Non-contact tonometer

Abstract

To shorten the time required for tonometry without increase in the number of components.SOLUTION: An ophthalmologic apparatus 1 includes a fluid discharge unit 20, a capacitor 100, and a control unit 80. When a voltage curve that is drawn when the capacitor 100 charges is a charge voltage curve, the capacitor 100 has a charge voltage characteristic in which a voltage value VX when a curve obtained by taking the second derivative of the charge voltage curve has a minimum value is larger than a drive voltage VB.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a non-contact tonometry device for measuring the intraocular pressure of a subject's eye. [Background technology]

[0002] A non-contact tonometry device is known that measures the intraocular pressure of a test eye by deforming the cornea of ​​the test eye and detecting the deformed cornea. To deform the cornea of ​​the test eye, a fluid such as compressed air is ejected from a fluid ejection unit onto the test eye, and the pressure of the fluid deforms the cornea of ​​the test eye. Conventionally, power is supplied to such a fluid ejection unit using a capacitor.

[0003] Specifically, the magnitude and timing of the power supplied to the fluid discharge unit are adjusted by controlling the charging and discharging of the capacitor. Typically, in one intraocular pressure measurement, fluid is discharged from the fluid discharge unit multiple times into the subject's eye. Therefore, when the first discharge of fluid from the fluid discharge unit is completed, the capacitor begins to charge and is charged until it reaches or exceeds a predetermined charging voltage (called the driving voltage). Then, when the charging voltage of the capacitor reaches or exceeds the driving voltage, a second discharge is performed, and fluid is again discharged into the subject's eye. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 9-285449 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if it takes time for the capacitor to start charging after the previous fluid discharge has finished and reach the drive voltage, the total time required for intraocular pressure measurement increases. Therefore, by using a high-quality capacitor with a high maximum charging voltage and capacitance, it is possible to shorten the charging time. However, using such a high-quality capacitor has the drawback of increasing product costs.

[0006] A typical object of the present disclosure is to provide a non-contact ocular pressure measuring device that can reduce the time required for measuring ocular pressure while suppressing an increase in costs. [Means for solving the problem]

[0007] A non-contact ocular pressure measuring device provided by a typical embodiment of the present disclosure detects deformation of the cornea of ​​a test eye and measures the intraocular pressure of the test eye. The non-contact ocular pressure measuring device includes a fluid discharge unit that discharges fluid onto the test eye to deform the cornea, a capacitor that supplies driving power to the fluid discharge unit by charging and discharging, and a control unit that controls the charging and discharging of the capacitor to supply power to the fluid discharge unit multiple times and discharge fluid into the test eye multiple times. A driving voltage is a charging voltage of the capacitor that serves as a reference charging voltage for the fluid discharge unit to discharge fluid once. The control unit is configured to discharge the capacitor while charging it to a voltage equal to or greater than the driving voltage, supply power to the fluid discharge unit to perform a first discharge into the test eye, and for second and subsequent discharges of fluid, charge the capacitor and discharge it when the voltage reaches or exceeds the driving voltage, thereby supplying power to the fluid discharge unit. If the voltage curve that a capacitor draws when charging is called a charging voltage curve, the capacitor has charging voltage characteristics in which the voltage value at which the curve obtained by second-order differentiation of the charging voltage curve has a minimum value is greater than the driving voltage.

[0008] The non-contact intraocular pressure measuring device according to the present disclosure can shorten the time required for intraocular pressure measurement without increasing the product cost. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a left side view showing the external configuration of the ophthalmologic apparatus. [Figure 2] FIG. 2 is a diagram illustrating an internal configuration of an ophthalmologic apparatus. [Figure 3] 10 is a graph showing a charging voltage curve of a capacitor during intraocular pressure measurement. [Figure 4] FIG. 10 is a diagram showing a comparison between a charging voltage curve of a capacitor during intraocular pressure measurement and a curve obtained by second-order differentiation of the charging voltage curve. [Figure 5] FIG. 10 is a diagram showing a comparison between a charging voltage curve of a capacitor during intraocular pressure measurement and a charging voltage curve of a capacitor according to a comparative example. [Figure 6] 10 is a flowchart illustrating an intraocular pressure measurement process executed by an ophthalmologic apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Summary> A non-contact ocular pressure measuring device exemplified in the present disclosure detects deformation of the cornea of ​​a subject's eye and measures the intraocular pressure of the subject's eye. The non-contact ocular pressure measuring device includes a fluid discharge unit that discharges fluid onto the subject's eye to deform the cornea, a capacitor that supplies driving power to the fluid discharge unit by charging and discharging, and a control unit that controls the charging and discharging of the capacitor to supply power to the fluid discharge unit multiple times and discharge fluid into the subject's eye multiple times. A driving voltage is a charging voltage of the capacitor that serves as a reference charging voltage for the fluid discharge unit to discharge fluid once. The control unit is configured to discharge the capacitor while charging it to a voltage equal to or greater than the driving voltage, supply power to the fluid discharge unit to perform a first discharge into the subject's eye, and for second and subsequent discharges of fluid, charge the capacitor and discharge it when the voltage reaches or exceeds the driving voltage, thereby supplying power to the fluid discharge unit. If the voltage curve that a capacitor draws when charging is called a charging voltage curve, the capacitor has a charging voltage characteristic in which the voltage value at which the curve obtained by second-order differentiation of the charging voltage curve has a minimum value is greater than the driving voltage.

[0011] The capacitor has a charging voltage characteristic in which the voltage value obtained by second-order differentiation of the charging voltage curve is greater than the driving voltage. In other words, the capacitor is set to have the above charging voltage characteristic by appropriately adjusting the capacitor to a predetermined maximum charging voltage and capacitance. Therefore, the time from the end of the first discharge and the start of charging the capacitor until the driving voltage is reached can be shortened. As a result, the total time required for the intraocular pressure measurement process can be reduced without using a high-quality capacitor.

[0012] The maximum charging voltage of the capacitor may be set to be 1.5 times or more the driving voltage.

[0013] In this case, the maximum charging voltage of the capacitor is set to 1.5 times or more the drive voltage. This allows the slope of the charging voltage curve to increase until the drive voltage VB is reached during charging, thereby shortening the time it takes to reach the drive voltage VB.

[0014] The control unit may further include a determination unit that determines whether the cornea of ​​the test eye is not properly applanated and the drive voltage needs to be increased when power is supplied to the fluid discharge unit. When the determination unit determines that the drive voltage needs to be increased after power is supplied from the capacitor to the fluid discharge unit, the control unit may supply a larger amount of power to the fluid discharge unit in the next fluid discharge by discharging the capacitor at a timing when the capacitor is charged to a high drive voltage or higher that is higher than the drive voltage.

[0015] In this case, the control unit includes a determination unit that determines whether the drive voltage needs to be increased based on the measurement results when power is supplied to the fluid ejection unit. If the determination unit determines that the drive voltage needs to be increased, the control unit charges the capacitor to a high drive voltage higher than the drive voltage during the next fluid ejection, thereby supplying higher power to the fluid ejection unit. Therefore, for example, if the subject's intraocular pressure is high and the cornea cannot be properly applanated with normal fluid pressure, the drive voltage can be increased to eject high-pressure fluid into the subject's eye the next time. Note that the high drive voltage may be set to a voltage value equal to or lower than the minimum value of the curve obtained by second-order differentiation of the charging voltage curve. In this case, even when power is supplied to the fluid ejection unit based on the high drive voltage, the time it takes for the capacitor's charging voltage to reach the high drive voltage can be shortened.

[0016] <Embodiment> Hereinafter, one typical embodiment (first embodiment) according to the present disclosure will be described with reference to the drawings. An ophthalmic apparatus 1 examines a subject's eye (examined eye) E with an examination axis IO aligned with the subject's eye (examined eye) E. The ophthalmic apparatus 1 illustrated in this embodiment is equipped with an examination protrusion 9 that protrudes toward the examinee's eye along the examination axis IO, and measures the intraocular pressure of the examinee's eye E from the deformed shape of the cornea by spraying fluid from the examination protrusion 9 onto the cornea of ​​the examinee's eye E. In other words, the ophthalmic apparatus 1 illustrated in this embodiment is a non-contact ocular pressure measuring device. In this disclosure, "examination" includes both measurement and photography of the examinee's eye E.

[0017] The schematic configuration of an ophthalmic apparatus 1 will be described with reference to FIG. 1. In the following description, the left-right direction of the paper in FIG. 1 is the Z direction (front-back direction), the up-down direction of the paper is the Y direction (up-down direction), and the depth direction of the paper is the X direction (left-right direction). The examination axis IO is parallel to the Z direction and perpendicular to the XY plane. In detail, the left side of the paper (subject side) in FIG. 1 is the front side of the ophthalmic apparatus 1, and the right side of the paper is the rear side of the ophthalmic apparatus 1. The upper side of the paper in FIG. 1 is the upper side of the ophthalmic apparatus 1, and the lower side of the paper is the lower side of the ophthalmic apparatus 1. The front side of the paper in FIG. 1 is the left side of the ophthalmic apparatus 1, and the depth side of the paper is the right side of the ophthalmic apparatus 1. The Z direction is parallel to the examination axis IO.

[0018] As shown in FIG. 1, the ophthalmologic apparatus 1 of this embodiment includes a base 2, a housing 3, a drive unit 4, and a face support unit 5. The base 2 is placed at an installation location and supports the entire ophthalmologic apparatus 1. The housing 3 includes various components for performing an examination of the subject's eye E (details will be described later). The housing 3 is supported on the base 2 via the drive unit 4. The face support unit 5 supports and positions the subject's face. In this embodiment, a chin rest and a forehead rest are used as the face support unit 5. The subject places their chin on the chin rest and their forehead on the forehead rest, thereby positioning the face. The drive unit 4 moves the position of the housing 3 relative to the subject's face, which has been positioned by the face support unit 5.

[0019] As an example, the drive unit 4 of this embodiment moves the housing 3 in the front-back, up-down, and left-right directions (three-dimensional directions) relative to the base 2 using an actuator such as a motor (not shown). This moves the relative position of the housing 3 with respect to the face of the subject (or the eye to be examined). However, the configuration of the drive unit 4 can also be changed. For example, the drive unit 4 may move the relative position of the housing 3 with respect to the face of the subject by moving the face support unit 5. Alternatively, the drive unit 4 may move both the housing 3 and the face support unit 5. For example, the drive unit 4 may move the housing 3 in the front-back and left-right directions and also move the face support unit 5 in the up-down direction to move the relative position of the housing 3 with respect to the face of the subject.

[0020] The housing 3 includes an examination protrusion (nozzle) 9, a face capturing unit 12, a display unit 7, and an operation unit 8. The housing 3 includes a surface 3a facing the eye to be examined, which is the side on which the subject's face is positioned (in this embodiment, the front side facing the eye to be examined). The examination protrusion 9 protrudes from the surface 3a facing the eye to be examined along an examination axis IO toward the eye to be examined. The examination axis IO is aligned with the eye to be examined E when the examination is performed. As an example, the examination protrusion 9 in this embodiment is a nozzle that sprays a fluid (e.g., compressed air) onto the cornea of ​​the eye to be examined. However, the specific configuration of the examination protrusion can be appropriately selected depending on the type of examination performed by the ophthalmologic apparatus. For example, an attachment that is detachably attached to the housing 3 to change the imaging angle of view, a protrusion that emits light or ultrasound for examination from its tip toward the eye to be examined E, or the like may be used as the examination protrusion.

[0021] The face photographing unit 12 photographs the face of the subject. The display unit 7 displays various images. In this embodiment, the display unit 7 is disposed on the rear side of the housing 3 facing the examiner. Various operation instructions are input to the operation unit 8 by the user. As an example, in this embodiment, a touch panel installed on the display surface of the display unit 7 is used as the operation unit 8. However, at least one of a joystick, a mouse, a keyboard, a drag ball, a button, a remote controller, etc. may also be used as the operation unit 8.

[0022] The internal configuration of the ophthalmic apparatus 1 will be described with reference to Fig. 2. The ophthalmic apparatus 1 includes a measurement optical system 10, a fluid discharge unit 20, a capacitor 100, and a control unit 80 (control unit) 80. The measurement optical system 10 and the fluid discharge unit 20 are an example of an examination unit that performs an examination of the subject's eye E. As described above, the examination unit of this embodiment measures the intraocular pressure of the subject's eye E in a non-contact manner.

[0023] The fluid discharge unit 20 discharges fluid onto the cornea of ​​the subject's eye E. The fluid discharge unit 20 includes, for example, a cylinder 201, a piston 202, a solenoid actuator (hereinafter also referred to as a solenoid) 203, and an examination protrusion 9. The cylinder 201 and the piston 202 are used as an air compression mechanism that compresses air to be discharged into the subject's eye E. The cylinder 201 is, for example, cylindrical. The piston 202 slides along the axial direction of the cylinder 201. The piston 202 compresses air in an air compression chamber 234 inside the cylinder 201. The solenoid 203 includes a movable body 204 and a coil 205. The movable body 204 is made of a magnetic material such as a permanent magnet. When a voltage is applied to the coil 205 from the capacitor 100 and a current flows, a magnetic field is generated inside the coil 205. The movable body 204 is moved in the direction A in FIG. 2 by an electromagnetic force received from the magnetic field. The movable body 204 is fixed to the piston 202 with screws, bolts, nuts, etc. (not shown). Therefore, the piston 202 moves together with the movable body 204. The movement of the movable body 204 moves the piston 202 in the compression direction (or forward direction, direction A in FIG. 1). The inspection protrusion 9 discharges the compressed air to the outside of the device.

[0024] The fluid compressed in the air compression chamber 234 in the cylinder 201 by the movement of the piston 202 is discharged from the testing protrusion 9 toward the cornea of ​​the subject's eye E through a tube (which may be a pipe) 220 connected to the tip of the cylinder 201 and an airtight chamber 221 that stores the compressed air. In this embodiment, the power required to drive the solenoid 203 and discharge air once (hereinafter referred to as "required power") is set in advance. This required power is determined based on the structure and specifications of the fluid discharge unit 20. The charging voltage of the capacitor 100 (hereinafter referred to as "driving voltage VB"), which serves as a reference for supplying the required power to the solenoid 203, is also set in advance. That is, the ophthalmic apparatus 1 determines that the required power can be supplied to the solenoid 203 when the charging voltage of the capacitor 100 reaches or exceeds the driving voltage VB. In this embodiment, the driving voltage VB is set to, for example, 185 V. Furthermore, as will be described later, the ophthalmologic apparatus 1 of this embodiment measures the intraocular pressure of the subject's eye E multiple times (for example, four times) and calculates the average value as the intraocular pressure. Therefore, in one intraocular pressure measurement, power is supplied (voltage is applied) from the capacitor 100 to the fluid discharge unit 20 (solenoid 203) multiple times. When air is discharged to the outside, the piston 202 and the movable body 204 are moved in the opposite direction (direction B in FIG. 2) and returned to their initial positions.

[0025] The fluid discharge unit 20 includes a glass plate 208 and a glass plate 209. The glass plate 208 is transparent, holds the inspection protrusion 9, and transmits observation light and index light. The glass plate 209 forms the rear wall of the airtight chamber 221, and transmits observation light and index light.

[0026] The control unit 80 includes a CPU (processor) 81, a ROM 82, and a RAM 83. The CPU 81 controls various aspects of the ophthalmologic apparatus 1. The ROM 82 stores various programs, initial values, and the like. The RAM 83 temporarily stores various pieces of information. The ROM 82 and the RAM 83 are memories. The control unit 80 is connected to the display unit 7, the operation unit 8, and a storage unit 84. The storage unit (e.g., a non-volatile memory) 84 is a non-transitory storage medium that can retain its contents even when the power supply is cut off. For example, a hard disk drive, a flash ROM, a removable USB memory, or the like may be used as the storage unit 84. In this embodiment, control programs and the like for executing various processes described below are stored in the storage unit 84. Furthermore, the control unit 80 is electrically connected to the drive unit 4, the measurement optical system 10, the face photographing unit 12, and the like.

[0027] The control unit 80 is electrically connected to the capacitor 100. The control unit 80 controls the charging and discharging of the capacitor 100, thereby controlling the power supply to the fluid discharge unit 20. More specifically, the control unit 80 controls the charging and discharging of the capacitor 100 by switching a switching element (not shown). When the control unit 80 electrically connects the capacitor 100 to a power source (not shown), the capacitor 80 is charged. On the other hand, when the control unit 80 electrically connects the capacitor 100 to the fluid discharge unit 20, the capacitor 80 discharges and a voltage is applied to the fluid discharge unit 20. The control unit 80 repeatedly charges and discharges the capacitor 100 while measuring intraocular pressure, thereby supplying power to the fluid discharge unit 20 multiple times. As will be described later, the control unit 80 starts charging the capacitor 100, for example, when the power of the ophthalmic apparatus 1 is turned on or when an instruction to start intraocular pressure measurement is input. If a sufficient charging time is ensured, the capacitor 100 is charged to a maximum charging voltage VA. Then, when the capacitor 100 is charged to the driving voltage VB or higher, power is supplied to the fluid discharge unit 20 (the capacitor 100 is discharged). Furthermore, for the second and subsequent discharges of air to the subject's eye E, the control unit 80 resumes charging the capacitor 100 and charges the capacitor 100 until the voltage reaches the driving voltage VB or higher. Thereafter, the control unit 80 discharges the capacitor 100 and supplies power to the fluid discharge unit 20 again. Note that the discharge of the capacitor 100 may be performed manually when an operator inputs an operation. Alternatively, the control unit 80 may automatically discharge the capacitor 100 when the voltage of the capacitor 100 reaches the driving voltage VB or higher.

[0028] The control unit 80 functions as a determination unit 80a. The determination unit 80a determines whether the drive voltage VB of the capacitor 100, which is the reference for supplying power to the fluid discharging unit 20, needs to be increased because the intraocular pressure measurement was not performed normally. More specifically, for example, the determination unit 80a receives a detection signal from a light-receiving element (not shown) of the measurement optical system 10 that receives light reflected by the cornea of ​​the subject's eye E. Based on the received detection signal, the determination unit 80a determines whether the cornea of ​​the subject's eye E has been properly applanated. If the determination unit 80a determines that the pressure of the air discharged to the subject's eye E was insufficient and that the cornea of ​​the subject's eye E has not been properly applanated, the determination unit 80a increases the drive voltage VB of the capacitor 100, which is the reference for supplying power to the fluid discharging unit 20 the next time, and determines that a higher power needs to be applied to the fluid discharging unit 20 than the previous time. In the following description, the increased drive voltage VB, determined by the determination unit 80a when it is determined that the drive voltage VB needs to be increased, is referred to as the high drive voltage VC. The value of this high drive voltage VC is set appropriately. For example, the high drive voltage VC may be set to a preset value (e.g., 190 V) that is a predetermined voltage higher than the normal drive voltage VB (185 V in this embodiment). If the corneal applanation is still insufficient when fluid is ejected based on the high drive voltage VC as a reference, a high drive voltage VC (e.g., 195 V) that is a predetermined voltage higher may be used as the reference, and even greater power may be applied to the fluid ejection unit 20. Alternatively, the value of the high drive voltage VC may be determined appropriately based on a detection signal from a light-receiving element. For example, the degree of corneal applanation of the subject's eye E may be estimated from the detection signal from the light-receiving element, and the value of the high drive voltage VC may be determined based on the estimation result.

[0029] In this disclosure, the term "processor" refers to one or more hardware processors configured to execute computer program code (i.e., one or more instructions of a computer program) included in a computer program. In other words, a "processor" is a hardware device capable of executing one or more programmed processes. For example, a "processor" may be a general-purpose or special-purpose processor, such as a CPU, a microprocessor, a GPU, a DFP (Data Flow Processor), or the like.

[0030] In this disclosure, the term "memory" refers to one or more hardware memories that are non-transitory tangible recording media configured to store computer program code and / or data in a manner accessible to a processor. The "memory" may be implemented using memory technologies such as SRAM, SDRAM, non-volatile / flash-type memory, or other types of memory. Computer program code that constitutes a computer program is stored in the memory and executed by the processor to cause the ophthalmic device 1 to perform various functions.

[0031] In this disclosure, the term "circuit" refers to one or more hardware logic circuits configured to enable the ophthalmic device 1 to perform a function. In other words, "circuit" refers to one or more non-programmable devices. For example, a "circuit" may be a custom IC or the like that is non-programmably designed for a specific application.

[0032] In the present disclosure, at least one of a circuit and a processor having a memory storing computer program code causes the ophthalmic apparatus 1 to realize various functions. The expression "at least one of a circuit and a processor" should be interpreted as a disjunction (logical OR), and not as at least one circuit and at least one processor.

[0033] Next, the capacitor 100 of this embodiment will be described below. The capacitor 100 functions as a power supply unit that supplies power to the fluid discharge unit 20. The capacitor 100 of this embodiment is electrically connected to the fluid discharge unit 20 and an external power source (not shown). The capacitor 100 is configured to be selectively connected to the fluid discharge unit 20 and the external power source. More specifically, the connection destination of the capacitor 100 is switched by the control unit 80 between the external power source and the fluid discharge unit 20. When the capacitor 100 is connected to the external power source, the capacitor 100 is charged. On the other hand, when the capacitor 100 is connected to the fluid discharge unit 20, power is supplied (discharged) to the fluid discharge unit 20.

[0034] 3 is a graph (hereinafter referred to as the charging voltage curve) showing the charging voltage characteristics of the capacitor 100 during charging and discharging (during intraocular pressure measurement). When intraocular pressure measurement starts and charging of the capacitor 100 begins, the charging voltage of the capacitor 100 rises sharply. Thereafter, the rate of rise of the charging voltage gradually decreases, and the charging voltage curve forms a curve. The curve then gradually flattens out, and eventually reaches the maximum charging voltage VA of the capacitor 100. When the charging voltage of the capacitor 100 reaches or exceeds a predetermined drive voltage VB, the CPU 81 determines that power can be applied from the capacitor 100 to the fluid discharger 20.

[0035] When the capacitor 100 is discharged, the voltage of the capacitor 100 drops sharply by an amount corresponding to the power supplied to the fluid discharge unit 20, and power is supplied to the fluid discharge unit 20. As a result, air is discharged from the fluid discharge unit 20, and the first fluid discharge is performed. When the first fluid discharge is completed, the control unit 80 charges the capacitor 100 again. At this time, the charging voltage curve rises sharply and reaches the driving voltage VB. When the charging voltage of the capacitor 100 again reaches or exceeds the driving voltage VB, the control unit 80 discharges the capacitor 100 again, and the second fluid discharge is performed. As a result, the voltage of the capacitor 100 drops as in the first discharge, and power is supplied to the fluid discharge unit 20. In this way, in the second and subsequent fluid discharges, the capacitor 100 is repeatedly charged and discharged until the voltage reaches or exceeds the driving voltage VB.

[0036] Next, FIG. 4 compares a charging voltage curve (FIG. 4(a)) with a curve obtained by second-order differentiation of the charging voltage curve (FIG. 4(b), hereinafter referred to as the second-order differential curve). As shown in FIG. 4(b), the second-order differential curve is a downwardly convex curve with a minimum value. As shown in FIG. 4(a), the point on the charging voltage curve when this second-order differential curve reaches its minimum value (t=t1) is located at the apex of the curve (the point on the charging voltage curve where the radius of curvature is smallest). The voltage value on the charging voltage curve at this time is referred to as the reference voltage VX. The capacitor 100 of this embodiment has voltage characteristics in which the reference voltage VX is greater than the drive voltage VB. In other words, the maximum charging voltage VA and capacitance of the capacitor 100 of this embodiment are set so that the reference voltage VX is greater than the drive voltage VB (in this embodiment, the maximum charging voltage is 300 V and the capacitance is 1200 μF).

[0037] FIG. 5 is a diagram comparing the charging voltage curve of the capacitor 100 according to this embodiment (FIG. 5(a)) with the charging voltage curve of the capacitor 100 according to a comparative example (FIG. 5(b)). The capacitor 100 according to the comparative example has a maximum charging voltage VA of 190 V and a capacitance of 1800 μF. Therefore, in the charging voltage curve of the comparative example, the drive voltage VB (185 V) is close to the maximum charging voltage VA. As shown in FIG. 5(b), the reference voltage VX in the charging voltage curve of the comparative example is smaller than the drive voltage VB. On the other hand, in the charging voltage curve of this embodiment, the maximum charging voltage VA is set sufficiently higher than the drive voltage VB, so the reference voltage VX is higher than the drive voltage VB. In the capacitor 100 according to this embodiment, the maximum charging voltage VA is set to be 1.5 times or more, more preferably 1.6 times or more, the drive voltage VB.

[0038] By adopting a capacitor 100 having a charging voltage characteristic in which the reference voltage VX is higher than the driving voltage VB, the time (T) from when the first fluid ejection is completed and charging of the capacitor 100 begins (t=t2) until the driving voltage VB is reached (t=t3) can be shortened compared to the comparative capacitor 100. As a result, the total time required for intraocular pressure measurement can be reduced without replacing the capacitor 100 with a higher-quality capacitor. Note that the high driving voltage VC set when the aforementioned determining unit 80a determines that the driving voltage VB needs to be increased is also lower than the reference voltage VX, as shown in FIG. 5(a). In other words, the high driving voltage VC is set to a value higher than the driving voltage VB and lower than the reference voltage VX.

[0039] (Regarding intraocular pressure measurement processing) Next, with reference to FIG. 6, an intraocular pressure measurement process executed by the ophthalmologic apparatus according to the embodiment will be described. The intraocular pressure measurement process is performed by the CPU 81 of the control unit 80 executing a computer program stored in the storage unit 84. When the intraocular pressure measurement process is started, the CPU 81 starts charging the capacitor 100 (S10). Note that the charging voltage of the capacitor 100 is initially set to zero. Next, the CPU 81 determines whether the charging voltage of the capacitor 100 has reached the driving voltage VB (S20). The CPU 81 repeats S20 until the charging voltage of the capacitor 100 reaches the driving voltage VB. When the charging voltage of the capacitor 100 reaches the driving voltage VB (S20: YES), the CPU 81 terminates charging of the capacitor 100 and discharges the capacitor 100 (S30). That is, the capacitor 100 supplies power to the fluid discharge unit 20 to eject fluid at normal pressure. Note that for the first fluid ejection, discharging to the capacitor 100 may be performed when the charging voltage exceeds the drive voltage VB and reaches (approaches) the maximum charging voltage VA. In this case, step 20 determines whether the maximum charging voltage VA has been reached. In this way, when charging to the maximum charging voltage VA, as shown in FIG. 5(a), the charging voltage curve of the capacitor 100 rises in a curve, exceeds the drive voltage VB and the reference voltage VX, and reaches the maximum charging voltage VA (more precisely, reaches the vicinity of the maximum charging voltage VA).

[0040] When power is supplied to the fluid discharge unit 20, a current flows through the coil 205, generating a magnetic field inside the coil 205. As a result, the moving body 204 moves together with the piston 202, and compressed air is discharged from the testing protrusion 9 toward the subject's eye E (S40). The pressure of this discharged air applanates the cornea of ​​the subject's eye E, and the first intraocular pressure measurement is performed (S50). When the first intraocular pressure measurement is completed, 1 is added to the number of executions N (S60). Note that N is initially set to 0.

[0041] Next, the CPU 81 determines whether the number of executions N has reached an upper limit (e.g., four) (S70). If the number of executions N has not reached the upper limit (S70: NO), the CPU 81 proceeds to step S80. In step S80, the CPU 81 starts charging the capacitor 100 and continues charging until the drive voltage VB is reached (S90). If the drive voltage VB is reached (S90: YES), the CPU 81 discharges the capacitor 100 again (S100). At this time, as shown in FIG. 5(a), when charging starts (t=t2), the charging voltage curve rises at a steep angle and maintains this steep angle until the drive voltage VB is reached (t=t3). Therefore, the time T from when charging starts to the capacitor 100 until the drive voltage VB is reached can be made shorter than that of the capacitor 100 of the comparative example (FIG. 5(b)).

[0042] When the capacitor 100 is discharged, air is discharged (S110), and a second intraocular pressure measurement is performed (S120). After the second intraocular pressure measurement is performed, the CPU 81 (determination unit 80a) determines whether the intraocular pressure measurement was performed normally (whether the drive voltage VB needs to be increased) based on the detection result of the light receiving element (S130). If the intraocular pressure measurement was performed normally (S130: NO), the CPU 81 proceeds to step S60 and increments the number of executions N by 1. On the other hand, if the intraocular pressure measurement was not performed normally in step S130 (S130: YES), the CPU 81 sets the drive voltage VB to a high drive voltage VC (S140) and proceeds to step S60. At this time, as shown in FIG. 5(a), the high drive voltage VC is set to a value greater than the drive voltage VB and less than the reference voltage VX. In this way, if the intraocular pressure measurement cannot be performed normally with the drive voltage VB, a high drive voltage VC greater than the drive voltage VB is set. As a result, a larger amount of power is supplied to the fluid ejection unit 20 than when the driving voltage VB is set, so the pressure of the air ejected in the next intraocular pressure measurement can be increased, thereby enabling normal intraocular pressure measurement.

[0043] In step S70, the CPU 81 determines whether the upper limit number of times has been reached, and if not (S70: NO), charges the capacitor 100 again (S80). Then, the CPU 81 determines whether the charging voltage of the capacitor 100 has reached the drive voltage VB (or the high drive voltage VC if the high drive voltage VC is set) (S90). When the charging voltage of the capacitor 100 has reached the drive voltage VB or the high drive voltage VC (S90: YES), the CPU 81 discharges the capacitor 100 and applies power to the fluid ejection unit 20 (S100). As a result, a third intraocular pressure measurement is performed (S110, S120).

[0044] After the third intraocular pressure measurement, the CPU 81 (determination unit 80a) continues to determine whether the intraocular pressure measurement was performed normally (S130). If the intraocular pressure measurement was not performed normally, the CPU 81 sets the high drive voltage VC (S140). In this manner, each time an intraocular pressure measurement is performed from the second time onward, it is determined whether the intraocular pressure measurement was performed normally. Therefore, for example, even if the second intraocular pressure measurement was performed normally, if the third intraocular pressure measurement was not performed normally, the drive voltage VB is increased to the high drive voltage VC, and high-pressure air is discharged in the next intraocular pressure measurement. Note that if the high drive voltage VC was already set in the previous intraocular pressure measurement and the intraocular pressure measurement is not performed normally again, the already set value of the high drive voltage VC and the value of the power supplied to the fluid discharge unit 20 are further increased.

[0045] In this way, the CPU 81 performs intraocular pressure measurement multiple times while adjusting the drive voltage VB. Then, when the number of executions reaches the upper limit (for example, four times) (S70: YES), the CPU 81 determines the final intraocular pressure from the measurement results up to that point (step S150) and ends the intraocular pressure measurement process. For example, the CPU 81 can calculate the average value of the intraocular pressures measured up to that point and determine this as the final intraocular pressure.

[0046] As described above, the capacitor 100 of the present embodiment has a charging voltage characteristic in which the reference voltage VX is greater than the driving voltage VB. In other words, by appropriately adjusting the capacitor 100 of the present embodiment to a predetermined maximum charging voltage VA and capacitance, the capacitor 100 is configured to have a charging voltage characteristic in which the reference voltage VX is greater than the driving voltage VB. Therefore, particularly when performing fluid ejection for the second or subsequent times, the time required for the charging voltage of the capacitor 100 to reach the driving voltage VB can be shortened. As a result, the total time required for the intraocular pressure measurement process can be shortened compared to the capacitor 100 of the comparative example. Furthermore, the capacitor 100 of the present embodiment has a maximum charging voltage VA set to 1.5 times or more the driving voltage VB. This allows the slope of the charging voltage curve to reach the driving voltage VB during charging to be increased. Therefore, the time required to reach the driving voltage VB can be shortened.

[0047] Here, for example, by connecting multiple capacitors 100 in series, the total maximum charging voltage VA can be increased. Also, by connecting multiple capacitors 100 in parallel, the total capacitance of the capacitors 100 can be increased. Therefore, by appropriately connecting multiple capacitors 100 in series and parallel, the maximum charging voltage VA and capacitance can be changed. However, improving the performance of the capacitors 100 in this way increases the number of components, which leads to higher costs. Furthermore, space is required to install high-performance capacitors 100, which often requires a change in the design of the ophthalmic apparatus 1 and increases its size.

[0048] Furthermore, by using a high-quality capacitor 100 with a large capacitance, it is possible to increase the capacitance while increasing the maximum charging voltage VA. While this avoids the problem of the ophthalmic apparatus 1 becoming larger in size, it has the drawback of the capacitor 100 becoming expensive and increasing product costs. Therefore, in this embodiment, a capacitor 100 with general performance is used, and the maximum charging voltage VA and capacitance of the capacitor 100 are appropriately set to provide the charging voltage characteristics described above. Therefore, the intraocular pressure measurement time is reduced without increasing product costs or the size of the ophthalmic apparatus.

[0049] In the above-described embodiment, the CPU 80 automatically discharges the capacitor 100 when the charging voltage of the capacitor 100 reaches or exceeds the driving voltage VB. However, the CPU 80 may discharge the capacitor 100 based on, for example, an operation signal input from an operator. In this case, for example, the CPU 80 may monitor whether the charging voltage of the capacitor 100 has reached the driving voltage VB, and when the driving voltage VB is reached, the CPU 80 may notify the operator that fluid ejection is possible (power can be supplied to the fluid ejection unit). The operator may be notified by displaying a predetermined message or image on the display unit 7 of the ophthalmic apparatus 1. Alternatively, the operator may be notified by sound. When the operator receives the notification that fluid ejection is possible, the CPU 80 inputs an operation at that timing, and the CPU 80 discharges the capacitor 100. Even when the capacitor 100 is discharged based on such an operation by the operator, the capacitor 100 quickly reaches the driving voltage VB after starting charging, as described above. Therefore, the timing at which the capacitor 100 becomes dischargeable is accelerated, and the total time required for intraocular pressure measurement can be reduced, as in the embodiment.

[0050] E. Examined eye VB driving voltage VA Maximum charging voltage VX Reference Voltage 1 Ophthalmology equipment 20 Fluid discharge section 80 Control unit (control section) 80a Judgment section 100 capacitors

Claims

1. A non-contact tonometry device for measuring intraocular pressure of a subject's eye by detecting deformation of the cornea of ​​the subject's eye, a fluid ejection unit that ejects a fluid onto the subject's eye to deform the cornea of ​​the subject's eye; a capacitor that supplies driving power to the fluid ejection unit by charging and discharging; a control unit that controls charging and discharging of the capacitor to supply power to the fluid discharge unit multiple times and discharge the fluid to the subject's eye multiple times, a charging voltage of the capacitor, which is a reference charging voltage for causing the fluid discharging unit to discharge the fluid once, is set in advance; the control unit is configured to charge the capacitor to a voltage equal to or higher than the drive voltage, discharge the capacitor, and supply power to the fluid discharge unit to perform a first discharge of fluid onto the subject's eye, and to charge the capacitor and discharge the capacitor when the voltage reaches a voltage equal to or higher than the drive voltage, and to supply power to the fluid discharge unit for second and subsequent discharges of fluid, If the voltage curve drawn by the capacitor when charging is called the charging voltage curve, The capacitor has a charging voltage characteristic in which the voltage value at which a curve obtained by second-order differentiation of the charging voltage curve has a minimum value is greater than the driving voltage.

2. The non-contact intraocular pressure measuring device according to claim 1, A non-contact intraocular pressure measuring device, wherein the maximum charging voltage of the capacitor is set to be 1.5 times or more the driving voltage.

3. 3. The non-contact intraocular pressure measuring device according to claim 1, the control unit further includes a determination unit that determines whether the cornea of ​​the subject's eye is not properly applanated and whether the drive voltage needs to be increased when power is supplied to the fluid ejection unit, When the control unit causes the capacitor to supply power to the fluid discharge unit and the determination unit determines that the drive voltage needs to be increased, the control unit causes the capacitor to discharge at the timing when it has been charged to a high drive voltage higher than the drive voltage, thereby supplying greater power to the fluid discharge unit than this time during the next fluid discharge.

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