JPS61122838A - 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] The present invention deforms the cornea of the subject's eye with a fluid such as air, detects the physical quantity indicating the deformation and the flow velocity of the fluid, and indicates the deformation of the cornea. This invention relates to a non-contact tonometer that measures intraocular pressure by determining a correlation function curve between a physical quantity and a fluid flow rate.

Traditionally, as a non-contact tonometer, for example,
What is disclosed in Japanese Patent No. 4-38437 is known.

The device disclosed in Japanese Patent Publication No. 54-38437 includes a fluid pulse generator as a fluid generating means for generating fluid for deforming the cornea of the eye to be examined, and an injection optical system that emits detection light toward the cornea of the eye to be examined. With the system.

It includes a light receiving optical system that receives the detection light that is emitted from the emitting optical system and passes through the cornea of the eye to be examined.

In this conventional device, when a fluid is flowed toward the cornea of the subject's eye, the cornea of the subject's eye deforms from a convex state to a flat state to a concave state as the flow pressure of the fluid increases; This technology utilizes the phenomenon that when the fluid pressure is reduced, the cornea of the eye to be examined returns from a concave state to a flat state to a convex state. It is set so that the amount of light received by the light-receiving optical system is maximum when the light-receiving optical system is in this state. The fluid pulse generator is designed to generate a fluid that describes a predetermined fluid pressure characteristic curve with time t as a parameter, as shown by reference numeral A in FIG. The deformation and recovery time of the optometric cornea has a correlation with the intraocular pressure, and the intraocular pressure can be measured using the time t as a parameter. The amount of detected light reflected from the cornea of the subject's eye by the light-receiving optical system is defined as the time t, 1 from when the fluid according to the fluid pressure characteristic @A starts flowing until the cornea of the subject's eye, which is in a convex state, deforms to a flat state. It is measured as the time until it reaches its maximum, and that time is converted into intraocular pressure. That is, the flow pressure Pe of the fluid at time 1
This process has the same meaning as calculating from the characteristic curve A and converting the flow pressure Pe into intraocular pressure. In this conventional method, the time interval between the formation of both planar shapes when the cornea of the subject's eye deforms from a convex state to a planar state to a concave state and then returns from the concave state to a planar state is measured, and based on this, Intraocular pressure can also be determined. Note 2: This first O
In @, the symbol B indicates the received light amount characteristic curve of the light receiving optical system, and the symbol Pmax indicates the maximum flow pressure of the fluid.

By the way, this conventional non-contact tonometer disclosed in Japanese Patent Publication No. 54-38437 is.

The flow pressure of the fluid with respect to time is shown in Figure 10.
1IA is an essential condition, and if the flow pressure characteristic curve A of the fluid is different for each measurement, it has the disadvantage that it directly causes an error in the measurement of intraocular pressure.
Conventional non-contact tonometers have the problem of improving the accuracy of measuring intraocular pressure.

The present invention has been made in view of the problems of the prior art described above, and its purpose is to provide a non-contact tonometer that can further improve the accuracy of measuring intraocular pressure. It is about providing.

The present invention was made based on the fact that there is a direct correlation between fluid flow velocity and intraocular pressure. In order to give the same, a fluid discharge means for discharging fluid to the cornea of the eye to be examined, a corneal deformation detection means for detecting a physical quantity indicating the deformation of the cornea of the eye to be examined, and a flow rate of the fluid having a correlation with the intraocular pressure are provided. A correlation function curve between a physical quantity indicating deformation of the cornea of the subject eye and the flow velocity is established based on information from the flow velocity detection means, the corneal deformation detection means, and the flow velocity detection means, and a preset value of the physical quantity is established. The present invention further includes intraocular pressure conversion means for determining a flow velocity value corresponding to the correlation function curve from the correlation function curve and converting the determined flow velocity value into an intraocular pressure value.

Two Wildebeest Traveling Figure 1 shows the first embodiment of the non-contact tonometer according to the present invention. The optical system 4 is a detection optical system. The fluid discharge means 1 is a barrel that discharges fluid to the cornea 2 of the eye to be examined (hereinafter referred to as the cornea) in order to deform the cornea 2. This fluid discharge means 1 is
It is roughly composed of a rotary solenoid 5, a cylinder 6, and a rotary solenoid drive circuit 7, and 8 is a drum attached to the rotary solenoid 5.

The cylinder 6 has a cylinder tube section 9 and a nozzle tube section 10. A piston 11 is provided in the cylinder portion 9 so as to be able to reciprocate, and the piston 11 is connected to the drum 8 of the rotary solenoid 5 via a piston rod 12. The nozzle barrel 10 extends straight toward the cornea 2, and fluid is discharged from the nozzle barrel 10 by the reciprocating movement of the piston I2. The on/off conditions for the rotary solenoid drive circuit 7 will be described later.

The cornea 2 is deformed by the fluid flow pressure, and the fluid flow pressure increases as the flow velocity increases,
The cornea 2 changes from a convex state to a flat state to a concave state as f'i increases due to the increase in flow velocity. Reference numeral C indicates a state in which the cornea 2 has undergone deformation. The symbol m indicates the amount of deformation, and the amount of deformation m is the center I! of the cornea 2! If the apex of the cornea 2 existing on 01 and before undergoing deformation is 02, and the apex of the cornea C existing on the center l1A01 of the cornea 2 and undergoing deformation is 03, then the apex A(]+ This indicates the distance from the vertex OB.

The exit optical system 3 and the detection optical system 4 constitute a physical quantity detecting means indicative of corneal deformation that photoelectrically detects the deformation amount m of the cornea 2. The exit optical system 3 is composed of a light source 13, a condenser lens 14, an aperture 15, and a projection lens 16, and 04 is an optical axis of the exit optical system 3. The diaphragm 15 is located between the condensing lens 14 and the projecting lens 16, and is located at the focal point of the lens 16.
After the emitted light from No. 3 is condensed by the condenser lens 14, it is condensed by the aperture 15.
The detection light is made up of a parallel light beam and is emitted to the cornea 2 through the projection lens 16. The detection optical system 4 is.

It is composed of an imaging lens 17, an aperture 18, and a photoelectric converter 19, and the photoelectric conversion circuit 19 is composed of a light receiving element 20 and an amplifier circuit 21. , the detection light emitted from the exit optical system 3 and passing through the corner [2 is received by the light receiving element 20 via the imaging lens 17 and the diaphragm 18, photoelectrically converted, and transmitted through the amplifier circuit 21 to deform the cornea 2. A signal corresponding to the amount of corneal deformation corresponding to the amount m is output.

22 is a flow rate detection circuit as a flow rate detection means, and this flow rate detection circuit 22 includes a flow rate sensor section 23 and a flow rate detector 24.
The ultrasonic beam displacement method is used here. The flow rate sensor section 23 includes a wave transmitter 24'
and a wave receiver 25.25 are arranged so as to face the peripheral wall of the nozzle cylinder 10, and the wave receiver 25.25
are arranged in parallel in the axial direction of the nozzle cylinder portion 10.

The transmitter 24' is adapted to be received by the receivers 25, 25, and the deflection of this ultrasonic beam is determined by the receiver 2.
This is expressed as the voltage level of the output of 5.25 and the difference therebetween. The flow rate detector 24 is connected to a delivery device 25.25.
The system receives the output signal of , calculates the voltage difference between the Okayama force signals, and outputs this as a flow velocity detection signal.

2G is a measurement circuit as an intraocular pressure value conversion means, and this measurement circuit 26 includes a photoelectric conversion circuit 19 and a flow rate detection circuit 22.
A correlation function curve between the amount of detection light and the flow velocity of the fluid corresponding to the amount of deformation m of the cornea 2 is established based on the information included in the detection signal output from the It has a function of determining a flow velocity value corresponding to a value from this correlation function curve and converting the determined flow velocity value into an intraocular pressure value.The circuit configuration thereof will be explained based on FIG. 2.

As shown in FIG. 2, the measurement circuit 26 includes a central processing circuit (hereinafter abbreviated as CPU) 27 and a memory circuit 28.
and a changeover switch circuit 29. cpu27
constitutes the core of this measurement circuit 26, and its function will be explained in relation to other circuit components. The changeover switch circuit 29 is conceptually shown in FIG. 2 as a contact switch, and here includes three changeover switches 30, 31. 32 has two switching contacts A and B.

In addition, the measurement circuit 26 includes two sampling circuit systems that sample data for establishing a correlation function curve. One sampling circuit system consists of a sample-and-hold circuit 33, an addition circuit 34, a reference voltage generation circuit 35, a comparison circuit 36, and a pulse generation circuit 37.
, an address counter circuit 38 and an OR circuit 39. Sample and hold circuit 3
3, a flow velocity detection signal from the flow velocity detection circuit 22 is inputted, and this sample-and-hold circuit 33 has a control terminal, and when a pulse signal is inputted to this control terminal, the flow velocity at that point is detected. The voltage of the detection signal is sampled and held until the next pulse signal is input to the control terminal. The adder circuit 34 adds the voltage values of the sample-and-hold circuit 33 and the base 4!1 voltage generating circuit 35, and outputs the voltage of the added voltage value. The comparison circuit 36 has the output voltage of the addition circuit 34 inputted to its positive terminal, and the flow velocity detection signal inputted to its negative terminal.
When the voltage of the flow velocity detection signal becomes higher than the output voltage of the adder circuit 34, its output becomes high level. When the output of the comparison circuit 36 becomes high level, a single pulse signal is output from the pulse generation circuit 37, and the pulse generation circuit 37 is constituted by, for example, a monostable multivibrator.

The address counter circuit 38 is connected to this pulse generating circuit 37.
pulse signals are counted, and address information, which is the count value, is transmitted to the memory circuit 28 through the changeover switch 32. The pulse signal of the pulse generation circuit 37 is also input to the control terminal of the sample-and-hold circuit 33 through an OR circuit 39, and the pulse signal is input to this OR circuit 39 from the CPU 27. ing.

That is, this sampling circuit system increments the address counter circuit 38 at every predetermined pressure step in the process of increasing the fluid flow velocity, and makes the output correspond to the flow velocity data and obtains it as address information.

The other sampling circuit system is composed of a sample-and-hold circuit 40 and an analog-to-digital conversion circuit 4.

The sample-and-hold circuit 40 includes a photoelectric converter 1.
The sample-and-hold circuit 40 has a control terminal, and when a pulse signal is input to this control terminal, the detection signal at that point is input. The voltage value is sampled and this voltage value is held until the next pulse signal is input to the control terminal. The voltage value held by the sample-and-hold circuit 40 is converted into a digital amount by an analog-to-digital conversion circuit 41, and is input to the memory circuit 28 via the changeover switch 31. A pulse signal is input to the control terminal of the sample-and-hold circuit 40 from an OR circuit 39. Therefore, in this sampling circuit system, at the same time as the flow velocity data is updated, reflected light amount data corresponding to the angular 1ull deformation amount corresponding to the flow velocity data is sampled.

The measuring circuit 26 further performs a rotation i! for stopping the rotary solenoid 5. ! It has a system. This circuit system is composed of a comparison circuit 42, a reference voltage generation circuit 43, and a pulse generator 44. The output voltage from the reference voltage generation circuit 43 is input to the comparator circuit 42 at its plus terminal, and the light 1! is input at its minus terminal. A detection signal from the conversion circuit 19 is input. The output voltage of the reference voltage generation circuit 43 is the same as that of the photoelectric conversion circuit 19 when the amount of deformation m of the cornea 2 is slightly before the maximum.
is set to the voltage of the detection signal from the comparator circuit 42.
The voltage of the detection signal is based on 4! I voltage generation times lol! When the output voltage exceeds the output voltage of 43, high level output is performed. When the output of this comparison circuit 42 changes from high level to low level, a single pulse signal is output from the pulse generation circuit 44. This pulse signal is input to the rotary solenoid drive circuit 7, and the rotary solenoid drive circuit 44 outputs a single pulse signal. The solenoid drive circuit 7 stops the rotorinoid 5 upon receiving this pulse signal.

Incidentally, a power switch, a start switch 45, and a display 46 (not shown) are connected to the CPU 27. First, when you turn on the power switch, this CPt
A changeover switch control signal is outputted from 127 to changeover switch circuit 29, changeover switch 30.degree. 31.32 is set to the B contact side, and memory circuit 28 is initialized. At the same time, a reset signal is input from the CPU 27 to the address counter 38, and the address counter 38 remains reset. After this, the CPU
The changeover switch control signal is outputted again from 27 to the changeover switch circuit 29, and the changeover switches 30, 31.3
2 is set on the A contact side.

In this state, if the start switch 45 is turned on or is turned on and there is a switch input to the CPU 27L, the CPU 27 reads this and performs the next process. First, a pulse signal is output to the OR circuit 39, and the sample-and-hold circuit 33.40 samples and holds the current voltage of the flow velocity detection signal and the voltage of the detection signal corresponding to the amount of corneal reflected light. . At the same time, current flow velocity data and light amount data are stored in the memory circuit 28. Note that, at this moment, the fluid is not discharged and the angle llI2 is not deformed accordingly, so the voltages of the flow velocity detection signal and the detection signal corresponding to the amount of corneal reflected light are both Ov. Therefore, Ov is applied to the negative terminal of the comparison circuit 36, and the output voltage of the reference voltage generation circuit 35 is applied to the positive terminal since it operates at the same time as the power switch is turned on, so the output of the comparison circuit 36 is It is at a low level. Further, the output of the sample-and-hold circuit 40 is also Ov. Next, the address counter 38 is reset, and then a drive control signal is input to the rotary solenoid drive circuit 7 to start operating the rotary solenoid 5.

After the rotary solenoid 5 starts operating.

Two sampling circuit systems sample light amount data corresponding to the amount of corneal deformation with respect to flow velocity data obtained in steps of a predetermined flow velocity, and the sampled data is stored in the memory circuit 28.

In this process, when the output of the comparator circuit 42 changes from high level to low level, the rotary solenoid 5 is stopped, and the increase in the fluid flow rate is stopped. Along with this, the increase in the voltage of the flow velocity detection signal stops, and after that, the comparison circuit 3
6 remains at a low level, data sampling is no longer performed.

Thereafter, after a predetermined time has elapsed by the timer of the CPU 27, a changeover switch control signal is input from the CPU 27 to the changeover switch circuit 29, and the changeover switch 3
0, 31.32 are set on the B contact side. And C.P.
U27 reads the sampled data in the memory circuit 285 and establishes a correlation function between the flow velocity data S and the detected light: tL corresponding to the corneal deformation amount m, as shown in FIG. 3, based on this sampled data. . In FIG. 3, 5IIla is the maximum value of the flow velocity, and L*aX is the maximum value of the amount of light. After establishing this correlation function, the CPU 27 determines the flow velocity corresponding to the amount of light corresponding to the amount of corneal deformation set in advance from this correlation rA number, and converts the determined flow velocity value into an intraocular pressure value. maximum value L+ia
The flow velocity values SH and SL at x are converted into intraocular pressure values. In addition, in Fig. 3, the solid line indicates the song $11H.
i and a dashed curve Lo are shown, but these curves 1iHi and Lo are for different corneas. Of course.

It goes without saying that the cornea according to the curve H1 has a higher intraocular pressure value than the cornea according to the curve 11Lo. After determining the intraocular pressure value, the CPU 27 causes the display 46 to display the intraocular pressure value.

By the way, as shown in FIG. 4, the cylinder 6 of this embodiment is provided with a fluid relief cylinder part 47, and this fluid relief cylinder part 47 is provided with an electromagnetic valve 48. Solenoid valve drive circuit 49 that opens valve 48
It is also possible to provide the cornea 2 to accelerate the relaxation of the fluid pressure applied to the cornea 2. In order to accelerate this fluid pressure relaxation, when the rotary solenoid drive circuit 7 receives a pulse signal from the pulse generation circuit 44 and the piston 11 is in the forward stroke, the piston 11 is moved backward. This can also be done by driving the rotary solenoid 5.

In addition, the photoelectric conversion circuit 19 and the flow rate detection circuit 22 are replaced, the photoelectric conversion circuit 19 is connected to the circuit system on the sample and hold circuit 33 side, and the flow rate detection circuit 22 is connected to the circuit system on the sample and hold circuit 40 side. It may also be configured to be connected to a circuit system. In this case, a correlation function is established as shown in FIG.

Furthermore, in this example, the ultrasonic beam deflection method was used to detect the flow velocity of the fluid, but there are other well-known techniques such as the ultrasonic propagation velocity variation method, the sing-around method, and the method using a constant temperature hot wire anemometer. can be adopted.

Next, a second embodiment of the non-contact tonometer according to the present invention will be described based on FIG. 6. Note that this second embodiment is
Since this embodiment has the same components as those in the first embodiment, the same components are given the same reference numerals as those in the first embodiment, and detailed explanation thereof will be omitted.

In FIG. 6, the cylinder 6 of the fluid discharge means 1 has a nozzle tube 10 extending in a direction perpendicular to the axis of the cylinder tube 9 and straight toward the cornea 2,
A flow rate sensor section 23 is attached to this nozzle cylinder part 10, and the fluid flows from the nozzle cylinder part 10 at an angle W! 42
It is designed to be emitted towards.

The exit optical system 3 biases the projection lens 50 and the infrared light emitting diode 51 so that the optical axis 04 of the projection lens 50 is parallel to the centerline axis 01 of the cornea 2 of the eye to be examined.
A light projecting lens 50 is provided. The infrared light emitting diode 51 is provided so that its light emitting center is located at the focal point of the light projecting lens 50, and the light projecting lens 50 is
A spot light consisting of a parallel light beam passes through the aperture A' and is ejected toward the cornea 2 as detection light. The detection optical system 4 has an imaging lens 52 and a photoelectric converter 53 biased, and the detection optical system 4 is emitted from the exit optical system 3 at a corner 1.
It has a function of receiving the detection light passing through [2], photoelectrically converting the detection light, and outputting a corneal deformation corresponding signal of the eye to be examined corresponding to the amount of corneal deformation of the eye to be examined. The imaging lens 52 is provided so that its optical axis O5 intersects with the optical axis 04, and the photoelectric converter 53 is provided at the focal position of the imaging lens 52, and the photoelectric converter 53 is provided at the focal position of the imaging lens 52 to detect the detection reflected by the cornea 2. The light is imaged on the photoelectric converter 53. For the photoelectric converter 53, a CCD linear sensor array with a -dimensional configuration is used here.

In FIG. 6, the symbol P1 indicates the detection light reflected by the cornea 2 of the eye to be examined before undergoing deformation, and the symbol P2
is the cornea C of the eye to be examined when deformed by the deformation ′jIkm
Here, a state is shown in which the detection light P1 is focused on the r1th component 54 of the photoelectric converter 53, and the detection light P2 is focused on the r1th component 54 of the photoelectric converter 53. The state of being imaged r2nd by M is shown. The time series output signal from the optical converter 53 is input to a detection circuit 55, and this detection circuit 55 has a function of outputting a voltage corresponding to the address information of each component 54. The output of this detection circuit 55 is configured to be input to a sample-and-hold circuit 40 and a comparison circuit 42 of the measurement circuit 26.

When the cornea 2 deforms by the deformation amount m, the imaging position of the detection light changes by Δr, and the change in the imaging position Δr
and the amount of deformation m have a corresponding relationship.

This change Δr in the imaging position can be understood as a voltage difference.

That is, data corresponding to the amount of corneal deformation is sampled based on the output voltage of the detection circuit 55.

In this embodiment, the exit optical system is configured to use a minute spot light, but it may also be configured to project a circular pattern or a lattice pattern onto the cornea and detect the amount of deformation thereof.

In this embodiment, the detection optical system is configured to utilize a one-dimensional change in the imaging position.

A two-dimensional configuration that detects changes in area of a circular pattern can also be used.

Furthermore, if the subject has corneal astigmatism, the position and amount of displacement of the reflected spot light differ along the corneal meridian direction, so in that case, for example, 1 along the corneal meridian direction.
It is preferable to arrange deformation detection optical systems every 60 degrees.

Next, a seventh embodiment of the non-contact tonometer according to the present invention will be described.
This will be explained based on FIGS. 9 to 9.

In this embodiment, the fluid discharge means 1 and the measurement circuit 24 have the same configuration as in the first embodiment, so illustration thereof is omitted. The exit optical system 3 is roughly composed of a light source 56, a condenser lens 57, a slit plate 58, and a projection lens 59.

An incandescent light bulb is used as the light source 56, the light source 56 is provided at the focal point of the condenser lens 57, and the slit plate 58 is provided between the condenser lens 57 and the projection lens 59. The slit plate 58 is provided with a dark blue long slit 60, and the detection light passing through the slit 60 is projected as slit projection light 61 toward the cornea 2 of the eye to be examined by the projection lens 59. The cornea 2 of the eye to be examined is cut by this Surin 1 - projection light 61 .

The detection optical system 4 is constructed as a microscope, and is roughly composed of an objective lens 62, a left eye optical system 63, and a right eye optical system 64. The left eye optical system 63 includes a variable magnification optical system 65, an imaging lens 66, an erecting optical system 67, a focusing plate 68, and an eyepiece 69, and the right optical system 64 includes a variable magnification optical system 70, an imaging lens 71, an erecting optical system 72, and a focusing plate 73
and an eyepiece lens 74, so that a slit-shaped cross section of the cornea 2 can be observed by the measurer. In the right eye optical system 64, a half mirror 75 is provided obliquely with respect to the optical axis of the right eye optical system 64 between a variable power optical system 70 and an imaging lens 71. A portion of the slit projection light reflected by the cornea 2 is.

The light is reflected by this half mirror 75, and an imaging lens 76 and an area sensor 77 are provided at the front in the reflection direction. This imaging lens 76 and area sensor 7
7 is arranged so as to satisfy the Scheinbruch principle with respect to the slit projection light beam. An area type CCD is used for the area sensor 77, and this area sensor 77 has at least three scanning lines. A conventional slit lamp can be used for the objective lens 62, the left eye optical system 63, and the right eye optical system 64, and the half mirror 75
The imaging lens 76 and the area sensor 77 can be housed in a case 78 as an optional configuration. cornea 2
The cross-sectional position of is adjusted to a predetermined position by the measurer using the left eye optical system 63 and the right eye optical system 64. Corner @2
The slit projection light reflected from the 1M image lens 76 is focused on the area sensor 77 as a corneal cross-sectional image. FIG. 8 shows this corneal cross-sectional image, and reference numeral C1 indicates the corneal cross-sectional image before the cornea 2 undergoes deformation;
2 shows a corneal cross-sectional image when the corner 111 [2 is deformed by the amount of deformation Δ, Lt+Lz, L-3 show scanning lines, and when the start switch is pressed, the area is divided by at least three scanning lines. The constituent elements of the sensor 77 are scanned, and by this scanning, the imaging position in the sense of which constituent element the corneal cross-sectional image is formed on is determined. Here, three images are formed in one unit! S'l
ls2 and Si are determined and inputted as an imaging position signal to the detection circuit 79, which detects the imaging position II! before deformation! A voltage corresponding to the address information of the element is input as a signal to one sample-and-hole circuit of the measurement circuit. This scanning is performed at high speed, and the 1M image position changes from moment to moment while the cornea 2 is undergoing deformation, and the image position signal during the deformation process is sent to the detection circuit 79 from time to time. The output voltage from the detection circuit 79 is input to the sample-and-hold circuit 40. That is, the output voltage of this detection circuit 79 is sampled as corneal deformation amount data. Note that in FIG. 8, symbols Sv', Sz', and S*' are imaging positions when the cornea 2 is deformed by the amount of deformation Δ.

By the way, as a method for measuring the intraocular pressure of the cornea 2 of the eye to be examined, in order to eliminate the influence of the elastic force of the cornea itself and tear fluid on the measurement of the intraocular pressure, the cornea of the eye to be examined 2 is shaped into a circular plane with a diameter of 3.06 mm. There is an applanation tonometry method in which applanation is performed so that
The flow velocity of the fluid when Sf and Si' are aligned on a straight line as shown in FIG. 9 can be used.

Monthly lesson Iυ arc rose The present invention has the configuration as described above.

1 compared to those that measure intraocular pressure using time as a parameter.
Since measurement errors caused by time measurement can be eliminated, the accuracy of limiting pressure measurement can be improved accordingly.

In addition, in the conventional method, it is an essential condition that the fluid pressure with respect to time follows the fluid pressure characteristic surface l1AA, and if the fluid fluid pressure characteristic curve A differs for each edict, measurement errors will occur. However, according to the present invention, errors due to defects in design, manufacturing, and quality control have no direct effect on the accuracy of intraocular pressure measurement. Therefore, the design, manufacture, and quality control of the fluid discharge means can be facilitated.

In addition, even if there is a change in fluid pressure characteristics due to a change in fluid density due to a change in temperature, the present invention can directly adjust the corresponding pressure! Since it is added by 1, there is no effect.

In particular, the deformation process of the cornea of the subject's eye that is currently being side-vented is determined as a correlation function curve between the flow velocity value and the amount of corneal deformation, and the intraocular pressure value is measured based on this.

Accuracy is further improved compared to conventional methods.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing a first embodiment of a non-contact tonometer according to the present invention, and FIG. 2 is a measurement circuit that is an intraocular pressure value conversion means of the optical contact tonometer shown in FIG. FIG. 3 is a graph of a correlation function established by the measurement circuit shown in FIG. 2, and FIG. 4 is a block diagram of an example in which the fluid discharge means shown in FIG. 1 is modified. FIG. 5 is a graph of a correlation function obtained by modifying the measurement circuit shown in FIG. 2, FIG. 6 is a main part configuration diagram showing a second embodiment of the present invention, and FIG. A main part configuration diagram showing the three embodiments, FIGS. 8 and 9 are explanatory diagrams for explaining the embodiment shown in FIG. 7, and FIG. 10 explains the problems of the conventional optical contact tonometer. FIG. DESCRIPTION OF SYMBOLS 1...Fluid discharge means, 2...Cornea, 23...Flow velocity detection circuit (flow velocity detection means), 24...Measurement circuit (intraocular pressure value conversion means). Figure 3 Figure 4 Figure 5 Figure 7 Figure 8 Figure 9 Figure 10 tIt (time)

Claims (1)

[Scope of Claims] Fluid discharge means for discharging fluid to the cornea of the eye to be examined in order to impart deformation to the cornea of the eye to be examined; corneal deformation detection means for detecting a physical quantity indicating the deformation of the cornea of the eye to be examined; a flow velocity detection means for detecting a flow velocity of the fluid having a correlation with intraocular pressure; and establishing a correlation function curve between the physical quantity and the fluid flow velocity based on information from the corneal deformation detection means and the flow velocity detection means. and intraocular pressure value conversion means for determining a flow velocity value of the fluid corresponding to a preset value of the physical quantity from the correlation function curve and converting the determined fluid flow velocity value into an intraocular pressure value. A non-contact tonometer characterized by: