Non-contact tonometer

Abstract

This non-contact tonometer for measuring intraocular pressure of an eye to be examined in a non-contact manner includes: a discharge means for discharging fluid to a cornea of the eye to be examined to deform the cornea; a corneal deformation detection means for detecting the deformation of the cornea and acquiring a corneal deformation detection signal; and a control means. The control means calculates the intraocular pressure on the basis of a plurality of corneal deformation detection signals obtained by a plurality of measurements. Furthermore, the control means determines the reliability of the plurality of corneal deformation detection signals, and calculates the intraocular pressure on the basis of the plurality of corneal deformation detection signals determined to have low reliability.

Description

Non-contact tonometer

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

[0002] A non-contact tonometer is known that measures the intraocular pressure of a subject's eye by deforming the cornea of ​​the subject's eye and detecting the deformed cornea. When deforming the cornea of ​​the subject's eye, a fluid such as compressed air is ejected from a fluid ejection unit onto the subject's eye, and the pressure of the fluid deforms the cornea of ​​the subject's eye.

[0003] JP 2007-143731

[0004] However, there are cases where good results cannot be obtained even if the measurement is repeated due to reasons such as poor fixation of the subject's eye.

[0005] A typical object of the present disclosure is to provide a non-contact tonometer that can perform stable intraocular pressure measurements.

[0006] In order to solve the above problems, the present disclosure is characterized by having the following configuration. A non-contact tonometer provided by a typical embodiment of the present disclosure measures the intraocular pressure of a subject's eye in a non-contact manner. The non-contact tonometer includes: an ejection means for ejecting a fluid onto the cornea of ​​the subject's eye to deform the cornea; a corneal deformation detection means for detecting the corneal deformation and acquiring a corneal deformation detection signal; and a control means. The control means calculates the intraocular pressure based on multiple corneal deformation detection signals obtained by multiple measurements.

[0007] The non-contact tonometer according to the present disclosure can perform stable intraocular pressure measurements.

[0008] FIG. 1 is a left side view showing the external configuration of an ophthalmic apparatus. FIG. 2 is a diagram showing the internal configuration of the ophthalmic apparatus. FIG. 3 is a diagram showing the configuration of a measurement optical system of the ophthalmic apparatus. FIG. 4 is a graph showing before and after accumulating corneal deformation detection signals detected by the ophthalmic apparatus. FIG. 5 is a graph showing before and after accumulating corneal deformation detection signals detected by the ophthalmic apparatus. FIG. 6 is a graph showing before and after accumulating corneal deformation detection signals detected by the ophthalmic apparatus. FIG. 7 is a flowchart showing intraocular pressure measurement processing executed by the ophthalmic apparatus.

[0009] <Embodiments> 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 IA aligned with the subject's eye (examined eye) E. The ophthalmic apparatus 1 illustrated in this embodiment includes an examination protrusion 9 that protrudes toward the examinee's eye along the examination axis IA, 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 tonometer.

[0010] 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 page in FIG. 1 is defined as the Z direction (front-back direction), the up-down direction of the page as the Y direction (up-down direction), and the depth direction of the page as the X direction (left-right direction). An examination axis IA is parallel to the Z direction and perpendicular to the X-Y plane. In detail, the left side of the page (the subject side) in FIG. 1 is defined as the front side of the ophthalmic apparatus 1, and the right side of the page is defined as the rear side of the ophthalmic apparatus 1. The upper side of the page in FIG. 1 is defined as the upper side of the ophthalmic apparatus 1, and the lower side of the page is defined as the lower side of the ophthalmic apparatus 1. The front side of the page in FIG. 1 is defined as the left side of the ophthalmic apparatus 1, and the depth side of the page is defined as the right side of the ophthalmic apparatus 1. The Z direction is parallel to the examination axis IA.

[0011] 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.

[0012] As an example, the drive unit 4 of this embodiment uses an actuator (not shown) such as a motor to move the housing 3 in the front-to-back, up-down, and left-to-right directions (three-dimensional directions) relative to the base 2. This moves the relative position of the housing 3 with respect to the subject's face (or the subject's eye). However, the configuration of the drive unit 4 can also be changed. For example, the drive unit 4 may move the face support unit 5 to move the relative position of the housing 3 with respect to the subject's face. 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-to-back and left-to-right directions and also move the face support unit 5 in the up-to-down direction to move the relative position of the housing 3 with respect to the subject's face.

[0013] The housing 3 includes an examination protrusion (nozzle) 9, a face imaging 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 toward the eye to be examined along an examination axis IA. The examination axis IA 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 E.

[0014] 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.

[0015] 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 (control means) 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.

[0016] 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 the 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. 2). The inspection protrusion 9 discharges compressed air to the outside of the device.

[0017] 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 compressed air. When the 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.

[0018] 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.

[0019] 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 84 (e.g., a non-volatile memory) is a non-transitory storage medium that can retain its contents even when the power supply is interrupted. 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 imaging unit 12, and the like.

[0020] 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.

[0021] 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 recorded in the memory and executed by the processor to cause the ophthalmic apparatus 1 to perform various functions.

[0022] 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, the term "circuit" refers to one or more non-programmable devices. For example, the "circuit" may be a custom IC or the like that is non-programmably designed for a specific application.

[0023] 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.

[0024] The configuration of the measurement optical system of the ophthalmic apparatus 1 will be described with reference to Fig. 3. The left-right direction of the page in Fig. 3 is the Y direction (vertical direction), the up-down direction of the page is the Z direction (front-back direction), and the depth direction of the page is the X direction (horizontal direction). The examination axis IA is parallel to the Z direction and perpendicular to the X-Y plane. In detail, the lower side (subject side) of the page in Fig. 3 is the front side of the ophthalmic apparatus 1, and the upper side of the page is the rear side of the ophthalmic apparatus 1. The left side of the page in Fig. 3 is the upper side of the tonometer 1, and the right side of the page is the lower side of the tonometer 1. The Z direction is parallel to the examination axis IA.

[0025] An image of the eye to be examined illuminated by the infrared illumination light source 30 is formed on the CCD camera 35 via the beam splitter 31, the objective lens 32, the dichroic mirror 33, the imaging lens 37, and the filter 34. That is, the optical system from the beam splitter 31 to the CCD camera 35 has an imaging element and is used as an observation optical system for observing the anterior segment of the eye to be examined. In this case, the examination axis IA is used as the observation optical axis.

[0026] The filter 34 transmits light from the light source 30 and the infrared light source 40 for alignment, but is opaque to light from a light source 50 for corneal deformation detection (described later) and visible light. The image formed on the CCD camera 35 is displayed on a display unit 85.

[0027] Infrared light projected from the light source 40 through the projection lens 41 is reflected by the beam splitter 31 and projected from the front onto the subject's eye. A corneal bright spot formed at the corneal vertex by the light source 40 is imaged on the CCD camera 35 via the beam splitter 31 to the filter 34 and is used to detect alignment in the vertical and horizontal directions. In other words, the optical system from the beam splitter 31 to the CCD camera 35 has an image sensor and is used as a detection optical system for detecting the alignment state of the subject's eye in the vertical and horizontal directions. In this case, the examination axis IA is used as the alignment optical axis. In this embodiment, the detection optical system also serves as an observation optical system for observing the anterior segment.

[0028] The fixation optical system 48 has an optical axis L1 that is coaxial with (substantially coincident with) the examination axis IA, and presents a fixation target to the subject's eye E from a frontal direction. In this case, the optical axis L1 is used as the fixation optical axis. The fixation optical system 48 has, for example, a visible light source (fixation lamp) 45, a projection lens 46, and a dichroic mirror 33, and projects light onto the subject's eye E to fixate the subject's eye E in a frontal direction. The visible light source 45 may be a light source such as an LED or a laser. The visible light source 45 may also be, for example, a pattern light source such as a point light source, a slit light source, or a ring light source, or a two-dimensional display such as a liquid crystal display.

[0029] Visible light emitted from the light source 45 passes through the projection lens 46, is reflected by the dichroic mirror 33, passes through the objective lens 32, and is then projected onto the fundus of the subject's eye E. This causes the subject's eye E to fixate on a fixation point in the front direction, and the direction of the line of sight is fixed. Note that the visible light emitted from the light source 45 is converted into a parallel beam of light by passing through the projection lens 46 and the objective lens 32.

[0030] The corneal deformation detection optical system 500 includes a light projecting optical system 500a and a light receiving optical system 500b, and is used to detect the deformation state of the cornea Ec of the test eye. Each of the optical systems 500a and 500b is disposed in the measurement unit 100 and is moved three-dimensionally by the drive unit 4.

[0031] Light emitted from the light source 50 is converted into a substantially parallel beam by a collimator lens 51, reflected by a beam splitter 52, and then becomes coaxial (coincident) with the optical axis L3 of a light-receiving optical system 70b (described later), and is projected onto the cornea Ec of the subject's eye. The light reflected by the cornea Ec of the subject's eye becomes coaxial (coincident) with the optical axis L2 of a light-projecting optical system 70a (described later), passes through a lens 53, is reflected by a beam splitter 55, passes through a pinhole plate 56, and is received by a photodetector 57. The lens 53 is coated with a coating that is opaque to the light from the light source 30 and the light source 40. The corneal deformation detection optical system is positioned so that the amount of light received by the photodetector 57 is maximized when the subject's eye is in a predetermined deformation state (e.g., applanation state).

[0032] The corneal deformation detecting optical system 500 also serves as a part of the first working distance detecting optical system, and the light projecting optical system of the first working distance detecting optical system also serves as the light projecting optical system 500a of the corneal deformation detecting optical system 500. The light receiving optical system 600b that receives light reflected by the cornea Ec of the test eye by the light source 50 has, for example, the lens 53, beam splitter 58, condenser lens 59, and position detecting element 60 of the light projecting optical system 500a, and forms an optical axis L2 as a light receiving optical axis.

[0033] Illumination light projected from the light source 50 and reflected by the cornea Ec of the subject's eye forms a target image, which is a virtual image of the light source 50. The light from this target image passes through a lens 53 and a beam splitter 55, is reflected by a beam splitter 58, passes through a condenser lens 59, and is incident on a one-dimensional or two-dimensional position-sensing element 60, such as a PSD or a line sensor. When the subject's eye E (cornea Ec) moves in the working distance direction (Z direction), the target image generated by the light source 50 also moves on the position-sensing element 60. Therefore, the control circuit 20 obtains working distance information based on the output signal from the position-sensing element 60. Note that the output signal from the position-sensing element 60 in this embodiment is used for alignment (coarse adjustment) in the working distance direction (Z direction). The light-receiving optical system 600b of the first working distance detection optical system does not have as high a magnification as the light-receiving optical system 70b (described later). Therefore, the distance detection range of the position-sensing element 60 in the Z direction is wider than that of the light-receiving element 77.

[0034] The corneal thickness measuring optical system includes a light projecting optical system 70a, a light receiving optical system 70b, and a fixation optical system 48, and is used to measure the corneal thickness of the subject's eye E. The light projecting optical system 70a also serves as a part of the corneal deformation detecting optical system 500 and the first working distance detecting optical system.

[0035] The light projection optical system 70a has an optical axis L2 as a light projection optical axis, and irradiates illumination light (measurement light) obliquely toward the cornea Ec of the test eye. The light projection optical system 70a includes, for example, an illumination light source 71, a condenser lens 72, a light limiting member 73, a concave lens 74, and a lens 53 that also serves as the corneal deformation detection optical system 500. The illumination light source 71 is a visible light source or an infrared light source (including near-infrared), such as an LED or laser. The condenser lens 72 condenses the light emitted from the light source 71. Note that the light source 50 and the light source 71 each use the same wavelength band.

[0036] The light limiting member 73 is disposed in the optical path of the light projection optical system 70a and limits the light emitted from the light source 71. The light limiting member 73 is disposed at a position that is approximately conjugate with the cornea Ec. For example, a pinhole plate, a slit plate, or the like is used as the light limiting member 73. The light limiting member 73 is used as an aperture that passes a portion of the light emitted from the light source 71 and blocks the other light. The light projection optical system 70a then forms a predetermined pattern light beam (for example, a spot light beam or a slit light beam) on the cornea of ​​the subject's eye E.

[0037] The light-receiving optical system 70b has a light-receiving element 77 and receives reflected light of the illumination light from the front and back surfaces of the cornea of ​​the eye E. The light-receiving optical system 70b is disposed approximately symmetrically with the light-projecting optical system 70a with respect to the optical axis L1. The light-receiving optical system 70b has, for example, a light-receiving lens 75, a concave lens 76, and a light-receiving element 77, and forms an optical axis L3 as a light-receiving optical axis. The light-receiving optical system 70b also serves as a second working distance detection optical system that detects the alignment state in the Z direction with respect to the eye E.

[0038] The light-receiving element 77 has a plurality of photoelectric conversion elements and receives light reflected from the front and back surfaces of the cornea. The light-receiving element 77 may be a light-detecting device such as a one-dimensional line sensor or a two-dimensional area sensor. The light-receiving optical system 70b of the corneal thickness measurement optical system and the second working distance detection optical system performs observation at a high magnification. Therefore, the distance detection range of the light-receiving element 77 in the Z direction is narrower than that of the position detection element 60.

[0039] When the subject's eye E (subject's cornea Ec) moves in the working distance direction (Z direction), the reflected light of the light source 71 on the subject's cornea Ec also moves on the light-receiving element 77, and the control unit 80 obtains working distance information based on the output signal from the light-receiving element 77 of the second working distance detection optical system. Furthermore, the control unit 80 determines the state of corneal deformation and blinking of the subject's eye E from the output signal from the light-receiving element 77, and controls the drive of the solenoid 203.

[0040] Light emitted from the illumination light source 71 is condensed by the condenser lens 72 and illuminates the light-limiting member 73 from behind. The light from the light source 71 is then limited by the light-limiting member 73, and then focused (condensed) by the lens 53 near the cornea Ec of the subject's eye. For example, a pinhole image (when a pinhole plate is used) or a slit image (when a slit plate is used) is formed near the cornea Ec of the subject's eye. At this time, the light from the light source 71 is focused near the intersection with the visual axis on the cornea Ec.

[0041] When illumination light is projected onto the cornea Ec of the subject's eye by the light projection optical system 70a, the reflected light of the illumination light from the cornea Ec of the subject's eye travels in a direction symmetrical to the direction of the projected light beam with respect to the optical axis L1. The reflected light is then focused onto the light receiving surface of the light receiving element 77 by the light receiving lens 75.

[0042] In addition, the lens 53, which is used in both the light receiving optical system 500b, 600b and the light projecting optical system 70a, is positioned so as to focus the reflected light from the cornea Ec of the test eye caused by the light source 50 at the center of the hole in the pinhole plate 56, and to focus the illumination light from the light source 71 on the front and back surfaces of the cornea Ec of the test eye.

[0043] The face photographing unit 90 is an optical system for photographing a face including at least one of the left and right eyes to be examined. The face photographing unit 90 of this embodiment mainly includes, for example, an image sensor 91 and an imaging lens 92.

[0044] The face imaging unit 90 is provided at a position where it can capture an image of both eyes of the subject when the measurement optical system 10 is in its initial position. In this embodiment, the initial position of the measurement optical system 10 is set to a position shifted to the right with respect to the optical axis L1 of the measurement optical system 10 to facilitate testing of the right eye. Therefore, the face imaging unit 90 is provided at a position where it can capture an image of both eyes of the subject when the measurement optical system 10 is in its initial position shifted to the right. For example, the face imaging unit 90 is disposed at the mechanical center when the measurement optical system 10 is in its initial position. If the initial position is set based on, for example, half the interpupillary distance, i.e., the interpupillary distance of one eye, the face imaging unit 90 may be disposed at a position shifted to the left or right by the interpupillary distance of one eye from the mechanical center of the device body.

[0045] The face photographing unit 90 of this embodiment is moved together with the measurement optical system 10 by the driving unit 4. Of course, the face photographing unit 90 may be configured to be fixed to the base 2 and not move, for example.

[0046] The imaging lens 92 may be, for example, a wide-angle lens. Examples of the wide-angle lens include a fisheye lens and a conical lens. By including a wide-angle lens, the face imaging unit 90 can capture an image of the subject's face with a wide angle of view.

[0047] In this embodiment, the control unit 80 calculates intraocular pressure based on multiple corneal deformation detection signals acquired by the photodetector 57. For example, the control unit 80 combines the multiple corneal deformation detection signals through a process such as integration (sequential addition or multiplication), and calculates the intraocular pressure value using the combined corneal deformation detection signal. FIG. 4 shows a curve ( FIG. 4A ) of a single highly reliable corneal deformation detection signal K, curves ( FIGS. 4B and 4C ) of less reliable corneal deformation detection signals K1 and K2, and a curve ( FIG. 4D ) of a corneal deformation detection signal K3 obtained by integrating multiple less reliable corneal deformation detection signals K1 and K2. In each curve, the vertical direction indicates the amount of light received by the photodetector 57, and the horizontal direction indicates elapsed time. When calculating the intraocular pressure value, the control unit 80 references the maximum value M of the peak that appears first on the curve.

[0048] In the case of corneal deformation detection signals K1 and K2 with low reliability, the maximum values ​​M1 and M2 of the first peaks are output lower than those of the curve of the corneal deformation detection signal K with high reliability, as shown in the example curves of Figures 4B and 4C. Therefore, when the curve of the corneal deformation detection signal with low reliability is integrated, the maximum value M3 of the first peak of the integrated corneal deformation detection signal K3 increases compared to before integration, as shown in the example curve of Figure 4D. Therefore, the control unit 80 integrates the corneal deformation detection signal multiple times, and uses the corneal deformation detection signal with low reliability to calculate the intraocular pressure value.

[0049] Next, the control unit 80 of this embodiment will be described below with reference to Figures 4 and 5. First, the examiner sets a predetermined threshold value P1 (hereinafter referred to as the first threshold value) at which the accumulation of multiple corneal deformation detection signals is to be terminated. Furthermore, the examiner sets a threshold value P2 (hereinafter referred to as the second threshold value) for the maximum value of the multiple corneal deformation detection signals to be accumulated. Furthermore, the examiner sets the number of consecutive error determinations (hereinafter referred to as the accumulation start count) at which intraocular pressure is calculated based on the accumulation of multiple corneal deformation detection signals.

[0050] Next, the examiner switches the setting from calculating the intraocular pressure based on a single corneal deformation signal to calculating the intraocular pressure based on multiple corneal deformation detection signals, except when the setting to calculate the intraocular pressure based on multiple corneal deformation detection signals has already been changed.

[0051] Next, the examiner adjusts the alignment between the subject's eye E and the ophthalmic apparatus 1. The examiner operates the operation unit 8 to move the ophthalmic apparatus 1 and align the examination axis IA with the subject's eye E. Once the alignment adjustment is complete, the examiner operates the operation unit 8 to start measurement.

[0052] When the examiner operates the operation unit 8 to start measurement, the number of measurements N for the subject's eye E is incremented by 1 (Step S10). Note that N is initially set to 0. The control unit 80 controls the power supply to the fluid discharge unit 20, causing the fluid discharge unit 20 to discharge air (Step S20). The cornea of ​​the subject's eye E gradually deforms due to the discharged fluid, and when it reaches an applanation state, a maximum amount of light is incident on the photodetector 57 (Step S30). Next, the control unit 80 determines whether the maximum value of the peak shape that appears the first time the corneal deformation detection signal incident on the photodetector 57 is equal to or greater than a highly reliable value, i.e., a value P at which intraocular pressure can be calculated based on a single corneal deformation detection signal (Step S40). If the corneal deformation detection signal incident on the photodetector 57 is equal to or greater than the value P, the corneal deformation detection signal is determined to be highly reliable, and the control unit 80 calculates the intraocular pressure value based on the output signal from the pressure sensor 212 and the detection signal from the photodetector 57. Then, the measurement results are output to the display unit 7 (step S50). When the output of the measurement results is completed, the control unit 80 ends the process.

[0053] If the maximum value of the corneal deformation detection signal detected by the photodetector 57 is less than the value P in step S40, the control unit 80 determines that the corneal deformation detection signal has low reliability. The control unit 80 determines whether the number of times N of measurements performed on the subject's eye E is equal to or greater than the accumulation start number (step S60). If the number of times N is less than the accumulation start number, the control unit 8 repeats the operation of adding 1 to the number of times N (step S10).

[0054] If the number of executions N is equal to or greater than the accumulation start number, the control unit 80 determines whether the maximum value of the corneal deformation detection signal detected by the photodetector 57 is equal to or greater than the second threshold value P2 (step S70). If the maximum value of the detected corneal deformation detection signal is less than the second threshold value P2, the control unit 80 determines that there was a defect in the measurement, discards the corneal deformation detection signal data (step S80), and repeats the operation of adding 1 to the number of executions N (step S10).

[0055] If the maximum value of the corneal deformation detection signal detected by the photodetector 57 is equal to or greater than the second threshold value P2, the control unit 80 integrates the detected corneal deformation detection signal (step S90). The control unit 8 then determines whether the maximum value of the peak shape that appears the first time in the integrated corneal deformation detection signal is equal to or greater than the first threshold value P1 (step S100). If the maximum value of the integrated corneal deformation detection signal is less than the integration end value, the control unit 8 repeats the operation of adding 1 to the execution count N (step S10).

[0056] If the maximum value of the integrated corneal deformation detection signals is equal to or greater than the first threshold value P1, the control unit 80 calculates an intraocular pressure value based on the output signal from the pressure sensor 212 and the integrated corneal deformation detection signal, and outputs the measurement result to the display unit 7 with a mark 7a (see FIG. 2) to indicate that the measurement result has been calculated based on the integration of multiple corneal deformation detection signals (step S110). When the output of the measurement result is complete, the control unit 80 ends the process.

[0057] As described above, the ophthalmologic apparatus 1 of the embodiment includes the fluid ejection means 20 (ejection means) that ejects a fluid onto the cornea of ​​the subject's eye to deform the cornea, the corneal deformation detection optical system 500 (corneal deformation detection means) that detects the corneal deformation and acquires a corneal deformation detection signal, and the control unit 80 (control means), and the control unit 80 calculates the intraocular pressure based on multiple corneal deformation detection signals obtained by multiple measurements. This absorbs variations between measurements and improves (stabilizes) the accuracy of the calculated intraocular pressure compared to when the intraocular pressure is calculated from a single corneal deformation detection signal.

[0058] In this embodiment, the control unit 80 calculates intraocular pressure based on multiple corneal deformation detection signals determined to have low reliability. As a result, corneal deformation detection signals determined to have low reliability, which would have been discarded in the past, are used to calculate intraocular pressure. Therefore, intraocular pressure can be calculated stably even when the reliability of the corneal deformation detection signal is repeatedly low. For example, in the past, if the corneal deformation detection signal during intraocular pressure measurement was weak due to poor fixation or other reasons, it was determined to be an error, and measurements had to be performed multiple times until a strong detection signal was detected. However, the ophthalmologic apparatus 1 of this embodiment can reduce the number of intraocular pressure measurements even for a subject's eye that repeatedly receives error determinations during intraocular pressure measurement.

[0059] In this embodiment, the control unit 80 calculates the intraocular pressure by integrating multiple corneal deformation detection signals until the corneal deformation detection signal reaches or exceeds a first threshold value P1. Therefore, the reliability of the calculated intraocular pressure can be increased by integrating multiple corneal deformation detection signals. Note that the first threshold value P1 may be set to a value higher than the value P. This allows the reliability of the intraocular pressure calculated using highly reliable corneal deformation detection signals to be approached, even when integrating corneal deformation detection signals with low reliability.

[0060] In this embodiment, the control unit 80 outputs the intraocular pressure calculated based on a plurality of corneal deformation detection signals in a state in which it can be determined that the intraocular pressure is different from the intraocular pressure calculated based on a single corneal deformation detection signal (for example, in a state in which the mark 7a is attached). Therefore, the examiner can distinguish whether the intraocular pressure has been calculated based on a single corneal deformation detection signal or a plurality of corneal deformation detection signals.

[0061] In this embodiment, the control unit 80 can switch between calculating the intraocular pressure based on a single corneal deformation signal or calculating the intraocular pressure based on multiple corneal deformation detection signals according to a setting operated by the examiner, thereby allowing the examiner to select whether to calculate the intraocular pressure based on a single corneal deformation signal or based on multiple corneal deformation detection signals.

[0062] In this embodiment, the control unit 80 integrates, among the multiple corneal deformation detection signals, corneal deformation detection signals whose maximum value is equal to or greater than the second threshold value P2. As a result, corneal deformation detection signals whose maximum value is less than the second threshold value P2 are considered to be corneal deformation detection signals resulting from imperfect intraocular pressure measurement, and are therefore excluded from integration. This improves the accuracy of the calculated intraocular pressure.

[0063] In this embodiment, the control unit 80 calculates intraocular pressure by processing a single corneal deformation detection signal that has been determined to have high reliability. As a result, the intraocular pressure can be calculated using only one corneal deformation detection signal that has high reliability.

[0064] In the above-described embodiment, the measurement result is output to the display unit 7 with a mark 7a attached thereto so that it can be seen that the measurement result has been calculated based on the summation of multiple corneal deformation detection signals. However, for example, the selection of a mode for accumulating corneal deformation detection signals may be indicated on the display unit 7. Since intraocular pressure calculated based on multiple corneal deformation detection signals may contain errors compared to intraocular pressure calculated based on a single corneal deformation detection signal, it is sufficient if an indication can be provided that allows the intraocular pressure calculated based on multiple corneal deformation detection signals to be distinguished from intraocular pressure calculated based on a single corneal deformation detection signal.

[0065] In the above-described embodiment, the intraocular pressure is calculated based on data obtained by integrating multiple corneal deformation detection signals with low reliability, each of which is less than the value P and equal to or greater than the second threshold value P2. However, for example, when the reliability of the corneal deformation detection signals is low, the intraocular pressure value may be calculated based on each detection signal without integrating the multiple corneal deformation detection signals, and the average of the calculated intraocular pressure values ​​may be output as the measurement result. In such a case, the number of corneal deformation detection signals used to calculate the average may be determined in advance. Furthermore, as the measurement progresses, the intraocular pressure value may be calculated from the corneal deformation detection signal detected at the time the examiner performs an operation based on the operation performed by the examiner, and the average of the respective intraocular pressure values ​​may be output as the measurement result.

[0066] E: Eye to be inspected 1: Ophthalmic device 20: Fluid ejection unit 80: Control unit 57: Photodetector 212: Pressure sensor

Claims

1. A non-contact tonometer for measuring the intraocular pressure of a subject's eye without contact, comprising: an ejection means for ejecting a fluid onto the cornea of ​​the subject's eye to deform the cornea; a corneal deformation detection means for detecting the corneal deformation and acquiring a corneal deformation detection signal; and a control means, wherein the control means calculates the intraocular pressure based on a plurality of the corneal deformation detection signals obtained by multiple measurements.

2. A non-contact tonometer according to claim 1, wherein the control means determines the reliability of the plurality of corneal deformation detection signals, and calculates the intraocular pressure based on the plurality of corneal deformation detection signals determined to have low reliability.

3. A non-contact tonometer according to claim 1 or 2, characterized in that the control means calculates the intraocular pressure by integrating the plurality of corneal deformation detection signals until the signal reaches or exceeds a first threshold, which is a predetermined threshold.

4. A non-contact tonometer according to any one of claims 1 to 3, characterized in that the control means outputs an intraocular pressure calculated based on the plurality of corneal deformation detection signals in a state in which it can be determined that the calculated intraocular pressure differs from an intraocular pressure calculated based on a single corneal deformation detection signal.

5. A non-contact tonometer according to any one of claims 1 to 4, wherein the control means switches between calculating intraocular pressure based on the single corneal deformation detection signal and calculating intraocular pressure based on the multiple corneal deformation detection signals in accordance with a setting made by the examiner.

6. A non-contact tonometer according to any one of claims 1 to 5, wherein the control means integrates, from among the plurality of corneal deformation detection signals, corneal deformation detection signals whose maximum value is equal to or exceeds a second threshold, which is a predetermined threshold.

7. A program used in a non-contact tonometer that measures the intraocular pressure of a subject's eye without contact, characterized in that, when executed by a control means of the non-contact tonometer, the program causes the non-contact tonometer to execute the following steps: an ejection step of ejecting a fluid onto the cornea of ​​the subject's eye to deform the cornea; a corneal deformation detection step of detecting the corneal deformation and acquiring a corneal deformation detection signal; and a calculation step of calculating the intraocular pressure based on multiple corneal deformation detection signals obtained by multiple measurements.

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