JPS6392328A - Tonometer - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Field of Application of Industry-I-] The present invention deforms the cornea by blowing air onto the eye to be examined,
The present invention relates to a so-called non-contact tonometer that measures intraocular pressure by detecting the deformation.

[Prior Art] In conventional tonometers of this type, when aligning with the eye to be examined, the alignment index is projected onto the center of curvature of the cornea, so only the reflected image is visible, and the eye to be examined and the device If the axis of the lens is misaligned, alignment is extremely difficult because the corneal reflection image is out of the field of view and cannot be seen.

However, in the conventional tonometer, a virtual image of the corneal reflection is formed at the center of curvature C of the cornea Ec, as shown in FIG. 6(a). Therefore, as shown in (b), when the axis B of the apparatus is shifted by δ with respect to the axis A of the eye E, the movement pressure # of the corneal reflection image is
l:D1 is approximately 26.

The distance from the apex of the cornea Ec to the center of curvature C is approximately 7.7 mm in a normal case, and the apparent distance from the apex of the cornea Ec to the iris surface is approximately 3 mm.

[Purpose of the Invention] In order to improve such drawbacks, the purpose of the present invention is to make the anterior segment of the eye such as the iris visible together with the corneal reflection image, and to prevent the corneal reflection image from disappearing from the field of vision even when axis deviation occurs. To provide a tonometer that does not come off and can be easily aligned.

[Summary of the Invention] The gist of the present invention for achieving the above-mentioned object is to provide a tonometer that measures intraocular pressure by blowing air onto the cornea of an eye to be examined through a nozzle in an air compression chamber and detecting corneal deformation. This tonometer is characterized in that a light source is arranged so that a virtual reflected image is formed near the iris surface of the eye to be examined.

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

FIG. 1 shows a first embodiment of the present invention, in which air compressed by a piston or the like is blown onto the eye E through a nozzle in an air compression chamber to deform the cornea Ec, and the deformation of the cornea Ec is optically measured. It is well known that the intraocular pressure is measured by detecting the intraocular pressure, and the illustration of the airflow generator and the measurement detection unit is omitted.

A nozzle 2 is provided at the center of the objective lens 1, and an alignment light source 3 consisting of a light emitting diode, a lamp, etc. is installed around the objective lens 1, and a virtual image of the corneal reflection image P of the alignment light source 3 is installed. When the distance between the alignment light source 3 and the vertex of the cornea Ec is approximately 11 to 12 mm,
It is formed approximately 3 mm from the apex of the cornea Ec. A lens 4 and an observation surface 5 are provided behind the objective lens 1, and the iris Ei and the corneal reflection image P are set in a conjugate relationship with the observation surface 5 by the objective lens 1 and the lens 4. The virtual image of the corneal reflection image P corresponds to the apparent upper position of the iris Ei of a normal eye from the vertex of the cornea Ec, and the iris Ei is also visible along with the corneal reflection image P on the observation surface 5 through the lens 4. .

FIG. 2 shows an example of the visual field image on the observation surface 5. A mark 6 is displayed on the observation surface 5. If the corneal reflection image P is focused on this mark, alignment is completed and the measurement is completed. become possible.

In the case of this example, for the axis misalignment between the eye E and the device,
Since the moving distance of the corneal reflection image P is about half that of the conventional one, the corneal reflection image is unlikely to disappear from the observation field of view even if there is some axis deviation. The reason for this will be explained below with reference to FIG.

As shown in FIG. 3(a), since the corneal reflection image P of the alignment light source 3 is formed near the iris surface Ei of the eye E, the axis A of the eye E is shown in FIG. 3(b). On the other hand, when the axis B of the apparatus is shifted by a distance δ, the movement distance D2 of the corneal reflection image P is also approximately the same as δ.

FIG. 4 shows a second embodiment, in which objective lens 1 and lens 4
A light splitting member 7 is placed between them, and a lens 8 is placed on the reflection side of the light splitting member 7.
A light source 9 is provided. Note that in FIG. 4, the same reference numerals as in FIG. 1 represent the same or equivalent members.

The image Q1 of the alignment light source 9 is formed by the lens 8 through the light splitting member 7 in the vicinity of the center hole 2 of the objective lens 1, and the virtual corneal reflection image Q2 is formed in the vicinity of the iris surface Ei of the eye E to be examined. is formed. In this embodiment, since the image is formed on the optical axis, the mark 6 displayed on the observation surface 5 is also brought to the center.

Furthermore, in this case, it is necessary to separately provide a light source that illuminates the entire external eye.

A third embodiment is shown in FIG. 5, in which the measurement light source 9 also serves as a positioning light source. An optical member 10 made of flat glass and having a nozzle 2 is arranged corresponding to an objective lens, and a lens 11 is provided behind it. Further, a second light splitting member 12 is arranged behind the light splitting member 7, and a television camera 13 is provided on the reflection side thereof, and the output of this television camera 13 is connected to a monitor 14.

The light beam from the light source 9 passes through the lens 8. Light splitting member 7, lens 1
1. Projected onto the eye E through the nozzle 2. Corneal Ec
When a light source image Q3 is formed near the iris surface by reflection, this is imaged by the television camera 13 via the optical member 10, the lens 11, and the light splitting member 7.12, and the extraocular image is displayed on the monitor 14. Alignment is performed by bringing the corneal reflection image P to a predetermined position on the monitor 14, air is blown onto the cornea Ec from the nozzle 2, and when the cornea Ec is deformed to a certain curvature, the amount of light incident on the observation surface 5 is determined. maximum,
Intraocular pressure can be determined from the timing at that time.

[Advantageous Effects of the Invention 1] As explained above, the tonometer according to the present invention allows the outer eye part of the subject's eye to be observed together with the corneal reflection image of the positioning light source, so even if the external ocular part of the subject's eye is reflected due to the deviation of the eye from the subject's eye. Even if the light does not fall within the field of view, it is possible to determine in which direction it is out. In addition, because the corneal reflection image is less likely to disappear from the observation field due to axis misalignment,
Alignment I: There is an advantage that the operation is significantly easier.

[Brief explanation of the drawing]

Figure 1 is an optical layout diagram of the first embodiment of the tonometer according to the present invention, Figure 2 is an explanatory diagram of its observation field image, Figure 3 is an explanatory diagram of its operation, and Figure 4 is an illustration of the second embodiment. FIG. 5 is an optical layout diagram of the third embodiment, and FIG. 6 is an explanatory diagram of the operation of the conventional example. 1 is an objective lens, 2 is a nozzle, 3.9 is a light source for alignment, 5 is an observation surface, 6 is a mark, 7.12 is a light splitting member, 10 is an optical member, 13 is a television camera, and 14 is a monitor It is. Patent applicant Canon Co., Ltd. Figure 4 Figure 6 (G) (b)

Claims (1)

[Claims] 1. In a tonometer that measures intraocular pressure by blowing air onto the cornea of the subject's eye through a nozzle in the air compression chamber and detecting the deformation of the cornea, a virtual image of the corneal reflection image is formed near the iris surface of the subject's eye. A tonometer characterized by a light source.