method of checking is required.

(Purpose of the Invention) Therefore, the present invention takes into account the defects of the checking means of conventional non-contact tonometers and deforms the cornea by discharging fluid from the fluid discharging means toward the cornea of the eye to be examined. while detecting a change in the state quantity of the fluid corresponding to the intraocular pressure of the eye to be examined by a state quantity change detection circuit, and detecting a physical quantity corresponding to the amount of deformation of the cornea sequentially corresponding to the change in the state quantity, In a non-contact tonometer that measures intraocular pressure based on the correlation between the physical quantity and its state quantity,
To provide a non-contact tonometer whose operation can be automatically checked upon power-on.

(Means for Solving the Problems) The non-contact tonometer according to the present invention is characterized by a self-check circuit that automatically checks the operation of the fluid discharge means and the operation of its state quantity change detection circuit when the power is turned on. It is located where the .

(Function) According to the intraocular pressure measuring instrument according to the present invention, the self-check circuit automatically operates at the same time as the power is turned on.

This self-check circuit checks whether the operation of the state quantity change detection circuit and the operation of the fluid discharge means are normal or abnormal.

Therefore, it is possible to prevent the operator from forgetting to check, and it is therefore possible to perform accurate intraocular pressure measurement.

(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. The 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 includes a rotary solenoid 5 and a cylinder 6.
, and a solenoid drive circuit 7, and reference numeral 8 indicates a drum of the rotary solenoid 5.

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. The nozzle cylinder part 10 is formed coaxially with the cylinder cylinder part 9, and the sensing cylinder part 11 is formed coaxially with the cylinder cylinder part 9.
It is formed protrudingly on the peripheral wall of.

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 cylinder cylinder part 9
The air as a fluid inside the piston 1 as a pulse
2 is emitted toward the cornea 2 from the nozzle barrel portion 10.

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 toward a planar 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 deformation amount m is 02
, when the vertex of the cornea C that has undergone deformation is 03, it is the distance between the vertex 0□ existing on the center line O□ of the cornea 2 and the vertex 03.

The exit optical system 3 and the detection optical system 4 have a function of detecting a physical quantity corresponding to the amount of deformation of the cornea 2 . The corneal deformation amount photoelectric detection means is configured to photoelectrically detect the amount of deformation of the cornea.

The exit optical system 3 is composed of a light source 14, a condensing lens 15, an aperture 16, and a light projecting lens 17. 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 light beam by the projection lens 17. = Projected onto the cornea 2 as detection light.

The detection optical system 4 includes an imaging lens 18, an aperture 19, and a photoelectric conversion circuit 20, and the photoelectric conversion circuit 20 includes a light receiving element 21 and an amplification circuit 22.

The detection light reflected on the cornea 2 is transmitted through an imaging lens 18,
The light is guided to the light receiving element 21 via the diaphragm 19, photoelectrically converted by the light receiving element 21, and amplified by the amplifier circuit 22. It has a function of outputting the output Vz to an intraocular pressure value conversion circuit which will be described later.

The pressure sensor 11a constitutes a part of a state quantity change detection circuit 23 that detects a change in the state quantity of the fluid corresponding to the intraocular pressure of the subject's eye. The detection output Vp detected by the pressure sensor 11a is input to the intraocular pressure value conversion circuit 25 via the amplifier circuit 24. This intraocular pressure value conversion circuit 25 includes a fluid pressure change detection circuit 23
Based on the detection output VP of the photoelectric conversion circuit 20 and the photoelectric output Vz of the photoelectric conversion circuit 20, the relationship between the change in the amount of corneal reflected light corresponding to the change in fluid pressure is determined as a correlation, and the fluid pressure corresponding to a predetermined amount of deformation m is determined. It has a function to convert into 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 CPO 26 is programmed with a self-check mode and an intraocular pressure measurement mode. The CPU 26 enters the self-check mode at the same time as the power switch 27 is turned on, and outputs an operation signal to operate a self-check circuit, which will be described later. Let's explain the case where this is the case.

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 CPO 26 outputs a drive signal as an operation signal to the solenoid drive circuit 7, thereby driving the cylinder device 1. By driving this cylinder device 1, 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. The pressure sensor 11a detects this pressure increase inside 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 and an incremental counter 34.

It has 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 ■ρ is the A/D
Although the input is also input to the converter 37, since the A/D converter 37 constitutes a part of the self-check circuit, the explanation here will be based on the detection output VP of the A/D converter 37. It is limited to having the function of converting from analog to digital.

=11- The reference voltage Vs is input to the other terminal of the comparison circuit 30. This comparison circuit 30 has a reference voltage Vs and a detection output Vp.
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 relationship between the OR circuit 33, the incremental counter 34, the D/A converter 35, and the reference voltage Vs will be described next.

OR circuit 33, incremental counter 34, and D/A
The converter 35 has a function of increasing the reference voltage Vs in steps. 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. The D/A converter 35 outputs a reference voltage Vs corresponding to the count value C to the comparison circuit 30.

This reference voltage Vs is determined by the offset removal operation described in the self-check mode to be described later, so that the initial value Vso is the detected output V before driving the cylinder device 1.
The initial value Vso of this reference voltage Vs in the intraocular pressure measurement mode is set equal to po.
This is given by the offset removal pulse PS output from 26, and this offset removal pulse PS
is an incremental counter 34 via an OR circuit 33.
has been entered.

For example, assume that the initial value vso=Vpo and the detected output VP slightly increases due to the driving of the cylinder device 1. Then, the comparator circuit 30 becomes high level,
One comparison pulse P is input to the incremental counter 34.
Output towards. Assuming that the initial value of the incremental counter 34 is "0" and one comparison pulse P is input, the count value changes from "0" to "1".
will be updated to. Then, the incremental counter 34
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 becomes higher as the air pulse is emitted, the magnitude of the detection output VP thereafter 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, and 36c.

The switch circuit 36a has a movable contact 36d and a fixed contact 36e.
, 36f, the switch circuit 36b consists of a movable contact 36g, fixed contacts 36h, 36i, and the switch circuit 36c consists of a movable contact 36j, fixed contacts 36k, 36i.
It consists of 12.

This switching circuit 36 is controlled by the CPU 26, and its movable contacts 36d, 36g, and 36j are connected to C
When the PU26 is in the intraocular pressure measurement mode, it is connected to fixed contacts 36f, 36h, and 36k, respectively. The timing pulse generator 31 has a function of sequentially specifying the sampling of the photoelectric output Vz as the amount of corneal reflected light, and every time one comparison pulse P of the comparison circuit 30 is input, the timing pulse generator 31 generates a timing pulse via the switch circuit 36b. pt to A/
The signal is output toward the control terminal 37a of the D converter 37 and the control terminal 38a of the A/D converter 38, which constitutes a part of the corneal reflected light amount change detection circuit 29.

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 is deformed toward a flattened state. The A/D converter 38 has a function of sequentially converting the photoelectric output Vz from analog to digital based on the timing pulse pt.

The photoelectric output value Dz as a digital signal is input to the memory circuit 39.

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 signal is inputted to a memory circuit 39 and a comparison circuit 45 of a self-check circuit, which will be described later, via a switch circuit 36c. 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 are designated as, for example, "0", rl", r2J, . . . The output values Dz are sequentially stored in memory. In this manner, the memory circuit 39 stores sequentially digitized photoelectric output values at their designated addresses based on the addressing signal. In addition, A
When the /D converter 37 also receives the timing pulse pt, it converts the detection output VP from analog to digital and outputs it as a detection pressure value DP toward the switch circuit 36a, but the movable contact 36d is connected to the fixed contact 36f. Therefore, the operation of the self-check circuit, which will be described later, is stopped.

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, C
Data on the amount of detected light stored in the memory circuit 39 is input to the PU 26 .

The CPU 26 uses this detected light amount data and the designated address value Ia.
It calculates the pressure-light amount function curve as shown in Figure 3 by calculating based on Lm when the light amount is maximum.
The intraocular pressure value is obtained from ax. 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 CPO 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 26 switches the switching circuit 3
The switch output signal Sc is output toward the switch 6. The switching circuit 36 connects its movable contacts 36d, 36g, and 36j to the fixed contacts 36f, 36i, and 36fl, respectively, in response to the switch switching signal Sc. Comparison circuits 43, 45 have their movable contacts 3
When 6d and 36j are connected to the fixed contacts 36f and 36fl, the output of the CPU 26 is input and the comparator circuit 43.4
5 is to be reset. Note that this comparison circuit 4
3.45 has the ability to compare digitally.

The CPU 26 outputs a reset signal R that 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 incremental counter 34 are changed by this reset signal.
0'', the CPU 26 then detects the pressure sensor 11
An offset removal pulse PS for removing the offset between the detection output Vp of the signal a and the reference voltage Vs is outputted to the incremental counter 34 via the OR circuit 33. This is because the static pressure inside the cylinder 9 is a function of temperature and density, and is not always constant but changes, so a difference occurs between the reference pressure value VSO and the detected output Vpo. , an offset operation is required to perform "zero" point alignment.

When the offset removal pulse PS is input, the incremental counter 34 inputs the offset removal pulse P.
A count value C is outputted to the D/A converter 35 in response to S. The D/A converter 35 performs digital-to-analog conversion on the count value C and outputs it to the comparison circuit 30 as a reference voltage Vs. The comparison circuit 30 has a reference voltage V
When s becomes larger than the detection output Vpo, it becomes a low level. The CPU 26 outputs the offset removal pulse PS to the incremental counter 34 until the reference voltage Vs becomes larger than the detection output Vpo. The incremental counter 34 sequentially counts this offset removal pulse PS and sets the reference voltage Vs to ΔVs=ΔVP
Increase step by step. When the comparator circuit 30 becomes low level, its output is sent to CP as the offset release signal PO.
It is input to U26, and the CPU 26 stops outputting the offset removal pulse PS.

When the offset cancellation signal is input, the CPU 26 outputs a switch switching signal Sc toward the switching circuit 36 and also outputs a drive signal toward 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 every timing pulse t, and outputs it to the comparison circuit 43 as a detection pressure value DP. The comparison circuit 43 digitally compares the reference pressure value Cp and its detected pressure value op. This reference pressure value Cp is a reference address value I, which will be described later.
There is a one-to-one correspondence with Dp, and the cylinder device 1 is manufactured to operate according to this reference pressure value Dp. The comparator circuit 43 becomes high level and outputs its output to the AND circuit 47 when the reference pressure value Cp and the detected pressure value op match. Timing pulse generator 3 including actuation of cylinder device 1
1. If there is a failure in any of the A/D converters 37, the detected pressure value Dp will not match the reference pressure value cp, which means that the operating system of the cylinder device 1 is not normal. It will be checked to see if it is present or abnormal.

The address counter 32 receives the comparison pulse P of the comparison circuit 30.
Comparison circuit 47 compares the specified address value 8 with each input.
45. The comparison circuit 45 compares the reference address value Ca
is compared with the specified address value Ia, and the reference address value Ca is determined.
When the address value I8 and the specified address value I8 match, it becomes high level and outputs the output to the AND circuit 47. Address counter 32, comparison circuit 30, OR circuit 33, incremental counter 34, A/D converter 3
5, the specified address value Ia of the address counter 32 will not be updated or the normal specified address value Ia will not be output, resulting in a mismatch between the reference address value Ca and the specified address value Ia. Thus, it is checked whether the address generation section is operating normally.

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, it inputs the reference pressure value Cp and reference address value Ca corresponding to the reference voltage Vs of the next step from the internal ROM (not shown) to the reference value generation circuits 44 and 46. and reset to the new standard value. Then, a self-check is executed using the input reference voltage value Vs, reference pressure value Cp, and reference address value Ca, and if the operation is normal, the AND circuit 47 again sends a determination signal to the CPU 26.
Output to.

The CPU 26 executes predetermined steps for rewriting the reference values Cp and Ca for several minutes, and when a determination signal is obtained from the AND circuit 47 for all the steps, the CPU 26 determines that the operation is normal. For example, "5" is displayed on the display 48 based on the total step determination signal.
It outputs a signal to display ELF CHECK OKJ and shifts to intraocular pressure measurement mode. CPU2
6, when the judgment signal is not output from the AND circuit 46 for even one step, the transition to the intraocular pressure measurement mode is canceled and a message ``Poor operation (unable to measure); please contact the service center.'' is displayed. A signal to cause the display 48 to perform is output to the display 48.

Although the embodiments have been described above, the present invention is not limited to this, and the flow velocity can also be adopted as the state quantity of the fluid.
In that case, a flow rate sensor is used instead of a pressure sensor.

(Effects of the Invention) According to the non-contact tonometer according to the present invention, the self-check circuit automatically operates at the same time as the power is turned on to check whether the fluid discharge means is operating normally or not, and to check whether the state quantity changes. Since it is possible to check whether the detection circuit is working properly, it is possible to save time and effort in operation, and
This has the effect of preventing forgetting to check.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of a non-contact tonometer as an intraocular pressure 811J 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 FIG. 2 is a diagram showing the correlation between the detection output and the amount of detected light used to explain the intraocular pressure measurement. 1...Cylinder installation V! 1 2...Cornea 3...Ejection optical system 4...Detection optical system 11a...Pressure sensor 23...State quantity change detection circuit-secondary 26...CPU 27...Power switch 28 ...Measurement switch 29...Physical quantity 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 (3)

[Claims] (1) A fluid is discharged from the fluid discharge means toward the cornea of the eye to be examined, and while deforming the cornea, a change in the state quantity of the fluid corresponding to the intraocular pressure of the eye to be examined is detected by a state quantity change detection circuit; , a non-contact tonometer that detects a physical quantity corresponding to the amount of deformation of the cornea in sequential correspondence with a change in the state quantity, and measures an intraocular pressure value based on the correlation between the physical quantity and the state quantity, A non-contact tonometer characterized by being provided with a self-check circuit that automatically checks the operation of the state quantity change detection circuit, including the operation of the fluid discharge means, when the power is turned on. (2) The fluid discharge means includes a cylinder device, and the state quantity change detection circuit includes a pressure sensor that detects the pressure inside the cylinder of the cylinder device, and a pressure sensor that detects the pressure inside the cylinder of the cylinder device. and an address generation unit that generates addresses for sequentially storing physical quantities, and the self-check circuit includes a fluid discharge circuit that checks whether the pressure value detected by the pressure sensor matches a predetermined reference pressure value. means operation check system, an address generator operation check system that checks whether the address matches a predetermined reference address value, and the state quantity change detection circuit and the 2. The non-contact tonometer according to claim 1, further comprising determining means for determining whether the operation with the fluid discharge means is normal or abnormal. (3) The non-contact tonometer according to claim 1, wherein the state quantity is a flow rate of the fluid.