JP2000000213A - Non-contact type ophthalmotonometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact type ophthalmotonometer capable of more highly accurately measuring an intraocular tension by taking the hardness or softness of the cornea of an eye to be tested into consideration and correcting a measured intraocular tension value. SOLUTION: This non-contact type ophthalmotonometer is provided with an arithmetic means 74 for projecting a luminous flux to the cornea C of the eye to be tested, detecting the reflected light and computing a cornea thickness and a measurement means 80 for blowing an air stream to the cornea C of the eye to be tested, detecting that the cornea C becomes a prescribed deformation and measuring the intraocular tensions. From the relation of the cornea thickness before a cornea deformation calculated from the arithmetic means 74 and the cornea thickness at the point of time at which the cornea C is deformed, the intraocular tension value calculated by the measurement means 80 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact tonometer for calculating a highly accurate intraocular pressure value.

[0002]

2. Description of the Related Art Conventionally, arithmetic means for projecting a light beam onto a cornea of an eye to be examined and detecting reflected light thereof to calculate a corneal thickness, and blowing an airflow on the cornea of the eye to be examined to deform the cornea to a predetermined degree. 2. Description of the Related Art A non-contact type tonometer including a measuring unit that detects the occurrence of an error and measures an intraocular pressure is known.

[0003] In some of such ophthalmic devices, the measured value of the intraocular pressure is corrected using the measured value of the corneal thickness, and the correction of the measured value of the intraocular pressure is performed by comparing the measured value of the corneal thickness with the true eye. By applying the measured value of the corneal thickness to an empirically created regression equation showing the correlation with the measurement error amount from the pressure, and correcting the measured value of the intraocular pressure in consideration of the measurement error (See, for example, Japanese Patent Publication No. Hei 8-507463).

[0004]

However, in this non-contact tonometer, the corneal hardness is corrected by a regression equation created based on empirical knowledge using only the corneal thickness as a variable. In addition, there is a lack of consideration of softness (hardness). For example, when the cornea is thin but hard, the correction may be insufficient and an accurate intraocular pressure may not be calculated.

SUMMARY OF THE INVENTION It is an object of the present invention to correct a measured intraocular pressure value in consideration of the hardness or softness of a cornea of a subject's eye, thereby enabling a non-contact type intraocular pressure measurement with even higher accuracy. It is to provide a tonometer.

[0006]

In order to achieve the above object, the invention according to claim 1 comprises a calculating means for projecting a light beam onto a cornea of a subject's eye, detecting reflected light thereof, and calculating a corneal thickness.
A non-contact tonometer comprising a measuring means for blowing an airflow against the cornea to be examined and measuring intraocular pressure by detecting that the cornea has undergone a predetermined deformation, wherein the cornea before the corneal deformation calculated from the calculating means The intraocular pressure value calculated by the measuring means is corrected based on the relationship between the thickness and the corneal thickness at the time when the cornea is deformed.

The invention of claim 2 provides the examiner with one of the calculated corneal thickness before corneal deformation, the corneal thickness at the time when the cornea is deformed, the intraocular pressure value, and the corrected intraocular pressure value. It is characterized by comprising a notifying means for notifying.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ophthalmologic apparatus according to the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show optical arrangement diagrams of an ophthalmologic apparatus.
15 (see FIG. 7).

1 and 2, reference numeral 10 denotes an eye E to be examined.
An anterior segment observation system for observing the anterior segment of the eye, 20 is an XY alignment index projection optical system for projecting index light for alignment detection and corneal deformation detection in the XY directions onto the cornea C of the eye E to be examined, Reference numeral 30 denotes a fixation target projection optical system for projecting a fixation target onto the eye E to be examined, and 40 receives reflected light of the XY alignment index light by the cornea C, and the apparatus main body 115 and the cornea C
An XY alignment detecting optical system for detecting the positional relationship of the XY directions in the XY directions, a corneal deformation detecting optical system for receiving the reflected light of the XY alignment index light by the cornea C and detecting the amount of deformation of the cornea C, A slit projection optical system for projecting a slit light beam having a narrower width than the slit light beam, an index projection optical system 90 for projecting an index light beam wider than the slit light beam onto the cornea C obliquely, and 70 a reflected light of the index light beam and the slit light beam by the cornea C Is a light receiving optical system that receives light from a direction symmetrical with respect to the optical axis of the anterior ocular segment observation optical system 10.

The anterior segment observation optical system 10 includes a plurality of anterior segment illumination light sources 11, which are positioned on the left and right of the eye E to be examined and directly illuminate the anterior segment, an airflow blowing nozzle 12, and an anterior segment window glass 13. , Chamber window glass 14, half mirror 1
5. Objective lens 16, half mirrors 17, 18, CCD
It has a camera 19 and O1 is its optical axis.

An anterior segment image of the eye E illuminated by the anterior segment illumination light source 11 passes through the inside and outside of the airflow blowing nozzle 12 and passes through the anterior segment window glass 13, the chamber window glass 14,
The light is transmitted through the half mirror 15, is transmitted through the half mirrors 17 and 18 while being focused by the objective lens 16, and is formed on the CCD camera 19. The anterior segment window glass 13 has power so that the light flux inside and outside the nozzle forms an image on the CCD camera 19. From the nozzle 12, an air puff is blown toward the eye E by airflow blowing means (not shown). The tonometer is constituted by the nozzle 12, the airflow blowing means, the corneal deformation detection optical system 50, and the like.

The XY alignment index projection optical system 20
A XY alignment light source 21 that emits infrared light, a condenser lens 22, an aperture stop 23, a pinhole plate 24, a dichroic mirror 25, and a projection lens 26 that is arranged on the optical path so that the focal point coincides with the pinhole plate 24. , A half mirror 15, a chamber window glass 14, and an airflow blowing nozzle 12.

The infrared light emitted from the XY alignment light source 21 passes through the aperture stop 23 while being focused by the condenser lens 22, and is guided to the pinhole plate 24. The light beam that has passed through the pinhole plate 24 is reflected by the dichroic mirror 25, becomes a parallel light beam by the projection lens 26, is reflected by the half mirror 15, passes through the chamber window glass 14, and passes through the airflow blowing nozzle 12.
XY alignment index light K is formed as shown in FIG. In FIG. 3, the XY alignment index light K is reflected by the corneal surface T so as to form a bright spot image R at an intermediate position between the vertex P of the cornea C and the center of curvature of the cornea C. The aperture stop 23 is provided at a position conjugate with the corneal vertex P with respect to the projection lens 26.

The fixation target optical system 30 includes a fixation target light source 31 that emits visible light, a pinhole plate 32, a dichroic mirror 25, a projection lens 26, a half mirror 15, a chamber window glass 14, and an airflow blowing nozzle 12. Have.

The fixation target light emitted from the fixation target light source 31 passes through a pinhole plate 32 and a dichroic mirror 25, is converted into parallel light by a projection lens 26, and is converted into a parallel light.
After being reflected at 5, the light passes through the chamber window glass 14, passes through the airflow spray nozzle 12, and passes through the eye E to be examined.
It is led to. The subject's gaze is fixed by gazing at the fixation target as a fixation target. The XY alignment detection optical system 40 includes an airflow blowing nozzle 12, a chamber window glass 14, a half mirror 15, an objective lens 16,
It has half mirrors 17 and 18, a sensor 41, and an XY alignment detection circuit.

The luminous flux projected onto the cornea C by the XY alignment index projection optical system 20 and reflected on the corneal surface T passes through the inside of the nozzle 12 and the chamber window glass 14,
The light passes through the half mirror 15, is partially focused by the half mirror 17 while being focused by the objective lens 16, and is partially reflected by the half mirror 18. Half mirror 18
The light flux reflected by forms a bright spot image R′1 on the sensor 41. The sensor 41 is a light receiving sensor capable of detecting a position such as a PSD. The XY alignment detection circuit 42 calculates the positional relationship (XY directions) between the apparatus main body 115 and the cornea C based on the output of the sensor 41 by known means, and calculates the calculation result as a corneal thickness measurement circuit 74 and a control circuit 80. Output to

On the other hand, the cornea C transmitted through the half mirror 18
The light flux reflected by the image is reflected on the CCD camera 19 by a bright spot image R'2.
To form The CCD camera 19 outputs an image signal to the monitor device, and as shown in FIG. 4, an anterior eye image E ′ of the eye E and a bright spot image R′2 of the XY alignment index light are displayed on a screen G of the monitor device. Is done. Note that H ′ is an alignment assist mark generated by an image generating unit (not shown).

Further, a part of the light beam reflected by the half mirror 17 is guided to a corneal deformation detecting optical system 50,
The light passes through the pinhole plate 51 and is guided to the sensor 52. The sensor 52 is a light receiving sensor capable of detecting the amount of light, such as a photodiode.

The slit projection optical system 60 includes a slit light source 61 for emitting infrared light, a condenser lens 62, and a slit 6
3, rectangular aperture stop 64, half mirror 95, aperture stop 6
4 has a projection lens 65 arranged on the optical path so as to make the focal point coincide with that of the projection lens 4. O2 is the optical axis of the slit projection optical system 60.

The infrared light emitted from the slit light source 61 is condensed by a condenser lens 62 and guided to a slit 63. The slit light beam L passing through the slit 63 passes through the aperture stop 64 and the half mirror 95, and is projected on the cornea C by the projection lens 65.

As shown in FIG. 5, a part of the slit light beam L projected on the cornea C is reflected by a corneal surface T which is a boundary surface between the air and the cornea C, and a part of the light beam passing through the corneal surface T. Is reflected by the back surface N of the cornea. The reflected light beam La on the corneal surface T
Is smaller than the light amount of the reflected light beam Lb from the corneal back surface N by one.
About 00 times more. Note that the slit 63 is a projection lens 65
Are provided at positions conjugate with the corneal back surface N.

The light receiving optical system 70 has an imaging lens 71 and a line sensor 72. O3 is the optical axis of the light receiving optical system 70.

The reflected light beam L reflected on the corneal surface T and the corneal back surface N by the slit light beam L of the slit optical system 60
a and Lb are converged by the imaging lens 71 and are displayed on the line sensor 72 as shown in FIG.
3A is formed. FIG. 6A shows the light quantity distribution of the slit image 63A. In FIG. 6A, reference numeral U denotes a peak due to a reflected light beam reflected on the surface T of the cornea C, and reference numeral V denotes a peak reflected on the back surface N of the cornea C. The peak U is the slit image 63A
And the peak V corresponds to the light image 63b.

The output of each address of the line sensor 72 is shown in FIG.
Is input to the Z alignment detection circuit 73 as shown in FIG.

The index projection optical system 90 includes a Z alignment light source 91 for emitting infrared light, a condenser lens 92, and an aperture stop 9.
3. It has a projection lens 65 arranged on the optical path so that the focus coincides with the pinhole plate 94, the half mirror 95, and the pinhole plate 94. The index projection optical system 90 has an index light beam W (see FIG. 9) having a wider width than the slit projection optical system 60.
Is projected onto the cornea C.

The infrared light emitted from the Z alignment light source 91 is condensed by a condenser lens 92, reaches an aperture stop 93, passes through the aperture stop 93, and is guided to a pinhole plate 94. The index light beam W that has passed through the pinhole plate 94 is reflected by the half mirror 95 and guided to the cornea C by the projection lens 65, and forms a bright spot image Q as shown in FIG. Is reflected. Note that the aperture stop 93 is provided at a position conjugate with the corneal vertex P with respect to the projection lens 65.

The target reflected light beam W 'on the corneal surface T of the target light beam W projected by the target projection optical system 90 is converged by the imaging lens 71 to form a bright spot image Q' on the line sensor 72.

The width of the index light beam W projected onto the cornea C by the index projection optical system 90 is set to be larger than the width of the slit light beam L by the slit projection optical system 60. Then, as shown in FIG. 10, the index light beam W projected on the cornea C is reflected by the corneal surface T and the corneal back surface N, and the reflected reflected index light beams Wa and Wb are converged by the imaging lens 71. An aperture image of the aperture stop 93 is formed on the line sensor 72. The light amount distribution of the aperture image is as shown in FIG. 11 because the light amount of the reflected light beam Wa is much larger than the light amount of the reflected light beam Wb. In FIG. 11, the peak indicated by the symbol F indicates the light amount at the center position of the reflected light beam Wa.

Then, the position of the peak F and the line sensor 7
When the reference address 72a substantially coincides with the reference address 72a of the second apparatus, the setting is made so that the rough alignment in the Z direction is completed.
5 can be obtained in the Z direction. Device body 11
When 5 is too close to the cornea C, the light amount distribution is indicated by a one-dot chain line, and when the apparatus main body 115 is too far from the cornea C, the light amount distribution is indicated by a two-dot chain line.

Further, since the width of the reflected light beam Wa is increased due to the wide width of the index light beam W, the apparatus body 115
The line sensor 72 receives the reflected light beam Wa even if the alignment in the Z direction is greatly shifted.

FIG. 6 shows the Z alignment detection circuit 73.
The position information (address information) of the peaks U and V shown in (A) and the peak F shown in FIG. 11 is obtained and output to the control circuit 80 and the corneal thickness measuring circuit (measuring means) 74. Corneal thickness measurement circuit 74
Calculates the thickness of the cornea C based on the position information of the peaks U and V by a known means. Further, the control circuit 80 controls the motor 112 based on the position information of the peaks U and F, moves the apparatus main body 115 in the Z direction, and performs alignment in the Z direction.

FIG. 7 is a side view showing the entire configuration of the ophthalmologic apparatus, and 100 is a base having a built-in power supply. Base 1
At the top of 00, a gantry 101 is a control lever 102
It is provided to be able to move back and forth and left and right by the operation of. The control lever 102 is provided with a manual switch 103, and this manual switch 103 is used in the manual mode. The motor 104 and the support 10 are provided on the
5 are provided. The motor 104 and the support 105 are connected by a pinion rack (not shown),
Is moved up and down (Y direction) by a motor 104. A table 106 is provided at the upper end of the column 105.

The table 106 has a column 107, a motor 1
08 is provided. A table 109 is slidably provided at the upper end of the column 107. At the rear end of the table 109, a rack 110 is provided as shown in FIG. A pinion 111 is provided on the output shaft of the motor 108, and the pinion 111 is engaged with the rack 110. Further, a motor 112 and a support 113 are provided on an upper portion of the table 109. The output shaft of the motor 112 is provided with a pinion 114. An apparatus main body 115 is slidably provided above the support 113. A rack 116 is provided on the side of the apparatus main body 115. The rack 116 is engaged with the pinion 114. 1 and 2 are provided inside the apparatus main body 115.
The optical system shown in FIG.

The motors 104, 108, 112 are controlled by control signals output from the control circuit 80 described above. When the control signal is output to the motor 104, the movement in the Y direction is performed. When the control signal is output to the motor 108, the movement in the X direction is performed.
When the control signal is output to the control signal 2, the movement in the Z direction is controlled, whereby the alignment adjustment is automatically performed.

Next, the operation of the non-contact tonometer of the above embodiment will be described.

First, the fixation target light source 3 of the fixation target optical system 30
1 is turned on to fixate the eye to be examined, and the Z alignment light source 91 of the index projection optical system 90 is turned on. Then, the examiner performs rough alignment while observing the anterior eye image E ′ of the subject on the screen G of the monitor by the anterior eye observation system 10. At this time, based on the output of the sensor 41 of the XY alignment detecting optical system 40 and the output of the line sensor 72 of the light receiving optical system 70, the XY alignment detecting circuit 42 and the Z alignment detecting circuit 73 The position of the apparatus main body 115 is calculated, and the calculated position is displayed on a monitor screen (notification means) G to notify the examiner. At this time, the light source 61 of the slit projection optical system 60 is turned off.

The position of the apparatus main body 115 in the Z direction is determined based on the position information of the peak F shown in FIG.
Is large, the line sensor 72 receives the reflected light beam Wa even if the alignment in the Z direction is largely shifted, so that the position of the apparatus main body 115 in the Z direction, that is, the direction of the positional shift can be known, and the screen G is displayed. The movement direction and position of the apparatus main body 115 in the Z direction can be displayed.
15 can be quickly moved in a proper direction in which the alignment is performed.

The examiner moves the gantry 10 based on the display on the screen G.
When the positional relationship between the control body 115 and the cornea C to be examined reaches a predetermined distance, the control circuit 80 drives and controls the motors 104, 108, 112 to move the apparatus body 115 in the alignment direction. Let me do it.

Each motor 104, 108, 1 of the control circuit 80
When the alignment of the apparatus main body 115 with respect to the cornea C to be examined is roughly performed by the drive control of 12, the bright spot image R'2 on the monitor screen G is located at the center of the alignment auxiliary mark H ', and When the peak F shown in FIG. 11 is located near the reference position 72a of the line sensor 72, the Z alignment light source 91 of the index projection optical system 90 is turned off and the light source 61 of the slit projection optical system 60 is turned on. .

Immediately before the Z alignment light source 91 is turned off, the Z alignment detection circuit 73 detects the output of the line sensor 72 when the peak F shown in FIG. 11 is located near the reference position 72a of the line sensor 72. The position of the main body 115 in the Z direction is calculated, and the control circuit 80 controls the motor 112 based on the calculated position to move the apparatus main body 115 in the Z direction.

When the light source 61 of the slit projection optical system 60 is turned on, a slit image 63A is formed on the line sensor 72 as shown in FIG. 6B, and based on the light amount distribution of the slit image 63A. Thus, alignment in the Z direction is performed. That is, the apparatus main body 115 is moved in a direction in which the peak U shown in FIG. 6A coincides with the reference position 72a of the line sensor 72. When the bright spot image R'2 is located at the center of the alignment assist mark H 'and the peak U coincides with the reference position 72a of the line sensor 72, that is, the alignment in the XY direction and the Z direction is completed. At this time, the corneal thickness measurement circuit 74 calculates the thickness of the cornea C based on the position information of the peaks U and V output from the Z alignment detection circuit 73 based on the output of the line sensor 72.

When the position information of the peaks U and V is taken in,
An air puff is blown from the nozzle 12 to applanate the cornea C, and the amount of deformation of the cornea C at this time is detected by the corneal deformation detection optical system 50. At the time of this detection, the light sources other than the light source 21 are turned off. The control circuit 80 functions as a measuring unit that calculates the intraocular pressure from the detected amount of deformation of the cornea C and the pressure of the air puff blown from the nozzle 12.

At this time, that is, when the cornea C is in a predetermined applanation state (flat), the light source 61 of the slit projection optical system 60 is turned on again, and as shown in FIG. Is calculated.

FIG. 12 shows the shape and thickness of the cornea C when the cornea C is in a predetermined applanation state (flattened). FIG. 12A shows the case where the cornea C is soft. FIG.
2 (b) shows the case where the cornea C is hard.

In FIG. 12A, the thickness of the cornea C at the portion where the cornea C is in the applanation state is smaller than the other portions, indicating that the cornea C is soft.

On the other hand, in FIG. 12B, the change in the thickness of the cornea C is extremely small, indicating that the cornea C is hard.

The calculated intraocular pressure is the corneal thickness H before the corneal applanation and the corneal thickness h after the corneal applanation (h1, h1,
h2) and the difference (Hh) between the corneal thicknesses before and after corneal applanation is corrected. In other words, not only the corneal thickness but also the hardness of the cornea C is calculated as a difference in corneal thickness (Hh) before and after applanation, and the information is added to the intraocular pressure correction.

FIG. 13 shows an empirically obtained correlation Re when the measured intraocular pressure value is corrected by the thickness change rate C1 = (Hh) / H which means the hardness of the cornea C. Show. This correlation curve is obtained by extracting the relationship between the thickness change rate C1 and the intraocular pressure value P from a population having a standard intraocular pressure of 15 mmHg and a thickness H of the cornea C of 0.5 mm. In FIG. 13, P0 indicates a true intraocular pressure, and there is an average value mC1 of the thickness change rate C1 corresponding to this P0. Thickness change rate C1
Is larger than the average value mC1, which means that the cornea C is soft. As the thickness change rate C1 increases, the measured intraocular pressure value P greatly deviates from the intraocular pressure P0 to a larger value, and the thickness change rate C1 is smaller than the average value mC1.
It means that the cornea C is hard. As the thickness change rate C1 decreases, the measured intraocular pressure value P largely deviates from the true intraocular pressure value P0 to a smaller value, and a correction amount for the hardness of the cornea C is obtained from these relationships. Here, the intraocular pressure is set to 15 mmHg, but correction can be made for other intraocular pressures by making a similar correlation.

Information on the relationship between the thickness of the cornea C before applanation, the thickness of the cornea C after applanation, and the corneal thickness before and after applanation;
The calculated intraocular pressure and the corrected intraocular pressure are displayed on the monitor screen G.

The air puff is blown out of the nozzle 12 by air flow blowing means (not shown), and the pressure of the air puff is detected by a pressure sensor (not shown) provided in the air flow blowing means. is there.

[0052]

As described above, according to the present invention, not only is the corneal thickness affecting the intraocular pressure measurement calculated, and the measured value of the intraocular pressure is corrected using only this corneal thickness.
The hardness or softness of the cornea is considered as the rate of change of the corneal thickness before and after corneal deformation, and the measured value of intraocular pressure is additionally corrected using the rate of change of the corneal thickness, based on the corneal hardness. It is possible to provide a non-contact tonometer capable of eliminating a measurement error and enabling a more accurate measurement of an intraocular pressure.

[Brief description of the drawings]

FIG. 1 is a plan view showing an arrangement of an optical system of an ophthalmologic apparatus according to the present invention.

FIG. 2 is a side view showing the arrangement of the optical system of the ophthalmologic apparatus shown in FIG. 1;

FIG. 3 is an explanatory diagram of reflection of an alignment light beam applied to the cornea from the front.

FIG. 4 is an explanatory diagram showing an anterior segment image displayed on a screen of a monitor.

FIG. 5 is an explanatory diagram showing a state in which a slit light beam is projected on a cornea from an oblique direction.

FIG. 6A is an explanatory diagram showing a light amount distribution of a line sensor. (B) It is explanatory drawing which showed the slit image formed on a line sensor.

FIG. 7 is a side view showing the entire apparatus of the ophthalmologic apparatus in FIG. 1;

FIG. 8 is a plan view showing a main part of the ophthalmologic apparatus of FIG. 1;

FIG. 9 is an explanatory diagram showing a relationship between a cornea and an index light beam.

FIG. 10 is an explanatory diagram showing a state where an index light beam is projected on the cornea.

FIG. 11 is an explanatory diagram showing a light amount distribution on a line sensor when an index light beam is projected on a cornea.

FIGS. 12A and 12B are explanatory views showing a state in which a slit light beam at the time of corneal applanation is projected onto the cornea from an oblique direction. FIG. 12A shows a case where the cornea is soft, and FIG. 12B shows a case where the cornea is hard.

FIG. 13 is a diagram showing a correlation between a thickness change rate C1 meaning the hardness of the cornea and a measured intraocular pressure value P.

[Explanation of symbols]

 Reference Signs List 60 Slit projection optical system 70 Light receiving optical system 72 Line sensor 74 Corneal thickness measuring circuit (arithmetic means) 80 Control circuit (measuring means) 90 Index projection optical system C Eye cornea C1 Thickness change rate meaning hardness of cornea

Claims (2)

[Claims] 1. An arithmetic unit for projecting a light beam onto a cornea of a subject's eye and detecting a reflected light thereof to calculate a corneal thickness, and blowing an airflow onto the cornea of the subject's eye to cause a predetermined deformation of the cornea of the subject's eye. A non-contact tonometer provided with measuring means for detecting the intraocular pressure by detecting that the corneal thickness before the corneal deformation calculated by the arithmetic means and the corneal thickness at the time when the cornea is deformed. A non-contact tonometer, wherein the tonometry value calculated by the means is corrected. 2. A notifying means for notifying an examiner of one of the calculated corneal thickness before corneal deformation, the corneal thickness at the time when the cornea is deformed, the intraocular pressure value, and the corrected intraocular pressure value. The non-contact tonometer according to claim 1, wherein the tonometer is provided.