JP4644842B2 - Non-contact tonometer - Google Patents

Description

  The present invention relates to an improvement in a non-contact tonometer that can measure the hardness of the cornea (corneal stiffness).

The non-contact tonometer measures the intraocular pressure by blowing airflow onto the cornea of the subject's eye, detecting the time from the start of blowing the airflow to the cornea until the predetermined amount of deformation of the cornea, and the cornea Since the time it takes for the cornea to collapse after being applanated and the collapsed cornea reverts to its original applanation depends on the hardness of the cornea, by measuring this recovery time, the hardness of the cornea is estimated, and the eye The thing of the structure which correct | amends a pressure is known (for example, refer patent document 1).
JP 2000-212 JP

  By the way, in general, when the intraocular pressure is high, the amount of displacement of the cornea (the amount of depression) is small, and when the intraocular pressure is low, the amount of deformation of the cornea is large. In the conventional non-contact tonometer, this cornea is from the applanation time of the cornea. Corneal hardness is measured by adopting a configuration that measures the time until the point of restoration until the depressed cornea is restored to its original applanation state. At this time, there is a problem that the degree of influence of intraocular pressure is large.

  Moreover, since the cornea is depressed and the hardness of the cornea is measured, the burden on the subject is large.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-contact tonometer that is less affected by intraocular pressure and can reduce the burden on the subject. To do.

  The invention according to claim 1 outputs a light intensity signal by optically detecting the airflow blowing means for deforming the cornea by blowing an airflow on the cornea of the eye to be examined, and the deformation of the cornea by the airflow blowing means. The corneal deformation detection means and the predetermined time point at which the light intensity signal is acquired at a predetermined time point corresponding to the skirt portion of the rising edge of the light intensity signal are measured from the start of operation of the airflow blowing means. Time measuring means for converting the light intensity signal into an amount of corneal deformation, and an internal pressure of the airflow blowing means corresponding to the amount of airflow actually blown to the cornea of the eye to be examined and a force at the predetermined time point. And calculating means for obtaining the rigidity of the cornea from the relationship.

  The invention according to claim 2 is characterized in that the airflow blowing means is provided with an internal pressure measuring sensor, and the calculation means obtains the internal pressure from the start of operation of the airflow blowing means to the predetermined time in time series. And

  The invention according to claim 3 is characterized in that the calculation means calculates an intraocular pressure of the eye to be examined from a relationship between a light intensity signal of the corneal deformation detection means and an internal pressure of the airflow blowing means.

  The invention described in claim 4 is characterized in that the rigidity of the cornea is notified.

  According to a fifth aspect of the present invention, an air current blowing means for deforming the cornea by blowing an air current on a cornea of an eye to be examined, and a light intensity signal is output by optically detecting the deformation of the cornea by the air current blowing means. The time measurement is started from the start of operation of the corneal deformation detecting means and the airflow blowing means, and the time when the light intensity signal reaches the predetermined light intensity signal corresponding to the skirt portion of the rising edge is measured and the predetermined time is reached. A timing means for acquiring the light intensity signal, and converting the light intensity signal into a corneal deformation amount and corresponding to the corneal deformation amount and a force at the predetermined time point of the airflow actually blown to the cornea of the eye to be examined. And calculating means for obtaining the rigidity of the cornea from the relationship with the time by the time measuring means when reaching a predetermined light intensity signal.

  The invention according to claim 6 is characterized in that the calculation means calculates a corrected intraocular pressure in consideration of rigidity of the cornea.

  According to the present invention, since it is configured as described above, the degree of influence of intraocular pressure is as small as possible and the burden on the subject can be reduced.

  Embodiments of a non-contact tonometer according to the present invention will be described below with reference to the drawings.

Example 1
In FIG. 1 and FIG. 2, S is an apparatus main body. This apparatus main body S is an anterior ocular segment observation system 10 for observing the anterior segment of the eye E, XY alignment for projecting index light for detecting alignment and corneal deformation in the XY directions onto the cornea C of the eye E from the front. Index projection optical system 20, fixation target projection optical system 30 that provides a fixation target to eye E to be examined, positional relationship between XY alignment index light and cornea C in the XY direction by receiving reflected light from cornea C XY alignment detection optical system 40 for detecting the corneal deformation detection optical system (corneal deformation detection means) 50 for detecting the amount of deformation of the cornea C by receiving the reflected light of the XY alignment index light from the cornea C, and Z from the diagonal to the cornea C Z alignment index projection optical system 60 for projecting direction alignment index light, and light reflected by cornea C of Z alignment index light is received from a direction symmetric with respect to the optical axis of anterior ocular segment observation optical system 10. And a Z alignment detection optical system 70 for detecting the Z-direction positional relationship of the Okimoto body S and the cornea C.

  The anterior ocular segment observation optical system 10 is located on the left and right sides of the eye E, and has a plurality of anterior ocular segment illumination light sources 11 that directly illuminate the anterior segment, an airflow spray nozzle 12, an anterior segment window glass 13, and a chamber 14A. , Chamber window glass 14, half mirror 15, objective lens 16, half mirrors 17 and 18, and CCD camera 19, where O 1 is the optical axis thereof. Here, the airflow spray nozzle 12, the anterior ocular window glass 13, the chamber 14 </ b> A, and the chamber windowglass 14 blow an airflow toward the cornea C of the eye E together with a rotary solenoid (not shown) to deform the cornea C. Functions as a means.

  The 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 spray nozzle 12, passes through the anterior segment window glass 13, the chamber window glass 14, and the half mirror 15, and the objective lens. 16 is formed on the CCD camera 19 through the half mirrors 17, 18 while being focused by 16. Note that the anterior ocular window glass 13 has power to form an image of the light flux inside and outside the nozzle 12 on the CCD camera 19.

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

  Infrared light emitted from the light source 21 for XY alignment passes through the aperture stop 23 while being focused by the condenser lens 22 and is guided to the pinhole plate 24. Then, the light beam that has passed through the pinhole plate 24 is reflected by the dichroic mirror 25, converted into a parallel light beam by the projection lens 26, reflected by the half mirror 15, and then transmitted through the chamber window glass 14 to the airflow blowing nozzle 12. Passing through the interior, XY alignment index light K is formed as shown in FIG. In FIG. 3, the XY alignment index light K is reflected on the corneal surface T so as to form a bright spot image R at an intermediate position between the apex 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 apex 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 air blowing nozzle 12.

  The fixation target light emitted from the fixation target light source 31 passes through the pinhole plate 32 and the dichroic mirror 25, becomes parallel light by the projection lens 26, is reflected by the half mirror 15, and then passes through the chamber window glass 14. The light passes through the airflow nozzle 12 and is guided to the eye E to be examined. The subject's line of sight is fixed by gazing at the fixation target as a fixation target.

  The reflected light beam projected onto the cornea C by the XY alignment index projection optical system 20 and reflected by the cornea surface T passes through the nozzle 12, passes through the chamber window glass 14 and the half mirror 15, and is focused by the objective lens 16. A part of the light is transmitted by the half mirror 17 and a part of the light is reflected by the half mirror 18.

  The light beam reflected by the half mirror 18 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 direction) between the apparatus body S and the cornea C based on the output of the sensor 41 by known means, and the calculation result is a Z alignment detection correction circuit 74 and a control circuit. Output to 80.

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

  Further, a part of the light beam reflected by the half mirror 17 is guided to the corneal deformation detection optical system 50, 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 like a photodiode.

  The Z alignment index projection optical system 60 is arranged on the optical path so as to be in focus with the Z alignment light source 61 that emits infrared light, the condenser lens 62, the aperture stop 63, the pinhole plate 64, and the pinhole plate 64. Projection lens 65, and O2 is its optical axis.

  The infrared light emitted from the light source 61 for Z alignment passes through the aperture stop 63 while being condensed by the condenser lens 62 and is guided to the pinhole plate 64. The light beam that has passed through the pinhole plate 64 is converted into parallel light by the projection lens 65, guided to the cornea C, and reflected by the cornea surface T so as to form a bright spot image Q as shown in FIG. The aperture stop 63 is provided at a position conjugate with the corneal apex P with respect to the projection lens 65.

  The Z alignment detection optical system 70 includes an imaging lens 71, a cylindrical lens 72 having power in the Y direction, a sensor 73, and a Z alignment detection correction circuit 74, and O3 is the optical axis thereof.

  The reflected light beam on the corneal surface T of the index light projected by the Z alignment index projection optical system 60 forms a bright spot image Q ′ on the sensor 73 via the cylindrical lens 72 while being focused by the imaging lens 71. The sensor 73 is a light receiving sensor capable of detecting a position, such as a line sensor or PSD. Information from the sensor 73 is guided to the Z alignment detection correction circuit 74. Since the correction by the Z alignment detection correction circuit 74 is described in detail in Japanese Patent Laid-Open No. 2000-212, detailed description thereof is omitted.

  In the XZ plane, the bright spot image Q and the sensor 73 are conjugated with respect to the imaging lens 71. In the YZ plane, the corneal apex P and the sensor 73 are conjugated with respect to the imaging lens 71 and the cylindrical lens 72. It is in a positional relationship.

  That is, the sensor 73 has a conjugate relationship with the aperture stop 63 (the magnification at this time is selected so that the image of the aperture stop 63 is smaller than the size of the sensor 73), and the cornea C is shifted in the Y direction. Also, the reflected light beam on the corneal surface T enters the sensor 73 efficiently.

  Here, a pressure sensor 14B for measuring the pressure in the chamber 14A is provided in the chamber 14A. While observing the anterior segment image E ′ on the monitor screen shown in FIG. 4, the examiner moves the apparatus body S in the XYZ directions so that the bright spot image R′2 enters the alignment auxiliary mark H and is in focus. Manually adjust the alignment.

  At this time, when the outputs of the XY alignment detection circuit 42 and the Z alignment detection correction circuit 74 fall within a predetermined range, the control circuit 80 activates the airflow blowing means and blows the airflow from the airflow blowing nozzle 12 toward the cornea C. . In the embodiment of the present invention, the airflow spraying means is automatically operated. However, a trigger switch (not shown) may be operated to start spraying the airflow to the cornea C.

  When the air flow is started to be blown onto the cornea C, the pressure in the chamber 14A increases as time t passes as indicated by reference numeral F1 in FIG. Next, the force of the airflow actually blown to the cornea C rises as indicated by the symbol F2, slightly behind the increase in the pressure (shown by the solid line) F1 in the chamber.

  The cornea C starts to deform as shown in FIG. 7 with a slight delay from the airflow force F2 (shown by a two-dot chain line) actually blown onto the cornea C, and the output of the light intensity signal S from the sensor 52 is shown in FIG. As shown in FIG. 4, the value rises as time t elapses, and becomes maximum when the cornea C reaches a flat shape. In FIG. 7, the solid line shows the state before the cornea C is deformed, the alternate long and short dash line shows the applanation state of the cornea C, and the broken line shows the state before the cornea C undergoes deformation until it is applanated. Show. Δ indicates the amount of deformation of the cornea C due to airflow spraying. This deformation amount Δ is obtained from the interval from the vertex P of the cornea C before deformation to the vertex P of the cornea C after deformation.

  Between the deformation amount Δ of the cornea C and the light intensity signal S, as shown in FIG. 8, even at the initial stage where the deformation amount Δ of the cornea C is small, that is, at the bottom part Sa of the rising edge of the light intensity signal S, It has been experimentally found that there is a correlation between the deformation amount Δ of the cornea C and the light intensity signal S.

  This correlation indicates that the cornea C of the eye to be inspected is continuously photographed from the side by a high-sensitivity high-speed camera, and the cornea C in the initial stage of airflow spraying of the cornea C by obtaining the value of the light intensity signal S at each photographing time. Is obtained by associating the amount of deformation Δ with the value of the light intensity signal S. FIG. 9 shows the correlation distribution diagram, and the correlation coefficient is about 0.7.

  The control circuit 80 starts timing from the operation start time t0 of the airflow blowing means and measures a predetermined time t1 corresponding to the skirt portion Sa having a low rise in the light intensity signal S, and measures the light intensity signal at the predetermined time t1. It has time measuring means for acquiring S. The predetermined time t1 is, for example, about 10 ms from the operation start time t0 of the airflow blowing means, and the correlation distribution diagram shown in FIG. 9 shows the correlation between the light intensity signal S and the deformation amount Δ.

  The control circuit 80 converts the light intensity signal S into a corneal deformation amount Δ, and the internal pressure F1 of the airflow blowing means corresponding to the corneal deformation amount Δ and the airflow force F2 actually blown to the cornea C of the eye E to be examined. From the relationship, the stiffness k of the cornea C is obtained based on the relational expression F2 = k · Δ. Since the deformation amount Δ of the cornea C is within a minute range, it is considered that the effect of intraocular pressure is hardly received.

  The control circuit 80 measures a predetermined time (predetermined time) t2 at which the cornea C reaches flatness from the operation start time t0 of the airflow blowing means, and acquires an internal pressure F3 corresponding to the predetermined time (predetermined time) t2. . Since there is a correspondence between the internal pressure F3 and the intraocular pressure F4, the intraocular pressure F4 of the eye to be examined can be obtained by acquiring the internal pressure F3 when the cornea C is applanated.

  The control circuit 80 may calculate the intraocular pressure of the eye E based on the relationship between the light intensity signal S of the corneal deformation detection unit and the internal pressure F1 of the airflow blowing unit. Further, the rigidity of the cornea C may be divided into five steps (five steps from 0 (soft) to 5 (hard)) and notified on the monitor screen. Moreover, you may employ | adopt the structure which alert | reports the rigidity of the cornea C by an audio | voice.

Although there are many normal-tension glaucoma patients in Japan, according to the embodiment of the present invention, it is possible to measure intraocular pressure without the influence of eyeball rigidity, and thus early detection of normal-tension glaucoma patients is realized.
(Example 2)
In the first embodiment, the light intensity signal S is converted into the corneal deformation amount Δ and the airflow blowing means corresponding to the corneal deformation amount Δ and the force F2 at the predetermined time point t1 of the airflow actually blown to the cornea C of the eye E to be examined. The stiffness of the cornea C is determined from the relationship with the internal pressure F1, but as shown in FIG. 10, the threshold value SL is set in the skirt portion Sa of the light intensity signal S, and the cornea C reaches a predetermined deformation amount ΔL. The time t1 ′ required for is obtained.

  When the cornea C is soft, the time until the cornea C reaches the predetermined deformation amount ΔL is short and the force F2 is small. When the cornea C is hard, the time until the cornea C reaches the predetermined deformation amount ΔL is long and the force F2 is large. Therefore, the time-force correlation curve shown in FIG. 11 is obtained, and the force F1 can be obtained by measuring the time from the spray start time t0 by the airflow spraying means.

  In FIG. 11, the time t1 ′ indicates the time required to reach the predetermined deformation amount ΔL when the cornea C is soft, and the time t2 ′ reaches the predetermined deformation amount ΔL when the cornea C is hard. The time required is shown, and the forces F2 ′ and F2 ″ applied to the cornea C are obtained from the time t1 ′ and the time t2 ′ using the time-force correlation curve, whereby the stiffness k of the cornea C is obtained. become.

  It is also possible to correct the intraocular pressure value measured using the eye stiffness obtained by the method of the first embodiment and the second embodiment described above. This is performed, for example, by using a correlation indicating a corrected intraocular pressure value corresponding to the obtained intraocular stiffness or a parameter related thereto and the measured intraocular pressure value. In addition to displaying the corrected intraocular pressure value as a measurement result, it is also possible to display an intraocular pressure value before correction and ocular stiffness at the same time.

It is a plane arrangement view of the optical system of the non-contact tonometer according to the present invention. FIG. 2 is a side view of an optical system of the non-contact tonometer shown in FIG. 1. It is explanatory drawing of the reflection of the alignment light beam irradiated to the cornea from the front. It is a figure which shows the anterior ocular segment image displayed on the screen of a monitor. It is explanatory drawing of reflection of the alignment light beam irradiated to the cornea from the diagonal direction. It is a figure which shows the relationship between the force in the chamber of an airflow spraying means, and the spraying pressure of the airflow actually sprayed on a cornea. It is explanatory drawing which shows the deformation | transformation state of a cornea. It is explanatory drawing which represented the relationship between a light quantity intensity signal and a cornea deformation | transformation by making a horizontal axis into a time axis. FIG. 6 is a correlation distribution diagram between a light intensity signal and a corneal deformation amount. It is an enlarged view of the skirt portion of the light intensity signal. It is a figure which shows a time-force correlation curve.

Explanation of symbols

12 ... Nozzle (air flow spraying means)
14A ... chamber (air flow spraying means)
50. Corneal deformation detection optical system (corneal deformation detection means)
80 ... Control circuit (time measuring means, calculating means)

Claims (6)

  An airflow blowing means for deforming the cornea by blowing an airflow on the cornea of the eye to be examined; a corneal deformation detecting means for optically detecting deformation of the cornea by the airflow blowing means and outputting a light intensity signal; and the airflow blowing Clocking means for timing the predetermined time to start timing from the start of operation of the lighting means and to acquire the light intensity signal at a predetermined time corresponding to the bottom of the light intensity signal, and the light intensity signal Is converted into a corneal deformation amount, and the stiffness of the cornea is obtained from the relationship between the corneal deformation amount and the internal pressure of the airflow blowing means corresponding to the force at the predetermined time point of the airflow actually blown onto the cornea of the eye to be examined. A non-contact tonometer comprising a calculation means.   The non-air flow sensor according to claim 1, wherein an internal pressure measurement sensor is provided in the airflow blowing means, and the calculation means obtains the internal pressure from the start of operation of the airflow blowing means to the predetermined time in time series. Contact tonometer.   2. The non-contact tonometer according to claim 1, wherein the calculating unit calculates an intraocular pressure of the eye to be examined from a relationship between a light intensity signal of the corneal deformation detecting unit and an internal pressure of the airflow blowing unit.   The non-contact tonometer according to claim 1, wherein the rigidity of the cornea is notified.   An airflow blowing means for deforming the cornea by blowing an airflow on the cornea of the eye to be examined; a corneal deformation detecting means for optically detecting deformation of the cornea by the airflow blowing means and outputting a light intensity signal; and the airflow blowing The time measurement is started from the time when the lighting means is started, and the time when the light intensity signal reaches the predetermined light intensity signal corresponding to the bottom of the rising edge is measured to obtain the light intensity signal at the predetermined time. Means for converting the light intensity signal into a corneal deformation amount and reaching a predetermined light intensity signal corresponding to the corneal deformation amount and the force at the predetermined time point of the airflow actually blown to the cornea of the eye to be examined A non-contact tonometer comprising: a calculating means for determining the rigidity of the cornea from the relationship with time by the time measuring means.   6. The non-contact tonometer according to claim 1, wherein the calculation unit calculates a corrected intraocular pressure in consideration of the rigidity of the cornea.

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