Non-contact type tonometer and operation method of non-contact type tonometer

Abstract

To provide a non-contact type tonometer capable of achieving both noise reduction and measurement accuracy in measuring an intraocular pressure, and an operation method of the non-contact type tonometer.SOLUTION: A non-contact type tonometer includes: a cylinder 34d; a piston 34f provided inside the cylinder 34d so as to freely move; an actuator (solenoid 34f) compressing air inside the cylinder 34d by moving the piston 34f inside the cylinder 34d by application of current; a nozzle 21b blowing the air compressed by the piston 34f to a subject eye E; and a current application control unit (measurement control unit 42) applying current to the actuator. The current application control unit executes first application processing for applying the current to the actuator in first current value, and when a switching condition predetermined during the first application processing is satisfied, the first application processing is switched to second application processing which causes current of a second current value higher than the first current value to be applied to the actuator.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a non-contact tonometer that measures the intraocular pressure of a subject's eye in a non-contact manner, and a method of operating the non-contact tonometer. [Background technology]

[0002] A non-contact tonometer that measures the intraocular pressure of a subject's eye without contact is known (see, for example, Patent Document 1). A non-contact tonometer is provided with a blowing mechanism that blows air from a nozzle onto the cornea of ​​the subject's eye. The non-contact tonometer thus measures the intraocular pressure of the subject's eye without contacting the cornea by driving the blowing mechanism to blow air from the nozzle onto the cornea of ​​the subject's eye, thereby deforming the cornea and detecting the state of deformation.

[0003] The spray mechanism of the non-contact tonometer described in Patent Document 1 is composed of a cylinder, a piston, a nozzle, a chamber, and a rotary solenoid. The piston is provided inside the cylinder so as to be freely movable. The nozzle is connected to the chamber and communicates with the inside of the cylinder (pressurizing chamber) through the chamber. The rotary solenoid is connected to the piston through a crank mechanism that converts its rotational motion into linear motion. The rotary solenoid rotates when a current is applied to it, and moves the piston inside the cylinder through the crank mechanism. As a result, air inside the cylinder compressed by the piston is ejected from the nozzle through the chamber toward the cornea of ​​the subject's eye. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-111333 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the non-contact tonometer described in Patent Document 1, a rotary solenoid is driven by current to blow air from a nozzle onto the cornea of ​​the subject's eye, but if the sound generated by the blowing mechanism when the rotary solenoid is driven is loud, it may cause discomfort to the subject. For this reason, there is a demand for reducing the sound generated by the blowing mechanism. In order to reduce the sound generated by the blowing mechanism, it is necessary to reduce the current value of the current applied to the rotary solenoid.

[0006] However, when the current value applied to the rotary solenoid is reduced, the piston moves as intended when the rotary solenoid first moves, but as the rotary solenoid continues to rotate, the force applied to the piston via the crank mechanism gradually weakens. This prevents the air pressure in the chamber from increasing, and the pressure of the air blown from the nozzle to the cornea of ​​the test eye may be insufficient. In this case, the intraocular pressure of the test eye cannot be measured accurately.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide a method of operating a contact tonometer and a non-contact tonometer that can achieve both quieter measurement of intraocular pressure and high measurement accuracy. [Means for solving the problem]

[0008] A non-contact tonometer for achieving the object of the present invention comprises a cylinder, a piston freely movable inside the cylinder, an actuator that moves the piston inside the cylinder by applying a current to compress the air inside the cylinder with the piston, a nozzle connected to the inside of the cylinder and blows the air compressed by the piston onto a test eye, and a current application control unit that applies current to the actuator, wherein the current application control unit executes a first application process that applies a current at a first current value to the actuator, and when a predetermined switching condition is satisfied during the execution of the first application process, switches from the first application process to a second application process that applies a current of a second current value higher than the first current value to the actuator.

[0009] According to this non-contact tonometer, in the first application process, a current of a first current value is applied to the actuator to achieve quiet operation, and when a specified switching condition is satisfied, the current value applied to the actuator is increased to a second current value, thereby preventing a decrease in the measurement accuracy of the intraocular pressure of the test eye.

[0010] In a non-contact tonometer according to another aspect of the present invention, the nozzle is in communication with the inside of the cylinder via a chamber that is in communication with the inside of the cylinder, and is provided with a pressure sensor that detects the pressure inside the chamber, and the current application control unit determines whether or not the switching condition is satisfied based on whether or not the pressure detected by the pressure sensor reaches a predetermined pressure threshold, thereby preventing a decrease in the pressure of the air blown onto the subject's eye.

[0011] In a non-contact tonometer according to another aspect of the present invention, a detection sensor is provided for detecting the amount of displacement of the actuator, and a current application control unit determines whether or not a switching condition is satisfied based on whether or not the amount of displacement detected by the detection sensor reaches a predetermined threshold value of the amount of displacement, thereby preventing a decrease in the pressure of the air blown onto the subject's eye.

[0012] In the non-contact tonometer according to another aspect of the present invention, the current application control unit increases the second current value stepwise while the second application process is being performed.

[0013] In another aspect of the non-contact tonometer of the present invention, the nozzle is connected to the interior of the cylinder via a chamber which is connected to the interior of the cylinder, and is equipped with a pressure sensor which detects the pressure inside the chamber, and the current application control unit gradually increases the second current value in response to an increase in the pressure detected by the pressure sensor during execution of the second application process.

[0014] In another aspect of the non-contact tonometer of the present invention, a detection sensor is provided for detecting the amount of displacement of the actuator, and the current application control unit gradually increases the second current value in response to an increase in the amount of displacement detected by the detection sensor during execution of the second application process.

[0015] In the non-contact tonometer according to another aspect of the present invention, the current application control unit stops the second application process when a predetermined specified time has elapsed since the start of the first application process.

[0016] A non-contact tonometer according to another aspect of the present invention includes a projection optical system that projects a light beam onto the subject's eye while air is being blown onto the subject's eye from the nozzle, and a light receiving optical system that receives the light beam reflected by the subject's eye while air is being blown onto the subject's eye from the nozzle and outputs an applanation signal, and when a current application control unit detects a peak of the applanation signal output from the light receiving optical system during execution of the second application process, the second application process is stopped. This allows a so-called soft puff that reduces the amount of air blown onto the subject's eye to be realized, thereby reducing the discomfort of the subject.

[0017] In a non-contact tonometer according to another aspect of the present invention, the actuator is a rotary actuator that moves a piston inside a cylinder via a crank mechanism.

[0018] To achieve the object of the present invention, a method of operating a non-contact tonometer includes a cylinder, a piston freely movable inside the cylinder, an actuator that moves the piston inside the cylinder by applying an electric current to compress the air inside the cylinder with the piston, and a nozzle that is connected to the inside of the cylinder and sprays the air compressed by the piston onto a test eye, and when applying an electric current to the actuator, a first application process is performed in which a current at a first current value is applied to the actuator, and when a predetermined switching condition is satisfied while the first application process is being performed, the first application process is switched to a second application process in which a current of a second current value higher than the first current value is applied to the actuator. Effect of the Invention

[0019] The present invention can achieve both quiet operation and high measurement accuracy during intraocular pressure measurement. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is a side view of a non-contact tonometer according to a first embodiment. [Diagram 2] 2 is a schematic top view of multiple types of optical systems in the measurement head as viewed from above. FIG. [Diagram 3] 4 is a schematic side view of multiple types of optical systems in the measurement head as viewed from the side. FIG. [Figure 4] FIG. 2 is a functional block diagram of a control device. [Diagram 5] 4 is a diagram showing an example of a current waveform that is a waveform of a current applied to a solenoid by a measurement control unit during a spraying process. FIG. [Figure 6] 4 is a flowchart showing a flow of an intraocular pressure measurement process of a subject's eye, which is an operation method of the non-contact tonometer of the first embodiment. [Figure 7] 1 is a graph showing an applanation waveform based on an applanation signal continuously output from an applanation detection optical system. [Figure 8] FIG. 11 is an explanatory diagram for explaining the stop timing of the second application process by the non-contact tonometer of the second embodiment. [Figure 9] 10 is a flowchart showing the flow of an intraocular pressure measurement process of a subject's eye by a non-contact tonometer according to a second embodiment. [Figure 10] FIG. 13 is an explanatory diagram for explaining a second application process executed by the non-contact tonometer of the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] [First embodiment] Fig. 1 is a side view of a non-contact tonometer 10 of a first embodiment. As shown in Fig. 1, the non-contact tonometer 10 measures the intraocular pressure value of a subject's eye E in a non-contact manner. The non-contact tonometer 10 includes a base 11, a face support unit 12, a moving mechanism 13, a measurement head 14, a monitor 15, and a control device 16.

[0022] In the figure, among the mutually orthogonal XYZ directions (three-axis directions), the Y direction is the up-down direction, the Z direction is the front-back direction (also called the working distance direction) moving toward or away from the subject (subject's eye E), and the X direction is the left-right direction perpendicular to both the up-down direction and the front-back direction. In addition, in the Z direction (front-back direction), the side approaching the subject's eye E (subject) is called the front side in the Z direction, and the side moving away from the subject's eye E (subject) is called the rear side in the Z direction.

[0023] A face support part 12 and a moving mechanism 13 are provided on the base 11 from the front side in the Z direction to the rear side in the Z direction. The base 11 supports a measuring head 14 via the moving mechanism 13 so as to be movable in the X, Y and Z directions.

[0024] The face support part 12 is fixed to the base 11. The face support part 12 includes a chin rest part 12a for receiving the subject's chin, a forehead rest part 12b against which the subject's forehead comes into contact, and a pair of supports 12c for supporting the forehead rest part 12b, and supports the subject's face.

[0025] The measurement head 14 measures the intraocular pressure of the subject's eye E in a non-contact manner by blowing air from the nozzle 21b toward the cornea Ec (see FIG. 2) of the subject's eye E to deform the cornea Ec and detect the deformed state.

[0026] The monitor 15 is, for example, a touch panel monitor, and is attached to the rear side of the measurement head 14. Under the control of the control device 16 described later, the monitor 15 displays various images including a photographed image (observation image) of the subject's eye E photographed by the measurement head 14, the measurement results of the intraocular pressure value of the subject's eye E, and a menu screen for performing various operations and settings.

[0027] Fig. 2 is a schematic top view of the multiple types of optical systems in the measurement head 14 as viewed from above (Y direction). Fig. 3 is a schematic side view of the multiple types of optical systems in the measurement head 14 as viewed from the side (X direction).

[0028] As shown in Figures 2 and 3, the measurement head 14 includes an anterior eye observation optical system 21, an XY alignment index projecting optical system 22, a fixation target projecting optical system 23, an applanation detection optical system 24, a Z alignment index projecting optical system 25, a Z alignment detection optical system 26, and a spraying mechanism 34.

[0029] The anterior-segment observation optical system 21 is used for observing the anterior segment of the subject's eye E and for XY-direction XY alignment of the measurement head 14 with respect to the subject's eye E. An anterior-segment illumination light source 21a (see FIG. 2) is provided in the anterior-segment observation optical system 21. Also, on the optical axis O1 of the anterior-segment observation optical system 21, there are provided an air-blowing nozzle 21b, an anterior-segment window glass 21c (see FIG. 3) that holds the tip of the nozzle 21b, a chamber window glass 21d, a half mirror 21e, a half mirror 21g, an objective lens 21f, and an image sensor 21i.

[0030] The anterior-segment illumination light sources 21a are provided at a plurality of positions around the anterior-segment window glass 21c, and directly illuminate the anterior segment of the subject's eye E.

[0031] The nozzle 21b is connected to a chamber 34a (see FIG. 3) of the spray mechanism 34, and sprays air onto the cornea Ec of the eye E to be examined.

[0032] An image of the anterior segment of the test eye E (image light from the anterior segment) passes outside the nozzle 21b, through the anterior segment window glass 21c, the glass plate 34b described below, the chamber window glass 21d, the half mirror 21g, and the half mirror 21e, and is formed on the light receiving surface of the imaging element 21i by the objective lens 21f.

[0033] The imaging element 21i is, for example, a CCD (Charge Coupled Device) type or CMOS (complementary metal oxide semiconductor) type image sensor. The imaging element 21i captures an image of the anterior segment incident on its light receiving surface to generate an imaging signal, and outputs the imaging signal to the control device 16. As a result, under the control of the control device 16, an observation image of the anterior segment of the subject's eye E based on the imaging signal output from the imaging element 21i is displayed on the monitor 15.

[0034] The anterior eye observation optical system 21 also guides the reflected light of the XY alignment index light projected from the XY alignment index projecting optical system 22 to the subject's eye E by the cornea Ec to the light receiving surface of the image sensor 21i. This reflected light passes through the nozzle 21b, the chamber window glass 21d, the half mirror 21g, and the half mirror 21e, and is imaged on the light receiving surface of the image sensor 21i by the objective lens 21f. As a result, an XY spot is formed on the light receiving surface of the image sensor 21i at a position according to the positional relationship (relative position) between the measurement head 14 and the cornea Ec in the XY direction. As a result, XY alignment detection can be performed to detect the relative position of the subject's eye E in the XY direction with respect to the measurement head 14.

[0035] The imaging element 21i captures an image of the XY spot formed on its light receiving surface, and outputs an imaging signal of the XY spot to the control device 16. As a result, under the control of the control device 16, the observed image of the anterior eye segment and the XY spot are superimposed and displayed on the monitor 15. Note that the monitor 15 also displays an alignment auxiliary mark.

[0036] The XY alignment index projection optical system 22 corresponds to the projection optical system of the present invention, and projects XY alignment index light, which corresponds to the light beam of the present invention, from the front onto the cornea Ec of the test eye E. This XY alignment index light is used for XY alignment of the measurement head 14 with respect to the test eye E. The XY alignment index light is also used to measure the intraocular pressure value of the test eye E. Hereinafter, the reflected light of the XY alignment index light by the cornea Ec will be simply abbreviated as "XY index reflected light."

[0037] The XY alignment index projection optical system 22 includes an XY alignment light source 22a, a condenser lens 22b, an aperture stop 22c, a pinhole plate 22d, a dichroic mirror 22e, and a collimator lens 22f (see FIG. 3). The XY alignment index projection optical system 22 shares the half mirror 21e with the anterior eye observation optical system 21.

[0038] The XY alignment light source 22a emits infrared light. The collimator lens 22f is disposed on the optical path of the XY alignment index projection optical system 22 so that its focal point coincides with the pinhole plate 22d. The infrared light emitted from the XY alignment light source 22a is focused by the condenser lens 22b, passes through the aperture stop 22c, and is guided to the hole of the pinhole plate 22d.

[0039] The infrared light passing through the hole of the pinhole plate 22d is reflected by the dichroic mirror 22e and guided to the collimator lens 22f, where it is collimated and then emitted from the collimator lens 22f to the half mirror 21e. This collimated infrared light is reflected by the half mirror 21e and travels along the optical axis O1 of the anterior eye observation optical system 21. As a result, the collimated infrared light passes through the half mirror 21g and the chamber window glass 21d, and then passes through the inside of the nozzle 21b, and enters the subject's eye E as XY alignment index light.

[0040] Although not shown, the XY alignment index light incident on the subject's eye E is reflected by the surface of the cornea Ec to form an XY spot. The aperture stop 22c is provided at a position conjugate with the corneal apex Ep of the cornea Ec with respect to the collimator lens 22f.

[0041] The fixation target projection optical system 23 projects a fixation target onto the subject's eye E. The fixation target projection optical system 23 has a fixation target light source 23a and a pinhole plate 23b (see FIG. 3). The fixation target projection optical system 23 also shares a dichroic mirror 22e and a collimator lens 22f with the XY alignment index projection optical system 22, and also shares a half mirror 21e with the anterior eye observation optical system 21.

[0042] The fixation target light source 23a emits visible light as fixation target light. This fixation target light is guided to the hole of the pinhole plate 23b, passes through the hole of the pinhole plate 23b and the dichroic mirror 22e, and is then emitted to the collimator lens 22f. The fixation target light is then converted into substantially parallel light by the collimator lens 22f and emitted toward the half mirror 21e, and is reflected by the half mirror 21e to travel along the optical axis O1 of the anterior eye observation optical system 21. As a result, the fixation target light passes through the half mirror 21g and the chamber window glass 21d, passes through the inside of the nozzle 21b, and reaches the subject's eye E. The subject can fix his or her gaze on the fixation target as a fixation target.

[0043] The applanation detection optical system 24 (see FIG. 3) corresponds to the light receiving optical system of the present invention, receives the XY index reflected light, and outputs an applanation signal (also called a corneal deformation signal) which is a light receiving signal indicating the amount of the XY index reflected light. The applanation detection optical system 24 has a lens 24a, a pinhole plate 24b, and a light receiving sensor 24c, and shares the half mirror 21g with the anterior eye observation optical system 21.

[0044] When the surface of the cornea Ec is flat, the lens 24a condenses the XY index reflected light onto the opening of the pinhole plate 24b, which is provided at the focal position of the lens 24a.

[0045] The light receiving sensor 24c is, for example, a photodiode that outputs an applanation signal according to the amount of light of the received XY index reflected light. The light receiving sensor 24c outputs the applanation signal to the control device 16.

[0046] The XY index reflected light passes through the inside of the nozzle 21b, passes through the chamber window glass 21d, and reaches the half mirror 21g. Then, a part of the XY index reflected light is reflected by the half mirror 21g, passes through the lens 24a, and is then incident on the pinhole plate 24b.

[0047] When the surface of the cornea Ec is in a flattened state (flat state) by the air blown from the nozzle 21b, the applanation detection optical system 24 allows the entire XY index reflected light traveling to the applanation detection optical system 24 to reach the light receiving sensor 24c through the pinhole plate 24b. When the cornea Ec is in a state other than the applanation state, the applanation detection optical system 24 allows the XY index reflected light to reach the light receiving sensor 24c while partially blocking it with the pinhole plate 24b. Therefore, the signal intensity of the detection signal of the XY index reflected light output from the applanation detection optical system 24 gradually increases as the surface of the cornea Ec changes from a convex state to an applanation state, and gradually decreases as the surface changes from the applanation state to a concave state.

[0048] The Z-alignment index projection optical system 25 (see FIG. 2) projects Z-alignment index light for Z alignment in the Z-axis direction from an oblique direction onto the cornea Ec. The Z-alignment index projection optical system 25 includes a Z-alignment light source 25a, a condenser lens 25b, an aperture stop 25c, a pinhole plate 25d, and a collimator lens 25e along the optical axis O2.

[0049] The Z-alignment light source 25a emits infrared light (for example, a wavelength of 860 nm). The aperture stop 25c is provided at a position conjugate with the corneal apex Ep with respect to the collimator lens 25e. The collimator lens 25e is disposed so as to focus on the hole of the pinhole plate 25d.

[0050] The infrared light emitted from the Z-alignment light source 25a is condensed by the condenser lens 25b, passes through the aperture stop 25c, and travels to the pinhole plate 25d. The infrared light that passes through the hole in the pinhole plate 25d is collimated by the collimator lens 25e, and then enters the subject's eye E as Z-alignment index light. The light is reflected by the cornea Ec to form a bright point image on the subject's eye E.

[0051] The Z alignment detection optical system 26 receives the reflected light of the Z alignment index light by the cornea Ec (hereinafter, abbreviated as Z index reflected light) and detects the positional relationship in the Z axis direction between the measurement head 14 and the cornea Ec. The Z alignment detection optical system 26 has an imaging lens 26a, a cylindrical lens 26b, and a light receiving sensor 26c along the optical axis O3.

[0052] The cylindrical lens 26b has power in the Y-axis direction. The light receiving sensor 26c is a sensor capable of detecting the receiving position of the Z index reflected light on its light receiving surface, and may be, for example, a line sensor or a PSD (Position Sensitive Detector).

[0053] The Z index reflected light is focused by the imaging lens 26a and then travels to the cylindrical lens 26b, where it is focused in the Y-axis direction to form a bright spot image on the light receiving sensor 26c.

[0054] The light receiving sensor 26c is in a positional relationship conjugate with the above-mentioned bright spot image formed on the subject's eye E by the Z alignment index projection optical system 25 with respect to the imaging lens 26a in the XZ plane. Also, the light receiving sensor 26c is in a positional relationship conjugate with the corneal apex Ep with respect to the imaging lens 26a and the cylindrical lens 26b in the YZ plane. That is, since the light receiving sensor 26c is in a conjugate relationship with the aperture stop 25c, even if the cornea Ec is displaced in the Y direction, the Z index reflected light on the surface of the cornea Ec efficiently enters the light receiving sensor 26c. Then, the light receiving sensor 26c outputs a detection signal of the Z index reflected light collected by the cylindrical lens 26b (hereinafter, referred to as a Z detection signal) to the control device 16. This Z detection signal indicates the relative position of the subject's eye E in the Z direction with respect to the measurement head 14, more specifically, the distance in the Z direction between the measurement head 14 and the subject's eye E (corneal apex Ep). This allows Z alignment detection.

[0055] The spray mechanism 34 (see FIG. 3) has, in addition to the nozzle 21b already described, a chamber 34a, a glass plate 34b, a pressure sensor 34c, a cylinder 34d, a connecting pipe 34e, a piston 34f, a solenoid 34g, a crank mechanism 34h, and an angle detection sensor 34i.

[0056] The nozzle 21b is attached to the chamber 34a via a transparent glass plate 34b. A chamber window glass 21d is provided in the chamber 34a at a position facing the nozzle 21b. A pressure sensor 34c is provided in the chamber 34a. The pressure sensor 34c outputs a pressure detection signal indicating the internal pressure of the chamber 34a (internal pressure) to the control device 16.

[0057] The cylinder 34d is connected to the chamber 34a via a communication pipe 34e. As a result, the inside of the cylinder 34d and the inside of the chamber 34a communicate with each other via the communication pipe 34e, and the inside of the cylinder 34d communicates with the nozzle 21b. A piston 34f is movably provided inside the cylinder 34d. The cylinder 34d and the piston 34f form an air compression chamber.

[0058] The solenoid 34g is a rotary solenoid that rotates when a current is applied, and corresponds to the actuator and rotary actuator of the present invention. The solenoid 34g is connected to the piston 34f via a crank mechanism 34h that converts the rotational motion into linear motion. The solenoid 34g rotates when a current is applied under the control of the control device 16, and the piston 34f moves linearly inside the cylinder 34d via the crank mechanism 34h, compressing the air in the cylinder 34d. As a result, air is blown from the nozzle 21b to the cornea Ec through the communication tube 34e and the chamber 34a.

[0059] In addition, in the blowing mechanism 34, the pressure sensor 34c detects the internal pressure of the chamber 34a, so that the pressure of the air blown from the nozzle 21b to the cornea Ec can be obtained.

[0060] The angle detection sensor 34i corresponds to the detection sensor of the present invention, and detects the rotation angle of the solenoid 34g, which corresponds to the displacement of the actuator of the present invention, and outputs the detection result to the control device 16. The rotation angle of the solenoid 34g detected by the angle detection sensor 34i indirectly indicates the internal pressure of the chamber 34a, and can be used for driving control of the solenoid 34g, which will be described in detail later. Note that if the detection result of the angle detection sensor 34i is not used for driving control of the solenoid 34g, the angle detection sensor 34i can be omitted.

[0061] Fig. 4 is a functional block diagram of the control device 16. As shown in Fig. 4, the control device 16 controls the overall operation of the non-contact tonometer 10. The control device 16 includes an arithmetic circuit configured with various processors and memories. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., simple programmable logic devices (SPLD), complex programmable logic devices (CPLD), and field programmable gate arrays (FPGA)). The various functions of the control device 16 may be realized by one processor, or may be realized by multiple processors of the same or different types.

[0062] The control device 16 is connected to the above-mentioned moving mechanism 13, the measurement head 14, the monitor 15, etc. This control device 16 controls the overall operation of the non-contact tonometer 10.

[0063] The control device 16 reads out and executes a control program (not shown) to function as an alignment control unit 40, a measurement control unit 42, and an intraocular pressure value calculation unit 44. Note that what is described as a "unit" of the control device 16 may also be a "circuit", a "device", or a "equipment". In other words, what is described as a "unit" may be composed of firmware, software, hardware, or a combination of these.

[0064] The alignment control unit 40 operates during intraocular pressure measurement of the subject's eye E, and controls auto-alignment of the measuring head 14 with respect to the subject's eye E in the X, Y and Z directions.

[0065] Specifically, the alignment control unit 40 controls the anterior eye observation optical system 21 and the XY alignment index projecting optical system 22 described above to perform XY alignment detection to detect the relative position of the subject's eye E in the XY direction with respect to the measurement head 14. The alignment control unit 40 also controls the Z alignment index projecting optical system 25 and the Z alignment detection optical system 26 to perform Z alignment detection to detect the relative position of the subject's eye E in the Z direction with respect to the measurement head 14. Note that the XY alignment detection and Z alignment detection of the non-contact tonometer 10 are well-known techniques, so a detailed description will be omitted here. Next, the alignment control unit 40 drives the moving mechanism 13 based on the XYZ alignment detection result to perform automatic alignment of the measurement head 14 with respect to the subject's eye E in the XYZ directions.

[0066] After completing the auto-alignment, the measurement control unit 42 operates the spray mechanism 34 to perform a spraying process in which air is sprayed onto the cornea Ec from the nozzle 21b of the spray mechanism 34. Specifically, the measurement control unit 42 applies a current to the solenoid 34g to rotate (drive) the solenoid 34g, thereby moving the piston 34f toward the back of the cylinder 34d via the crank mechanism 34h. Thus, the measurement control unit 42 corresponds to the current application control unit of the present invention. At this time, the measurement control unit 42 applies a current to the solenoid 34g under conditions that both reduce the sound generated by the spray mechanism 34 and ensure the measurement accuracy of the intraocular pressure measurement.

[0067] FIG. 5 is a diagram showing an example of a current waveform CW1 that is the waveform of the current that the measurement control unit 42 applies to the solenoid 34g during the spraying process.

[0068] The symbol CW2 in Fig. 5 is an example of a current waveform of a comparative example that only achieves silencing of the sound generated by the spray mechanism 34. The symbol PW1 in Fig. 5 is an example of an internal pressure waveform that shows the time change of the pressure (internal pressure) inside the chamber 34a detected by the pressure sensor 34c when the measurement control unit 42 applies a current of the current waveform CW1 to the solenoid 34g. The symbol PW2 in Fig. 5 is an internal pressure waveform that shows the time change of the pressure inside the chamber 34a detected by the pressure sensor 34c when the measurement control unit 42 applies a current of the current waveform CW2 to the solenoid 34g. Furthermore, the symbol W in Fig. 5 shows the pulse width of the current waveforms CW1 and CW2, i.e., the application period of the current to the solenoid 34g.

[0069] 5, in order to reduce the sound generated by the spray mechanism 34 during the spray process, it is necessary to reduce the current value of the current applied to the solenoid 34g by the measurement control unit 42. For this reason, the measurement control unit 42 applies a first current value DAC1 to the solenoid 34g. The first current value DAC1 is a current value aimed at reducing the sound generated by the spray mechanism 34, and is, for example, the minimum current value capable of driving the piston 34f. This first current value DAC1 is appropriately determined by experiments, simulations, etc.

[0070] At this time, as shown in the current waveform CW2 of the comparative example, if the current value of the current applied to the solenoid 34g is kept constant at the first current value DAC1 over the entire period of the pulse width W, the torque generated by the solenoid 34g becomes constant. On the other hand, as the rotation of the solenoid 34g progresses, the force required to compress the air in the chamber 34a increases. Therefore, if the current value of the current applied to the solenoid 34g is kept constant at the first current value DAC1, the force applied to the piston 34f via the crank mechanism 34h weakens as the rotation of the solenoid 34g progresses. As a result, as shown in the internal pressure waveform PW2 of the comparative example, the pressure of the air in the chamber 34a does not increase, and the pressure of the air blown from the nozzle 21b to the cornea Ec is insufficient. In this case, the intraocular pressure value of the subject's eye E cannot be measured accurately.

[0071] Therefore, as shown by the current waveform CW1, the measurement control unit 42 executes a first application process in which the current value of the current applied to the solenoid 34g is kept constant at a first current value DAC1 at the start of the spray process. Then, at a switching timing TA when a predetermined switching condition is satisfied during the execution of the first application process, the measurement control unit 42 executes a second application process in which the current value of the current applied to the solenoid 34g is increased to a second current value DAC2 higher than the first current value DAC1, and the current of the second current value DAC2 is applied to the solenoid 34g.

[0072] The switching condition for switching from the first application process to the second application process (hereinafter, simply referred to as the switching condition) is determined so that the force transmitted from the solenoid 34g to the piston 34f does not decrease even if the rotation of the solenoid 34g progresses. Specifically, in this embodiment, the first application process is switched to the second application process when the pressure detected by the pressure sensor 34c during the execution of the first application process reaches a predetermined pressure threshold. For this reason, the measurement control unit 42 continues the first application process from the start of the first application process at the start of the spraying process until the pressure detected by the pressure sensor 34c reaches the pressure threshold.

[0073] When the pressure detected by the pressure sensor 34c during the first application process reaches the pressure threshold (switching timing TA), the measurement control unit 42 increases the current value applied to the solenoid 34g from the first current value DAC1 to the second current value DAC2, thereby switching from the first application process to the second application process. This keeps the slope of the internal pressure waveform PW1 substantially constant, making it possible to sufficiently increase the pressure of the air in the chamber 34a. The pressure threshold and the second current value DAC2 are set to values ​​that can keep the slope of the internal pressure waveform PW1 substantially constant through experiments, simulations, etc.

[0074] Note that there is a correlation between the pressure detected by the pressure sensor 34c during the spraying process and the rotation angle of the solenoid 34g detected by the angle detection sensor 34i. Therefore, instead of the above-mentioned switching condition, the process may be switched to the second application process when the rotation angle detected by the angle detection sensor 34i during the execution of the first application process reaches a predetermined angle threshold (the displacement amount threshold of the present invention). In this case, the measurement control unit 42 continues the first application process until the rotation angle detected by the angle detection sensor 34i reaches the angle threshold, and switches to the second application process at the timing when the rotation angle detected by the angle detection sensor 34i reaches the angle threshold (switching timing TA).

[0075] When a predetermined specified time (time corresponding to the pulse width W) has elapsed since the start of the first application process, the measurement control unit 42 stops the second application process by stopping the application of current to the solenoid 34g. Note that the measurement control unit 42 may start timing after starting the second application process, and stop the second application process when the predetermined specified time has elapsed. That is, the timing at which timing of the specified time starts is not particularly limited.

[0076] Returning to FIG. 4, while the measurement control unit 42 is executing the spraying process, it continuously executes the projection process of the XY alignment index light onto the cornea Ec by the XY alignment index projecting optical system 22, and the signal output process including the reception of the XY index reflected light by the applanation detection optical system 24 and the output of the applanation signal.

[0077] The intraocular pressure value calculation unit 44 calculates the intraocular pressure value of the subject's eye E based on the applanation signal continuously output from the applanation detection optical system 24 and the detection result of the pressure sensor 34c. For example, the intraocular pressure value calculation unit 44 calculates the peak centroid position or maximum value of the applanation waveform SW (see reference numeral 7B in FIG. 7) based on the applanation signal output from the applanation detection optical system 24. Then, the intraocular pressure value calculation unit 44 calculates the intraocular pressure value of the subject's eye E by a known method based on the signal intensity (light amount) of the applanation signal corresponding to the peak centroid position or maximum value and the detection result (air pressure) of the pressure sensor 34c. Note that the method of calculating the intraocular pressure value of the subject's eye E is not limited to the above-mentioned method, and various known methods can be adopted.

[0078] [Operation of the first embodiment] FIG. 6 is a flow chart showing the flow of an intraocular pressure measurement process of the subject's eye E, which is an operation method of the non-contact tonometer 10 of the first embodiment having the above-mentioned configuration.

[0079] As shown in Figure 6, after the subject's face is set on the face support part 12, when the examiner inputs an operation to start intraocular pressure measurement into an operation part not shown, the control device 16 functions as an alignment control part 40, a measurement control part 42, and an intraocular pressure value calculation part 44.

[0080] First, the alignment control unit 40 controls the anterior eye observation optical system 21 and the XY alignment index projecting optical system 22 to perform XY alignment detection, and also controls the Z alignment index projecting optical system 25 and the Z alignment detection optical system 26 to perform Z alignment detection. Next, the alignment control unit 40 drives the moving mechanism 13 based on the XYZ alignment detection result to perform auto-alignment of the measuring head 14 in the XYZ directions with respect to the subject's eye E (step S1).

[0081] After completing the auto-alignment, the measurement control unit 42 operates the spray mechanism 34 to execute the spray process. At this time, the measurement control unit 42 starts a first application process in which a current of a first current value DAC1 is applied to the solenoid 34g at the initial start of the spray process (step S2). The measurement control unit 42 also monitors the pressure detected by the pressure sensor 34c, and continues the first application process until the pressure reaches the pressure threshold value, that is, until the switching condition is satisfied (NO in step S3). At this stage, a low current of the first current value DAC1 is applied to the solenoid 34g, so that the sound generated by the spray mechanism 34 can be reduced.

[0082] Then, when the pressure detected by the pressure sensor 34c during the first application process reaches the pressure threshold, i.e., when the switching condition is satisfied (YES in step S3), the measurement control unit 42 increases the current value applied to the solenoid 34g to the second current value DAC2, thereby switching from the first application process to the second application process (steps S4, S5). As a result, as shown in Fig. 5, the slope of the internal pressure waveform PW1 before and after the switching timing TA is maintained substantially constant, and the pressure of the air in the chamber 34a can be sufficiently increased.

[0083] In addition, when the rotation angle of the solenoid 34g detected by the angle detection sensor 34i during execution of the first application process reaches an angle threshold value, the measurement control unit 42 may determine that the switching condition is satisfied and execute switching from the first application process to the second application process.

[0084] The measurement control unit 42 continues the second application process until a specified time has elapsed since the start of the first application process, and maintains the current value applied to the solenoid 34g at the second current value DAC2 (steps S6 and S7: NO). Then, when the specified time has elapsed (step S7: YES), the measurement control unit 42 stops the application of current to the solenoid 34g, thereby stopping the second application process (step S8).

[0085] In addition, during the spraying process, the measurement control unit 42 continuously executes a process of projecting the XY alignment index light onto the cornea Ec by the XY alignment index projecting optical system 22, and a signal output process including receiving the XY index reflected light by the applanation detection optical system 24 and outputting an applanation signal.

[0086] When the spraying process is completed, the intraocular pressure value calculation unit 44 calculates the centroid position or maximum value of the peak of the applanation waveform SW based on the applanation signal output from the applanation detection optical system 24. Then, the intraocular pressure value calculation unit 44 calculates the intraocular pressure value of the subject's eye E based on the signal intensity (light amount) of the applanation signal corresponding to the centroid position or maximum value of the peak and the detection result (air pressure) of the pressure sensor 34c (step S9).

[0087] Fig. 7 is a graph showing an applanation waveform SW based on an applanation signal continuously output from the applanation detection optical system 24. Reference numeral 7A in Fig. 7 is an example of an applanation waveform SW obtained when a current having a waveform CW2 of the comparative example shown in Fig. 5 is applied to the solenoid 34g. Reference numeral 7B in Fig. 7 is an example of an applanation waveform SW obtained when a current having a waveform CW1 of the present embodiment shown in Fig. 5 is applied to the solenoid 34g.

[0088] If the current value applied to the solenoid 34g is fixed to the first current value DAC1 for the sole purpose of reducing the noise generated by the blowing mechanism 34, the air pressure in the chamber 34a does not rise sufficiently as shown in the internal pressure waveform PW2 shown in Fig. 5. As a result, as shown by reference numeral 7A in Fig. 7, the applanation waveform SW does not become a normal waveform (see reference numeral 7B in Fig. 7), making it difficult to detect a peak from the applanation waveform SW. This reduces the measurement accuracy of the intraocular pressure value of the subject's eye E.

[0089] In contrast, in this embodiment, as shown by reference symbol 7B in Fig. 7, the current value of the current applied to the solenoid 34g is increased from the first current value DAC1 to the second current value DAC2 during the spraying process, thereby making it possible to sufficiently increase the air pressure in the chamber 34a. As a result, as shown by reference symbol 7B in Fig. 7, the applanation waveform SW becomes a normal waveform, so that the intraocular pressure value calculation unit 44 can accurately detect the peak of the applanation waveform SW. This prevents a decrease in the measurement accuracy of the intraocular pressure value of the subject's eye E.

[0090] As described above, the non-contact tonometer 10 of the first embodiment applies a current of the first current value DAC1 to the solenoid 34g at the start of the spraying process to reduce the sound generated by the spraying mechanism 34, and increases the current value applied to the solenoid 34g to the second current value DAC2 in the middle of the spraying process, thereby preventing a decrease in the measurement accuracy of the intraocular pressure of the subject's eye E. As a result, the non-contact tonometer 10 of the first embodiment can achieve both noise reduction and measurement accuracy during intraocular pressure measurement.

[0091] [Second embodiment] In the non-contact tonometer 10 of the first embodiment, the second application process is stopped when a predetermined specified time (time corresponding to the pulse width W) has elapsed since the start of the first application process. In contrast, in the non-contact tonometer 10 of the second embodiment, the second application process is stopped at a stop timing different from that of the first embodiment.

[0092] The non-contact tonometer 10 of the second embodiment has basically the same configuration as the non-contact tonometer 10 of the first embodiment described above, so parts that are the same in function or configuration as those of the first embodiment described above are given the same reference numerals and their description is omitted.

[0093] Fig. 8 is an explanatory diagram for explaining the timing of stopping the second application process by the non-contact tonometer 10 of the second embodiment. As shown in Fig. 8, the measurement control unit 42 of the non-contact tonometer 10 of the second embodiment detects the peak P of the applanation waveform SW, for example, by continuously calculating the slope of the applanation waveform SW based on the applanation signal continuously output from the applanation detection optical system 24 during the execution of the second application process. Then, when the measurement control unit 42 of the second embodiment detects the peak P of the applanation waveform SW, it stops the application of current to the solenoid 34g to stop the second application process.

[0094] 9 is a flow chart showing the flow of the intraocular pressure measurement process of the subject's eye E by the non-contact tonometer 10 of the second embodiment. Note that the processes from step S1 to step S6 are the same as the processes from step S1 to step S6 of the first embodiment shown in FIG. 6, so a detailed description thereof will be omitted here.

[0095] The measurement control unit 42 continues the second application process until it detects the peak P of the applanation waveform SW based on the applanation signal continuously output from the applanation detection optical system 24 during the execution of the second application process, and maintains the current value of the current applied to the solenoid 34g at the second current value DAC2 (step S6, NO in step S7A). Then, when the measurement control unit 42 detects the peak P of the applanation waveform SW (YES in step S7A), it stops the current application to the solenoid 34g to stop the second application process (step S8). The process thereafter is the same as that of the first embodiment shown in FIG. 6, and therefore a detailed description thereof will be omitted here.

[0096] As described above, in the non-contact tonometer 10 of the second embodiment, as in the first embodiment, a current of the first current value DAC1 is applied to the solenoid 34g at the start of the spraying process, and the current value of the current applied to the solenoid 34g is increased to the second current value DAC2 during the spraying process, so that the same effect as in the first embodiment can be obtained. In addition, by stopping the second application process after detecting the peak P of the applanation waveform SW, a so-called soft puff that reduces the amount of air sprayed onto the subject's eye E can be realized, so that the discomfort of the subject can be reduced.

[0097] [Third embodiment] 10 is an explanatory diagram for explaining the second application process executed by the non-contact tonometer 10 of the third embodiment. In the non-contact tonometer 10 of each of the above embodiments, the second current value DAC2 during the second application process is set to one value. Therefore, when the condition for switching to the second application process is satisfied during the execution of the first application process, the measurement control unit 42 of each of the above embodiments increases the current value of the current applied to the solenoid 34g to this one second current value DAC2 and maintains it at the second current value DAC2. In contrast, the non-contact tonometer 10 of the third embodiment executes a second application process different from that of each of the above embodiments.

[0098] The non-contact tonometer 10 of the third embodiment has basically the same configuration as the non-contact tonometer 10 of each of the above embodiments, except for the method of the second application process. Therefore, parts that are the same in function or configuration as the above embodiments are given the same symbols and their descriptions are omitted.

[0099] 10, a plurality of second current values ​​DAC2 are set in the non-contact tonometer 10 of the third embodiment. When a condition for switching to the second application process is satisfied during execution of the first application process, the measurement control unit 42 of the non-contact tonometer 10 of the third embodiment gradually increases the second current value DAC2 of the current applied to the solenoid 34g in a plurality of stages.

[0100] Specifically, the above-mentioned pressure threshold is set in advance for each second current value DAC2. In this case, the pressure threshold is set to be higher in stages as the second current value DAC2 increases in stages. Then, the measurement control unit 42 applies a current of the second current value DAC2 corresponding to the pressure threshold to the solenoid 34g each time the pressure detected by the pressure sensor 34c during the execution of the second application process reaches the pressure threshold. This allows the measurement control unit 42 to increase the second current value DAC2 in stages in response to an increase in the pressure detected by the pressure sensor 34c during the execution of the second application process.

[0101] The angle threshold may be set in advance for each second current value DAC2. In this case, the angle threshold is set to be higher in stages as the second current value DAC2 increases in stages. Then, the measurement control unit 42 applies a current of the second current value DAC2 corresponding to the angle threshold to the solenoid 34g every time the rotation angle of the solenoid 34g detected by the angle detection sensor 34i during the execution of the second application process reaches the angle threshold. This allows the measurement control unit 42 to increase the second current value DAC2 in stages in response to an increase in the rotation angle of the solenoid 34g detected by the angle detection sensor 34i during the execution of the second application process.

[0102] In addition, during execution of the second application process, the measurement control unit 42 may gradually increase the second current value DAC2 of the current applied to the solenoid 34g each time the pressure detected by the pressure sensor 34c or the rotation angle detected by the angle detection sensor 34i increases by a certain amount.

[0103] As described above, in the non-contact tonometer 10 of the third embodiment, a current of the first current value DAC1 is applied to the solenoid 34g at the start of the spraying process, and the second current value DAC2 of the current applied to the solenoid 34g is gradually increased in the middle of the spraying process, thereby achieving the same effect as in each of the above embodiments.

[0104] [others] In each of the above embodiments, the piston 34f is driven by the solenoid 34g, but the piston 34f may be driven using a rotary actuator other than the solenoid 34g, and further, an actuator other than a rotary actuator may be used as long as it is capable of driving the piston 34f.

[0105] In each of the above embodiments, the non-contact tonometer 10 has been used as an example, but the present invention can also be applied to a multifunction device capable of measuring the intraocular pressure value of the subject's eye E and eye characteristics other than the intraocular pressure value of the subject's eye E. [Explanation of symbols]

[0106] 10. Non-contact tonometer 11...Bass 12…Face support part 12a…Chin rest 12b…Forehead rest 12c…post 13...Movement mechanism 14…Measuring head 15…Monitor 16...Control device 21...Anterior segment observation optical system 21a...Anterior segment illumination light source 21b…Nozzle 21c…Anterior window glass 21d…Chamber window glass 21e…Half mirror 21f…Objective lens 21g…Half mirror 21i…Image sensor 22...XY alignment target projection optical system 22a…Light source for XY alignment 22b...Condenser lens 22c…Aperture diaphragm 22d…Pinhole plate 22e…Dichroic mirror 22f...Collimator lens 23…Fixation target projection optical system 23a...Fixation target light source 23b…Pinhole plate 24...Applanation detection optical system 24a…Lens 24b…Pinhole plate 24c...Light receiving sensor 25...Z alignment index projection optical system 25a…Z alignment light source 25b…Condenser lens 25c…Aperture 25d…Pinhole plate 25e…Collimator lens 26…Z alignment detection optical system 26a…Imaging lens 26b…Cylindrical lens 26c...Light receiving sensor 34...Spray mechanism 34a…Chamber room 34b…Glass plate 34c...Pressure sensor 34d…Cylinder 34e…Communication pipe 34f…Piston 34g…Solenoid 34h…Crank mechanism 34i...Angle detection sensor 40...Alignment control unit 42...Measurement control section 44...Intraocular pressure value calculation unit CW1…Current waveform CW2…Current waveform DAC1…First current value DAC2: Second current value E…Examined eye Ec…cornea Ep…corneal apex O1…Optical axis O2…optical axis O3…Optical axis P…Peak PW1…Internal pressure waveform PW2…Internal pressure waveform SW…Applanation waveform TA: Switching timing W: Pulse width

Claims

1. A cylinder; A piston movably provided inside the cylinder; an actuator that moves the piston inside the cylinder by application of an electric current, thereby compressing air inside the cylinder with the piston; a nozzle communicating with the inside of the cylinder and blowing the air compressed by the piston onto the subject's eye; a current application control unit that applies the current to the actuator; Equipped with A non-contact tonometer in which the current application control unit executes a first application process to apply the current to the actuator at a first current value, and when a predetermined switching condition is satisfied during execution of the first application process, switches from the first application process to a second application process to apply the current to the actuator at a second current value higher than the first current value.

2. the nozzle is in communication with the interior of the cylinder via a chamber in communication with the interior of the cylinder, a pressure sensor for detecting a pressure inside the chamber; The non-contact tonometer according to claim 1 , wherein the current application control unit determines whether the switching condition is satisfied based on whether the pressure detected by the pressure sensor reaches a predetermined pressure threshold.

3. a detection sensor for detecting a displacement amount of the actuator; The non-contact tonometer according to claim 1 , wherein the current application control unit determines whether the switching condition is satisfied based on whether the displacement amount detected by the detection sensor reaches a predetermined displacement amount threshold.

4. The non-contact tonometer according to claim 1 , wherein the current application control unit increases the second current value stepwise during execution of the second application process.

5. the nozzle is in communication with the interior of the cylinder via a chamber in communication with the interior of the cylinder, a pressure sensor for detecting a pressure inside the chamber; The non-contact tonometer according to claim 4 , wherein the current application control unit increases the second current value stepwise in response to an increase in the pressure detected by the pressure sensor during execution of the second application process.

6. a detection sensor for detecting a displacement amount of the actuator; The non-contact tonometer according to claim 4 , wherein the current application control unit increases the second current value stepwise in response to an increase in the amount of displacement detected by the detection sensor during execution of the second application process.

7. 4. The non-contact tonometer according to claim 1, wherein the current application control unit stops the second application process when a predetermined specified time has elapsed since the start of the first application process.

8. a projection optical system that projects a light beam onto the subject's eye while the air is being blown from the nozzle to the subject's eye; a light receiving optical system that receives reflected light of the light beam reflected by the subject's eye while the air is being blown from the nozzle to the subject's eye and outputs an applanation signal; Equipped with 4. The non-contact tonometer according to claim 1, wherein the current application control unit stops the second application process when it detects a peak of the applanation signal output from the light receiving optical system during execution of the second application process.

9. 4. The non-contact tonometer according to claim 1, wherein the actuator is a rotary actuator that moves the piston inside the cylinder via a crank mechanism.

10. A cylinder; A piston movably provided inside the cylinder; an actuator that moves the piston inside the cylinder by application of an electric current, thereby compressing air inside the cylinder with the piston; a nozzle communicating with the inside of the cylinder and blowing the air compressed by the piston onto the subject's eye; A method for operating a non-contact tonometer comprising: A method for operating a non-contact tonometer, which, when applying the current to the actuator, executes a first application process in which the current is applied to the actuator at a first current value, and, if a predetermined switching condition is satisfied during execution of the first application process, switches from the first application process to a second application process in which the current is applied to the actuator at a second current value higher than the first current value.

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