JP5924219B2 - Non-contact tonometer - Google Patents

Description

  The present invention relates to a non-contact tonometer that measures the intraocular pressure of a subject's eye in a non-contact manner.

In a non-contact tonometer that measures the intraocular pressure of the subject's eye in a non-contact manner by optically detecting the deformation state of the cornea when fluid is sprayed onto the eye's cornea via a nozzle, the corneal thickness of the eye to be examined There is known an apparatus that includes an optical system for measuring the eye pressure and corrects the intraocular pressure value of the eye to be examined based on the obtained measurement result (see Patent Document 1).
Further, as in Patent Document 2, when measuring the corneal thickness, a light beam is obliquely incident on the eye to be examined, the reflected light on the cornea is received by a light receiving element such as a line sensor, and the reflected light is received on the front and back surfaces of the cornea. There was an apparatus for measuring the corneal thickness based on the peak value of the signal. In such an apparatus, the alignment in the working distance direction is performed on the basis of the peak value of the light reception signal of the reflected light on the cornea surface during both intraocular pressure measurement and corneal thickness measurement.
JP-T 8-507463 JP 2002-102170 A

  However, for the human eye, the amount of reflection on the back surface is smaller than that on the front surface, and when the light receiving element receives light, the reflected light on the back surface has a smaller peak than the reflected light on the front surface. Furthermore, when the alignment reference in the working distance direction is matched to the corneal surface, the amount of reflected light on the back surface decreases, and the amount decreases as the corneal thickness increases. Therefore, the conventional apparatus that aligns the reference position with the cornea surface has a problem that the peak of reflected light on the back surface of the cornea received by the light receiving element is small, and the measurement accuracy of the cornea thickness is reduced. It was.

  In view of the above problems, an object of the present invention is to provide a non-contact tonometer that can accurately measure the corneal thickness of the eye to be examined.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) A non-contact tonometer that has a first detector for detecting a reflection signal from the corneal surface of the subject's eye and measures intraocular pressure for measuring the intraocular pressure of the subject's eye in a non-contact manner. Corneal thickness measurement means for measuring the corneal thickness of the eye to be examined in a non-contact manner, having a second detector for detecting a reflected signal from the corneal surface and a reflected signal from the corneal back surface, An observation optical system for observing the anterior ocular segment, the measurement unit comprising an observation optical system shared in vertical alignment in the intraocular pressure measurement unit and the corneal thickness measurement unit, and an electric motor A moving mechanism that moves the measuring unit relative to the eye to be examined; and a third detector that is provided in the measuring unit and detects a reflected signal from the cornea of the eye to be examined. That detects the alignment state in the front-rear direction Detection means, and the alignment detection means switches the alignment reference position on the cornea set for detecting the alignment state between intraocular pressure measurement and corneal thickness measurement, and the alignment with respect to the switched alignment reference position It is characterized by detecting a state.

  According to the present invention, it is possible to accurately measure the corneal thickness of the subject's eye and correct the intraocular pressure value of the subject's eye with high accuracy.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an external configuration diagram of a non-contact type tonometer according to the present embodiment.

  The non-contact tonometer 100 is a so-called stationary non-contact tonometer, and is provided on a base 101, a face support unit 102 attached to the base 101, and movable on the base 101. A movable table 103 and a measuring unit (measuring unit) 104 that is movably provided on the movable table 103 and accommodates a measurement system and an optical system described later are provided. The measuring unit 104 is moved in the left-right direction (X direction), the up-down direction (Y direction), and the front-back direction (Z direction) with respect to the eye E by an XYZ driving unit 106 provided on the moving table 103. The movable table 103 is moved in the X direction and the Z direction on the base 1 by operating the joystick 105. Further, when the examiner rotates the rotary knob 105 a, the measuring unit 104 is moved in the Y direction by the Y driving of the XYZ driving unit 106. On the top of the joystick 105, a measurement start switch 105b is provided. A display monitor 36 is provided on the moving table 103.

  FIG. 2 is a side view of the fluid ejection mechanism of the non-contact tonometer and a diagram showing the main part of the control system.

  The cylinder portion 1 for air compression is provided to be inclined with respect to the horizontal line of the tonometer body. When electric charge (current, voltage) as drive energy is applied to the rotary solenoid 3, the piston 2 is pushed up along the cylinder 1 through the arm 4 and the connecting rod (piston rod) 5. The air compressed in the air compression chamber 11 that communicates with the cylinder portion 1 as the piston 2 rises is ejected from the nozzle 6 toward the cornea of the eye E. The rotary solenoid 3 is provided with a coil spring (not shown). When the applied charge is cut, the piston 2 that has been lifted by the biasing force in the downward direction of the coil spring is lowered and returned to the initial position.

  The transparent glass plate 7 holds the nozzle 6 and provides light for detecting corneal deformation, light for observing the anterior segment for observing the anterior segment from the front direction, alignment light, and light for measuring the corneal thickness. Used as a transmissive member for transmission. Further, the glass plate 7 a arranged on the eye side of the glass plate 7 also serves to prevent foreign substances from entering the internal optical system from the outside, and the glass plate 7 b serves as a side wall of the air compression chamber 11. ing. A transparent glass plate 9 provided on the back surface of the nozzle 6 constitutes the rear wall of the air compression chamber 11 and transmits observation light and alignment light. Behind the glass plate 9 is an optical system 8 for observation and alignment described later. The pressure sensor 12 detects the pressure in the air compression chamber 11. The resistance until the initial speed is applied to the piston 2 is reduced by the air vent hole 13, and a pressure change almost proportional to time can be obtained at the time of the rise of pressure.

  The control circuit 20 includes a pressure detection processing circuit 21 for the pressure sensor 12, a signal detection processing circuit 22 for a photodetector 57 of a corneal deformation detection optical system, which will be described later, and a light receiving element 77 for working distance detection and corneal thickness measurement. Signal detection processing circuit 28, signal detection processing circuit 26 for working distance detection position detection element 60, signal detection processing circuit 27 for CCD camera 35, drive circuit 23 for driving rotary solenoid 3, measurement data, etc. A memory 24 for storing is connected. The control circuit 20 is connected to various light sources (anterior segment illumination light source 30, light source 40, light source 45, light source 50, light source 71) provided in the optical system shown in FIG. Take control.

  FIG. 3 is a principal view of the upper-view optical system of the non-contact tonometer. The eye image illuminated by the infrared illumination light source 30 forms an image on the CCD camera 35 via the beam splitter 31, the objective lens 32, the beam splitter 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 image sensor and is used as an observation optical system for observing the anterior eye portion to be examined. In this case, the optical axis L1 is used as an observation optical axis.

  The filter 34 transmits light from the light source 30 and the alignment light source 40, and has a characteristic that is opaque to light from a light source 50 for detecting corneal deformation described later and visible light. The image formed on the CCD camera 35 is displayed on the monitor 36.

  Infrared light projected from the alignment infrared light source 40 via the projection lens 41 is reflected by the beam splitter 31 and projected onto the eye to be examined from the front. The corneal bright spot formed at the apex of the cornea by the light source 40 forms an image on the CCD camera 35 via the beam splitter 31 to the filter 34 and is used for alignment detection in the vertical and horizontal directions. That is, 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 in the vertical and horizontal directions with respect to the eye to be examined. In this case, the optical axis L1 is used as an alignment optical axis. In the present embodiment, the detection optical system also serves as an observation optical system for observing the anterior segment.

  The fixation optical system 48 has an optical axis L1 and presents a fixation target with respect to the eye E from the front direction. In this case, the optical axis L1 is used as a fixation optical axis. The fixation optical system 48 includes, for example, a visible light source (fixation lamp) 45, a projection lens 46, and a dichroic mirror 33, and projects light for fixing the eye E in the front direction onto the eye E. As the visible light source 45, a light source such as an LED or a laser is used. For the visible light source 45, 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 is used.

  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 eye E. As a result, the eye E is in a state of fixing the fixation point in the front direction, and the line-of-sight direction is fixed. The visible light emitted from the light source 45 passes through the projection lens 46 and the objective lens 32 and is converted into a parallel light beam.

  The corneal deformation detecting optical system includes a light projecting optical system 500a and a light receiving optical system 500b, and is used for detecting a deformed state of the cornea Ec. Each of the optical systems 500a and 500b is disposed in the measurement unit 104 and is three-dimensionally moved by the XYZ driving unit 106. Of course, it may be a handheld device.

  The light projecting optical system 500a has an optical axis L3 as a light projecting optical axis, and irradiates illumination light toward the cornea Ec of the eye E from an oblique direction. The light projecting optical system 500a includes, for example, an infrared light source 50, a collimator lens 51, and a beam splitter 52. The light receiving optical system 500b includes a photodetector 57 and receives the reflected light of the illumination light from the cornea Ec of the eye E. The light receiving optical system 500b is disposed substantially symmetrically with the light projecting optical system 500a with respect to the optical axis L1. The light receiving optical system 500b includes, for example, a lens 53, a beam splitter 55, a pinhole plate 56, and a photodetector 57, and forms an optical axis L2 as a light receiving optical axis.

  The light emitted from the light source 50 is made into a substantially parallel light beam by the collimator lens 51, reflected by the beam splitter 52, and then coaxial (coincidence) with an optical axis L3 of a light receiving optical system 70b described later, and projected onto the cornea Ec of the eye to be examined. Lighted. The light reflected by the cornea Ec becomes coaxial (coincidence) with an optical axis L2 of a light projecting optical system 70a described later, passes through the lens 53, is reflected by the beam splitter 55, passes through the pinhole plate 56, and passes through the photo detector. 57 receives the light. The lens 53 is provided with a coating that has a characteristic that does not transmit light from the light source 30 and the light source 40. The optical system for detecting corneal deformation is arranged so that the amount of light received by the photodetector 57 is maximized when the eye to be examined is in a predetermined deformed state (flat state).

  As in the present embodiment, the corneal deformation detection optical system is arranged so as to be inclined with respect to the optical axis L1 that is the observation optical axis, whereby one of the light source 50 and the optical element of the first working distance detection optical system, which will be described later, is provided. The part can also be used. Thereby, the configuration of the apparatus can be simplified.

The corneal deformation detection optical system also serves as a part of the first working distance detection optical system. The projection optical system of the first working distance detection optical system includes the projection optical system 500a of the corneal deformation detection optical system. Combined use. Receiving optical system 600b for receiving the light reflected by the cornea Ec by the light source 50 is, for example, the light receiving optical system 500 b of the lens 53, the beam splitter 58, a condensing lens 59 has a position detecting element 60, as a light receiving optical axis The optical axis L2 is formed.

  The illumination light projected from the light source 50 and reflected by the cornea Ec forms an index image V (see FIG. 4) that is a virtual image of the light source 50. The light of the index image V passes through the lens 53 and the beam splitter 55, is reflected by the beam splitter 58, passes through the condensing lens 59, and enters the one-dimensional or two-dimensional position detection element 60 such as a PSD or a line sensor. Incident. When the eye E (cornea Ec) moves in the working distance direction (Z direction), the position detection element 60 moves the index image from the light source 50 on the position detection element 60. The working distance information is obtained based on the output signal. The output signal from the position detection element 60 of 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 detecting optical system is not as large in magnification as the light receiving optical system 70b described later. Therefore, the distance detection range in the Z direction of the position detection element 60 is wider than that of the light receiving element 77. The distance detection range of the position detection element 60 is, for example, a range of ± 3 to 4 mm from the alignment reference position.

  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 for measuring the corneal thickness of the eye E of the subject. The light projecting optical system 70a is also used as a part of the corneal deformation detection optical system and the first working distance detection optical system. Each optical system 70a, 70b, 48 is arranged in the measurement unit 104 similarly to the optical systems 500a to 600b, and is three-dimensionally moved by the XYZ driving unit 106.

  The light projecting optical system 70a has an optical axis L2 as a light projecting optical axis, and irradiates illumination light (measurement light) toward the cornea Ec of the eye E from an oblique direction. The light projecting optical system 70a includes, for example, an illumination light source 71, a condensing lens 72, a light limiting member 73, a concave lens 74, and a lens 53 that is also used as a corneal deformation detection optical system. As the illumination light source 71, a visible light source or an infrared light source (including near infrared) is used. For example, a light source such as an LED or a laser is used. The condensing lens 72 condenses the light emitted from the light source 71. In addition, the light source 50 and the light source 71 mutually use a wavelength band.

  The light restricting member 73 is disposed in the optical path of the light projecting optical system 70 a and restricts the light emitted from the light source 71. The light limiting member 73 is disposed at a position substantially conjugate with the cornea Ec. As the light limiting member 73, for example, a pinhole plate, a slit plate, or the like is used. The light limiting member 73 is used as an aperture that allows some light emitted from the light source 71 to pass therethrough and blocks other light. Then, the light projecting optical system 70a forms a predetermined pattern light beam (for example, a spot light beam, a slit light beam) on the cornea of the eye E.

  The light receiving optical system 70b has a light receiving element 77 and receives reflected light of illumination light on the cornea surface and the back surface of the eye E. The light receiving optical system 70b is disposed substantially symmetrically with the light projecting optical system 70a with respect to the optical axis L1. The light receiving optical system 70b includes, 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 in FIG. 3 also serves as a second working distance detection optical system that detects the alignment state of the eye E in the Z direction.

  The light receiving element 77 has a plurality of photoelectric conversion elements and receives reflected light from the front and back surfaces of the cornea. For the light receiving element 77, for example, a light detection device such as a one-dimensional line sensor or a two-dimensional area sensor is used. The light receiving optical system 70b of the corneal thickness measurement optical system and the second working distance detection optical system performs observation with an increased magnification. Therefore, the distance detection range in the Z direction of the light receiving element 77 is narrower than that of the position detecting element 60. For example, the range is ± 1 mm from the alignment reference position. The output of the light receiving element 77 is connected to the control circuit 20.

  When the eye E (cornea Ec) moves in the working distance direction (Z direction), the reflected light of the light source 71 from the cornea Ec also moves on the light receiving element 77, so that the control circuit 20 includes the second working distance detection optical system. Working distance information is obtained based on the output signal from the light receiving element 77. The control circuit 20 knows the corneal deformation state and the blink of the eye E based on the output signal from the light receiving element 77 and controls the driving of the solenoid 3.

  Regarding the positional relationship between the optical systems 70a, 70b, 48, for example, the optical axis L2 of the light projecting optical system 70a and the optical axis L3 of the light receiving optical system 70b are substantially symmetrical positions (for example, the optical axis L1 of the fixation optical system 48). , Left-right symmetry, up-down symmetry, etc.).

  The light emitted from the illumination light source 71 is collected by the condenser lens 72 and illuminates the light limiting member 73 from behind. The light from the light source 71 is limited by the light limiting member 73 and then imaged (condensed) near the cornea Ec by the lens 53. Near the cornea Ec, for example, a pinhole image (when using a pinhole plate) and a slit image (when using a slit plate) are formed. At this time, the light from the light source 71 is imaged in the vicinity of the intersection with the visual axis on the cornea Ec.

  When illumination light is projected onto the cornea Ec by the light projecting optical system 70a, the reflected light of the illumination light on the cornea Ec travels in a direction symmetrical to the projected light beam with respect to the optical axis L1. The reflected light is imaged on the light receiving surface on the light receiving element 77 by the light receiving lens 75.

  Regarding the output of the light receiving element 77, the surface of the cornea Ec (the received light signal S1 of reflected light on the surface (epithelium) of the cornea Ec illustrated in FIG. 5 and the received light signal S2 of reflected light on the back surface (endothelium) of the cornea Ec) Reflected light on the epithelium and the back surface (endothelium) is detected with strong luminance. As shown in FIG. 6, the reflected light on the front surface (see the solid line) and the reflected light on the back surface (see the broken line) are imaged at different positions on the light receiving element 77 because the reflected light paths are different.

  As described above, in the present embodiment, the projection optical axes of the corneal deformation detection optical system and the first working distance detection optical match the light receiving optical axes of the corneal thickness detection optical system and the second working distance detection optical system. The light receiving optical axes of the corneal shape detection optical system and the first working distance detection optical are arranged so that the light projecting optical axes of the corneal thickness detection optical system and the second working distance detection optical system coincide with each other. That is, the light projecting optical system 500a and the light receiving optical system 70b share the optical axis L3, and the light projecting optical system 70a, the light receiving optical system 500b, and the light receiving optical system 600b share the optical axis L2.

  At this time, the emitted light (illumination light) from the light source 50 is reflected by the beam splitter 52, travels on the axis L3, and enters the cornea Ec, and is reflected at an angle so that the incident angle to the cornea Ec is equal to the reflection angle. And proceed on the axis L2. Therefore, the light emitted from the light source 50 is not detected by the light receiving element 77. Similarly, the light emitted from the light source 71 passes through the beam splitters 58 and 55, travels on the axis L2, and enters the cornea Ec, and is reflected at an angle that makes the incident angle to the cornea Ec and the reflection angle equal. , Proceed on axis L3. Accordingly, the light emitted from the light source 71 is not detected by the photodetector 57 and the position detection element 60.

  Thereby, it is possible to prevent the light reception signal when the light detector 57 and the position detection element 60 detect the light reflected from the cornea Ec by the light source 50 from being influenced by the light reflected from the cornea Ec by the light source 71. . Similarly, the light reception signals S1 and S2 when the light receiving element 77 detects the light reflected from the cornea Ec by the light source 71 can be prevented from being influenced by the light reflected from the cornea Ec by the light source 50.

  The lens 53 that is also used in the light receiving optical systems 500b and 600b and the light projecting optical system 70a condenses the reflected light from the cornea Ec by the light source 50 in the center of the hole of the pinhole plate 56, and the light source 71. Is arranged at a position for condensing the illumination light from the front and back surfaces of the cornea Ec.

  The operation of the apparatus having the above configuration will be described. The examiner places the eye E to be examined at a predetermined position, and causes the subject to gaze at the fixation target. The examiner performs alignment adjustment by operating the joystick 105 based on the alignment information displayed on the monitor 36. The alignment adjustment in the vertical and horizontal directions is performed so that the corneal bright spot formed by the light source 40 has a predetermined relationship with a reticle (not shown) displayed on the monitor 36. Note that the vertical and horizontal alignments may be adjusted by automatic alignment. In this case, the control circuit 20 determines that the corneal bright spot by the light source 40 is formed at the alignment position set on the CCD camera 35 (for example, the intersection position of the optical axis L1 and the imaging surface of the CCD camera 35). The drive unit 106 is controlled. In this way, the control circuit 20 moves the measurement unit 104 to the alignment completion position in the XY direction.

  When the alignment adjustment in the XY directions is completed, the alignment adjustment in the Z direction is performed. For alignment adjustment in the Z direction, the control circuit 20 controls the drive unit 106 based on the working distance information obtained from the position detection element 60 and the light receiving element 77, and moves the measurement unit 104 toward the predetermined alignment completion position in the Z direction. (Automatic alignment).

  Before the automatic alignment is started, the examiner performs alignment in the Z direction. First, a joystick is used so that the light of the index image on the cornea Ec by the light emitted from the light source 50 is incident on the position detection element 60. The measurement unit 104 is moved in the Z direction by the operation 105.

  When the light of the index image is detected by the position detection element 60, the control circuit 20 detects the reflected light of the light source 71 at the cornea Ec by the light receiving element 77 based on the working distance information obtained from the position detection element 60. The measuring unit 104 is moved in the Z direction within a range. When the movement is completed, the control circuit 20 moves the measurement unit 104 in the Z direction based on the light reception signal by the reflected light from the cornea Ec of the light emitted from the light source 71 detected by the light receiving element 77.

  FIG. 7 is a diagram illustrating a state in which light emitted from the light source 71 is reflected by the cornea Ec. FIG. 8 shows a part of the first received light signal S1 corresponding to reflection on the surface of the cornea Ec and the second received light signal S2 corresponding to reflection on the back surface of the cornea Ec in the received light signal output from the light receiving element 77. FIG. As shown in FIG. 7A, the control circuit 20 performs alignment by driving the measurement unit 104 to a position where the emitted light of the light source 71 condensed by the lens 53 is substantially condensed on the back surface of the cornea Ec.

  For example, the control circuit 20 sets a threshold value a for extracting the second received light signal S2, and, as shown in FIG. 8A, the second received light signal S2 extracted at a portion exceeding the set threshold value a. Detect the peak position. The control circuit 20 controls the drive unit 106 so that the peak of the second light reception signal S2 is formed at the alignment completion position Ps (for example, the center position) set on the light receiving element 77. The threshold value a is preferably smaller than the peak value of the first light reception signal S1 and the peak value of the second light reception signal S2, and larger than the minimum value between the first light reception signal S1 and the second light reception signal S2. This is because the first light reception signal S1 and the second light reception signal S2 are separated and extracted, and the magnitude of the threshold value a is obtained experimentally, for example.

  When the alignment for measuring the corneal thickness is completed, the control circuit 20 automatically issues a trigger signal for starting the measurement (or by inputting a trigger signal by the examiner) and starts measuring the corneal thickness.

  As shown in FIG. 7B, when alignment is performed at a position where the emitted light from the light source 71 is collected on the surface of the cornea Ec, as shown in FIG. The second light receiving signal S2 corresponding to the reflection on the back surface of the cornea Ec is detected smaller than the first light receiving signal S1 corresponding to the reflection. As will be described later, since the control circuit 20 measures the corneal thickness based on the distance between the first light receiving signal S1 and the second light receiving signal S2 (or the distance between peaks of each signal), the signal of the second light receiving signal S2 is The measurement accuracy decreases due to the small size. Therefore, in the present embodiment, when measuring the corneal thickness, alignment is performed at a position where the light emitted from the light source 71 is substantially condensed on the back surface of the cornea Ec so that the second light receiving signal S2 can be detected largely.

  When a trigger signal for starting measurement is generated, the control circuit 20 calculates a distance (interval) between the extracted first light reception signal S1 and the second light reception signal S2. Each received light signal is extracted, for example, by edge detection processing for the luminance distribution. The control circuit 20 may calculate the distance between the two peaks based on the output of the light receiving element 77 and calculate the corneal thickness from the calculated distance.

  Thereafter, the control circuit 20 converts the calculated distance into a measured value of the corneal thickness of the eye E using at least one of the arithmetic expression and the table. The obtained measurement value is stored in the memory 24. In the case of an arithmetic expression, for example, the arithmetic expression is created by optical simulation or the like in consideration of a difference in refractive index between air and the cornea, a difference in corneal curvature, and the like. In the case of a table, for example, the table is created by calibration using known eyes (for example, model eyes) having different thicknesses. An arithmetic expression, a table, and the like are stored in the memory 24 in advance.

  The control circuit 20 calculates the corneal thickness a plurality of times (for example, about 10 times) by acquiring the light reception signal from the light receiving element 77 a plurality of times, and stores the average value in the memory 24 as a measured value of the corneal thickness. It may be.

  When the corneal thickness measurement is completed, the control circuit 20 shifts to alignment in the Z direction for measuring intraocular pressure. As shown in FIG. 7B, the control circuit 20 performs alignment by driving the measurement unit 104 to a position where the emitted light of the light source 71 condensed by the lens 53 is substantially condensed on the surface of the cornea Ec.

  For example, the control circuit 20 switches the setting from the threshold value a to the threshold value b (the threshold value b for extracting the second light reception signal S2). As shown in FIG. 8B, the control circuit 20 detects the peak position of the first light reception signal S1 extracted at a portion exceeding the set threshold value b. The control circuit 20 performs alignment in the Z direction so that the peak of the first light reception signal S1 is formed at the alignment completion position Ps set on the light receiving element 77. The threshold value b is preferably smaller than the peak value of the first light reception signal S1 and larger than the peak value of the second light reception signal S2. This is for extracting the first light receiving signal S1, and the magnitude of the numerical value b may be obtained experimentally. At the time of measuring the intraocular pressure, since the second light reception signal S2 by the reflected light from the back surface of the cornea Ec is not used for the measurement, it is preferable to perform alignment based on the first light reception signal that is detected relatively strongly.

  When performing alignment in the Z direction for measuring intraocular pressure from the alignment state for measuring corneal thickness, the measuring unit 104 is driven in a direction away from the eye E. At this time, the control circuit 20 controls the driving unit 106 to move it in the direction away from the eye E from the corneal thickness measurement position by the measured value of the corneal thickness previously measured. Thereby, the condensing position of the light from the light source 71 reaches the vicinity of the corneal surface. Thereafter, the control circuit 20 moves the measurement unit 104 in the Z direction based on the first light reception signal S1 as described above. Such control shortens the alignment adjustment time.

  The control circuit 20 starts supplying current to the solenoid 3 before the alignment is completed, and drives and controls the solenoid 3 so that fluid is sprayed onto the eye cornea after the light receiving element 77 completes the alignment operation in the Z direction. To do. The control circuit 20 applies electric charge as operable drive energy to the rotary solenoid 3 via the drive circuit 23 to drive it.

  When electric charge is applied to the rotary solenoid 3, the piston 2 rises, the air in the air compression chamber 11 is compressed by the piston 2, and the compressed air is blown toward the cornea of the eye E from the nozzle 6. The cornea of the eye E is gradually deformed by the compressed air blown. Reflected light from the cornea of the light projected from the light source 50 enters the photodetector 57, and the deformed state of the cornea is detected by an output signal from the photodetector 57.

  Here, the eye cornea to be examined is gradually deformed by blowing compressed air, and the maximum amount of light enters the photodetector 57 when it reaches the applanation state. Then, the control circuit 20 obtains an intraocular pressure value based on an output signal from the pressure sensor 12 when the eye cornea to be examined reaches an applanation state.

  Here, the control circuit 20 corrects the intraocular pressure measurement value of the eye to be examined based on the corneal thickness measured by the corneal thickness measurement optical system. In this case, the measured value of corneal thickness is applied to the empirical regression equation that shows the correlation between the corneal thickness, the amount of measurement error from true intraocular pressure, and the intraocular pressure The intraocular pressure value can be corrected by correcting the measurement value.

  Thereafter, the control circuit 20 displays the corrected intraocular pressure value and corneal thickness measurement value on the display monitor 36. When a predetermined number (for example, three) of measurement values excluding the measurement error is obtained, the intraocular pressure measurement is terminated.

  Thus, in the case of a non-contact tonometer having the configuration of the present embodiment, by switching the alignment reference in the Z direction, which has been constant in the past, between corneal thickness measurement and intraocular pressure measurement, The corneal thickness can be accurately measured while maintaining the measurement accuracy.

  In addition, in the alignment for measuring the corneal thickness and the alignment for measuring the intraocular pressure, the extraction process and the peak detection process of the first light reception signal S1 and the second light reception signal S2 can be simplified by switching between the two threshold values.

  In the above description, the output signal from the position detection element 60 of the first working distance detection optical system is used for coarse adjustment of the alignment in the Z direction. However, the present invention is not limited to this. At the time of measuring intraocular pressure, the final adjustment (fine adjustment) of the alignment in the Z direction may be performed by an output signal from the position detection element 60. In the intraocular pressure measurement method of the present embodiment, it is preferable to spray a fluid on the eye E at the same time as alignment is achieved. This is because the eye E may move due to the reflexive avoidance behavior of the subject due to the spray of fluid. In such a case, it is preferable to perform final adjustment (fine adjustment) of the alignment with an output signal from an element having a high response speed. At the time of cornea measurement, since a reflection signal on the back surface of the cornea is used, alignment is performed based on the output from the light receiving element 77.

  In the above description, although two threshold values are provided for the extraction processing of the light reception signals S1 and S2, a method of performing processing by providing one threshold value is also conceivable. For example, when the first light receiving signal S1 and the second light receiving signal S2 are extracted as in the threshold value a, the alignment at the time of measuring the corneal thickness is detected on the left side of the light receiving element 77 among the two extracted signals. Alignment is performed so that the peak of the light receiving signal is arranged at a predetermined position of the light receiving element 77. For alignment at the time of measuring intraocular pressure, alignment is performed so that the peak of the received light signal detected on the right side of the light receiving element 77 of the two extracted signals is arranged at a predetermined position of the light receiving element 77. As described above, when the alignment reference is switched between the corneal surface and the corneal back surface, the reflected light on the corneal surface is determined from the positional relationship between both signals detected by the light receiving element 77 with respect to the two received light signals S1 and S2 exceeding the threshold value. And the light reception signals S1 and S2 of the reflected light from the back of the cornea may be discriminated, and the alignment reference may be switched between the corneal thickness measurement and the intraocular pressure measurement.

  In addition, in order to prevent the signal of the reflected light from the cornea Ec by the light source 71 from being too large and saturating the detectable range of the light receiving element 77, the alignment reference is adjusted to the corneal surface and to the corneal back surface. The light amount of the light source 71 or the gain of the light receiving element 77 may be adjusted.

  In addition, when the signal of the reflected light from the cornea Ec by the light source 71 is large and the upper limit of the detectable range of the light receiving element 77 is saturated, the assumed peak position is calculated based on the received light signal detected within the detectable range. It is possible to perform alignment in the Z direction so that the calculated peak position matches the alignment completion position Ps. Therefore, as described above, the alignment in the Z direction is performed without switching the light amount of the light source 71 or the gain of the light receiving element 77 between the case where the alignment reference is aligned with the cornea surface and the case where the alignment reference is aligned with the cornea back surface. Is possible.

  Moreover, it is good also as a structure which switches the tolerance | permissible_range of the alignment adjustment of a Z direction between the time of corneal thickness measurement and the time of intraocular pressure measurement.

  The present invention is not limited to the non-contact tonometer, and can be used in an apparatus that measures corneal thickness and other eye characteristics other than corneal thickness.

  Further, in the configuration of the present embodiment, the projection optical axes of the corneal deformation detection optical system and the first working distance detection optical are the same as the light receiving optical axes of the corneal thickness detection optical system and the second working distance detection optical system, The light receiving optical axes of the corneal shape detection optical system and the first working distance detection optical are arranged so that the light projecting optical axes of the corneal thickness detection optical system and the second working distance detection optical system coincide with each other. By having such a configuration, it becomes possible to perform corneal thickness measurement and intraocular pressure measurement with the light sources 50 and 71 turned on simultaneously, and it is necessary to repeatedly turn on and off the light sources 50 and 71 for each measurement. Disappears. Further, by providing the above configuration, the light receiving element 77 can detect the reflected light from the light source 71 at the cornea Ec when the cornea Ec is deformed by the air from the nozzle 6 along with the intraocular pressure measurement. The light reception signal output from the light receiving element 77 at the time of corneal deformation obtained in this way can be used for correction of an intraocular pressure value. For example, the hardness of the eye, elasticity, and the like can be obtained from the amount of deformation of the corneal thickness caused by air injection, and used to correct the intraocular pressure value.

  In the above description, the alignment reference to the cornea surface and the alignment reference to the cornea back surface are not limited to strictly aligning the alignment reference to the cornea surface and the cornea back surface. Even if the alignment reference is adjusted to the vicinity of the cornea surface and the vicinity of the cornea back surface, a certain effect can be obtained. The alignment reference may be shifted to either the left or right (front and back of the corneal surface, the back and front of the corneal surface) of each of the received light signals S1 and S2.

  For example, when measuring the corneal thickness, even if the alignment reference is shifted to the corneal back side by a predetermined distance from the first reception signal S1 corresponding to the corneal surface, the second reception signal S2 is more than when the alignment reference is aligned with the corneal surface. Can be detected strongly.

  For example, even when the alignment reference is set to the intermediate position between the peak value of the first received light signal S1 and the peak value of the second received light signal S2 when measuring the corneal thickness, the alignment is made to the peak value of the first received light signal S1 when measuring the corneal thickness. The corneal thickness can be measured with higher accuracy than those that meet the standards.

  In the above configuration, the present invention can also be applied to a non-contact ultrasonic tonometer that measures the intraocular pressure of the eye to be examined with ultrasonic waves. The non-contact ultrasonic tonometer includes, for example, a transmission unit that irradiates the eye cornea with ultrasonic waves, and a first detector for detecting reflected signals from the cornea surface of the eye with ultrasonic waves. Based on the signal from one detector, the intraocular pressure of the eye to be examined is measured in a non-contact manner using ultrasound.

It is the schematic which shows the external appearance of the apparatus concerning this embodiment. It is the figure which showed the side outline of the fluid ejection mechanism with which the apparatus which concerns on this embodiment has, and the principal part of the control system. It is an upper view optical system principal part figure of the apparatus concerning this embodiment. It is the schematic which shows the parameter | index image by the illumination light reflected by the cornea. It is the schematic which shows an example of the light reception signal of the reflected light by the cornea surface received by the light receiving element, and the reflected light by a cornea back surface. It is the schematic which shows the optical path of the path | route of the reflected light in the cornea surface, and the reflected light in a cornea back surface. It is the figure which showed a mode that the light emitted from the light source reflected in a cornea It is a figure which shows a part of light reception signal corresponding to reflection on the cornea surface, and light reception signal corresponding to reflection on the cornea back surface in the light reception signal output from a light receiving element.

DESCRIPTION OF SYMBOLS 1 Cylinder part 2 Piston 3 Solenoid 6 Nozzle 7a, 7b Glass plate 20 Control circuit 36 Monitor 50 Infrared light source 52 Beam splitter 53 Lens 57 Photo detector 60 Light receiving element 71 Illumination light source 77 Light receiving element 100 Non-contact type tonometer 101 Base 103 Moving table 104 Measuring unit 105 Joystick 106 XYZ driving unit

Claims (3)

An intraocular pressure measuring means having a first detector for detecting a reflection signal from the corneal surface of the subject's eye, and measuring the intraocular pressure of the subject's eye in a non-contact manner, a reflected signal from the corneal surface and the back of the cornea A corneal thickness measuring means for measuring the corneal thickness of the subject's eye in a non-contact manner, and an observation optical system for observing the anterior segment of the subject's eye A measuring unit comprising: an observation optical system shared in vertical alignment in the intraocular pressure measuring means and the corneal thickness measuring means;
A moving mechanism that has an electric motor and moves the measuring unit relative to the eye to be examined;
A third detector for detecting a reflected signal from the cornea of the eye to be examined provided in the measurement unit, comprising an alignment detection means for detecting an alignment state in the front-rear direction of the measurement unit with respect to the eye cornea;
The alignment detection means switches the alignment reference position on the cornea set to detect the alignment state between tonometry and corneal thickness measurement, and detects the alignment state with respect to the switched alignment reference position. A non-contact tonometer.   In the intraocular pressure measurement, the alignment detection means sets the alignment reference position as the first alignment reference position on the corneal surface, and in the corneal thickness measurement, the alignment reference position is used as the second alignment reference position or near the corneal back surface The non-contact tonometer according to claim 1, wherein 3. The non-contact type eye according to claim 1, further comprising a control unit that moves the measurement unit toward the alignment reference position by controlling the electric motor based on a detection result of the alignment detection unit. Pressure gauge.

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