JP2786692B2 - Non-contact tonometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention aims to eliminate the discomfort and burden on a subject caused by discharging a fluid having an excessive discharge pressure toward a cornea. The present invention relates to a non-contact tonometer that can be used.

(Prior art) Conventionally, a non-contact tonometer has been known in which a cornea is applanated to measure an intraocular pressure by operating a rotary solenoid to move a piston and discharge a fluid from a nozzle. ing.

(Problems to be Solved by the Invention) However, in this device, energization of the rotary solenoid is stopped at the time of applanation of the eye to be inspected. However, since the piston rises due to inertia, it is more than necessary after the applanation detection is completed. The fluid under pressure is released toward the cornea, which causes a problem that the burden on the subject is large and that the subject is uncomfortable. In particular, there is a problem that infants are scared because of the burden of the pressure.

Therefore, an object of the present invention is to provide a non-contact tonometer capable of relieving a subject of discomfort and a burden caused by discharging a fluid having an excessive discharge pressure toward a cornea. It is in.

(Means for Solving the Problems) In order to achieve the above object, a non-contact tonometer according to the present invention discharges a fluid toward a cornea to be examined, applanates the cornea and measures intraocular pressure A non-contact type tonometer, wherein corneal deformability detecting means for detecting corneal deformation easiness from a relationship between the corneal deformation degree before applanation and the time, and a control output of the corneal deformability detecting means. And a drive stopping means for stopping the driving of the fluid discharging means before the corneal applanation.

(Operation) According to the non-contact tonometer according to the present invention, the amount of light received by the alignment light receiver decreases as the fluid is released and the cornea is deformed, and the light reception output decreases. The corneal deformability detection means outputs a control output based on the relative relationship between the degree of decrease in the light receiving output of the alignment light receiver due to the corneal deformation when the fluid is discharged and the time until the cornea undergoes deformation. The drive stopping means stops driving the fluid discharge means before corneal applanation based on the control output.

(Example) Hereinafter, an example of a non-contact tonometer according to the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an observation optical system for observing an anterior segment of the eye E, 2 an index projection system for projecting an index image onto the eye E to detect an alignment state, and 3 an index on the eye E. A light receiving optical system 4 for receiving a corneal specular reflected light beam forming an image, a fixation target projection system 5 for projecting a fixation target to the eye E to be examined,
Reference numeral denotes a detection light projection system that projects the applanation detection light onto the cornea C in order to detect the applanation state of the cornea C. Reference numeral 6 denotes a light receiving optical system that receives the applanation detection light reflected by the cornea C. The light receiving optical system 6 is composed of a telecentric optical system in which a stop is arranged at the focal point of the objective lens, and has a light receiver 7.

The observation optical system 1 includes an objective lens 8, a half mirror 9, an objective lens 10, a half mirror 11, an aiming plate 12, and an eyepiece 13. The optical axes O of the objective lenses 8 and 10 are coaxial with the axis M of the nozzle 14 that emits a fluid toward the cornea C of the eye E to be examined. The eye E is illuminated by an anterior segment illumination light source (not shown), and the objective lens 10 forms an image of the anterior segment of the eye E on the sighting plate 12. The examiner can observe the image of the anterior segment formed on the aiming plate 12 through the eyepiece 13. Note that reference numeral 15
Is the examiner's eye.

The nozzle 14 is held by the objective lens 8 as shown in FIG. 2 and communicates with a chamber 17 of a cylinder device 16 as a fluid discharging means. The chamber 17 is connected to a compression chamber 19. In the compression chamber 19, a piston 20 is provided so as to be able to reciprocate. A piston rod 21 is provided integrally with the piston 20. An arm 23 of a rotary solenoid 22 is connected to the piston rod 21. The rotary solenoid 22 constitutes a part of the fluid discharging means, and when the distance from the tip 14a of the nozzle 14 to the vertex 24 of the cornea C reaches the reference working distance D (when the eye E is properly aligned). When the rotary solenoid 22 is energized, the rotary solenoid 22 is driven and the discharge of the fluid from the nozzle 14 toward the cornea C is started. arm
The arm 23 is rotated clockwise by a rotary solenoid 22. When the energization is stopped, the arm 23 returns to its original position by the spring force of a spring (not shown). External air is sucked into the compression chamber 19 from the nozzle 14 as the piston 20 descends at that time, and the cylinder device 16 waits for the next measurement.

The index projection system 2 includes an infrared light emitting diode 26, a half mirror 27, a reflection mirror 28, a collimator lens 29, a half mirror 9, and an objective lens 8, as shown in FIG. The infrared light beam emitted from the infrared light emitting diode 26 passes through the half mirror 27 and is guided to the reflection mirror 28, is reflected by the reflection mirror 28, and is guided to the collimator lens 29.
The collimator lens 29 guides the infrared light beam as a parallel light beam P to the half mirror 9. The parallel light beam P is reflected by the half mirror 9 toward the cornea C. The objective lens 8 functions to converge the parallel light flux P toward the corneal curvature center R when the apparatus main body is at the reference working distance D with respect to the eye E, and the objective lens 8 is parallel to the corneal curvature center R of the cornea C. An index image is formed based on the corneal specularly reflected light flux of the light flux P.

The light receiving optical system 3 is generally constituted by a half mirror 11, a stop 30, and a light amount sensor 31 as a light receiver for alignment. The aperture 30 and the corneal curvature center R of the eye E have a conjugate relationship with respect to the objective lenses 8 and 10 when the apparatus main body is at the reference working distance D with respect to the eye E. A corneal specularly reflected light beam that forms an index image on the cornea C is converted into a parallel light beam by the objective lens 8 and guided to the half mirror 11 as a convergent light beam by the objective lens 10. Part of the specularly reflected light beam passes through the half mirror 11 and is imaged on the aiming plate 12. The examiner performs alignment of the apparatus main body with respect to the eye E by visually recognizing the index image. The remaining corneal specularly reflected light flux is reflected by the half mirror 11 and guided to the diaphragm 30,
An index image is formed at the position of the stop 30. And the aperture
The corneal specularly reflected light beam that has passed through 30 is received by light amount sensor 31. Axis M of the optical axis L ₂ and the nozzle 14 of the light-receiving output from the optical axis L ₁ of the (detection light projection system 5 when the apparatus main body with respect to the eye E is aligned to the normal light-receiving optical system 6 of the light amount sensor 31 (When the intersection Z with the corneal vertex 24 coincides). The received light output of the light quantity sensor 31 is input to the light quantity detection circuit 32, the details of which will be described later.

The fixation target projection system 4 includes an objective lens 8, a half mirror 9, a turret plate 33, a collimator lens 29, a reflection mirror 28, a half mirror 27, a fixation target 34, and a lamp 35. The collimator lens 29 has a substantially conjugate relationship. A plurality of windows are formed in the turret plate 33, and lenses with different focal lengths are respectively installed in these windows. Even when the subject is hyperopic or myopic, the turret plate 33
Is selectively rotated so that the subject gazes at the in-focus state of the fixation target so that the subject's eye E is in a cloudy vision state.

The light quantity detection circuit 32 outputs an alignment completion signal to the solenoid driving means 34, the timer circuit 36, and the comparison divider 37 when the apparatus body is properly aligned with the eye E. The solenoid driving means 35 drives the rotary solenoid 22 based on the alignment completion signal. The timer circuit 36 starts timing based on the alignment completion signal. The comparison divider 37 stores the light reception output of the light quantity sensor 31 when the alignment completion signal is output. When the cornea C starts to be deformed based on the fluid discharge from the nozzle 14, the index image on the diaphragm 30 is spread and blurred, the amount of light incident on the light amount sensor 31 decreases, and the light receiving output of the light receiving sensor 31 decreases.

When the light receiving output of the light quantity sensor 31 decreases at a constant rate, the comparing circuit 37 outputs a comparing output to the arithmetic circuit. The clock output of the timer circuit 36 is input to the arithmetic circuit 38 every moment, and the arithmetic circuit 38 outputs the comparison output after the fluid discharge is started based on the clock output of the timer circuit 36 at the time when the comparison output is output. Read the time until is input. When the intraocular pressure of the eye E is relatively high, the time from the start of liquid discharge until the cornea C undergoes a predetermined amount of deformation is relatively long, and the intraocular pressure of the eye E is relatively low. Is relatively short from the start of fluid release until the cornea C undergoes a predetermined amount of deformation. On the other hand, the received light output of the light amount sensor 31 at the time of completion of the alignment and the received light output at the time when the cornea C is deformed by a predetermined amount are not constant, but the received light output at the time when the cornea C is deformed by a predetermined amount is completed. The value obtained by dividing the received light output of the light amount sensor 31 at the time can be regarded as a constant. Therefore, the value obtained by dividing the received light output of the light amount sensor 31 when the cornea C is deformed by the light receiving sensor 31 at the time of the alignment completion is a predetermined value. If the value is detected, it can be detected that the cornea C has undergone a predetermined amount of deformation.

Therefore, it is determined in advance by an experiment how long the rotary solenoid 22 must be driven from the time when the cornea C is deformed by a predetermined amount due to the discharge of the fluid to the time when the cornea is applanated. At that time, the control signal is output to the solenoid control circuit 39. When the arithmetic circuit 38 is configured in this manner, the arithmetic circuit 38 cooperates with the timer circuit 36 and the comparative divider 38 based on the degree of decrease in the light reception output of the alignment light receiver caused by the corneal deformation at the time of fluid discharge. It functions as corneal deformability detection means for detecting the ease of deformation.

The solenoid control circuit 39 outputs a solenoid stop signal to the solenoid driving means 35 based on the control signal of the arithmetic circuit 38. Therefore, the solenoid control circuit 39 functions as a drive stop unit that stops driving the fluid discharge unit based on the control output of the corneal deformability detection unit.

The piston 20 rises by inertia even when the driving of the rotary solenoid 22 is stopped. Accordingly, the cornea C is applanated by the rise due to the inertia of the rotary solenoid 22. When the cornea C is applanated, the parallel light flux of the detection light projection system 5
P ₁ is plane-reflected by the cornea C, and the plane reflected light beam is received by the light receiving optical system 6. The applanation of the cornea C is detected by receiving the planar reflected light beam of the light receiving optical system 6, and the intraocular pressure of the eye E is measured based on the time required from the start of fluid discharge to the applanation of the cornea C. Is done. In FIG. 1, reference numeral 40 denotes an infrared light emitting diode, and reference numeral 41 denotes an objective lens which projects the infrared light emitting diode as a parallel light beam toward the applanation cornea.

As described above, in the embodiment, the time until the cornea undergoes a predetermined amount of deformation is obtained based on the degree of decrease in the light reception output of the light amount sensor,
Thus, the ease of corneal deformation is detected, and the solenoid driving means is stopped based on the control output of the corneal deformation easy means. However, the light receiving output of the light amount sensor after a predetermined time has elapsed since the fluid discharge was started. Calculate the degree of decrease in the received light output after a certain period of time has elapsed since the fluid discharge was started by dividing the received light output when the alignment is completed, and detect the ease of corneal deformation and stop driving the solenoid driving means. It may be.

(Effects of the Invention) As described above, the present invention measures the ease of deformation of the subject's eye based on the degree of decrease in the light receiving output of the alignment light receiver due to the corneal deformation at the time of fluid discharge, and Since the discharge of the fluid is stopped before the corneal applanation according to the ease of deformation, the discomfort and burden on the subject caused by discharging the fluid having an excessive discharge pressure toward the cornea Is achieved.

[Brief description of the drawings]

1 is a side view showing an outline of an optical system of a non-contact tonometer according to the present invention, and FIG. 2 is a conceptual diagram of a cylinder device according to the present invention. 2 ... Target projection system, 3, 6 ... Light receiving optical system 14 ... Nozzle 16 ... Cylinder device (fluid discharge means) 31 ... Light amount sensor (light receiving device for alignment) 32 ... Light amount detection circuit, 35 ... Solenoid driving means 36 Timer circuit 37 Comparison division circuit 38 Calculation circuit 39 Solenoid control circuit (driving stop means) C Cornea M M Axis line E Eye to be examined

Claims (1)

(57) [Claims] 1. A non-contact tonometer for measuring an intraocular pressure by applanating the cornea by discharging a fluid toward the cornea to be examined, wherein the degree of deformation of the cornea before the applanation and the time are measured. Corneal deformability detecting means for detecting the easiness of corneal deformation from the relationship, and drive stopping means for stopping driving of the fluid discharge means before corneal applanation based on the control output of the corneal deformability detecting means. Non-contact tonometer characterized by the following.