JPH05103761A - Eyeground inspecting device - Google Patents

Abstract

PURPOSE:To make a precise diagnosis of glaucoma by projecting the image of a retinal nerve fiber layer at a high contrast to easily find an abnormality of the fiber layer. CONSTITUTION:The light flux from a light source 1 is passed through a circularly polarizing plate 2, a lens 3, a bored mirror 4, and an objective lens 5 to light the eyeground Er of an eye E to be inspected with a circularly polarized light, and the reflected light from the eyeground Er is passed through the bored mirror 4, a lens 6, a circularly polarizing plate 7, a quick return mirror 8, a mirror 10, and a lens 11, and imaged on a telecamera 12. The projected image is once stored in a frame memory included in a signal processing part 13, and an eyeground image calculated by the signal processing part 13 is displayed on a television monitor 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fundus examination apparatus mainly used for ophthalmologic examination for glaucoma and the like.

[0002]

2. Description of the Related Art Conventionally, as a fundus examination apparatus used for diagnosing glaucoma and the like, there is known a system for illuminating the fundus using linearly polarized light regardless of the traveling direction of the retinal nerve fiber layer. .. Also, when visualizing the retinal nerve fiber layer,
It is also practiced to use a color filter or a linear polarization filter.

[0003]

Since the conventional method of illuminating the fundus using linearly polarized light has a direction dependency on the linearly polarized light, the test result tends to differ depending on the running direction of the retinal nerve fiber layer, and There is a problem that accurate results cannot be obtained. Further, when the retinal nerve fiber layer is imaged using a color filter or the like, a sufficiently clear image cannot be obtained, and it is irrelevant to the running direction of the retinal nerve fiber layer.
The method using a linear polarization filter has a problem that a good image cannot be obtained because it is an image obtained by simply combining a polarizer and an analyzer.

The object of the present invention is to accurately visualize the thickness distribution of the fiber layer without being influenced by the running direction of the nerve fiber of the retina or the reflection image of the fundus of the retina, thereby facilitating the abnormality of the retinal nerve fiber layer. An object of the present invention is to provide a fundus examination device that can be found.

[0005]

A fundus examination apparatus according to a first aspect of the invention for achieving the above object is an illumination system for illuminating a fundus with fundus illumination light by polarized light having components in a plurality of directions and a plurality of directions. And a fundus photographing means for photographing the fundus by the fundus photographing light with polarized light.

A fundus examination apparatus according to a second aspect of the present invention for achieving the above object is an illuminating means for illuminating a fundus with a fundus illumination light of linearly polarized light having a relationship of 45 ° with a running direction of a retinal nerve fiber layer. And a photographing means for photographing the fundus by the fundus photographing light by a linear polarizer perpendicular to and parallel to the fundus illumination light.

[0007]

In the fundus examination apparatus having the above-mentioned structure, since the refractive index of the retinal nerve fiber layer is different between the nerve fiber running direction and the direction perpendicular thereto, for example, circularly polarized light illuminating the fundus becomes elliptically polarized light and is emitted. The distribution of the thickness of the fiber layer is visualized by obtaining the phase distribution related to the thickness of the fiber layer from the ellipticity of the elliptically polarized light by using the phenomenon of eclipse.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiments. FIG. 1 shows a first embodiment, 1 is a light source, and a circularly polarizing plate 2, a lens 3, a perforated mirror 4, and an objective lens 5 are provided in an optical path from the light source 1 to an eye E to be inspected. There is. Behind the perforated mirror 4, a lens 6, a circularly polarizing plate 7, a quick return mirror 8 and a film 9 are sequentially arranged. Further, in the reflecting direction of the quick return mirror 8, the mirror 10, the lens 11, the television camera 12
Is provided, and the output of the TV camera 12 is the signal processing unit 13.
Is connected to the television monitor 14 via.

The luminous flux emitted from the light source 1 is a circular polarization plate 2,
Through the lens 3, the perforated mirror 4 and the objective lens 5,
The fundus Er of the eye E to be examined is illuminated. The reflected image on the fundus Er passes through the objective lens 5, the perforated mirror 4, the lens 6, the circularly polarizing plate 7, the quick return mirror 8, the mirror 10 and the lens 11 to form a fundus image on the television camera 12. This image is temporarily stored in the frame memory built in the signal processing unit 13, and the fundus image calculated by the signal processing unit 13 is displayed on the television monitor 14. In the case of capturing an image on the film 9, the light flux is guided to the film 9 by raising the quick return mirror 8.

FIG. 2 exemplifies the fundus image projected on the television monitor 14, in which nerve fibers originate from the nipple A, run along the blood vessel B and gather at the macula C. Although the fiber layer is almost transparent, the refractive index is different between the running direction and the direction perpendicular to the running direction and has birefringence. Therefore, when illuminated with circularly polarized light, it generally comes out as elliptically polarized light. The direction of this ellipse is 45 ° with respect to the running direction of the nerve fiber, and the direction differs depending on the fundus position, and the direction of the ellipse also differs at points P and Q in FIG. However, if the fiber layers have the same thickness, the phase difference is the same, so the ellipticity depends only on the thickness. When the intraocular pressure rises and the defect zone K occurs, the birefringence of that portion disappears, so that no ellipse occurs. Theoretically, the transmitted light disappears when the circularly polarizing plates in the same direction are used as the analyzer, but in reality, since various components are mixed in the retina reflection, the transmitted light does not disappear.

FIG. 3 shows the state of retinal reflection at the fundus Er, and the illumination light I is first reflected at the boundary F between the vitreous body and the retina D. Since this is specular reflection, the polarized light is maintained, and since it has not passed through the retina D yet, it remains circularly polarized light. Next, the light is reflected at the boundary between the retina D and the pigment epithelium layer G. This is also specular reflection, and the polarization is maintained, but it becomes an ellipse as much as it passes the retina D. Further, it is diffusely reflected by the pigment epithelium layer G. This amount is the largest, but only the component reflected in the pupil direction contributes to the image, so it is not necessarily large compared to the former two. To make an image of the fiber layer, you can take a picture using a circularly polarizing plate as a polarizer and analyzer, but the contrast cannot be so high. In order to increase the contrast, the circularly polarizing plate 7 shown in FIG. 1 may be taken in and out as shown by an arrow to store an image, and the calculation may be performed using the image.

Here, the reflectances of the front and back surfaces of the retina D are a and b, respectively, the reflectance of the pigment epithelium layer G is c, the incident light quantity is Ii,
Assuming that the amount of reflected light is Io, the reflectances a and b are sufficiently smaller than 1, so that the following equation (1) is established. Io = a ・ Ii + b ・ Ii + c ・ Ii ... (1)

Here, Io is the output at each point when there is no analyzer. The reflectance a can be considered to be substantially constant at each point on the fundus Er, and the reflectance b can be considered to be substantially constant as well. However, the reflectance c of the pigment epithelium layer G differs depending on the position.

When a circularly polarizing plate of the same direction is placed in the light receiving system to receive the reflected light, the light quantity If is expressed by the following equation (2).
The first term a · Ii in the above equation (1) disappears as circularly polarized light in the opposite direction due to reflection, and the second term b · Ii produces transmitted light by the amount corresponding to the ellipse. This depends on the phase difference δ. Also,
The third term becomes 1/2. That is, If = f (δ) · b · Ii + (1/2) c · Ii ... (2)

From the equations (1) and (2), the following equation (3) is obtained. f (δ) = (2If−Io) / 2Ii · b− (a + b) / 2b ... (3)

Therefore, if f (δ) is calculated at each point of the fundus Er, the phase distribution can be known. If the screen is composed of f (δ) in the equation (3), the state of the nerve fiber can be displayed as an image, which is particularly effective for the diagnosis of glaucoma. Approximately,
Although the reflectances of the respective points are independent, the fundus pattern remains in reality without being completely removed, so that the positional relationship may be understood.

The reflecting members such as the perforated mirror 4, the quick return mirror 8 and the mirror 10 shown in FIG. 1 preferably have a non-polarizing reflection surface so that the polarization is not disturbed, and the wavelength band is appropriately used. Narrowing down improves efficiency.

Needless to say, the circularly polarizing plates 2 and 7 can be replaced with other circularly polarizing elements. In the case of this example, the phase distribution uniformly related to the thickness of the fiber layer on the fundus of the eye is obtained regardless of the running direction of the nerve fiber, and the phase distribution does not depend on the reflectance of each point of the fundus Er. Therefore, it is possible to easily detect an abnormality of the retinal nerve fiber layer.

FIG. 4 shows a second embodiment, and the same reference numerals as those in FIG. 1 represent the same members. In this embodiment, a rotatable linear polarizing plate 21 and an image sensor 22 are provided behind the lens 6.
A television camera 23 including is arranged. The linear polarization plate 21 is driven by a step motor 25 via a gear 24 as shown in FIG. Further, the signal processing unit 26 includes a television camera 23, a step motor 25,
It is connected to the television monitor 27.

Also in this embodiment, the light flux from the light source 1 illuminates the fundus Er of the eye E through the circularly polarizing plate 2, the lens 3, the perforated mirror 4 and the objective lens 5. Since the fiber layer in the retina of the fundus Er has the birefringence as described above, when illuminated by the circularly polarized light J as shown in FIG. 6, the elliptically polarized light K generally appears as shown in FIG. Come on. 6 and 7, S indicates the running direction of the fiber layer.
The circularly polarized light J can be regarded as having a phase difference of 90 degrees between the traveling direction S and the linearly polarized light in the direction perpendicular to the traveling direction S. Therefore, if the difference becomes 0 degree through the retina, the circularly polarized light J becomes 45 degrees in the traveling direction S. It becomes linearly polarized light, and elliptically polarized light K between them. Since the phase difference is proportional to the difference in refractive power in the parallel and vertical directions and the thickness, if the difference in refractive power is assumed to be constant, it is proportional to only the thickness. Therefore, the phase difference may be obtained from the ellipticity of the elliptically polarized light K. As shown in FIG. 7, the analysis of the elliptically polarized light K is performed by the three-direction oblique shadows P1, P2,
It can be calculated from P3.

Now, in FIG. 4, the reflected light from the fundus Er passes through the perforated mirror 4, the lens 6 and the linear polarizing plate 21 to form a fundus image on the image pickup device 22, and the television camera 23.
Is visualized in. Here, the linearly polarizing plate 21 is rotated by 60 degrees by the step motor 25 to perform imaging three times, the imaging is taken into the signal processing unit 26, and the phase difference at each point of the fundus Er is obtained by calculation. The result is displayed on the television monitor 27. If this phase difference is represented by the strength of the signal, the defective portion of the retinal nerve fiber layer can be displayed by shading. The running direction of the nerve fiber is not constant, but circularly polarized light is desirable because it has no directionality. However, the direction of the formed ellipse varies depending on the traveling direction, but the problem is the phase difference, which is determined not by the elliptic direction but by the ellipticity.

FIG. 8 shows another embodiment. Fundus
When the narrow range of Er is photographed, the running direction of the fiber layer is considered to be constant, and it is illuminated with linearly polarized light of 45 degrees, and the light is received in the directions parallel and perpendicular to that direction, and the position is determined from the difference between them. The phase difference can be calculated. In FIG. 8, the light source 30
A linear polarization plate 31, a light splitting member 32 having no polarization characteristic, and an objective lens 33 are provided in the optical path of the light path, and a light splitting member 34 having no polarization property and a linear polarization plate 31 are provided behind the light splitting member 32. A polarizing plate 35 and a television camera 36 having parallel polarization directions are arranged. In the reflection direction of the light splitting member 34, a linear polarization plate 31, a polarization plate 35 having a polarization direction perpendicular to each other, and a TV camera 38 are provided, and outputs of the TV cameras 36 and 38 are connected to a signal processing unit 39.

In this case, the light flux from the light source 30 passes through the linear polarizing plate 31, the light splitting member 32, and the objective lens 33 to illuminate the fundus Er of the eye E to be examined, and the reflected light from the fundus Er is split into the light splitting member 34. The image is divided into a polarizing plate 35 and a polarizing plate 35 by means of, and the respective images are taken into the television cameras 36 and 38, and the signal processing unit 39 obtains a phase difference distribution from the difference and visualizes it.
The display in this case may be displayed on a color television monitor in an appropriate similar color in addition to the light and shade.

FIG. 9 shows the linearly polarized light M of the illumination system, and FIG. 10 shows the elliptically polarized light N of the reflected light. Since polarized components Q1 and Q2 are mixed at the time of fundus reflection at the time of detection to reduce the contrast of imaging, Q1 / Q2 of each pixel is obtained, and the minimum value of Q1 / Q2 is set to (Q1 / Q2) min When Q1 / Q2- (Q1 / Q2) min
Is calculated and displayed, there is an effect of removing the non-polarized component, and it is possible to obtain a phase image with high contrast.

[0025]

As described above, since the fundus examination apparatus according to the present invention can visualize the retinal nerve fiber layer with high contrast, abnormality of the fiber layer can be easily detected,
It is especially effective in diagnosing glaucoma. In addition, it is possible to obtain the phase distribution uniformly related to the fiber layer thickness on the fundus irrespective of the running direction of the nerve fiber, and it is possible to obtain the phase distribution without depending on the reflectance at each fundus point. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is an explanatory diagram of a fundus image.

FIG. 3 is an explanatory diagram of a reflection state on the retina.

FIG. 4 is a configuration diagram of a second embodiment.

FIG. 5 is a front view of a linear polarizing plate viewed from the optical axis direction.

FIG. 6 is an explanatory diagram of circularly polarized light.

FIG. 7 is an explanatory diagram of elliptically polarized light.

FIG. 8 is a configuration diagram of a third embodiment.

FIG. 9 is an explanatory diagram of linearly polarized light of an illumination system.

FIG. 10 is an explanatory diagram of elliptically polarized light of reflected light.

[Explanation of symbols]

 1 light source 2, 7 circularly polarizing plate 4 perforated mirror 8 quick return mirror 9 film 12, 36, 38 TV camera 13, 26, 39 signal processing unit 14, 27 TV monitor 21, 31 linear polarizing plate 23 step motor 32, 34 Light splitting member 35, 37 Polarizing plate

Claims (4)

[Claims] 1. An illumination system for illuminating a fundus with a fundus illumination light of polarized light having a plurality of directions of components, and a fundus photographing unit for photographing a fundus with a fundus photographing light of polarized light having a plurality of directions of components. A fundus examination apparatus characterized by: 2. The fundus examination apparatus according to claim 1, wherein the fundus illumination light and the fundus photographing light are circularly polarized light. 3. The television camera is used as the fundus photographing means,
The fundus examination apparatus according to claim 1, further comprising a frame memory that temporarily stores an image captured by the television camera and a unit that analyzes a retinal nerve fiber layer from images captured in a plurality of polarization states. 4. Illuminating means for illuminating the fundus with a fundus illumination light of linearly polarized light having a relationship of 45 ° with the running direction of the retinal nerve fiber layer, and fundus photographing light by a linear polarizer perpendicular and parallel to the fundus illumination light. A fundus examination apparatus, comprising: