JP4080183B2 - Anterior segment imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an anterior segment cross-section imaging apparatus that projects slit light onto a subject's eye and photographs a cross section of the anterior segment of the subject's eye.
[0002]
[Prior art]
2. Description of the Related Art An imaging device that projects slit light on an eye to be examined and obtains a cross-sectional image of the anterior eye portion of the eye to be examined by an imaging optical system having an optical axis that is inclined with respect to the optical axis of the slit light is known. By observing and analyzing the photographed cross-sectional image, it is possible to know the state of the anterior segment shape such as the lens thickness and the anterior chamber depth.
[0003]
By the way, changes in the shape of the anterior segment (particularly the crystalline lens and the depth of the anterior chamber) act on the visualization of an object. Clear vision is to change the refractive power of the eye to clarify the retinal image. It is generally known that when an object is nearby, the crystalline lens becomes thick and the anterior chamber depth becomes shallow.
[0004]
[Problems to be solved by the invention]
However, in the conventional device, since the fixation target presented to the eye to be examined was fixed at one distance, the change in the anterior segment shape due to the difference in the focal position when the subject eye changed the refractive power. It was not possible to evaluate.
[0005]
In view of the drawbacks of the above-described conventional apparatus, it is an object of the present invention to provide an anterior ocular segment photographing apparatus capable of accurately evaluating changes in the anterior ocular segment shape when the eye to be examined changes its refractive power.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is characterized by having the following configuration.
[0007]
(1) a slit projection optical system for projecting slit light onto the anterior segment of the eye to be examined, an anterior segment imaging optical system having a photographing optical axis inclined with respect to the slit projection optical axis, and photographing a slit projection cross section with an imaging device; And a fixation target presenting means for presenting the fixation target at different presentation distances, and presenting the fixation target at at least two different presentation distances by the fixation target presentation means. Display means for displaying contrast information of the anterior segment shape in each anterior segment cross-sectional image obtained in this manner.
(2) In the anterior segment cross-section imaging device according to (1), the display means displays each anterior segment cross-sectional image captured by presenting a fixation target at at least two different presentation distances on the same screen. It is a means.
(3) In the anterior segment cross-sectional imaging device of (1), for each anterior segment cross-sectional image obtained by presenting the fixation target at different presentation distances, the dimensions of the anterior segment shape including the lens thickness are determined. Analyzing means for analyzing is provided, and the display means is means for displaying an analysis result of the analyzing means.
[0008]
(4) In the anterior segment imaging apparatus of (3), a first correction unit that corrects distortion of an aspect ratio of a captured image by the anterior segment imaging optical system, and a captured image corrected by the first correction unit And a second correction unit that corrects the influence of distortion caused by the anterior segment translucent body by a ray tracing method, and the analysis unit calculates the lens thickness from the tissue position of the anterior segment translucent body by the second correction unit. It is characterized by analyzing the size of the anterior segment shape including.
(5) The anterior eye photographing optical system according to any one of (1) and (4) is a photographing optical system having a photographing lens and an image pickup element arranged on the basis of the Shine-Pluke principle. .
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an optical system of an apparatus according to the present invention.
[0010]
<Slit Projection Optical System> 1 is a reflecting mirror, 2 is a flash lamp for photographing, 3 is a condenser lens, 4 is a slit aperture stop, 5 is a light projection lens, and 6 is obliquely arranged on the optical axis L1 of the slit projection optical system. Dichroic mirror. The dichroic mirror 6 has a characteristic of transmitting most of visible light and reflecting part of infrared light.
[0011]
The luminous flux emitted from the flash lamp 2 is condensed by the condenser lens 3 to illuminate the slit aperture stop 4. The light beam limited to a narrow slit shape by the slit aperture stop 4 is transmitted through the light projecting lens 5 and the dichroic mirror 6 to project a slit image of the slit aperture stop 4. Thereby, the translucent body (cornea, anterior chamber, crystalline lens, etc.) of the anterior eye part of the eye to be examined is illuminated in the form of being light-cut by a white light source in the visible range.
[0012]
<Slit Section Imaging Optical System> L2 represents the imaging optical axis of the slit section imaging optical system. Reference numeral 7 denotes a photographing lens, 8 denotes an anamorphic lens for correcting image distortion, and 9 denotes a CCD camera. The optical axis L2 of the slit section photographing optical system is arranged with an inclination angle of 45 degrees with respect to the optical axis L1 of the slit projection optical system. The taking lens 7 is disposed to be inclined with respect to the optical axis L2 so as to satisfy the Shine-Pluke principle. That is, the intersection line between the extension of the optical section of the anterior segment of the eye to be examined by the slit illumination light and the extension of the imaging surface 9 a of the CCD camera 9 intersects with the extension line of the main plane of the photographing lens 7. With this optical arrangement, the cross-sectional image formed on the imaging surface 9a of the CCD camera 9 can have a depth of focus that is focused on substantially the entire cross-sectional image.
[0013]
Note that if the photographic lens 7 and the camera 9 are arranged so as to satisfy the Shine-Pluke principle, the aspect ratio of the photographic image does not become 1: 1, and the entire image is distorted. In order to correct this, in this embodiment, an anamorphic lens 8 is disposed between the photographing lens 7 and the camera 9 to correct the influence of photographing magnification based on the Shine-Pluke principle. Further, since the image distortion can be expressed by a well-known mathematical expression, it is possible to correct all the image distortion in the image processing process without using the anamorphic lens 8.
[0014]
<Fixation Target Presenting Optical System> 11a and 11b are a fixation light source for the left eye and a fixation light source for the right eye for presenting a fixation target for distance vision, and emits green light. Reference numeral 13 denotes a target plate for far vision. In the present embodiment, the target plate 13 is arranged at a position where the gaze distance of the eye to be examined is set to a distance of −2D (diopter). Further, in the average eyeball, the eye axis is deviated from the photographing optical axis by about 4 ° outward and by about 1 ° downward. A left eye fixation light source 11a and a right eye fixation light source 11b are provided in order to make the eye axis of the eye to be examined coincide with the imaging optical axis, and the captured image can be easily analyzed there. The plate 13 is provided with two pinholes.
[0015]
12a and 12b are a fixation light source for the left eye and a fixation light source for the right eye for presenting a fixation target for near vision, and red light is used so that it can be easily distinguished from the color of the fixation target for distance vision. I use something that emits. Reference numeral 14 denotes a target plate for near vision, which is arranged at a position where the gaze distance of the eye to be examined is a distance of −5D. Similarly to the target plate 13, the target plate 14 is provided with two pinholes so that the eye axis of the eye to be inspected can coincide with the imaging optical axis.
[0016]
15 is a half mirror, 17 is a dichroic mirror that reflects visible light and transmits near-infrared light, 18 is a projection lens, and 20 is a beam splitter. The target plate 13 or 14 is illuminated by individually lighting the light sources 11a, 11b, 12a, and 12b. The light beam from the target plate 13 or 14 is projected onto the eye to be examined through the half mirror 15, the dichroic mirror 17, the projection lens 18, the beam splitter 20, and the dichroic mirror 6.
[0017]
<Alignment optical system> 10 is a near-infrared light source for alignment for irradiating alignment light from the front (visual axis direction) of the eye to be examined, and 16 is a target plate. Reference numeral 17 denotes a dichroic mirror, and 18 denotes a projection lens. The light emitted from the light source 10 illuminates the target plate 16. The alignment light emitted from the target plate 16 passes through the dichroic mirror 17, is converted into a parallel light beam by the projection lens 18, and is then reflected by the beam splitter 20. Thereafter, the alignment light is reflected by the dichroic mirror 6 toward the eye E along the optical axis L1, and the image of the target plate 16 is formed at a position inside the eye by a distance half the corneal curvature radius from the corneal apex by reflection on the surface of the cornea. Form.
[0018]
<Alignment Observation Optical System> 21 is an imaging lens, and 23 is a front-view CCD camera having sensitivity in the infrared region. The cornea reflected light of the alignment light source 10 projected by the alignment optical system is reflected by the dichroic mirror 6 and then imaged by the CCD camera 23 via the beam splitter 20 and the imaging lens 21. Further, an anterior ocular segment image of the eye E illuminated by an anterior ocular segment illumination light source (not shown) is also captured by the CCD camera 23 through the same optical path.
[0019]
FIG. 2 is a diagram illustrating the configuration of the electrical system of the apparatus.
<Anterior Eye Section Imaging Unit> 100 is an anterior segment imaging unit in which the above-described optical system is arranged. The output signal from the CCD camera 9 is digitized by the A / D conversion circuit 50 and taken into the frame memory 52 in synchronization with the signal from the timing generator 51. The image signal taken into the frame memory 52 is converted into a video signal via the D / A conversion circuit 53 and then sent to the image switching circuit 54. The image switching circuit 54 receives a command signal from the control unit 60 and switches the image displayed on the display 55 between a photographed image from the CCD camera 23 and a photographed image from the CCD camera 9. Reference numeral 56 denotes an image synthesis circuit, which synthesizes various information displays generated by the display circuit 57 and the images from the CCD cameras 23 and 9 and displays them on the display 55, which is freeze-stored in the frame memory 52. The image is transferred to the image analysis unit 200 via the interface circuit 64 by input to the image transfer switch 63.
[0020]
<Image Analysis Unit> 201 is a computer unit that performs image processing on the cross-sectional image data input from the anterior segment cross-sectional imaging unit 100 and analyzes it, and includes a memory that stores and holds image data and an analysis program for image analysis. Have. A keyboard 202 and a mouse 203 for inputting operation instructions are connected to the computer unit 201. A color display 204 displays a cross-sectional image and an analysis result input from the anterior segment cross-section photographing unit 100, and 205 is a video printer. The computer unit 201 controls display on the display 204 and output to the video printer 205.
[0021]
The operation of the apparatus configured as described above will be described. The eye to be examined is fixed by switching between a near fixation target and a distant fixation target, and a cross-sectional image of the anterior segment is photographed in each fixation state. Here, a case where the left eye of the eye to be examined is imaged will be described.
[0022]
At the time of shooting, the left-eye switching switch 61 switches to left-eye shooting, and the switch 66 selects a near fixation target. Based on the signals from the switches 61 and 66, the control unit 60 lights the fixation light source 12a and projects the target plate 14 for near vision, so that the eye to be examined is fixed.
[0023]
When the alignment light source 10 is turned on, the light beam passes through the target plate 16, is collimated by the lens 18, and is projected onto the eye to be examined. The reflected image of the light beam on the cornea surface is taken by the CCD camera 23 through the lenses 24 and 21. A front anterior eye image of the eye to be examined is also captured by the camera 23 and displayed on the display 55. While observing the corneal reflection image displayed on the display 55, the examiner moves the imaging unit main body including the optical system to the left and right so as to have a predetermined relationship with the reticle formed electrically or optically on the display 55. Move up and down to align. The alignment in the optical axis direction is performed by moving the imaging unit main body in the front-rear direction so that the cornea reflection image is the smallest and clear image.
[0024]
When the alignment is completed by the above operation, when the photographing switch 62 is pressed and the photographing flash lamp 2 is turned on, a cross-sectional image of the anterior segment cut by the slit light is photographed by the CCD camera 9. The captured image is stored in the frame memory 52, and the display image on the display 55 is switched from the observation image to display the captured image. The anterior segment cross-sectional image stored in the frame memory 52 is transferred to the image analysis unit 200 by the image transfer switch 63.
[0025]
Subsequently, the examiner selects a far vision fixation target by using the switch 66, turns on the fixation light source 11a, and causes the eye to be examined to fix it. An anterior segment cross-sectional image is captured in the same procedure as that for the near vision imaging, and the image is transferred to the image analysis unit 200.
[0026]
Next, analysis of the captured image will be described. One is selected from the near-field and far-field cross-sectional images stored in the computer unit 201, and the selected cross-sectional image is displayed on the display 204.
[0027]
FIG. 3 shows a photographed cross-sectional image. From this cross-sectional image, the measurement axis M for measuring the anterior segment shape such as the corneal front radius of curvature, corneal thickness, anterior chamber depth, and lens thickness is determined. When three points (P1, P2, P3) along the front surface of the cornea are obtained by operating the mouse 203, the computer unit 201 approximates the front surface of the cornea in a circle and the measurement axis M passing through the center of curvature is drawn. Next, in order to obtain the thickness and depth of each part, the intersection point P4 of the rear surface of the cornea on the measurement axis M, the intersection point P5 of the front surface of the crystalline lens, and the intersection point P6 of the rear surface of the crystalline lens are sequentially designated with the mouse 203. Note that the points P1 to P3, the measurement axis M, and the intersections P4 to P6 on the front surface of the cornea may be automatically detected and determined by the computer unit 201 based on the density value (luminance value) of each layer of the captured image. good. When the analysis is executed after designating the measurement point in this way, the values of the corneal anterior curvature radius, the anterior chamber depth, and the lens thickness are measured. This is performed for each of the near vision cross-sectional image and the far vision cross-sectional image taken.
[0028]
The photographed image in this embodiment is an image in which the influence of the photographing magnification based on the Shine-Pluke principle is corrected by disposing the anamorphic lens 8. However, the anterior segment cross-sectional image not only passes through the imaging optical system, but part of it passes through the eyeball (anterior segment translucent body) and is distorted by refraction inside the eyeball. It is an apparent image. Therefore, in order to obtain the shape (position, thickness) inside the eyeball, it is necessary to correct the influence of the anterior segment translucent body in the middle. As a correction method, a ray tracing method (for example, Feder formula) can be used. By giving the apparent distance from the front of the cornea to each part and the refractive index of each part, the actual corneal thickness, anterior chamber Depth and lens thickness can be obtained. The corneal front radius of curvature is obtained from the captured image.
[0029]
FIG. 4 is a display example of the analysis result. A far-field cross-sectional image 310 is displayed on the left half of the screen, and a near-field cross-sectional image 320 is displayed on the same screen. Each image is divided in half by the measurement axis M. The positions of both images on the screen are superimposed with respect to the front surface of the crystalline lens on the measurement axis M. Such a display makes it easy to visually compare the difference in the shape of the anterior segment between far vision and near vision. From this figure, it can be seen that the depth of the anterior chamber is shallower and the lens is thicker in near vision than in far vision. Note that the lines 311, 312, 313, 321, 322, and 323 indicated by dotted lines on the screen indicate the actual corneal front surface position, lens front surface position, and lens rear surface position, respectively.
[0030]
In addition, the analysis results of the corneal anterior curvature radius, corneal thickness, anterior chamber depth and lens thickness are displayed numerically corresponding to the distance vision and near vision images, which changes between distance vision and near vision The difference in the anterior segment shape can be quantitatively evaluated. Further, as the anterior segment shape, the radius of curvature of the front surface of the crystalline lens is also obtained, and the result may be displayed together.
[0031]
In the above embodiment, the far vision fixation target is set to -2D, and the near vision fixation target is set to -5D. However, the presenting distance of each fixation target can be changed according to the refractive power of the eye to be examined. Anyway. In this case, the target plate 14 is moved in the optical axis direction using the target plate 14. Alternatively, a lens is inserted between the target plate 14 and the dichroic mirror 17, and this lens is moved in the optical axis direction so that the presenting distance of the fixation target is continuously variable. Further, the fixation target presentation distance may be changed more than two stages.
[0032]
In addition, the slit cross-section photographing optical system in the above-described embodiments has been described as an optical system that satisfies the Schein-Pluke principle, but in front of a portion (such as a crystalline lens or an anterior chamber depth) that is contrasted by the difference between far vision and near vision. Since it is only necessary to capture an eye image, a photo slit imaging optical system may be used.
[0033]
【The invention's effect】
As described above, according to the present invention, it is possible to accurately evaluate the anterior ocular segment shape that changes due to the difference in the focal position when the eye to be examined changes the refractive power.
[Brief description of the drawings]
FIG. 1 shows a schematic diagram of an optical system of an apparatus according to the present invention.
FIG. 2 is a diagram illustrating the configuration of an electric system of the apparatus.
FIG. 3 is a diagram illustrating determination of a measurement axis for a photographed cross-sectional image.
FIG. 4 is a diagram illustrating a display example of an analysis result.
[Explanation of symbols]
4 slit aperture stop 7 photographing lens 8 anamorphic lens 9 CCD camera 11a, 11b fixation light source 12a, 12b for far vision photographing fixation light source 13 target plate 14 visual target plate 18 projection lens 100 cross section of anterior eye part Imaging unit 200 Image analysis unit 201 Computer unit 204 Color display

Claims (5)

A slit projection optical system for projecting slit light onto the anterior ocular segment of the eye to be examined, an anterior ocular imaging optical system having an imaging optical axis inclined with respect to the slit projection optical axis, and imaging a slit projection cross section with an imaging device, A fixation target presenting means for presenting the fixation target at different presentation distances, and presenting the fixation target at at least two different presentation distances by the fixation target presenting means. An anterior ocular segment imaging apparatus comprising: display means for displaying contrast information of an anterior segment shape in each of the obtained anterior segment cross-sectional captured images. 2. The anterior segment cross-section photographing apparatus according to claim 1, wherein the display means displays the anterior segment cross-sectional images captured by presenting a fixation target at at least two different presenting distances side by side on the same screen. An anterior ocular segment imaging device. The anterior segment cross-sectional imaging apparatus according to claim 1, wherein each anterior segment cross-sectional image obtained by presenting a fixation target at different presentation distances is analyzed for analyzing an anterior segment shape dimension including a lens thickness. And the display means is means for displaying an analysis result of the analysis means. 4. The anterior segment imaging apparatus according to claim 3, further comprising: a first correction unit that corrects distortion of an aspect ratio of a captured image by the anterior segment imaging optical system; and a captured image corrected by the first correction unit. Second correction means for correcting the influence of distortion caused by the anterior segment translucent body by a ray tracing method, and the analysis means includes the lens thickness from the tissue position of the anterior segment translucent body by the second correction means. An anterior segment imaging device characterized by analyzing a dimension of a part shape. 5. The anterior ocular segment imaging optical system according to claim 1 or 4, wherein the anterior ocular segment imaging optical system is an imaging optical system having an imaging lens and an imaging element arranged on the basis of the Shine-Pluke principle. .

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