JP5014593B2 - Ophthalmic measuring device - Google Patents

Description

  The present invention relates to an ophthalmologic measurement apparatus, and more particularly to an ophthalmologic measurement apparatus that measures the fundus of a subject's eye.

  There is a demand to look at the fundus photograph taken with fluorescence to determine the size of the lesion and the distance on the retina from the lesion to the nipple. This is known as photodynamic therapy (PDT therapy) in which a lesion is irradiated with a laser beam in the form of a spot to treat age-related macular degeneration. In order to form an appropriate laser spot, This is because an actual distance is required. When treating a lesion by irradiating it with spot light, it is a problem whether the spot size of the light beam to be irradiated is too large or too small. It is required to form with. Generally, it is said that a spot size having a maximum lesion diameter of +1 mm is optimal. For that purpose, the maximum diameter of the lesioned part must be accurately measured in advance, and the size of the lesioned part maximum diameter + 1 mm must be set as the light spot size.

  In this way, it is necessary to recognize the position of the lesioned part on the retina and accurately determine the distance of that part. For detecting the position of a lesioned part, the luminance changes in the lesioned part. For example, a technique (Patent Document 1) that extracts the contour of an image based on the luminance is used.

  In addition, the nipple and the pale part are extracted from the fundus image based on the luminance (Patent Document 2), and the average luminance of the nipple is obtained and the lesion is identified from the average luminance. (Patent Document 3).

In addition, in order to accurately measure the distance of the lesion on the retina, the positional information by the focus lens position detection mechanism, the eye refractive power measured earlier, the axial length of the eye measured separately, It is necessary to obtain a distance between predetermined points on the actual retina from the retina image using a part or all (usually two) of the three pieces of information of the measured corneal curvature.
JP 55-49778 A JP-A-6-1225876 JP 2003-310555 A

  However, conventionally, it is difficult to specify the lesion on the retina from the fundus image, and it is not easy to determine the exact distance on the retina of the lesion, so it is not possible to perform appropriate photodynamic therapy. There was a problem.

  The present invention has been made to solve such problems, and it is an object of the present invention to provide an ophthalmologic measurement apparatus that makes it easy to specify a predetermined area of a fundus image and enables accurate measurement of the area. Let it be an issue.

The ophthalmic measuring apparatus of the present invention is
Display means for displaying an electronic image of the fundus photographed with fluorescence;
Designation means for designating the outer edge of the lesion on the image displayed on the display means;
Wherein the luminance value of the outer edge portion of the lesion that is specified by means a threshold, it possesses a region extracting means for extracting a region of high brightness values than the threshold value, and
Further, when a plurality of regions having a luminance value higher than the threshold value are extracted, only the region including the outer edge of the designated lesion is selected, and the outer periphery of the region including the outer edge of the selected lesion is selected. It has the outer periphery acquisition means to obtain, It is characterized by the above-mentioned.

  In the present invention, a luminance value increasing / decreasing means for increasing / decreasing the luminance value of the designated point is provided to change the size of the extracted area.

In the present invention, since it is possible to extract a region having a higher luminance than the luminance value of the outer edge point specified by the user, it is possible to easily specify a region of the lesion on the retina having a higher luminance than other locations. Can be specified. In addition, since the size of the specified area changes by increasing or decreasing the luminance value (brightness threshold value) of the specified point, the user specifies the most likely area as the lesion while viewing the screen. It becomes possible.

  Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

  In FIG. 1, a fundus camera 10 is shown as a schematic block diagram, and this fundus camera 10 forms a fluorescent image of the fundus Er of the illuminated eye E on an image sensor 11 composed of a CCD or the like. To do. The fundus image captured by the imaging device 11 is input to the A / D converter 21 of the image processing device 20, where the fundus image is converted into a digital signal in accordance with the A / D resolution. And stored in the image memory 22.

  The image processing apparatus 20 includes a CPU 23 that performs various data processing and calculations. In the present invention, the CPU 23 is a region extraction unit 23a, an outer periphery acquisition unit 23b, a minimum circle acquisition unit 23c, an area, and a diameter calculation unit. It fulfills the function of 23d and executes a program stored in the ROM 25 to process the fundus image as will be described later. During this image processing, the RAM 24 is used as a working memory for storing input data and processed data.

  The image processing apparatus 20 can be connected to the recording apparatus 30, and can record and store the fundus image captured by the fundus camera 10 and stored in the image memory 22 in the recording apparatus 30. Further, the fundus image recorded in the recording device 30 can be taken into the image memory 22 and subjected to the same image processing as the fundus image from the image sensor 11.

  The image processing apparatus 20 is connected to a display means including a monitor 31. The monitor 31 displays a fundus image stored in the image memory 22, a processed fundus image, and a mouse 32. A predetermined area or a predetermined point of the image displayed on the monitor 31 can be arbitrarily specified by a specifying means such as. Further, a luminance value increasing / decreasing means 33 for increasing / decreasing the luminance value (luminance threshold) of the image of the point on the screen designated by the mouse 32 is provided. Further, the image processing apparatus 20 is provided with input means 34 such as a keyboard and a mouse, and various data can be input to the image processing apparatus 20.

  The flow of processing for measuring the size of a predetermined region on the retina of the eye to be examined, that is, the size of the lesioned part, will be described.

  The fundus camera 10 fluoresces the fundus Er of the eye E with the image sensor 11, converts it to a digital signal with the A / D converter 21, stores it in the image memory 22, and displays the fundus image on the monitor 31. Then, image processing is performed. The processed image may be a fundus image loaded by loading a fluorescently photographed fundus image stored in the recording device 30 into the image memory 22.

  The fundus image on the monitor 31 captured or recorded is shown in FIG. 2, and a dialog box 50 as shown in the upper left of FIG. 3A is displayed on the monitor 31 at this time. As shown in FIG. 4, the dialog box 50 includes the ID number of the eye to be examined related to the fundus image, eye information such as the left eye (L) and right eye (R), and information on the fundus camera 10 ( The parameters of the eye to be examined such as the refracting power of the eye to be examined, the corneal curvature (kerato), and the axial length are displayed.

  Here, the manufacturer name, model name, angle of view, and photographing mask size of the fundus camera are stored as a file for each fundus camera in the device list 26. Therefore, when the fundus camera 10 photographs the fundus, These data relating to 10 are read from the device list 26 and automatically entered in the items of the dialog box 50. If these items are not yet input in the fundus image read from the recording device 30, the user inputs them via the input unit 34.

  Thus, when the fundus camera is specified and the above specifications are known, the magnification conversion table 27 is loaded, and the magnification conversion value is obtained.

  In addition, an eye parameter to be examined such as refractive power of the test eye, corneal curvature (kerato), or axial length is input. Preferably, the default value is displayed and changed by the user. Only one of the corneal curvature (kerato) and the axial length can be input.

  The imaging mask defines the imaging range of the fundus, and the images in the imaging mask 31a are the fundus image in FIGS. The imaging mask 31a is automatically detected by a known algorithm for obtaining the minimum circle, a circle matching the imaging mask is drawn, and the number of pixels of the diameter d (FIG. 2A) is stored.

  The final magnification of the image is obtained from the number of pixels corresponding to the obtained photographing mask diameter d, the mask size of the photographing mask designated in the dialog 50, and the converted value obtained from the magnification conversion table 27.

  Subsequently, in order to measure the distance between the laser light irradiation region and the nipple edge, the user designates the nipple edge prior to the designation of the lesion. As the designation method, the user designates 3 to 4 points on the macular side of the nipple 40 and draws an arc by software, or displays a vertically long ellipse (standard nipple size) on the screen, A method where the user drags the ellipse and moves it to fit the nipple edge is conceivable.

  Subsequently, the lesioned part 41 is specified. Therefore, as shown in FIG. 2A, an arbitrary point, for example, the outer edge 41a of the lesion 41 is designated (clicked) by the mouse 32. Since the fundus image has a multi-valued luminance value (for example, a value of 0 to 256) by the A / D converter 21, the luminance value of the pixel of the clicked outer edge portion 41a is multi-valued. The luminance value is almost the intermediate value (for example, 120), and the luminance value is set as a threshold value for binarization. Therefore, the region extracting unit 23a scans the fundus image for each pixel, binarizes the luminance value that is higher than the set threshold value as “1”, and the lower value as “0”. As shown in (B), an image region having a luminance value higher than the threshold value is extracted.

  Since there may be a plurality of regions having brightness higher than the threshold value, narrowing is performed so that only the region including the position 41a designated (clicked) with the mouse 32 is selected. For this purpose, for example, the outer periphery obtaining unit 23b scans the region 41b with a 3 × 3 pixel region centered on the clicked pixel, and selects only the region 41c by extracting the pixel region “1” (see FIG. 2 (C)), the filtering process is performed on the region to obtain the outer periphery 41d of the region 41c as shown in FIG.

  Subsequently, the minimum circle acquisition means 23c acquires the minimum circle 42 including the entire outer periphery 41d according to a known algorithm.

  This method is a method of specifying a lesion when the button 50c of “Method (3)” in FIG. 4 is operated. However, other known “Method (1): the user can select two points that are considered to be the maximum diameter of the affected area”. It is also possible to specify a lesion by selecting “Specify” and “Method (2): Specifying an area by tracing the outer periphery of the affected area with a user's mouse operation”.

  In this way, since the minimum circle including the lesion is obtained, the area / diameter calculation means 23d is activated by operating the “Calculate” button 50d shown in FIG. 4, and the GLD (maximum diameter) corresponding to the diameter of the minimum circle is activated. ), A value obtained by adding the area of the minimum circle and the equivalent of 1 mm to the diameter as a margin is calculated as the irradiation diameter of the laser beam. When calculating the area of the minimum circle and / or its diameter (corresponding to GLD), the calculated values are used for the imaging magnification of the imaging optical system, the dimensions of the imaging mask, the position of the focus lens in the optical axis direction, etc. The correction is performed according to the imaging parameter, and the correction is performed according to the eye parameter such as the eye refractive power.

  The calculation result is shown in the lower part 50e of FIG. At that time, as shown in FIG. 3A, the designated region of the lesioned part 41c, the calculated minimum circle 42, and the laser beam irradiation diameter 42a are drawn on the screen. At this time, the irradiation diameter is drawn by converting the image equivalent to 1 mm in advance from the image magnification to the number of pixels, and when the distance of the closest part to the nipple edge previously determined is 200 μm or less, the nipple is accidentally irradiated. As a result, the irradiation diameter is drawn in red and a warning is displayed.

  In the above-described example, the luminance threshold is determined according to the position (predetermined point) where the outer edge portion 41a of the lesion is first clicked. It will be different. Therefore, the user can verify the validity of the acquired image or data by changing the threshold value to change the region of the lesion or the minimum circle on the screen.

  This is performed, for example, by operating the increase / decrease buttons (luminance value increasing / decreasing means) 50a, 50b in the dialog shown in FIG. Each time the button 50b is clicked, the previously acquired luminance threshold value can be decreased by a predetermined value, and as shown in FIG. The minimum circle 43 to be drawn and the irradiation diameter 43a of the laser beam increase.

  On the other hand, when the button 50a is clicked, the previously obtained luminance threshold value can be increased by a predetermined value for each click, thereby binarizing as shown in FIG. The area of the lesioned part 41f is reduced, and the minimum circle 44 to be drawn and the laser beam irradiation diameter 44a are also reduced.

  In this way, by adjusting the luminance threshold value for binarization, the size of the designated lesion area changes, so the user can select the most appropriate area while looking at the screen. It is possible to designate and select as a lesion, and it is possible to easily identify a lesion to be treated and measure the actual distance on the retina.

It is a block diagram which shows the structure of the ophthalmic measurement apparatus of this invention. It is explanatory drawing which shows the flow which specifies the lesioned part on a retina. It is explanatory drawing explaining the process of calculating | requiring the laser irradiation area | region irradiated to a lesioned part. It is a screen figure of the dialog box displayed on a monitor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fundus camera 11 Image sensor 20 Image processing device 22 Image memory 23a Area extraction means 23b Perimeter acquisition means 23c Minimum circle acquisition means 23d Area and diameter calculation means 30 Recording device 31 Display means 32 Specification means 33 Luminance value increase / decrease means 34 Input means

Claims (6)

Display means for displaying an electronic image of the fundus photographed with fluorescence;
Designation means for designating the outer edge of the lesion on the image displayed on the display means;
Wherein the luminance value of the outer edge portion of the lesion that is specified by means a threshold, it possesses a region extracting means for extracting a region of high brightness values than the threshold value, and
Further, when a plurality of regions having a luminance value higher than the threshold value are extracted, only the region including the outer edge of the designated lesion is selected, and the outer periphery of the region including the outer edge of the selected lesion is selected. An ophthalmologic measuring apparatus comprising an outer periphery obtaining means for obtaining . The ophthalmologic measurement apparatus according to claim 1 , further comprising a luminance value increasing / decreasing unit that increases / decreases a luminance value of an outer edge portion of the designated lesion portion. Ophthalmic measuring apparatus according to claim 1 or 2, characterized in that it has a minimum circle obtaining means for obtaining the smallest circle containing the determined perimeter. The ophthalmic measurement apparatus according to claim 3 , wherein an area and / or diameter of the obtained circle is calculated, and the calculated area and / or diameter is corrected according to an imaging parameter. The ophthalmic measurement apparatus according to claim 4 , wherein the imaging parameter includes at least one of an imaging magnification of an imaging optical system, a dimension of an imaging mask, and a position of a focus lens in an optical axis direction. The ophthalmic measurement apparatus according to claim 3 , wherein the calculated area and / or diameter of the circle is calculated, and the calculated area and / or diameter is corrected according to an eye parameter to be examined.

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