JPH0397435A - Ophthalmology measuring device - 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 ophthalmological measuring device, and particularly to a device for measuring the ocular refractive power and corneal shape of an eye to be examined.

[Conventional technology] Conventionally, in a device that measures both eye refractive power and corneal shape,
An index for measuring eye refractive power and an index for measuring corneal shape were provided separately.

As corneal shape measurement indicators, ring-shaped indicators are known that are arranged continuously or discretely on the same circumference around the optical axis.

[Problems to be Solved by the Invention] In corneal shape measurement using the conventional ring-shaped index mentioned above, the corneal reflection image of the index is generally elliptical. The short axis and rotation angle were also measured.

However, even if the cornea has irregular astigmatism in which the center of the ellipse is off the optical axis, it cannot be distinguished from cases of astigmatism in which the center of the ellipse is on the optical axis and has the same elliptical shape, making it impossible to determine whether the cornea is irregularly astigmatic. .

Even in the case of irregular astigmatism, the corneal shape is forcibly calculated from a general elliptical shape, resulting in a problem of low measurement reliability.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus that solves the problems of the prior art described above.

[Means for Solving the Problem] In order to achieve the above object, the present invention provides a first index at a position substantially on the optical axis projected onto the fundus of the eye to be examined, and a position around the optical axis projected onto the cornea of the eye to be examined. a second index, a first measuring means for measuring the ocular refractive power of the eye to be examined by receiving the fundus reflected image light of the first index, and a first measuring means that receives the corneal reflected image light of the first index and the second index. The present invention is characterized in that it has a second measuring means for measuring the corneal shape of the eye to be examined.

[Example] FIG. 1 is a diagram showing an example of the present invention. In eye refractive power measurement, light emitted from a light source 1 illuminates an eye refractive power measurement index 3 using a condensing lens 2. The light passes through the light splitting mirror 7.8 and is projected onto the fundus of the subject's eye via the objective lens 9. Further, the image reflected by the fundus of the eye refractive power measurement index 3 passes through the objective lens 9, the light splitting mirror 8.7, is reflected by the perforated mirror 6, and is transmitted through the apertures 10a to 10f of the multi-hole aperture diaphragm 10. It is separated by a relay lens 11 and prisms 12a to 12f, reflected by a mirror 13, and transmitted through cylindrical lenses 14a to 14c to one-dimensional position detection elements 15a to 15 such as one-dimensional CCDs.
The image is formed on c. Note that the cylindrical lens 14a~
14c has power in a direction perpendicular to the detection direction of the one-dimensional position detecting elements 15a to 15c, and focuses light in that direction onto the corresponding one-dimensional position detecting element.

Here, the eye refractive power measurement index 3 has a shape as shown in FIG. 2, and its center O is placed on the optical axis. The reflected image of the eye refractive power measuring index 3 on the fundus is shown in FIG.
It is separated into 6 pieces via 10f. If the fundus of the examinee's eye and the position detection element 15 are conjugate, six separated images are originally superimposed on the optical axis, but due to the presence of the prisms 12a to 12f, the six separated images are superimposed on the optical axis.
It is considered to be a separate image of individuals. Therefore, one-dimensional position detection element 1 5
The eye refractive power is determined from the interval between 3a3a'' (the same applies hereinafter) appearing in the signals a to 15c.

On the other hand, for corneal topography measurement, four
Two fingers 1jJ20a to 20d and an index 3 for measuring eye refractive power are used. The light emitted from the indices 20a to 20d is reflected by the cornea, passes through the objective lens 9, is reflected by the light splitting mirror 8, is imaged once by the relay lens 21, is reflected by the light splitting main mirror 22, and is transmitted to the field lens 23 and mirror 24.
are transmitted and reflected respectively, and pass through the relay lens 25 to the aperture 2.
6. Two-dimensional image sensor ゜28 through the light combining mirror 27
The image will be re-imaged on top. The diaphragm 26 is located at a position such that the magnification of the indicators 20a to 20d remains unchanged even if the working distance between the device and the eye to be examined changes, that is, the indicator 20 (in the eye to be examined) when the working distance is appropriate and when the working distance is inappropriate. The chief ray connecting the corneal reflection images (virtual images) 20a to 20d) is arranged at a position intersecting the optical axis through the optical system. Here, the corneal reflection image of the index 3 for measuring eye refractive power is also imaged on the image sensor 28 via the optical system, and FIG. This shows the corneal reflection image above. Each reflected image is indicated with °.

Now, since the eye refractive power measuring index 3 always emerges from above the optical glaze, if the corneal shape measuring indexes 20a to 20d are arranged symmetrically about the optical axis, the corneal reflection images 20a' to 20d
′, the corneal reflection image 3′ is considered to be its geometric center. Since the cornea is generally a toric surface, the corneal reflection image for such a subject is such that images 20a' to 20d' are arranged on a certain ellipse centered on image 3'.

On the other hand, an ellipse can be determined by finding three points with respect to a certain center, so images 20a to 20d with the center of image 3' as the origin
An ellipse can be determined by finding the position coordinates of three points in '.

Here, each image 20a is set from the origin to the center of the image 3'.
By comparing the distances of ~20d', the presence or absence of irregular astigmatism can be detected. In addition, when determining the ellipse, for example, images 20a, 20
The ellipse and image 20b', 2 obtained from the pair of b', 20c
00 and 20d' are compared, and if their shapes are not significantly different, the average value is displayed, and if they are significantly different, it is assumed that the ellipses have deviated from the toric plane, and an irregular astigmatism mark is displayed to indicate the shape abnormality. It is possible to display information such as informing the examiner. Note that even if the images 20a' cannot be detected because the eyelids are closed, the images 20b',
It is clear that it is possible to display measured values using 20c', 20d'.

As a modification, even if the indices 20a to 20d are not arranged symmetrically about the optical axis, the same result can be achieved by calibrating the positions of the images 20a' to 20d' using a spherical surface or the like with a known curvature in advance. things are possible.

By the way, in FIG. 1, in addition to the two measurement threads mentioned above, the corneal shape is separated from the corneal shape measurement optical system by the light splitting mirror 22, imaged by the field lens 30, mirror 31, relay lens 12, and then reconstituted by the light combining mirror 27 to measure the corneal shape. An anterior eye observation optical system that is combined with the measurement optical system is available. Furthermore, a fixation target optical system for fixating the subject during corneal shape measurement and eye refractive power measurement is shown, which specifically includes an illumination light source 43, a fixation target movable in the optical axis direction, Mark 42, Ri L, -
It consists of an L/lens 41, light splitting mirrors 7 and 8, and an objective lens 9.

[Modification] By the way, in FIG. 1, the center of the eye refractive power measuring index 3 is located on the optical axis, but even if the center is apparently off the optical axis, the same applies to the indexes 20a to 20d as described above. If you calibrate in advance using a spherical surface with a known curvature, there will be no problem.

That is, even in this case, in the present invention, it is considered that the center of the eye refractive power measurement index is substantially on the optical axis. In the example shown in FIG. 1, three dimensional position detection elements were used to measure the eye refractive power, but these may also be two-dimensional imaging elements.
may also be used by the image sensor 28 using a detour optical path. Alternatively, the conjugate position of the fundus may be determined from the light amount balance by moving the optical system.

In addition, an index for measuring eye refractive power 3, an index for measuring corneal shape 20
(20a to 20d) are not limited to the above-mentioned shapes, and may both have a ring shape, for example.

[Effects of the Invention] As explained above, according to the present invention, irregular astigmatism of the cornea can be corrected by determining the corneal shape from the corneal reflection image of a predetermined index for eye refractive power measurement and the corneal reflection image of a corneal shape measurement index. It is possible to provide an ophthalmological measuring device that can determine the presence or absence of the corneal shape and has a corneal shape measuring function with higher precision without particularly using a new index for measuring the center position.

[Brief Description of the Drawings] Fig. 1 is a diagram of an embodiment of the present invention, Fig. 2 is a diagram of a specific example of an index for measuring eye refractive power, Fig. 3 is an enlarged view of the aperture 10, and Fig. 4 is a diagram of a specific example of an index for measuring eye refractive power. FIG. 5 is a diagram showing a specific example of a corneal shape measurement index; FIG. 6 is a diagram showing a corneal reflection image on an imaging means; 3 in the figure indicates the eye refractive power. Measurement indicators (also serve as corneal shape measurement indicators) 15a to 15c are one-dimensional optical position detection elements 20a to 20d
The corneal shape measurement index 28 and the image sensor 42 are fixation targets.

Claims (1)

[Scope of Claims] A first indicator projected onto the fundus of the subject's eye at a position substantially on the optical axis; a second indicator projected onto the cornea of the subject's eye at a position around the optical axis; and a fundus reflection of the first indicator. a first measurement means for measuring the ocular refractive power of the eye to be examined by receiving image light; and a second measurement for measuring the corneal shape of the eye to be examined by receiving the corneal reflected image light of the first index and the second index. An ophthalmological measuring device characterized in that it has means.