JPH0394729A - Non-contact type ophthalmotonometer - Google Patents

Abstract

PURPOSE:To reduce a measuring error in the inspection of the eye by providing a solution injection means, an intraocular pressure detecting means, a varying means and a judging means for a fluid injecting state, and a stopping means for the pressurization of fluid. CONSTITUTION:A piston 2 is driven with a solenoid 1, and the air in a compression room is compressed and is injected from a nozzle 4 to a cornea Ec, and the cornea Ec begins to be deformed. When the pressure stabilized state of the cornea Ec is obtained, a light quantity made incident on a light receiving sensor 17 is maximized, therefore, pressure at a time tp when the output of the light receiving sensor 17 arrives at the peak is detected with a pressure sensor 5, and intraocular pressure is calculated from a conversion equation by using a pressure value. At such a case, since the driving current of the solenoid 1 is varied with a resistor RH by switching a switch 23, the ratio of rise of the pressure in the compression room 3 can be moderated. Furthermore, when the pressure arrives at pressure Ps set on a memory 25 before the output S of the light receiving sensor 17 arrives at the peak in an MPU 21, or an error occurs due to the non-detection of the deformation of the cornea, energizing to the solenoid 1 is stopped, thereby, no unrequired air is injected to the eye E to be inspected.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a non-intraocular device that measures the intraocular pressure of the eye to be examined by spraying compressed fluid onto the eye to deform the cornea and optically detecting the deformation. This article concerns contact-type tonometers. [Prior Art] Conventionally, this type of non-contact tonometer generally uses compressed air as the compressed fluid. For example,
As disclosed in Japanese Patent Publication No. 38437 and Japanese Patent Publication No. 61-321, air in a compression chamber is gradually compressed by a piston driven by a solenoid, and this compressed air is injected into the cornea of the eye to be examined through a nozzle. The system measures the time it takes for the cornea to reach an applanation state, and then turns off the power to the solenoid. In this case, detection of corneal deformation is done optically, but if this detection is not done within the time from the start of air compression until the compression pressure reaches its maximum, it is considered an error and the energization of the solenoid is stopped. ．．
Therefore, if an error occurs, it means that the maximum capacity air of the device is being injected into the eye to be examined. [Problems to be Solved by the Invention] However, the situation in which a predetermined corneal deformation signal cannot be obtained occurs not only when the intraocular pressure of the eye to be examined exceeds the measurement range of the device, but also when the eye to be examined has low intraocular pressure. However, it can also occur due to misalignment due to poor fixation of the subject's eye. With conventional devices, even in the latter case, the maximum air pressure of the device is injected into the subject's eye, which can cause disadvantageous factors such as blowing away the tear fluid from the subject's eye, which may be detrimental to the next step, such as eye refraction measurement. It's creating. In addition, the subject may feel uncomfortable due to the excessive shock, and may easily fall into a mentally unstable state, resulting in poor fixation or increased blinking frequency during the next measurement. The disadvantage is that it becomes difficult.

SUMMARY OF THE INVENTION An object of the present invention is to provide a non-contact tonometer that eliminates the above-mentioned drawbacks and is provided with a means for making a quasi-value for determining an error variable in accordance with past conditions. [Means for Solving the Problems] In order to achieve the above object, the non-contact tonometer according to the invention includes a fluid ejection means that pressurizes fluid over time and sprays it onto the cornea of the eye to be examined. , an intraocular pressure measuring means for detecting that the cornea is in a predetermined deformed state due to the fluid and measuring the intraocular pressure value; a variable means for varying a reference value for stopping the fluid ejection state; The present invention is characterized by comprising a determining means for determining whether a reference value is exceeded, and a stopping means for stopping pressurization of the fluid based on the output of the determining means. [Function] The non-contact tonometer with the above structure makes the criterion for judgment when a predetermined deformation detection signal cannot be obtained variable according to the condition of the eye to be examined, thereby reducing measurement errors. [Example] The present invention will be explained in detail based on the illustrated example. FIG. 1 shows a diagram of the structure of a non-contact tonometer according to the present invention,
A piston 2 driven by a solenoid 1 is connected to a compression chamber 3
The air in the compression chamber 3 is compressed, and this compressed air is blown through a nozzle 4 onto the corner 1iEc of the eye E to be examined. Further, a pressure sensor 5 is provided inside the compression chamber 3 to measure the internal pressure of the compression chamber 3.
A portion of the compression chamber 3 corresponding to the optical path L is provided with transparent windows 6 and 7 made of a transparent material, and the nozzle 4 is attached to the center of the transparent window 6. On the optical path L behind the transparent window 7, following the objective lens 8, there is a half mirror 9,
1O is obliquely installed, and furthermore, an imaging lens 1l and a television camera 1 are installed.
2 are arranged in sequence, and the output of the television camera l2 is connected to the television monitor l3. On the optical axis of the reflection side of the half mirror 9, a lens 14 and an infrared light source 15 for alignment of an infrared light emitting diode, etc. are arranged, and on the optical axis of the reflection side of the half mirror 10, a lens 16 and a light receiving sensor are arranged. 1
7 is placed. The light receiving sensor 17 is configured so that the amount of incident light becomes maximum when the cornea Ec is in an applanation state, and a plurality of light emitting elements l8 for extraocular illumination are provided around the transparent window 6. ．． The output of the pressure sensor 5 is connected to an MPU (microprocessor unit) 21 via an amplifier 19 and an A/D converter 20. Also, M.P.
The output of the reset switch 22 is connected to U21, and M
The output of PU2L is connected to analog switch 23. The analog switch 23 operates to selectively connect the source resistor RL or RH to the solenoid control circuit 24 that drives the solenoid 1. Furthermore. A memory 25, a measurement range selector switch 26, a print switch 27, and a left/right eye selector switch 28 are connected to the MPU 21. Next, to explain the operation of the apparatus, the eye image Ea to be examined is formed on the television camera 12 through the transparent windows 6, 7, the objective lens 8, and the imaging lens 11, and the cornea Ec is emitted from the infrared light source 15. The examiner observes the light source image L5a reflected on the television monitor 13 and performs alignment. When this alignment is completed, the solenoid 1 is automatically or manually energized at time 10 as shown in FIG. Ru. Therefore, as described above, the piston 2 is driven by the solenoid 1, and the air in the compression chamber 3 is compressed and flows from the nozzle 4 to the corner 11iEc.
The cornea Ec begins to deform. PNI indicates the increase in pressure within the compression chamber 3 detected by the pressure sensor 5, and S is the output of the light receiving sensor 17. And corneal Ec
When in the applanation state, the amount of light incident on the light receiving sensor 17 becomes maximum, so the pressure at the time tp when the output of the light receiving sensor 17 reaches its peak is detected by the pressure sensor 5,
Using this pressure value, calculate the intraocular pressure using a conversion formula prepared in advance. Furthermore, the measurement range can be changed by using the analog switch 23 to switch between the field-effect transistor field-effect transistor resistances RL and Rl included in the solenoid control circuit 24 that controls the current flowing to the solenoid l. Figure 3 shows the situation when the switch 23 is changed to a lower measurement range. In this case, compression chamber 3
PN2 shows how the internal pressure increases, but since the drive current of solenoid L is changed by resistor RH, the rate of increase is gradual. In the initial state of the device, that is, when the power is turned on, if misalignment occurs due to poor fixation of the eye E during the first measurement, and a reference time tSl or ts2 elapses without optically detecting corneal deformation. , an operation is performed to stop the energization of the lenoid 1. At this time, the pressure change inside the compression chamber 3 is
It is represented by PEI and PE2 in Fig. 3. In terms of the operation of the device, when the time tsl preset in the memory 25 has elapsed before the peak of the output S of the light receiving sensor 17 is detected by the MPU 21, the energization is stopped via the lenoid control circuit 24. Let's do it. Also,
The MPU indicates that the measurement range selector switch 26 has been turned on.
21 recognizes the time ts set in the memory 25.
2 is selected, and the energization to solenoid l is stopped after time ts2 has elapsed. In this way, the set value in the memory 25 can be selected by switching the measurement range, and the injection of excess air depending on the measurement range can be prevented. In addition, after even one measurement has been performed, the memory 25 stores the maximum time ts▼, which takes into account the error for each measurement of the same eye E, corresponding to the time Mtp up to the corneal applanation of the previous measurement, for example, the time tp's 1.
Memorize the time ts▼ that will triple the time. By doing this, even if corneal deformation is not detected later and an error occurs, it is possible to stop the current supply to the lens l after the time ts▼ has elapsed, and excess air is not injected into the eye E to be examined. Moreover, the amount of air can be minimized. The value in the memory 25 is determined by means such as the print switch 27 or the left/right eye changeover switch 28 that allows the user to select the end of the measurement.
It is connected to U21, and the time tp until corneal applanation is reset in accordance with the change of examinee or eye E to be examined. Next, as another embodiment, an example will be described in which control is performed based on the progress of the increase in the output of the pressure sensor 5 instead of controlling the passage of time. As shown in FIG. 5, the pressure sensor 5 detects an increase in the pressure inside the compression chamber 3 without optically detecting the deformation of the cornea Ec, and when the pressure reaches a predetermined pressure Ps, the energization to the lensoid 1 is stopped. Avoid injecting excess air into the eye E to be examined. This is similar to the previous example, and MP
If the pressure Ps set in the memory 25 is reached before the output S of the light receiving sensor 17 reaches its peak within the Uzl, the energization is stopped via the solenoid control circuit 24 IE. Of course,
When the measurement range is changed, the set value in the memory 25 is selected, and the previous pressure measurement value P of 1.3
It is also possible to detect an error at twice the time and stop driving the lenoid l at that point. And print switch 27
The previous pressure measurement value P
It is also possible to reset the , as in the previous embodiment. [Effects of the Invention] As explained above, the non-contact tonometer according to the present invention uses a reference value of time or pressure to determine an error state in which corneal deformation is not detected due to poor fixation of the subject's eye. By providing a means to make it variable depending on the past state of the eye, the maximum air pressure will not be injected into the eye to be examined, and fixation can be stabilized without causing excessive shock or discomfort to the eye to be examined. , it is possible to perform continuous measurements with high accuracy.

[Brief explanation of drawings]

The drawings show an embodiment of a non-contact tonometer according to the present invention,
Figure 1 is a diagram of its configuration, Figure 2 is a graph of pressure sensor output versus time over a wide measurement range, Figure 3 is a graph of pressure sensor output versus time over a narrow measurement range, and Figure 4 is a graph of pressure sensor output versus time over a narrow measurement range. The figure is a graph when the minimum air injection is set, and Figure 5 is a graph of pressure sensor output versus time based on pressure rise.

Claims (1)

[Claims] 1. Fluid ejection means that pressurizes fluid over time and sprays it onto the cornea of the eye to be examined, and measures the intraocular pressure value by detecting that the cornea is in a predetermined deformed state due to the fluid. an intraocular pressure measuring means, a variable means for varying a reference value for stopping the fluid ejection state, a determining means for determining whether the fluid ejecting state exceeds the reference value, and pressurizing the fluid based on the output of the determining means. A non-contact tonometer characterized by having a stop means for stopping. 2. The non-contact tonometer according to claim 1, wherein the reference value is a predetermined elapsed time after fluid injection. 3. The non-contact tonometer according to claim 1, wherein the reference value is the fluid pressure within the fluid ejecting means. 4. The non-contact tonometer according to claim 1, wherein the reference value is switched in response to selection of a plurality of intraocular pressure measurement ranges. 5. The non-contact type eye according to claim 1, further comprising a storage means for storing a previous intraocular pressure measurement value, and the reference value is switched based on the previous intraocular pressure measurement value stored in the storage means. Pressure gauge.