JPH05329104A - Cornea geometry measuring apparatus - Google Patents

Abstract

PURPOSE:To enable the measuring of a sagittal radius of curvature automatically by arranging a target projection optical system to project a target for measuring the sagittal radius of curvature of the peripheral part of the cornea and an arithmetic means to determine the sagittal radius of curvature by detecting a target image projected with a detection optical system. CONSTITUTION:When a specified switch is depressed to switch over to a mode of measuring a sagittal radius of curvature of the peripheral part of the cornea, a spot light source 1a is turned ON and an outgoing light thereof is made parallel with a collimating lens 2a. Here, by staring at the pot light source 1a, an eye to be inspected is turned by a certain angle with respect to a measuring optical axis. Then, when the measuring optical axis is set to a specified position in the lower perimeter of the cornea 3 to depress a measuring switch, other spot light sources than the spot light sources 1a and 1b come ON and an interval between images thereof is detected with a one-dimensional primary position detector 5b. Then, a sagittal radius of curvature in the lower perimeter of the cornea 3 is calculated by an arithmetic means based on the image interval detected.

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 apparatus for measuring the radius of curvature of the cornea.

[0002]

2. Description of the Related Art Various off-salmometers have been proposed as a device for measuring the radius of curvature of the central portion of the cornea. These devices measure the radius of curvature in the radial direction near the center of the cornea. Recently, a device that detects the corneal reflection image created by the projection optical system that is projected around the apex of the cornea and detects the radius of curvature automatically has been put into practical use. It does not differ from conventional devices in terms of measurement. In addition, a device capable of measuring a spherical radius of curvature has also been proposed in a manual type off-salmometer. This device is provided with a fixation target such as a lamp around the measurement optical axis, guides the fixation position of the eye to be inspected, and puts a predetermined peripheral part of the cornea on the measurement optical axis, so that the aspheric curvature of the eye to be inspected. Measuring the radius.

[0003]

However, it has been pointed out that the measurement of the radius of curvature in the radial direction of the cornea alone is not sufficient for determining the base curve of the contact lens. In Europe, a spherical radius of curvature may be used as a reference when determining the base curve of a contact lens. In particular, since the radius of curvature of the cornea increases toward the peripheral portion, the information on the peripheral portion of the cornea is useful for determining the base curve of the contact lens that adheres to a wide area of the cornea.

Further, in the manual type off-salmometer capable of measuring the radius of curvature having a non-spherical shape, the fixation target is placed near the eye to be inspected, in addition to the drawback that the manual type is complicated.
There is a drawback in that a very large adjustment force is required to fix this. The present invention has been devised in view of the above drawbacks, and an object thereof is to provide a cornea shape measuring apparatus which is an automated apparatus and which can easily measure a spherical curvature radius.

[0005]

In order to achieve the above object, the present invention has the following features. (1) A first index projection optical system that projects a plurality of point indexes onto a cornea of an eye to be examined at a predetermined projection angle, a detection optical system that detects the position of the point indexes projected on the cornea, and detection by the detection optical system A corneal shape measuring apparatus comprising means for obtaining a radius of curvature of a cornea based on a result, wherein the point index is constituted by a visible light beam, and a fixation guide means for guiding the fixation of an eye to be examined with the point index as a fixation point. A mode changeover switch for changing over to a mode for measuring a spherical radius of curvature, and a second index projection optical system for projecting a second index for measuring a spherical radius of curvature orthogonal to the guiding direction. And a calculation unit that detects the index image projected by the second index projection optical system by the detection optical system and obtains a spherical radius of curvature.

(2) The first index projection optical system of (1) is characterized in that a point index is arranged at the focal position of the lens.

(3) The first index projection optical system of (1) has four point light sources arranged in the vertical and horizontal directions of the eye to be inspected,
When the upper and lower point light sources are used as the fixation index, the left and right point light sources are used, and when the left and right point light sources are used as the fixation index, the upper and lower point light sources are used as the second index.

(4) The fixation guidance means of (1) is a selection means for selecting a fixation position, and a presentation index control means for distinguishing between the point index of the selected fixation position and another point index. And having.

(5) A first index projection optical system for projecting an index onto the cornea of the eye to be examined at a predetermined projection angle, a detection optical system for detecting the position of the point index projected on the cornea, and detection by the detection optical system. In a corneal shape measuring device comprising means for obtaining the radius of curvature of the cornea based on the result, a mode changeover switch for changing over to a mode for measuring the abrupt radius of curvature,
A fixation guide means for guiding the fixation of the eye to be inspected, which is composed of a visible light beam, and a second index projection optical system for projecting a second index for measuring a spherical curvature radius orthogonal to the guiding direction. Selection means for selecting a fixation position, control means for presenting a second index of the selected fixation position, and an index image projected by the second index projection optical system is detected by the detection optical system. And a means for automatically determining and displaying the position of the measured radius of curvature based on the selection signal from the selection means. ..

[0010]

EXAMPLES Examples of the present invention will be described below.
FIG. 1 is a diagram showing a measurement optical system of the corneal shape measuring apparatus.
Reference numerals 1a, 1b, 1c and 1d (1c and 1d are not shown) are point light sources composed of a light emitting diode, and are fixed as a measuring light projected on the cornea of the eye to be inspected or fixed to the eye to be inspected. It emits a light flux in the near-infrared region so as to function as a target. Light emitted from the point light sources 1a and 1b is converted into a parallel light flux by the collimating lenses 2a and 2b, and the cornea 3 of the eye to be inspected.
Projected at an angle of α onto the point light source images 1a ′, 1b ′
You can Similarly, the light emitted from the point light sources 1c and 1d (not shown) located at a position where the point light source 1a is rotated by 90 degrees with respect to the optical axis O becomes a parallel light flux by the collimating lenses 2c and 2d (not shown), and α is incident on the cornea 3 of the eye to be examined. Are projected at an angle of 3 to form point light source images 3c 'and 3d' (not shown). The point light sources 1a, 1b, 1c, 1d are also used for the fixation target of the eye to be examined, and the details of the selection will be described later.

The imaging lens 4 includes a one-dimensional position detecting element 5
a, 5b detection surfaces and point light source images 1a ', 1b', 1c ',
1d ′ is arranged at a conjugate position, and a telecentric diaphragm 6 is arranged at the image-side focal position thereof. The beam splitter 7 divides the optical path into two. Further, between the telecentric diaphragm 6 and the one-dimensional position detecting elements 5a and 5b, convex cylindrical lenses 8a and 8b are arranged so that their axes (bus lines) coincide with the detection direction of the one-dimensional position detecting element. The focal lengths of the convex cylindrical lenses 8a and 8b are infinite in the cross section in the cylinder axis direction, and the telecentric diaphragm 6 and the one-dimensional position detecting element 5 are in the cross section in the direction orthogonal to the cylinder axis direction.
It is designed so that a and 5b are almost conjugate. Further, the one-dimensional position detecting elements 5a and 5b are relatively orthogonal to each other.

FIG. 2 is a block diagram of the electric system of the apparatus. 1
0 is an LED driver for lighting four point light sources (1a, 1b, 1c, 1d), 11 is a drive circuit for capturing signals on the detection elements 5a, 5b, 12 is a clock counter, and 13 is a clock generation circuit. , 14 is a peak-hold circuit for holding the peak voltage of the signal sent from 11, and 15 is a signal and peak-hold circuit 14 from 11
, A comparator for outputting a strobe signal by comparing the voltage with a signal converted into a half of the peak voltage through a computer 17, and 16 is a comparator for outputting a strobe signal. Latch for holding counter value, 18 is A / D
A converter 19 is a D / A converter.

Reference numeral 20 denotes a switch for switching the measurement mode, which switches from the mode for measuring the radius of curvature in the meridian direction near the apex to the mode for measuring the spherical radius of curvature in the peripheral portion of the cornea. Reference numeral 21 is a fixation designation switch for designating a position to be fixed at the time of measuring the spherical curvature radius. 22 is a display circuit, 23
Is a television monitor. The television monitor 23 displays an anterior ocular segment image captured by a television camera (not shown) and also displays measurement data and the like.

The signal obtained by the detection element 5 is transmitted to the drive circuit 11. The signal from the drive circuit 11 is transmitted to the comparator 15 and the peak-hold circuit 14.
The peak voltage detected by the peak hold circuit 14 is converted into a digital signal by the A / D converter 18 and then input to the computer 17. The digital signal of the peak voltage output at 17 is converted into a voltage signal of 1/2 of the peak voltage at the D / A converter 19 and input to the comparator 15. This signal and the signal directly input to the comparator 15 are compared with each other to output a strobe signal. A signal having a peak voltage of 1/2 is to be compared with the signal input one time before. Become. The strobe signal causes the signal of the counter 12 to enter the latch 16, and the position of the bright and dark edges is read from the waveform at that time.

Next, the operation of the apparatus having the above configuration will be described. FIG. 3 is a flow chart for explaining the measuring operation. The method of measuring and calculating the radius of curvature in the radial direction of the central portion of the cornea is described in detail in Japanese Patent Laid-Open No. 61-85920, and the description thereof will be incorporated herein. The eye to be inspected and the device are placed in a predetermined positional relationship by a known alignment mechanism (not shown). The measurement mode when the power is turned on is a mode for measuring the radius of curvature in the meridian direction near the apex of the cornea, and the point light sources 1a to 1d are sequentially or simultaneously (when the lights are turned on simultaneously, an image separation prism or the like may be used. ) Is turned on, and the radius of curvature and the axial angle of the strong and weak main meridians are calculated based on the detection result of the image position.

When the switch 20 is pressed, the mode is switched to the mode for measuring the spherical radius of curvature of the peripheral portion of the cornea. Mode
When the mode is switched, the point light source 1a lights up (blinks for attention). The light emitted from the point light source 1a is made into a parallel light flux by the collimating lens, and the eye to be examined can see the point light source 1a at infinity. FIG. 4 shows this state, and by fixing the point light source 1a, the subject's eye 3 rotates by an angle α with respect to the measurement optical axis.
The measurement optical axis is aligned with a predetermined position around the lower part of the cornea and a measurement switch (not shown) is pushed. When the measurement switch is pressed, the point light sources 1c and 1d are turned on, and the image interval thereof is detected by the one-dimensional position detecting element 5b. Based on the detected image interval, the spherical curvature radius around the lower cornea is calculated.

Next, the fixation light designating switch 21 is pressed to operate the point light source 1b as a fixation light (instead of depressing the fixation light designating switch 21, the fixation light is switched in a predetermined order based on the measurement signal of the measurement switch. May be switched.). In this way, when the point light source 1b is used as a fixation lamp, the spherical curvature radius around the upper part of the cornea is the same. As for the target radius of curvature, the point-shaped light source 1d is used as a fixation lamp to measure the spherical radius of curvature around the left portion of the cornea. The measurement data thus obtained is stored together with the position signal obtained from the fixation designating switch 21 (or the pre-programmed measurement sequence and the measurement signal of the measurement switch), and the television monitor 23 via the display circuit 22.
Displayed in. It goes without saying that various modifications are included within the scope of making the technical idea the same.

[0018]

As described above, according to the present invention, the spherical radius of curvature can be easily measured by an automated device.

[Brief description of drawings]

FIG. 1 is a diagram showing a measurement optical system of a corneal shape measuring apparatus.

FIG. 2 is a block diagram of an electric system of the apparatus.

FIG. 3 is a flowchart illustrating a measurement operation.

FIG. 4 is an explanatory diagram showing a state of an eye to be inspected when a spherical radius of curvature is obtained.

[Explanation of symbols]

 1 Light emitting diode 2 Collimating lens 3 Eye cornea 4 Imaging lens 5 Detection element

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 31, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

[0010]

EXAMPLES Examples of the present invention will be described below.
FIG. 1 is a diagram showing a measurement optical system of the corneal shape measuring apparatus.
Reference numerals 1a, 1b, 1c and 1d (1c and 1d are not shown) are point light sources composed of a light emitting diode, and are used as measurement light projected on the cornea of the eye to be inspected and are also fixed to the eye to be inspected. It emits a light flux in the red region to the near-infrared region so as to function as a target. The light emitted from the point light sources 1a and 1b is collimated.
Coating the lens 2a, is projected at an angle of α to the cornea 3 becomes parallel light flux by 2b, point source images 1a ',
I can do 1b '. Similarly, the point light source 1a is moved to the optical axis O by 90 degrees.
The light emitted from the point light sources 1c and 1d (not shown) at the rotated positions is collimating lenses 2c and 2 (not shown).
By d, it becomes a parallel light beam and is projected on the cornea 3 of the eye to be inspected at an angle of α to form unillustrated point light source images 3c ′ and 3d ′. The point light sources 1a, 1b, 1c, 1d are also used for the fixation target of the eye to be examined, and the details of the selection will be described later.

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (5)

[Claims] 1. A first index projection optical system for projecting a plurality of point indices onto a cornea of an eye to be examined at a predetermined projection angle, a detection optical system for detecting the position of the point indices projected on the cornea, and the detection optical system. A corneal shape measuring apparatus comprising means for obtaining the radius of curvature of the cornea based on the detection result by the above, wherein the point index is composed of a visible light flux, and a fixation that guides the fixation of the eye to be examined with the point index as the fixation point. Guidance means, a mode changeover switch for changing over to a mode for measuring a spherical radius of curvature, and a second index projection for projecting a second index for measuring a spherical radius of curvature orthogonal to the guiding direction. An optical system, and an arithmetic means for detecting the index image projected by the second index projection optical system by the detection optical system to obtain a spherical radius of curvature,
A corneal shape measuring apparatus comprising: 2. The cornea shape measuring device according to claim 1, wherein the first index projection optical system has a point index at the focal position of the lens. 3. The first index projection optical system according to claim 1 has four point light sources arranged in the vertical and horizontal directions of the eye to be inspected, and when the upper and lower point light sources are used as fixation indices A corneal shape measuring apparatus characterized in that, when the left and right point light sources are used as fixation indices, the upper and lower point light sources are used as second indices. 4. The fixation guidance means according to claim 1, wherein a selection means for selecting a fixation position, and a presentation index control means for separately indicating a point index of the selected fixation position and another point index are provided. A corneal shape measuring apparatus comprising: 5. A first index projection optical system for projecting an index on a cornea of an eye to be examined at a predetermined projection angle, a detection optical system for detecting the position of the point index projected on the cornea, and a detection result by the detection optical system. In the corneal shape measuring apparatus having means for obtaining the radius of curvature of the cornea based on the above, a mode changeover switch for changing over to a mode for measuring the abrupt radius of curvature, and a fixation of the eye to be inspected constituted by a visible light beam. A fixation guide means for guiding the eye, a second index projection optical system for projecting a second index for measuring a spherical radius of curvature orthogonal to the guide direction, and a selection means for selecting the fixation position. Control means for presenting the second index of the selected fixation position; computing means for detecting the index image projected by the second index projection optical system by the detection optical system to obtain a spherical radius of curvature; Based on the selection signal by the selection means A corneal shape measuring apparatus having means for automatically discriminating and displaying at which position the measured radius of curvature is measured.