JPH06343609A - Keratometer and fixed target device - Google Patents

Abstract

PURPOSE:To provide a keratometer which can make stable and accurate mea surement even at the time of measuring the cornea periphery of the eye to be inspected. CONSTITUTION:A keratometer to measure the cornea shape information is equipped with a fixed target means 6 for measuring the cornea periphery to be fix-viewed by the eye to be inspected so that the view direction of the eye is displaced, when the shape information of the cornea periphery is to be acquired, and an emitted light flux restricting means 6a which is provided for the light emitted by the fixed target means 6 not to be fix-viewed by the other eye than that to be inspected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a keratometer for measuring corneal shape information of an eye to be inspected and a fixation target device applicable to the keratometer.

[0002]

2. Description of the Related Art Conventionally, a measurement index is projected on the cornea of an eye to be examined,
In the keratometer for measuring the radius of curvature of the cornea from the corneal reflection image, there was a keratometer for measuring the radius of curvature not only in the central portion of the cornea but also in the corneal portion deviated from the center of the cornea, that is, the peripheral portion of the cornea. As a method of measuring the peripheral part of the cornea, in addition to the measurement index used for measuring the central part, a measurement index used for measuring the peripheral part is provided, or a fixation target for measuring the peripheral part of the cornea is provided to the eye to be examined. Displace the cornea of the eye to be examined by fixing it,
There is a method of measuring using a measurement index projected on the peripheral part of the cornea of the eye to be inspected.

[0003]

However, in the method of separately providing the measurement index for measuring the peripheral part of the cornea, the measurement index for measuring the peripheral part must be provided outside the measurement index for measuring the central part. There was a problem that the index projection unit had to be enlarged. In addition, since the measurement index is projected on the peripheral part of the eye to be fixed to the front, the measurement index projection light for measuring the peripheral part may be partially shaded by the effect of the eyelid, and measurement may not be possible. There was also the problem of being large.

On the other hand, in the method of providing the fixation target for measuring the peripheral portion of the cornea, since the fixation target is provided at a position greatly separated from the optical axis of the apparatus, the fixation target is provided separately from the measurement optical system. However, it is desirable to provide the fixation target at a position close to the eye so that the fixation target can be easily seen from the eye. In this case, the fixation target is easily fixed by the opposite eye. When the eye on the opposite side gazes at this fixation target, the eye to be inspected linked to this eye on the opposite side does not accurately fix the line of sight in the direction of the fixation target. There is a possibility of giving a curvature radius measurement value.

In view of the above-mentioned problems of the conventional example, the present invention provides a fixation target device for displacing the gaze direction from the front direction so that the eye on the opposite side is not affected, and is stable and accurate. It aims to provide a keratometer capable of measuring a peripheral corneal region.

[0006]

In order to achieve the above object, the present invention provides a keratometer for measuring corneal shape information, in order to displace the eye direction of the eye to be measured when measuring the shape information of the corneal peripheral part. A fixation target means for measuring the corneal periphery, and an exit light flux limiting means for preventing the light emitted from the fixation target means from being fixed by the eye opposite to the eye to be examined. I have it.

Further, the fixation target device of the present invention is a fixation target means for fixing the eye to be examined so as to displace the line-of-sight direction of the eye from the front direction, and the light emitted from the fixation target means is the eye to be examined. Ejection light flux limiting means for preventing fixation by the opposite eye.

[0008]

1 is a schematic sectional view showing the structure of an objective portion according to a first embodiment of the present invention, and FIG. 2 is a front view of the objective portion. In the figure, E is an eye to be inspected, 1 is a constituent member that constitutes a projection portion of a measurement index, 2 is an infrared light source for measuring corneal curvature, 3 is a diffusion plate having a high light diffusivity for diffusing a light flux from the light source 2, Reference numeral 4 is a light source for observing the external eye at the time of alignment and also serves as a fixation target for fixing the eye E to be inspected when measuring the peripheral portion of the cornea, 5 is a printed circuit board on which the light sources 2 and 4 are mounted, and 6 is a light source 4 is an opening, 6a is a groove provided on the constituent member 1, and 7 is an opening for a measurement optical system (not shown) which exists on the right side of the drawing. FIG. 3 is a view of the constituent member 1 as viewed from the back side. The constituent member 1 is formed by molding a synthetic resin or an aluminum alloy. The position where the diffuser plate 3 is attached to the constituent member 1 and the eye E to be inspected
The position of the opening 6 that serves as a fixation target for fixing the eye is predetermined by this type. Further, the opening 6 is formed in the groove 6 on the constituent member 1 so as not to be seen by the eye on the side opposite to the eye to be inspected, other than the direction in which the eye to be inspected exists, as shown in FIG.
It is provided at the bottom of a.

As shown in FIG. 2, the diffusion plate 3 is arranged in a ring shape around the optical axis O of the measuring optical system. In this embodiment, the diffusion plate 3 is fixed to the component member 1 by pouring an adhesive agent through the adhesive holes 3a provided in the component member 1 at several positions.
The fixing of the diffusion plate 3 is not limited to this method, and may be crimped by, for example, press fitting or heat.

The light source 2 follows the ring shape of the diffusion plate 3,
A plurality of them are arranged in a circle. The larger the number of the light sources 2 is, the more the light amount can be earned. However, if the light sources 2 are provided too densely, the light source 2 separates the constituent members inside and outside the ring.
It is desirable to determine the number of light sources 2 within a range in which light is evenly emitted from the diffusion plate.

As shown in FIG. 2, eight apertures 6 and the light sources 4 disposed behind each aperture are arranged on the circumference. Light source 4
Is designed to emit two colors of visible light and infrared light. Then, all eight of the light sources 4 emit infrared light for observation illumination so as not to be seen by the eye to be inspected at the same time when performing external eye observation at the time of alignment or measuring the central portion of the cornea. or,
When measuring the peripheral part of the cornea, only the light source in the direction in which the eye to be examined should be fixed emits visible light, and the other seven light sources remain infrared emission.

The substrate 5 is fixed to the component member 1 with screws,
Only the substrate 5 can be replaced when the light source is cut off or weakened due to aging or the like. If the light source is replaced by another method, it may be bonded.

FIG. 4 is a schematic view of the optical system configuration of this apparatus. In the figure, 8 is an imaging lens part of the measurement optical system, 9 is a movable diaphragm, 10 is a two-dimensional photodetector, 11 is a visible light source, 12 is a fixation target for measuring the central part of the cornea, 13 is a lens, and 14 is red. It is a dichroic mirror that transmits external light and reflects visible light. The operation of this apparatus will be described with reference to this figure. Light source 2
The light emitted by the light passes through the space of the component member 1 and reaches the diffusion plate 3. The inner wall of the space of the component member 1 is preferably a mirror surface in order to transmit the light amount of the light source 2 without waste. The light is diffused sufficiently evenly by the diffusion plate 3 and is applied to the eye E as a ring-shaped index to form an index image R'as a corneal reflection image on the cornea EC of the eye to be inspected. This index image R ′ is imaged together with the anterior ocular segment of the subject's eye on the two-dimensional photodetection element 10 via the imaging lens unit 8 and the moving diaphragm 9. The movable diaphragm 9 is separated from the optical axis O during alignment,
It is inserted on the optical axis O when measuring the corneal curvature. The position of the movable diaphragm 9 on the optical axis O has a measurement error even if the working distance between the eye E to be inspected and the diffuser plate 3 as an index is changed as disclosed in JP-A-61-249432. It is a position where it decreases. The image information detected by the detection element 10 is processed by a signal processing circuit (not shown) and displayed on a monitor.

When measuring the central part of the cornea, the light source 11 is turned on and the eye E to be examined is placed on the dichroic mirror 14 and the lens 1.
The fixation target 12 on the optical axis is fixed through 3 In this state, the examiner looks at the monitor and aligns the apparatus main body with respect to the eye E in the vertical and horizontal directions and the working distance direction. FIG. 5 shows an image on the monitor 15 in a state where the alignment is completed. After the alignment is completed, the detection element 1
From the image signal of the index image R ′ in the image signal of 0, the corneal curvature radius is measured by a well-known method with a signal processing circuit (not shown). With this, the radius of curvature of the cornea at the center of the cornea can be measured.

Next, when measuring the peripheral part of the cornea, the light source 11 is used.
Is turned off, and the light source existing in the direction opposite to the direction to be measured on the cornea of the light source 4 emits visible light, and the light emitted from the opening 6 corresponding to this light source is fixed to the eye E to be examined. In this state, the inspector looks at the monitor and attaches the device body to the subject's eye E.
Align relative to. FIG. 6 shows an image on the monitor 15 in a state where the alignment is completed.
After the alignment is completed, the radius of curvature of the cornea is measured from the image signal of the index image R ′ in the video signal of the detection element 10 by a well-known method in a signal processing circuit (not shown). Thereby, the radius of curvature of the cornea in the peripheral part of the cornea can be measured. If the shape of the cornea in the central part of the cornea is measured in advance, the direction of the main diameter line of the corneal astigmatism can be known. Two light sources in a direction that is perpendicular to
By sequentially emitting visible light to measure the peripheral portion of the cornea, the radius of curvature of the peripheral portion of the cornea in the direction close to the main radial direction and in the direction perpendicular thereto can be known.

FIG. 7 is a diagram for explaining the effect of this device.
When measuring the peripheral part of the cornea, the eye E'on the side opposite to the eye E to be inspected
If the fixation target can be fixed by the eye, the fixation target may be fixed by the eye E ′ on the opposite side as described above. However, in this embodiment, since the opening 6 is provided at the bottom of the groove 6a provided in the component member 1, the opening 6 cannot be fixed from the direction of the eye E '. This allows
This enables accurate measurement of the radius of curvature of the corneal periphery.

Although the fixation means shown in the above embodiment is integrated with the index projection unit in the embodiments, it may be provided independently of the index projection unit. Although the number of the light sources 4 is eight in the embodiment, the number may be increased or decreased depending on the frequency of use.

FIG. 8 is a view showing a modification of the constituent members of the above apparatus. Since the measurement index portion is the same, the description is omitted. Unlike the constituent member 1, the constituent member 16 does not have the opening 6 serving as a fixation target, and instead, the light source 1 serving as a fixation target.
The head of No. 7 projects from the bottom of the groove 16 a provided in the component 16. Due to the effect of the groove 16a, the fixation target cannot be fixed from the eye on the side opposite to the eye to be examined, as in the above-described embodiment. If the diameter of the head of the light source 17 is large, the viewpoint of the eye to be inspected may be uncertain and measurement may be difficult. Therefore, it is desirable that the head of the light source 12 be as small as possible.

FIG. 9 is a view showing a further modified example of the constituent members. An LED 19 serving as a fixation target directed toward the eye E to be inspected and a substrate 20 on which the LED 19 is mounted are attached to the component member 18. The head of the LED 14 is spherical, and the LED chip is at a position 2 / r from the top of the head, where r is the radius of the spherical surface. Therefore, since parallel light is projected from the LED 14 onto the eye E to be inspected, the eye on the side opposite to the eye E to be inspected cannot fixate. If the substrate 20 is a flexible substrate, it can be integrated with the substrates of LEDs in other positions.

[0020]

As described above, since the fixation target for one eye of the present invention is invisible to the other eye, the fixation target in which the other eye is not affected and more accurate corneal peripheral portion It has become possible to measure the corneal shape of the.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing the structure of an objective unit according to a first embodiment of the present invention.

FIG. 2 is a front view of the objective unit according to the first embodiment of the present invention.

FIG. 3 is a view of the constituent members as viewed from the back side.

FIG. 4 is a schematic diagram of an optical system configuration of the apparatus of the first embodiment.

FIG. 5 is a diagram showing an image on a monitor.

FIG. 6 is a diagram showing an image on a monitor.

FIG. 7 is a diagram illustrating an effect of the device according to the first embodiment.

FIG. 8 is a modified example of the constituent members.

FIG. 9 is a modification of the constituent members.

[Explanation of reference numerals] 1 constituent members 2 light source 3 diffusion plate 4 light source 5 printed circuit board 6 opening 6a groove 7 opening 8 imaging lens section 9 moving narrowing 10 two-dimensional photodetection element 11 light source 12 fixation target

Claims (2)

[Claims] 1. In a keratometer for measuring corneal shape information, a fixation target for measuring the corneal peripheral portion, which is fixed to the eye to be displaced so as to displace the line-of-sight direction of the eye when measuring the peripheral shape information. A keratometer, which is provided with a means and an emission light flux limiting means for preventing the light emitted from the fixation target means from being fixed by the eye opposite to the eye to be examined. 2. A fixation target means for fixing a target eye so as to displace the line-of-sight direction of the target eye from the front direction, and the light emitted from the fixation target means is fixed by an eye opposite to the target eye. A fixation target device comprising: an exiting light flux limiting means for preventing the above.