JP2620774B2 - Non-contact tonometer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact tonometer for applying a predetermined deformation to a cornea of an eye to be examined with a fluid such as air to measure an intraocular pressure in a non-contact manner. .

2. Description of the Related Art Conventionally, a non-contact tonometer described in, for example, Japanese Patent Publication No. 54-38437 is known. This device is a fluid pulse generator that emits a fluid toward the cornea of the eye to be deformed to give a deformation to the cornea of the eye to be examined, and a light detection for detecting that the cornea of the eye to be examined is deformed into a plane by the fluid pulse. The output of the photodetector is configured to produce a maximum output when the cornea is flat. Furthermore, paying attention to the fact that the deformation and recovery time of the cornea when receiving this fluid is correlated with the intraocular pressure, the time is measured and converted into an intraocular pressure value.

That is, FIG. 3 schematically shows the air flow pressure Pe and the output A of the photodetector at the time of the measurement as a function of time, and the time t1 at which the output A of the photodetector peaks is shown. Measurement is performed to convert the air flow pressure Pe at that time into an intraocular pressure value. The relationship between the time and the air flow pressure, that is, the time and the intraocular pressure, is based on the assumption that the air pulse generator generates an air pulse having the same speed and spread every measurement.
To assure this, the air pulse generator is composed of a piston, cylinder, and rotary solenoid manufactured with high precision.

As described above, in the conventional example, it is a necessary condition that the air flow pressure Pe with respect to time exhibits the same characteristic at each measurement, but if this condition is broken, there is a drawback that a direct error occurs in the measurement of the intraocular pressure. That is, the cause of this error is
Variations in the members that make up the air pulse generator, such as variations in the driving force of the rotary solenoid, aging between the piston and cylinder, etc., can be considered.However, in the past, accuracy was guaranteed by quality control and periodic inspection of these members. ing.

Further, in the more advanced tonometer, an inspection mode called a demo mode is set, and it is possible to confirm whether the air pulse generator is operating normally before the measurement. However, even in such a case, since the fluid pressure is not detected after all, it has been difficult to accurately confirm the fluid pressure.

[Object of the Invention] An object of the present invention is to confirm the actual operating state of the fluid emitting means, and to be able to confirm the abnormality when an abnormality occurs, thereby obtaining a highly reliable measurement value. To provide a non-contact tonometer capable of easily confirming the occurrence of abnormalities in the operating state including fluid leakage in a configuration in which fluid is discharged through a fluid compression chamber provided with is there.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide a fluid compression chamber in which an eye path for observing an eye to be examined is disposed and a fluid to be emitted to the cornea of the eye through the fluid compression chamber. Intraocular pressure measurement having a fluid emitting means and a corneal deformation detecting means for detecting that the cornea has undergone a predetermined deformation by the fluid, and measuring an intraocular pressure of the eye to be examined based on an output of the corneal deformation detecting means A pressure sensor for detecting the pressure in the fluid compression chamber, and a tonometer based on a detection signal of the pressure sensor in a state where the tonometry of the subject's eye can be measured by the tonometry means. An operating state detecting means for detecting an operating state of the fluid emitting means, and an abnormality detecting means for detecting whether or not the operation of the fluid emitting means is abnormal based on a detection signal of the operating state detecting means. Non-contact intraocular pressure It is total.

[Embodiment of the Invention] The present invention will be described in detail based on an example of an apparatus for explaining the embodiment shown in FIGS.

FIG. 1 is a configuration diagram of a non-contact tonometer as an example of an apparatus for explaining an embodiment of the present invention, and FIG. 1 (a) is a diagram viewed from a side. Nozzle 1 facing the cornea Ec of the eye to be examined
In addition, an air compression chamber 4 having a glass window 3 formed on the optical axis of the objective lens 2, a harm mirror 5, a focal plane 6, and an eyepiece 7 are disposed behind the objective lens 2, and an examiner O has an eyepiece. The subject's eye can be observed through the lens 7. Also, the focal plane 6 on the reflection side of the half mirror 5
An index 8 is provided at a position conjugate with.

A cylinder 9 and a piston 10 for generating an air pulse emitted to the cornea Ec of the subject's eye through the nozzle 1 are connected to the compression chamber 4, and the piston 10 is driven by a rotary solenoid 11 in the direction of the arrow. Generates an air pulse. The piston 10 is provided with a through hole 10a in a direction orthogonal to the axial direction of the cylinder 9. Further, the cylinder 9 is provided with through openings 12a and 12b, and the light emitting diode 13 is arranged near the opening 12a of the cylinder 9,
The photodetector 14 is arranged near the opening 12b.

FIG. 1 (b) is a plan view of the apparatus, which is composed of two optical systems symmetrical with respect to the optical axis of the objective lens 2, and measures a deformation of the cornea Ec of the eye to be examined due to an air pulse. Is shown. That is, the infrared light emitting diode 15 is
Project the measurement light onto the cornea Ec through the collimator lens 17,
This measurement light is reflected by the cornea Ec, condensed on the pinhole 19 through the condenser lens 18, and received by the photodetector 20 when the cornea Ec undergoes a predetermined deformation such as a plane by an air pulse. It has become. In this optical system, the output of the photodetector 20 is configured to be maximum when the cornea Ec has undergone the above-described predetermined deformation.

The output of the photodetector 14 is connected to a controller 22 via a pulse counting circuit 21, and pulses output from the clock pulse generator 23 are output to the pulse counting circuit 21 and the controller 22.
Connected to 22. The controller 22 has a memory
24, display 25 is connected. Further, the output output from the photodetector 20 and passed through the peak detection circuit 26 is output to the controller 22.
It is connected to the.

In the alignment of the present apparatus, the index 8 is projected onto the cornea Ec of the eye to be examined via the half mirror 5 and the objective lens 2, and the reflected image is formed again on the focal plane 6 of the eyepiece 7 by the objective lens 2. This is performed by a visual alignment system observed by the examiner O through the eyepiece 7.

When the examiner O presses a measurement switch (not shown) after performing alignment using this alignment system, the rotary solenoid 11 is driven, and an air pulse is emitted from the nozzle 1 toward the cornea Ec of the eye to be inspected. The cornea Ec is deformed by this air pulse, and changes the output of the photodetector 20 of the measurement system, but the peak detection circuit connected to the photodetector 20
26 detects the peak of the output, and outputs a detection signal to the controller 22. Upon receipt of this signal, the controller 22 reads the point of occurrence, converts this to an intraocular pressure value and displays it on the display 25.

At this time, the light emitted from the light emitting diode 13 is
Is below the openings 12a, 12b of the cylinder 9 before the start of the measurement, and the piston 10 moves during the measurement,
The light is received by the photodetector 14 when the through hole 10a provided in the piston 10 passes between 12a and 12b. The output signal of the photodetector 14 at this time is as shown in FIG. 2, and the pulse counting circuit 21 uses the clock pulse generation circuit 22 to measure the gap Δt between the two pulses. This pulse gap Δt is proportional to the average moving speed of the piston 10 to be measured,
Ideally, it is always constant, and it can be said that it is most suitable for monitoring the operating state of the fluid emitting means.

The controller 22 determines this pulse gap Δ
t is obtained from the pulse counting circuit 21, and is compared with Δt0 stored in the separately provided memory 24, that is, the pulse gap Δt0 when the piston 10 normally operates during the initial adjustment. Then, if they match, the previously calculated intraocular pressure value is output to the display 25. If the difference between the two is small, the intraocular pressure value is corrected by a separately provided correction function, and the corrected intraocular pressure value is output to the display 25. Further, when the difference between them is equal to or more than a predetermined value, it is clearly determined that the device is malfunctioning, and an error signal is output to the display 25.

Also, as a matter of course, the method of detecting the moving speed of the piston 10 is not limited to the above-described method.
For example, a further effect can be obtained by connecting a rotary encoder to the rotary solenoid 11 and measuring the moving speed of the piston 10 more precisely by the pulse interval.

In the device example for explaining the above-described embodiment, the operating state of the air pulse generator is detected by the moving speed of the piston 10. However, in the non-contact tonometer of the embodiment, the pressure inside the compression chamber 4 is measured. A pressure sensor for measurement is provided to detect an increase in the pressure in the compression chamber 4 after a predetermined time from the start of the movement of the piston 10, thereby detecting the operating state of the pulse generator. Note that the reference value compared in this case is the internal pressure increase value of the compression chamber 4 at the time of the initial adjustment.

[Effect of the Invention] As described above, the non-contact tonometer according to the present invention detects the operating state of the fluid emitting means, and obtains a highly reliable measurement value by confirming the occurrence when an abnormality occurs. This enables stable operation of the device and stable measurement. In particular, since the fluid is discharged through the fluid compression chamber in which the optical path for the eye to be observed is disposed, it is necessary to dispose an optical member or the like in the fluid compression chamber. It is necessary to check the operation state more. In addition, the configuration in which the operation state of the fluid emitting means is detected based on the detection of the pressure sensor that detects the pressure in the fluid compression chamber enables the abnormality of the operation state including the leakage of the compression chamber to be confirmed, so that the operation can be performed more accurately. The state can be confirmed, and further stable operation of the device and stable measurement can be performed. In particular, since it is detected whether or not the operation in the state where the tonometry can be performed is abnormal, the operation state in the actual use state can be confirmed, and the confirmation can be more accurately performed.

[Brief description of the drawings]

The drawings show an embodiment of the non-contact tonometer according to the present invention. FIG. 1 is a configuration diagram thereof, FIG. 2 is an output waveform diagram of a speed detecting photodetector, and FIG. FIG. 3 is a diagram illustrating the measurement principle. 1 is a nozzle, 2 is an objective lens, 4 is an air compression chamber, 9
Is a cylinder, 10 is a piston, 10a is a through hole, 11 is a rotary solenoid, 12a and 12b are openings, 13 and 15 are light-emitting diodes, 14 and 20 are photodetectors, 21 is a pulse counting circuit, 22 is a controller, and 24 is a controller. A memory, 25 is a display, and 26 is a peak detection circuit.

Claims (2)

(57) [Claims] 1. A fluid compression chamber having an optical path for observing an eye to be inspected therein, fluid ejection means for ejecting a fluid to the cornea of the eye via the fluid compression chamber, and a predetermined deformation of the cornea by the fluid. Having corneal deformation detection means for detecting that it has occurred,
A non-contact tonometer having an intraocular pressure measurement unit that measures the intraocular pressure of the subject's eye based on the output of the corneal deformation detection unit, and a pressure sensor that detects a pressure in the fluid compression chamber,
Operating state detecting means for detecting an operating state of the fluid emitting means based on a detection signal of the pressure sensor in a state in which the intraocular pressure of the subject eye can be measured by the intraocular pressure measuring means; and A non-contact tonometer, comprising: abnormality detection means for detecting whether the operation of the fluid emission means is abnormal. 2. A non-contact tonometer according to claim 1, wherein an error is displayed when an abnormality is detected by said abnormality detecting means.