JPH07124122A - Tonometer - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a tonometer which is safe and easy to use, and which can measure intraocular pressure with high accuracy without causing discomfort or fear to a subject. [Configuration] X-axis stage 11 driven by motor 13
Moves at a constant velocity toward the eye to be inspected, and the load sensor 6 and the pressure rod 5 reciprocate back and forth (constant velocity motion) via the cam 9 and the spring 7 by the drive of the motor 10 on the X-axis stage 11. , The pressure rod 5 from above the eyelid 1 to the cornea 3 of the eyeball 2.
The part is repeatedly pressed multiple times. The load amount of the repulsive force from the eyeball 2 is detected by the load sensor 6, and the CPU obtains the intraocular pressure from the time change of the load amount. The CPU identifies the presence or absence of mechanical influence of the eyelid in the time change of the detected load amount based on the difference in elastic constant between the eyelid and the eyeball of the eye to be inspected, and the load amount when it is determined that there is no influence. The intraocular pressure is calculated from the time change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tonometer for measuring intraocular pressure, and more particularly, to indirectly pressurize an eye to be inspected from above the eyelid and detect a repulsive force load against the pressurization to measure the intraocular pressure. The present invention relates to a load detection type tonometer.

[0002]

2. Description of the Related Art As a conventional intraocular pressure measuring method, a contact type and a non-contact type are known. In the contact type, the measuring unit of the device is brought into direct contact with the eyeball to obtain the intraocular pressure from the pressing force required to obtain a certain amount of deformation.

The measurement principle of a conventional contact (applanation) tonometer will be described. As shown in FIG. 4, when a ball having an external pressure of P0, an internal pressure of P1 and a radius R is pushed by a pressure rod, and the contact area between the ball and the pressure rod is A, the force applied to the pressure rod. f
Is expressed by f = (P1−P0) A, press the sphere with a pressure rod so that the contact area A is constant, and measure the force f applied to the pressure rod at that time. The difference (P1-P0) can be known.
When the sphere shown in FIG. 4 is replaced with an eyeball, the difference between the internal pressure and the external pressure (P1-P0) corresponds to the intraocular pressure.

On the other hand, in the non-contact type, in many cases, air is jetted onto the surface of the cornea and the deformation of the cornea is measured mainly by an optical method.

Further, in the alignment in the contact tonometer, a fluorescent agent is applied to the eye to be inspected, and usually blue light is irradiated,
The examiner observes the fluorescence from the fluorescent agent with a slit lamp microscope to check whether the pressed area reaches a predetermined area. On the other hand, in the non-contact tonometer, the alignment is performed using the specular reflection light from the cornea.

[0006]

At present, the contact tonometer is highly reliable, but since a part of the device is brought into direct contact with the cornea, the cornea is damaged unless the examiner is proficient in the operation. In addition, since an anesthesia drug is applied to the cornea before the measurement, a general person who does not have a license of a medical worker cannot easily measure the intraocular pressure like the body temperature and the blood pressure.

On the other hand, in the non-contact tonometer, the risk of corneal damage is lowered, but since air is jetted into the cornea, there is a problem that the subject feels discomfort and fear. That is, even though it is non-contact, there is no difference from the contact type in that the machine does not directly touch the cornea and stress is directly applied to the cornea during measurement.

Therefore, an object of the present invention is to solve the above problems, to use it safely and easily, and to measure the intraocular pressure with high accuracy without giving discomfort or fear to the subject. An object of the present invention is to provide a tonometer that can be configured easily and inexpensively.

[0009]

In order to solve the above-mentioned problems, according to the tonometer of the present invention, a pressurizing body for pressurizing the eyeball of the eye to be inspected from above the eyelid, and the pressurizing body mechanically A load sensor that is coupled and detects a load amount of repulsive force of the eyeball with respect to pressurization of the pressurizing body, and moves the pressurizing body and the load sensor at a constant velocity toward the eye to be inspected, A driving mechanism for performing pressurization, and an arithmetic processing means for obtaining the intraocular pressure from the time change of the load amount of the repulsive force detected by the load sensor when the eyeball is pressed by driving the driving mechanism. Having the arithmetic processing means, based on the difference between the elastic constants of the eyelid and the eyeball of the eye to be inspected, identifies the presence or absence of mechanical influence of the eyelid in the time change of the detected load amount, and there is no influence. Intraocular pressure from the time change of load amount when identified It was configured to determine.

[0010]

According to this structure, the pressure member and the load sensor are moved at a constant velocity toward the eye to be inspected by the drive of the drive mechanism to cause the pressure body to press the eyeball of the eye to be inspected from above the eyelids. The load amount of the repulsive force of the eyeball with respect to the pressurization is detected by the load sensor, and the arithmetic processing means obtains the intraocular pressure from the time change of the detected load amount. Here, since the eye pressure is measured by pressing the eyeball over the eyelids, the measurement can be performed without giving the subject a feeling of discomfort or fear, and without using an anesthetic.

Further, the arithmetic processing means discriminates the presence or absence of the mechanical influence of the eyelid on the temporal change of the detected load amount, and when the eyelid is discriminated as having no influence, the intraocular pressure is obtained from the temporal change of the load amount. The accuracy of measurement can be improved by eliminating the mechanical influence of the eyelids.

[0012]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows the mechanical structure of the tonometer of the embodiment. In FIG. 1, reference numeral 16 is a base of the tonometer, and a moving base 15 is provided on the base 16, and the position can be adjusted by moving the joystick 14 provided on the moving base 15 back and forth and left and right. ing.

A cylindrical eyeball base 4 is provided on the front end of the base 16. The subject fixes the eyeball 2 by contacting the eye to be inspected with the front surface of the eyeball fixing base 4 with the eyelid 1 closed. The front surface of the contact portion of the eyelid 1 of the eyeball fixing base 4 is a concave surface having a radius of curvature substantially equal to the radius of curvature of the portion of the eyeball 2 other than the cornea 3 plus the thickness of the eyelid. Then, the hole 4a of the cylindrical eyeball fixing base 4
Has a nearly circular shape, and its diameter is slightly larger than the diameter of the corneal portion.

A pressure rod 5 is arranged at the center of the hole 4a of the eyeball base 4, and the pressure rod 5 is mechanically connected to a load sensor 6. The load sensor 6 is provided so as to be slidable back and forth on the frame 11a fixed on the X-axis stage 11, and the holder 6 fixed to the rear end thereof.
It is biased rearward by a spring 7 stretched between a and the frame 11a. A shaft 8 is planted in the holder 6a, and the shaft 8 is attached to the outer periphery of a cam 9 fixed to a drive shaft of a motor 10 fixed on the frame 11a by a rearward biasing force of a spring 7. Pressed.

When the motor 10 is driven, the driving force of the motor 10 and the spring 7 are passed through the cam 9, the shaft 8 and the spring 7.
The elastic force of the load sensor 6 causes the load sensor 6 to reciprocate back and forth along the axial direction of the hole 4a together with the pressing rod 5. In particular, the shape of the cam 9 is devised so that the pressure rod 5 and the load sensor 6 reciprocate at a constant speed while keeping the rotation speed of the motor 10 constant.

Further, the pressure rod 5, the load sensor 6, the spring 7, the shaft 8, the cam 9 and the motor 10 for reciprocating the pressure rod 5.
The X-axis stage 11 equipped with a drive mechanism consisting of is provided slidably on the moving table 15 in the X-axis direction (front-back direction) coinciding with the axial direction of the hole 4a, and is fixed on the moving table 15. The motor 13 is driven to move forward and backward through the micrometer 12 at a speed substantially lower than the speed of the reciprocating motion.

Next, FIG. 2 shows the configuration of the control system of the tonometer. In the configuration of FIG. 2, the signal from the load sensor 6 is amplified by the amplifier circuit 17, and the A / D conversion circuit 18
Is converted into a digital signal by the CPU, input to the CPU 19 including a microprocessor, and processed. CP
U19 performs arithmetic processing for obtaining the intraocular pressure based on the input signal and controls the driving of the motors 10 and 13 via the motor drive circuits 20 and 21 to reciprocate the pressure rod 5 and the load sensor 6 described above. , X-axis stage 11 is moved.

Next, the operation of measuring the intraocular pressure with the above configuration will be described.

At the time of measuring the intraocular pressure, under the control of the CPU 19, the X-axis stage 11 is moved forward at a low speed (constant linear motion) by the drive of the motor 13, and the motor 1 is driven.
By driving 0, the pressure bar 5 reciprocates back and forth at a speed higher than the forward speed of the X-axis stage 11 together with the load sensor 6. Then, the pressure rod 5 approaches the eyeball 2 while reciprocating at a constant speed, and presses the cornea 3 portion of the eyeball 2 from above the eyelid 3. The load amount of the repulsive force with respect to this pressurization is detected by the load sensor 6, the detection signal is amplified, A / D converted, and input to the CPU 19. The CPU 19 performs arithmetic processing based on the input signal, and calculates the intraocular pressure from the time change of the load amount of the repulsive force as described later. Where X
By repeating the reciprocating motion of the pressure rod 5 while the shaft stage 11 moves forward at a low speed, the eyeball 2 is pressurized a plurality of times, and the load amount of the repulsive force is detected a plurality of times. This can improve the accuracy of measurement.

When the eye to be inspected is pressed from above the eyelid 1 with the pressure rod 5, in order to measure the intraocular pressure correctly,
We must consider the mechanical effects of eyelid 1. When the eyelid 1 is regarded as an elastic body, the repulsive force from the eyelid 1 changes according to the displacement of the pressure rod 5. However, if the portion of the eyelid 1 sandwiched between the cornea 3 of the eyeball 2 and the pressure rod 5 is continuously pressed, the eyelid 1 will eventually be deformed (compressed), and the repulsive force from the eyelid 1 will be constant, The force pushed by the pressure bar 5 directly deforms the eyeball 2 and the cornea 3.

Therefore, the displacement x of the pressure bar 5 and the eyelid 1
The graph of the relationship between the repulsive force f from the eyeball 2 and the cornea 3 is as shown in FIG. That is, in FIG. 3, when the displacement of the pressure rod 5 is up to x0, the pressure rod 5 is
The eyelid 1 is compressed by being pressed by,
When the displacement becomes larger than x0, the eyelid 1 is completely compressed, and therefore the repulsive force f with respect to the displacement x of the pressure rod 5 is f.
The change of is a reflection of the repulsive force from only the eyeball 2. Therefore, if the repulsive force from only the eyeball 2 is measured, the intraocular pressure can be measured with high accuracy.

Here, since the elastic constant of the eyelid 1 is usually smaller than the elastic constant of the eyeball 2, when the load amount measured by the load sensor 6 is differentiated by the displacement of the pressure bar 5, the differential value is the eyelid. Small when the mechanical effect of 1 is large,
It increases when the mechanical influence is small.

Therefore, when a threshold value is set for this differential value and the measured differential value becomes larger than the threshold value, the change in the load amount of the repulsive force f with respect to the displacement x (as will be described later). It is judged that the mechanical effect of the eyelid 1 on (equal to the change with time) has disappeared, and in that case the intraocular pressure is measured by performing appropriate processing such as associating the maximum value of the differential value measured with the intraocular pressure. be able to.

Therefore, the threshold value of the differential value is set in the memory of the CPU 19, and the CPU 19 compares the differential value of the detected load amount with the threshold value, and determines whether the eyelid 1 is smaller than the threshold value or not. The presence or absence of mechanical influence is identified, and the intraocular pressure is obtained from the differential value when it is identified as having no influence. In this way, the mechanical influence of the eyelids can be eliminated and the intraocular pressure can be measured with higher accuracy.

In the above description, the load amount that reflects the repulsive force from the eyelid 1 and the eyeball is differentiated by the displacement of the pressure rod 1, but normally, in order to obtain the differential value, it is better to differentiate with respect to time. It is convenient. Therefore, by moving the pressure bar 5 at a constant speed, differentiation by displacement can be made equivalent to differentiation by time. That is, the differential value of the repulsive force load amount is a differential value with respect to time, and the differential value,
That is, the intraocular pressure is obtained from the time change of the load amount of the repulsive force. This can facilitate the process of obtaining the intraocular pressure.

Considering the radius of curvature of the concave surface that contacts the eyelid 1 of the eyeball base 4 in the above structure, the radius of curvature of the cornea 3 is about 7.5 mm, and the radius of curvature of the eyeball portion other than the cornea is It is about 9 mm when converted from the axial length, and the respective radii of curvature are different. Therefore, the radius of curvature of the concave surface in contact with the eyelids 1 on the eyeball base 4 is adjusted to the radius of curvature of the eyeball portion other than the cornea plus the thickness of the eyelids as described above. By doing so, the eyeball 2 is supported by the entire concave surface, so that the eyeball 2 can be fixed without giving discomfort to the subject. Further, attaching a cushioning material such as a sponge to the concave surface of the eyeball fixing base 4 is also an effective method for alleviating the discomfort of the subject.

The diameter of the hole 4a of the cylindrical eyeball base 4 is set to be slightly larger than the diameter of the cornea 3 as described above. With such a structure, the subject can fix the eyeball base 4
When the cornea 3 comes into contact with the concave surface of the cornea 3 via the eyelid 1, it feels uncomfortable. Therefore, the user tries to bring the cornea 3 to the portion of the hole 4a having no contact surface, so that the portion of the cornea 3 is naturally accommodated in the hole 4a. The alignment can be easily performed by configuring the eye to be inspected and the tonometer in alignment with the cornea 3 portion accommodated in the hole 4a.

Further, the eyeball base 4 is made of a transparent material. By doing so, the examiner can directly observe the fixed state of the eyeballs, which facilitates alignment.

The pressure bar 5 is a hole 4a in the eyeball base 4.
It is arranged on the central axis of, and moves at a constant speed along the central axis. In this way, the pressure bar 5 can be brought into contact with the apex of the cornea 3 of the eyeball 2 fixed by the eyeball fixing base 4, and the measurement can be performed with higher accuracy.

The drive mechanism for reciprocating the pressure bar 4 and the load sensor 6 at a constant speed is not limited to the above-mentioned mechanism, but a generally known mechanism combining a motor, a gear and a cam, A mechanism that combines a push-pull solenoid and an optical position detector is also conceivable.

[0032]

As is apparent from the above description, according to the tonometer of the present invention, the pressurizing body and the load sensor which are mechanically coupled to each other are moved at a constant speed toward the eye to be inspected. The eyeball of the eye to be inspected is pressed from above the eyelid, the load amount of the repulsive force of the eyeball with respect to the pressurization is detected by the load sensor, and the intraocular pressure is calculated from the time change of the detected load amount by the arithmetic processing means. Since the eye pressure is measured by applying pressure to the eyeball from above the eyelids, the measurement can be safely and easily performed without giving the subject a feeling of discomfort or fear, or requiring an anesthetic. Further, the arithmetic processing means identifies the presence or absence of the mechanical influence of the eyelid on the time change of the detected load amount, and obtains the intraocular pressure from the time change of the load amount when it is determined that there is no influence, so the eyelid dynamics It is possible to obtain an excellent effect that it is possible to improve the measurement accuracy by eliminating the physical influence.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional side view showing a mechanical configuration of an embodiment of the tonometer of the present invention.

FIG. 2 is a block diagram showing a configuration of a control system of the same tonometer.

FIG. 3 is a graph showing the relationship between the displacement of the pressure bar and the load amount when measuring intraocular pressure in the same tonometer.

FIG. 4 is an explanatory diagram of a measurement principle of a conventional contact type (applanation type) tonometer.

[Explanation of symbols]

 1 Eyelid 2 Eyeball 3 Corneal 4 Eyeball Fixing Base 5 Pressure Rod 6 Load Sensor 7 Spring 8 Axis 9 Cam 10 Motor 11 X Axis Stage 12 Micrometer 13 Motor 14 Joystick 17 Amplification Circuit 18 A / D Conversion Circuit 19 CPU

Claims (6)

[Claims] 1. A pressurizing body for pressurizing the eyeball of the eye to be inspected from above the eyelid, and a load mechanically coupled to the pressurizing body for detecting the amount of repulsive force of the eyeball against the pressurization of the pressurizing body. A sensor, a drive mechanism that causes the pressurizing body and the load sensor to move at a constant speed toward the eye to be inspected, and pressurizes the eyeball by the pressurizing body, and pressurizes the eyeball by driving the drive mechanism. And an arithmetic processing means for obtaining the intraocular pressure from the time change of the load amount of the repulsive force detected by the load sensor when performed, the arithmetic processing means, in the difference in the elastic constants of the eyelid and the eyeball of the eye to be examined. On the basis of the above, the presence or absence of the mechanical influence of the eyelids in the time change of the detected load amount is identified, and the intraocular pressure is obtained from the time change of the load amount when it is identified that there is no effect. Tonometer. 2. The drive mechanism repeatedly performs a plurality of reciprocating motions of a constant velocity motion of the pressure body and the load sensor toward the eye to be inspected and a motion in the opposite direction, and thereby the load amount of the repulsive force is increased. 2. The detection is performed a plurality of times.
The tonometer described in. 3. The tonometer according to claim 2, further comprising a drive mechanism that moves the drive mechanism toward the subject's eye at a constant speed lower than the reciprocating speed. 4. A cylindrical eyeball fixing base for fixing the eyeball by contacting the eyelid of the eye to be inspected, and the front surface of the eyeball fixing base to contact the eyelid has a radius of curvature of an eyeball other than the cornea of the eye to be inspected. The hole is formed in a concave surface that is approximately equal to the radius of curvature obtained by adding the thickness of the eyelid to the radius of curvature of the portion, and the hole of the cylindrical eye fixation base is a substantially circular shape whose diameter is slightly larger than the diameter of the corneal portion. The tonometer according to any one of claims 1 to 3, characterized in that the eye to be inspected and the tonometer are aligned so that the corneal portion of the eye to be inspected is accommodated. 5. The tonometer according to claim 4, wherein the pressurizing body is arranged on a central axis of the hole of the eyeball fixing base and moves at a constant speed along the central axis. 6. The tonometer according to claim 4 or 5, wherein the eyeball base is made of a transparent material.