JP2007319416A - Retinal function measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow an examiner to easily recognize a saturated state of a displayed measurement image, to recognize the reliability of data and to control the excessive rate of amplification. <P>SOLUTION: The retinal function measurement apparatus comprises: an observation/illumination optical system for illuminating the retina region of an eye of a subject; a light receiving optical system for obtaining the fundus image by receiving the reflection light from the retina region; a stimulation light irradiating optical system for stimulating the retina by irradiating the retina region of the eye of the subject with the visible stimulation light; an obtaining means for obtaining the information on the variation of the fundus image by comparing the fundus images obtained by the light receiving optical system before and after the irradiation of the stimulation light; and a display control means for setting a prescribed threshold for the information on the variation obtained by the obtaining means and mapping/displaying the information on the variation with color gradation in a display means based on the set threshold. The display control means displays the information on the variation saturated over the threshold among the mapped/displayed information on the variation in a different color from the color used in the color gradation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retinal function measuring device that optically measures a retinal function of a subject's eye.

As a device for optically measuring the retinal function of a subject's eye, means for illuminating the retina of the subject's eye, receiving light from the illuminated retinal region and obtaining a fundus image, Means for irradiating the retina with stimulation light, and determining a minute change in brightness of the retinal region before and after irradiation of the stimulation light on the fundus (retinal) of the subject's eye, A technique for imaging changes in retinal function and evaluating retinal function is disclosed (see Patent Document 1).
Special Table 2002-521115

  When the retinal function is to be measured using such an apparatus, the amount of change before and after stimulation is very small, and thus the amount of change is calculated with a high gain. Therefore, in order to capture a minute amount of change, it is only necessary to increase the amplification factor, but on the other hand, information that becomes saturated increases. For example, when the brightness change information of the retinal area is simply mapped and displayed as a measurement image in grayscale etc., it is not possible to determine how much of the saturated portion caused by the set amplification factor is appropriate and appropriate It is difficult to determine whether the gain is high. As a result, it is difficult to accurately grasp the retinal function.

  In view of the above problems, the present invention provides a retinal function measuring device that allows an examiner to easily check the saturation state of a displayed measurement image and grasp the reliability of data. An object of the present invention is to provide a retinal function measuring device capable of suppressing an excessive amplification factor.

  In order to solve the above problems, the present invention is characterized by having the following configuration.

(1) an observation illumination optical system that illuminates the retina region of the subject's eye;
A light receiving optical system for obtaining a fundus image by receiving reflected light from the retinal region illuminated by the observation illumination optical system;
A stimulation light irradiation optical system for stimulating the retina by irradiating the retina region of the subject's eye with visible stimulation light;
Obtaining means for comparing fundus images before and after the stimulation light irradiation obtained by the light receiving optical system to obtain change information of the fundus image;
A display control unit configured to set a predetermined threshold value for the change information acquired by the acquisition unit, and to display the change information on a display unit using color shading based on the threshold value; Display control means for displaying change information that saturates beyond the threshold among the displayed change information, a color that is different from the color used for the color shading, or a numerical value of the ratio separately from the mapping display When,
It is characterized by providing.
(2) In the retinal function measuring device according to (1), the display control means displays the change information that is saturated on the plus side and the change information that is saturated on the minus side in different colors. And
(3) In the retinal function measuring device according to (1), the color shading is a gray scale, and change information that saturates beyond the threshold is displayed in color.
(4) The retinal function measuring device according to (1) to (3) further includes a threshold value changing unit for changing the threshold value, and the display control unit uses the threshold value changed by the threshold value changing unit. The change information is displayed by mapping.

  According to the present invention, the examiner can easily confirm the saturation state of the displayed measurement image, and the data reliability can be grasped. Moreover, an excessive gain can be suppressed.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an optical system of a retinal function measuring apparatus according to this embodiment.

  In FIG. 1, the optical system of the present apparatus receives an observation illumination optical system 10 that illuminates a retinal region of a subject's eye E, and reflected light from the retinal region illuminated by the observation illumination optical system 10 to receive a fundus image. A light receiving optical system 20 for obtaining the eye, a stimulating light irradiation optical system 30 for stimulating the retina by irradiating the retina region of the eye of the subject, and a fixation for fixing the eye of the subject. It is roughly divided into a visual optical system 40.

  The observation illumination optical system 10 is an observation light source 11 such as a halogen lamp that emits infrared light, for example, an infrared filter 12 that transmits infrared light having a wavelength of 800 nm to 1000 nm, a condenser lens 13, and reflects infrared light to visible light. A dichroic mirror 14 having a characteristic of transmitting light, a ring slit 15 having a ring-shaped opening, a light projecting lens 16, a perforated mirror 17, a beam splitter 100, and an objective lens 18. The ring slit 15 and the perforated mirror 17 are disposed at a position substantially conjugate with the pupil of the subject's eye E. The observation illumination light emitted from the observation light source 11 is converted into an infrared beam by the infrared filter 12, collected by the condenser lens 13, and then reflected by the dichroic mirror 14 to illuminate the ring slit 15. The light transmitted through the ring slit 15 reaches the perforated mirror 17 through the light projecting lens 16. Most of the light reflected by the mirror portion of the perforated mirror 17 is transmitted through the beam splitter 100 and once converged in the vicinity of the pupil of the eye E through the objective lens 18, and then diffused and examined. A predetermined region of the retina of the human eye E is continuously illuminated. A part of the light reflected by the perforated mirror 17 is reflected by the beam splitter 100 and received by the light receiving element 101. The light receiving element 101 detects the output of observation light output from the observation light source 11. As the light receiving element 101, a photodiode or the like can be considered. The beam splitter 100 disposed in the optical path of the observation illumination optical system 10 transmits visible stimulus light from a stimulus light source, which will be described later, and transmits most of the observation light from the observation light source 11. It has a characteristic to reflect.

  The stimulation light irradiation optical system 30 includes a stimulation light source that emits visible flash light for stimulating the retinal region, a condensing lens 33, and a ring slit 15 to an objective lens 18 that share an optical path with the observation illumination optical system 10. Includes optics. The light source for stimulation can irradiate visible flash light in a single shot or in a flicker form. Here, the visible flash light emitted from the stimulation light source is irradiated to the retinal region of the eye E through the condenser lens 33 and the dichroic mirror 14 through the same optical path as the observation illumination light.

  The light receiving optical system 20 includes an objective lens 18, a focusing lens 21 movable in the optical axis direction, an imaging lens 22, and a two-dimensional light receiving element 23 (for example, a two-dimensional CCD sensor). The focusing lens 21 moves in the optical axis direction by driving the drive mechanism 50. The reflected light from the retinal region illuminated by the observation light source 11 is once condensed in front of the perforated mirror 17 via the objective lens 18 and then passes through the opening of the perforated mirror 17. Then, the reflected light that has passed through the aperture (hole portion) of the perforated mirror 17 is condensed by the imaging lens 22 via the focusing lens 21 and then imaged on the two-dimensional light receiving element 23.

  Returning to FIG. 1, the fixation optical system 40 includes a fixation light source 41 that emits visible light, a pinhole (or a fixation chart) 42, and a dichroic mirror that has a characteristic of reflecting visible light and transmitting infrared light. The optical path from the dichroic mirror 29 to the objective lens 18 is shared with the light receiving optical system 20. The pinhole 42 is arranged at a position substantially conjugate with the observation point (imaging point) of the retina of the subject's eye E. The light emitted from the fixation light source 41 passes through the pinhole 42, is reflected by the dichroic mirror 29, and then passes through the optical path in the direction opposite to the reflected light from the retina (imaging lens 22 to objective lens 18). An image is formed on the retina of the examiner's eye.

  FIG. 2 is a block diagram showing a control system of the retinal function measuring apparatus in the present embodiment. A control unit 70 controls the entire apparatus. The control unit 70 includes an observation light source 11, an offset / gain adjustment unit 24, an A / D converter 25, a stimulus light source, a fixation light source 41, a focus drive mechanism 50, a storage unit 72, a control unit 74, and a fundus of the subject. The image processing unit 71 and the like for imaging the image formation and the retinal function are connected. Reference numeral 75 denotes a monitor on which the fundus image formed by the image processing unit 71 is displayed. The storage unit 72 is for storing various information. The control unit 74 is for performing various input operations.

  The light receiving signal detected by the two-dimensional light receiving element 23 is adjusted in offset value and gain by the offset / gain adjusting unit 24, converted from an analog signal to a digital signal by the A / D converter 25, and then the control unit 70. To be stored in the storage unit 72. Here, the control unit 70 can adjust the offset value and gain of the received light signal input to the A / D converter 25 by sending a command signal to the offset / gain adjustment unit 24. Thereby, the offset value and gain of the light receiving element 23 can be adjusted.

  The operation of the retinal function measuring apparatus having the above configuration will be described. The examiner moves the apparatus with respect to the eye to be examined using a joystick (not shown), and the alignment is performed so that the fundus of the eye E is irradiated with illumination light and a desired fundus image is displayed on the monitor 75. I do. Then, the focus adjustment of the image is performed by driving the drive mechanism 50 using a focus adjustment switch provided in the control unit 74.

  When measuring the retinal function, a photographing button (not shown) of the control unit 74 is pressed in a state where a fundus image at a desired position is displayed on the monitor 75. When the photographing button is pressed, the control unit 70 stores the fundus image before the stimulation light emission in the storage unit 72 as a reference retinal image, and emits visible flash light toward the fundus of the eye E using the stimulation light source. Irradiate. The infrared illumination light continuously illuminates a predetermined region of the fundus of the eye E regardless of before and after the flash light irradiation.

  In the case of flickering the visible flash light, the control unit 70 performs the stimulation light irradiation repeatedly performed by the stimulation light irradiation optical system 30 by synchronizing the exposure operation of the light receiving element 23 and the blinking operation of the stimulation light source. Image acquisition control for acquiring a fundus image is performed in between. That is, the control unit 70 performs control for acquiring a fundus image between repeated stimulation light irradiations in flicker stimulation in which stimulation light irradiation is repeatedly performed by repeatedly turning on and off the light source for stimulation. Note that retinal images acquired over time are stored in the storage unit 72 as needed. In the present embodiment, the time during which the stimulus light source is continuously blinked can be arbitrarily set.

  More specifically, the controller 70 stimulates the light receiving element 23 during the exposure operation in accordance with the timing at which the exposure / transfer operation of the light receiving element 23 is repeated at a predetermined frequency (for example, 30 Hz). The blinking operation of the stimulus light source 31 is controlled so that the stimulus light source 31 is turned off and the stimulus light source 31 is turned on while the light receiving element 23 is performing the transfer operation.

  At this time, the control unit 70 can acquire a retinal image for one frame by one exposure / transfer operation by the light receiving element 23. That is, the light receiving element 23 exposes (accumulates) the fundus reflection light received on the light receiving surface, and transfers the electric charge accumulated by the photoelectric effect during the exposure to the outside (storage unit 72) as an electric signal, thereby retina. One frame of image is acquired. In the present embodiment, the control unit 70 is input to the control unit 70 together with the electrical signal from the light receiving element 23 in order to obtain the timing of the exposure / transfer operation of the light receiving element 23 based on the synchronization signal of the light receiving element 23. A function of acquiring a synchronization signal of the light receiving element 23.

  FIG. 3 shows an example of the blinking operation of the stimulus light source according to the present embodiment. In the case of FIG. 3 (a), it is always blinking in synchronization with the frame rate of the light receiving element 23 (when the frame rate of the light receiving element 23 is 30 Hz, the lighting operation of the light source 31 is set to 30 Hz). FIG. 3B shows the light source 31 turned on at 15 Hz. That is, it is sufficient if the stimulation light source blinks at a frequency (the number of times the light is turned on per second) at which the frame rate of the light receiving element 23 is divisible by an integer (for example, when the frame rate is 30 Hz per second, The lighting of the light source 31 is set to 10 Hz or 15 Hz). Note that it is not always necessary for the lighting time of the light source 31 to coincide with the time required for the transfer operation of the light receiving element 23, and it is sufficient that the light source 31 is turned on at a timing when the exposure operation by the light receiving element 23 is not performed. .

  By irradiating the visible stimulus light in a flicker manner by the method as described above, the stimulus light is not mixed in any frame in the retinal image acquired by the light receiving element 23. Therefore, the intrinsic signal of the retina acquired during flicker stimulation can be accurately acquired at any timing. Therefore, it is possible to accurately determine the change in the brightness of the retinal image during flicker stimulation, and to measure the retinal function of the eye to be examined in more detail.

  In the above description, the light source 31 is controlled to blink in accordance with the timing at which the exposure / transfer operation of the light receiving element 23 is repeatedly performed at a predetermined frequency. In accordance with the timing at which the extinguishing operation is repeatedly performed at a predetermined frequency, the light receiving element 23 performs a transfer operation while the stimulation light source 31 is lit, and the light receiving element 23 while the stimulation light source 31 is extinguished. The exposure / transfer operation of the light receiving element 23 may be controlled so that the exposure operation is performed. In this case, it is conceivable to use the light receiving element 23 capable of changing the frame rate as the light receiving element 23. For example, when the blinking operation of the light source 31 is set to 20 Hz for 1 second, the control unit 70 adjusts the frame rate of the light receiving element 23 to 20 Hz, while the light source 31 for stimulation is on. The transfer operation is performed so that the light receiving element 23 performs the exposure operation while the stimulus light source 31 is turned off. In this way, even when the repetition frequency of turning on and off the light source 31 for stimulation can be arbitrarily adjusted, the intrinsic signal of the retina acquired during flicker stimulation can be accurately acquired at any timing. it can.

  When the irradiation of the stimulation light to the retinal region is completed, the control unit 70 further stores the fundus image after the irradiation operation of the flash light (single stimulation light or stimulation light that is turned on in flicker) is completed. Store in the unit 72. Not only one fundus image is taken after the flash light irradiation, but the fundus image may be stored continuously or over time after the flash light irradiation so that a change in the retinal function can be seen. In this case, data used for analysis may be extracted from a plurality of stored images.

  Then, the control unit 70 performs analysis by performing arithmetic processing on a predetermined fundus image stored in the storage unit 72. In this case, the control unit 70 compares the fundus images before and after the flash light irradiation stored in the storage unit 72 to acquire fundus image change information, and displays the result on the monitor 75 via the image processing unit 71. .

  In addition, the control unit 70 performs arithmetic processing on the retinal image before flash light irradiation stored in the storage unit 72 and the retinal image acquired between flicker stimuli to obtain retinal function change information, and the result is obtained. It can be displayed on the monitor 75 via the image processing unit 71. In this case, it is also possible to acquire retinal function change information from the retinal image acquired between flicker stimuli and the retinal image after flicker stimulation is completed.

  Here, the principle for measuring the retinal function will be briefly described. That is, when stimulation light such as flash light is irradiated to the fundus of the subject's eye E and the cells constituting the retina are stimulated, the neuronal activity changes with the stimulation, and this neural activity occurs. The intensity (reflectance) of the reflected light at the part changes. For this reason, by reading the change in the brightness of the fundus image (the reflectance of the retinal area with respect to the observation light) before and after the flash light irradiation, an intrinsic signal change resulting from the change in the activity of the nerve cell can be obtained. . Therefore, the retinal function of the subject's eye can be measured.

  For example, when measuring the retinal function based on the fundus images before and after the flash light irradiation, the control unit 70 first stores the fundus image before the flash light irradiation (reference fundus) stored in the storage unit 72 when measuring the retinal function. Image) and the fundus image after flash light irradiation are aligned. For alignment, feature points (eg, blood vessel shape, nipple, macula, etc.) are extracted by image processing from the fundus image before irradiation (reference fundus image) and the fundus image after irradiation, and both images are moved relatively. The position where the feature points of both images most closely match is obtained by arithmetic processing by performing enlargement, reduction, or the like. Note that the alignment method is not limited to this, and a known image processing technique may be used.

  After the alignment of the fundus image before and after such flash light irradiation, the control unit 70 obtains, for each pixel, a change in the brightness of the fundus image after irradiation with respect to the brightness of the fundus image before irradiation. The change in brightness can be obtained by obtaining a difference, a ratio, or the like. The image processing unit 71 displays the brightness change information obtained by the control unit 70 on the monitor 75 in association with each pixel. As brightness change information, a method of displaying brightness change information as an image according to shading and height, numerical information of differences and ratios, and processing of this numerical information by a predetermined analysis program for evaluating retinal function It can be expressed by the information etc.

  Next, an example will be given in which change information of the brightness of the fundus image before and after stimulation light irradiation is displayed on the monitor 75 as a measurement image (mapping display). First, the control unit 70 obtains brightness change information (difference or ratio) between the fundus image before the flash light irradiation and the fundus image after the flash light irradiation for each pixel of the light receiving element 23 (in the case of the ratio). Before / after irradiation, in case of difference, before irradiation-after irradiation). Then, the image processing unit 71 displays the brightness change information obtained by the control unit 70 on the monitor 75 as a measurement result.

  In this case, the image processing unit 71 sets a predetermined threshold for the change information acquired as described above, and changes the color of the change information based on the set threshold (for example, a gray scale of 255 gradations). Display the mapping using. Here, the setting of the predetermined threshold by the image processing unit 71 is for setting the width of the change information expressed by color shading, and when the upper and lower thresholds are set, the set threshold is set. The change information within the range is expressed by the color shading.

  Further, the image processing unit 71 displays change information that is saturated and exceeds the threshold among the change information that is displayed by mapping in a color that is different from the color that is used for color shading. For example, when the change information is displayed by mapping using grayscale, the image processing unit 71 exceeds the threshold value among the mapping images displayed on the monitor 75 and is in a saturated state (plus peak and minus peak). And the pixel position of the display monitor 75 corresponding to the image signal detected as being saturated is colored and displayed. In this case, the change information that is saturated on the plus side and the change information that is saturated on the minus side may be displayed in different colors. For example, for change information that is saturated on the plus side, The change information that is displayed in yellow and is saturated on the minus side may be displayed in blue.

  FIG. 4 is a plot of data for one horizontal line of a measurement image displayed on the monitor 75. In this case, the change rate of brightness is expressed in white as the change rate increases in the positive direction, and is expressed in black as the change rate increases in the negative direction. Here, the width of the change rate expressed in gray scale is set to the lower limit threshold value −0.5% and the upper limit threshold value + 0.5%, and information on the change rate within this range is gray scale (256 gradations). When the image is to be expressed by the mapping image (measurement image) displayed on the monitor 75, the brightness change part (near the center in the figure) and the part (near part in the figure) where there is almost no change. The contrast will be relatively reduced, and it will be difficult to see the change in brightness in grayscale.

  On the other hand, when the change rate range expressed in grayscale is expressed as the lower limit threshold (minimum value) -0.1% and the upper limit threshold (maximum value) + 0.1% (when the amplification factor is increased) The measurement image displayed on the monitor 75 has a clear contrast between the part where the brightness has changed (near the center in the figure) and the part where the brightness has hardly changed (the peripheral part in the figure), and the change in brightness. Becomes easier to understand. However, many image signals in a saturated state exceeding the range of the brightness change rate expressed in gray scale (within the set upper and lower thresholds) are generated.

  Therefore, as in this embodiment, by displaying the display position corresponding to the image signal that is saturated in the measurement image in a color different from the shade of the color indicating change information such as color display, the examiner can The saturated portion in the measurement image displayed on the monitor 75 can be easily grasped.

  Here, the examiner uses the adjustment switch for changing the range of the upper and lower thresholds of the brightness change rate width expressed in grayscale as the mapping image, and displays the change information to be expressed as the mapping image. Adjust the width (range). This makes it possible to confirm the display of a saturated signal while looking at the display screen while reducing the influence of the noise signal, and adjusting the retinal function so that an appropriate mapping display can be performed. Can do. Specifically, the range of change rate expressed in gray scale is changed from the lower threshold −0.1% and the upper threshold + 0.1% to, for example, the lower threshold −0.3% and the upper threshold + 0.3%. Then, the measurement image may be displayed based on the upper and lower thresholds. In this case, both the upper limit side (maximum value) and the lower limit side (minimum value) may be adjusted within the same range, or the upper and lower thresholds may be adjusted independently.

  In this way, it is possible to adjust the image of the measurement image displayed on the monitor 75 so that the mapping image is less affected by the noise signal and the contrast of the brightness change is clear. In this embodiment, the mapping is displayed in gray scale. However, the present invention is not limited to this, and it is naturally possible to display using other shades of color. Even in this case, the saturated portion may be displayed in a color different from the color representing the change rate.

  In addition to the mapping display described above, the ratio of change information that saturates beyond a threshold value may be expressed as a numerical value. For example, the image processing unit 71 detects image signals that are in a saturated state exceeding the set threshold from the change information, and measures the number thereof. Then, the ratio of the number of image signals in a saturated state to the number of image signals of the entire change information (the number of pixels of the light receiving element 23) is obtained, and the ratio is expressed in stages (for example, 1, 2, 3, 4). 5).

  The display as described above is a stage before irradiation of the stimulation light, and can be used as a confirmation image for the examiner to confirm that the fixation eye movement of the subject's eyes is stabilized. In this case, the control unit 70 detects the fundus image of the subject's eye based on the output signal from the light receiving element 23. At this time, the control unit 70 acquires the reference fundus image for detecting the change information of the brightness of the fundus image by the light receiving element 23 and stores it in the storage unit 72. The reference fundus image may be acquired at a predetermined time interval (for example, every 3 seconds). Also, the fundus image acquired one frame before the fundus image detected in real time may be used as the reference fundus image.

  After the reference fundus image is acquired, the control unit 70 monitors the fundus image detected by the light receiving element 23 in real time, and receives brightness change information between the fundus image and the reference fundus image acquired in real time. It calculates | requires for every pixel position of the element 23 at any time. That is, the control unit 70 acquires brightness change information (for example, change rate or difference) with respect to the reference fundus image over time. Then, the image processing unit 71 performs mapping display of the brightness change information obtained by the control unit 70 using the shades of color. In this case, the image processing unit 71 may display the change information that saturates beyond a predetermined threshold value in a color different from the color used for color shading. Note that the change information mapped and displayed by the image processing unit 71 is updated at any time or at a predetermined timing based on the brightness change information with respect to the reference fundus image acquired over time. In addition, when calculating | requiring the brightness change information using a change rate, in order to catch the fixation eye movement of a test subject's eye, it is possible to set a detection range to the range of +/- 0.5%, for example.

  Note that the above image display control is not limited to application to the retinal function measuring device, and when anesthesia is applied to the subject's eye, it is confirmed whether the anesthesia is effective and whether fixation fixation has stopped. It is also possible to use it. Moreover, it is not restricted to the change information of the brightness of the fundus image, and any subject eye image may be used. For example, change information on the brightness of the subject's anterior ocular segment image may be acquired by a light receiving element.

  In the above description, the control unit 70 determines whether or not the fixation eye movement of the subject's eye is stable based on the brightness change information of the retinal image acquired over time as described above. Then, the determination result may be notified. For example, the control unit 70 obtains brightness change information between the fundus image acquired in real time and the reference fundus image for each pixel position of the light receiving element 23 as needed. The control unit 70 determines that the fixation eye movement of the subject's eye is stable when the brightness change information of the retinal image acquired over time does not change significantly over a predetermined time. , To that effect is displayed on the monitor 75. On the other hand, if the brightness change information of the retinal image acquired over time has changed significantly within a predetermined time, it is determined that the fixation eye movement of the subject's eye is not stable, A message to that effect is displayed on the monitor 75.

  In the case of measuring the retinal function, the temporal fluctuation of the observation light may greatly affect the measurement data. For this reason, it is preferable to acquire a fundus image in a state where there is no fluctuation of observation light. Hereinafter, a method for acquiring a fundus image in a state where there is no fluctuation of observation light will be described.

  When the observation light is emitted from the observation light source 11, the control unit 70 displays time-dependent change information of the output of the observation light emitted from the observation light source 11 based on the detection result detected by the light receiving element 101 illustrated in FIG. 1. get. In this case, the control unit 70 stores the observation light output detected at a predetermined timing in the storage unit 72 as a reference output in order to set one of the detection results detected over time as the reference output. Keep it. The reference output may be set once after a lapse of a predetermined time after the light source 11 is turned on, or may be set as needed at predetermined time intervals (for example, every 10 seconds).

  After the reference output is set, the control unit 70 monitors the output signal from the light receiving element 101 in real time, and acquires change information (for example, change rate or difference) of the observation light output with respect to the reference output over time. . When obtaining change information of the observation light output using the change rate, in order to capture a minute change in the output of the observation light emitted from the light source 11, for example, the detection range is ± 0.05% of the reference output. It is conceivable to set the range.

  The temporal change information of the observation light output acquired as described above is displayed on the display screen of the monitor 75 by the image processing unit 71 (see FIG. 5). FIG. 5 is a diagram showing a change with time of the change rate of the output of the observation light. At this time, the change information of the observation light output is obtained in real time by the arithmetic processing of the control unit 70, and therefore the image processing unit 71 updates the change information displayed on the monitor 75 as needed.

  With the configuration as described above, the observation light source 11 is used in an apparatus such as this embodiment that needs to capture minute changes in the brightness of the fundus image (for example, a range within 0.5%) due to stimulation light irradiation. Since it is possible to confirm a minute change in the output of the observation light emitted from the retinal, it is possible to check the temporal stability of the retinal observation light that affects the measurement result.

  In the above description, the temporal change information of the output of the observation light emitted from the observation light source 11 is displayed on the monitor 75 in real time. However, the present invention is not limited to this. Anything that can check stability can be used. For example, the control unit 70 determines whether or not the change rate of the observation light output obtained in real time exceeds a preset allowable range (for example, the change rate is within ± 0.5%). The result may be displayed on the monitor 75. In addition, when the change rate of the output of the observation light acquired over time does not change significantly over a predetermined time, the control unit 70 determines that the retinal observation light is stable over time, and accordingly Is displayed on the monitor 75. On the other hand, if the rate of change in the output of the observation light acquired over time changes significantly within a predetermined time, it is determined that the retinal observation light is not stable in time, and this is monitored. 75 may be displayed.

  Further, in the above description, the temporal change information of the output of the observation light is displayed on the monitor 75. However, the information is obtained as described above based on the detection result detected by the light receiving element 101. The change information of the fundus image may be corrected. In this case, when the fundus image is acquired by the light receiving element 23, the control unit 70 stores the output of the observation light detected by the light receiving element 101 in the storage unit 72. Thereby, the storage unit 72 stores the output of observation light at the time of image acquisition corresponding to each fundus image acquired over time.

  Hereinafter, a specific method of the correction process will be described. For example, the control unit 70 performs correction processing when obtaining, for each pixel, change information of the brightness of the fundus image after irradiation with respect to the brightness of the fundus image before irradiation. For example, when calculating the change rate of the brightness of the fundus image before and after the stimulation light irradiation, a correction equation such as (Equation 1) is used.

Iｂは刺激前の眼底画像の輝度であり、Ｒｂは刺激前の眼底画像取得の際に受光素子１０１によって検出された観察光の出力である。また、Iｓ（ｔ）は刺激後の眼底画像における輝度であり、Ｒｓ（ｔ）は刺激後の眼底画像取得の際に受光素子１０１によって検出された観察光の出力である。

Ib is the luminance of the fundus image before stimulation, and Rb is the output of the observation light detected by the light receiving element 101 when acquiring the fundus image before stimulation. Further, Is (t) is the luminance in the fundus image after stimulation, and Rs (t) is the output of the observation light detected by the light receiving element 101 when acquiring the fundus image after stimulation.

  By performing the correction processing as described above, the temporal fluctuation of the observation light is canceled out, so that the retinal function can be accurately measured.

  When measuring the retinal function as described above, the offset value and imaging gain of the light receiving element 23 may be adjusted in order to perform measurement with higher accuracy. FIG. 6 is a view when the fundus image of the eye to be examined acquired by the light receiving element 23 is displayed on the monitor 75, and is when the alignment with respect to the eye to be examined before the stimulation light emission is completed. First, the examiner sets a region that the examiner wants to measure from the fundus image on the display monitor 75 observed in real time (for example, the vicinity of the macula is designated from the entire retina image). At this time, the examiner operates a measurement part setting switch (for example, a mouse) provided in the control unit 74 to display a rectangular mark M electrically displayed on the retina image on the screen. The measurement part is set. Note that the size of the mark M can be arbitrarily changed, and the range of the measurement site can be changed. The mark M can be set to an arbitrary shape (round shape or cylindrical shape).

  When the measurement part is set, the control unit 70 performs offset / gain so that the retinal image received at the light receiving position of the light receiving element 23 corresponding to the measurement part set as described above can be detected in a wide range. The adjustment unit 24 is used to adjust the offset value and gain (gain) of the light receiving element 23. FIG. 7 is a reference diagram for explaining the adjustment of the offset value and gain of the light receiving element 23. FIG. 7 is a diagram showing a change in the received light signal in the scanning line S on the image of FIG.

  The control unit 70 detects the minimum value Kmin and the maximum value Kmax of the light reception signal in the light receiving region of the light receiving element 23 corresponding to the preset measurement site based on the image signal based on the retinal image output from the light receiving element 23 ( FIG. 7 (a)). Then, the offset value of the light receiving element 23 is adjusted so that the minimum value Kmin of the detected light receiving signal is close to the output signal lower limit value of the light receiving element 23 (see FIG. 7B). More specifically, in the output signal of the light receiving element 23 output from the light receiving element 23 to the A / D converter 25 via the offset / gain adjusting unit 24, the minimum value Kmin of the received light signal detected as described above is obtained. The offset value is adjusted using the offset / gain adjustment unit 24 so that the corresponding output signal is near the lower limit value of the output signal that can be detected by the A / D converter 25 (near the lower limit value of the detection region). Then, after the offset value is adjusted, the gain of the light receiving element 23 is adjusted (set) in the plus direction so that the maximum value Kmax of the light receiving signal is near the output signal upper limit value or near the predetermined value (see FIG. 7). c)). More specifically, in the output signal of the light receiving element 23 output from the light receiving element 23 to the A / D converter 25 via the offset / gain adjusting unit 24, the maximum value Kmax of the received light signal detected as described above is obtained. The gain of the light receiving element 23 is adjusted using the offset / gain adjustment unit 24 so that the corresponding output signal is near the upper limit value of the output signal that can be detected by the A / D converter 25 (near the upper limit value of the detection region). To do. In the above description, the light reception signal on the scanning line S has been described. However, actually, the offset and gain are adjusted based on the light reception signal corresponding to the area surrounded by the mark M.

  Thereafter, when the photographing button is pressed by the examiner, the control unit 70 acquires the fundus image before the stimulation light emission using the light receiving element 23 after the offset value and gain adjustment, and stores them in the storage unit 72 as a reference retinal image. Let And the control part 70 irradiates visible flash light toward the fundus of the eye E to be examined using the light source for stimulation. Then, the retinal images during and after the flash light irradiation are acquired and stored in the storage unit 72 using the light receiving element 23 after the offset value and gain adjustment. Thereafter, the control unit 70 obtains, for example, a change in brightness of the retinal image after irradiation with respect to the brightness of the retinal image before irradiation, and displays brightness change information on the monitor 75.

  In this way, since the intrinsic signal at the measurement site on the retina can be detected in a wide range, the retinal function of the eye to be examined can be accurately measured.

  When brightness change information is displayed on the monitor 75, the control unit 70 may perform an initialization process to return the offset value and gain changed as described above to predetermined values. For example, in preparation for the next measurement, it may be possible to return to an offset value and gain suitable for alignment observation.

  In the above description, one measurement part is set. However, the present invention is not limited to this, and a plurality of measurement parts may be set. In this case, a plurality of measurement parts can be set (designated) on the screen of the monitor 75. When a plurality of measurement part setting signals are input by measurement part setting, the control unit 70 has a wide range of retinal images received in the light receiving region of the light receiving element 23 corresponding to each of the plurality of set measurement parts. The offset value and gain (gain) of the light receiving element 23 are adjusted in each light receiving region so that they can be detected. As described above, as the light receiving element 23 used for adjusting different offset values and gains in the plurality of light receiving regions of the light receiving element 23, for example, adjustment of the offset value and gain is performed for each pixel position of the light receiving element 23. Possible CMOS sensors are listed.

  In the above description, an arbitrary measurement site is set before adjusting the offset value and gain of the light receiving element 23. However, the present invention is not limited to this, and the retina received by the light receiving element 23 is not limited thereto. You may make it adjust the offset value and gain (gain) of the light receiving element 23 so that the whole image can be detected in a wide range. In this case, the minimum value Kmin and the maximum value Kmax of the light reception signal of the light receiving element 23 corresponding to the entire retinal image are detected based on the image signal based on the retinal image output from the light receiving element 23. When the entire retinal image is used as the measurement site, the minimum value Kmin and the maximum value Kmax of the light reception signal are removed as described above after removing the image signal corresponding to the mask portion (not shown) arranged in the optical system of the light reception optical system. Is detected. The following control is the same as that when the measurement site is set, and the description thereof is omitted.

  In the above description, after the offset value is adjusted, the gain of the light receiving element 23 is set so that the maximum value Kmax of the light receiving signal is close to the output signal upper limit value of the light receiving element 23 or near a predetermined value. However, the present invention is not limited to this. That is, after the offset value is adjusted, the light receiving condition of the light receiving element 23 is set so that the maximum value Kmax of the light receiving signal is near the upper limit value of the light receiving signal of the light receiving element 23 or near the predetermined value. As long as is set. Note that the light receiving conditions of the light receiving element 23 to be set include the exposure time of the light receiving element 23 and the output of observation light emitted from the observation light source 11.

It is a schematic block diagram which shows the optical system of the retinal function measuring apparatus which concerns on this embodiment. It is the block diagram which showed the control system of the retinal function measuring device in this embodiment. The example of the blinking operation | movement of the stimulus light source which concerns on this embodiment is shown. This is a plot of data for one horizontal line of a measurement image displayed on a monitor. It is a figure which shows the time-dependent change of the change rate of the output of observation light. It is a figure when the fundus image of the eye to be examined acquired by the light receiving element is displayed on the monitor. It is a reference diagram for explaining adjustment of an offset value and a gain of a light receiving element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Observation illumination optical system 11 Observation light source 20 Light reception optical system 23 Light receiving element 24 Offset / gain adjustment part 25 A / D converter 30 Stimulation light irradiation optical system 31 Stimulation light source 70 Control part 71 Image processing part 72 Storage part 74 Control part 75 Display monitor

Claims (4)

An observation illumination optical system for illuminating the retina region of the subject's eye;
A light receiving optical system for obtaining a fundus image by receiving reflected light from the retinal region illuminated by the observation illumination optical system;
A stimulation light irradiation optical system for stimulating the retina by irradiating the retina region of the subject's eye with visible stimulation light;
Obtaining means for comparing fundus images before and after the stimulation light irradiation obtained by the light receiving optical system to obtain change information of the fundus image;
A display control unit configured to set a predetermined threshold value for the change information acquired by the acquisition unit, and to display the change information on a display unit using color shading based on the threshold value; Display control means for displaying change information that saturates beyond the threshold among the displayed change information, a color that is different from the color used for the color shading, or a numerical value of the ratio separately from the mapping display When,
A retinal function measuring device comprising:   2. The retinal function measuring apparatus according to claim 1, wherein the display control means displays the change information that is saturated on the plus side and the change information that is saturated on the minus side in different colors. Functional measuring device.   2. The retinal function measuring device according to claim 1, wherein the color shading is a gray scale, and change information that saturates beyond the threshold is displayed in color. The retinal function measuring device according to claims 1 to 3,
The apparatus further comprises threshold value changing means for changing the threshold value, and the display control means displays the change information by mapping using the threshold value changed by the threshold value changing means.

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