JP3429028B2 - Non-contact tonometer - Google Patents

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 measuring the intraocular pressure of the eye to be inspected in a non-contact manner by optically detecting the deformation of the eye to be inspected when gas is ejected. Regarding improvement.

[0002]

2. Description of the Related Art A non-contact tonometer of this type is, for example, as disclosed in Japanese Patent Publication No. 56-6772, a gas injection device for deforming the eye by blowing gas onto the eye. A light source for illuminating the eye to be inspected, and a corneal deformation detecting means for detecting the deformation of the cornea by receiving the reflected light from the eye to be inspected, based on the gas blowing pressure and the deformation of the cornea of the eye to be inspected Measure intraocular pressure. In the conventional non-contact tonometer, the corneal deformation detecting means is composed of an optical system including one light receiving element.

[0003]

However, in the above-mentioned conventional non-contact tonometer, since only one corneal deformation detecting means is provided, when there is an error in alignment between the eye to be inspected and the apparatus. Will be included in the detected information in an inseparable form.

Further, since the axis of the jet flow of the gas injection device and the optical axis of the corneal deformation detecting means generally do not exactly coincide with each other due to component errors and adjustment errors, deformation of the cornea when gas is blown. Is not necessarily symmetric with respect to the optical axis of the apparatus, and there is a possibility that a single corneal deforming means cannot accurately detect the deformation state.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and can accurately measure the intraocular pressure of the eye to be inspected even when there is an alignment error or a device component error. An object is to provide a non-contact tonometer.

[0006]

In order to achieve the above-mentioned object, a non-contact tonometer according to the present invention is basically configured to optically deform the cornea of a subject eye when a gas is blown to the cornea. A non-contact tonometer for detecting the intraocular pressure by detecting at least 2 and projecting corneal deformation detection light onto the cornea.
One projection optical system, one detection light receiving means for receiving reflected light from the cornea of the one projection optical system, and the other detection light receiving reflected light from the cornea of the other projection optical system e Bei the light receiving means, wherein both the projection optical system of the light source
The wavelengths are different from each other .

[0007]

According to the non-contact tonometer of the present invention, the deformation of the eye to be inspected can be detected by the plurality of corneal deformation detecting means,
Accurate intraocular pressure can be calculated by averaging these detection results, or the reliability of measurement can be determined in consideration of these variations.

[0008]

1 is an anterior ocular segment observation optical system as a main optical system for observing an anterior ocular segment image including an eye to be examined. The anterior segment observation optical system 10 has an objective lens 11 and an imaging lens 12. On the optical axis O of the objective lens 11, a jet nozzle 14 for jetting an air pulse toward the subject's eye 13 is provided. The light flux forming the anterior segment image is the objective lens 11, the half mirror 15, the half mirror 78, the half mirror 22, and the imaging lens.
An image is formed on the CCD camera 16 via 12. Half mirror 15
2 constitutes a part of an alignment optical system 17 for aligning the visual axis O'of the eye 13 to be examined with the optical axis O of the main optical system as shown in FIG. The alignment optical system 17 is an LED 18 as a light source.
And an aperture 19 and a collimator lens 20. The LED 18 emits infrared light.

The collimator lens 20 collimates the infrared light of the LED 18 into a parallel light flux. The parallel light flux is reflected by the half mirror 15, passes through the inside of the injection nozzle 14, and the cornea of the eye 13 to be inspected.
It is emitted toward 21. The parallel light flux is reflected by the cornea 21 and passes through the imaging lens 12 and the half mirror 22 to the CCD.
Guided by the camera 16. Further, a part of the reflected light flux is reflected by the half mirror 22 and guided to the light receiving element 23 to form an index image i3 for visual axis alignment alignment on the CCD camera 16. The anterior ocular segment image and the index image i3 formed on the CCD camera 16 are input to a video signal processing circuit described later to be imaged. The CCD camera 16 projects a reticle image forming the visual axis allowable range mark 3.

From the apex P of the cornea 21 to the tip Q of the injection nozzle 14.
An alignment optical system for setting the working distance W up to is provided separately from the alignment optical system 17. This alignment optical system has index projection optical systems 24 and 25. The index projection optical systems 24 and 25 are provided with an optical axis O of the objective lens 11.
Are arranged symmetrically. The index projection optical system 24 has an LED 26 as a light source. The LED 26 has, for example, a wavelength of 76
Emit 0 nm infrared light. The infrared light emitted from the LED 26 is condensed by the condenser lens 28 and guided to the opening 29. The infrared light is focused on the center of the aperture 29 and then guided to the dichroic mirror 30.

The index projection optical system 25 includes an LED 27 as a light source.
Have. The LED 27 emits infrared light having a wavelength of 860 nm, for example. The infrared light emitted from the LED 27 is condensed by the condenser lens 31 and guided to the opening 32. The infrared light is focused on the center of the opening 32 and then guided to the dichroic mirror 33.

The dichroic mirror 30 has a characteristic of reflecting infrared light having a wavelength of 760 nm and transmitting infrared light having a wavelength of 860 nm. The dichroic mirror 33 has a characteristic of reflecting infrared light having a wavelength of 860 nm and transmitting infrared light having a wavelength of 760 nm. Wavelength 760n reflected by dichroic mirror 30
The m infrared light is guided to the objective lens 34. The infrared light with a wavelength of 860 nm reflected by the dichroic mirror 33 is guided to the objective lens 35.

The objective lenses 34 and 35 face the cornea 21 of the subject's eye 13. The focal position of the objective lens 34 is at the center of the aperture 29. The focal position of the objective lens 35 is at the center of the aperture 32. The infrared light guided to the objective lenses 34 and 35 is the objective lens 34,
The light beams are collimated by 35 and projected on the cornea 21. The parallel light beam projected by the objective lens 34 forms an index image i1 for working distance alignment based on corneal mirror reflection. The parallel light beam projected by the objective lens 35 is an index image i2 for working distance alignment based on corneal mirror reflection.
To form.

The reflected light flux forming the index image i1 is guided to the objective lens 35 so that the focal position of the objective lens 35 is the index image i.
It is a parallel light flux when it is in the formation position of 1. And
The parallel luminous flux is dichroic mirror 33, half mirror
It is guided to the total reflection mirror 37 via 36. Then, the direction is changed by the total reflection mirror 37 and is guided to the total reflection mirror 39 through the relay lens 38. The parallel light flux reflected by the total reflection mirror 39 is redirected by the total reflection mirror 40 and guided to the light receiving element 41.

The reflected light flux forming the index image i2 is guided to the objective lens 34 and is made a parallel light flux when the focal position of the objective lens 34 is at the point of the index image i2. The reflected light flux converted into the parallel light flux by the objective lens 34 passes through the dichroic mirror 30 and is guided to the total reflection mirror 42.
Is guided to the relay lens 43 by. The parallel light flux that has passed through the relay lens 43 is redirected by the total reflection mirrors 44 and 45 to form an image on the light receiving element 41. The index images i1 and i2 are focused and formed on the light receiving element 41 when the distance from the corneal vertex P of the eye to be inspected to the tip Q of the nozzle is a normal working distance, and in other cases, they are separated and formed. To be imaged.

The LEDs 18, 26, 27 are driven by drive circuits 46, 47, 48 as shown in FIG. This drive circuit 46 ~
The control unit 48 is controlled by the control calculation unit 52 having a function described later. The LEDs 26 and 27 are alternately turned on and off as shown in FIG. The output of the light receiving element 41 is input to the signal processing circuit 49, and the output of the light receiving element 23 is input to the signal processing circuit 50.

The signal processing circuit 49 detects the barycentric position of the pair of index images i1 and i2. The signal processing circuit 50 detects the barycentric position of the index image i3. The detection result is stored in the storage circuit 51. The detection data stored in the storage circuit 51 is input to the control calculation circuit 52. The control calculation circuit 52 calculates the distance between the centers of gravity of the pair of index images i1 and i2. The calculation time is shown in Figure 4.
It is repeatedly performed during the period t as shown in FIG.

The control arithmetic circuit 52 is a video signal processing circuit 53.
And also has a function of controlling the fluid ejection drive means 54. The output of the CCD camera 16 is input to the video signal processing circuit 53.
The output of the video signal processing circuit 53 is input to the display means 55.
As shown in FIG. 5, the display means 55 displays the pupil 1, the working distance allowable range mark 2, and the visual axis allowable range mark 3 as the anterior segment image.

The examiner indicates that the index image i3 is the visual axis allowable range mark 3
The optical axis O of the optical system is adjusted with respect to the visual axis O ′ so as to enter the inside. On the other hand, the video signal processing circuit 53 displays the working distance W on the bar graph 56 'based on the calculation result of the control calculation unit 52. The working distance W is adjusted so that the shaded area of the bar graph 56 'is within the working distance range mark 2. W '
Indicates that the working distance W is optimum.

The control arithmetic circuit 52 determines whether the working distance is within the allowable range, and also determines whether the visual axis of the eye 13 to be examined is within the visual axis allowable range mark 3 to determine the working distance W. When both the visual axis 4 and the visual axis 4 are set within the permissible range, a fluid ejection drive start signal is output toward the fluid ejection drive means 54.
The fluid ejection drive means 54 automatically ejects the cornea from the ejection nozzle 14.
Inject air pulse toward 21.

The air pulse may be jetted by a manual switch. In this case, the air pulse is forcibly ejected, but if there is no change in the light amount of the light receiving element 23 or 41 immediately after the air pulse ejection, the ejection of the air pulse is automatically stopped.

As shown in FIG. 7, LED 26, condenser lens 28, aperture 29, dichroic mirror 30, objective lens
Reference numeral 34 functions as a first detection light projection optical system that projects the corneal deformation detection light toward the cornea 21 in order to optically detect the deformation of the cornea due to the ejection of the air pulse. The cornea 21 is applanated by the jet of air pulses.

The reflected light beam due to the deformation of the cornea passes through the objective lens 35 and the dichroic mirror 33 and the half mirror 36.
Is guided to the condenser lens 56 and is focused on the light receiving element 57 by the condenser lens 56. The objective lens 35, the dichroic mirror 33, the half mirror 36, the condenser lens 56, and the light receiving element 57 are the first corneal deformation detecting means for receiving the corneal deformation detecting light reflected by the cornea 21, that is, the first detecting light receiving hand.
A step is formed, and the amount of light received by the light receiving element 57 increases as the cornea 21 starts to deform. The intraocular pressure is measured according to a known procedure based on the increase in the amount of light received due to the deformation of the cornea 21.

At the same time, the LED 27, the condenser lens 31,
The opening 32, the dichroic mirror 33, and the objective lens 35 function as a second detection light projection optical system that projects the corneal deformation detection light toward the cornea in order to optically detect the deformation of the cornea due to the ejection of the air pulse. . The cornea 21 is in a state of being flattened by the jet of the air pulse.

The reflected light beam due to the deformation of the cornea passes through the objective lens 34 and the dichroic mirror 30 and the half mirror 68.
Is guided to the condenser lens 66 and is focused on the light receiving element 67 by the condenser lens 66. The objective lens 34, the dichroic mirror 30, the half mirror 68, the condenser lens 66, and the light receiving element 67 are the second corneal deformation detecting means for receiving the corneal deformation detecting light reflected by the cornea 21, that is, the second detecting light receiving hand.
A step is formed, and the amount of light received by the light receiving element 67 increases with the start of deformation of the cornea 21. The intraocular pressure is measured according to a known procedure based on the increase in the amount of light received due to the deformation of the cornea 21.

FIG. 8 is a diagram showing a third corneal deformation detection optical system. Infrared light from LED18 is collimator lens
The light flux is collimated by 20 and reflected by the half mirror 15 and is emitted toward the cornea 21 of the subject's eye 13 through the inside of the ejection nozzle 14. LED18, aperture 19, collimator lens
20, the half mirror 15 functions as a third detection light projection optical system that projects corneal deformation detection light toward the cornea in order to optically detect the deformation of the cornea due to the ejection of the air pulse.

The reflected light due to the deformation of the cornea passes through the inside of the jet nozzle 14 and is reflected by the half mirror 78 through the half mirror 15 and focused on the light receiving element 77 by the condenser lens 76. The half mirror 78, the condenser lens 76, and the light receiving element 77 are the third corneal deformation detecting means for receiving the corneal deformation detecting light reflected by the cornea 21, that is, the third corneal deformation detecting means .
3 detection light receiving means . The intraocular pressure is measured according to a known procedure on the basis of the increase in the amount of received light due to the deformation of the cornea 21.

The measured values obtained from the first, second and third corneal deformation detecting means are averaged and displayed as an intraocular pressure value on a monitor (not shown). By averaging the measured values,
It is possible to reduce the influence of an adjustment error during manufacturing and an alignment error during measurement, and it is possible to improve the accuracy of measurement.

Further, when the difference between the measured values obtained from the first, second and third corneal deformation detecting means is more than a predetermined value, for example, the numerical value displayed on the monitor is enclosed in (). By displaying that the measurement reliability is low, the reliability of the displayed intraocular pressure value can be easily determined.
Further, in each of the first, second, and third corneal deformation detection means, the amount of light received increases as the cornea 21 deforms, and the cornea 21
It is also possible to calculate the points at which the cornea 21 truly became the predetermined deformation by obtaining the respective points at which the predetermined deformation occurred, and average them to calculate the intraocular pressure according to a known procedure. Further, by omitting each of the first, second, and third corneal deformation detecting means that does not increase the predetermined amount of received light, it is possible to obtain a more accurate intraocular pressure value. In addition, the intraocular pressure may be calculated based on the data of the corneal deformation detecting unit that has received the maximum amount of received light.

FIG. 9 is a diagram showing another embodiment of the present invention. Half mirror 78, condenser lens 81, aperture 82,
The light receiving element 83 constitutes an optical system for receiving the reflected light in the corneal deformation process, and the reflected light is incident on the light receiving element 83 when the cornea 21 has a predetermined shape before the applanation state due to the ejection of the air pulse. Is configured.

When the light receiving element 83 receives a predetermined amount of light or more, it outputs a fluid ejection stop signal to the fluid ejection driving means 54. As a result, the power supply to the fluid ejection drive means 54 is stopped, but the air pulse from the ejection nozzle continues to be ejected for a certain period of time due to inertia. Due to this inertia, the cornea 21
If the output timing of the fluid ejection stop signal is determined so as to be applanated, after the eye to be examined is applanated and the intraocular pressure is measured, the injection of the air pulse to the eye to be examined is immediately stopped, Compared with the case where the fluid ejection stop signal is output after the measurement of the intraocular pressure is completed, the burden on the subject can be reduced.

[0032]

As described above, according to the non-contact tonometer of the present invention, by providing a plurality of means for receiving the detection light reflected from the subject's eye, the error contained in the measured intraocular pressure value can be reduced. The influence can be reduced and the measurement accuracy can be improved.

Further, the reliability of the measurement can be judged by taking into consideration the variation of the plurality of measured intraocular pressure values.

[Brief description of drawings]

FIG. 1 is a plan view of an optical system of a non-contact tonometer according to an embodiment of the present invention.

FIG. 2 is a side view of the optical system shown in FIG.

FIG. 3 is a control block diagram of the tonometer of the embodiment.

FIG. 4 is a timing chart of on / off control of LEDs of the tonometer of the embodiment.

FIG. 5 is an explanatory diagram of an alignment display state of the tonometer of the embodiment.

FIG. 6 is an explanatory diagram of a conventional alignment display state.

FIG. 7 is an explanatory diagram of an optical system showing first and second corneal deformation detecting means of the tonometer of the embodiment.

FIG. 8 is an explanatory view of an optical system showing a third corneal deformation detecting means of the tonometer of the embodiment.

FIG. 9 is an explanatory diagram of an optical system showing another embodiment of the present invention.

[Explanation of symbols]

4 visual axis 13 eye 17 Alignment optical system 21 cornea

Claims (4)

(57) [Claims] 1. A non-contact tonometer that optically detects deformation of the cornea when gas is blown to the cornea of an eye to be examined to measure intraocular pressure, and projects corneal deformation detection light onto the cornea. At least two projection optical systems, one detection light receiving means for receiving the reflected light from the cornea of the one projection optical system, and the other for receiving the reflected light from the cornea of the other projection optical system. and a detection light receiving means, wherein both projection
A non-contact tonometer characterized in that the wavelengths of light sources of optical systems are different from each other . 2. A measurement obtained from both the detection light receiving means.
The feature is that the intraocular pressure is calculated based on the average value of the fixed values.
The non-contact tonometer according to claim 1 . 3. The amount of light received by both of the detection light receiving means is
The intraocular pressure is based on the measurement value of the larger detection light receiving means.
The non-contact tonometer according to claim 1, wherein 4. The non-contact tonometer according to claim 1, wherein spraying of the gas is controlled based on information of at least one detection light receiving means of the plurality of detection light receiving means. .