JPH0580207B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is a non-contact method that deforms the cornea by blowing compressed air onto the eye to be examined, and optically detects the deformed state to measure intraocular pressure. It concerns a tonometer.

[Prior Art] A conventional tonometer is known, for example, the one described in the specification of Utility Model Application No. 58-37294. The most common method is to spray compressed air onto the subject's eye from a nozzle in the center of the lens, and detect when the cornea is applanated by the pressure, but a more accurate detection method is needed. It is being

[Object of the Invention] An object of the present invention is to provide a tonometer that can measure intraocular pressure more accurately.

[Summary of the invention] The gist of the present invention for achieving the above object is as follows:
Compressed air is sprayed from a nozzle onto the cornea of the eye being examined to deform the cornea, and the deformation is optically detected.
In a tonometer that detects a predetermined parameter related to the intraocular pressure of the eye to be examined and calculates the intraocular pressure based on the detection of the deformation and the detection of the predetermined parameter, the cornea is detected in a predetermined deformed state before applanation. , the tonometer is characterized in that the intraocular pressure is determined based on the detection result of the predetermined parameter at the time of the predetermined deformation.

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

FIG. 1 shows an example of a tonometer,
C shows the cornea of the eye to be examined, and compressed air is blown toward the cornea C from a nozzle 2 provided at the center of the objective lens 1 placed in front of the cornea, and the compressed air moves the piston 4 in the cylinder 3 in the direction of arrow A. This is the same as in the conventional example.

Note that the cylinder 3 is provided with a window 5 for passing the light beam of the optical system, behind which a light splitting member 6 and a light receiving element 7 are arranged, and on the reflective side of the light splitting member 6 an index 8 is provided. , a light source 9 are arranged. The output of the light receiving element 7 is transmitted to a change point detection circuit 10,
They are sequentially connected to the intraocular pressure measurement circuit 11.

The light beam from the index 8 illuminated by the light source 9 is reflected by the light splitting member 6, passes through the window 5 and the lens portion 1a around the nozzle 2 of the objective lens 1, and is projected onto the cornea C. When the cornea C is deformed by the compressed air and its curvature increases slightly, the light beam reflected by the cornea C passes through the lens portion 1a of the objective lens 1 again, passes through the window 5 and the light splitting member 6, and forms an image on the light receiving element 7. The light receiving element 7 is arranged so that.

That is, before compressed air is blown, there is no co-projection relationship between the light receiving element 7 and the index 8, and the amount of light incident on the light receiving element 7 is small, but when the cornea C deforms and its curvature becomes slightly larger, the co-projection relationship is established. is established so that the amount of light incident on the light receiving element 7 is maximized, so that the intraocular pressure can be measured based on the air pressure of the compressed air at that time. Regarding this co-projection relationship, since the normal radius of curvature of the cornea C is about 7 to 8 mm, if R is set to about 10 mm, the point at which the cornea C starts to deform can be detected by, for example, a change point detection circuit equipped with a differential circuit. 10, and based on the output thereof, an intraocular pressure measuring circuit 11 enables accurate intraocular pressure measurement from the pressure of the compressed air at that time.

Generally, when compressed air is sprayed, the pressure on the cornea C increases, and when the pressure on the outside of the cornea C becomes higher than the pressure on the inside, the cornea C begins to deform.
If we can determine the point at which this deformation begins, we will be able to measure intraocular pressure more accurately.

In the embodiment shown in FIG. 1, a case has been described in which the image of the index 8 is projected onto the cornea C, but it goes without saying that an image of the light source 9 may be projected instead of the index 8. Further, in the embodiment, the light receiving element 7 and the index 8 are not conjugated with respect to the light splitting member 6, but there is no problem even if they are conjugated. Furthermore, the luminous flux is
An optical system that emits light obliquely to the cornea without passing through the cornea.
A light receiving optical system may be arranged.

[Effects of the Invention] As explained above, the tonometer according to the present invention can measure intraocular pressure more accurately than before because the tonometer can measure the point at which the cornea undergoes a predetermined deformation before applanation. I can do it. It also becomes possible to weaken the spraying pressure required for intraocular pressure measurement.

[Brief explanation of the drawing]

The drawings show an embodiment of the tonometer according to the present invention, and FIG. 1 is an optical layout diagram thereof. 1 is an objective lens, 1a is a lens part, 2 is a nozzle, 3 is a cylinder, 4 is a piston, 5 is a window, 6
1 is a light splitting member, 7 is a light receiving element, 8 is an index, 9 is a light source, 10 is a change point detection circuit, and 11 is an intraocular pressure measurement circuit.

Claims (1)

[Scope of Claims] 1. Compressed air is blown onto the cornea of the eye to be examined from a nozzle to deform the cornea, the deformation is optically detected, a predetermined parameter related to the intraocular pressure of the eye to be examined is detected, and the deformation is performed. In the tonometer that calculates the intraocular pressure based on the detection of the cornea and the detection of the predetermined parameter, the cornea is detected in a predetermined deformed state before applanation, and based on the detection result of the predetermined parameter at the time of the predetermined deformation. A tonometer that measures intraocular pressure. 2. The tonometer according to claim 1, wherein the predetermined parameter is the pressure of compressed air.