JP2962845B2 - Corneal curvature measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a corneal shape measuring device used in, for example, an ophthalmic clinic.

[0002]

2. Description of the Related Art A so-called keratometer for measuring the curvature of a cornea measures an area near the center (2 to 3 mm in diameter), and approximates the cornea to a torric plane and displays the measured value. Conventional fixation lamps for measuring the periphery of this main device are known as external type, which can be moved arbitrarily by an examiner to an unspecified position, or built-in type, which has only four points in vertical and horizontal directions. .

Further, as a method for performing more precise measurement of the shape of the cornea, a method is known in which an index image is simultaneously projected on the entire cornea area (diameter: 8 to 10 mm) and the entire shape is measured at one time.

[0004]

However, among the above-mentioned keratometers, the conventional apparatus in which the examiner manually sets the measurement site requires a very complicated operation in determining the position of the fixation lamp when performing the peripheral measurement. In addition, the inspection time becomes longer. A conventional device of a type in which four fixation lights are built in only in the vertical and horizontal directions is provided to improve this point. However, in order to select a base curve of a contact lens, the device is used. Was not appropriate. First
How the curvature in the peripheral portion of the cornea differs depends on the eye to be examined, and thus it is necessary to turn on the fixation lamp more appropriately for each eye to be measured and measure the curvature. There is no special configuration for turning on the fixation lamp, and the device is insufficient in this respect. Separately from this, the cornea to be examined usually has a shape similar to the toric surface, and the curvature at the peripheral portion of the cornea and the curvature of the central cornea are most greatly different in each of the major meridian directions of the toric surface. The meridian direction may be asymmetric with respect to the vertical and horizontal support axes. In order to select the base curve of the contact lens for such an eye to be examined, it is necessary to use only four points in the vertical and horizontal directions.
The measurement information was insufficient with an apparatus of a system in which a point fixation lamp was built-in.

In order to select contact lenses more strictly, the above-mentioned conventional apparatus of the type which simultaneously projects an index image onto the entire cornea is useful, but practically it is not necessary to perform such a precise measurement. This type of device, which is complicated and takes a long time to calculate, is not widely used.

[0006] An object of the present invention is to provide a corneal curvature measuring apparatus which has solved the above-mentioned disadvantages of the conventional example.

[0007]

To achieve the above object, the present invention provides a measuring means for measuring a curvature of a cornea of a subject's eye,
In order to measure the corneal shape of the peripheral portion of the cornea of the subject eye,
In a corneal shape measurement device having a plurality of peripheral measurement fixation lamps arranged at positions shifted with respect to the optical axis direction of the measurement optical system of the measurement means, in a state in which the subject's eye fixates on the measurement center Control means for measuring corneal curvature information by the measuring means, selecting a position where the peripheral measurement fixation lamp should be lit based on the curvature information, and controlling lighting of the selected peripheral measurement fixation lamp. It is characterized by having.

[0008]

The corneal shape at the peripheral portion of the cornea can be quickly measured by sequentially lighting the peripheral fixation lights based on the corneal information obtained by the measurement of the central region, particularly the information on the direction of the main meridian.

[0009]

FIG. 1 is a block diagram of a corneal curvature measuring apparatus. On an optical axis P1 of an objective lens 1, a dichroic mirror 2, a relay lens 3, and a quick return mirror 4 are sequentially arranged behind the objective lens 1. , An imaging element 5, and a stop 6, a relay lens 7 having a larger magnification than the relay lens 3, and a dichroic mirror 8 are provided on the optical axis P <b> 2 in the reflection direction of the dichroic mirror 2. .
A reflection mirror 9 is provided at the intersection of the optical axis P4 in the reflection direction of the dichroic mirror 8 and the optical axis P3 in the reflection direction of the quick return mirror 4. The output of the image sensor 5 is connected to a television monitor (not shown). As shown in FIG. 2, a ring-shaped myring 11 whose center coincides with the optical axis P1 is provided around the objective lens 1, and further around the myring 11 is a concentric circle centered on the optical axis P1. , Four measurement light sources 12a to 12d are arranged at an angle of 90 degrees. The quick return mirror 4 can be inserted into and removed from the optical axis P1 by a driving means (not shown) as indicated by an arrow in the operation direction.

During the observation of the anterior eye, the quick return mirror 4 is separated from the optical axis P1. The luminous flux emitted from the earring 11 and the anterior segment illumination light source (not shown) is reflected by the cornea Ec and the anterior segment of the eye E, goes right on the optical axis P1, and is observed through the objective lens 1 and the relay lens 3. An image is formed on the image sensor 5 by the optical system for use, and an anterior eye image and a corneal reflection image of the myring 11 are projected on a television monitor.

On the rear optical axis P5 of the dichroic mirror 8, a fixation lamp unit 13 is provided at a position conjugate with the rear focal position of the objective lens 1.

The characteristics of the dichroic mirrors 2 and 8 are shown in FIG.
The anterior eye image is captured on the image sensor 5 with light having a wavelength longer than 750 mm transmitted through the dichroic mirror 2, while the LED 14 having the peak emission wavelength 650 mm of the fixation lamp unit 13 is a dichroic light. After passing through the reflection mirror 8 and passing through the relay lens 7, the light is reflected by the dichroic mirror 2, passes through the objective lens 1, and the subject's eye E
Projected to A measurement site of the cornea is determined by the eye to be inspected E fixing the LED. Fixation light unit 13
As shown in FIG. 4, 37 LEDs 14c, 14o to 14-35 are set in a plane perpendicular to the optical axis P5. The central LED 14c is for measuring the central part of the cornea on the optical axis P5, and the other LEDs are for measuring the peripheral part of the cornea and are arranged at a 10 ° pitch on a circle having a radius of R from the optical axis. Radius R
Is a predetermined value that falls within the range of 20 ° to 30 ° in the viewing angle when the objective lens is emitted. The LED drive circuit 15 receives a signal from the controller 16 and turns on one of the 37 LEDs.

When the corneal shape is measured, when the quick return mirror 4 is inserted on the optical axis P1, the measuring light sources 12a to 12
The light beam from d is also reflected by the cornea Ec of the eye E,
The light travels rightward on the optical axis P1, passes through the objective lens 1, is reflected by the dichroic mirror 2, the light beam is restricted by the stop 6 on the optical axis P2, and further passes through the relay lens 7 to the dichroic mirror 8, the reflecting mirror 9, The measurement optical system reflected by the quick return mirror 4 projects the image onto the image sensor 5 at an imaging magnification larger than that of the observation optical system. The image of the anterior eye part during observation and the earring 11 are displayed on a television monitor (not shown).
Of the measurement light sources 12a-1
2d corneal reflection images 12A to 12D are displayed. In addition,
The diaphragm 6 is arranged at such a position that the magnification of the corneal reflection images 12A to 12D of the measurement light sources 12a to 12d on the image sensor 5 does not change even if the distance between the eye E and the corneal shape measuring device changes. . The corneal reflection image on the image sensor 5 is stored in the frame memory 17 once, and a known operation is performed by the controller 16 to calculate the radius of curvature of the cornea.
When performing only the center measurement, the fixation lamp 14c at the center of the fixation lamp unit 13 is turned on, and the measurement is completed by a measurement switch (not shown). However, if the mode switching switch 18 is now in the peripheral measurement mode, Follow the flowchart of FIG. That is, when the peripheral measurement mode is selected, it is determined whether the center measurement value has already been obtained. If not, the fixation lamp LED 14c is turned on and the measurement operation is repeated until the examiner finishes the measurement. The end of the center measurement depends on the input of SW indicating the meaning of the end. Here, when a printer switch that also serves as a printout switch that outputs measured values to a printer is turned on, a representative value of the obtained center measured value is output to the printer. Here, as is well known, when the corneal reflection image positions are connected to each other, a toric surface approximation is obtained. Can be When the asymmetry of the corneal curvature is detected from the corneal curvature information obtained at the position of the fixation lamp for center measurement, the controller 1
Reference numeral 6 sequentially turns on the fixation LEDs on the same circumference on both main meridians at four locations to perform peripheral measurement.

When the asymmetry of the corneal curvature is not detected from the corneal curvature information obtained at the position of the fixation lamp for central measurement, that is, when it is assumed that the corneal curvature has a symmetric corneal shape in which each corneal curvature is substantially equal in each meridian direction. The control system terminates the measurement without turning on the peripheral measurement fixation lamp, but specifies at most two points as the peripheral measurement fixation lamp position as described later, and sequentially turns the fixation lamp at this fixation lamp position. The lighting may be turned on to measure the corneal curvature, and the processing may be terminated.

Since the peripheral measurement routine is the same as the center measurement, the description is omitted.

Here, the order of lighting of the fixation LED is, for example, when there is no center measured value, 1) LED 14 on the optical axis.
c, 2) Upper LED 14-3 in the direction of strong main meridian A1
3, 3) The upper LED 14-6 in the direction of the weak main meridian A2,
4) LEDs 14-15 below in the direction of the strong main meridian A1 5)
14-24 below in the direction of the weak main meridian A2, and so on. At this time, the subject is presented with fixation lights in the order from the upper part to the lower part as shown in FIG.

When the angle of each meridian does not exactly coincide with the position of the fixation lamp, it is needless to say that the closest LED should be selected.

Regarding the measured value to be printed out, a position at which the measured value is specified is clearly displayed, and a position at which the fixation lamp is currently turned on is displayed on the TV monitor.

It is useful to make the fixation lamp unit 13 movable on the optical axis so as to cope with the refraction abnormality of the subject.

In the embodiment described above, the peripheral measurement is not performed when the AS value of the central measured value is small in the above-described embodiment. It is also useful to detect asphericity by performing peripheral measurement at two points in the left-right direction, for example, of the four points. In addition, 2
Obviously, the peripheral measurement may be performed at only one point instead of the point.

In the above embodiment, the fixation light unit 1
Reference numeral 3 used an LED having no movable part composed of 37 LEDs, but one LED for the periphery was prepared in addition to the LED for the center, and the LEDs for the periphery were mechanically arranged on the circumference. The rotation may be controlled, or only the center LED may be prepared and used as the peripheral LED. Furthermore, it is conceivable that the examiner can manually select or move the peripheral fixation lamp from outside, and not only the manual operation but also the automatic operation and the manual operation can be selectively used.

[0022]

As described above, according to the present invention, the peripheral fixation lamps are sequentially turned on based on the corneal information obtained by measuring the central part, in particular, the information on the direction of the main meridian line, so that the peripheral part of the cornea can be quickly turned on. Of the cornea can be measured.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a corneal curvature measurement device embodying the present invention.

FIG. 2 is a layout diagram of a measurement light source and an alignment light source.

FIG. 3 is a characteristic diagram of a dichroic mirror.

FIG. 4 is a plan view of a fixation light unit.

FIG. 5 is a diagram showing an operation flow in a peripheral measurement mode.

FIG. 6 is a diagram showing a state of a change in a visual field of a subject.

[Explanation of symbols]

 E Eye to be inspected Ec Corneal eye to be inspected 1 Objective lens 2, 8 Dichroic mirror 5 Image pickup device 11 Meyer ring 12 Light source for measurement 13 Fixation light unit 14 Fixation light LED 16 Controller 17 Frame memory 18 Mode switching switch

Claims (2)

(57) [Claims] A measuring means for measuring a curvature of a cornea of an eye to be examined;
In order to measure the corneal shape of the peripheral portion of the cornea of the subject eye,
In a corneal shape measurement device having a plurality of peripheral measurement fixation lamps arranged at positions shifted with respect to the optical axis direction of the measurement optical system of the measurement means, in a state in which the subject's eye fixates on the measurement center Control means for measuring corneal curvature information by the measuring means, selecting a position where the peripheral measurement fixation lamp should be lit based on the curvature information, and controlling lighting of the selected peripheral measurement fixation lamp. A corneal shape measuring device comprising: 2. The corneal shape according to claim 1, wherein the control means obtains a principal meridian direction of the corneal curvature from the corneal curvature information and turns on a peripheral measurement fixation lamp in the principal meridian direction. measuring device.