JPH02289227A - Ophthalmological 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 for measuring eye refractive power and corneal shape, which has a fixation means that can be controlled to suit each measurement.

[Prior Art] Generally, when performing an eye refraction test, in addition to measuring refractive power, the corneal shape is also measured in order to test for the presence of astigmatism and to test the astigmatism axis and degree of astigmatism. . Conventionally, when performing such an examination, the corneal shape and refractive power were measured separately using different instruments, but the time and effort required for the measurements was costly for both the examiner and the examinee. However, in recent years, devices that can perform both measurements using the same instrument have been manufactured.

By the way, generally when measuring eye refractive power or corneal shape, the subject's eye is fixed on a fixation target provided inside the device, and then a predetermined target is placed on the fundus or cornea of the subject's eye. is projected, the reflected image is received by a detector, and measured values are obtained by analyzing them.

Problem 1 to be Solved by the Invention There are two types of fixation targets for measuring eye refractive power: a slide photograph of a landscape, etc., and a radial pattern.The latter radial pattern is designed to direct the eye to gaze at its center. In devices that measure eye refractive power and corneal shape using the same instrument, one of these fixation targets is installed; Since the measurement results are greatly affected by the examiner's movement, it is necessary to make the examinee's eye gaze at the optotype more firmly and to fix the examinee's eye more reliably. Therefore, if the fixation target for eye refractive power measurement is used as it is when measuring the corneal shape, accurate measurement may be hindered.

When using a slide of a general scene where central fixation is difficult as a common fixation target, the subject may be confused as to where to look on the slide, making it difficult to fixate the subject's eye (due to corneal shape, etc.). It is unsuitable as a fixation target for measurement.Also, when a radial pattern is used as a common fixation target, the center of the pattern is fixed at the position of emmetropia, so a fixation target with this fixation target is not suitable. If the visual means is not changed in any way, in the case of subjects with moderately or severely myopic or farsighted eyes, the pattern will become blurry and they will not be able to gaze, making it difficult to fix the subject's eye. As described above, the conventional example is not fully satisfactory, which causes a decrease in measurement accuracy.

The purpose of the present invention is to significantly reduce measurement time and labor by providing a fixation target that can be controlled to be suitable for measuring both eye refractive power and corneal shape, and to sufficiently fix the eye to be examined. An object of the present invention is to provide an ophthalmological measuring device that enables accurate measurement.

[Means for Solving the Invention] The gist of the present invention for achieving the above-mentioned object is to provide an optical system for measuring the eye refractive power of an eye to be examined, and a part of the optical system sharing the optical system with the optical system for measuring the eye refractive power. a corneal shape measuring optical system; a first fixation means for measuring eye refractive power that includes a two-dimensional fixation target and presents the two-dimensional fixation target to the eye to be examined; and a center located at the center of the visual field; a second fixation means for corneal shape measurement that includes a fixation target and presents the central fixation target to the eye to be examined; and a position adapted to the eye refractive power of the eye to be examined obtained by the eye refractive power measurement optical system. The ophthalmologic measuring device is characterized in that it has a means for adjusting the second fixation means and a means for observing the anterior segment of the eye to be examined.

[Operation] The ophthalmological measuring device having the above-described configuration measures eye refractive power using a two-dimensional fixation target, moves the central fixation target to a position corresponding to the obtained eye refractive power, and measures the corneal shape. Take measurements.

[Example] The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an optical system showing an embodiment of the present invention, in which visible light emitted from a ring-shaped strobe 1 is directed to a collimator ring lens 2 facing the subject's eye E during corneal shape measurement.
A circular slit 3 provided in the slit 3 is illuminated. The slit 3 is located on the focal plane of the ring lens 2 when viewed in a cross section including the optical axis, and the slit 3 is optically located at an infinity point, so that the light projected from that infinity point is illuminated. The cornea Ec of the optometrist E is illuminated. Since the surface of the eye E to be examined is like a convex mirror, a corneal reflection image of the slit 3 is created, and this corneal reflection image reflects only the near-infrared light through the objective lens 4 and rejects light of other wavelengths. It passes through the dichroic mirror 5 and reflects visible light.
The infrared light is reflected upward by the dichroic mirror 6 that transmits the infrared light, and is reflected to the right by the beam splitter 7, and then passed through the multi-hole aperture 8.
The light is deflected by a prism 9 and reimaged onto a one-dimensional position detection element 10 made of a CCD (charge coupled device).

The multi-hole diaphragm 8 has, for example, five openings 8a to 8e, as shown in FIG.
There are five elements 9a to 9e, which are divided by dotted lines, corresponding to 8e, and each of these elements 98 to 9e has a cross-sectional shape as shown in FIG. The five corneal reflection images separated by the multi-hole aperture 8 and the prism 9 are combined at the position of the detection element 10 in the relationship shown in FIG. In this FIG. 3, sb represents a corneal reflected image obtained by forming and separating the image reflected by the cornea Ec by the objective lens 4, and loa to 10e are detection elements, respectively, and apertures 88 to 8e, a prism This corresponds to each of the elements 98 to 9e. by this,
The coordinates of five points in the corneal reflection image sb are detected, and the coefficients are calculated by substituting the coordinates of these five points into the general formula of the quadratic curve, AX" + BXY + CY" + DX + EY + F = 0 and solving the simultaneous equations. Find A to E and use the general formula for an ellipse, (x xol"/a" + (y -yo)2/b
2= Matadashi, x=Xcosθ−Y sinθy=X
sin θ + y cos θ , the major axis a and the minor axis of the ellipse are used to derive the radius of curvature of the bibionic meridian of the cornea Ec, and the astigmatic axis can be calculated from the angle θ.

On the other hand, in the case of refractive power measurement, as shown in FIG.
2 to illuminate the fundus projection chart 13. As shown in FIG. 4, this chart 13 is provided with three slits 13a to 13c in three meridian directions that form an angle of 120 degrees with each other. light emitting diode 11
The light further passes through the relay lens 14, forms an image on the fundus illumination diaphragm 15, passes through the perforated mirror 16, passes through the dichroic mirror 6 since it is infrared light,
Only the far-infrared light passes through the dichroic mirror 5 and is imaged on the pupil of the eye E through the objective lens 4, forming the fundus Ef.
It is designed to illuminate.

The image of the chart 13 created by this far infrared light is the relay lens 1
4 and is once formed into an image, and projected by the objective lens 4 so as to be conjugate with the fundus of the emmetropic eye.

The reflected image from the fundus Ef passes through the objective lens 4 again, passes through the dichroic mirror 5.6, forms an image, and is reflected downward by the perforated mirror 16. A diaphragm plate 17 is disposed near the perforated mirror 16, and the diaphragm plate 17 has six apertures 17a to 17f each consisting of an annular transmitting portion, as shown in FIG. The openings 17a and 17d, 17b and 17e, and 17c and ITf correspond to each other and form one channel.The fundus illumination diaphragm 15 and the diaphragm plate 17 are the sixth Images are formed as shown at 15A and 17A in the figure, and the image of the chart 13 is separated into a projection optical system and a measurement optical system.

The light beam divided by the diaphragm plate 17 passes through the imaging lens 18 and is separated by the prism 19, and is then separated by the reflecting mirror 20.
The light is focused in the lateral direction of the detection element 22 through the cylindrical lens 21, and is imaged onto the three detection elements 22a to 22c. The prism 19 is shown in FIG.
It has six elements 19a to 19f as shown in FIG.
shows the cross-sectional shape of the prism 19.

The images separated in this way are focused in the longitudinal direction of the images by three cylindrical lenses 21a to 21c arranged as shown in FIG. Fundus image Pa corresponding to 17a to 17f
-Pf.

If the eye E to be examined is an ametropic eye, the light ray that exits from the fundus Ef and exits at a point above the pupil will be emitted at an angle that corresponds to the refractive power, so an optical system like the one in this example is used. Then, the distance between the two fundus images P on the detection element 22 changes depending on the refractive power of the eye E to be examined.

Therefore, if the relationship between the distance between the two fundus images P and the refractive power is determined in advance, the refractive power in the three radial directions can be measured, and each refractive power can be calculated using the following formula, D=A sin (2ω 10) + B. By substitution, the spherical power, astigmatic power, and astigmatic angle can be calculated. The variables D and ω represent the refractive power and the radial angle, respectively, and the constants RA, B, and θ correspond to the degree of astigmatism, the average refractive power, and the astigmatic axis, respectively.

The alignment between the eye E and the instrument is achieved by emitting light from a light source (not shown) and using a dichroic mirror 5 using an objective lens 4.
The infrared light reflected downward from the anterior segment of the eye is imaged onto a television image pickup tube 24 by a television relay lens 23, and the image can be imaged by a television monitor attached to the main body or provided separately.

The first one is equipped with a two-dimensional fixation target 25 for measuring eye refractive power.
The fixation means is provided above the beam splitter 7 together with the light source 26, and the fixation means illuminated by the light source 26! ! 42
5 is configured to be gazed at by the subject's eye E via the relay lens 27 and beam splitter 7. Fixation target 2
5 moves up and down on the optical axis together with the light source 26, that is, M n
By performing measurements while fixing the eye E to be examined at a plurality of positions, the eye E is controlled to eliminate mechanical myopia of the eye E to be examined.

If the fixation target 25 is a slide of a general scene where central fixation is difficult, it is inappropriate to use this as a fixation target for corneal shape measurement. E
A second fixation means having another point-like fixation target is provided at the emmetropic eye position f. For example, in this embodiment, one end of the fiber 28 is arranged at the center of the prism 9, and a light emitting diode 29 that emits visible light is arranged near the other end. When measuring the corneal shape, the illumination light source 26 is turned off, the light emitting diode 29 is turned on, and the fiber 28 is placed at the center of the prism 9.
By emitting light from the light emitting diode 29 via the light emitting diode 29, the subject's eye E can gaze at a clear bright spot, and the subject's eye E is fixed.

FIG. 9 shows a second embodiment in which the fiber 28 is installed at another emmetropic eye position of the eye E to be examined, and is located at the center position on the side of the illumination light source 26 of the two-dimensional fixation target 25 for eye refractive power measurement. One end of the fiber 28 is installed, and a light emitting diode 29 is placed at the other end. In this embodiment as well, the corneal shape is measured following the same procedure as in the previous embodiment, but in the case of this second embodiment, the fiber 28 can also be moved together with the fixation target 25, so the corneal shape can be measured. At this time, the brightness of the central bright spot relative to the surrounding area can be adjusted to allow the subject's eye E to gaze at it.

If a radial pattern is used as the fixation target 25 for refractive power measurement, it can also be used for corneal shape measurement, but since the fixation target 25 is usually installed at the emmetropic position, Since only the eye to be examined can gaze, the fixation target 25 is installed at a position corresponding to the refractive power of the eye to be examined E.

It is preferable to simply measure the refractive power before measuring the corneal shape, that is, to make the light emitting diode 11 emit light once,
When the detection element 22 captures the reflected image from the fundus Ef and moves the fixation target 25 to a position according to its refractive power, the fixation target 25 becomes clearly visible to the subject, and the subject's eye E can be securely fixed. Note that since the value of the spherical power necessary for determining the position of the fixation target 25 may be a rough number, only the l radius may be processed to shorten the measurement processing time.

If only corneal topography is to be measured, perform a simple refractive power measurement like this, but if refractive power and corneal topography measurements are to be performed consecutively, the measurement results of the refractive power measurement can be used as is. can do. That is, it is sufficient to move the fixation target 25 to a position corresponding to the spherical power obtained by the refractive power measurement and then proceed to the corneal shape measurement.

FIG. 10 shows the control circuit of this device, including a corneal shape measuring circuit 30 which manually inputs the signal of the detection element 10, an eye refractive power measuring circuit 31 which inputs the signal of the detecting element 22, and a signal of the eye refractive power measuring circuit 31. Fixation target 25 and light source 26 manually created and imaged
The fixation target control circuit 32 controls the fixation target control circuit 32, and the fixation target illumination control circuit 33 controls the light source 26 and the light emitting diode 29. Each is connected to a selection control circuit 34.

Note that the fixation target illumination control circuit 33 is a measurement selection control circuit 34.
This circuit is for appropriately switching the lighting of the light source 26 and the light emitting diode 29 according to the command, so this control circuit 33 is omitted when the fixation target 25 is one that allows the focus to be focused on the center of a radial pattern or the like. can.

In a device in which the fiber 28 is installed because the fixation target 25 is a slide of a general scene where central fixation is difficult, when eye refractive power measurement or continuous measurement is selected in the measurement selection control circuit 34, the fixation target 25 is fixed. The light source 2 is controlled by the visual target illumination control circuit 33.
6 is turned on, and the fixation target 25 is turned on by the fixation target control circuit 32.
By inputting the signal from the detection element 22 to the eye refractive power measurement circuit 31 while moving the light source 26, it is possible to obtain accurate refractive power measurement results in which instrumental myopia is removed.

In the case of continuous measurement, the light source 2 is controlled by the fixation target illumination control circuit 33.
6 is turned off, the light emitting diode 29 is turned on to create a bright spot on the fiber 28 that the eye E can easily gaze at, the eye E is fixed, and the measurement is performed, and the signal from the detection element 1.0 is used to measure the corneal shape. The circuit 30 allows corneal topography results to be obtained. When corneal shape measurement is selected by the measurement selection control circuit 34, the light emitting diode 29 is turned on by the fixation target illumination control circuit 33, and the corneal shape measurement value is obtained by following the same procedure as described above.

When a radial pattern is used as the fixation target 25, if eye refractive power measurement or continuous measurement is selected by the measurement selection control circuit 34, eye refractive power measurement is performed in the same manner as before, and continuous measurement is selected. In this case, the fixation target control circuit 32 moves the fixation target 25 to the position obtained by the eye refractive power measurement, and the eye E is made to gaze at the fixation target 25 to measure the corneal shape.

When only corneal shape measurement is selected by the measurement selection control circuit 34, data in only one radial direction is manually transmitted from the detection element 22 to the eye refractive power measurement circuit 31 according to the procedure for eye refractive power measurement, and the result is fixed. The fixation target 25 is moved by the target control circuit 32, and the eye E to be examined is made to gaze at the fixation target 25 to perform normal corneal shape measurement.

[Effects of the Invention] As explained above, according to the ophthalmological measuring device according to the present invention, fixation targets suitable for eye refractive power measurement and corneal shape measurement are provided, and these are switched and presented at the time of measurement, Alternatively, when measuring the corneal shape using the same fixation target, the fixation means is switched to a position suitable for the eye to be examined obtained by eye refractive power measurement, i.e., for example, the fixation target provided in the fixation means is moved. By doing so, a clearly visible fixation target is presented to the subject's eye, reducing the time for alignment during measurement, and the fixation state can be confirmed by observing the anterior segment of the eye, making it possible to obtain accurate measurement results. It is.

[Brief explanation of the drawing]

The drawings show an embodiment of the ophthalmological measurement device according to the present invention, and FIG. 1 is an optical configuration diagram thereof, FIG. The figure is an explanatory diagram of the relationship between the corneal reflection image and the detection element, Figure 4 is a front view of the fundus projection chart, Figure 5 is a front view of the aperture plate for eye refraction measurement,
Figure 6 is a front view of the image forming state of the aperture on the pupil of the eye to be examined, Figure 7 is a front view of the image separation prism for measuring eye refraction, f
b) is its sectional view, FIG. 8 is an explanatory diagram of the relationship between the fundus image and the light receiving element, FIG. 9 is a configuration diagram showing another embodiment of the fixation target for corneal shape measurement, and FIG. 10 is the control circuit. FIG. 2 is a block circuit configuration diagram of FIG. Symbol l is a ring-shaped strobe, 2 is a ring lens, 3 is a slit, 4 is an objective lens, 5.6 is a gicroic mirror, 7 is a beam splitter, 8 is a multi-hole aperture, 9.19
is a prism, 10.22 is a detection element, 11.29 is a light emitting diode, 13 is a chart, 15 is an illumination diaphragm, 16 is a perforated mirror, 17 is treated as an aperture, 21 is a cylindrical lens, 24 is a television carrier tube, 25 is a A fixation target, 26 a light source, 28 a fiber, 30 a corneal shape measurement circuit, 31 an eye refractive power measurement circuit, 32 a fixation target control circuit, 33 a fixation target illumination control circuit, and 34 a measurement selection control circuit. It is. Patent applicant Canon Co., Ltd.

Claims (1)

[Claims] 1. An eye refractive power measuring optical system for the eye to be examined, a corneal shape measuring optical system that partially shares an optical system with the eye refractive power measuring optical system, and a two-dimensional fixation target. A first fixation means for measuring eye refractive power that presents a two-dimensional fixation target to the subject's eye and performs fogging, and a central fixation target located at the center of the visual field, and presents the central fixation target to the subject's eye. a second fixation means for measuring the corneal shape; a means for adjusting the second fixation means to a position adapted to the eye refractive power of the eye to be examined obtained by the eye refractive power measuring optical system; 1. An ophthalmological measuring device comprising means for observing the anterior segment of the eye. 2. The ophthalmological measuring device according to claim 1, wherein the two-dimensional fixation target and the central fixation target are the same fixation target. 3. Claim 2, wherein the same fixation target comprises a radial pattern.
The ophthalmological measuring device described in . 4. The ophthalmological measuring device according to claim 2, wherein the same fixation target has a bright spot arranged at the center of the two-dimensional fixation target and operates independently of the surrounding area.