JPH01192331A - Eye pressure measuring instrument - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an intraocular pressure measuring device, particularly an intraocular pressure measuring device that measures intraocular pressure by injecting fluid onto the corneal surface and measuring the time until corneal applanation. It is related to.

[Prior Art] The inside of the human eyeball has a positive pressure of about 15 mmHg, and its shape is maintained by this intraocular pressure. A condition in which the intraocular pressure rises above the normal range is a disease called intraocular disease. A tonometer is used to diagnose endometriosis.

The well-known Shetz tonometer applies a constant pressure to the cornea and measures the distance that the cornea is displaced by this pressure. There are problems with this method, such as causing pain to the subject and risk of infection because the instrument directly contacts the cornea.Recently, several tonometers that perform non-contact measurements have become known.

2'gJ shows the structure of a conventional non-contact type intraocular pressure measuring device. In Fig. 0, reference numeral 11 indicates the eye to be examined.
A fluid, such as an air flow, generated by a constant pressure is applied to the center of the cornea 11a of the eye 11 to be examined through the fluid nozzle 13.
The intraocular pressure is calculated from the time it takes for the cornea 11a to deform into a flat surface.

Whether or not the cornea 11a has been applanated can be determined by a light source 3 such as an LED.
a light receiving element 33 that receives light from 1 through a lens 32;
The determination is made based on the maximum amount of light received. light source 31,
A measuring optical system consisting of a lens 32 and a light receiving element 33 is incorporated into the apparatus in a predetermined positional relationship with a 7-line optical system, which will be described later, so that the angle of incidence and angle of reflection on the applanated corneal surface are equal.

Optical elements sandwiched by the measurement optical system 40 and arranged on the optical axis 50a directly facing the eye 11 to be examined constitute an alignment optical system 50. The alignment detection optical system 50 is used to position the measurement optical system 40 with respect to the eye 11 to be examined at a predetermined operating position where the above-mentioned reflection occurs during corneal applanation.

FIG. 2 shows this operating position, that is, the eye 11 to be examined and the device are arranged in a predetermined positional relationship.

On the optical axis 50a of the alignment detection optical system 50, an objective lens 12 and a half mirror 34 are arranged from the side closer to the eye 11 to be examined.
, a relay lens 14, and an observation optical system 15 are arranged. A fluid nozzle 13 is provided at the center of the fluid nozzle 13 . The observation optical system 15 is composed of an eyepiece in a method in which the examiner directly observes the alignment state, but it is composed of an eyepiece.
An imaging system using a sensor or the like may be used.

The following configuration is provided to detect that the relative position of the eye 11 and the device is set to the illustrated operating position.

A tilted half mirror 35 is disposed on the optical axis bent by the half mirror 34.

A light source 38 and an alignment index 37 are arranged behind the half mirror 35. Further, a light receiving element 36 is arranged on the reflection optical axis of the half mirror 35.

The alignment mark 37 is aligned with the cornea 1 in a predetermined operating position.
It is arranged at a position conjugate with the center of curvature Q of 1a. The light receiving element 36 corresponds to the arrangement position of the alignment mark 37 and the half mirror.
It is conjugate to 35.

Furthermore, the image plane of the aforementioned observation optical system 15 is conjugate with respect to the main optical system of the alignment detection optical system 50 including the relay lens 14 with respect to the center of curvature Q of the cornea 11a.

According to such a configuration, during alignment prior to measurement, light is irradiated by the light receiving element 36 via the alignment index 37 and reflected by the cornea, and enters the light receiving element 36 and the observation optical system 15.

The position of the subject [11] is determined in advance by a chin rest (not shown) that positions the face of the subject, and the applanation measurement optical system 40 and alignment detection optical system 50, which are connected in a predetermined positional relationship, are The operating position is determined by moving in three dimensions via the illustrated movable mechanism.

When moving the applanation measurement optical system 40 and the alignment detection optical system 50, if the image of the alignment index 37 is correctly formed through the observation optical system 15 and the amount of light received by the light receiving element 36 is the maximum, the eye 11 and Correct positioning of the device is detected.

Once the operating position is determined, air is injected from the fluid nozzle 13 at a constant pressure by operating a predetermined switch, and at the same time a timer circuit is started. When the cornea is applanated, the light from the light source 31 is best reflected in the direction of the light receiving element 33, so that the amount of light received by the light receiving element 33 reaches a predetermined maximum value.

Therefore, by stopping the timer circuit when the amount of light received by the light receiving element 33 reaches the maximum, the time until corneal applanation is measured, and this time value is used to refer to a table prepared in a ROM or the like. This allows you to know the intraocular pressure value.

[Problems to be Solved by the Invention] However, the conventional device as described above has the following problems.

First, the applanation measurement optical system 40 and the alignment detection optical system 5
Since the optical axes of 0 and 0 are different and the applanation measurement optical system 40 is arranged to sandwich the alignment detection optical system 50, these must be mutually positioned with a predetermined precision and incorporated into the apparatus. The positioning structure of the optical system becomes complicated, which increases manufacturing costs and makes it difficult to miniaturize the device.

The alignment detection optical system 50 is configured to detect the operating position when the center of the cornea 11a is positioned at a predetermined conjugate position. Therefore, as shown by the broken line in FIG. 2, the light beam of the seven-line detection optical system 50 crosses the periphery of the cornea 11a. cornea 11a
There are individual differences in the curvature of the cornea, and the error is particularly large in the peripheral area of the cornea. Therefore, with the optical system arrangement as shown, even if the working position is detected, the actual working distance will be affected by this corneal curvature error. Therefore, it is difficult to reduce the intraocular pressure measurement error caused by the fluid pressure error beyond a certain level.

An object of the present invention is to solve the above problems and provide an intraocular pressure measuring device that is small and lightweight, can be manufactured at low cost, and has good measurement accuracy.

C Means for Solving the Problems] In order to solve the above problems, the present invention provides an intraocular pressure measuring device that measures intraocular pressure by injecting fluid onto the corneal surface and measuring the time until corneal applanation. an optically configured applanation measuring means for detecting that the corneal surface has reached a predetermined applanation state by detecting a reflection state on the corneal surface of the eye to be examined; A configuration was adopted in which optically configured alignment detection means for detecting that the eye to be examined is positioned at a predetermined operating position share the same optical system.

[Function] According to the above configuration, since the applanation measuring means and the 7-line detection means share the same optical system, the light f of the optical system
The number of dl and the number of mathematical optical elements can be reduced.

[Example] The present invention will be described in detail below based on an example shown in one drawing.

FIG. 1 shows the structure of an intraocular pressure measuring device employing the present invention.9 In this embodiment, the applanation measurement system and alignment detection system of the device share the same main optical system 60.

The main optical axis 60a of the main optical system 60 is arranged to directly face the eye 11 in the operating position. An objective lens 12, a relay lens 14, a half mirror 22, and an observation optical system 15 are arranged on the main optical axis 60a from the side closest to the eye 11 to be examined.

A fluid nozzle 13 is provided at the center of the objective lens 12 as in the conventional structure. The fluid (for example, air) is ejected from the fluid nozzle 13 by operating a switch 24 . At the same time, this switch 24 acts to start a timer circuit 23 that measures the time until corneal applanation is detected. The timer circuit 23 is stopped depending on the amount of light received by the light receiving element 19 of the measurement system, which will be described later.

The observation optical system 15 similarly consists of an imaging system such as an eyepiece or a CCD sensor.

Light sources 16 for 7-line detection are placed equidistantly across the optical axis 60b bent by the half mirror 22.
17 are placed. The light from light sources 16 and 17 is a half mirror.
22 is irradiated in the direction of the eye 11 through the pinhole 21 arranged at a position conjugate with the imaging center P2 of the observation optical system 15.

Further, a light source 18 and a light receiving element 19 (measuring system) for detecting applanation of the cornea 11a are arranged behind the light sources 16 and 17 at equidistant positions across the optical axis 60b. light source 18,
The position F3 of the light receiving element 19 on the optical axis 60b is conjugate with the rear focal point F2 of the objective lens 12 with respect to the relay lens 14 and the half mirror 22.

In the above configuration, the operating position of the device is the objective lens 12.
It is assumed that the front focus of is coincident with the vertex r1 of the angle $11a.

The light from the light sources 16.17 passes through the pinholes 21. half mirror 2
2. The eye 11 is irradiated via the relay lens 14 and the objective lens 12, and the corneal reflected light flux returns along the same path, passes through the half mirror 22, and enters the observation optical system 15.

The relative position between the device and the eye 11 to be examined is adjusted by a movable adjustment system (not shown) as in the conventional case, but since the pinhole Pi and the imaging center P2 of the observation optical system 15 are conjugate with the half mirror 22, the operation is easy. If the position is not displayed, the observation optical system 15
As a result, two light spots of the light sources 16 and 17 are observed separately.

When the eye to be examined 11 and the device are adjusted to the correct operating position, the parallel light beam irradiated from the light source 16.17 through the pinhole 21 is reflected at the vertex rl of the cornea 11a, that is, at the front focal position of the objective lens 12. , overlap on the imaging plane of the observation optical system 15.

Therefore, when the light spots of the light sources 16 and 17 overlap at their center positions and become one by the observation optical system 15, the optical axis of the eye 11 to be examined and the main optical axis 60a of the main optical system 60 coincide, and the cornea 11a It can be determined that the distance of the objective lens 12 is set at the correct working distance.

When it is determined by observation through the observation optical system 15 that one operating position has been determined, the examiner operates the switch 24 to cause the fluid nozzle 13 to eject fluid (for example, an air stream). The pressure of this fluid is previously adjusted to a predetermined value. The timer circuit 23 is started at the same time as the fluid nozzle 13 ejects the fluid.

After fluid injection, when the cornea is applanated, the parallel light beam incident from the light source 18 through the pinhole 20 is reflected by the applanation plane AI, and the energy returned to the light receiving element 19 becomes maximum.

This applanation timing is determined by comparing the received light amount signal of the light receiving element 19 with a predetermined threshold value, or by detecting the peak value of the received light amount signal, and by stopping the timer circuit 23, the time until corneal applanation is measured. can. Based on this time value, the intraocular pressure can be calculated by referring to the ROM table as described above.

According to the above configuration, since the alignment detection system and the corneal applanation measurement system share the same main optical system 60, the number of optical systems and the number of elements thereof can be reduced, and positioning of the optical system can be made very easy.

Therefore, the configuration of the device can be significantly simplified and manufacturing costs can be reduced.

Further, as is clear from the comparison with the conventional structure shown in FIG. 2, by sharing the optical system, the volume occupied by the optical system can be reduced, so that a compact and lightweight intraocular pressure measuring device can be provided.

Furthermore, in the embodiment described above, when the corneal apex r1 coincides with the front focus of the objective lens 12, seven alignments to the predetermined operating position are detected.

Therefore, the reflected light at the center of the cornea, where individual differences in corneal curvature are small, is used for 7-alignment detection, and errors in the alignment position can be reduced, and the accuracy of intraocular pressure measurement can be significantly improved.

In the above embodiment, the alignment state is determined by observation through the observation optical system 15, but a light receiving element is provided at the imaging center P2 of the observation optical system 15, and the output of this light receiving element is used to control the fluid injection and the timer circuit. It is also possible to automate the measurement process by having the system perform a start.

[Effects of the Invention] As is clear from the above, according to the present invention, in an intraocular pressure measuring device that measures intraocular pressure by injecting fluid onto the corneal surface and measuring the time until corneal applanation, an optically configured applanation measuring means for detecting that the corneal surface is in a predetermined applanation state by detecting a reflection state on the corneal surface; Since the optically configured alignment detection means for detecting that the alignment has been positioned at the operating position shares the same optical system, the applanation measurement means and the 7-alignment detection means share the same optical system. Because they are shared, the number of optical axes and optical elements in the optical system can be reduced, which has the excellent effect of simplifying the configuration of the device and reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the structure of an intraocular pressure measuring device employing the present invention, and FIG. 2 is an explanatory diagram showing the structure of a conventional intraocular pressure measuring device. 11...Eye to be examined 11a...Cornea 12...
objective lens

Claims (1)

[Claims] 1) In an intraocular pressure measuring device that measures intraocular pressure by injecting fluid onto the corneal surface and measuring the time until corneal applanation,
An optically configured applanation measuring means for detecting that the corneal surface has reached a predetermined applanation state by detecting a reflection state on the corneal surface of the eye to be examined; the applanation measuring means and the eye to be examined; 1. An intraocular pressure measuring device characterized in that optically configured alignment detection means for detecting that the device is positioned at a predetermined operating position share the same optical system.