JPH01300931A - Tonometer - Google Patents

Abstract

PURPOSE:To measure an accurate intraocular pressure value without deforming the cornea until the surface thereof becomes flat, by measuring intraocular pressure on the basis of the pressure of a fluid when the cornea is deformed to a predetermined degree before reaching an applanation state. CONSTITUTION:An index light source 1 and a projection lens 2 are arranged in the oblique direction of an eye E to be examined, and a light receiving lens 3 and a photodetector 4 are arranged in the oblique direction of said eye on the opposite side. The luminous flux from the index light source 1 is allowed to irradiate the cornea Ec in the direction oblique with respect to the jet direction of the air stream from a nozzle 7. When the cornea Ec receives predetermined deformation by the air stream, the reflected light due to the cornea Ec enters the photodetector 4 arranged so as to become the conjugated relation to the index light source 1 through the lens 3 to detect the deformation of the cornea Ec. The air pressure when the cornea generates predetermined deformation is measured by the pressure sensor 8 in a cylinder 5 to calculate an intraocular pressure value.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a non-contact tonometer used in ophthalmology, etc., which measures intraocular pressure by injecting airflow onto the cornea and deforming the cornea. It is something.

[Prior art 1] In recent years, when measuring intraocular pressure, the intraocular pressure has been measured without contacting the eye to be examined.
A tonometer is used to determine intraocular pressure, in which the cornea is applanated by injecting airflow to the cornea, and the intraocular pressure is measured from the air pressure at that time. However, deforming the cornea until it is sufficiently applanated causes strong discomfort to the patient and at the same time, the degree of deformation is large, so the restoring power of the cornea is affected not only by intraocular pressure but also by the elasticity of the cornea itself. There is a risk of receiving

Therefore, it is possible to measure the intraocular pressure at a predetermined degree of deformation before the cornea becomes flat, but in the conventional method, the direction of the airflow and the direction of the measurement light beam are the same, so the airflow If the injection nozzle is present in the path of the light and the index light is reflected spherically without applanating the cornea, it will be difficult to design the optical system.

[Objective of the Invention] The object of the present invention is to provide accurate intraocular pressure values without causing discomfort to the subject and without deforming the corneal surface until it becomes flat when measuring intraocular pressure in a non-contact manner. The objective is to provide a tonometer that can measure

[Summary of the Invention] The gist of the present invention to achieve the above-mentioned object is to provide a tonometer that deforms the cornea by blowing airflow and optically detects the deformation to measure intraocular pressure. is irradiated onto the cornea from an oblique direction with respect to the jetting direction of the airflow, and when the cornea undergoes a predetermined deformation due to the airflow, a light-receiving element installed so that the light reflected by the cornea becomes conjugate with the light source via a lens is used to detect the cornea. This is a tonometer characterized by detecting deformation of the tonometer.

[Embodiments of the invention] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a configuration diagram of a tonometer, in which an index light source 1 consisting of an LED or the like and a light projecting lens 2 are arranged diagonally toward the eye E to be examined, and a light receiving lens 3 and a light receiving element 4 are arranged diagonally on the opposite side. is located. In addition, a cylinder 5 is placed in front of the eye E to be examined.
is arranged, and the cornea Ec of the eye E to be examined is placed in front of the cylinder 5.
A nozzle 7 is provided toward the cylinder 5, and a piston 6
It is designed to compress air. Further, the cylinder 5 has a built-in pressure sensor 8 for measuring internal pressure.

The light beam emitted from the index light source 1 becomes a condensed light beam Ll by the projection lens 2 and is irradiated onto the center of the cornea Ec, causing spherical reflection on the cornea Ec and becoming a diffused light beam L2. here,
The piston 6 in the cylinder 5 is moved to inject an air stream from the nozzle 7 toward the cornea Ec, the diffused light beam L2 is focused by the light receiving lens 3, and the light amount is detected by the light receiving element 4. In this optical system, the light source 1 and the light-receiving element 4 are moved to a conjugate position via the lens 2.3 at a predetermined time of deformation, during the process in which the cornea Ec is deformed by the air flow and the curvature is relaxed. It is arranged in In the case of such an optical system, it is preferable that the corneal reflection be the same magnification and that the convergence and divergence of the luminous flux be equal, but the principle does not change even if it is not the same magnification.

FIG. 2(a) shows the image of the light source 1, and (b) and (C) show the image of the diffused light flux L2 on the light receiving element 4, but the light source 1 and the light receiving element 4 are of the same shape, and b) is corneal Ec
(C) shows a case where the cornea Ec is deformed and the light source 1 and the light-receiving element 4 are in a conjugate position. If the -conjugate relationship does not hold, the image of the diffused light beam L2 becomes blurred and the conjugate holds. When the cornea Ec undergoes a predetermined deformation, the entire image is incident within the plane of the light receiving element 4, the output of the light receiving element 4 becomes maximum, and it is possible to detect the point in time when the predetermined deformation occurs using this signal. becomes.

Therefore, by measuring the air pressure when a predetermined deformation occurs with the pressure sensor 8 in the cylinder 5, the intraocular pressure value is measured from the deformation value of the cornea Ec and the air pressure in the cylinder 5 obtained by the pressure sensor 8. .

Note that a compressor may be used as a means for generating the air flow, and it is also possible to calculate the pressure from the speed, position, and time of the piston 6 instead of the pressure sensor 8.

FIG. 3 shows, as another embodiment of the method for detecting a predetermined deformation, a light receiving section 40 consisting of an index light source 10 having a different shape and three light receiving elements 40a, 40b, 4OC. ) is the index light source 10° (b) is the light receiving element 40a,
40b and 40c, the light source 10 is rectangular, and the element 4
Oa, 40b.

In 40C, rectangular elements of the same shape are arranged in parallel in a direction orthogonal to the optical axis. At the time of predetermined deformation, the central element 40b and the light source 10 become conjugate, and before the deformation, the image of the reflected light beam L2 from the light source 10 is blurred, and light also enters the elements 40a and 40b on both sides. Therefore, three elements 40a, 40b,
Letting the output signals of 40c be St, S2, and S3, the overall output signal S is S = S2/(St + 93)
In this case, the maximum value of the signal S becomes more remarkable than in the case of one light receiving element, and it becomes easier to determine when a predetermined deformation occurs.

[Effects of the Invention] As explained above, the tonometer according to the present invention measures intraocular pressure based on the fluid pressure at a predetermined deformation before the cornea is applanated, so the deformation of the cornea can be reduced. Not only can the subject's discomfort be reduced, but also the influence of the elasticity of the cornea itself can be reduced, allowing for more accurate measurements. Furthermore, since the light beam is emitted from a direction different from the direction in which the airflow is ejected, the path of the light is not obstructed by the airflow injection nozzle.

[Brief explanation of the drawing]

The drawings show an embodiment of the tonometer 1 according to the present invention, and FIG. 1 is a configuration diagram of the tonometer, and FIG.
(b) and (c) are explanatory diagrams of the light source image and the light receiving element, the third
Figure (a) is a front view of a light source in another embodiment, and Figure (b) is an explanatory diagram of a light receiving element. Code 1, lO is the index light source, 2.3 is the lens, 4.40a
, 40b, 40e are light receiving elements, 5 is a cylinder, 6 is a piston, 7 is a nozzle, and 8 is a pressure sensor. Patent applicant Canon Co., Ltd. Figure 1 14/ Figure 3

Claims (1)

[Claims] 1. In a tonometer that deforms the cornea by blowing airflow and optically detects the deformation to measure intraocular pressure, a light beam from a light source is irradiated onto the cornea from an oblique direction with respect to the direction of the airflow, and the cornea is A tonometer characterized in that, when the cornea undergoes a predetermined deformation due to airflow, the deformation of the cornea is detected by a light-receiving element installed so that the light reflected by the cornea becomes conjugate with the light source through a lens.