JP3577071B2 - Non-contact tonometer - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a non-contact tonometer capable of measuring an intraocular pressure of a subject's eye with high accuracy by optically detecting a deformed state of a cornea of the subject's eye when airflow is blown.
[0002]
[Prior art]
Conventionally, a non-contact tonometer has airflow blowing means for deforming the cornea by blowing airflow onto the cornea of the eye to be inspected, and projecting a light flux on the cornea to measure a change in the amount of reflected light flux accompanying the corneal deformation. A corneal deformation detecting optical system that detects corneal deformation by detecting the corneal deformation is known.
[0003]
In this conventional non-contact tonometer, when a rotary solenoid which constitutes a part of the airflow blowing means is operated to drive the piston, an airflow is emitted from the nozzle of the airflow blowing means toward the cornea. At this time, the cornea is deformed as shown in FIG. 1 according to the change in the pressure of the airflow.
[0004]
By the way, as shown in FIG. 1, the cornea C is hardly deformed immediately after the start of the discharge of the airflow (see the period t1). However, the cornea C is deformed as shown by a solid line when the discharge pressure of the airflow increases after a predetermined time has elapsed from the start of the discharge of the airflow (see period t2). '(See time t0).
[0005]
Then, when the discharge pressure of the airflow further increases, the cornea C is dented as shown by periods t3 and t4. At this time, the light amount of the reflected light flux from the cornea C increases as the cornea C deforms toward flattening, reaches a theoretical maximum in the flattened state, and decreases as the cornea C deforms from the flattened state to concave. . Therefore, in such a deformation of the cornea, a light amount change curve as indicated by a symbol D is drawn.
[0006]
On the other hand, the pressure of the airflow is displayed as a pressure change curve P over time as shown in FIG. Since there is a correlation between the pressure value in the airflow blowing means and the intraocular pressure value of the subject's eye when the cornea C is in the flat state, the pressure change curve P when the light quantity change curve D shows the peak value D ' And the intraocular pressure value IOP can be calculated from the pressure value P0 using an arithmetic circuit.
[0007]
[Problems to be solved by the invention]
However, it may be difficult to specify the time point at which the cornea enters the flattened state based on the light amount change curve D due to various external factors. For example, as shown in FIG. 4, fine disturbance may occur in the light amount change local line due to tears, eyelashes, and the like. In this case, the peak position cannot be specified, and the time at which the cornea enters the flat state cannot be specified accurately. Also, as shown in FIG. 3, the light amount may increase or decrease gradually due to the difference in the magnitude of the elasticity of the cornea. Also in this case, it is difficult to specify the peak position. Therefore, in the conventional non-contact tonometer, the positions of the reflected light amount corresponding points having the same reflected light amount level on the light amount increasing side and the light amount increasing side of the light amount change curve are obtained, and the position between the reflected light amount corresponding points is determined. By integrating the reflected light amount levels of the light amount change curve, a reflected light amount corresponding centroid point Z for measuring an intraocular pressure value is calculated, and the reflected light amount corresponding centroid point Z is measured as a true peak position to measure an intraocular pressure value IOP. Known to do so. (For example, see Patent Document 1)
However, such a method of calculating the center of gravity is a method of calculating the flattening time of the cornea, which is suitable for the pattern of the light amount change curve having a relatively high appearance ratio. Therefore, when a special pattern with a relatively low appearance rate, for example, a pattern with extremely high intraocular pressure, appears, the time at which the cornea becomes flat may be incorrectly calculated, and the obtained intraocular pressure value may be calculated. Had a problem of lack of reliability.
[0008]
That is, when the intraocular pressure becomes high, more airflow must be blown until the cornea is blown by the airflow and flattened until the cornea becomes further dented. Therefore, in the method of calculating the center of gravity as disclosed in Japanese Patent Application Laid-Open No. 5-56930, there is a problem that the higher the intraocular pressure, the higher the value of the true intraocular pressure is displayed.
[0009]
FIG. 6 shows a light amount change curve D of the hypertensive eye. When the eye is not a hypertensive eye, X′Y ″ is obtained from a curve indicated by a broken line. In the case of a high intraocular pressure, a solid line is obtained. Since the calculation is performed, it is displayed higher than the true intraocular pressure, which is not preferable.
[0010]
Conventionally, in a non-contact tonometer, an example has been known in which an obtained light amount change curve D is output by a printer or the like to help determine the reliability of the obtained intraocular pressure value.
[0011]
However, simply displaying the curve does not make it clear which point of the curve was determined to be the time of cornea flattening and the intraocular pressure value was calculated. Therefore, when a special pattern is obtained, it is not known whether the obtained intraocular pressure value is an accurate value, and there is a problem that reliability is lacking.
[0012]
Therefore, an object of the present invention is to solve these problems and improve the reliability of the calculated intraocular pressure value.
[Patent Document 1]
JP-A-5-56930 (see FIG. 5)
[0013]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 includes a projection unit that projects a measurement light beam onto the cornea of the eye to be inspected, a light receiving sensor that receives reflected light of the measurement light beam from the cornea of the eye to be inspected, A corneal deformation detection optical system that guides the reflected light from the eye cornea to the light receiving sensor, an airflow blowing unit that blows an air pulse to the eye cornea to deform the cornea, and the airflow blowing unit. Calculating means for calculating an intraocular pressure by calculating a predetermined deformation point of the cornea to be examined based on a light quantity change curve which is an output change of the light receiving sensor when the cornea to be examined is deformed, the calculating means comprising: The reflected light amount corresponding centroid point is obtained by integrating the light amount of a portion equal to or higher than a predetermined light amount detection level in the light amount change curve, and the reflected light amount corresponding centroid point is calculated from the pressure of the air pulse corresponding to the obtained reflected light amount corresponding centroid point. Together determine the intraocular pressure value of the cornea, when said intraocular pressure value of the cornea exceeds a predetermined value, calculating the point at which maximum light amount of the light amount change curve is obtained as a predetermined deformation point of the cornea A non-contact tonometer.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the invention of the ophthalmic instrument according to the present invention is applied to a non-contact tonometer, and will be described with reference to the drawings.
[0015]
7A and 8, reference numeral 10 denotes a fixation target projection optical system that projects a fixation target at the eye E, and reference numeral 20 denotes an anterior eye image including the eye E and an optical axis. An anterior eye observation optical system capable of detecting alignment (alignment detection) between O and the visual axis O ′ of the eye E; an alignment light projecting optical system 30 for projecting an alignment light beam onto the eye E; Reference numeral 50 denotes a corneal deformation detection optical system that optically detects the deformation of the cornea C.
[0016]
The fixation target projection optical system 10 includes an LED 11 that emits visible light, a pinhole 12, a wavelength division filter 13 having a property of transmitting visible light and reflecting near-infrared light, a collimator lens 14, a half mirror 15, a chamber. It has a window glass 16 and an injection nozzle 17 (airflow blowing means) for blowing airflow. The chamber window glass 16 is a frame surrounding a supply device such as a cylinder member for supplying an air pulse to the injection nozzle 17. The cylinder member has a piston driven by a rotary solenoid (not shown). When the piston is operated by the rotary solenoid, compressed air is supplied to the injection nozzle 17. Since this structure employs a well-known structure, a specific illustration is omitted.
[0017]
The visible light emitted from the LED 11 to be a gazing target passes through the pinhole 12, passes through the wavelength division filter 13, is converted into a parallel light beam by the collimator lens 14, is reflected by the half mirror 15, and is then reflected by the chamber window glass 16. And an image is presented to the cornea C of the eye E through the inside of the ejection nozzle 17.
[0018]
The anterior ocular segment observation optical system 20 includes a plurality of LEDs 21 for emitting infrared light for directly illuminating the eye E to be inspected from the left and right for anterior ocular segment observation, a cover glass 22 fixed to the tip of the ejection nozzle 17, and an ejection nozzle 17. , A chamber window glass 16, a half mirror 15, an objective lens 24, a half mirror 25, an imaging lens 26, and a CCD camera 27 that support one end of the camera.
[0019]
The infrared reflected light from the LED 21 reflected by the subject's eye E passes through the glasses 22 and 23, the chamber window glass 16 and the half mirror 15, is converted into a parallel light beam by the objective lens 24, and passes through the half mirror 25. The light is condensed by the imaging lens 26 and is imaged on the CCD camera 27.
[0020]
The infrared reflected light flux formed on the CCD camera 27 is input to the image processing circuit G and converted into a signal, and as shown in FIG. 7B, the front eye is displayed on the screen 28 of the monitor television M (image display means). The partial image E 'is displayed. In addition, the screen 28 electrically displays the alignment area 28a.
[0021]
The alignment light projection optical system 30 includes an LED 31 used for alignment operation and for detecting intraocular pressure, condenser lenses 32 and 33, an aperture stop 34, a pinhole 35 for forming an image projected on the cornea C, and a wavelength. It has a split filter 13, a collimator lens 14, a half mirror 15, a chamber window glass 16, and an injection nozzle 17. The pinhole 35 is provided at the rear focal position of the collimator lens 14.
[0022]
The near-infrared light emitted from the LED 31 passes through the condenser lenses 32 and 33, the aperture stop 34, and the pinhole 35, is reflected by the wavelength division filter 13, is converted into a parallel light beam by the collimator lens 14, and is reflected by the half mirror 15. After that, the light passes through the chamber window glass 16, passes through the inside of the ejection nozzle 17, is projected onto the cornea C of the eye E, and is reflected by the cornea C.
[0023]
The corneal reflected light reflected by the cornea C passes through the glasses 22, 23, 16 and the half mirror 15 by the anterior ocular segment observation optical system 20 and is converted into a parallel light by the objective lens 24. After passing through the mirror 25, the light is condensed by the imaging lens 26, formed into an image on the CCD camera 27, and an optotype image 28 b is displayed on the screen 28.
[0024]
The examiner moves the apparatus body three-dimensionally so that the optotype image 28b enters the alignment area 28a. When the alignment is out of alignment, the optotype image 28b moves in the vertical and horizontal directions in the screen 28. When the working distance is out of alignment, the optotype image 28b becomes large and protrudes from the alignment area 28a. This allows the examiner to perform alignment and rough working distance adjustment.
[0025]
The alignment light imaging optical system 40 shares optical components from the cover glass 22 to the half mirror 25, and has an imaging lens 41, a reflection mirror 42, a half mirror 43, diaphragms 44 and 45, and light receiving sensors 46 and 47. .
[0026]
A part of the alignment reflected light beam reflected by the cornea C is reflected by the half mirror 25 and guided to the imaging lens 41, and is reflected by the reflection mirror 42 while being condensed by the imaging lens 41 and is reflected by the half mirror 43. Some are transmitted and others are reflected. The alignment reflected light beam transmitted through the half mirror 43 passes through the stop 44 and forms an image on the light receiving sensor 46. The alignment reflected light beam reflected by the half mirror 43 is imaged on the light receiving sensor 47 via the stop 45.
[0027]
The light receiving sensors 46 and 47 are disposed before and after the light condensing position P where the alignment reflected light flux forms an image when the cornea C is at an appropriate working distance. In the present embodiment, the diaphragms 44 and 45 and the light receiving sensors 46 and 47 are designed so that the same one can be used. In addition, the light receiving sensors 46 and 47 cause the arithmetic and control circuit (calculating means) 60 including the central processing unit shown in FIG. 16 to calculate the working distance based on the light amount ratio of the alignment reflected light flux incident on each of them.
[0028]
For example, when the light amount incident on the light receiving sensor 46 is α level and the light amount incident on the light receiving sensor 47 is β level,
γ = (β-α) / (β + α)
, The working distance can be calculated by calculating the light amount ratio γ. When α = β and γ = 0, it is determined that the working distance is appropriate. Further, when γ> 0, the eye E and the apparatus main body are close to each other, and when γ <0, the eye E and the apparatus main body are far from each other. In this case, since the detection is performed based on the light amount ratio γ, the working distance can be detected without being affected by the reflectance of the cornea C.
[0029]
On the other hand, a working distance recognition bar 28c is combined and displayed on the screen 28 based on the light receiving state of the light receiving sensors 46 and 47, and the examiner can recognize the working distance by changing the length of the working distance recognition bar 28c. .
[0030]
For example, the working distance area 28d is synthesized and displayed on the screen 28 in the same manner as the alignment area 28a, and the width of the working distance area 28d is set as the proper working distance. When the working distance area is within the proper working distance, the working distance recognition bar 28c is displayed as the working distance area. When the distance is outside the proper working distance, the working distance recognition bar 28c protrudes from the working distance area 28d according to the distance. Further, when the apparatus main body is too close to the eye E, a warning display such as "TOO CLOSE" is displayed on the screen 28 to make the examiner recognize.
[0031]
On the other hand, the alignment detection by the light receiving sensors 46 and 47 confirms that the light amounts of the respective sensors 46 and 47 are both equal to or higher than a predetermined light amount level. In this case, since the change in the amount of light due to the movement of the image due to the alignment on the diaphragms 44 and 45 is considerably larger than the effect of the change in the reflectance of the cornea C, the influence of the reflectivity of the cornea C can be small, and the measurement accuracy is low. Has no effect. Further, when the alignment image forming optical system 40 is telecentric on the image side, the movement of the image by the alignment on the diaphragms 44 and 45 becomes the same, so that the alignment can be detected more accurately.
[0032]
The corneal deformation detection optical system 50 includes optical components from the cover glass 22 to the half mirror 25, a reflection mirror 51, an aperture 52, and a light receiving sensor 53.
[0033]
When the completion of the alignment and the working distance is detected by the light receiving sensors 46 and 47, an ejection OK signal is output to an air ejection driving device (not shown). 2), the cornea C is deformed by the air injected through the injection nozzle 17. At the same time, the detection light is emitted from the LED 31 toward the cornea C.
[0034]
As shown in FIG. 8, the detection light at this time is, as in the case of the alignment detection, the condenser lenses 32 and 33, the aperture stop 34, the pinhole 35, the wavelength division filter 13, the collimator lens 14, the half mirror 15, and the chamber window. The light is projected onto the cornea C of the eye E through the glass 16 and the ejection nozzle 17 and is reflected by the cornea C.
[0035]
Then, the detected reflected light reflected by the cornea C passes through the half mirror 25 from the ejection nozzle 17, is reflected by the half mirror 25, is reflected by the reflection mirror 51, passes through the diaphragm 52, and forms an image on the light receiving sensor 53. Is done.
[0036]
In the light receiving sensor 53, the amount of light received by the light receiving sensor 53 increases with the start of deformation of the cornea C. When the cornea C reaches a predetermined flat state, the maximum amount of light is received. Decrease, and the light amount change curve shown in FIG. 1 is obtained.
[0037]
The maximum light amount time point of the light amount change curve is a predetermined flat time, and the pressure of the air at that time or a physical quantity having a correlation with the pressure-for example, the time after the air starts to be injected from the injection nozzle 17-the intraocular pressure is determined according to a known procedure. Desired.
[0038]
When the intraocular pressure is obtained, the image processing circuit G displays the intraocular pressure value and its light amount change curve on the screen 28 on the image display means M as shown in FIG. The examiner determines whether or not the obtained intraocular pressure value is highly reliable by checking the light amount change curve. For example, if the peak a1 is a single light amount change curve D as shown in FIG. 9A, the reliability is high, and as shown in FIG. 9B, the light amount change curve D has a plurality of peaks a1, a2, a3, and the like. In this case, it can be determined that the reliability is low. In this case, the measurement is performed again.
[0039]
FIG. 10 shows an overall view of the apparatus, and the printer 101 is incorporated in a gantry of the apparatus. FIG. 11 shows a result of outputting the measurement result to the printer paper 101a by the printer 101, and the intraocular pressure value 102 and the light amount change curve D are displayed together with the patient ID on the printer paper 101a. However, even if the calculated intraocular pressure value is correct to display the light amount change curve D as described above, it may be determined that the reliability is low. Is desirably displayed together.
[0040]
FIG. 12 shows a pressure change curve 71 together with a light quantity change curve D on the screen 28, and furthermore, a point where the cornea is calculated to be in a predetermined flat state is indicated by a dashed line 70 (hereinafter, this dashed line is a position at which an intraocular pressure value is obtained. This is an example in which the predetermined deformation point Dm is used as a mark for obtaining on the light quantity change curve D) in association with the light quantity change curve D.
[0041]
FIG. 13 illustrates a state where the broken line 70 in FIG. 12 is moved. This switch operation signal is input to the arithmetic and control circuit 60 when the examiner operates switches (cursor keys and the like in the horizontal direction) 103 and 104 on the panel 102 shown in FIG. At this time, the arithmetic control circuit 60 controls the movement of the broken line 70 as shown in FIG. 12 in the time axis direction (time t direction) according to the switch operation. At this time, the movement of the broken line 70 is performed in association with the pressure change curve and the light amount change curve stored by the arithmetic control circuit 60 (not shown). In addition, the arithmetic control circuit 60 sequentially recalculates the intraocular pressure value every time the broken line 70 moves in the time axis direction, and changes the intraocular pressure value displayed on the screen 28.
[0042]
Therefore, the examiner moves the broken line 70 to a position where the cornea of the light amount change curve D displayed on the screen 28 is in a predetermined flat state, so that a correct intraocular pressure value can be obtained.
[0043]
It is not necessary to display the pressure change curve D, but there is an advantage that an abnormality of the air pulse generator can be detected, and it is preferable to display the tonometer of a type in which the pressure of the air pulse generator is directly measured. .
[0044]
The operation for measuring the intraocular pressure is performed as described above, but the intraocular pressure values in the case of normal intraocular pressure and the case of high intraocular pressure can be obtained as follows.
[0045]
FIG. 14A shows a light amount change curve D when a human eye having a normal intraocular pressure (for example, 18 mmHg) is measured, and FIG. 14B shows a light amount change curve when a human eye with a high intraocular pressure (for example, 35 mmHg) is measured. In order to simplify the description of the light amount change curve D ′, the graph is shown on the same graph.
[0046]
In FIG. 14A, Dm is a point at which the maximum light quantity of the light quantity change curve is obtained, and IOP1 is calculated by a known technique (by the second calculation method) based on the pressure P1 of the corresponding air pulse. Is done. At the same time, the light amount detection level L of the light amount change curve between the reflected light amount corresponding points X and Y crossing the light amount detection level L of the light amount change curve D is integrated, and the position of the reflected light amount corresponding centroid point Z is calculated. Based on the corresponding air pulse pressure P2, IOP2 is calculated by a known technique (by a first calculation method).
[0047]
There is a possibility that the position of Dm may deviate from a predetermined flattening time of the cornea due to eyelashes, tears, eye movements, etc. of the subject's eye.
[0048]
Similarly, in the case of a high intraocular pressure (FIG. 14B), P3 is calculated from Dm, and IOP1 'is calculated by a known technique, and P4 is calculated from Z', and IOP2 'is calculated by a known technique. Here, when IOP2 '> 30 mmHg, the value of IOP1' is displayed on the screen 28 as an intraocular pressure value. This is because, in the case of high intraocular pressure, more air is needed when the cornea is further depressed from the flattened state than until the cornea becomes a predetermined flattened shape. This is because the value becomes considerably higher than the above. The position of Dm 'may deviate from the predetermined flattening time of the cornea depending on the condition of the eye to be examined, similarly to Dm. However, in the case of high intraocular pressure, an error of 1 to 2 mmHg does not cause a clinical problem.
[0049]
Whether to use IOP1 or IOP2 may be selected according to the switching of the measurement range changeover switch 105 (FIG. 10 (b)) of the apparatus, and the screen 28 corresponds to the graph of FIG. May be displayed, and the examiner may select one of H (high intraocular pressure) and L (low intraocular pressure) by using the switches 106 and 107 on the panel 102. In addition, in FIG. 10, J is a joystick lever.
[0050]
FIG. 15 shows a printout format of the measured intraocular pressure obtained in the second embodiment. In (A), IOP2 obtained from point Z indicated by a solid line at normal intraocular pressure is displayed as an intraocular pressure value, and IOP1 obtained from Dm indicated by a broken line 70 is displayed in parentheses. An arrow is added to the solid line to indicate that the measured value of IOP2 from point Z is 18 mmHg without parentheses. Similarly, (B) shows the measurement result of the hypertensive eye, and it can be seen that the IOP1 'obtained from Dm' shown by the broken line is the measured value without parentheses (33 mmHg).
[0051]
【The invention's effect】
As described above, the invention according to claim 1 includes a projection unit that projects a measurement light beam onto the cornea of the eye to be inspected, a light receiving sensor that receives reflected light of the measurement light beam from the cornea of the eye to be inspected, and A corneal deformation detection optical system that guides the reflected light from the optometry cornea to a light receiving sensor; airflow blowing means for blowing an air pulse onto the cornea to be examined to deform the cornea; and the airflow blowing means using the airflow blowing means. Calculating means for calculating an intraocular pressure by obtaining a predetermined deformation point of the cornea of the eye to be examined based on a light amount change curve which is an output change of the light receiving sensor when the optometric cornea is deformed, wherein the calculating means comprises: The reflected light amount corresponding centroid point is obtained by integrating the light amount of the portion above the predetermined light amount detection level in the change curve, and the eye to be inspected is obtained from the pressure of the air pulse corresponding to the obtained reflected light amount corresponding centroid point. Together determine the intraocular pressure of the membrane, when said intraocular pressure value of the cornea exceeds a predetermined value, calculates the point at which maximum light amount of the light amount change curve is obtained as a predetermined deformation point of the cornea With the configuration, the predetermined deformation point can be changed , and the calculation method for obtaining the predetermined flattening time of the cornea from the reflected light amount change curve can be changed according to the intraocular pressure value. I got it.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a case where a change in the amount of light of reflected light from a cornea of an eye to be examined at the time of airflow blowing is sharp.
FIG. 2 is an explanatory diagram showing a relationship between a change in the amount of reflected light from the cornea of the eye to be examined and a change in pressure when airflow is blown.
FIG. 3 is an explanatory diagram showing a case where a change in the amount of light of reflected light from the cornea of the eye to be examined during airflow blowing is gentle.
FIG. 4 is an explanatory diagram showing a case in which there are a plurality of peaks in a change in the amount of light of reflected light from the cornea of the eye when the airflow is blown.
FIG. 5 is an explanatory diagram showing a relationship for obtaining an intraocular pressure value from a change in the amount of reflected light from the cornea of the subject's eye and a change in pressure when airflow is blown.
FIG. 6 is an explanatory diagram showing a change in the amount of reflected light from the cornea of the eye with high intraocular pressure at the time of airflow blowing.
7A is an explanatory view showing an optical system of a non-contact tonometer according to the present invention, and FIG. 7B is a monitor screen showing an image of an anterior ocular segment of a subject's eye captured by the optical system of FIG. FIG. 7C is an explanatory view showing a change in the amount of reflected light from the cornea of the eye when the airflow is blown onto the cornea of the eye by the non-contact tonometer having the optical system of FIG.
8 is an operation explanatory view of the non-contact tonometer shown in FIG. 7;
FIGS. 9A and 9B are explanatory diagrams of a light amount change curve.
10A is an explanatory diagram of a non-contact tonometer provided with the optical system shown in FIG. 7, and FIG. 10B is an enlarged explanatory diagram of a main part of FIG.
FIG. 11 is an explanatory diagram showing a print example of a measurement result obtained by the non-contact tonometer shown in FIG. 7;
FIG. 12 is an explanatory diagram showing a display example on a monitor screen according to the present invention.
13 is an explanatory diagram when a mark (broken line) indicating a predetermined deformation point shown in FIG. 12 is moved.
FIG. 14 is an explanatory diagram showing a change in light amount between a person with normal intraocular pressure and a person with high intraocular pressure.
15A is an explanatory diagram illustrating an example of calculating an intraocular pressure value from a light intensity curve of a person with normal intraocular pressure, and FIG. 15B is an explanatory diagram illustrating an example of calculating an intraocular pressure value from a light intensity change curve of a person with high intraocular pressure. It is.
FIG. 16 is a control circuit diagram of the non-contact tonometer according to the present invention.
[Explanation of symbols]
11 LED (projection means)
17 ... Injection nozzle (air flow blowing means)
53: Light receiving sensor (light receiving optical system)
D, D ': light intensity change curve C: eye cornea Dm, Dm': predetermined deformation point

Claims (1)

Projecting means for projecting the measurement light beam onto the cornea of the eye to be inspected, a light receiving sensor receiving the reflected light of the measurement light beam from the cornea of the eye to be inspected, and guiding the reflected light of the measurement light beam from the cornea of the eye to be inspected to a light receiving sensor A corneal deformation detection optical system, airflow blowing means for blowing the air pulse to the cornea to be examined to deform the cornea to be examined, and the light receiving sensor when the cornea to be examined is deformed by the airflow spraying means. Calculation means for calculating intraocular pressure by obtaining a predetermined deformation point of the cornea of the eye to be examined based on a light amount change curve that is an output change,
The calculating means calculates the reflected light quantity corresponding centroid by integrating the light quantity of a portion of the light quantity change curve which is equal to or higher than a predetermined light quantity detection level , and calculates the pressure of the air pulse corresponding to the calculated reflected light quantity corresponding centroid point. The eye pressure value of the cornea to be examined is obtained from the above, and when the intraocular pressure value of the cornea to be examined exceeds a predetermined value, the point at which the maximum light amount of the light amount change curve is obtained is determined by the predetermined deformation of the cornea to be examined. noncontact tonometer characterized by calculating a point.

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