JP2021000177A - Ophthalmologic apparatus - Google Patents

Abstract

To provide an ophthalmologic apparatus which can acquire a fundus image with less influence even when opacity exists in a vitreous body of a subject's eye.SOLUTION: An ophthalmologic apparatus comprises: fundus imaging means which images a fundus of a subject's eye as a moving image while irradiating the fundus of the subject's eye with the illumination light; and addition means which performs addition average processing by matching feature points in plural frames of the fundus image acquired by the fundus imaging means to remove a vitreous body opacity region from the fundus image.SELECTED DRAWING: Figure 4

Description

The present invention relates to an ophthalmic apparatus for photographing the fundus of a subject's eye.

Conventionally, an imaging device for photographing the fundus of the subject's eye has been known. For example, an imaging means for obtaining a fundus image of the subject's eye, a turbidity information acquisition means for acquiring opacity information of an intermediate translucent body such as a vitreous body in the fundus image, and a storage means for associating the fundus image with the turbidity information. There is a fundus photography apparatus including a memory control means for storing and an image processing means for performing contrast adjustment according to the degree of turbidity based on turbidity information as image processing (see, for example, Patent Document 1). According to this fundus photography apparatus, opacity of the vitreous body of the subject's eye is less likely to affect the image quality of the fundus image, and the fundus image can be preferably diagnosed.

JP-A-2017-99718

By the way, one of the eye diseases is a symptom called floater. Floater is a symptom in which black dots, strings, or thin clouds are visible in the field of vision, especially in bright places due to the opacity of the vitreous. Even if the eyeball is moved, the foreign object image moves while swaying in various directions while changing the location according to the movement. These symptoms can be felt even when undergoing an ophthalmic examination that looks at something like a light source, but especially in an ophthalmic examination that receives laser light on the fundus, you can notice the opacity of the vitreous body quite clearly. ..

On the other hand, in an ophthalmologic examination apparatus using a laser, a shadow of opacity of the vitreous body is observed on the photographed fundus image. Such vitreous opacity becomes an artifact in fundus observation.

Therefore, it is an object of the present invention to provide an ophthalmic apparatus capable of acquiring a fundus image having less influence on the vitreous body of the subject's eye even if the vitreous body is opaque.

In order to solve the above problems, the means adopted by the present invention include a fundus photography means for photographing the fundus of the subject's eye as a moving image while irradiating the fundus of the subject's eye with illumination light, and the fundus photography. An ophthalmologic apparatus comprising: an addition means for removing a vitreous opaque region from the fundus image by matching feature points in a plurality of frames of the fundus image acquired by the means and performing addition averaging processing. Is.

In addition, the ophthalmic apparatus may include a turbid region extraction means for extracting the vitreous turbid region by performing difference processing on two fundus images having different addition numbers obtained by the addition means.

In addition, the ophthalmic apparatus may include a turbid region evaluation means that three-dimensionally displays the size and brightness of the region specified by the turbid region extraction means in relation to the fundus image.

Further, the ophthalmic apparatus further includes an optotype presenting means for projecting an optotype onto the fundus, and when the optotype passes through the vitreous opaque region, the amount of light of the optotype according to the degree of opacity in the region. May be increased.

Further, the ophthalmic apparatus may include an auto-tracking means for calculating the amount of deviation for each frame by using the position information of the featured portion of the fundus image.

According to the present invention, since the vitreous opaque region in the acquired fundus image can be removed from the fundus image as an artifact, fundus observation can be preferably performed.

It is a schematic block diagram of the ophthalmic apparatus which concerns on this Example. It is a block diagram of the control system of the ophthalmic apparatus which concerns on this Example. It is a schematic diagram of the fundus image explaining auto-tracking. It is a schematic diagram of the fundus image including the vitreous opaque region. It is a schematic diagram of the fundus image explaining the addition process. It is a schematic diagram of the fundus image explaining the difference processing.

Hereinafter, an embodiment of the ophthalmic apparatus according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments, and various modifications and combinations are possible within the scope of the claims and the scope of the embodiments, and these modifications and combinations are also possible. It is included in the scope of rights.

As shown in FIG. 1, the ophthalmologic apparatus includes a fundus image acquisition optical system 10 that acquires a fundus image by scanning a laser beam on the fundus of the subject eye E as a fundus imaging means. Further, as the optotype presenting means, the optotype optical system 20 for presenting the optotype, the background, and the fixation lamp to the fundus of the subject eye E by a DLP (registered trademark) (Digital Light Processing) type projector is provided. ..

[Fundus photography]
As a fundus photographing means, a general scanning laser optical probe (SLO) is used. SLO illuminates a sufficiently small area on the fundus with laser light, scans it at high speed, captures each reflection with a high-sensitivity detector, and reconstructs the entire image of the scanned area on the monitor. is there. The moving image of the fundus acquired by this is used for image processing described later.

The fundus image acquisition optical system 10 uses a line laser light source 40 that emits line-shaped light. The line-shaped light emitted from the line laser light source 40 is reflected by the mirror 41, passes through a hole formed in the center of the hole mirror 42, and is irradiated to the scanner 43. In this embodiment, the scanner 43 is a galvanometer, and is reflected in a predetermined direction by a mirror (galvanometer mirror) 44 mounted on the galvanometer. Then, it passes through the lenses 50 and 51, and is irradiated to the fundus of the subject eye E through the dichroic mirror 52 and the lens 53. The reflected light from the fundus of the subject eye E is reflected by the hole mirror 42 through the lens 53, the dichroic mirror 52, the lenses 50, 51, and the scanner 43. Then, it passes through the lens 54 and is detected by the line sensor 60. The light intensity information detected by the line sensor 60 is converted into a digital signal and input to the control device 80.

[Means for presenting visual targets]
One of the purposes of presenting the optotype is to guide the subject's eye in the direction of fixation. The optotype optical system 20 uses a DLP projector 70 as a light source to present (project) a predetermined optotype at a predetermined position on the fundus of the subject eye E. The DLP projector 70 creates a presentation pattern by variably controlling the angles of micron-sized micromirrors laid out in a matrix. That is, the tilt angle of each micromirror is turned on / off. When it is on, light is projected through the lens, and when it is off, the light is absorbed by the light absorption plate. Therefore, by controlling the tilt angle of each micromirror on / off, it is possible to form and present an optotype of an arbitrary shape and size at an arbitrary position on the fundus. In addition, the target to be presented can form not only symbols but also characters, and the number of characters can be freely changed. In addition to the optotype, the DLP projector 70 can also project a fixation lamp and a background for the subject to gaze for the purpose of fixing the subject's eyes. Further, since the DLP projector 70 can change the brightness by changing the ratio of the on / off time of each micromirror, it is possible to present the optotype on a black background on a white background.

The light emitted from the DLP projector 70 passes through the lens 71, is reflected by the mirror 72, is reflected by the dichroic mirror 52 through the lens 73, and is applied to the fundus of the subject eye E.

Next, the configuration of the control system of the ophthalmic apparatus of this embodiment will be described. As shown in FIG. 2, the ophthalmic apparatus is controlled by the control device 80. The control device 80 is composed of a microcomputer (microprocessor) including a CPU, a ROM, a RAM, and the like. A DLP projector 70, a scanner 43, a line sensor 60, a monitor 82 of a touch panel 81, and a memory 83 are connected to the control device 80.

The control device 80 scans the line-shaped light on the fundus of the subject eye E by controlling the driving of the scanner 43. That is, in this embodiment, since the light output from the line laser light source 40 extends in a line shape in the X direction, the control device 80 moves the scanner 43 in the Y direction (direction orthogonal to the paper surface of FIG. 1). Drive control and scan light. Further, an electric signal corresponding to the intensity of the reflected light detected line by line by the line sensor 60 is input to the control device 80, and a two-dimensional fundus image 100 of the subject eye E is generated from the electric signals of the plurality of lines. , The generated fundus image 100 is displayed on the monitor 82. In this embodiment, the line-shaped light output from the line laser light source 40 is scanned in the Y direction, but the spot-shaped light may be scanned in the XY direction.

The operation when the subject's eye is photographed by using the ophthalmic apparatus having the above configuration will be described.

The examiner operates an operating member such as a joystick (not shown) to align the subject eye E with the device. When the alignment is completed, the luminous flux of the line laser light source 40 is applied to the fundus of the subject eye E, the control device 80 drives the scanner 43, and the acquisition of the fundus image 100 is started. In this embodiment, the line sensor 60 continuously acquires the fundus image 100 of the subject eye E and displays it on the monitor 82 as a real-time moving image.

[Auto tracking means]
As shown in FIG. 3, in the fundus motion image 100 of about 20 to 30 frames / sec obtained by the fundus photography means, the deviation amount is calculated for each frame by designating the characteristic parts such as the position of the optic nerve head and the running position of the blood vessel. To do. Specifically, the amount of deviation is obtained from the position where the sum of the difference values is minimized by shifting Δx and Δy. Then, in order to speed up the calculation, rough detection is performed using the thinned reduced image, and detailed detection is performed on the image that is not thinned out. Further, in order to obtain accuracy in the thinned-out state, the thinned-out image is created not by simple thinning out in pixel units but by the minimum value in the block represented by the thinned-out pixel.

[Addition means]
As shown in FIG. 4A, when the vitreous body is opaque, the shadow of the opacity appears as blackish artifact 110 in the fundus image. Since the state of the blood vessel arrangement of the fundus does not change during the fundus motion image acquisition, the fundus image which is the base image without the inclusion of artifacts unrelated to the fundus is acquired by performing the addition process. When performing the addition process, a process of matching feature points such as blood vessel arrangement for each frame is also performed. Since vitreous opacity is linked to fixation, if the number of additions is large while fixation is slightly moving, the artifact disappears from the final addition image as shown in FIG. 4B. Here, 512 frames are added.

[Muddy area extraction means]
When less addition processing is performed than the above addition image, as shown in FIG. 5, it is possible to obtain a fundus image 100 in which only high frequency noise is removed while leaving vitreous opacity. Here, 32 frames are added.

Then, the difference processing is performed between the 512 frames addition image and the 32 frames addition image. Here, the gray level is converted to 127 with a difference value of 0, and the + side is expressed whitish and the-side is expressed blackish. Then, as shown in FIG. 6, an image 200 in which only the vitreous turbid region 210 is extracted can be obtained.

The problem at the time of difference processing is dealt with individually instead of the simple difference between matching pixels.
1) Rotation for each frame If the subject's face is fixed, correction is not necessary, but the method is to determine the degree of agreement for each Δθ.
2) Difference in enlargement ratio for each frame If the subject's face is fixed, correction is not necessary, but the method is to determine the degree of agreement for each Δ enlargement ratio.
Regarding the above two points, as a simple method, the one that minimizes the difference value within the number of peripheral pixels for each (x, y) is adopted.

By performing the fundus image processing as described above, the vitreous opaque region is extracted, and the following uses become possible.

[Evaluation of vitreous turbid region]
The size and brightness of the identified areas correlate with the degree of vitreous opacity, and they are displayed three-dimensionally in relation to the fundus image. Specifically, the brightness of the vitreous opaque region represents the degree of opacity, and the sharpness of the edge of the vitreous opaque region roughly correlates with the distance from the fundus, so that 3D mapping display can be performed. Actually, distance display (for example, mm) cannot be performed without some calibration, but normalization is performed using the brightness of the fundus image, and differential values are used for edges to make 3D in a dimensionless quantity. Since it is possible to perform the conversion, a useful display can be performed. In addition, from the state in which the vitreous opaque region fluctuates, the speed of movement and the interlocking with the movement of the eyeball can be displayed as evaluation values.

[Correction of fundus image]
Remove the shadow of vitreous opacity from images that have not been added or have not been added sufficiently. As described above, if a large number of frames are added, the vitreous opacity is corrected in the direction of disappearing, and the corrected image may be treated as a fundus image. However, for some reason, it may be necessary to handle an image (target image) having a small number of single frames or addition frames. In this case, vitreous turbidity remains on the image. As a premise, if there is a case where the turbid region can be extracted by the above-mentioned difference processing by sufficient addition processing somewhere during measurement, this region is not deformed or the appearance amount does not change in a short time. , The position of the turbid region on the target image was specified by calculating the position of the high degree of correlation between the turbid region extracted image and the target image, and the turbid region was removed by performing the difference processing at that position. A fundus image can be obtained.

[Adjustment of projected light]
Not limited to lasers, when projecting light with a wavelength different from that of fundus photography onto the fundus using a DLP projector or the like (for example, giving light stimulation of a pattern or spot), when passing through a vitreous opaque region, Increase the strength according to the degree of the area. Specifically, it is assumed that the subject is shown some kind of image, the test pattern of the visual acuity test, or the Randold ring image. In this case, if there is vitreous turbidity, the brightness of the pixel to be displayed decreases and it becomes difficult to see, so that it can be brightened to make it easier to see.

10 Fundus image acquisition optical system (fundus imaging means)
20 Optical system for optotypes (means for presenting optotypes)

Claims (5)

Fundus photography means for photographing the fundus of the subject's eye as a moving image while irradiating the fundus of the subject's eye with illumination light.
It is characterized by comprising an addition means for removing a vitreous opaque region from the fundus image by matching feature points in a plurality of frames of the fundus image acquired by the fundus photography means and performing addition averaging processing. Ophthalmic device. The ophthalmologic apparatus according to claim 1, further comprising a turbid region extraction means for extracting the vitreous opaque region by performing differential processing on two fundus images having different numbers of additions obtained by the addition means. The ophthalmologic apparatus according to claim 1 or 2, further comprising a turbid region evaluation means for three-dimensionally displaying the size and brightness of a region specified by the turbid region extraction means in relation to the fundus image. .. It is further provided with an optotype presenting means for projecting an optotype onto the fundus, and when the optotype passes through the vitreous opaque region, the amount of light of the optotype is increased according to the degree of opacity in the region. The ophthalmologic apparatus according to any one of claims 1 to 3. The ophthalmologic apparatus according to any one of claims 1 to 4, further comprising an auto-tracking means for calculating a deviation amount for each frame using the position information of a characteristic portion of the fundus image.

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