JP2016029968A - Image processing apparatus, image processing method, program, and toric intraocular lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus, an image processing method, and a program capable of highly accurately calculating the three-dimensional position of the equatorial part of the crystalline lens from a three-dimensional image of an anterior ocular segment.SOLUTION: A fundus oculus photographing apparatus comprises: an image generation unit for capturing a plurality of anterior ocular segment tomographic images in which the anterior surface and the posterior surface of the crystalline lens of a subject's eye are photographed; a curve intersection calculation unit for approximating curves to the anterior and posterior surfaces of the crystalline lens with respect to each of the plurality of the anterior ocular segment tomographic images and for calculating the intersections of the anterior surface approximating curves and the posterior surface approximating curves as the crystalline lens equatorial part of the subject's eye; and a three-dimensional map processing unit for creating a three-dimensional map indicating the crystalline lens equatorial part.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image processing device, an image processing method, a program, and a toric intraocular lens. In particular, the present invention relates to an image processing apparatus and an image processing method for measuring the shape of a crystalline lens of an eye to be examined using a tomographic image, a program for executing the image processing method, and a toric intraocular lens that can be inserted into the eye to be examined.

  Cataract treatment is aimed at restoring the patient's visual function, removing the turbid lens, and inserting and fixing an intraocular lens into the lens capsule (the eye tissue corresponding to the bag containing the lens). The method is used. Of the intraocular lenses used in the treatment of cataracts, the toric intraocular lens has the effect of correcting astigmatism. However, since the effect of astigmatism correction is reduced when axial misalignment occurs, it is required to fix the support portion of the toric intraocular lens so as not to misalign with the equator portion of the crystalline lens capsule. In order to fix the support portion of the toric intraocular lens to the lens capsule so as not to be misaligned, it is necessary to use an intraocular lens having a shape suitable for the three-dimensional shape of the lens capsule of the eye to be examined in the preoperative examination of cataract surgery. desirable. For this purpose, it is necessary to be able to calculate the three-dimensional shape of the crystalline lens capsule of the eye to be examined in the preoperative examination of cataract surgery. Here, in order to perform more accurate anterior ocular segment analysis on the captured 3D image of the anterior segment, correcting the 3D image so that the inclination of the anterior segment image in the 3D image is eliminated, It is disclosed in Patent Document 1.

JP 2010-220757 A

  By the way, because the measurement light is blocked by the iris of the anterior eye due to the structure of the eye, the end of the crystalline lens located deeper than the iris along the visual axis of the eye to be examined is not shown in the three-dimensional image. For this reason, since the equator part of the crystalline lens cannot be specified from the three-dimensional image of the anterior eye part, the three-dimensional position of the equator part cannot be calculated with high accuracy. Accordingly, one of the objects of the present invention is to enable accurate calculation of the three-dimensional position of the equator of the crystalline lens from the three-dimensional image of the anterior segment.

  The image processing apparatus according to the present invention includes an image generation unit that acquires a plurality of anterior ocular segment tomographic images in which the front lens surface and the posterior lens surface of the eye to be inspected, and the front lens surface and the crystalline lens for each of the plurality of anterior ocular segment tomographic images. Approximation processing means for approximating the back surface with a curve, equatorial part determining means for determining an intersection of a curve approximating the front surface of the lens and a curve approximating the rear surface of the lens as the lens equator part of the eye to be examined, and the lens equator part And a three-dimensional map creating means for creating the three-dimensional map shown.

  According to the present invention, it is possible to accurately calculate the three-dimensional position of the equator of the crystalline lens from the three-dimensional image of the anterior segment.

FIG. 1 is a schematic diagram of an overall configuration of an ophthalmologic apparatus including an image processing apparatus according to the present embodiment. FIG. 2 is a flowchart showing processing in the present embodiment. FIG. 3 is a diagram illustrating a display example of the display screen of the display unit in the present embodiment. FIG. 4 is a diagram illustrating an example of a scan pattern when an anterior segment tomographic image is captured. FIG. 5 is a diagram illustrating an example of an anterior segment tomographic image. FIG. 6 is a diagram illustrating an example of a state where the approximate curves of the front and rear surfaces of the crystalline lens are overlaid on the anterior segment tomographic image. FIG. 7 is a diagram showing an example of a three-dimensional map of the crystalline lens equator viewed from above. FIG. 8 is a diagram showing a three-dimensional map of the crystalline lens equator. FIG. 9 is a diagram illustrating a second example of a three-dimensional map of the crystalline lens equator. FIG. 10 is a flowchart illustrating an example of a method for customizing an intraocular lens. FIG. 11 is a front view showing an example of a customized intraocular lens. FIG. 12 is a side view showing an example of a customized intraocular lens. FIG. 13 is a diagram illustrating an example of an anterior ocular segment tomographic image in a state where an intraocular lens is inserted. FIG. 14 is a front view showing an example of the anterior segment with an intraocular lens inserted. FIG. 15 is a front view showing an example of a lens capsule with an intraocular lens inserted therein.

  Hereinafter, an image processing apparatus and an image processing method according to an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, a configuration in which the image processing apparatus is applied to an ophthalmologic apparatus is shown as an example. An ophthalmologic apparatus is an example of an imaging apparatus.

[Overall configuration of the device]
FIG. 1 is a schematic diagram illustrating an example of the overall configuration of an ophthalmologic apparatus 1 that is an example of an imaging apparatus according to the present embodiment. At least a part of an image analysis unit 190 of the ophthalmologic apparatus 1 described later is an example of the image processing apparatus according to the present embodiment. An image analysis unit 190, which is an example of an image processing apparatus, executes an image processing method according to an embodiment of the present invention. The entire ophthalmic apparatus 1 can be regarded as an “ophthalmic system”, and the entire “imaging apparatus” can be regarded as an “imaging system”.

  The ophthalmologic apparatus 1 includes an SS-OCT (Swept source OCT) 100, an internal fixation lamp 170, an anterior ocular segment observation unit 160, and a control unit 200. Then, the control unit 200 of the ophthalmologic apparatus 1 turns on the internal fixation lamp 170 to cause the subject to gaze at the internal fixation lamp 170, and in this state, the anterior ocular segment observed by the anterior ocular segment observation unit 160 The SS-OCT 100 is aligned using the Ea image. After the alignment is completed, the control unit 200 images the anterior segment Ea of the eye E using the SS-OCT 100.

<Configuration of SS-OCT100>
A configuration example of the SS-OCT 100 will be described. The light source 101 is an SS (Swept source) light source that performs light source output by wavelength sweep, and continuously changes its oscillation wavelength while oscillating at a specific wavelength. For example, the light source 101 emits light having a center wavelength of 1310 nm and a wavelength sweep width of 100 nm. The light emitted from the light source 101 is guided to the fiber coupler 104. The fiber coupler 104 divides the light guided from the light source 101 into measurement light (also referred to as “measurement light for tomographic image” or “OCT measurement light”) and reference light corresponding to the measurement light. The branching ratio of the fiber coupler 104 is, for example, 2 (reference light): 98 (measurement light). The branching ratio of the fiber coupler 104 is not limited to the above ratio. The branching ratio of the fiber coupler 104 is preferably larger for the measurement light than for the reference light. This is because the amount of light returned from the measurement light due to absorption and scattering by the eye to be examined is lower than that of the reference light. However, the branching ratio between the reference light and the measurement light may be 50:50.

  The measurement light is guided to the collimator 106 via the optical circulator 133. The collimator 106 emits the light guided from the optical circulator 133 as parallel light. The measurement light emitted from the collimator 106 reaches the dichroic mirrors 161 and 111 via the X scanner 107 as an example of scanning means, the lenses 108 and 109, and the Y scanner 110 as an example of scanning means. The X scanner 107 is an example of scanning means of the SS-OCT 100. For example, a galvano scanner having a galvanometer mirror that scans the measurement light in the horizontal direction in the anterior eye portion Ea is applied. The Y scanner 110 is an example of scanning means of the SS-OCT 100. For example, a galvano scanner having a galvanometer mirror that scans measurement light in the vertical direction at the anterior eye portion Ea is applied. The X scanner 107 and the Y scanner 110 are controlled by the drive control unit 180 of the control unit 200. Each of the X scanner 107 and the Y scanner 110 can scan the measurement light with a desired scan pattern on the anterior segment Ea of the eye E. The range in which the measurement light of the anterior segment Ea is scanned is an example of the tomographic image acquisition range, the tomographic image acquisition position, and the measurement light irradiation position. A common XY scanner may be applied as the X scanner 107 and the Y scanner 110.

  The dichroic mirror 161 has a characteristic of reflecting light having a wavelength of 800 to 1100 nm and transmitting light having other wavelengths. The dichroic mirror 111 has a characteristic of reflecting light having a wavelength of 400 to 900 nm and transmitting light having other wavelengths. The focus lens 114 is provided on the stage 116. When the drive control unit 180 controls the stage 116, the measurement light transmitted through the dichroic mirror 111 is irradiated so that the anterior eye portion Ea of the eye E to be examined is in focus. The measurement light applied to the anterior segment Ea is reflected and scattered at the boundary surface of the cornea 311, the lens 222, the iris 221, and the sclera of the anterior segment Ea (see FIG. 5), and passes through the optical path described above. Return to 133. The measurement light that has returned to the optical circulator 133 is guided to the fiber coupler 135 via the polarization controller 134.

  On the other hand, the reference light branched by the fiber coupler 104 is guided to the collimator 118 via the optical circulator 131. The collimator 118 emits the reference light guided from the optical circulator 131 as parallel light. The reference light emitted from the collimator 118 passes through the dispersion compensation glass 120, is reflected by the mirror 122 on the coherence gate stage 121, and returns to the optical circulator 131. The reference light that has returned to the optical circulator 131 is guided to the fiber coupler 135 via the polarization controller 132. In addition, the mirror 122 is arrange | positioned at a coherence gate. The coherence gate is a position corresponding to the optical path length of the reference light in the optical path of the measurement light (a position where the difference between the optical path length of the constant light and the optical path length of the reference light is zero). The coherence gate stage 121 is controlled by the drive control unit 180 in order to cope with a difference in anterior chamber (anterior chamber) depth for each eye E to be examined. In the present embodiment, the optical path length of the reference light is changed in order to cope with a difference in anterior chamber depth, but the present invention is not limited to this configuration. In short, any configuration that can change the difference between the optical path length of the measurement light and the optical path length of the reference light may be used.

  The fiber coupler 135 synthesizes interference light (hereinafter also referred to as “combined light”) from the measurement light guided from the optical circulators 131 and 133 and the reference light. The combined interference light is guided to the differential amplifier 136. The differential amplifier 136 is used as a photodetector, detects a beat of the guided interference light, and outputs the detected beat as an optical beat signal that is an analog electric signal. An optical beat signal that is an analog electric signal output from the differential amplifier 136 is input to the analog / digital conversion circuit 137.

  The light source 101 outputs k-clock. k-clock is a TTL trigger signal with equal wave number intervals in accordance with the wavelength sweep of the light source 101. The k-clock output from the light source 101 is input to the analog / digital conversion circuit 137 via the k-clock signal line 138. The analog / digital conversion circuit 137 samples the optical beat signal of the interference light in synchronization with the input k-clock. Thereby, the optical beat signal is converted from an analog signal to a digital signal. Then, the analog / digital conversion circuit 137 transmits the optical beat signal converted into the digital signal to the image generation unit 193 of the control unit 200 described later.

By the way, the depth Δz that can be measured by the SS-OCT 100 is expressed as follows when the optical beat signal of the interference light is sampled at a constant frequency interval δν (wavelength interval δk), and c is the velocity of light in the air. It is known to be given in In the following equation, k is a wave number and ν is a frequency. The wave number k is proportional to the frequency ν. That is, that the wave numbers k are equally spaced is equivalent to the frequency ν being equally spaced.

Δz = π / 2δk = c / 4δν

As is clear from this equation, the measurable depth increases as the sampling frequency interval decreases. In this embodiment, k-clock of δν = 6.25 GHz is used as an example of k-clock. In this case, a depth of Δz = 12 mm can be measured.

  The polarization controllers 132 and 134 adjust the polarization so that the intensity of the interference light is maximized. The measurement light and the reference light guided to the fiber coupler 104 are generally in an elliptical polarization state, and components having different polarization do not cause optical interference. Accordingly, the polarization controllers 132 and 134 increase the intensity of the interference light by controlling and aligning the polarizations of the measurement light and the reference light.

<Anterior Eye Observation Unit 160>
Next, the anterior segment observation unit 160 will be described. The anterior segment observation unit 160 generates an image (anterior segment image) of the anterior segment Ea of the eye E to be examined illuminated by the illumination light source 115. The illumination light source 115 includes LEDs 115a and 115b that emit illumination light having a wavelength of 1000 nm. The light reflected by the anterior segment Ea passes through the focus lens 114 and the dichroic mirror 111 and reaches the dichroic mirror 161. The dichroic mirror 161 has a characteristic of reflecting light of 400 to 900 nm and transmitting other light. The light reflected by the dichroic mirror 161 reaches the anterior eye camera 165 via the lenses 162, 163 and 164. The anterior eye camera 165 receives the reached light (that is, an image of the anterior eye part) and converts it to an anterior eye part image. Thereby, an anterior ocular segment image (image data) is generated. The anterior segment image generated by the anterior segment camera 165 is input to the image analysis unit 190.

<Internal fixation lamp 170>
Next, the internal fixation lamp 170 will be described. The internal fixation lamp 170 includes an internal fixation lamp display unit 171 and a lens 172. In the internal fixation lamp display unit 171, a plurality of light emitting diodes (LEDs) are arranged in a matrix. The lighting position of the light emitting diode (which of the LEDs arranged in a matrix is to be lit) is controlled by the drive control unit 180 in accordance with the part to be imaged. The light emitted from the internal fixation lamp display unit 171 is transmitted through the lens 172, reflected by the dichroic mirror 111, transmitted through the focus lens 114, and guided to the eye E to be examined. The display pattern of light emitted from the internal fixation lamp display unit 171 is controlled by the drive control unit 180. Then, a desired pattern is displayed in accordance with the part of the eye E to be imaged. The wavelength of the light emitted from the internal fixation lamp display unit 171 is 520 nm (green) or 630 nm (red), and is controlled by the drive control unit 180 so that the subject can easily see the color.

<Control unit 200>
Next, the control unit 200 will be described. The control unit 200 controls each unit of the ophthalmologic apparatus 1. The control unit 200 includes a drive control unit 180, an image generation unit 193, an image analysis unit 190, a display control unit 191, and a display unit 192. The drive control unit 180 controls the driving of each unit of the ophthalmologic apparatus 1 including the X scanner 107, the Y scanner 110, the coherence gate stage 121, the internal fixation lamp display unit 171 and the stage 116 of the focus lens 114. To do.

  Here, an example of a hardware configuration of the control unit 200 will be described. As the control unit 200, a computer having a CPU, a RAM, a ROM, and a display device is applied. The display device functions as an example of the display unit 192. The ROM stores a computer program for controlling the ophthalmologic apparatus 1 and for executing the image processing method. The CPU reads out a computer program stored in the ROM, expands it in the RAM as appropriate, and executes it. Thereby, the computer functions as the control unit 200 and realizes processing operations described later. As described above, the computer functions as each unit of the control unit 200 (the drive control unit 180, the image analysis unit 190, the image generation unit 193, the display control unit 191, and the display unit 192). Further, the computer also functions as each unit (approximation processing unit 196, curve intersection calculation unit 197, three-dimensional map processing unit 198, alignment processing unit 199) of the image analysis unit 190 which is an example of the image processing apparatus.

  The image generation unit 193 is an example of an image generation unit. The image generation unit 193 performs fast Fourier transform (FFT) that is discrete Fourier transform on the optical beat signal of the interference light output from the analog / digital conversion circuit 137. As described above, the analog / digital conversion circuit 137 discretely samples the optical beat signal input from the differential amplifier 136 at equal wave intervals in synchronization with the k-clock input from the light source 101. Output. Thereby, the image generation unit 193 obtains the intensity of backscattering in one depth direction as a function of the depth distance (depth). One scanning in the depth direction is referred to as an A scan. Then, for each A scan, the X scanner 107 and the Y scanner 110 scan the irradiation light to the eye E with an arbitrary scan pattern, and the image generation unit 193 determines a two-dimensional tomographic image (in the present embodiment, the previous tomographic image). Eye tomographic image). Scanning light in one direction by the X scanner 107 and the Y scanner 110 (galvano scanner) is referred to as a B scan.

  The image analysis unit 190 includes an approximation processing unit 196, a curve intersection calculation unit 197, a three-dimensional map processing unit 198, and an alignment processing unit 199. The approximation processing unit 196 is an example of approximation processing means. The curve intersection calculation unit 197 is an example of an equator determination unit. The three-dimensional map processing unit 198 is an example of a three-dimensional map creation unit and a maximum radial direction calculation unit. The approximation processing unit 196, the curve intersection calculation unit 197, and the three-dimensional map processing unit 198 of the image analysis unit 190 analyze the two-dimensional tomographic image generated by the image generation unit 193, and the equator portion position of the crystalline lens 222 of the eye E to be examined. Is three-dimensionally determined (measured) to create a three-dimensional map indicating the equator position. Then, the result is output to the display control unit 191. Details will be described later.

  The display control unit 191 displays the two-dimensional tomographic image generated by the image generation unit 193, the analysis result by the image analysis unit 190, and the anterior segment image generated by the anterior segment camera 165 on the display screen of the display unit 192. Display. For the display unit 192, for example, various display devices that can display information such as images and characters such as a liquid crystal display are applied. The display unit 192 displays various information in a predetermined display form as will be described later under the control of the display control unit 191. Note that image data may be transmitted from the display control unit 191 to the display unit 192 by wire or wirelessly. In the present embodiment, the display unit 192 is included in the control unit 200, but is not limited to this configuration. The display unit 192 may be provided separately from the control unit 200.

[Processing operation]
Next, the processing operation of the ophthalmologic apparatus 1 will be described. FIG. 2 is a flowchart showing an example of processing operation of the ophthalmologic apparatus 1.

<Adjustment>
In the “adjustment” in step S101, the control unit 200 aligns the SS-OCT 100 and the eye E with the subject in contact with the forehead portion on an unillustrated fixing plate or the like. Here, of the alignment, processing unique to the present embodiment will be described, and processing similar to the conventional processing will be omitted. For example, alignment in the XYZ directions such as working distance, focus, adjustment of the coherence gate, and the like can be applied with the same processing as in the past, and thus description thereof is omitted. In addition, in order to image the lens 222 more widely, a mydriatic may be preliminarily applied to the test eye E before imaging an anterior ocular segment tomographic image, which is an example of a two-dimensional tomographic image.

  First, the angle of the eye E is aligned so that the measurement light is incident so that the measurement light substantially coincides with the eye optical axis of the eye E. Hereinafter, the angle alignment method of the eye E will be described in detail with reference to FIG. FIG. 3 is a schematic diagram illustrating an example of a screen displayed on the display unit 192. In step S <b> 101, the display control unit 191 displays the anterior segment image 201, the horizontal tomographic image 202, and the vertical tomographic image 203 on the display unit 192. The anterior segment image 201 is generated by the anterior segment camera 165. The anterior segment image 201 is an anterior segment tomographic image generated by the image generation unit 193 from the optical beat signal detected by the differential amplifier 136 by scanning the eye E with the X scanner 107 in the horizontal direction. The vertical tomographic image 203 is an anterior segment tomographic image generated by the image generation unit 193 from the optical beat signal detected by the differential amplifier 136 when the Y scanner 110 scans the eye E in the vertical direction.

  Then, as shown in FIG. 3, the display control unit 191 displays, for example, the anterior segment image display area 21, the horizontal tomographic image display area 22, and the vertical tomographic image display area 23 on the display screen of the display unit 192. The map display area 24 and the angle display area 220 are provided to display information. The anterior segment image display area 21 is an area for displaying the anterior segment image 201. The horizontal tomographic image display area 22 is an area for displaying the horizontal tomographic image 202. The vertical tomographic image display area 23 is an area for displaying the vertical tomographic image 203. The map display area 24 is an area for displaying a three-dimensional map 216 of the equator position of the crystalline lens 222 described later. The angle display area 220 is an area for displaying a value of an angle 219 in the maximum diameter direction 218 of the crystalline lens 222 described later.

  Since the measurement light is blocked by the iris 221, a portion of the crystalline lens 222 that overlaps the iris 221 and the eye optical axis 317 is not reflected in the horizontal tomographic image 202. For this reason, in the horizontal tomographic image 202 displayed in the horizontal tomographic image display area 22 of the display unit 192, the lens 222 is not projected in a portion overlapping the iris 221 in the eye optical axis direction. Similarly, since the measurement light is blocked by the eyelid 223, the vertical tomographic image 203 does not include a portion of the crystalline lens 222 that overlaps the eyelid 223 in the direction of the eye optical axis. For this reason, in the vertical tomographic image 203 displayed in the vertical tomographic image display area 23 of the display unit 192, the crystalline lens 222 is not projected in a portion overlapping the eyelid 223 in the eye optical axis direction.

  Next, the alignment processing unit 199 detects the pupil center 206 shown in the anterior eye image 201 from the image data of the anterior eye image 201. The drive control unit 180 controls the X scanner 107 and the Y scanner 110 to scan through the detected pupil center 206, and performs live view imaging of the horizontal tomographic image 202 and the vertical tomographic image 203. Note that the display control unit 191 displays the horizontal scan line 207 and the vertical scan line 208 in an overlapping manner on the anterior segment image displayed in the anterior segment image display area 21. The tomographic image on the horizontal scan line 207 is the horizontal tomographic image 202, and the tomographic image on the vertical scan line 208 is the vertical tomographic image 203.

  The alignment processing unit 199 detects two contact points 209 and 210 at the left and right of the distal end of the lens 222 and the iris 221 from the image data of the horizontal tomographic image 202. Similarly, the alignment processing unit 199 detects two contact points 212 and 213 at the upper and lower portions of the distal end portion of the crystalline lens 222 and the iris 221 from the image data of the vertical tomographic image 203. The alignment processing unit 199 determines an alignment line 211 that connects the two left and right contact points 209 and 210 and an alignment line 214 that connects the two upper and lower contact points 212 and 213. The display control unit 191 displays the determined alignment lines 211 and 214 superimposed on the horizontal tomographic image 202 and the vertical tomographic image 203, respectively.

  The angles of the alignment lines 211 and 214 with respect to the horizontal direction in the drawing (the direction perpendicular to the incident direction of the measurement light) vary depending on the fixation position of the eye E to be examined. Therefore, the drive control unit 180 changes the display position of the internal fixation lamp 170 so that the alignment line 211 of the horizontal tomographic image 202 and the alignment line 214 of the vertical tomographic image 203 are simultaneously horizontal (perpendicular to the incident direction of the measurement light). adjust. In a state where the alignment line 211 and the alignment line 214 are simultaneously horizontal, the measurement light is incident on the eye E substantially coincident with the eye optical axis. This state is a state in which the angle of the eye E is aligned. The drive controller 180 may automatically adjust the display position of the internal fixation lamp 170 so that the alignment lines 211 and 214 are horizontal. The angle alignment of the eye E may be a method of irradiating the eye E with light from an appropriate light source, capturing the Purkinje image with a camera, and detecting the angle of the eye E from the Purkinje image. .

<Anterior segment tomographic imaging> to <Image generation>
In “anterior segment tomographic imaging” in step S102, the drive control unit 180 controls the light source 101 to irradiate the eye E with measurement light. Then, the drive control unit 180 controls the X scanner 107 and the Y scanner 110 to scan the anterior segment Ea. The differential amplifier 136 receives interference light between the return light of the measurement light from the anterior segment Ea and the reference light, and detects a beat. The detected beat is input to the analog / digital conversion circuit 137 as a beat signal of an analog electric signal. The analog / digital conversion circuit 137 discretely samples the optical beat signal of the analog electric signal input from the differential amplifier 136 at regular wave intervals in synchronization with the k-clock input from the light source 101. Thereby, the optical beat signal is converted into a digital electric signal. Then, the optical beat signal converted into the digital electric signal is transmitted to the image generation unit 193.

  In “image generation” in step S103, the image generation unit 193 generates a plurality of anterior segment tomographic images, which are examples of two-dimensional tomographic images. In this step, the image generation unit 193 generates a plurality of anterior segment tomographic images corresponding to the number of scans. Each of the plurality of generated anterior segment tomographic images indicates the sectional structure of the anterior segment Ea at the position of the corresponding scan line (the sectional structure when cut by the scan line).

  Here, a scan pattern in scanning by the X scanner 107 and the Y scanner 110 will be described in detail with reference to FIG. FIG. 4 is a diagram schematically illustrating an example of a scan pattern when an anterior segment tomographic image is captured. In anterior ocular segment tomographic imaging, a radial scan is performed according to a radial scan pattern 303 centered on the pupil center 206 (eye optical axis), which is the center of the pupil 205. Specifically, a range wider than the pupil 205 is scanned along a scan line passing through the pupil center 206 or the vicinity thereof. Further, the scan line is rotated around the pupil center 206 (eye axis light), and the eye E is scanned in 32 directions at equal intervals. Note that at the time of imaging an anterior segment tomographic image, scanning is performed with the eyelid raised so that the eyelid of the eye E is not covered by the pupil. At this time, an eye opener may be used to raise the eyelid.

  FIG. 5 is a diagram schematically illustrating an example of one anterior segment tomographic image 301 among a plurality of anterior segment tomographic images 301 generated by the image generation unit 193. The anterior segment tomographic image 301 includes a cornea 311, an iris 221, and a part of a crystalline lens 222 (including its front and rear surfaces). In FIG. 5, reference numeral “315” indicates the front surface of the crystalline lens, and “316” indicates the rear surface of the crystalline lens. The display control unit 191 displays the ocular optical axis 317 passing through the center of the pupil in an overlay display on the anterior segment tomographic image 301 displayed on the display unit 192. As described above, since the measurement light is blocked by the iris 221, the crystalline lens 222 is not reflected in the region 314 (the lower side in FIG. 5) that overlaps the iris 221 in the direction of the eye optical axis 317. For this reason, the equator portion of the crystalline lens 222 is not shown in the anterior segment tomographic image 301.

  The number of radial scans (the number of scan lines) is not limited to 32, and may be 32 or more. This is because the higher the number of radial scans, the higher the density of data that can be acquired. In addition, a mydriatic may be preliminarily applied to the eye E in order to capture a wider range of the lens 222 in the anterior segment tomographic image capturing. Further, the radial scan pattern 303 may be a scan pattern in which a part of the scan area is missing.

<Image analysis>
Next, the image analysis in step S201 will be described. The image analysis process is an example of an image processing method executed by the image processing apparatus. For the image analysis, the lens boundary portion approximation processing in step S104, the lens equator position determination in step S105, the three-dimensional map of the lens equator portion in step 106, and the maximum radial angle of the lens in step S107 Measurement.

  The approximation processing of the lens boundary part in step S104 and the method for determining the lens equatorial part position in step S105 will be described with reference to FIG. FIG. 6 is a diagram illustrating an example of a state in which the approximate curve 324 of the front surface 315 of the lens and the approximate curve 325 of the back surface 316 of the lens are overlaid on the tomographic image 301 of the anterior eye. In step S104, the approximation processing unit 196 functions as an approximation processing unit. In step S105, the curve intersection calculation unit 197 functions as an equator determination unit. The approximation processing unit 196 detects the lens front surface 315 shown in the anterior segment tomographic image 301 and fits the detected lens front surface 315 with the approximate curve 324. Similarly, the lens rear surface 316 shown in the anterior segment tomographic image 301 is detected, and the detected lens rear surface 316 is fitted with the approximate curve 325. Here, an example in which circles (arcs) are applied as the approximate curves 324 and 325 is shown. However, the approximate curves 324 and 325 for fitting the lens front surface 315 and the lens rear surface 316 are not limited to circles (arcs). For example, it may be a quadratic curve or another curve. In addition, the above-mentioned instillation of the mydriatic agent to the eye E is for obtaining the lens equator position with high accuracy by widening the pupil 205 to image the lens.

  In “determination of the lens equator position” in step S105, the curve intersection calculation unit 197 has two intersections (reference numerals “322” and “323”) of the approximate curve 324 of the lens front surface 315 and the approximate curve 325 of the lens rear surface 316. Position) is calculated. Then, the curve intersection calculation unit 197 determines the calculated positions of the two intersections as the lens equator positions 322 and 323. Thereby, the crystalline lens equator positions 322 and 323 which are not shown in the anterior segment tomographic image 301 are determined. Further, the curve intersection calculation unit 197 calculates a line segment 321 connecting the lens equator positions 322 and 323. The length of this line segment 321 (the distance between the two lens equator positions 322 and 323) is the lens equator diameter in each anterior segment tomographic image 301. Then, the curve intersection calculation unit 197 calculates the lens equator positions 322 and 323 and the lens equator diameter for all of a plurality (32 in the present embodiment) of the anterior segment tomographic image 301 acquired in step S102. As described above, by executing steps S104 and S105, the lens equator positions 322 and 323 can be determined (calculated) even when the measurement light is blocked by the iris 221 and the lens equator is not captured in the image.

  Next, “creating a three-dimensional map of the crystalline lens equator” in step S106 will be described with reference to FIG. FIG. 7 is an example of a top view of a three-dimensional map of the crystalline lens equator. In step S106, the three-dimensional map processing unit 198 functions as an example of a three-dimensional map creation unit. The three-dimensional map processing unit 198 plots the lens equator positions 322 and 323 (that is, the positions of the two intersections) in the 32 anterior segment tomographic images 301 determined in step S105 in a three-dimensional space. At this time, the positions of the eye optical axes 317 of the 32 anterior segment tomographic images 301 are matched, and the directions of the lens equator positions 322 and 323 are matched with the directions of the respective scan lines in the radial scan pattern 303. In other words, the lens equator positions 322 and 323 determined from the anterior segment tomographic image 301 in each scan line are relative to each other on the three-dimensional coordinates with the eye optical axis 317 passing through the pupil center 206 as the coordinate origin. Plot while maintaining a typical angular relationship. As a result, discrete three-dimensional plots of the lens equator where the positions corresponding to the lens equator positions 322 and 323 shown in FIG. 6 are black circle points such as the lens equator positions 322 and 323 shown in FIG. 7 are obtained. It is done.

  Further, the three-dimensional map processing unit 198 smoothly connects the discrete three-dimensional plots of the lens equator positions 322 and 323 by, for example, spline interpolation. Thereby, a three-dimensional closed curve is obtained. The three-dimensional closed curve thus obtained is a three-dimensional map 216 of the crystalline lens equator. The method of connecting the lens equator positions 322 and 323 is not limited to spline interpolation, and may be linear interpolation or other interpolation methods, for example. Also, polynomial fitting or other fitting methods may be used.

Next, “measurement of the angle in the maximum diameter direction of the crystalline lens” in step S107 will be described with reference to FIG. In step S107, the three-dimensional map processing unit 198 functions as a maximum radial direction calculating unit, and calculates an angle 219 of the maximum radial direction 218 of the crystalline lens 222 with respect to the reference direction. FIG. 8 is a diagram in which a straight line 341 indicating the maximum diameter is superimposed on the three-dimensional map 216 of the crystalline lens equator created in step S106. This straight line 341 is a straight line in which the distance between two intersections (that is, lens equator positions 322 and 323) of the three-dimensional map 216 is the largest among the straight lines passing through the pupil center 206. The maximum diameter of the crystalline lens 222 is calculated as the distance D _L between two intersections of the three-dimensional map 216 on the set straight line 341 when the straight line 341 as described above is set. For example, the three-dimensional map processing unit 198 sets a straight line that passes through the pupil center 206, and calculates the distance between two intersections of the set straight line and the three-dimensional map 216. Then, the three-dimensional map processing unit 198 rotates this straight line around the pupil center 206 and calculates this distance over the entire circumference of the three-dimensional map 216. Then find the maximum value. This maximum value is the maximum diameter of the crystalline lens 222. The direction of the straight line 341 when this distance takes the maximum value is the maximum radial direction 218. An angle 219 in the maximum radial direction 218 is calculated as an angle between the straight line 341 and the reference direction. In the present embodiment, the horizontal direction is applied as the reference direction. However, the reference axis is not limited to the horizontal axis 217. The direction of the reference axis can be set as appropriate. In general, it is said that the eye E rotates by an average of 2.2 ° between the sitting position (when sitting) and the supine position (facing up).

  Here, a second example of the three-dimensional map 216 will be described with reference to FIG. FIG. 9 is a diagram showing a second example of the three-dimensional map 216 of the crystalline lens equator. As shown in FIG. 9, even when the three-dimensional map 216 of the crystalline lens equator is a meandering closed curve, it can be calculated by the same method as described with reference to FIG. That is, even in such a case, the maximum diameter of the crystalline lens 222 is set as a straight line passing through the pupil center 206, and the maximum distance between two intersections between the set straight line and the three-dimensional map 216 of the crystalline lens equator part is set. It can be calculated as a value. Similarly, the angle 219 between the horizontal axis 217 and the straight line 341 where the distance between the two intersection points with the three-dimensional map 216 of the crystalline lens equator passing through the pupil center 206 is the angle in the maximum radial direction 218 of the crystalline lens 222. 219 is calculated.

<Output>
In “output” in step S108, the generated image and the analysis result are output. First, when the creation of the three-dimensional map 216 and the calculation of the angle 219 in the maximum radial direction 218 are completed, the three-dimensional map processing unit 198 generates output information for displaying them on the display unit 192. For example, the three-dimensional map processing unit 198 generates, as output information, image data that displays a three-dimensional map 216 with a horizontal axis 217 and a straight line 341 indicating the maximum diameter direction 218 superimposed. Using this output information, the display control unit 191 displays the three-dimensional map 216 in the map display area 24 and displays the value of the angle 219 in the maximum radial direction 218 in the angle display area 220. Thereby, the examiner can grasp the shape of the equator part position of the crystalline lens 222 of the eye E to be examined three-dimensionally. Further, the angle 219 in the maximum radial direction 218 can be grasped.

  According to the present embodiment, by creating the three-dimensional map 216 indicating the equator position of the crystalline lens 222, the shape of the crystalline lens equator can be obtained three-dimensionally. Furthermore, an angle 219 in the maximum diameter direction 218 of the crystalline lens 222 can be calculated from the created three-dimensional map 216.

  By using the image processing method of the present embodiment, the toric intraocular lens can be customized so that the support portion of the toric intraocular lens faces the maximum diameter direction of the crystalline lens capsule for each eye to be examined. That is, in the preoperative examination of cataract surgery using a toric intraocular lens, a three-dimensional map of the equator position of the crystalline lens is created using the image processing method of the present embodiment, and the maximum diameter direction of the crystalline lens capsule is obtained. Good. Then, in the operation of cataract surgery, the support portion of the intraocular lens can be stably supported in the lens capsule by using the calculated angle in the maximum diameter direction of the lens capsule. Therefore, the axial shift of the intraocular lens can be suppressed. Since the lens capsule is an eye tissue constituting the surface of the lens 222, the angle in the maximum diameter direction of the lens capsule coincides with the angle 219 in the maximum diameter direction 218 of the lens 222 calculated by the above-described processing.

  Here, a method for customizing the toric intraocular lens for each eye to be examined using the angle in the maximum diameter direction of the crystalline lens (the crystalline lens capsule) will be described. FIG. 10 is a flowchart showing an example of a method for customizing a toric intraocular lens for each eye to be examined according to this embodiment. In this embodiment, the toric intraocular lens is customized so that the maximum radial direction of the support portion of the toric intraocular lens matches the maximum radial direction of the crystalline lens according to the eye to be examined. Thereby, the support part of the toric intraocular lens can be stably supported in the crystalline lens capsule of the eye E to be examined.

  Step S401 is a step of measuring the eye E. This step S401 includes “measurement in the weak principal meridian direction of the cornea of the subject eye” in step S301 and “measurement of the angle in the maximum diameter direction of the lens capsule” in step S302.

  First, the measurement in the weak principal meridian direction of the cornea 311 of the subject eye E in step S301 will be described. The weak principal meridian direction of the cornea 311 of the subject eye E is equivalent to the astigmatic axis. A corneal shape analyzer or an autokeratometer is used to measure the weak main meridian. If the subject's head is misaligned during measurement, the weak principal meridian direction cannot be measured accurately. Therefore, at the time of measurement, the forehead portion of the subject is maintained in a state where the subject's forehead is in contact with a not-shown fixing plate or the like. Further, since the shift of the angle of the eye E leads to the shift of the weak main meridian, the angle of the eye E is aligned so that the angle of the eye E does not shift.

  Next, in step S302, the angle in the maximum diameter direction of the lens capsule is measured. As described above, the angle 219 in the maximum diameter direction 218 of the crystalline lens 222 calculated by the image processing method of the present embodiment matches the angle in the maximum radial direction of the crystalline lens capsule obtained in step S302. Therefore, in step S302, first, the angle 219 in the maximum radial direction 218 of the crystalline lens 222 of the eye E is measured using the method described above. Then, the measured angle 219 with respect to the reference axis (horizontal axis 217 in the present embodiment) in the maximum diameter direction 218 of the crystalline lens 222 is set as the angle in the maximum diameter direction of the crystalline lens capsule.

  In “create customized toric intraocular lens” in step S303, the toric intraocular lens 351 is created using the angle 219 in the maximum diameter direction 218 of the crystalline lens 222 measured in step S302. FIG. 11 is a front view schematically showing a configuration example of the customized toric intraocular lens 351. FIG. 12 is a side view schematically showing a configuration example of the toric intraocular lens 351. As shown in FIGS. 11 and 12, the toric intraocular lens 351 includes a lens portion 352 that is a lens body and two support portions 353 that support the lens portion 352 in the crystalline lens capsule. The two support portions 353 are elastically deformable (have elasticity) and extend outward from the peripheral edge of the lens portion 352 in plan view. The two support portions 353 are formed in a loop shape or a plate shape, for example. The two support portions 353 are configured such that the maximum diameter direction 354 of the support portion 353 coincides with the angle 219 of the maximum diameter direction 218 of the crystalline lens 222 calculated in S302. Note that the maximum radial direction 354 of the support portion 353 is a direction in which the tip portions of the two support portions 353 pass through each other, and a direction in which the dimension between the tip portions of the two support portions 353 is maximized. . The two support portions 353 can be elastically deformed at least in the maximum radial direction 354. In other words, the distance between the tip portions of the two support portions 353 (the dimension in the maximum radial direction 354) can be changed elastically. Further, the angle 343 of the lens portion 352 with respect to the horizontal axis 217 in the strong principal radial direction is configured to coincide with the weak principal meridian direction 355 of the cornea 311 of the eye E measured in S301. Further, an axis mark 356 is stamped on the periphery of the lens portion 352 in the strong principal meridian direction. The axis mark 356 is used for alignment in the rotational direction when the toric intraocular lens 351 is inserted. The toric intraocular lens 351 is created to have these configurations.

  In “insertion of an intraocular lens into the subject's eye” in step S304, the toric intraocular lens 351 created in step S303 is inserted into the eye of the eye E and fixed. For the insertion and fixing of the toric intraocular lens 351, for example, the following method can be applied. First, the marking 371 of 2 points | pieces is attached | subjected to the weak principal meridian direction of the cornea periphery part of the eye E (refer FIG. 14). The marking 371 is attached by, for example, scratching a predetermined position of the cornea 311 with a needle-like instrument called a hook and staining it with a marker. The toric intraocular lens 351 can be inserted by a general cataract surgery procedure. That is, first, the cornea 311 or the sclera is incised, a continuous circular anterior capsular incision is performed, and the clouded lens 222 is crushed and removed by ultrasonic emulsification and aspiration. As a result, only the lens nucleus and the cortex are removed, and the lens capsule corresponding to the bag of the lens 222 is left. Then, the toric intraocular lens 351 is inserted into the lens capsule.

  FIG. 13 is a diagram schematically showing the anterior segment tomographic image 301 in a state where the toric intraocular lens 351 is inserted. The lens capsule 363 is opened by the continuous circular anterior capsulotomy described above. Reference numeral “364” in FIG. 13 indicates an opening of the lens capsule 363 by continuous circular anterior capsulotomy. As described above, the two support portions 353 extend outward from the peripheral portion of the lens portion 352 and are formed in a loop shape or a plate shape that can be elastically deformed (has elasticity). The two support portions 353 can elastically expand and contract in the maximum diameter direction 354. For this reason, the toric intraocular lens 351 is fixed when the two support portions 353 are elastically stretched to the crystalline lens equator portion 365 while being inserted into the crystalline lens capsule 363. In addition, the lens capsule 363 is fixed and fixed to the eye tissue within the eye by a chin band 362 that is a plurality of filamentous tissues. Reference numeral “361” in FIG. 13 indicates an incision incised through the cornea 311 or the sclera as an opening for inserting the toric intraocular lens 351.

  Next, “alignment of the intraocular lens” in step S305 is performed. Step S305 will be described with reference to FIG. FIG. 14 is a front view schematically showing the anterior segment Ea in a state where the toric intraocular lens 351 is inserted. In the alignment of the toric intraocular lens 351, a marking 371 applied in the weak principal meridian direction of the cornea 311 of the subject eye E, and an axial mark 356 in the strong principal meridian direction stamped on the lens portion 352 of the toric intraocular lens 351, Match. The alignment of the toric intraocular lens 351 is performed, for example, by inserting tweezers or the like into the cornea 311 or the scleral opening 361 and rotating the toric intraocular lens 351. FIG. 15 is a front view schematically showing the lens capsule 363 in a state where the toric intraocular lens 351 is inserted. When the alignment of the toric intraocular lens 351 is completed, the weak main radial direction 382 of the cornea 311 of the eye E to be examined and the strong main radial direction 383 of the lens portion 352 coincide as shown in FIG. The maximum diameter direction 354 of the two support portions 353 and the maximum diameter direction 218 of the crystalline lens capsule 363 of the eye E to be examined coincide with each other.

  The toric intraocular lens 351 according to the present embodiment is most effective in correcting astigmatism when the direction of the strong principal diameter of the lens portion 352 matches the weak principal diameter of the eye E. In this state, since the two support portions 353 are positioned in the maximum diameter direction 218 of the lens capsule 363, the toric intraocular lens 351 is most stable in the lens capsule 363. Therefore, axial displacement of the toric intraocular lens 351 can be suppressed after cataract surgery.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. For example, the configuration of the control unit 200 is not limited to the configuration described above. The control unit 200 may be configured by a single piece of hardware, or may be configured by a plurality of pieces of hardware working together. Further, as described above, the display unit 192 may not be included in the control unit 200. Furthermore, the control unit 200 may have an external storage medium, and a computer program for controlling the ophthalmologic apparatus 1 may be stored in the external storage medium so as to be readable by a computer. In this case, the CPU reads the computer program from the external storage medium and executes it.

  Further, the image analysis unit 190 may not be included in the control unit 200. In this case, a computer in which the image analysis unit 190 includes a CPU, a ROM, and a RAM is applied. The ROM stores a computer program for executing the image processing method according to the present embodiment. Then, the CPU reads out this computer program from the ROM, expands it appropriately in the RAM, and executes it. Accordingly, the computer functions as the image analysis unit 190 which is an example of the image processing apparatus, and the image processing method according to the present embodiment is executed.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, or the like) of the system or apparatus reads the program. It is a process to be executed. In this case, a computer-readable storage medium storing the program constitutes the present invention.

Claims (12)

Approximation processing means for approximating the front surface of the lens and the back surface of the lens with a curve for each of a plurality of anterior ocular segment tomographic images in which the front surface and the rear surface of the lens of the eye to be examined are reflected,
An equator determination means for determining an intersection of a curve that approximates the front surface of the lens and a curve that approximates the rear surface of the lens as a lens equator portion of the eye to be examined;
Three-dimensional map creating means for creating a three-dimensional map showing the crystalline lens equator;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, wherein the plurality of anterior ocular segment tomographic images are images captured by a radial scan centered on an eye optical axis of the eye to be examined.   The three-dimensional map creating means creates the three-dimensional map by interpolating the positions of the crystalline equator portions of the plurality of anterior segment tomographic images determined by the equator determining unit. The image processing apparatus according to claim 1.   4. The image processing apparatus according to claim 1, further comprising a maximum radial direction calculating unit that calculates a maximum radial direction of the lens of the eye to be examined from the three-dimensional map. 5.   The maximum radial direction calculating means sets a straight line passing through the pupil center of the eye to be examined in the three-dimensional map, and a distance between two intersections between the straight line and the equator of the three-dimensional map is maximized. The image processing apparatus according to claim 4, wherein an angle of the straight line with respect to a reference direction is an angle in the maximum radial direction. An approximation step for approximating the front surface of the lens and the back surface of the lens with a curve for each of a plurality of anterior segment tomographic images in which the front surface and the rear surface of the lens of the eye to be examined are reflected,
An equator determination step for determining an intersection of a curve that approximates the front surface of the lens and a curve that approximates the rear surface of the lens as the equator portion of the eye to be examined;
A three-dimensional map creation step of creating a three-dimensional map showing the crystalline lens equator;
An image processing method comprising:   The image processing method according to claim 6, wherein the plurality of anterior segment tomographic images are tomographic images captured by a radial scan centered on an eye optical axis of the eye to be examined.   In the three-dimensional map creation step, the three-dimensional map is created by interpolating the positions of the lens equator portions of the plurality of anterior segment tomographic images determined in the equator determination step. The image processing method according to claim 6 or 7.   The image processing method according to any one of claims 6 to 8, further comprising a maximum radial direction calculating step of calculating a maximum radial direction of the crystalline lens of the eye to be examined from the three-dimensional map.   In the maximum radial direction calculating step, a straight line passing through the pupil center of the eye to be examined is set in the three-dimensional map, and the distance between two intersections between the straight line and the equator of the three-dimensional map is maximized. The image processing method according to claim 9, wherein an angle of the straight line with respect to a reference direction is an angle in the maximum radial direction.   A program causing a computer to execute the image processing method according to any one of claims 7 to 10. The lens part,
A support portion extending from a peripheral portion of the lens portion;
Have
The direction of the strong principal diameter line of the lens portion coincides with the weak principal diameter line of the cornea of the eye to be examined, and the maximum diameter direction of the support portion coincides with the maximum diameter direction of the lens capsule of the eye to be examined. Toric intraocular lens.

Images