Ophthalmic device, control method thereof, program, and recording medium

Abstract

To perform highly reliable eye axial length measurement even when opacity moves in a vitreous body.SOLUTION: An ophthalmologic apparatus according to an embodiment performs the first OCT scan on a first region including a first portion after performing alignment by acquiring first deviation information of a subject eye, performs the second OCT scan on a second region including a second portion after performing alignment by acquiring second deviation information, and calculates a distance between the first portion and the second portion based on the first and second data obtained respectively in the first and second OCT scans. The ophthalmologic apparatus further determines whether or not the data obtained by applying the OCT scan in the first scan mode to a subject eye satisfies a scan mode shifting condition, and applies the OCT scan in the second scan mode different from the first scan mode to the subject eye when the scan mode shifting condition is not satisfied even when the OCT scan in the first scan mode is repeated in the prescribed number of times.SELECTED DRAWING: Figure 3B

Description

[Technical field]

[0001] The present invention relates to an ophthalmic apparatus, a control method thereof, a program, and a recording medium. [Background technology]

[0002] There are known ophthalmic devices capable of measuring axial length. For example, Patent Document 1 discloses a technique for measuring axial length using optical coherence tomography (OCT). Axial length is defined as the distance between the corneal apex and the macula (fovea), and is one of the intraocular parameters useful for selecting the power of an intraocular lens before cataract surgery, checking axial refractive error, and the like.

[0003] As described above, since the axial length is defined as the distance between the corneal apex and the macula, it is necessary to know both the position of the cornea and the position of the retina in order to measure the axial length. In the invention disclosed in Patent Document 1, there is a time lag between the first measurement (OCT scan in anterior segment mode) for determining the position of the cornea and the second measurement (OCT scan in posterior segment mode) for determining the position of the retina. Therefore, if the subject's eye moves between the first and second measurements, the axial length may not be measured accurately. In particular, movement in a direction perpendicular to the depth direction of the subject's eye may significantly reduce the reliability of the measured value of the axial length. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-19634 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a technique capable of performing highly reliable axial length measurement, even in a subject's eye suffering from floaters, for example, when opacity moves within the vitreous body. [Means for solving the problem]

[0006] A first aspect of an exemplary embodiment includes a scanning unit that applies an optical coherence tomography (OCT) scan to a subject's eye, a moving mechanism that moves at least a part of the scanning unit, a deviation measuring unit that measures deviation of the subject's eye relative to a predetermined reference position, a scan control unit that executes a first scan control that causes the scanning unit to execute an OCT scan on a first region including a first part of the subject's eye, and a second scan control that causes the scanning unit to execute an OCT scan on a second region including a second part different from the first part, and a control unit that performs a first scan control that causes the scanning unit to execute an OCT scan on a second region including a second part different from the first part. An ophthalmologic apparatus including: an alignment control unit that executes a first alignment control for controlling the moving mechanism based on first deviation information of the subject's eye acquired by a position measurement unit; a second alignment control for controlling the moving mechanism based on second deviation information of the subject's eye acquired by the deviation measurement unit before the second scan control; and a distance calculation unit that calculates a distance between the first portion and the second portion based on first data acquired by the scan unit under the first scan control and second data acquired by the scan unit under the second scan control. The scan control unit may be configured to control the scan unit to apply an OCT scan of a first scan mode to the subject's eye, determine whether data obtained by the OCT scan of the first scan mode satisfies a scan mode transition condition, and control the scan unit to apply an OCT scan of a second scan mode different from the first scan mode to the subject's eye when the scan mode transition condition is not satisfied even after the OCT scan of the first scan mode is repeated a predetermined number of times.

[0007] A second aspect of an exemplary embodiment is an ophthalmic device of the first aspect, wherein the scanning unit includes an interference optical system including a measurement arm that guides measurement light to the test eye and a reference arm that guides reference light, and an arm length change unit provided in at least one of the measurement arm and the reference arm that changes the arm length under the control of the scan control unit, and the distance calculation unit calculates a difference between a first arm length applied in the first scan control and a second arm length applied in the second scan control, analyzes the first data to identify a first position corresponding to the first portion, analyzes the second data to identify a second position corresponding to the second portion, and calculates the distance based on the difference, the first position, and the second position.

[0008] A third aspect of an exemplary embodiment is an ophthalmologic apparatus including a scanning unit that applies an optical coherence tomography (OCT) scan to a test eye, a deviation measuring unit that measures deviation of the test eye relative to a predetermined reference position, a scan control unit that executes a first scan control that causes the scanning unit to perform an OCT scan on a first region including a first region of the test eye, and a second scan control that causes the scanning unit to perform an OCT scan on a second region including a second region different from the first region, and a distance calculation unit that calculates a distance between the first region and the second region based on at least one of first deviation information of the test eye acquired by the deviation measuring unit in response to the first scan control and second deviation information of the test eye acquired by the deviation measuring unit in response to the second scan control, first data acquired by the scanning unit under the first scan control and second data acquired by the scanning unit under the second scan control. The scan control unit may be configured to control the scan unit to apply an OCT scan of a first scan mode to the test eye, determine whether or not data obtained by the OCT scan of the first scan mode satisfies a scan mode transition condition, and control the scan unit to apply an OCT scan of a second scan mode different from the first scan mode to the test eye if the scan mode transition condition is not satisfied even after repeating the OCT scan of the first scan mode a predetermined number of times.

[0009] A fourth aspect of an exemplary embodiment is the ophthalmologic apparatus of the third aspect, wherein the deviation measurement unit further includes a moving mechanism that acquires one deviation information corresponding to one of the first scan control and the second scan control, and acquires the other deviation information before the other scan control, and moves at least a part of the scan unit, and an alignment control unit that performs alignment control to control the moving mechanism based on the other deviation information before the other scan control, and the distance calculation unit calculates the distance based on the one deviation information, the first data, and the second data.

[0010] A fifth aspect of an exemplary embodiment is an ophthalmologic apparatus of the third or fourth aspect, wherein the scanning unit includes an interference optical system including a measurement arm that guides measurement light to the test eye and a reference arm that guides reference light, and an arm length change unit provided in at least one of the measurement arm and the reference arm that changes the arm length under the control of the scan control unit, and the distance calculation unit calculates a difference between a first arm length applied in the first scan control and a second arm length applied in the second scan control, analyzes the first data to identify a first position corresponding to the first portion, analyzes the second data to identify a second position corresponding to the second portion, and calculates the distance based on the difference, the first position, the second position, and at least one of the first deviation information and the second deviation information.

[0011] A sixth aspect of an exemplary embodiment is an ophthalmic device of the fifth aspect, characterized in that the distance calculation unit calculates a provisional distance between the first portion and the second portion based on the difference, the first position, and the second position, and calculates the distance based on the provisional distance, at least one of the first deviation information and the second deviation information, and a corneal curvature radius of the test eye that has been acquired in advance.

[0012] A seventh aspect of an exemplary embodiment is an ophthalmic device of the sixth aspect, characterized in that, when the temporary distance is ALm, one of the first deviation information and the second deviation information is h, the corneal curvature radius is r, and the distance is AL, the distance calculation unit calculates the distance AL by the calculation formula AL=(rr×cos(arcsin(h / r)))+ALm×cos(arcsin(h / ALm)).

[0013] An eighth aspect of an exemplary embodiment is an ophthalmic device of any of the first to seventh aspects, characterized in that the scan control unit causes the scan unit to perform multiple OCT scans in at least one of the first scan control and the second scan control, and the distance calculation unit acquires a single piece of data from a group of data acquired by the multiple OCT scans, and calculates the distance using the single piece of data.

[0014] A ninth aspect of an exemplary embodiment is an ophthalmic device of the eighth aspect, characterized in that the distance calculation unit generates the single data by averaging the group of data.

[0015] A tenth aspect of an exemplary embodiment is an ophthalmic device of any of the first to seventh aspects, wherein the scan control unit causes the scan unit to perform an OCT scan of a three-dimensional region of the test eye in at least one of the first scan control and the second scan control, and the distance calculation unit analyzes data acquired by the OCT scan of the three-dimensional region to identify a feature position corresponding to a feature point of the test eye, and calculates the distance as the length of a line segment having one end at the feature position.

[0016] An eleventh aspect of an exemplary embodiment is an ophthalmic device of the tenth aspect, characterized in that, in the first scan control, the scan control unit causes the scan unit to perform an OCT scan of a three-dimensional area including the corneal surface of the test eye, and the distance calculation unit analyzes data obtained by the OCT scan of the three-dimensional area to identify a feature position corresponding to the corneal apex.

[0017] A twelfth aspect of an exemplary embodiment is an ophthalmic device of any of the first to eleventh aspects, wherein the scan control unit determines whether or not the data obtained by the OCT scan in the second scan mode satisfies the scan mode transition condition, and if the scan mode transition condition is not satisfied even after repeating the OCT scan in the second scan mode a predetermined number of times, controls the scan unit to apply an OCT scan of a third scan mode different from the second scan mode to the test eye, and the first scan mode is an A scan, the second scan mode is a B scan, and the third scan mode is a radial scan.

[0018] A thirteenth aspect of an exemplary embodiment is an ophthalmic device of any of the first to twelfth aspects, characterized in that the scan control unit controls the scan unit to apply an OCT scan of the second scan mode to a position different from the OCT scan of the first scan mode, and / or to apply an OCT scan of the second scan mode to a wider range than the OCT scan of the first scan mode.

[0019] A fourteenth aspect of an exemplary embodiment is an ophthalmic device of any of the first to thirteenth aspects, characterized in that the scan control unit controls the scan unit so that the first area and / or the second area do not fall outside the application range of the OCT scan.

[0020] A fifteenth aspect of an exemplary embodiment is a method for controlling an ophthalmic device including a scanning unit that applies an optical coherence tomography (OCT) scan to a test eye, a moving mechanism that moves at least a part of the scanning unit, and a deviation measurement unit that measures deviation of the test eye relative to a predetermined reference position, the method including a first alignment control step of controlling the moving mechanism based on first deviation information of the test eye acquired by the deviation measurement unit, a first scan control step of causing the scanning unit to perform an OCT scan on a first region including a first portion of the test eye, a second alignment control step of controlling the moving mechanism based on second deviation information of the test eye acquired by the deviation measurement unit, a second scan control step of causing the scanning unit to perform an OCT scan on a second region including a second portion different from the first portion, and a distance calculation step of calculating a distance between the first portion and the second portion based on first data acquired by the scanning unit in the first scan control step and second data acquired by the scanning unit in the second scan control step. A fifteenth aspect of an exemplary embodiment may further include the steps of controlling the scanning unit to apply an OCT scan of a first scan mode to the test eye, determining whether or not data obtained by the OCT scan of the first scan mode satisfies a scan mode transition condition, and controlling the scanning unit to apply an OCT scan of a second scan mode different from the first scan mode to the test eye if the scan mode transition condition is not satisfied even after repeating the OCT scan of the first scan mode a predetermined number of times.

[0021] A sixteenth aspect of an exemplary embodiment is a method for controlling an ophthalmic device including a scanning unit that applies an optical coherence tomography (OCT) scan to a test eye and a deviation measurement unit that measures deviation of the test eye relative to a predetermined reference position, the method including a first scan control step of causing the scanning unit to perform an OCT scan on a first region including a first portion of the test eye, a second scan control step of causing the scanning unit to perform an OCT scan on a second region including a second portion different from the first portion, a deviation measurement step of causing the deviation measurement unit to perform at least one of a step of acquiring first deviation information of the test eye in response to the first scan control and a step of acquiring second deviation information of the test eye in response to the second scan control, and a distance calculation step of calculating a distance between the first portion and the second portion based on at least one of the first deviation information and the second deviation information acquired by the deviation measurement step, the first data acquired by the scanning unit in the first scan control step, and the second data acquired by the scanning unit in the second scan control step. A sixteenth aspect of the exemplary embodiment may further include the steps of controlling the scanning unit to apply an OCT scan of a first scan mode to the test eye, determining whether or not data obtained by the OCT scan of the first scan mode satisfies a scan mode transition condition, and controlling the scanning unit to apply an OCT scan of a second scan mode different from the first scan mode to the test eye if the scan mode transition condition is not satisfied even after repeating the OCT scan of the first scan mode a predetermined number of times.

[0022] A seventeenth aspect of the exemplary embodiment is a program for causing a computer to execute the control method according to the fifteenth or sixteenth aspect.

[0023] An eighteenth aspect of the exemplary embodiment is a computer-readable non-transitory recording medium having the program of the seventeenth aspect recorded thereon. Effect of the Invention

[0024] According to the exemplary embodiment, it is possible to perform reliable axial length measurements despite the movement of the examined eye. [Brief description of the drawings]

[0025] [Figure 1] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Diagram 2] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Figure 3A] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Figure 3B] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Figure 4A] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Figure 4B] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Diagram 5] 1 is a schematic diagram illustrating an example of an operation that can be performed by an ophthalmic device according to an exemplary embodiment. [Figure 6] 11 is a flowchart illustrating an example of an operation that can be performed by an ophthalmic apparatus according to an exemplary embodiment. [Figure 7] 1 is a schematic diagram illustrating an example of a configuration of an ophthalmologic apparatus according to an exemplary embodiment. [Figure 8] 1 is a schematic diagram illustrating an example of an operation that can be performed by an ophthalmic device according to an exemplary embodiment. [Figure 9] 11 is a flowchart illustrating an example of an operation that can be performed by an ophthalmic apparatus according to an exemplary embodiment. [Figure 10] 11 is a flowchart illustrating an example of an operation that can be performed by an ophthalmic apparatus according to an exemplary embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] An ophthalmic apparatus according to an embodiment, a control method thereof, a program, and an exemplary embodiment of a recording medium will be described in detail with reference to the drawings. The ophthalmic apparatus according to the embodiment obtains data by applying an optical coherence tomography (OCT) scan to the subject's eye, thereby determining a distance between two different parts of the subject's eye. Typically, the ophthalmic apparatus according to the embodiment sequentially applies an OCT scan to the anterior and posterior segments of the subject's eye, and determines a value of the axial length from the obtained data.

[0027] In the following exemplary disclosure, an ophthalmic apparatus that combines a spectral domain OCT and a fundus camera will be described, but the embodiment is not limited thereto. The type of OCT is not limited to the spectral domain OCT, and may be, for example, a swept source OCT.

[0028] Spectral domain OCT is a technique in which light from a low-coherence light source is split into measurement light and reference light, the return light of the measurement light from the test object is superimposed on the reference light to generate interference light, the spectral distribution of this interference light is detected by a spectroscope, and an image is formed by performing a Fourier transform or the like on the detected spectral distribution.

[0029] Swept-source OCT is a technique in which light from a tunable light source is split into measurement light and reference light, and the return light of the measurement light from the test object is superimposed on the reference light to generate interference light. This interference light is detected by a photodetector such as a balanced photodiode, and an image is formed by performing a Fourier transform or the like on the detection data collected in response to the wavelength sweep and the measurement light scan.

[0030] In this way, the spectral domain OCT is an OCT method that acquires the spectral distribution by spatial division, and the swept source OCT is an OCT method that acquires the spectral distribution by time division. Note that the OCT methods that can be used in the embodiments are not limited to these, and it is also possible to adopt an embodiment that uses any OCT method other than these (for example, time domain OCT).

[0031] In this specification, unless otherwise specified, no distinction is made between "image data" and "image," which is visualized information based on the image data. Furthermore, unless otherwise specified, no distinction is made between a site or tissue of the subject's eye and an image obtained by visualizing the site or tissue.

[0032] First Embodiment In the first embodiment, an OCT scan (first OCT scan) is performed on a first region of the test eye after alignment is performed on the test eye, and an OCT scan (second OCT scan) is performed on a second region after alignment is performed again, and a distance between a first portion included in the first region and a second portion included in the second region is calculated based on first data obtained by the first OCT scan and second data obtained by the second OCT scan. This makes it possible to perform both the first OCT scan and the second OCT scan in a good alignment state, and it is possible to perform distance measurement with high reliability even if the test eye moves between the first OCT scan and the second OCT scan. An example of such an embodiment is disclosed below.

[0033] <composition> The exemplary ophthalmic apparatus 1 shown in FIG. 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic and control unit 200. The fundus camera unit 2 is provided with an optical system and a mechanism for acquiring a front image of the subject's eye E, and an optical system and a mechanism for performing OCT. The OCT unit 100 is provided with an optical system and a mechanism for performing OCT. The arithmetic and control unit 200 includes one or more processors configured to perform various processes (arithmetic, control, etc.). Furthermore, the ophthalmic apparatus 1 includes two anterior eye cameras 300 for photographing the anterior eye from two different directions.

[0034] The fundus camera unit 2 is provided with a chin rest and a forehead rest for supporting the face of the subject. The chin rest and the forehead rest correspond to the support section 340 shown in Figs. 4A and 4B. A drive mechanism and an arithmetic and control circuit are housed in the base 310. An optical system is housed in a housing 320 provided on the base 310. An objective lens 22 is housed in a lens housing section 330 provided to protrude from the front surface of the housing 320.

[0035] Furthermore, the ophthalmic apparatus 1 includes a lens unit for switching the part to which OCT is applied. Specifically, the ophthalmic apparatus 1 includes an anterior segment OCT attachment 400 for applying OCT to the anterior segment. The anterior segment OCT attachment 400 may be configured similarly to the optical unit disclosed in, for example, JP 2015-160103 A.

[0036] 1, the anterior segment OCT attachment 400 can be placed between the objective lens 22 and the subject's eye E. When the anterior segment OCT attachment 400 is placed in the optical path, the ophthalmic apparatus 1 can apply an OCT scan to the anterior segment. On the other hand, when the anterior segment OCT attachment 400 is retracted from the optical path, the ophthalmic apparatus 1 can apply an OCT scan to the posterior segment. The anterior segment OCT attachment 400 is moved manually or automatically.

[0037] In another embodiment, an OCT scan may be applied to the posterior segment when the attachment is disposed in the optical path, and an OCT scan may be applied to the anterior segment when the attachment is retracted from the optical path. In addition, the measurement site switched by the attachment is not limited to the posterior segment and the anterior segment, and may be any site of the eye. Note that the configuration for switching the site to which the OCT scan is applied is not limited to such an attachment, and it is also possible to adopt, for example, a configuration including a lens that can be moved along the optical path, or a configuration including a lens that can be inserted into and removed from the optical path.

[0038] In this embodiment, the "processor" is a circuit such as a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), a programmable logic device (e.g., SPLD (Simple Programmable Logic Device), CPLD (Complex Programmable Logic Device), or FPGA (Field Programmable Gate Array)). The processor realizes the functions according to the embodiment by, for example, reading and executing a program stored in a memory circuit or a storage device.

[0039] Fundus Camera Unit 2 The fundus camera unit 2 is provided with an optical system for photographing the fundus Ef of the subject's eye E. The acquired digital image of the fundus Ef (called a fundus image, fundus photograph, etc.) is generally a front image such as an observed image or a photographed image. The observed image is obtained by capturing a moving image using near-infrared light. The photographed image is a still image captured using a flash light in the visible range.

[0040] The fundus camera unit 2 includes an illumination optical system 10 and an imaging optical system 30. The illumination optical system 10 irradiates illumination light onto the subject's eye E. The imaging optical system 30 detects return light of the illumination light irradiated onto the subject's eye E. The measurement light from the OCT unit 100 is guided to the subject's eye E through an optical path within the fundus camera unit 2. Return light of the measurement light projected onto the subject's eye E (e.g., the fundus Ef) is guided to the OCT unit 100 through the same optical path within the fundus camera unit 2.

[0041] Light (observation illumination light) output from the observation light source 11 of the illumination optical system 10 is reflected by the concave mirror 12, passes through the condenser lens 13, and passes through the visible light cut filter 14 to become near-infrared light. The observation illumination light is then focused once near the photographing light source 15, reflected by the mirror 16, and passes through the relay lens system 17, the relay lens 18, the diaphragm 19, and the relay lens system 20 to be guided to the aperture mirror 21. The observation illumination light is then reflected at the periphery (area surrounding the hole) of the aperture mirror 21, passes through the dichroic mirror 46, and is refracted by the objective lens 22 to illuminate the subject's eye E (fundus Ef). The return light of the observation illumination light from the subject's eye E is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the hole formed in the central area of ​​the aperture mirror 21, passes through the dichroic mirror 55, passes through the photographing focusing lens 31, and is reflected by the mirror 32. Furthermore, this return light passes through the half mirror 33A, is reflected by the dichroic mirror 33, and is imaged on the light receiving surface of the image sensor 35 by the imaging lens 34. The image sensor 35 detects the return light at a predetermined frame rate. The focus of the photographing optical system 30 can be adjusted to match the fundus Ef or its vicinity, and can also be adjusted to match the anterior segment or its vicinity.

[0042] The light (imaging illumination light) output from the imaging light source 15 is irradiated onto the fundus Ef through the same path as the observation illumination light. The return light of the imaging illumination light from the subject's eye E is guided to the dichroic mirror 33 through the same path as the return light of the observation illumination light, passes through the dichroic mirror 33, is reflected by a mirror 36, and is imaged by an imaging lens 37 on the light receiving surface of an image sensor 38.

[0043] A liquid crystal display (LCD) 39 displays a fixation target (fixation target image). A part of the light beam output from the LCD 39 is reflected by the half mirror 33A, reflected by the mirror 32, passes through the photographing focusing lens 31 and the dichroic mirror 55, and passes through the hole of the aperture mirror 21. The light beam that passes through the hole of the aperture mirror 21 passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus Ef. The fixation target is typically used to guide and fix the gaze. The direction to which the gaze of the subject's eye E is guided (and fixed), that is, the direction to which the subject's eye E is encouraged to fixate, is called the fixation position.

[0044] The fixation position can be changed by changing the display position of the fixation target image on the screen of the LCD 39. Examples of fixation positions include a fixation position for acquiring an image centered on the macula, a fixation position for acquiring an image centered on the optic disc, a fixation position for acquiring an image centered on a position between the macula and the optic disc (center of the fundus), and a fixation position for acquiring an image of a site far away from the macula (periphery of the fundus).

[0045] A graphical user interface (GUI) or the like for specifying at least one of such typical fixation positions can be provided. Also, a GUI or the like for manually moving the fixation position (display position of the fixation target) can be provided. Also, a configuration for automatically setting the fixation position can be applied.

[0046] The configuration for presenting a fixation target with a changeable fixation position to the subject's eye E is not limited to a display device such as an LCD. For example, a device (fixation matrix) in which a plurality of light-emitting units (such as light-emitting diodes) are arranged in a matrix can be used instead of a display device. In this case, the fixation position of the subject's eye E based on the fixation target can be changed by selectively turning on the plurality of light-emitting units. As another example, a fixation target with a changeable fixation position can be generated by a device having one or more movable light-emitting units.

[0047] The alignment optical system 50 generates an alignment index used for aligning the optical system with respect to the subject's eye E. Alignment light output from a light-emitting diode (LED) 51 passes through an aperture 52, an aperture 53, and a relay lens 54, is reflected by a dichroic mirror 55, passes through the hole of the aperture mirror 21, transmits through the dichroic mirror 46, and is projected onto the subject's eye E via the objective lens 22. The return light of the alignment light from the subject's eye E is guided to the image sensor 35 via the same path as the return light of the observation illumination light. Manual alignment or auto alignment can be performed based on the received light image (alignment index image).

[0048] It should be noted that the alignment method applicable to the embodiments is not limited to those using such alignment indicators, and may be any known method, such as a method using an anterior eye camera 300 (described below) or a method using an optical lever configured to project light onto the cornea from an oblique angle and detect corneal reflected light in the opposite direction (described below).

[0049] The focusing optical system 60 generates a split index used for focus adjustment of the subject's eye E. In conjunction with the movement of the photographing focusing lens 31 along the optical path (photographing optical path) of the photographing optical system 30, the focusing optical system 60 is moved along the optical path (illumination optical path) of the illumination optical system 10. The reflecting rod 67 is inserted and removed from the illumination optical path. When performing focus adjustment, the reflecting surface of the reflecting rod 67 is tilted and disposed on the illumination optical path. The focusing light output from the LED 61 passes through the relay lens 62, is split into two light beams by the split index plate 63, passes through the two-hole diaphragm 64, is reflected by the mirror 65, and is once imaged and reflected on the reflecting surface of the reflecting rod 67 by the condenser lens 66. Furthermore, the focusing light passes through the relay lens 20, is reflected by the aperture mirror 21, passes through the dichroic mirror 46, and is projected onto the subject's eye E via the objective lens 22. The return light (fundus reflection light, etc.) of the focusing light from the subject's eye E passes through the same path as the return light of the alignment light and is guided to the image sensor 35. Manual focusing or autofocusing can be performed based on the received light image (split target image).

[0050] Diopter correction lenses 70 and 71 can be selectively inserted into the photographing optical path between the aperture mirror 21 and the dichroic mirror 55. The diopter correction lens 70 is a plus lens (convex lens) for correcting strong hyperopia. The diopter correction lens 71 is a minus lens (concave lens) for correcting strong myopia.

[0051] The dichroic mirror 46 combines the optical path for fundus imaging and the optical path for OCT (measurement arm). The dichroic mirror 46 reflects light in the wavelength band used for OCT and transmits light for fundus imaging. The measurement arm is provided with a collimator lens unit 40, a retroreflector 41, a dispersion compensation member 42, an OCT focusing lens 43, an optical scanner 44, and a relay lens 45 in this order from the OCT unit 100 side.

[0052] The retroreflector 41 is movable along the optical path of the measurement light LS incident thereon, thereby changing the length of the measurement arm. The change in the measurement arm length is used, for example, to correct the optical path length according to the axial length of the eye, adjust the interference state, and so on.

[0053] The dispersion compensation member 42, together with a dispersion compensation member 113 (described later) disposed in the reference arm, acts to match the dispersion characteristics of the measurement light LS with the dispersion characteristics of the reference light LR.

[0054] The OCT focusing lens 43 is moved along the measurement arm to adjust the focus of the measurement arm. The movement of the imaging focusing lens 31, the movement of the focus optical system 60, and the movement of the OCT focusing lens 43 can be controlled in a coordinated manner.

[0055] The optical scanner 44 is disposed substantially at a position optically conjugate with the pupil of the subject's eye E. The optical scanner 44 deflects the measurement light LS guided by the measurement arm. The optical scanner 44 is, for example, a galvano scanner capable of two-dimensional scanning. Typically, the optical scanner 44 includes a one-dimensional scanner (x-scanner) for deflecting the measurement light in ±x directions and a one-dimensional scanner (y-scanner) for deflecting the measurement light in ±y directions. In this case, for example, either one of these one-dimensional scanners is disposed at a position optically conjugate with the pupil, or a position optically conjugate with the pupil is disposed between these one-dimensional scanners.

[0056] <OCT Unit 100> The exemplary OCT unit 100 shown in FIG. 2 is provided with an optical system for performing spectral domain OCT. This optical system includes an interference optical system. This interference optical system splits light from a tunable light source into measurement light and reference light, and generates interference light by superimposing the return light of the measurement light projected onto the subject's eye E and the reference light passing through the reference light path. The spectral distribution of the interference light generated by the interference optical system is detected by a spectroscope. Data (detection signal) obtained by detecting the spectral distribution of the interference light is sent to the arithmetic and control unit 200.

[0057] The light source unit 101 outputs wideband low coherence light L0. The low coherence light L0 includes, for example, a wavelength band in the near infrared region (approximately 800 nm to 900 nm) and has a temporal coherence length of approximately several tens of micrometers. The low coherence light L0 may be near infrared light having a central wavelength of, for example, approximately 1040 to 1060 nm that is not visible to the human eye. The light source unit 101 includes a light output device such as a superluminescent diode (SLD), an LED, or a semiconductor optical amplifier (SOA).

[0058] When swept-source OCT is employed, the light source unit includes a near-infrared tunable laser that changes the wavelength of emitted light at high speed.

[0059] Low-coherence light L0 output from light source unit 101 is guided by optical fiber 102 to polarization controller 103, where its polarization state is adjusted. The light L0 whose polarization state has been adjusted is guided by optical fiber 104 to fiber coupler 105, where it is split into measurement light LS and reference light LR. The optical path that guides the measurement light LS is called a measurement arm, etc., and the optical path that guides the reference light LR is called a reference arm, etc.

[0060] The reference light LR generated by the fiber coupler 105 is guided by the optical fiber 110 to the collimator 111, where it is converted into a parallel beam, and is guided to the retroreflector 114 via the optical path length correction member 112 and the dispersion compensation member 113. The optical path length correction member 112 acts to match the optical path length of the reference light LR with that of the measurement light LS. The dispersion compensation member 113 acts, together with the dispersion compensation member 42 arranged in the measurement arm, to match the dispersion characteristics between the reference light LR and the measurement light LS. The retroreflector 114 is movable along the optical path of the reference light LR incident thereon, thereby changing the length of the reference arm. The change in the reference arm length is used, for example, for correcting the optical path length according to the axial length of the eye, adjusting the interference state, and the like.

[0061] The reference light LR that has passed through the retroreflector 114 passes through the dispersion compensation member 113 and the optical path length correction member 112, is converted from a parallel beam to a focused beam by the collimator 116, and enters an optical fiber 117. The reference light LR that has entered the optical fiber 117 is guided to a polarization controller 118 where its polarization state is adjusted, is guided through an optical fiber 119 to an attenuator 120 where its light amount is adjusted, and is guided through an optical fiber 121 to a fiber coupler 122.

[0062] On the other hand, the measurement light LS generated by the fiber coupler 105 is guided through the optical fiber 127 to the collimator lens unit 40, where it is converted into a parallel beam, passes through the retroreflector 41, the dispersion compensation member 42, the OCT focusing lens 43, the optical scanner 44, and the relay lens 45, is reflected by the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E. The measurement light LS is scattered and reflected at various depth positions in the subject's eye E. The return light of the measurement light LS from the subject's eye E travels in the opposite direction through the measurement arm, is guided to the fiber coupler 105, and reaches the fiber coupler 122 via the optical fiber 128.

[0063] The fiber coupler 122 superimposes the measurement light LS incident via the optical fiber 128 and the reference light LR incident via the optical fiber 121 to generate an interference light LC.

[0064] The interference light LC generated by the fiber coupler 122 is guided to the spectrometer 130 through the optical fiber 129. The spectrometer 130 converts the incident interference light LC into a parallel beam by a collimator lens, resolves the parallel beam of interference light LC into spectral components by a diffraction grating, and projects the spectral components resolved by the diffraction grating onto an image sensor by a lens 114. This image sensor is, for example, a line sensor, and detects a plurality of spectral components of the interference light LC to generate an electrical signal (detection signal). The generated detection signal is sent to the arithmetic and control unit 200.

[0065] In addition, when swept-source OCT is adopted, interference light generated by superimposing measurement light and reference light is branched at a predetermined branching ratio (for example, 1:1) to generate a pair of interference light, and the generated pair of interference light is guided to a photodetector. The photodetector includes, for example, a balanced photodiode. The balanced photodiode includes a pair of photodetectors that detect the pair of interference light, respectively, and outputs the difference between the pair of detection signals obtained by these. The photodetector sends this output (detection signal such as a difference signal) to a data acquisition system (DAQ). A clock is supplied to the data acquisition system from the light source unit. The clock is generated in the light source unit in synchronization with the output timing of each wavelength swept within a predetermined wavelength range by the wavelength-tunable light source. For example, the light source unit branches light of each output wavelength to generate two branched lights, optically delays one of the branched lights, combines the branched lights, detects the obtained combined light, and generates a clock based on the detection signal. The data acquisition system performs sampling of the detection signal (differential signal) input from the photodetector based on the clock. The data obtained by this sampling is used for processing such as image construction.

[0066] 1 and 2 is provided with both an element for changing the measurement arm length (e.g., retroreflector 41) and an element for changing the reference arm length (e.g., retroreflector 114 or reference mirror), but only one of these elements may be provided. The coherence gate position is changed by changing the difference (optical path length difference) between the measurement arm length and the reference arm length, but the element for changing the optical path length difference is not limited to the element exemplified in this embodiment, and any element (optical member, mechanism, etc.) can be adopted.

[0067] <Arithmetic control unit 200> The arithmetic control unit 200 controls each part of the ophthalmologic apparatus 1. The arithmetic control unit 200 also executes various arithmetic processing. For example, the arithmetic control unit 200 forms a reflection intensity profile for each A-line by performing signal processing such as Fourier transform on the spectral distribution acquired by the spectroscope 130. Furthermore, the arithmetic control unit 200 forms image data by imaging the reflection intensity profile of each A-line. The arithmetic processing for this purpose is similar to that of conventional spectral domain OCT.

[0068] The arithmetic control unit 200 includes, for example, a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), a hard disk drive, a communication interface, etc. Various computer programs are stored in a storage device such as a hard disk drive. The arithmetic control unit 200 may also include an operation device, an input device, a display device, etc.

[0069] <User Interface 240> The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes the display device 3. The operation unit 242 includes various operation devices and input devices. The user interface 240 may include a device such as a touch panel in which a display function and an operation function are integrated. It is also possible to construct an embodiment that does not include at least a part of the user interface 240. For example, the display device may be an external device connected to the ophthalmic imaging apparatus.

[0070] <Anterior Eye Camera 300> The anterior eye camera 300 photographs the anterior eye of the subject's eye E from two or more different directions. The anterior eye camera 300 includes an imaging element such as a CCD image sensor or a CMOS image sensor. In this embodiment, two anterior eye cameras 300 are provided on the subject side of the fundus camera unit 2 (see the anterior eye cameras 300A and 300B shown in FIG. 4A). As shown in FIG. 1 and FIG. 4A, the anterior eye cameras 300A and 300B are provided at positions off the optical path passing through the objective lens 22. Hereinafter, one of the anterior eye cameras 300A and 300B or both of them may be collectively indicated by the symbol 300. In addition, an anterior eye camera that can be adopted instead of the anterior eye cameras 300A and 300B may be indicated by the symbol 300.

[0071] In this embodiment, two anterior eye cameras 300A and 300B are provided, but the number of anterior eye cameras 300 may be any number equal to or greater than two. Considering the calculation process described below, a configuration capable of photographing the anterior eye from two different directions is sufficient (but is not limited to this). Alternatively, a movable anterior eye camera 300 may be provided to sequentially photograph the anterior eye from two or more different positions.

[0072] In this embodiment, the anterior eye camera 300 is provided separately from the illumination optical system 10 and the photographing optical system 30, but for example, the anterior eye can be photographed using the photographing optical system 30. That is, one of the two or more anterior eye cameras 300 may be the photographing optical system 30. The anterior eye camera 300 according to this embodiment may be capable of photographing the anterior eye from two (or more) different directions.

[0073] A configuration for illuminating the anterior eye may be provided. The anterior eye illumination means includes, for example, one or more light sources. Typically, at least one light source (e.g., an infrared light source) can be provided near each of the two or more anterior eye cameras 300.

[0074] When two or more anterior eye cameras 300 are provided, the anterior eye can be photographed substantially simultaneously from two or more different directions. "Substantially simultaneously" refers to the case where the photographing timings of the two or more anterior eye cameras are simultaneous, and also the case where there is a difference in the photographing timing to such an extent that eye movement can be ignored. Such substantially simultaneous photographing makes it possible to obtain images of the subject's eye E in substantially the same position and orientation by the two or more anterior eye cameras.

[0075] The two or more anterior eye cameras may capture video or still images. In the case of video capture, the above-mentioned substantially simultaneous anterior eye images can be realized by controlling the timing of the start of capture to be synchronized, or by controlling the frame rate and the capture timing of each frame. On the other hand, in the case of still image capture, the substantially simultaneous anterior eye images can be realized by controlling the timing of capture to be synchronized.

[0076] <Control System> 3A and 3B show an example of the configuration of a control system (processing system) of the ophthalmologic apparatus 1. The control unit 210, the image forming unit 220, and the data processing unit 230 are provided in an arithmetic control unit 200, for example.

[0077] <Control unit 210> The control unit 210 includes a processor, and controls each unit of the ophthalmologic apparatus 1. The control unit 210 includes a main control unit 211 and a storage unit 212.

[0078] <Main control unit 211> The main control unit 211 includes a processor, and controls each element (including the elements shown in FIGS. 1 to 3B) of the ophthalmic apparatus 1. The main control unit 211 is realized by cooperation between hardware including circuits and control software.

[0079] The photographing focusing lens 31 arranged in the photographing optical path and the focus optical system 60 arranged in the illumination optical path are moved integrally or in cooperation with each other by a photographing focusing drive unit (not shown) under the control of the main control unit 211. The retroreflector 41 arranged in the measurement arm is moved by a retroreflector (RR) drive unit 41A under the control of the main control unit 211. The OCT focusing lens 43 arranged in the measurement arm is moved by an OCT focusing drive unit 43A under the control of the main control unit 211. The movement of the OCT focusing lens 43 can be performed in cooperation with the movement of the photographing focusing lens 31 and the focus optical system 60. The retroreflector 114 arranged in the reference arm is moved by a retroreflector (RR) drive unit 114A under the control of the main control unit 211. Each of the mechanisms exemplified here typically includes an actuator such as a pulse motor that operates under the control of the main control unit 211. The optical scanner 44 arranged in the measurement arm operates under the control of the main control unit 211. Furthermore, the main control unit 211 can control any element included in the ophthalmic apparatus 1, such as the polarization controller 103, the polarization controller 118, the attenuator 120, various light sources, various optical elements, various devices, and various mechanisms. The main control unit 211 may also be capable of controlling any peripheral equipment (apparatus, equipment, device, etc.) connected to the ophthalmic apparatus 1, and any equipment, equipment, device, etc. accessible by the ophthalmic apparatus 1.

[0080] The moving mechanism 150, for example, moves at least the fundus camera unit 2 three-dimensionally. In a typical example, the moving mechanism 150 includes an x-stage movable in ±x directions (left and right directions), an x-moving mechanism for moving the x-stage, a y-stage movable in ±y directions (up and down directions), a y-moving mechanism for moving the y-stage, a z-stage movable in ±z directions (depth direction), and a z-moving mechanism for moving the z-stage. Each of these moving mechanisms includes an actuator such as a pulse motor that operates under the control of the main controller 211.

[0081] <Storage section 212> The storage unit 212 stores various types of data. Examples of data stored in the storage unit 212 include image data of an OCT image, image data of a fundus image, and information about the subject's eye. The information about the subject's eye includes information about the subject, such as a patient ID and name, identification information for the left eye / right eye, and electronic medical record information.

[0082] <Image forming unit 220> The image forming unit 220 forms OCT image data based on the data acquired by the spectrometer 130. The image forming unit 220 includes a processor. The image forming unit 220 is realized by cooperation between hardware including a circuit and image forming software.

[0083] The image forming unit 220 forms cross-sectional image data based on the data acquired by the spectroscope 130. This image forming process includes signal processing such as sampling (A / D conversion), noise removal (noise reduction), filtering, and fast Fourier transform (FFT), similar to conventional spectral domain OCT.

[0084] The image data formed by the image forming unit 220 is a data set including a group of image data (a group of A-scan image data) formed by imaging the reflection intensity profiles in multiple A-lines (scan lines along the z-direction) arranged in the area where the OCT scan was applied.

[0085] The image data formed by the image forming unit 220 is, for example, one or more B-scan image data, or stack data formed by embedding a plurality of B-scan image data in a single three-dimensional coordinate system. The image forming unit 220 can also perform a voxelization process on the stack data to construct volume data (voxel data). The stack data and volume data are typical examples of three-dimensional image data expressed in a three-dimensional coordinate system.

[0086] The image forming unit 220 can process the three-dimensional image data. For example, the image forming unit 220 can apply rendering to the three-dimensional image data to construct new image data. Rendering methods include volume rendering, maximum intensity projection (MIP), minimum intensity projection (MIP), surface rendering, and multiplanar reconstruction (MPR). The image forming unit 220 can also construct projection data by projecting the three-dimensional image data in the z direction (A-line direction, depth direction). The image forming unit 220 can also construct a shadowgram by projecting a part of the three-dimensional image data (three-dimensional partial image data) in the z direction. The three-dimensional partial image data is set, for example, by applying segmentation to the three-dimensional image data.

[0087] Data Processing Unit 230 The data processing unit 230 executes various types of data processing. For example, the data processing unit 230 can apply image processing and analysis processing to OCT image data, and can apply image processing and analysis processing to observed image data or captured image data. The data processing unit 230 includes, for example, at least one of a processor and a dedicated circuit board. The data processing unit 230 is realized by cooperation between hardware including a circuit and data processing software.

[0088] Next, a functional configuration of the ophthalmic device 1 realized by the elements (hardware elements, software elements) shown in Figures 1 to 3A will be described. An example of the functional configuration of the ophthalmic device 1 is shown in Figure 3B. Among the elements shown in Figure 3B, the same elements as those in Figure 3A are denoted by the same reference numerals.

[0089] <Scanning unit 410> The scanning unit 410 acquires data by applying an OCT scan to the subject's eye E. The data acquired by the scanning unit 410 may be, for example, any one of first data acquired by the spectroscope 130, second data (sampling data, reflection intensity profile, image data, etc.) generated by the image forming unit 220 from the first data, and data (image data, etc.) generated by the data processing unit 230 or the like from the second data. In this manner, the scanning unit 410 includes at least the spectroscope 130, may further include at least a part of the image forming unit 220, and may further include at least a part of the data processing unit 230.

[0090] The scan unit 410 includes an interference optical system including the above-mentioned measurement arm that guides the measurement light LS to the subject's eye E and the above-mentioned reference arm that guides the reference light LS. As described above, the measurement arm is provided with the OCT focusing lens 43, the optical scanner 44, etc., and the reference arm is provided with the polarization controller 118, the attenuator 120, etc. This interference optical system includes a spectrometer 130.

[0091] Furthermore, the scan unit 410 includes an arm length changer provided in at least one of the measurement arm and the reference arm. The arm length changer includes one or both of a combination of the retroreflector 41 and the retroreflector driver 41A and a combination of the retroreflector 114 and the retroreflector driver 114A. The arm length changer changes the arm length under the control of the scan control unit 450 described below. More specifically, when the arm length changer includes a combination of the retroreflector 41 and the retroreflector driver 41A, the arm length changer can change the measurement arm length. Also, when the arm length changer includes a combination of the retroreflector 114 and the retroreflector driver 114A, the arm length changer can change the reference arm length.

[0092] <Displacement measuring unit 420> The deviation measuring unit 420 measures the deviation of the subject's eye E relative to a preset reference position. The alignment control unit 440 described later executes alignment control based on the deviation measurement result (deviation information) acquired by the deviation measuring unit 420. The alignment control includes control of the moving mechanism 150 based on the deviation information. For example, the alignment control is a process of moving the optical system (at least the measurement arm) so as to cancel the deviation acquired by the deviation measuring unit 420.

[0093] The deviation of the subject's eye E with respect to the reference position is a relative position with respect to the reference position, and is typically a vector quantity (direction and magnitude).

[0094] The reference position is set based on, for example, the optical system of the ophthalmologic apparatus 1. Typical reference positions include a reference position in the x direction, a reference position in the y direction, and a reference position in the z direction. That is, a typical reference position is a three-dimensional position. The reference position is not limited to a three-dimensional position, and may be a two-dimensional position or a one-dimensional position.

[0095] As described above, since the deviation of the subject's eye E with respect to the reference position is a relative position, when the reference position is set based on the optical system of the ophthalmic apparatus 1, the deviation of the subject's eye E with respect to the optical system of the ophthalmic apparatus 1 is synonymous with the deviation of the subject's eye E with respect to the optical system. Note that even when the reference position is set not based on the optical system of the ophthalmic apparatus 1, the deviation of the subject's eye E with respect to the optical system of the ophthalmic apparatus 1 is synonymous with the deviation of the subject's eye E with respect to the optical system with respect to the reference position.

[0096] The reference position in the x direction and the reference position in the y direction (xy reference position) are, for example, the position (optical axis position) of the optical axis (optical axis of the objective lens 22) of the ophthalmic apparatus 1. In this case, the deviation measuring unit 420 can obtain the deviation of the subject's eye E with respect to the optical axis position on the xy plane (xy coordinate system).

[0097] On the other hand, the reference position in the z direction (z reference position) is, for example, a position spaced a predetermined distance in the +z direction from the optical system (the front surface of the objective lens 22) of the ophthalmic apparatus 1. In this case, the deviation measuring unit 420 can obtain the deviation of the subject's eye E with respect to the z reference position in the z direction (z coordinate).

[0098] The predetermined distance used to define the z reference position is, for example, a preset working distance, or a distance obtained by adding a predetermined value to the working distance. Examples of the predetermined value include half the value of the corneal curvature radius and the value of the distance between the cornea and the pupil.

[0099] When alignment is performed based on the corneal surface, the working distance can be used as the above-mentioned predetermined distance. When alignment is performed based on a bright spot (Purkinje image) formed in the anterior segment, the distance obtained by adding half the value of the corneal curvature radius to the working distance can be used as the above-mentioned predetermined distance. When alignment is performed based on the pupil, the distance obtained by adding the value of the corneal interpupillary distance to the working distance can be used as the above-mentioned predetermined distance. The corneal curvature radius and the corneal interpupillary distance may be values ​​obtained by actually measuring the eye E to be examined.

[0100] An example of the three-dimensional reference position is a position on the optical axis of the ophthalmic apparatus 1 that is spaced from the front surface of the objective lens 22 in the +z direction by the above-mentioned predetermined distance.

[0101] In order to obtain the deviation of the test eye E from the reference position, it is necessary to define the position of the test eye E. The position of the test eye E is defined as, for example, the position of a bright spot formed in the anterior segment, the position of the pupil center (pupil gravity center), or the position of the corneal apex.

[0102] When the position of the test eye E is defined as a bright spot position, the deviation measurement unit 420 can identify the bright spot position from two anterior eye images acquired by two anterior eye cameras 300, for example, according to the processing method disclosed in Japanese Patent Application Publication No. 2017-074115 and Japanese Patent Application Publication No. 2017-225638 by the present applicant, and determine the deviation of the test eye E relative to a reference position.

[0103] When the position of the test eye E is defined as the pupil center position, the deviation measurement unit 420 can identify the pupil center position from two anterior eye images acquired by two anterior eye cameras 300, for example, according to the processing method disclosed in Japanese Patent Application Publication No. 2013-248376 and Japanese Patent Application Publication No. 2017-225638 by the present applicant, and determine the deviation of the test eye E relative to a reference position.

[0104] When the position of the test eye E is defined as the corneal apex position, the deviation measurement unit 420 can identify the corneal apex position from two anterior segment images acquired by two anterior segment cameras 300, for example, according to the processing method disclosed in JP 2017-225638 by the present applicant, and determine the deviation of the test eye E relative to a reference position.

[0105] The definition of the reference position, the definition of the position of the subject's eye E, the processing method for identifying the position of the subject's eye E, and the calculation method for the deviation of the subject's eye E from the reference position are not limited to the above examples and may be any. For example, an alignment method based on the positional relationship between two bright points or an alignment method using an optical lever can be applied.

[0106] 3B is an example applicable to the case where the position of the subject's eye E is defined as a bright spot position. The deviation measuring part 420 of this example includes an alignment optical system 50, two anterior eye cameras 300, and a deviation calculating part 430. The deviation calculating part 430 is included in the data processing part 230, and is realized by cooperation between hardware including a circuit and deviation calculating software.

[0107] As described above, the alignment optical system 50 projects an alignment target onto the anterior segment of the subject's eye E. That is, the alignment optical system 50 corresponds to a projection system that projects a light beam onto the anterior segment of the subject's eye E.

[0108] When the light beam is projected by the alignment optical system 50, the two anterior eye cameras 300 capture the anterior eye of the subject's eye E from different directions. This results in two anterior eye images corresponding to different directions. Each of these anterior eye images depicts an image of the light beam projected by the alignment optical system 50, i.e., a bright point used as an alignment indicator.

[0109] The deviation calculation section 430 calculates the deviation of the subject's eye E with respect to a predetermined reference position based on the positions of two bright points depicted in the two anterior eye images acquired by the two anterior eye cameras 300, respectively.

[0110] Similar to the processing methods disclosed in JP 2017-074115 A and JP 2017-225638 A, the deviation calculation unit 430 analyzes each of the two anterior eye images to detect bright spots, and identifies the position of the test eye E based on the two bright spots detected from the two anterior eye images.

[0111] For example, the deviation calculation unit 430 can calculate the distance between the subject's eye E and the ophthalmic apparatus 1 (objective lens 22) in the direction along the optical axis (z direction) of the ophthalmic apparatus 1 based on the relative positions of two bright spots detected from two anterior eye images. Based on this distance, the alignment control unit 440 can control the movement mechanism 150 so that the distance between the subject's eye E and the ophthalmic apparatus 1 in the z direction matches the working distance.

[0112] Furthermore, the deviation calculation unit 430 can calculate the deviation between the subject's eye E and the ophthalmic apparatus 1 in directions perpendicular to the z direction (x direction, y direction) based on the positions of the two bright spots detected from the two anterior eye images. Based on this deviation, the alignment control unit 440 can control the moving mechanism 150 so as to align the optical axis of the ophthalmic apparatus 1 with the axis of the subject's eye E.

[0113] When no bright spot is detected from either or both of the two anterior eye images, the alignment method may be switched to another method (for example, alignment based on the center of the pupil).

[0114] Although details will be described later, the ophthalmologic apparatus 1 executes a first OCT scan on a first region (e.g., an anterior eye region) including a first portion (e.g., a corneal surface) of the subject's eye E, and a second OCT scan on a second region (e.g., a posterior eye region) including a second portion (e.g., a retinal surface). The deviation measurement unit 420 performs a first deviation measurement to obtain first deviation information before the first OCT scan, and performs a second deviation measurement to obtain second deviation information before the second OCT scan. Typically, the first deviation measurement is performed immediately before the first OCT scan, and the second deviation measurement is performed immediately before the second OCT scan.

[0115] The order of execution of the first OCT scan and the second OCT scan is arbitrary; the second OCT scan may be executed after the first OCT scan, or the first OCT scan may be executed after the second OCT scan.

[0116] <Alignment control unit 440> The alignment control unit 440 executes a first alignment control for controlling the moving mechanism 150 based on first deviation information acquired by the deviation measurement unit 420 before the first OCT scan, and a second alignment control for controlling the moving mechanism 150 based on second deviation information acquired by the deviation measurement unit 420 before the second OCT scan.

[0117] For example, the alignment control unit 440 performs first alignment control so as to cancel out the deviation indicated by the first deviation information, and also performs second alignment control so as to cancel out the deviation indicated by the second deviation information, in the same manner as the alignment methods disclosed in JP 2017-074115 A, JP 2017-225638 A, or JP 2013-248376 A.

[0118] The alignment control unit 440 is included in the control unit 210 and is realized by cooperation between hardware including circuits and alignment control software.

[0119] <Scan control unit 450> The scan control unit 450 executes control for the first OCT scan and the second OCT scan described above. That is, the scan control unit 450 executes a first scan control for making the scan unit 410 execute a first OCT scan on a first region (e.g., an anterior eye region) including a first site (e.g., a corneal surface) of the subject's eye E, and a second scan control for making the scan unit 410 execute a second OCT scan on a second region (e.g., a posterior eye region) including a second site (e.g., a retinal surface).

[0120] Each of the first scan control and the second scan control includes, for example, control of an arm length changer (either one or both of the retroreflector driving unit 41A and the retroreflector driving unit 114A), control of the light source unit 101, and control of the optical scanner 44. Each of the first scan control and the second scan control may include control of the polarization controller 103, control of the polarization controller 118, control of the attenuator 120, control of the OCT focusing driving unit 43A, etc. Examples of the first scan control and the second scan control will be described later.

[0121] The scan control unit 450 is included in the control unit 210 and is realized by cooperation between hardware including circuits and scan control software.

[0122] <Distance Calculation Unit 460> The distance calculation unit 460 calculates the distance between a first portion included in the application range of the first OCT scan and a second portion included in the application range of the second OCT scan, based on the first data acquired by the first OCT scan and the second data acquired by the second OCT scan. That is, the distance calculation unit 460 calculates the distance between the first portion and the second portion of the subject's eye E, based on the first data acquired by the scan unit 410 under the first scan control and the second data acquired by the scan unit 410 under the second scan control.

[0123] For example, when the first site is the corneal surface and the second site is the retinal surface, that is, when the first OCT scan is applied to the anterior eye region including the corneal surface and the second OCT scan is applied to the posterior eye region including the retinal surface, the distance calculation unit 460 can calculate the distance between the corneal surface and the retinal surface. Typically, the distance calculation unit 460 can calculate the axial length, which is the distance between the corneal apex and the center of the macular (fovea).

[0124] For example, distance calculation unit 460 performs distance calculation through a series of processes (first to fourth processes) shown below. Here, the first to third processes may be performed in any order, and any two or more of these processes may be performed in parallel.

[0125] In the first process, the distance calculation unit 460 calculates the difference between the first arm length applied in the first scan control and the second arm length applied in the second scan control. The first arm length and the second arm length are acquired, for example, from the scan control unit 450 that executed the first scan control and the second scan control. Alternatively, either or both of the first arm length and the second arm length may be detected by a means for detecting the arm length, for example, a position sensor that detects the position of either or both of the retroreflector 41 and the retroreflector 114.

[0126] In the second process, the distance calculation unit 460 analyzes the first data acquired by the scan unit 410 under the first scan control to identify a position (first position) in the first data corresponding to a first portion of the subject's eye E. For example, when the first portion is the corneal surface, the distance calculation unit 460 analyzes the first data acquired by the first OCT scan of the anterior eye region to identify the first position corresponding to the corneal surface (typically the corneal apex) of the subject's eye E. Typically, the first position is a signal position in a reflection intensity profile generated from a detection signal acquired by the first OCT scan, or a pixel position in A-scan image data obtained by imaging this reflection intensity profile.

[0127] In the third process, the distance calculation unit 460 analyzes the second data acquired by the scan unit 410 under the second scan control to identify a position (second position) in the second data corresponding to the second site of the subject's eye E. For example, when the second site is the retinal surface, the distance calculation unit 460 analyzes the second data acquired by the second OCT scan of the posterior eye region to identify the second position corresponding to the retinal surface (typically the center of the macula) of the subject's eye E. Typically, the second position is a signal position in a reflection intensity profile generated from a detection signal acquired by the second OCT scan, or a pixel position in A-scan image data obtained by imaging this reflection intensity profile.

[0128] In the fourth process, the distance calculation unit 460 calculates the distance between the first portion and the second portion based on the arm length difference calculated in the first process, the first position identified in the second process, and the second position identified in the third process.

[0129] Typically, in the fourth process, the distance calculation unit 460 calculates the value of the axial length of the subject's eye E based on the arm length difference calculated in the first process, the corneal apex position identified in the second process, and the macular center position identified in the third process. An overview of this calculation process is shown in FIG.

[0130] The corneal apex of the test eye E is indicated by the symbol C, and the macular center is indicated by the symbol M. Symbols A1 and A2 indicate the first OCT scan and the second OCT scan, respectively. In this example, the first OCT scan A1 and the second OCT scan A2 are A-scans. FIG. 5 shows a case where the first OCT scan A1 and the second OCT scan A2 are each performed under a good alignment state. That is, FIG. 5 shows a case where the first OCT scan A1 is performed so as to pass through the corneal apex C, and the second OCT scan A2 is performed so as to pass through the macular center M.

[0131] The reflection intensity profile acquired by the first OCT scan A1 is denoted by the symbol P1, and the reflection intensity profile acquired by the second OCT scan A2 is denoted by the symbol P2. The z-coordinate axis on which the first reflection intensity profile P1 is defined is denoted by "z1", and the z-coordinate axis on which the second reflection intensity profile P2 is defined is denoted by "z2".

[0132] The first OCT scan A1 of the anterior eye region is performed with a coherence gate placed at an arbitrary position in the anterior eye. For example, the coherence gate is placed at a position (bright spot formation position) that is half the distance of the corneal curvature radius from the corneal apex C in the +z direction. The symbol z1(0) indicates the coherence gate position applied in the first OCT scan A1 of this example.

[0133] On the other hand, the second OCT scan A2 of the posterior segment is performed with a coherence gate placed at an arbitrary position in the posterior segment. For example, the coherence gate is placed in the vitreous body close to the retinal surface. The symbol z2(0) indicates the coherence gate position applied in the second OCT scan A2 in this example.

[0134] The distance calculation unit 460 calculates the difference between the coherence gate position z1(0) applied in the first OCT scan A1 and the coherence gate position z2(0) applied in the second OCT scan A2. This difference is indicated by the symbol Δz 12and corresponds to the arm length difference between the first OCT scan A1 and the second OCT scan A2. This process is an example of the first process described above.

[0135] The first reflection intensity profile P1 includes a peak corresponding to the corneal surface, a peak corresponding to the back surface of the cornea, a peak corresponding to the surface of the crystalline lens, and a peak corresponding to the back surface of the crystalline lens. The distance calculation unit 460 identifies the peak corresponding to the corneal surface from among the multiple peaks included in the first reflection intensity profile P1. This peak identification includes, for example, a process of identifying the peak with the maximum intensity. Alternatively, this peak identification may include a process of identifying the peak with the smallest z1 coordinate value (the peak located closest to the -z1 side) among the peaks with intensity exceeding a predetermined threshold. The z1 coordinate value of the peak corresponding to the corneal surface identified in this manner is referred to as "z C In this example, the z1 coordinate value z C corresponds to the position of the corneal apex C. z1 coordinate value z C The process for determining is an example of the second process described above.

[0136] The second reflection intensity profile P2 includes a peak corresponding to the retinal surface, as well as multiple peaks corresponding to the inner retinal layers and a peak corresponding to the choroid. The distance calculation unit 460 identifies the peak corresponding to the retinal surface from the multiple peaks included in the second reflection intensity profile P2. This peak identification includes, for example, a process of identifying the peak with the maximum intensity. Alternatively, this peak identification may include a process of identifying the peak with the smallest z2 coordinate value (the peak located closest to the -z2 side) among the peaks with intensity exceeding a predetermined threshold. The z2 coordinate value of the peak corresponding to the retinal surface identified in this manner is referred to as "z M In this example, the z2 coordinate value z M corresponds to the position of the macula center M. The z2 coordinate value z M The process for determining is an example of the third process described above.

[0137] The distance calculation unit 460 calculates the arm length difference Δz 12 and the corneal apex position z Cand the pupil center position z M Based on this, the distance between the corneal apex C and the center of the macula M (axial length) is calculated. In the example shown in FIG. 5, the axial length AL is calculated using the following formula: AL=Δz 12 +(z1(0)-z C )+(z M -z2(0)). The sign on the right side is determined by the settings of the coherence gate position, the first region, the second region, etc., and the axial length AL is generally calculated using the following formula: AL = Δz 12 ±|z C -z1(0)|±|z M −z2(0)|. This process for determining a distance such as the axial length is an example of the fourth process.

[0138] <Operation> An example of the operation of the ophthalmic apparatus 1 according to this embodiment will be described below. An example of the operation of the ophthalmic apparatus 1 is shown in Fig. 6. In this operation example, for example, a fixation target for photographing the macula is presented to the subject's eye E.

[0139] (S1: Perform alignment) First, alignment of the ophthalmic apparatus 1 with respect to the examinee's eye E is performed.

[0140] In this example, first, the alignment control unit 440 turns on the light emitting diode 51 of the alignment optical system 50. As a result, a light beam is projected onto the anterior segment of the subject's eye E, forming a bright spot on the anterior segment. The two anterior segment cameras 300 capture the anterior segment onto which the light beam is projected from different directions. As a result, a pair of anterior segment images, each depicting a bright spot, is obtained.

[0141] The deviation calculation part 430 identifies the bright spot position from each of the pair of anterior eye images, and obtains the deviation of the subject's eye E with respect to a predetermined reference position. The alignment control part 440 controls the moving mechanism 150 so as to cancel the deviation calculated by the deviation calculation part 430.

[0142] In this example, a series of processes including anterior eye photography by the two anterior eye cameras 300, deviation calculation by the deviation calculation unit 430, and movement control by the alignment control unit 440 are repeatedly executed at a predetermined time interval, so that the alignment state can be gradually improved and a good alignment state can be maintained. The latter is called tracking.

[0143] (S2: Change the arm length to obtain the corneal signal) When a good alignment state is achieved by step S1, the scan control unit 450 (and the data processing unit 230) changes either or both of the measurement arm length and the reference arm length so as to obtain a signal corresponding to the cornea of ​​the subject's eye E. The measurement arm length is changed by controlling the retroreflector driving unit 41A, and the reference arm length is changed by controlling the retroreflector driving unit 114A.

[0144] In addition, taking into consideration that the position of the cornea is determined by the working distance, the retroreflector driving unit (either or both of the retroreflector driving unit 41A and the retroreflector driving unit 114A) may be controlled by a predetermined control amount so that the retroreflector (either or both of the retroreflector 41 and the retroreflector 114) is positioned at a position corresponding to an arm length (either or both of the measurement arm length and the reference arm length) at which a signal from the position of the cornea determined by a predetermined working distance can be detected.

[0145] The processing of step S2 includes, for example, a process called "Auto Z" disclosed in JP 2017-184874 A by the present applicant. Auto Z is an automatic process that searches for a good arm length (here, an arm length that can obtain a corneal signal). Note that the arm length adjustment of step S2 may be performed by a process different from Auto Z. In addition to Auto Z, it is also possible to execute a process called "Z lock" disclosed in the same document. Z lock is an automatic process for maintaining a good image depiction state achieved by Auto Z.

[0146] After the arm length adjustment in step S2, alignment may be performed again in the same manner as in step S1.

[0147] Here, the OCT focusing lens 43 may be moved to focus on the vicinity of the cornea. For example, since the position of the cornea is determined by the working distance as described above, the position of the OCT focusing lens 43 corresponding to this is determined in advance, and the OCT focusing lens 43 can be moved to this position. Also, considering that the signal intensity from the anterior surface of the cornea is strong, it is also possible to move the OCT focusing lens 43 so as to focus on the retina even when the signal from the cornea is acquired. In this case, the OCT focusing lens 43 may be moved in conjunction with the movement of the focusing optical system 60, or the OCT focusing lens 43 may be moved by the amount of movement determined using the focusing optical system 60.

[0148] (S3: OCT scan applied to the anterior segment) When the arm length adjustment in step S2 is completed, the scan control unit 450 executes control for applying an OCT scan to the anterior segment of the subject's eye E. In this example, the scan control unit 450 executes a first scan control for causing the scan unit 410 to execute an OCT scan of the anterior segment region including the corneal surface of the subject's eye E.

[0149] The OCT scan applied here is, for example, an A-scan, and cases where other scan modes are applied will be described later.

[0150] (S4: Generate a reflection intensity profile) The scanning unit 410 (image forming unit 220) generates a reflection intensity profile from the data acquired by the OCT scan in step S3. This reflection intensity profile is data corresponding to the A-line to which the A-scan was applied in step S3.

[0151] (S5: Record the retroreflector position and reflection intensity profile) The ophthalmic apparatus 1 (eg, the distance calculation unit 460) records the position of the retroreflector when the OCT scan in step S3 is performed and the reflection intensity profile generated in step S4.

[0152] When the measurement arm length is changed in step S2, the position of the retroreflector 41 is recorded, and when the reference arm length is changed in step S2, the position of the retroreflector 114 is recorded. Here, the position of the retroreflector 41 is obtained, for example, based on the control contents for the retroreflector driving unit 41A, or by detecting the position of the retroreflector 41. Similarly, the position of the retroreflector 114 is obtained, for example, based on the control contents for the retroreflector driving unit 114A, or by detecting the position of the retroreflector 114.

[0153] (S6: Change the arm length to obtain retinal signals) Next, the scan control unit 450 (and the data processing unit 230) changes either or both of the measurement arm length and the reference arm length so as to obtain a signal corresponding to the retina of the subject's eye E. This process is executed in the same manner as in step S2.

[0154] (S7: Perform alignment) When the arm length adjustment in step S6 is completed, the ophthalmic apparatus 1 is aligned with the subject's eye E. The alignment is performed in the same manner as in step S1.

[0155] If the OCT focusing lens 43 is moved to focus on the vicinity of the cornea when acquiring a signal from the cornea (as described above), then at this stage, the OCT focusing lens 43 can be moved to focus on the retina. At this time, the OCT focusing lens 43 may be moved in conjunction with the movement of the focusing optical system 60, or the OCT focusing lens 43 may be moved by an amount determined using the focusing optical system 60.

[0156] (S8: OCT scan applied to the posterior segment) When the alignment in step S7 is completed, the scan control unit 450 executes control for applying an OCT scan to the posterior segment of the subject's eye E. In this example, the scan control unit 450 executes a second scan control for causing the scan unit 410 to execute an OCT scan of the posterior segment region including the retinal surface of the subject's eye E.

[0157] The OCT scan applied here is, for example, an A-scan, and cases where other scan modes are applied will be described later.

[0158] (S9: Generate reflection intensity profile) The scanning unit 410 (image forming unit 220) generates a reflection intensity profile from the data acquired by the OCT scan in step S8. This reflection intensity profile is data corresponding to the A-line to which the A-scan was applied in step S8.

[0159] (S10: Record the retroreflector position and reflection intensity profile) The ophthalmic apparatus 1 (for example, the distance calculation unit 460) records the position of the retroreflector when the OCT scan in step S8 is performed and the reflection intensity profile generated in step S9. This process is performed in the same manner as step S5.

[0160] (S11: Calculate axial length) The distance calculation section 460 calculates the distance between the corneal surface and the retinal surface based on the position and reflection intensity profile of the retroreflector recorded in step S5 and the position and reflection intensity profile of the retroreflector recorded in step S10.

[0161] In this example, the distance calculation unit 460 first calculates the difference between the first arm length and the second arm length based on the position of the retroreflector recorded in step 5 (i.e., the first arm length applied to the anterior OCT scan) and the position of the retroreflector recorded in step 10 (i.e., the second arm length applied to the posterior OCT scan). Furthermore, the distance calculation unit 460 analyzes the reflection intensity profile recorded in step 5 to identify a position (first position) corresponding to the corneal surface, and analyzes the reflection intensity profile recorded in step S10 to identify a position (second position) corresponding to the retinal surface. Then, the distance calculation unit 460 calculates the axial length of the subject's eye E based on the difference in the arm lengths, the first position, and the second position. This concludes the operation of this operation example (end).

[0162] <Modification of the first embodiment> Modifications applicable to the ophthalmic apparatus 1 according to the first embodiment will be described below. Unless otherwise specified, the reference characters used in the description of the ophthalmic apparatus 1 will be used in the following description.

[0163] First Modified Example For example, if the patient's eye has floaters, the opacities moving within the vitreous may adversely affect the posterior segment OCT scan.

[0164] To address this issue, multiple OCT scans can be applied to the posterior segment, with the scan unit 410 performing the repetitive OCT scans under the control of the scan controller 450. Each OCT scan is typically an A-scan, but is not limited to this and may be any scan mode, such as a B-scan, a 3D scan, etc.

[0165] An example of an applicable repetitive OCT scan (multiple OCT scans) will be described. The ophthalmic apparatus of this example first performs an A scan. If the distance measurement cannot be performed appropriately even after the A scan is repeated a predetermined number of times (for example, 10 times), the ophthalmic apparatus of this example switches the scan mode from the A scan to another scan mode. The other scan mode is, for example, a B scan. The determination of whether the distance measurement has been performed appropriately includes, for example, a step of comparing the intensity of the interference signal obtained by the OCT scan (the A scan at this stage) with a predetermined threshold. If the interference signal intensity is equal to or greater than the threshold, it is determined that the distance measurement has been performed appropriately, and if the interference signal intensity is less than the threshold, it is determined that the distance measurement has not been performed appropriately. The length of the scan line of the B scan of this example is arbitrary, and is typically shorter than that of a normal B scan (for example, 1 mm long). If the distance measurement cannot be performed appropriately even after the B scan is repeated a predetermined number of times (for example, 10 times), the ophthalmic apparatus of this example switches the scan mode from the B scan to another scan mode. The other scan pattern is, for example, a radial scan. Whether or not the distance measurement using the B scan has been performed properly is judged in the same manner as in the case of the A scan. The size of the radial scan in this example is arbitrary, and is typically smaller than that of a normal radial scan (for example, the length of each scan line is 1 mm). By switching the scan mode in this way, a signal corresponding to the retina can be obtained at any stage.

[0166] More generally, the ophthalmic apparatus of this example first applies the first scan mode. The ophthalmic apparatus of this example determines whether or not data obtained by the OCT scan in the first scan mode satisfies a predetermined condition. If the condition is not satisfied even after the OCT scan in the first scan mode is repeated a predetermined number of times, the ophthalmic apparatus of this example switches from the first scan mode to the second scan mode. The ophthalmic apparatus of this example determines whether or not data obtained by the OCT scan in the second scan mode satisfies a predetermined condition. If the condition is not satisfied even after the OCT scan in the second scan mode is repeated a predetermined number of times, the ophthalmic apparatus of this example switches from the second scan mode to the third scan mode. In this way, the ophthalmic apparatus of this example determines whether or not suitable data has been obtained by the OCT scan in the q-th scan mode by considering the predetermined condition, and if suitable data has not been obtained, switches from the q-th scan mode to the (q+1)-th scan mode to perform an OCT scan (q is an integer equal to or greater than 1). Here, at least two scan modes are preset, and the scan mode transition condition is also preset. Furthermore, the (q+1)th scan mode is applied to a position different from that of the qth scan mode and / or to a range wider than that of the qth scan mode, for example. By gradually shifting the scan mode in this manner, even if there is a floater in the examinee's eye, it becomes possible to detect a signal corresponding to the retina at any stage.

[0167] In multiple OCT scans, the orientation of the optical scanner 44 may or may not be constant. In the former case, even if a certain OCT scan is affected by the movement of opacity in the vitreous, other OCT scans may not be affected. In the latter case, it is possible to actively avoid the influence of opacity in the vitreous. However, in the latter case, it is desirable to limit the range of change in the orientation of the optical scanner 44 so that the target site of the distance measurement (e.g., the center of the macula) does not fall outside the range of application of the OCT scan. In particular, when an A-scan is applied, it is necessary to limit the change in the orientation of the optical scanner 44 to a small range. The range of change in the orientation of the optical scanner 44 is set in advance according to, for example, the scan mode to be applied.

[0168] The scanning unit 410 generates a reflection intensity profile or image data from the detection signals obtained by each of the multiple OCT scans, thereby obtaining a data group (multiple data) corresponding to the multiple OCT scans.

[0169] The distance calculation section 460 can obtain a single piece of data from a data group obtained by multiple OCT scans, and perform distance calculation using this single piece of data.

[0170] For example, the distance calculation unit 460 can generate a single piece of data by superimposing (i.e., averaging) at least two pieces of data included in the data group. By averaging two or more pieces of data obtained by two or more OCT scans applied to (substantially) the same location of the subject's eye E, it is possible to reduce or remove noise caused by opacity in the vitreous body.

[0171] In another example, the distance calculation unit 460 can select one data from a data group acquired by multiple OCT scans. In selecting the data, for example, a predetermined evaluation value (e.g., contrast) obtained from the data is referred to. As a result, even if any of the multiple data included in the data group is affected by opacity in the vitreous, it is possible to select data that is not affected or data that is less affected.

[0172] In addition, if the single data obtained by the distance calculation unit 460 does not satisfy a predetermined condition (e.g., a contrast condition), the ophthalmic device 1 can perform a posterior eye OCT scan again or display a message prompting the user to perform a posterior eye OCT scan again.

[0173] <Second Modification> In order to accurately measure the distance between two parts of the test eye E, it is necessary to accurately identify the two parts. For this purpose, it is possible to apply an OCT scan to a three-dimensional region of the test eye E. Examples of scan modes for this purpose include three-dimensional scan, radial scan, and multi-line cross scan. Here, the radial scan is a scan mode consisting of multiple line scans (multiple B-scans) arranged radially, and the multi-line cross scan is a scan mode consisting of two line scan groups that are orthogonal to each other.

[0174] The scan control unit 450 causes the scan unit 410 to perform an OCT scan of a three-dimensional region of the subject's eye E, for example, at least one of an anterior eye OCT scan and a posterior eye OCT scan.

[0175] Typically, in the anterior segment OCT scan, the scan control unit 450 can cause the scan unit 410 to perform an OCT scan of a three-dimensional region including the corneal surface of the subject's eye E. In a state where the alignment is good, an OCT scan is applied to a three-dimensional region of the anterior segment including the corneal apex of the subject's eye E.

[0176] In addition, in the posterior segment OCT scan, the scan control unit 450 causes the scan unit 410 to perform an OCT scan of a three-dimensional region including the retinal surface of the subject's eye E. In a state where the alignment is good, an OCT scan is applied to a three-dimensional region of the posterior segment including the center of the macular of the subject's eye E.

[0177] The distance calculation section 460 can identify characteristic positions corresponding to the characteristic points of the subject's eye E by analyzing data acquired by an OCT scan of a three-dimensional region of the subject's eye E.

[0178] Typically, the distance calculation unit 460 can specify a feature position corresponding to the corneal apex by analyzing data acquired by OCT scanning of a three-dimensional region of the anterior part of the eye including the corneal apex of the subject's eye E. This process includes, for example, a process of specifying an image region corresponding to the corneal surface from data of the three-dimensional region of the anterior part of the eye, and a process of specifying a feature position (corneal apex position) corresponding to the corneal apex from the shape of this image region.

[0179] Furthermore, the distance calculation unit 460 can identify a characteristic position corresponding to the macular center by analyzing data acquired by OCT scanning of a three-dimensional region of the posterior eye including the macular center of the subject's eye E. This process includes, for example, a process of identifying an image region corresponding to the retinal surface (internal limiting membrane, etc.) from data of the three-dimensional region of the posterior eye, and a process of identifying a characteristic position (macular center position) corresponding to the macular center from the shape of this image region, the position of a predetermined tissue, and the position of a predetermined site. An example of the predetermined tissue is a sub-tissue (layer tissue) of the retina, and an example of the predetermined site is the optic disc.

[0180] Distance calculation section 460 calculates the length of a line segment having one end at the identified characteristic position. The length of this line segment is the distance to be measured.

[0181] When the corneal apex position is identified from the data acquired by the anterior OCT scan and the macular center position is identified from the data acquired by the posterior OCT scan, the distance calculation unit 460 calculates the distance of the line segment connecting the corneal apex position and the macular center position. This distance corresponds to the axial length of the subject's eye E.

[0182] <effect> The effects of the ophthalmologic apparatus 1 according to the first embodiment and its modified examples will be described.

[0183] The ophthalmologic apparatus 1 includes a scanning unit 410 , a moving mechanism 150 , a deviation measuring unit 420 , a scan control unit 450 , an alignment control unit 440 , and a distance calculation unit 460 .

[0184] The scan unit 410 is configured to apply an OCT scan to the subject's eye E. The movement mechanism 150 is configured to move at least a part of the scan unit. The deviation measurement unit 420 measures the deviation of the subject's eye E with respect to a predetermined reference position.

[0185] The scan control unit 450 executes a first scan control that causes the scan unit 410 to execute an OCT scan of a first region (e.g., an anterior eye region) including a first site (e.g., a corneal surface) of the subject's eye E, and a second scan control that causes the scan unit 410 to execute an OCT scan of a second region (e.g., a posterior eye region) including a second site (e.g., a retinal surface) different from the first site. The OCT scan executed under the first scan control is called the first OCT scan, and the OCT scan executed under the second scan control is called the second OCT scan.

[0186] The alignment control unit 440 executes a first alignment control for controlling the moving mechanism 150 based on first deviation information of the subject's eye E acquired by the deviation measuring unit 420 before the first scan control, and a second alignment control for controlling the moving mechanism 150 based on second deviation information of the subject's eye E acquired by the deviation measuring unit 420 before the second scan control. The ophthalmologic apparatus 1 can execute alignment in the xy directions and alignment in the z direction.

[0187] The distance calculation unit 460 calculates the distance between the first location and the second location (e.g., the axial length) based on the first data acquired by the scanning unit 410 under the first scan control and the second data acquired by the scanning unit 410 under the second scan control.

[0188] According to such an ophthalmic apparatus 1, since alignment is performed before each of the first OCT scan and the second OCT scan, it is possible to perform both the first OCT scan and the second OCT scan in a well-aligned state. Therefore, for example, when the second OCT scan is performed after the first OCT scan, even if the subject's eye moves between the first OCT scan and the second OCT scan, the second OCT scan is performed after alignment is performed on the subject's eye after the movement, so that it is possible to ensure the reliability of the distance measurement.

[0189] As an optional configuration, the scan unit 410 of the ophthalmologic apparatus 1 includes an interference optical system including a measurement arm that guides the measurement light LS to the subject's eye E and a reference arm that guides the reference light LR. Furthermore, as an optional configuration, the scan unit 410 includes an arm length changer that is provided in at least one of the measurement arm and the reference arm and changes the arm length under the control of the scan control unit 450. The retroreflector 41 and the retroreflector driving unit 41A are examples of the arm length changer provided in the measurement arm. The retroreflector 114 and the retroreflector driving unit 114A are examples of the arm length changer provided in the reference arm.

[0190] In addition, as an optional configuration, the distance calculation unit 460 can execute the following series of processes: (1) a process of calculating the difference (arm length difference) between the first arm length applied in the first scan control (first OCT scan) and the second arm length applied in the second scan control (second OCT scan); (2) a process of identifying a first position corresponding to a first portion of the test eye E (e.g., a signal position corresponding to the corneal surface) by analyzing first data acquired in the first OCT scan; (3) a process of identifying a second position corresponding to a second portion of the test eye E (e.g., a signal position corresponding to the retinal surface) by analyzing second data acquired in the second OCT scan; (4) a process of calculating the distance between the first portion and the second portion (e.g., the axial length) based on the arm length difference calculated in (1), the first position identified in (2), and the second position identified in (3).

[0191] According to this optional configuration, it is possible to provide a specific process for calculating the distance between the first portion and the second portion of the subject's eye E.

[0192] As an optional configuration, the scan control unit 450 can cause the scan unit 410 to execute multiple OCT scans in at least one of the first scan control (first OCT scan) and the second scan control (second OCT scan). In this case, the distance calculation unit 460 can acquire a single piece of data from a data group acquired by multiple OCT scans. Here, the distance calculation unit 460 can generate a single piece of data by averaging the data group acquired by multiple OCT scans. Furthermore, the distance calculation unit 460 can calculate the distance between the first region and the second region using the acquired single piece of data.

[0193] With this optional configuration, even if opacities moving within the vitreous body or the like adversely affect the posterior segment OCT scan, it is possible to reduce or eliminate noise caused by the opacities, or to select data that is not affected by the opacities, or data that is only slightly affected by the opacities, thereby improving the reliability of distance measurements.

[0194] As an optional configuration, the scan control unit 450 can cause the scan unit 410 to execute an OCT scan of a three-dimensional region of the subject's eye E in at least one of the first scan control (first OCT scan) and the second scan control (second OCT scan). In this case, the distance calculation unit 460 can specify a feature position corresponding to a feature point of the subject's eye E by analyzing data acquired by the OCT scan of this three-dimensional region. Furthermore, the distance calculation unit 460 can calculate the length of a line segment having one end at this feature position as the distance between the first location and the second location.

[0195] As a first typical example, in the first scan control (first OCT scan), the scan control unit 450 can cause the scan unit 410 to execute an OCT scan of a three-dimensional region including the corneal surface of the subject's eye E. Furthermore, the distance calculation unit 460 can specify a feature position corresponding to the corneal apex of the subject's eye E by analyzing data acquired by the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460 can calculate the length of a line segment having the corneal apex as one end as the distance between the first location and the second location.

[0196] As a second typical example, in the second scan control (second OCT scan), the scan control unit 450 can cause the scan unit to execute an OCT scan of a three-dimensional region including the retinal surface of the subject's eye E. Furthermore, the distance calculation unit 460 can specify a feature position corresponding to the macular center of the subject's eye E by analyzing data acquired by the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460 can calculate the length of a line segment having one end at the macular center as the distance between the first location and the second location.

[0197] By combining the first and second typical examples, it is possible to obtain the length of a line segment having the corneal apex at one end and the center of the macula at the other end, that is, the axial length of the subject's eye E.

[0198] As an optional configuration, the deviation measuring unit 420 includes an alignment optical system 50 (projection system), two (or more) anterior eye cameras 300 (two or more imaging units), and a deviation calculating unit 430. The alignment optical system 50 projects a light beam onto the anterior eye of the subject's eye E. The two (or more) anterior eye cameras 300 capture images of the anterior eye of the subject's eye E from different directions. The deviation calculating unit 430 calculates the deviation of the subject's eye E relative to a predetermined reference position based on the positions of the images (bright spots) of the light beams depicted in each of the two (or more) anterior eye images acquired by the two (or more) anterior eye cameras 300.

[0199] This optional configuration makes it possible to provide a specific configuration and process for measuring the deviation of the subject's eye E relative to a predetermined reference position.

[0200] Any of the items (configurations, elements, processing, operations, actions, functions, etc.) described in the first embodiment or any of the publicly known items can be combined with the ophthalmic apparatus described in this effect section.

[0201] The first embodiment provides a method for controlling an ophthalmic apparatus. The ophthalmic apparatus includes a scanning unit (410) that applies an OCT scan to an eye E, a moving mechanism (150) that moves at least a part of the scanning unit (410), and a deviation measuring unit (420) that measures deviation of the eye E relative to a predetermined reference position.

[0202] This control method includes a first alignment control step, a first scan control step, a second alignment control step, a second scan control step, and a distance calculation step.

[0203] The first alignment control step controls the moving mechanism 150 based on the first deviation information of the subject's eye E acquired by the deviation measurement unit 420. The first scan control step causes the scan unit 410 to execute an OCT scan of a first region including a first part of the subject's eye E. This OCT scan is called a first OCT scan.

[0204] The second alignment control step controls the moving mechanism (150) based on the second deviation information of the subject's eye (E) acquired by the deviation measurement unit (420). The second scan control step causes the scan unit (410) to execute an OCT scan of a second region including a second portion of the subject's eye (E) different from the first portion. This OCT scan is called a second OCT scan.

[0205] The distance calculation step calculates the distance between the first location and the second location based on first data acquired by the scanning unit (410) in the first scan control step and second data acquired by the scanning unit (410) in the second scan control step.

[0206] According to this method for controlling an ophthalmic apparatus, since alignment is performed before each of the first OCT scan and the second OCT scan, it is possible to perform both the first OCT scan and the second OCT scan in a well-aligned state, thereby ensuring the reliability of distance measurement.

[0207] Any of the items (configurations, elements, processes, operations, actions, functions, etc.) described in the first embodiment or any of the publicly known items can be combined with the control method.

[0208] It is possible to configure a program for causing a computer to execute such a control method. This program may include, for example, any of the above-mentioned programs for operating the ophthalmic apparatus 1 of the first embodiment or the modified example thereof.

[0209] It is also possible to create a computer-readable non-transitory recording medium having such a program recorded therein. This non-transitory recording medium may be in any form, and examples of such a recording medium include a magnetic disk, an optical disk, a magneto-optical disk, and a semiconductor memory.

[0210] Second Embodiment As described above, the first embodiment aims to improve the reliability of distance measurement of the subject's eye by performing alignment before each of the first OCT scan and the second OCT scan. In other words, the first embodiment aims to improve the reliability of distance measurement by increasing the reliability of the first OCT scan and the second OCT scan.

[0211] In contrast, the second embodiment aims to improve the reliability of distance measurement by correcting the alignment error present in the OCT scan in data processing.

[0212] Hereinafter, unless otherwise specified, the description of the same matters as those in the first embodiment will be omitted. In addition, among the elements included in the second embodiment, the elements similar to those in the first embodiment are given the same reference numerals as the corresponding elements in the first embodiment. In addition, in the following description, the elements of the first embodiment will be referred to as necessary.

[0213] <composition> An example of the configuration of an ophthalmic apparatus according to this embodiment is shown in Fig. 7. The ophthalmic apparatus 1A has a hardware configuration similar to that of the ophthalmic apparatus 1 according to the first embodiment (see Figs. 1, 2, 3A, 4A, and 4B). The configuration shown in Fig. 7 is applied in place of the configuration shown in Fig. 3B of the first embodiment.

[0214] In the ophthalmologic apparatus 1A, the scan unit 410, the deviation measuring unit 420, and the moving mechanism 150 each have the same configuration, function, and action as those in the first embodiment.

[0215] The scan unit 410 acquires data by applying an OCT scan to the subject's eye E. As in the first embodiment, the scan unit 410 includes an interference optical system including a measurement arm that guides measurement light LS to the subject's eye E and a reference arm that guides reference light LS. Furthermore, as in the first embodiment, the scan unit 410 includes an arm length changer provided in at least one of the measurement arm and the reference arm.

[0216] The deviation measuring part 420 measures the deviation of the subject's eye E relative to a preset reference position. As in the first embodiment, the deviation measuring part 420 may include an alignment optical system 50, an anterior eye camera 300, and a deviation calculating part 430. The deviation measuring part 420 shown in Fig. 7 is an example applicable when the position of the subject's eye E is defined as a bright spot position. When another definition (for example, the pupil center position, the corneal apex position, etc.) is used, a configuration corresponding thereto is applied.

[0217] An alignment control unit 440A described later can execute alignment control based on the deviation measurement result (deviation information) acquired by the deviation measurement unit 420. In addition, a distance calculation unit 460A described later can calculate a predetermined distance in the subject's eye E in consideration of the deviation information acquired by the deviation measurement unit 420.

[0218] Although details will be described later, the ophthalmologic apparatus 1A executes a first OCT scan on a first region (e.g., an anterior eye region) including a first portion (e.g., a corneal surface) of the subject's eye E, and a second OCT scan on a second region (e.g., a posterior eye region) including a second portion (e.g., a retinal surface). Note that the order of execution of the first OCT scan and the second OCT scan is arbitrary.

[0219] The deviation measuring unit 420 can perform a first deviation measurement corresponding to the first OCT scan to obtain first deviation information, and can perform a second deviation measurement corresponding to the second OCT scan to obtain second deviation information.

[0220] The first displacement measurement is performed before, during, or after the first OCT scan. Similarly, the second displacement measurement is performed before, during, or after the second OCT scan. Typically, the first displacement measurement is performed immediately before, during, or after the first OCT scan, and the second displacement measurement is performed immediately before, during, or after the second OCT scan.

[0221] A distance calculation section 460A described later can calculate a predetermined distance in the subject's eye E by considering either or both of the first deviation information and the second deviation information acquired by the deviation measurement section 420. An alignment control section 440A described later can execute alignment control based on either the first deviation information and the second deviation information acquired by the deviation measurement section 420. Note that a configuration in which alignment control (first alignment control) is performed based on the first deviation information and alignment control (second alignment control) is performed based on the second deviation information corresponds to the first embodiment.

[0222] As in the first embodiment, the moving mechanism 150 can move the scan unit 410 (particularly, the measurement arm of the interference optical system) relative to the eye E.

[0223] The alignment control unit 440A and the scan control unit 450A are provided in the control unit 210A. The control unit 210A is provided in place of the control unit 210 of the first embodiment. The control unit 210A includes a processor and controls each unit of the ophthalmic apparatus 1A. The control unit 210A includes a main control unit and a storage unit (not shown). The control unit 210A is realized by cooperation between hardware including a circuit and control software.

[0224] As in the first embodiment, the alignment control unit 440A executes alignment control for controlling the moving mechanism 150 based on the deviation information acquired by the deviation measuring unit 420.

[0225] The scan control unit 450A executes a first scan control for making the scan unit 410 execute an OCT scan of a first region (e.g., an anterior eye region) including a first site (e.g., a corneal surface) of the subject's eye E, and a second scan control for making the scan unit 410 execute an OCT scan of a second region (e.g., a posterior eye region) including a second site (e.g., a retinal surface) different from the first site. The first scan control and the second scan control are executed in the same manner as the scan control unit 450 of the first embodiment. The OCT scan executed by the first scan control is called the first OCT scan, and the OCT scan executed by the second scan control is called the second OCT scan.

[0226] As described above, the deviation measurement unit 420 performs deviation measurement of the test eye E before, during, or after the execution of the first scan control to obtain first deviation information, and performs deviation measurement of the test eye E before, during, or after the execution of the second scan control to obtain second deviation information.

[0227] The distance calculation unit 460A calculates the distance (e.g., axial length) between a first location (e.g., corneal surface) and a second location (e.g., retinal surface) of the subject eye E based on either or both of the first and second deviation information, the first data acquired in the first OCT scan, and the second data acquired in the second OCT scan.

[0228] In other words, the distance calculation section 460A performs distance calculation taking into consideration either or both of the alignment error during the first OCT scan (first deviation information) and the alignment error during the second OCT scan (second deviation information).

[0229] The distance calculation section 460A executes, for example, the following series of processes. First, the distance calculation section 460A calculates the difference (arm length difference) between the first arm length applied in the first OCT scan and the second arm length applied in the second OCT scan. Second, the distance calculation section 460A analyzes the first data acquired by the first OCT scan to identify a first position (for example, a signal position on the corneal surface) corresponding to a first portion of the subject's eye E. Third, the distance calculation section 460A analyzes the second data acquired by the second OCT scan to identify a second position (for example, a signal position on the retinal surface) corresponding to a second portion of the subject's eye E. The first to third processes are each executed in the same manner as in the first embodiment. Fourth, the distance calculation unit 460A calculates the distance between the first portion and the second portion based on the arm length difference calculated in the first process, the first position identified in the second process, the second position identified in the third process, and the deviation information (at least one of the first deviation information and the second deviation information) acquired by the deviation measurement unit 420.

[0230] An example of such calculation processing will be described with reference to Fig. 8. As in Fig. 5 of the first embodiment, the symbol C indicates the corneal apex of the subject's eye E, and the symbol M indicates the macular center. A straight line Ax passing through the corneal apex C and the macular center M indicates the ocular axis of the subject's eye E.

[0231] The symbol K indicates the center of curvature of the corneal surface at the corneal apex C. The center of curvature K is the center of the circle of curvature (osculating circle) at the corneal apex C. The radius of this circle of curvature, that is, the radius of curvature of the corneal surface at the corneal apex C, is defined as r.

[0232] Symbol G indicates the path (incident path) of the measuring light LS projected onto the macular center M. Symbol H indicates the intersection of the incident path G and the corneal surface of the test eye E, that is, the incident position of the measuring light LS with respect to the test eye E.

[0233] The deviation (height) of the incident path G with respect to the eye axis Ax is denoted by h. If it is assumed that the shape of the corneal surface is substantially spherical, or if it is assumed that the height h is sufficiently small (i.e., if it is assumed that the alignment error is sufficiently small), it can be considered that the distance between the incident position H and the center of curvature K is equal to the radius of curvature r at the corneal apex C.

[0234] The angle that the line segment connecting the incident position H and the center of curvature K makes with the ocular axis Ax is defined as θ. Also, the angle that the line segment connecting the incident position H and the macular center M makes with the ocular axis Ax is defined as φ.

[0235] The length of the line segment connecting the incident position H and the macular center M is defined as ALm. This length ALm corresponds to the measured value of the axial length of the test eye E obtained from data acquired by an OCT scan using the measurement light LS that passes through the incident path G and is projected onto the macular center M.

[0236] Let AL be the axial length (true value) of the test eye E. Let AL1 be the distance between the corneal apex C and the incident position H in the direction along the ocular axis Ax, that is, the magnitude of the ocular axis (Ax) direction component of the vector that starts at the corneal apex C and ends at the incident position H. Let AL2 be the distance between the incident position H and the macular center M in the direction along the ocular axis Ax, that is, the magnitude of the ocular axis (Ax) direction component of the vector that starts at the macular center M and ends at the incident position H.

[0237] As is clear from FIG. 8, the axial length AL is expressed by the following equation: AL=AL1+AL2=(rr×cosθ)+ALm×cosφ=(rr×cos(arcsin(h / r)))+ALm×cos(arcsin(h / ALm)).

[0238] Here, the corneal curvature radius r is assumed to be acquired in advance by a corneal shape measuring device such as a keratometer. The height h is an alignment error in the x and y directions measured by the deviation measuring unit 420, and is included in the deviation information. The axial length measurement value ALm is a value of the axial length calculated by the ophthalmic apparatus 1A in the same manner as in the first embodiment. The axial length AL can be calculated by substituting these values ​​r, h, and ALm into the above formula.

[0239] The distance calculation unit 460A prestores, for example, the above formula and the corneal curvature radius value (r) of the subject's eye E. The distance calculation unit 460A calculates the axial length value (AL) of the subject's eye E by substituting this corneal curvature radius value (r), the deviation (h) in the x and y directions included in the deviation information acquired by the deviation measurement unit 420, and the axial length value (ALm) measured using an OCT scan into the above formula.

[0240] In this example, a case where alignment errors in the x and y directions occur during posterior eye OCT scanning has been described; however, it will be clear to those skilled in the art that similar calculations can be performed when alignment errors in the x and y directions occur during anterior eye OCT scanning, or when alignment errors occur during both anterior eye OCT scanning and posterior eye OCT scanning.

[0241] In this example, only the refraction of the measurement light LS on the corneal surface is considered, but it is also possible to consider other refractive index boundaries. For example, the refraction of the measurement light LS on the back surface of the cornea, the front surface of the crystalline lens, the back surface of the crystalline lens, etc. may be considered.

[0242] In addition to the alignment error in the xy directions, it is also possible to take into consideration the alignment error in the z direction. The alignment error in the z direction is found by the deviation measuring unit 420, as in the first embodiment.

[0243] <Operation> An example of the operation of the ophthalmologic apparatus 1A according to the present embodiment will be described below. A first operation example in which distance calculation is performed taking into consideration both the first deviation information and the second deviation information, and a second operation example in which distance calculation is performed taking into consideration the second deviation information while using the first deviation information for alignment will be described below.

[0244] <First operation example> A first operation example of the ophthalmic apparatus 1A is shown in Fig. 9. In this operation example, for example, a fixation target for macular imaging is presented to the subject's eye E. Furthermore, a preliminary alignment may be performed before step S21.

[0245] (S21: Change the arm length to obtain the corneal signal) In the same manner as step S2 in the first embodiment, the scan control unit 450A (and the data processing unit 230) changes either or both of the measurement arm length and the reference arm length so as to obtain a signal corresponding to the cornea of ​​the test eye E.

[0246] (S22: Obtain the first deviation information) After the change in the arm length in step S21 is completed, the deviation measuring section 420 performs a first deviation measurement corresponding to a first OCT scan (anterior segment OCT scan) to obtain first deviation information.

[0247] (S23: OCT scan applied to the anterior segment) When the deviation information acquisition in step S22 is completed, the scan control unit 450A executes control for applying an OCT scan to the anterior segment of the subject's eye E. In this example, the scan control unit 450A executes a first scan control for causing the scan unit 410 to execute an OCT scan of the anterior segment region including the corneal surface of the subject's eye E. Step S23 is executed in the same manner as step S3 in the first embodiment.

[0248] (S24: Generate reflection intensity profile) The scanning unit 410 (image forming unit 220) generates a reflection intensity profile from the data acquired by the OCT scan in step S23. This reflection intensity profile is, for example, data corresponding to the A-line to which the A-scan is applied in step S23.

[0249] (S25: Record the retroreflector position, reflection intensity profile, and first deviation information) The ophthalmic apparatus 1 (e.g., the distance calculation unit 460A) records the position of the retroreflector when the OCT scan is performed in step S23 and the reflection intensity profile generated in step S24 in the same manner as in step S5 in the first embodiment. Furthermore, the ophthalmic apparatus 1 (e.g., the distance calculation unit 460A) records the first deviation information acquired in step S22.

[0250] (S26: Change the arm length to obtain retinal signals) Next, the scan control unit 450A (and the data processing unit 230) changes either or both of the measurement arm length and the reference arm length so that a signal corresponding to the retina of the subject's eye E can be obtained.

[0251] (S27: Obtain second deviation information) After the arm length adjustment in step S26 is completed, the deviation measurement unit 420 performs a second deviation measurement corresponding to a second OCT scan (posterior segment OCT scan) to obtain second deviation information. This process is performed in the same manner as in step S22.

[0252] (S28: OCT scan applied to the posterior segment) When the acquisition of deviation information in step S27 is completed, the scan control unit 450A executes control for applying an OCT scan to the posterior segment of the subject's eye E. In this example, the scan control unit 450A executes a second scan control for causing the scan unit 410 to execute an OCT scan of the posterior segment region including the retinal surface of the subject's eye E.

[0253] (S29: Generate reflection intensity profile) The scanning unit 410 (image forming unit 220) generates a reflection intensity profile from the data acquired by the OCT scan in step S28. This reflection intensity profile is, for example, data corresponding to the A-line to which the A-scan was applied in step S28.

[0254] (S30: Record the retroreflector position, reflection intensity profile, and second deviation information) In the same manner as in step S25, the ophthalmic apparatus 1 (e.g., the distance calculation unit 460A) records the position of the retroreflector when the OCT scan in step S28 is performed, the reflection intensity profile generated in step S29, and the second deviation information acquired in step S27.

[0255] (S31: Calculate axial length) The distance calculation unit 460A calculates the distance between the corneal surface and the retinal surface based on the position, reflection intensity profile, and first deviation information of the retroreflector recorded in step S25, and the position, reflection intensity profile, and second deviation information of the retroreflector recorded in step S30.

[0256] In this example, the distance calculation unit 460A first calculates the difference between the first arm length and the second arm length (arm length difference) based on the position of the retroreflector recorded in step S25 (i.e., the first arm length applied to the anterior OCT scan) and the position of the retroreflector recorded in step S30 (i.e., the second arm length applied to the posterior OCT scan). Furthermore, the distance calculation unit 460A analyzes the reflection intensity profile recorded in step S25 to identify a position (first position) corresponding to the corneal surface, and analyzes the reflection intensity profile recorded in step S30 to identify a position (second position) corresponding to the retinal surface. Then, the distance calculation unit 460A calculates the axial length of the subject's eye E based on the arm length difference, the first position, and the second position, as well as the first deviation information recorded in step S25 and the second deviation information recorded in step S30. This calculation is performed, for example, according to the method described with reference to FIG. 8. In this example, both the alignment error in the anterior eye OCT scan and the alignment error in the posterior eye OCT scan are taken into consideration. This is the end of the operation according to this operation example (END).

[0257] <Second operation example> A second operation example of the ophthalmic apparatus 1A is shown in Fig. 10. In this operation example, for example, a fixation target for macular imaging is presented to the subject's eye E. Furthermore, a preliminary alignment may be performed before step S41.

[0258] (S41: Change the arm length to obtain the corneal signal) The scan control unit 450A (and the data processing unit 230) changes either or both of the measurement arm length and the reference arm length so that a signal corresponding to the cornea of ​​the subject's eye E is obtained.

[0259] (S42: Obtain the first deviation information and perform alignment) After the change of the arm length in step S41 is completed, the deviation measurement unit 420 performs a first deviation measurement corresponding to a first OCT scan (anterior segment OCT scan) to obtain first deviation information. The alignment control unit 440A executes alignment control to control the moving mechanism 150 based on the acquired first deviation information. The alignment control is executed in the same manner as in the first embodiment.

[0260] (S43: OCT scan applied to the anterior segment) After the alignment in step S42 is completed, the scan control unit 450A executes control for applying an OCT scan to the anterior segment of the subject's eye E. In this example, the scan control unit 450A executes a first scan control for causing the scan unit 410 to execute an OCT scan of the anterior segment region including the corneal surface of the subject's eye E. It can be assumed that this anterior segment OCT scan is performed under a good alignment state.

[0261] (S44: Generate reflection intensity profile) The scanning unit 410 (image forming unit 220) generates a reflection intensity profile from the data acquired by the OCT scan in step S43. This reflection intensity profile is, for example, data corresponding to the A-line to which the A-scan is applied in step S43.

[0262] (S45: Record the retroreflector position and reflection intensity profile) The ophthalmic apparatus 1 (eg, the distance calculation unit 460A) records the position of the retroreflector when the OCT scan is performed in step S43 and the reflection intensity profile generated in step S44.

[0263] (S46: Change the arm length to obtain retinal signals) Next, the scan control unit 450A (and the data processing unit 230) changes either or both of the measurement arm length and the reference arm length so that a signal corresponding to the retina of the subject's eye E can be obtained.

[0264] (S47: Obtain second deviation information) After the arm length adjustment in step S46 is completed, the deviation measurement unit 420 performs a second deviation measurement corresponding to a second OCT scan (posterior OCT scan) to obtain second deviation information. Unlike the anterior OCT scan, which is assumed to be performed under good alignment conditions, good alignment conditions are not guaranteed in the posterior alignment, so only the second deviation information is taken into account in the distance calculation (step S51 described below).

[0265] (S48: OCT scan applied to the posterior segment) When the acquisition of deviation information in step S47 is completed, the scan control unit 450A executes control for applying an OCT scan to the posterior segment of the subject's eye E. In this example, the scan control unit 450A executes a second scan control for causing the scan unit 410 to execute an OCT scan of the posterior segment region including the retinal surface of the subject's eye E.

[0266] (S49: Generate reflection intensity profile) The scanning unit 410 (image forming unit 220) generates a reflection intensity profile from the data acquired by the OCT scan in step S48. This reflection intensity profile is, for example, data corresponding to the A-line to which the A-scan was applied in step S48.

[0267] (S50: Record the retroreflector position, reflection intensity profile, and second deviation information) The ophthalmic apparatus 1 (e.g., the distance calculation unit 460A) records the position of the retroreflector when the OCT scan in step S48 is performed, the reflection intensity profile generated in step S49, and the second deviation information acquired in step S47.

[0268] (S51: Calculate axial length) The distance calculation unit 460A calculates the distance between the corneal surface and the retinal surface based on the position and reflection intensity profile of the retroreflector recorded in step S45, and the position, reflection intensity profile, and second deviation information of the retroreflector recorded in step S50.

[0269] In this example, the distance calculation unit 460A first calculates the difference between the first arm length and the second arm length (arm length difference) based on the position of the retroreflector recorded in step 45 (i.e., the first arm length applied to the anterior OCT scan) and the position of the retroreflector recorded in step 50 (i.e., the second arm length applied to the posterior OCT scan). Furthermore, the distance calculation unit 460A analyzes the reflection intensity profile recorded in step 45 to identify a position (first position) corresponding to the corneal surface, and analyzes the reflection intensity profile recorded in step S50 to identify a position (second position) corresponding to the retinal surface. Then, the distance calculation unit 460A calculates the axial length of the subject's eye E based on the arm length difference, the first position, the second position, and the second position, as well as the second deviation information recorded in step S50. This calculation is performed, for example, according to the method described with reference to FIG. 8. With the above, the operation according to this operation example is completed (end).

[0270] <Modification of the second embodiment> Modifications applicable to the ophthalmic apparatus 1A according to the second embodiment will be described below. Unless otherwise specified, the reference characters used in the description of the ophthalmic apparatus 1 and / or the ophthalmic apparatus 1A will be used in the following description.

[0271] First Modified Example Similar to the first modification of the first embodiment, to address the adverse effects of intravitreal opacities on the posterior segment OCT scan, the OCT scans can be applied to the posterior segment multiple times, with the scan unit 410 performing the repetitive OCT scans under the control of the scan control unit 450A.

[0272] The scanning unit 410 generates a reflection intensity profile or image data from the detection signals obtained by each of the multiple OCT scans. This allows a data group (multiple data) corresponding to the multiple OCT scans to be obtained. The distance calculation unit 460A can obtain a single data from the data group obtained by the multiple OCT scans and perform distance calculation using this single data.

[0273] <Second Modification> As in the second modified example of the first embodiment, in order to accurately identify two parts of the subject's eye E, it is possible to apply an OCT scan to a three-dimensional region of the subject's eye E. The scan control unit 450A causes the scan unit 410 to perform an OCT scan of the three-dimensional region of the subject's eye E, for example, in at least one of an anterior eye OCT scan and a posterior eye OCT scan.

[0274] The distance calculation unit 460A can specify a feature position corresponding to a feature point of the subject's eye E by analyzing data acquired by OCT scanning of a three-dimensional region of the subject's eye E, and calculate the length of a line segment having one end at the specified feature position. The length of this line segment is the distance to be measured.

[0275] <effect> The effects of the ophthalmologic apparatus 1A according to the second embodiment and its modified example will be described.

[0276] The ophthalmologic apparatus 1A includes a scanning unit 410, a deviation measuring unit 420, a scan control unit 450A, and a distance calculation unit 460A.

[0277] The scan unit 410 applies an OCT scan to the subject's eye E. The deviation measurement unit 420 measures the deviation of the subject's eye E with respect to a predetermined reference position.

[0278] The scan control unit 450A executes a first scan control that causes the scan unit 410 to perform an OCT scan of a first region (e.g., an anterior eye region) including a first site (e.g., a corneal surface) of the subject eye E, and a second scan control that causes the scan unit 410 to perform an OCT scan of a second region (e.g., a posterior eye region) including a second site (e.g., a retinal surface) different from the first site.

[0279] The distance calculation unit 460A calculates the distance between the first and second locations of the subject eye E (e.g., axial length) based on at least one of the first deviation information of the subject eye E acquired by the deviation measurement unit 420 in response to the first scan control and the second deviation information of the subject eye E acquired by the deviation measurement unit 420 in response to the second scan control, the first data acquired by the scanning unit 410 under the first scan control, and the second data acquired by the scanning unit 410 under the second scan control.

[0280] According to such an ophthalmic apparatus 1A, an alignment error (deviation information) in either one or both of the first OCT scan and the second OCT scan can be acquired, and distance calculation can be performed taking into consideration the alignment error. Therefore, for example, when the second OCT scan is performed after the first OCT scan, it is possible to ensure the reliability of distance measurement even if the subject's eye moves between the first OCT scan and the second OCT scan.

[0281] As an optional configuration, the deviation measuring unit 420 may obtain one deviation information corresponding to one of the first and second scan controls, and obtain the other deviation information before the other scan control. Furthermore, the ophthalmic apparatus 1A may include a moving mechanism 150 and an alignment control unit 440A. The moving mechanism 150 moves at least a part of the scan unit 410. The alignment control unit 440A executes alignment control for controlling the moving mechanism 150 based on the other deviation information before the other scan control. The distance calculation unit 460A can perform distance calculation based on the one deviation information, the first data, and the second data.

[0282] For example, in the second operation example shown in FIG. 10, the deviation measurement unit 420 acquires the first deviation information and performs alignment before the first scan control, and also performs distance calculation based on the second deviation information acquired in response to the second scan control, the first data, and the second data.

[0283] According to this optional configuration, while one of the first OCT scan and the second OCT scan is performed after alignment, distance calculation can be performed taking into account alignment error in the other scan, making it possible to perform distance measurement with high reliability.

[0284] As an optional configuration, the scan unit 410 may include an interference optical system and an arm length changer. The interference optical system includes a measurement arm that guides the measurement light LS to the subject's eye E and a reference arm that guides the reference light LR. The arm length changer is provided in at least one of the measurement arm and the reference arm, and changes the arm length under the control of the scan control unit 450A. The retroreflector 41 and the retroreflector driving unit 41A are examples of the arm length changer provided in the measurement arm. The retroreflector 114 and the retroreflector driving unit 114A are examples of the arm length changer provided in the reference arm.

[0285] In addition, as an optional configuration, the distance calculation unit 460A can execute the following series of processes: (1) a process of calculating the difference (arm length difference) between the first arm length applied in the first scan control (first OCT scan) and the second arm length applied in the second scan control (second OCT scan); (2) a process of identifying a first position (e.g., a signal position on the corneal surface) corresponding to a first portion of the test eye E by analyzing first data acquired in the first OCT scan; (3) a process of identifying a second position (e.g., a signal position on the retinal surface) corresponding to a second portion of the test eye E by analyzing second data acquired in the second OCT scan; (4) a process of calculating the distance (e.g., the axial length) between the first portion and the second portion based on the arm length difference calculated in (1), the first position identified in (2), the second position identified in (3), and at least one of the first deviation information and the second deviation information acquired by the deviation measurement unit 420.

[0286] Here, the distance calculation section 460A may be configured as follows. First, the distance calculation section 460A calculates a provisional distance between the first and second locations based on the arm length difference and the first and second locations. Furthermore, the distance calculation section 460A calculates the distance between the first and second locations based on the provisional distance, at least one of the first and second deviation information, and the corneal curvature radius of the subject's eye E acquired in advance.

[0287] As a specific example of such distance calculation, when the provisional distance between the first portion and the second portion is ALm, one of the first and second deviation information is h, the corneal curvature radius is r, and the distance (true value) between the first portion and the second portion is AL, the distance calculation unit 460A can calculate the distance AL by the calculation formula AL=(rr×cos(arcsin(h / r)))+ALm×cos(arcsin(h / ALm)).

[0288] According to these optional configurations, it is possible to provide a specific process for calculating the distance between the first portion and the second portion of the subject's eye E.

[0289] As an optional configuration, the scan control unit 450A can cause the scan unit 410 to execute multiple OCT scans in at least one of the first scan control (first OCT scan) and the second scan control (second OCT scan). In this case, the distance calculation unit 460A can acquire a single piece of data from a data group acquired by multiple OCT scans. Here, the distance calculation unit 460A can generate a single piece of data by averaging the data group acquired by multiple OCT scans. Furthermore, the distance calculation unit 460A can calculate the distance between the first region and the second region (for example, the above-mentioned provisional distance) using the acquired single piece of data.

[0290] With this optional configuration, even if opacities moving within the vitreous body or the like adversely affect the posterior segment OCT scan, it is possible to reduce or eliminate noise caused by the opacities, or to select data that is not affected by the opacities, or data that is only slightly affected by the opacities, thereby improving the reliability of distance measurements.

[0291] As an optional configuration, the scan control unit 450A can cause the scan unit 410 to execute an OCT scan of a three-dimensional region of the subject's eye E in at least one of the first scan control (first OCT scan) and the second scan control (second OCT scan). In this case, the distance calculation unit 460A can specify a feature position corresponding to a feature point of the subject's eye E by analyzing data acquired by the OCT scan of this three-dimensional region. Furthermore, the distance calculation unit 460A can calculate the length of a line segment having one end at this feature position as the distance between the first portion and the second portion (for example, the above-mentioned provisional distance).

[0292] As a first typical example, in the first scan control (first OCT scan), the scan control unit 450A can cause the scan unit 410 to execute an OCT scan of a three-dimensional region including the corneal surface of the subject's eye E. Furthermore, the distance calculation unit 460A can specify a feature position corresponding to the corneal apex of the subject's eye E by analyzing data acquired by the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460A can calculate the length of a line segment having the corneal apex as one end as the distance between the first location and the second location (for example, the above-mentioned provisional distance).

[0293] As a second typical example, in the second scan control (second OCT scan), the scan control unit 450A can cause the scan unit to execute an OCT scan of a three-dimensional region including the retinal surface of the subject's eye E. Furthermore, the distance calculation unit 460A can specify a feature position corresponding to the macular center of the subject's eye E by analyzing data acquired by the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460A can calculate the length of a line segment having one end at the macular center as the distance between the first location and the second location (for example, the above-mentioned provisional distance).

[0294] By combining the first and second typical examples, it is possible to obtain the length of a line segment having the corneal apex at one end and the center of the macula at the other end, that is, the axial length of the subject's eye E.

[0295] As an optional configuration, the deviation measuring unit 420 includes an alignment optical system 50 (projection system), two (or more) anterior eye cameras 300 (two or more imaging units), and a deviation calculating unit 430. The alignment optical system 50 projects a light beam onto the anterior eye of the subject's eye E. The two (or more) anterior eye cameras 300 capture images of the anterior eye of the subject's eye E from different directions. The deviation calculating unit 430 calculates the deviation of the subject's eye E relative to a predetermined reference position based on the positions of the images (bright spots) of the light beams depicted in each of the two (or more) anterior eye images acquired by the two (or more) anterior eye cameras 300.

[0296] This optional configuration makes it possible to provide a specific configuration and process for measuring the deviation of the subject's eye E relative to a predetermined reference position.

[0297] Any of the items (configurations, elements, processes, operations, actions, functions, etc.) described in the second embodiment or any of the publicly known items can be combined with the ophthalmic device described in this Effects section. Any of the items (configurations, elements, processes, operations, actions, functions, etc.) described in the first embodiment can be combined with the ophthalmic device described in this Effects section.

[0298] The second embodiment provides a method for controlling an ophthalmic apparatus. The ophthalmic apparatus includes a scanning unit (410) that applies an OCT scan to an eye E to be examined, and a deviation measuring unit (420) that measures deviation of the eye E to be examined with respect to a predetermined reference position.

[0299] This control method includes a first scan control step, a second scan control step, a deviation measuring step, and a distance calculation step.

[0300] The first scan control step causes the scan unit (410) to perform an OCT scan on a first region including a first part of the subject's eye (E). This OCT scan is called the first OCT scan. The second scan control step causes the scan unit (410) to perform an OCT scan on a second region including a second part different from the first part of the subject's eye (E). This OCT scan is called the second OCT scan.

[0301] The deviation measurement step causes the deviation measurement unit (420) to execute at least one of a step of acquiring first deviation information of the test eye (E) in response to a first scan control and a step of acquiring second deviation information of the test eye (E) in response to a second scan control.

[0302] The distance calculation step calculates the distance between the first and second locations of the test eye (E) based on at least one of the first and second deviation information acquired in the deviation measurement step, the first data acquired by the scan unit (410) in the first scan control step, and the second data acquired by the scan unit (410) in the second scan control step.

[0303] According to this control method for an ophthalmic apparatus, it is possible to obtain an alignment error (deviation information) in either one or both of the first OCT scan and the second OCT scan, and perform distance calculation taking the alignment error into consideration, thereby ensuring the reliability of distance measurement.

[0304] In addition, it is possible to combine any of the matters described in the first embodiment (configuration, elements, processing, operation, action, function, etc.), any of the matters described in the second embodiment (configuration, elements, processing, operation, action, function, etc.), or any publicly known matters with the control method.

[0305] It is possible to configure a program for causing a computer to execute such a control method. This program may include, for example, any of the above-mentioned programs for operating the ophthalmic apparatus 1A of the second embodiment or the modified example thereof.

[0306] It is also possible to create a computer-readable non-transitory recording medium having such a program recorded therein. This non-transitory recording medium may be in any form, examples of which include a magnetic disk, an optical disk, a magneto-optical disk, and a semiconductor memory.

[0307] <Other matters> The above-described embodiments are merely examples of the implementation of the present invention. Anyone who wishes to implement the present invention may make any modifications (omissions, substitutions, additions, etc.) within the scope of the gist of the present invention.

[0308] For example, the ophthalmic apparatus according to the embodiment may include a configuration for measuring the characteristics of the subject's eye. As a specific example, the ophthalmic apparatus according to the embodiment may include a configuration for measuring the corneal curvature radius of the subject's eye. The configuration for measuring the corneal curvature radius may include an optical system, a calculation system, and a control system similar to those of a conventional corneal shape measuring device. An example of a configuration for measuring the corneal curvature radius is disclosed in Japanese Patent Application Laid-Open No. 2017-063978 by the present applicant, which uses a kerato plate (kerato ring) or a placido plate (placido ring). In addition, the corneal curvature radius may be measured by an anterior segment OCT scan. Note that the configuration for measuring the corneal curvature radius is not limited to these examples, and may be a configuration using any known technology.

[0309] The characteristics of the subject's eye that can be measured by the ophthalmic apparatus according to the embodiment are not limited to the corneal radius of curvature. For example, the ophthalmic apparatus according to the embodiment may include a configuration for measuring the refractive power of the subject's eye (spherical power, cylindrical power, cylindrical axis angle, etc.). The configuration for measuring the refractive power of the subject's eye may include an optical system, a calculation system, and a control system similar to those of a conventional refractive power measuring device (refractometer). An example of the configuration for measuring the refractive power is disclosed in JP 2017-063978 A by the present applicant.

[0310] When the ophthalmic device of the embodiment has an eye refractive power measurement function, instead of using the focus optical system 60 as disclosed above, the ophthalmic device can determine the focus position using the eye refractive power measurement function and move the OCT focusing lens 43 to focus at this position.

[0311] In the above disclosure, the method using the alignment index and the method using the anterior eye camera have been described as applicable alignment methods, but other alignment methods may be applied. An example of the other alignment method is a method using an optical lever. Note that alignment methods for ophthalmic devices using an optical lever are disclosed in, for example, JP 2012-148032 A and JP 2018-050922 A.

[0312] The deviation measuring unit of the ophthalmic apparatus of this example uses an optical lever to measure the deviation of the subject's eye relative to a predetermined reference position. The predetermined reference position is, for example, a position corresponding to a working distance, i.e., a position separated from the subject's eye in the z direction by the predetermined working distance, and the deviation to be measured is typically a deviation in the z direction.

[0313] The deviation measuring unit of this example includes a projection system that projects a light beam obliquely onto the anterior segment of the eye to be examined, and an image sensor that detects the light beam reflected from the anterior segment of the eye of the subject. The configuration and arrangement of the projection system and the image sensor may be the same as those of a conventional optical lever type alignment means.

[0314] A typical projection system includes a light source and a lens. The optical axis of the typical projection system is inclined at a first angle in a first direction with respect to the optical axis of the measurement arm (optical axis of the objective lens). A typical image sensor is a CCD image sensor or a CMOS image sensor, and is a line sensor or an area sensor. Typically, an imaging lens is disposed between the image sensor and the subject's eye E. The optical axis of the detection system including the image sensor and the imaging lens is inclined at a second angle equal to the first angle with respect to the optical axis of the measurement arm in a second direction opposite to the first direction.

[0315] With this configuration and arrangement, when the projection system and the detection system are located within a predetermined range with respect to the subject's eye, the image sensor can detect the reflected light beam. Also, when the relative positions between the projection system and the detection system and the subject's eye change, the detection position of the reflected light beam by the image sensor changes. In other words, the projection position of the reflected light beam with respect to the light receiving area (light receiving element array) of the image sensor changes depending on the relative positions between the projection system and the detection system and the subject's eye.

[0316] The deviation measurement unit of this example includes a deviation calculation unit that calculates the deviation of the subject's eye based on the detection position of the reflected light beam by the image sensor. The calculation performed by the deviation calculation unit of this example is the same as the calculation performed by a conventional optical lever type alignment means, and typically calculates the deviation in the z direction. The deviation calculation unit of this example is realized by the cooperation of hardware including a circuit and deviation calculation software.

[0317] According to this example, it is possible to provide a specific configuration and processing for measuring the deviation of the test eye relative to a predetermined reference position, similar to the case where an alignment indicator is used or where two or more anterior eye cameras are used. [Explanation of symbols]

[0318] 1 Ophthalmology equipment 50 Alignment Optical System 150 Moving mechanism 210, 210A Control section 300 Anterior Eye Camera 410 Scanning section 420 Displacement measurement unit 430 Deviation Calculation Unit 440, 440A Alignment Control Unit 450, 450A Scan Control Unit

Claims

1. a scanning unit that applies an optical coherence tomography (OCT) scan to the subject eye; a moving mechanism that moves at least a part of the scanning unit; a deviation measuring unit for measuring a deviation of the subject's eye relative to a predetermined reference position; a scan control unit that executes a first scan control to cause the scan unit to execute an OCT scan on a first region including a first part of the subject's eye, and a second scan control to cause the scan unit to execute an OCT scan on a second region including a second part different from the first part; an alignment control unit that executes a first alignment control for controlling the moving mechanism based on first deviation information of the subject's eye acquired by the deviation measurement unit before the first scan control, and a second alignment control for controlling the moving mechanism based on second deviation information of the subject's eye acquired by the deviation measurement unit before the second scan control; a distance calculation unit that calculates a distance between the first region and the second region based on first data acquired by the scanning unit under the first scan control and second data acquired by the scanning unit under the second scan control; Including, The scanning unit includes: an interference optical system including a measurement arm that guides a measurement light to the subject's eye and a reference arm that guides a reference light; an optical scanner that deflects the measurement light; Including, The scan control unit is Controlling the scanning unit to apply an A-scan to the subject's eye; comparing the intensity of the interference signal obtained from the A-scan with a predetermined threshold; When the intensity of the interference signal is less than the predetermined threshold value even after repeating the A scan a predetermined number of times, the scanning unit is controlled to apply a B scan to the subject's eye. comparing the intensity of the interference signal obtained from the B-scan to the predetermined threshold; When the intensity of the interference signal is less than the predetermined threshold value even after repeating the B scan a predetermined number of times, the scanning unit is controlled to apply a radial scan to the subject's eye. and performing control to limit a range of change in the orientation of the optical scanner of the scanning unit so that the first portion and / or the second portion are not outside the range of application of the OCT scan. An ophthalmic apparatus comprising:

2. the scanning unit includes an arm length changing unit provided in at least one of the measurement arm and the reference arm, the arm length changing unit changing an arm length under the control of the scan control unit; The distance calculation unit Calculating a difference between a first arm length applied in the first scan control and a second arm length applied in the second scan control; analyzing the first data to identify a first location corresponding to the first region; analyzing the second data to identify a second location corresponding to the second region; Calculating the distance based on the difference, the first position, and the second position 2. An ophthalmic apparatus according to claim 1 .

3. a scanning unit that applies an optical coherence tomography (OCT) scan to the subject eye; a deviation measuring unit for measuring a deviation of the subject's eye relative to a predetermined reference position; a scan control unit that executes a first scan control to cause the scan unit to execute an OCT scan on a first region including a first part of the subject's eye, and a second scan control to cause the scan unit to execute an OCT scan on a second region including a second part different from the first part; a distance calculation unit that calculates a distance between the first site and the second site based on at least one of first deviation information of the subject's eye acquired by the deviation measurement unit in response to the first scan control and second deviation information of the subject's eye acquired by the deviation measurement unit in response to the second scan control, first data acquired by the scan unit under the first scan control, and second data acquired by the scan unit under the second scan control; Including, The scanning unit includes: an interference optical system including a measurement arm that guides a measurement light to the subject's eye and a reference arm that guides a reference light; an optical scanner that deflects the measurement light; Including, The scan control unit is Controlling the scanning unit to apply an A-scan to the subject's eye; comparing the intensity of the interference signal obtained from the A-scan with a predetermined threshold; When the intensity of the interference signal is less than the predetermined threshold even after repeating the A-scan a predetermined number of times, the scanning unit is controlled to apply a B-scan to the subject's eye. comparing the intensity of the interference signal obtained from the B-scan to the predetermined threshold; When the intensity of the interference signal is less than the predetermined threshold value even after repeating the B scan a predetermined number of times, the scanning unit is controlled to apply a radial scan to the subject's eye. and performing control to limit a range of change in the orientation of the optical scanner of the scanning unit so that the first portion and / or the second portion are not outside the range of application of the OCT scan. An ophthalmic apparatus comprising:

4. the deviation measuring unit acquires one deviation information corresponding to one of the first scan control and the second scan control, and acquires another deviation information before the other scan control; a moving mechanism that moves at least a part of the scanning unit; an alignment control unit that executes alignment control for controlling the moving mechanism based on the other deviation information before the other scan control; Further comprising: The distance calculation unit calculates the distance based on the one deviation information, the first data, and the second data.

4. An ophthalmic apparatus according to claim 3.

5. the scanning unit includes an arm length changing unit provided in at least one of the measurement arm and the reference arm, the arm length changing unit changing an arm length under the control of the scan control unit; The distance calculation unit Calculating a difference between a first arm length applied in the first scan control and a second arm length applied in the second scan control; analyzing the first data to identify a first location corresponding to the first region; analyzing the second data to identify a second location corresponding to the second region; Calculating the distance based on the difference, the first position, the second position, and at least one of the first deviation information and the second deviation information.

5. An ophthalmic apparatus according to claim 3 or 4.

6. The distance calculation unit Calculating a provisional distance between the first portion and the second portion based on the difference, the first position, and the second position; The distance is calculated based on the provisional distance, at least one of the first deviation information and the second deviation information, and a corneal curvature radius of the subject's eye that has been acquired in advance.

6. An ophthalmic apparatus according to claim 5.

7. When the provisional distance is ALm, one of the first deviation information and the second deviation information is h, the corneal curvature radius is r, and the distance is AL, the distance calculation unit calculates the distance AL by an arithmetic formula AL=(r−r×cos(arcsin(h / r)))+ALm×cos(arcsin(h / ALm)).

7. An ophthalmic apparatus according to claim 6.

8. The scan control unit causes the scan unit to perform a plurality of OCT scans in at least one of the first scan control and the second scan control, The distance calculation unit Acquiring a single piece of data from the data group acquired by the multiple OCT scans; The distance is calculated using the single data. An ophthalmic apparatus according to any one of claims 1 to 7.

9. The distance calculation unit generates the single data by averaging the data group.

9. An ophthalmic apparatus according to claim 8.

10. The length of the scan line of the B scan is shorter than the length of a scan line of a standard B scan.

10. An ophthalmic apparatus according to claim 1, wherein the ophthalmic apparatus comprises:

11. The radial scan dimension is smaller than a standard radial scan dimension. An ophthalmic apparatus according to any one of claims 1 to 10.

12. As a range of change in the orientation of the optical scanner of the scanning unit, a range corresponding to the A scan, a range corresponding to the B scan, and a range corresponding to the radial scan are preset. An ophthalmic apparatus according to any one of claims 1 to 11.

13. The range corresponding to the A scan is set narrower than the range corresponding to the B scan and the range corresponding to the radial scan.

13. An ophthalmic apparatus according to claim 12.

14. A method for controlling an ophthalmic apparatus including a scanning unit that applies an optical coherence tomography (OCT) scan to a test eye, a moving mechanism that moves at least a part of the scanning unit, and a deviation measuring unit that measures deviation of the test eye relative to a predetermined reference position, wherein the scanning unit includes an interference optical system including a measurement arm that guides measurement light to the test eye and a reference arm that guides reference light, and an optical scanner that deflects the measurement light, a first alignment control step of controlling the moving mechanism based on first deviation information of the subject's eye acquired by the deviation measuring unit; a first scan control step of causing the scan unit to execute an OCT scan on a first region including a first portion of the subject's eye; a second alignment control step of controlling the moving mechanism based on second deviation information of the subject's eye acquired by the deviation measuring unit; a second scan control step of causing the scanning unit to perform an OCT scan on a second region including a second region different from the first region; a distance calculation step of calculating a distance between the first region and the second region based on first data acquired by the scanning unit in the first scan control step and second data acquired by the scanning unit in the second scan control step; Including, Furthermore, Controlling the scanning unit to apply an A-scan to the subject's eye; comparing an intensity of the interference signal obtained from the A-scan with a predetermined threshold; controlling the scanning unit to apply a B scan to the subject's eye when the intensity of the interference signal is less than the predetermined threshold even after repeating the A scan a predetermined number of times; comparing the intensity of the interference signal obtained in the B-scan with the predetermined threshold; controlling the scanning unit to apply a radial scan to the subject's eye when the intensity of the interference signal is less than the predetermined threshold value even after repeating the B scan a predetermined number of times; and executing control to limit a range of change in orientation of the optical scanner of the scanning unit so that the first region and / or the second region do not fall outside the range of application of the OCT scan. Includes 4. A method for controlling an ophthalmic apparatus comprising:

15. A method for controlling an ophthalmic apparatus including a scanning unit that applies an optical coherence tomography (OCT) scan to a test eye, and a deviation measuring unit that measures a deviation of the test eye relative to a predetermined reference position, the scanning unit including an interference optical system including a measurement arm that guides a measurement light to the test eye and a reference arm that guides a reference light, and an optical scanner that deflects the measurement light, comprising: a first scan control step of causing the scan unit to execute an OCT scan of a first region including a first portion of the subject's eye; a second scan control step of causing the scanning unit to perform an OCT scan on a second region including a second region different from the first region; a deviation measuring step of causing the deviation measuring unit to execute at least one of a step of acquiring first deviation information of the subject's eye in response to the first scan control and a step of acquiring second deviation information of the subject's eye in response to the second scan control; a distance calculation step of calculating a distance between the first portion and the second portion based on at least one of the first deviation information and the second deviation information acquired in the deviation measurement step, first data acquired by the scanning unit in the first scan control step, and second data acquired by the scanning unit in the second scan control step; Including, Furthermore, Controlling the scanning unit to apply an A-scan to the subject's eye; comparing an intensity of the interference signal obtained from the A-scan with a predetermined threshold; controlling the scanning unit to apply a B scan to the subject's eye when the intensity of the interference signal is less than the predetermined threshold even after repeating the A scan a predetermined number of times; comparing the intensity of the interference signal obtained in the B-scan with the predetermined threshold; controlling the scanning unit to apply a radial scan to the subject's eye when the intensity of the interference signal is less than the predetermined threshold value even after repeating the B scan a predetermined number of times; and executing control to limit a range of change in orientation of the optical scanner of the scanning unit so that the first region and / or the second region do not fall outside the range of application of the OCT scan. Includes 4. A method for controlling an ophthalmic apparatus comprising:

16. A program for causing a computer to execute the control method according to claim 14 or 15.

17. A non-transitory computer-readable recording medium having the program according to claim 16 recorded thereon.

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