Ophthalmic devices, their control methods, programs and storage media

Abstract

An ophthalmic device, its control method, and storage medium are disclosed. Highly reliable axial length measurement can be performed independently of the movement of the examined eye. An exemplary embodiment of the ophthalmic device performs a first optical coherence tomography (OCT) scan of a first region containing a first part of the examined eye and a second OCT scan of a second region containing a second part. The ophthalmic device aligns itself by acquiring first offset information of the examined eye before the first OCT scan and by acquiring second offset information before the second OCT scan. The ophthalmic device calculates the distance between the first and second parts of the examined eye based on the first data acquired through the first OCT scan and the second data acquired through the second OCT scan.

Description

[0001] This application is a divisional application of application number 201910866660.0 filed on September 12, 2019, entitled "Ophthalmic Device and Control Method, Program and Storage Medium Thereof". Technical Field

[0002] This invention relates to ophthalmic devices and their control methods, programs, and storage media. Background Technology

[0003] Ophthalmic devices capable of measuring axial length are known. 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 a useful intraocular parameter in selecting the power of intraocular lenses and confirming axial refractive errors before cataract surgery.

[0004] As mentioned earlier, axial length is defined as the distance between the corneal apex and the macula. Therefore, measuring axial length requires knowledge of both the corneal and retinal positions. In the invention disclosed in Patent Document 1, there is a time difference between the first measurement (anterior eye pattern OCT scan) used to determine the corneal position and the second measurement (posterior eye pattern OCT scan) used to determine the retinal position. Consequently, when the eye being examined moves between the first and second measurements, there is a possibility that the axial length cannot be accurately measured. In particular, movement of the eye in a direction orthogonal to the depth direction poses a risk of significantly reducing the reliability of the axial length measurement.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2016-19634 Summary of the Invention

[0008] The purpose of this invention is to provide a technique for measuring axial length with high reliability that can be performed regardless of the movement of the eye being examined.

[0009] A first exemplary embodiment provides an ophthalmic device comprising: a scanning unit, which performs optical coherence tomography (OCT) on the eye being examined. The device includes: a tomography scan unit; a moving mechanism for moving at least a portion of the scanning unit; an offset measuring unit for measuring the offset of the examined eye relative to a predetermined reference position; a scan control unit for executing a first scan control and a second scan control, wherein the first scan control causes the scanning unit to perform optical coherence tomography (OCT) scanning of a first region, the first region including a first portion of the examined eye, and the second scan control causes the scanning unit to perform OCT scanning of a second region, the second region including a second portion different from the first portion; an alignment control unit for executing a first alignment control and a second alignment control, wherein the first alignment control controls the moving mechanism based on first offset information of the examined eye obtained by the offset measuring unit prior to the first scan control, and the second alignment control controls the moving mechanism based on second offset information of the examined eye obtained by the offset measuring unit prior to the second scan control; and a distance calculation unit for calculating the distance between the first portion and the second portion based on first data obtained by the scanning unit under the first scan control and second data obtained by the scanning unit under the second scan control.

[0010] A second exemplary embodiment is an ophthalmic device according to the first embodiment, wherein the scanning unit includes: an interference optical system including a measuring arm for guiding measuring light to the eye being examined and a reference arm for guiding reference light; and an arm length changing unit disposed on at least one of the measuring arm and the reference arm, and changing the arm length under the control of the scanning control unit; the distance calculation unit calculates the difference between a first arm length applicable under the first scanning control and a second arm length applicable under the second scanning control, and parses the first data to determine a first position corresponding to the first part, parses the second data to determine a second position corresponding to the second part, and calculates the distance based on the difference, the first position, and the second position.

[0011] A third exemplary embodiment provides an ophthalmic device comprising: a scanning unit for performing optical coherence tomography (OCT) scanning on an eye under examination; an offset measuring unit for measuring the offset of the eye under examination relative to a predetermined reference position; a scanning control unit for executing a first scanning control and a second scanning control, the first scanning control causing the scanning unit to perform OCT scanning on a first region, the first region including a first portion of the eye under examination, and the second scanning control causing the scanning unit to perform OCT scanning on a second region, the second region including a second portion different from the first portion; and a distance calculation unit for calculating a distance between the first portion and the second portion based on at least one of first offset information and second offset information, first data, and second data, wherein the first offset information is offset information of the eye under examination obtained by the offset measuring unit corresponding to the first scanning control, the second offset information is offset information of the eye under examination obtained by the offset measuring unit corresponding to the second scanning control, the first data is data obtained by the scanning unit under the first scanning control, and the second data is data obtained by the scanning unit under the second scanning control.

[0012] A fourth exemplary embodiment is based on a third-party ophthalmic device, wherein the offset measuring unit acquires offset information corresponding to one of the first scan control and the second scan control, and acquires another offset information before and after the other scan control, the ophthalmic device further includes: a moving mechanism for moving at least a portion of the scanning unit; and an alignment control unit that performs alignment control of the moving mechanism based on the other offset information before the other scan control, the distance calculation unit calculating the distance based on the offset information, the first data, and the second data.

[0013] A fifth exemplary embodiment is an ophthalmic device according to a third or fourth embodiment, wherein the scanning unit includes: an interference optical system including a measuring arm for guiding measuring light to the eye being examined and a reference arm for guiding reference light; and an arm length changing unit disposed on at least one of the measuring arm and the reference arm, and changing the arm length under the control of the scanning control unit; the distance calculation unit calculates the difference between a first arm length applicable under the first scanning control and a second arm length applicable under the second scanning control, and parses the first data to determine a first position corresponding to the first part, parses the second data to determine a second position corresponding to the second part, and calculates the distance based on the difference, the first position, the second position, and at least one offset information of the first offset information and the second offset information.

[0014] A sixth exemplary embodiment is an ophthalmic device according to the fifth embodiment, wherein the distance calculation unit calculates a provisional distance between the first part and the second part based on the difference, the first position and the second position, and calculates the distance based on the provisional distance, at least one offset information of the first offset information and the second offset information, and the corneal curvature radius of the examined eye obtained in advance.

[0015] A seventh exemplary embodiment is an ophthalmic device according to the sixth embodiment, wherein when the provisional distance is set to ALm, one offset information of the first offset information and the second offset information is set to h, the corneal curvature radius is set to r, and the distance is set to AL, the distance calculation unit calculates the distance AL by the formula AL = (rr × cos(arcsin(h / r))) + ALm × cos(arcsin(h / ALm)).

[0016] An eighth embodiment of the exemplary implementation is an ophthalmic device according to any one of the first to seventh embodiments, wherein the scanning control unit causes the scanning unit to perform multiple optical coherence tomography scans under at least one of the first scanning control and the second scanning control, and the distance calculation unit obtains a single data from the data set obtained through the multiple optical coherence tomography scans and uses the single data to calculate the distance.

[0017] A ninth exemplary embodiment is an ophthalmic device according to the eighth embodiment, wherein the distance calculation unit generates the single data by performing an arithmetic average on the data set.

[0018] The tenth embodiment of the exemplary implementation is an ophthalmic device according to any one of the first to seventh embodiments, wherein the scanning control unit, under at least one of the first scanning control and the second scanning control, causes the scanning unit to perform optical coherence tomography (OCT) scanning of a three-dimensional region of the eye being examined, and the distance calculation unit analyzes the data obtained by the OCT scanning of the three-dimensional region, determines the feature position corresponding to the feature point of the eye being examined, and calculates the distance as the length of a line segment with the feature position as one end.

[0019] The eleventh exemplary embodiment is an ophthalmic device according to the tenth embodiment, wherein, under the first scan control, the scan control unit causes the scan unit to perform optical coherence tomography (OCT) scanning of a three-dimensional region including the corneal surface of the examined eye, and the distance calculation unit analyzes the data obtained by the OCT scanning of the three-dimensional region to determine the feature position corresponding to the corneal vertex.

[0020] The twelfth exemplary embodiment is an ophthalmic device according to the tenth or eleventh embodiment, wherein, under the second scan control, the scan control unit causes the scan unit to perform an optical coherence tomography scan of a three-dimensional region including the retinal surface of the examined eye, and the distance calculation unit analyzes the data obtained by the optical coherence tomography scan of the three-dimensional region to determine a feature position corresponding to the macula center.

[0021] The thirteenth embodiment is an ophthalmic device according to any one of the first to twelfth embodiments, wherein the offset measuring unit includes: a projection system that projects a light beam onto the anterior eye portion of the eye being examined; two or more imaging units that capture images of the anterior eye portion of the eye being examined from different directions; and an offset calculation unit that calculates the offset of the eye being examined based on the positions of the light beam images drawn in two or more anterior eye images acquired by the two or more imaging units.

[0022] The fourteenth embodiment is an ophthalmic device according to any one of the first to twelfth embodiments, wherein the offset measuring unit includes: a projection system for projecting a light beam obliquely toward the anterior eye portion of the examined eye; an image sensor for detecting reflected light beams from the anterior eye portion of the light beam; and an offset calculation unit for calculating the offset of the examined eye based on the detection position of the reflected light beam by the image sensor.

[0023] A fifteenth exemplary embodiment provides a control method for an ophthalmic device, the ophthalmic device comprising: a scanning unit for performing optical coherence tomography (OCT) scanning on an eye under examination; a moving mechanism for moving at least a portion of the scanning unit; and an offset measuring unit for measuring the offset of the eye under examination relative to a predetermined reference position, wherein the control method comprises: a first alignment control step for controlling the moving mechanism based on first offset information of the eye under examination obtained by the offset measuring unit; a first scan control step for causing the scanning unit to perform an OCT scan of a first region, the first region including a first portion of the eye under examination; a second alignment control step for controlling the moving mechanism based on second offset information of the eye under examination obtained by the offset measuring unit; a second scan control step for causing the scanning unit to perform an OCT scan of a second region, the second region including a second portion different from the first portion; and a distance calculation step for calculating the distance between the first portion and the second portion based on first data obtained by the scanning unit in the first scan control step and second data obtained by the scanning unit in the second scan control step.

[0024] A sixteenth exemplary embodiment provides a control method for an ophthalmic device, the ophthalmic device comprising: a scanning unit for performing optical coherence tomography (OCT) scanning on an eye under examination; and an offset measuring unit for measuring the offset of the eye under examination relative to a predetermined reference position, wherein the control method comprises: a first scanning control step of causing the scanning unit to perform an OCT scan of a first region, the first region including a first portion of the eye under examination; a second scanning control step of causing the scanning unit to perform an OCT scan of a second region, the second region including a second portion different from the first portion; an offset measuring step of causing the offset measuring unit to perform at least one of a step of acquiring first offset information of the eye under examination corresponding to the first scanning control and a step of acquiring second offset information of the eye under examination corresponding to the second scanning control; and a distance calculation step of calculating the distance between the first portion and the second portion based on at least one of the first offset information and the second offset information acquired by the offset measuring step, first data acquired by the scanning unit in the first scanning control step, and second data acquired by the scanning unit in the second scanning control step.

[0025] A seventeenth exemplary embodiment provides a program that causes a computer to execute the control method of the fifteenth or sixteenth embodiment.

[0026] An eighteenth exemplary embodiment provides a computer-readable non-volatile storage medium storing a program of the seventeenth embodiment.

[0027] According to the exemplary implementation, a highly reliable axial length measurement can be performed regardless of the movement of the eye being examined. Attached Figure Description

[0028] Figure 1 This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0029] Figure 2 This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0030] Figure 3A This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0031] Figure 3B This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0032] Figure 4A This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0033] Figure 4B This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0034] Figure 5 This is a simplified diagram illustrating an example of the operations that an ophthalmic device according to an exemplary embodiment can perform.

[0035] Figure 6 This is a flowchart illustrating an example of the operations that an ophthalmic device according to an exemplary embodiment can perform.

[0036] Figure 7 This is a simplified diagram illustrating an example of the structure of an ophthalmic device according to an exemplary embodiment.

[0037] Figure 8 This is a simplified diagram illustrating an example of the operations that an ophthalmic device according to an exemplary embodiment can perform.

[0038] Figure 9 This is a flowchart illustrating an example of the operations that an ophthalmic device according to an exemplary embodiment can perform.

[0039] Figure 10 This is a flowchart illustrating an example of the operations that an ophthalmic device according to an exemplary embodiment can perform.

[0040] Explanation of reference numerals in the attached figures

[0041] 1: Ophthalmic device; 50: Alignment optical system; 150: Moving mechanism; 210, 210A: Control unit; 300: Anterior eye camera; 410: Scanning unit; 420: Offset measurement unit; 430: Offset calculation unit; 440, 440A: Alignment control unit; 450, 450A: Scanning control unit. Detailed Implementation

[0042] The ophthalmic device of the embodiments, its control method, program, and storage medium are illustrated in detail with reference to the accompanying drawings. The ophthalmic device of the embodiments acquires data by applying optical coherence tomography (OCT) scans to the examined eye, thereby determining the distance between two different parts of the examined eye. Typically, the ophthalmic device of the embodiments applies OCT scans sequentially to the anterior and posterior portions of the examined eye, and determines the axial length from the obtained data.

[0043] The following exemplary disclosure describes an ophthalmic device that combines a spectral domain OCT and a fundus camera, but the implementation is not limited to this. The type of OCT is not limited to spectral domain OCT; for example, it may be a swept-frequency light source OCT.

[0044] Spectral domain OCT is a method that splits light from a low-coherence light source into a measurement light and a reference light, and then combines the returned light from the measurement light from the test object with the reference light to generate interference light. The spectral distribution of this interference light is detected by a beam splitter, and an image is formed by performing Fourier transform on the detected spectral distribution.

[0045] Frequency sweep light source OCT is a method that involves splitting light from a wavelength-tunable light source into a measurement light and a reference light, coinciding the return light from the measurement light from the test object with the reference light to generate interference light, detecting the interference light through a photodetector such as a balanced photodiode, and performing Fourier transform and other methods on the detection data collected by scanning the response wavelength and the measurement light to form an image.

[0046] Thus, spectral domain OCT is an OCT method that obtains spectral distribution through spatial segmentation, while swept-frequency light source OCT is an OCT method that obtains spectral distribution through time segmentation. Furthermore, the OCT methods that can be used in the implementation are not limited to these; implementations utilizing any different OCT method (e.g., time-domain OCT) can also be employed.

[0047] In this specification, unless specifically mentioned otherwise, no distinction is made between "image data" and the visualization information based thereon, i.e., "image". Furthermore, unless specifically mentioned otherwise, no distinction is made between the part or tissue of the eye being examined and the image that visualizes it.

[0048] <First Implementation>

[0049] In the first embodiment, after aligning the eye to be examined, an OCT scan of a first region of the eye is performed (first OCT scan). After realigning, an OCT scan of a second region is performed (second OCT scan). Based on first data obtained through the first OCT scan and second data obtained through the second OCT scan, the distance between a first portion contained in the first region and a second portion contained in the second region is calculated. Therefore, both the first and second OCT scans can be performed in a well-aligned state, enabling distance measurement with high reliability even if the eye to be examined moves between the first and second OCT scans. An example of this embodiment is disclosed below.

[0050] <structure>

[0051] Figure 1The exemplary ophthalmic device 1 shown includes a fundus camera unit 2, an OCT unit 100, and a computation control unit 200. The fundus camera unit 2 is equipped with an optical system and mechanism for acquiring a frontal image of the examined eye E, and an optical system and mechanism for performing OCT. The OCT unit 100 is equipped with an optical system and mechanism for performing OCT. The computation control unit 200 includes one or more processors configured to perform various processes (calculations, control, etc.). Furthermore, the ophthalmic device 1 includes two anterior eye cameras 300 for capturing images of the anterior eye from two different directions.

[0052] The fundus camera unit 2 includes a jaw support and a forehead pad for supporting the subject's face. The jaw support and forehead pad are equivalent to... Figure 4A as well as Figure 4B The support portion 340 is shown. A drive mechanism and an operational control circuit are housed in the base 310. An optical system is housed in a housing 320 mounted on the base 310. An objective lens 22 is housed in a lens receiving portion 330 that protrudes from the front of the housing 320.

[0053] Furthermore, the ophthalmic device 1 includes a lens unit for switching the site to which OCT is applied. Specifically, the ophthalmic device 1 includes an anterior ophthalmic OCT auxiliary lens 400 for applying OCT to the anterior eye. The anterior ophthalmic OCT auxiliary lens 400 may be configured in the same way as the optical unit disclosed in Japanese Patent Application Publication No. 2015-160103.

[0054] like Figure 1 As shown, the anterior ocular OCT auxiliary lens 400 can be positioned between the objective lens 22 and the examined eye E. When the anterior ocular OCT auxiliary lens 400 is positioned in the optical path, the ophthalmic device 1 can perform OCT scanning on the anterior eye. On the other hand, when the anterior ocular OCT auxiliary lens 400 is retracted from the optical path, the ophthalmic device 1 can perform OCT scanning on the posterior eye. The movement of the anterior ocular OCT auxiliary lens 400 can be performed manually or automatically.

[0055] In other embodiments, the auxiliary lens can be used to perform OCT scanning on the posterior eye when positioned in the optical path, and to perform OCT scanning on the anterior eye when the auxiliary lens is withdrawn from the optical path. Furthermore, the measurement site switched by the auxiliary lens is not limited to the posterior and anterior eyes, but can be any part of the eye. Moreover, the structure for switching the site for OCT scanning is not limited to this auxiliary lens; for example, a structure with a lens movable along the optical path or a structure with a lens that can be inserted and removed relative to the optical path can also be used.

[0056] In this embodiment, the "processor" is, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), or a programmable logic device (e.g., a SPLD (Simple Programmable Logic Device), a CPLD (Complex Programmable Logic Device), or a FPGA (Field Programmable Gate Array)). The processor implements the functionality of the embodiment by reading and executing a program stored in a storage circuit or storage device.

[0057] <Fundus Camera Unit 2>

[0058] The fundus camera unit 2 is equipped with an optical system for capturing the fundus image (Ef) of the examined eye (E). The acquired digital image of the fundus (Ef) (called a fundus image, fundus photograph, etc.) is generally a frontal image, such as an observation image or a photograph. The observation image is acquired by dynamic imaging using near-infrared light. The photographed image is a static image captured using a flash over the visible area.

[0059] The fundus camera unit 2 includes an illumination optics system 10 and an imaging optics system 30. The illumination optics system 10 illuminates the eye E to be examined. The imaging optics system 30 detects the return light of the illumination light illuminating the eye E. Measurement light from the OCT unit 100 is guided to the eye E through the optical path within the fundus camera unit 2. The return light of the measurement light projected onto the eye E (e.g., fundus Ef) is guided to the OCT unit 100 through the same optical path within the fundus camera unit 2.

[0060] The light emitted from the observation light source 11 of the illumination optical system 10 (observation illumination light) is reflected by the concave mirror 12, passes through the condenser lens 13, and becomes near-infrared light after passing through the visible light cutoff filter 14. Furthermore, the observation illumination light temporarily converges near the imaging light source 15, is reflected by the mirror 16, and is guided to the aperture mirror 21 via the relay lens system 17, relay lens 18, aperture 19, and relay lens system 20. Moreover, the observation illumination light is reflected at the periphery of the aperture mirror 21 (the area around the aperture), passes through the dichroic mirror 46, and is refracted by the objective lens 22 to illuminate the examined eye E (fundus Ef). The return light from the examined eye E is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the aperture formed in the central region of the aperture mirror 21, passes through the dichroic mirror 55, passes through the imaging focusing lens 31, and is reflected by the mirror 32. Furthermore, the returned light passes through the semi-transparent mirror 33A, is reflected by the dichroic mirror 33, and is imaged on the light-receiving surface of the image sensor 35 through the imaging lens 34. The image sensor 35 detects the returned light at a predetermined frame rate. In addition, the focus of the imaging optical system 30 can be adjusted to coincide with the fundus Ef or its vicinity and can also be adjusted to coincide with the anterior eye or its vicinity.

[0061] The light output from the imaging light source 15 (imaging illumination light) illuminates the fundus Ef through the same path as the observation illumination light. The return light from the imaging illumination light of the examined eye E is guided to the dichroic mirror 33 through the same path as the return light of the observation illumination light. After passing through the dichroic mirror 33, it is reflected by the reflecting mirror 36 and imaged on the light-receiving surface of the image sensor 38 through the imaging lens 37.

[0062] A liquid crystal display (LCD) 39 displays a fixed target (fixed target image). A portion of the light beam output from the LCD 39 is reflected by a semi-transparent mirror 33A, then by a mirror 32, and passes through the aperture of an aperture mirror 21 via a focusing lens 31 and a dichroic mirror 55. The light beam passing through the aperture of the aperture mirror 21 passes through a dichroic mirror 46, is refracted by an objective lens 22, and is projected onto the fundus Ef. Fixed targets are typically used for guiding and fixing the line of sight. The direction in which the line of sight of the examined eye E is guided (and fixed), i.e., the direction in which the examined eye E fixates, is called the fixation position.

[0063] By changing the display position of the fixed target image on the LCD 39 screen, the fixation position can be changed. Examples of fixation positions include those for acquiring an image centered on the macula, those for acquiring an image centered on the optic nerve head, those for acquiring an image centered on the area between the macula and the optic nerve head (center of the fundus), and those for acquiring an image of a region far from the macula (peripheral fundus).

[0064] A graphical user interface (GUI) can be provided to specify at least one of these typical fixation positions. Additionally, a GUI can be provided for manually moving the fixation position (the display position of the fixed target). Alternatively, a structure for automatically setting the fixation position can also be used.

[0065] The structure for displaying a fixed target capable of changing fixation position to the examined eye E is not limited to display instruments such as LCDs. For example, an instrument (fixation matrix) in which multiple light-emitting units (light-emitting diodes, etc.) are arranged in a matrix can be used instead of a display instrument. In this case, by selectively illuminating the multiple light-emitting units, the fixation position of the examined eye E based on the fixed target can be changed. As another example, a fixed target capable of changing fixation position can be generated by an instrument having one or more movable light-emitting units.

[0066] The alignment optical system 50 generates alignment marks for aligning the optical system of the examined eye E. Alignment light output from the light-emitting diode (LED) 51 passes through aperture 52, aperture 53, and relay lens 54, is reflected by dichroic mirror 55, passes through the aperture of the open-aperture mirror 21, passes through dichroic mirror 46, and is projected onto the examined eye E via objective lens 22. The return light from the examined eye E follows the same path as the return light of the observation illumination light and is guided to image sensor 35. Manual or automatic alignment can be performed based on the received image (alignment mark image).

[0067] Furthermore, the alignment method applicable to the implementation is not limited to the method using this alignment mark, and can be any known method such as the method using the front eye camera 300 (described later) or the method using light cutting (described later) which is configured to project light onto the cornea from the oblique direction and detect the corneal reflected light in the opposite direction.

[0068] The focusing optical system 60 generates a segmentation mark for focusing the examined eye E. Linked to the movement of the imaging focusing lens 31 along the optical path (imaging optical path) of the imaging optical system 30, the focusing optical system 60 moves along the optical path (illumination optical path) of the illumination optical system 10. The reflector 67 is inserted and removed relative to the illumination optical path. During focus adjustment, the reflective surface of the reflector 67 is tilted relative to the illumination optical path. The focused light output from the LED 61 passes through the relay lens 62, is split into two beams by the segmentation mark plate 63, passes through the two-aperture aperture 64, is reflected by the reflector 65, and is temporarily imaged and reflected by the condenser lens 66 on the reflective surface of the reflector 67. Furthermore, the focused light, via the relay lens 20, is reflected by the aperture reflector 21, passes through the dichroic mirror 46, and is projected onto the examined eye E by the objective lens 22. The return light (fundus reflection light, etc.) of the focused light from the examined eye E is guided to the image sensor 35 via the same path as the return light of the alignment light. It can perform manual or automatic focusing based on its received image (segmentation marker image).

[0069] A power-correcting lens 70 and a power-correcting lens 71 can be selectively inserted into the imaging optical path between the aperture reflector 21 and the dichroic mirror 55. The power-correcting lens 70 is a positive lens (convex lens) used to correct high-degree hyperopia. The power-correcting lens 71 is a negative lens (concave lens) used to correct high-degree myopia.

[0070] The dichroic mirror 46 combines the optical path for fundus imaging and the optical path for OCT (measuring arm). The dichroic mirror 46 reflects the wavelength light used for OCT, allowing the light used for fundus imaging to pass through. On the measuring arm, from the OCT unit 100 side, a collimating lens unit 40, a Littoral mirror 41, a dispersion compensation component 42, an OCT focusing lens 43, a light scanner 44, and a relay lens 45 are arranged sequentially.

[0071] The Littoral mirror 41 can move along the optical path of the measurement light LS incident on it, thereby changing the length of the measurement arm. The change in the measurement arm length can be used, for example, for optical path length correction in response to the axial length of the eye, interference state adjustment, etc.

[0072] The dispersion compensation component 42, together with the dispersion compensation component 113 (described later) disposed on the reference arm, serves to match the dispersion characteristics of the measurement light LS and the dispersion characteristics of the reference light LR.

[0073] The OCT focusing lens 43 moves along the measurement arm to adjust the focus of the measurement arm. Furthermore, the movement of the imaging focusing lens 31, the focusing optical system 60, and the OCT focusing lens 43 can be controlled in a series of steps.

[0074] The optical scanner 44 is substantially optically conjugate to the pupil of the eye being examined, E. The optical scanner 44 deflects the measurement light LS guided by the measurement arm. The optical scanner 44 is, for example, a current scanner capable of two-dimensional scanning. Typically, the optical scanner 44 includes a one-dimensional scan (x-scan) for deflecting the measurement light in the ±x direction and a one-dimensional scan (y-scan) for deflecting the measurement light in the ±y direction. In this case, for example, either one of these one-dimensional scans is optically conjugate to the pupil, or the optically conjugate position to the pupil is positioned between these one-dimensional scans.

[0075] <OCT Unit 100>

[0076] exist Figure 2The exemplary OCT unit 100 shown is equipped 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 wavelength-tunable light source into a measurement light and a reference light, such that the return light of the measurement light projected onto the examined eye E coincides with the reference light passing through the reference light path, generating interference light. The spectral distribution of the interference light generated by the interference optical system is detected using a beam splitter. The data (detection signal) obtained from the detection of the spectral distribution of the interference light is sent to the computation control unit 200.

[0077] The light source unit 101 outputs wide-bandwidth, low-coherence light L0. The low-coherence light L0 may include wavelengths in the near-infrared region (around 800nm–900nm) with a temporal coherence length of approximately tens of micrometers. Alternatively, the low-coherence light L0 may also be near-infrared light with a center wavelength indistinguishable to the human eye, such as around 1040–1060nm. The light source unit 101 includes light output instruments such as superluminescent diodes (SLDs), LEDs, and semiconductor optical amplifiers (SOAs).

[0078] Furthermore, in the case of using a swept-frequency light source OCT, the light source unit includes a near-infrared wavelength tunable laser that causes the wavelength of the emitted light to change rapidly.

[0079] The low-coherence light L0 output from the light source unit 101 is guided by the optical fiber 102 to the polarization controller 103, where its polarization state is adjusted. The polarization-adjusted light L0 is then guided by the optical fiber 104 to the optical fiber coupler 105, where it is split into a measurement light LS and a reference light LR. The optical path guiding the measurement light LS is called the sample arm, and the optical path guiding the reference light LR is called the reference arm.

[0080] The reference light LR generated by the fiber coupler 105 is guided by the fiber optic cable 110 to the collimator 111 and converted into a parallel beam. It is then guided to the Littrow mirror 114 via the optical path length correction member 112 and the dispersion compensation member 113. The optical path length correction member 112 matches the optical path length of the reference light LR and the measurement light LS. The dispersion compensation member 113, together with the dispersion compensation member 42 disposed on the measurement arm, matches the dispersion characteristics between the reference light LR and the measurement light LS. The Littrow mirror 114 can move along the optical path of the incident reference light LR, thereby changing the length of the reference arm. This change in reference arm length can be used, for example, for optical path length correction in response to eye axis length, and for adjusting the interference state.

[0081] The reference light LR, passing through the Littoral mirror 114, is converted from a parallel beam to a converging beam by the collimator 116 via the dispersion compensation component 113 and the optical path length correction component 112, and then incident on the optical fiber 117. The reference light LR incident on the optical fiber 117 is guided by the polarization controller 118 and its polarization state is adjusted. It passes through the optical fiber 119 and is guided to the attenuator 120 where its light intensity is adjusted. It then passes through the optical fiber 121 and is guided to the optical fiber coupler 122.

[0082] On the other hand, the measurement light LS generated by the fiber optic coupler 105 is guided through the fiber optic cable 127 to the collimating lens unit 40 and converted into a parallel beam. It then passes through the Littoral mirror 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, refracted by the objective lens 22, and projected onto the examined eye E. The measurement light LS is scattered and reflected at various depth positions of the examined eye E. The return light from the examined eye E of the measurement light LS travels in reverse on the measurement arm and is guided to the fiber optic coupler 105, reaching the fiber optic coupler 122 via the fiber optic cable 128.

[0083] The fiber coupler 122 causes the measurement light LS incident via fiber 128 and the reference light LR incident via fiber 121 to coincide, thereby generating the interference light LC.

[0084] The interference light LC generated by fiber coupler 122 is guided to beam splitter 130 via fiber optic cable 129. Beam splitter 130, for example, converts the incident interference light LC into a parallel beam through a collimating lens, and then decomposes the parallel beam LC into spectral components through a diffraction grating. The spectral components decomposed by the diffraction grating are projected onto an image sensor through lens 114. This image sensor, for example, is a line sensor, which detects multiple spectral components of the interference light LC to generate an electrical signal (detection signal). The generated detection signal is sent to arithmetic control unit 200.

[0085] Furthermore, in the case of OCT using a swept-frequency light source, the interference light generated by coinciding the measurement light and the reference light is branched at a predetermined branching ratio (e.g., 1:1) to generate a pair of interference lights, which are then 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 lights respectively, and outputs the difference between the pair of detection signals obtained through it. The photodetector transmits this output (the detection signal, such as the difference signal) to a data acquisition system (DAQ). A clock is supplied from the light source unit to the data acquisition system. The clock is generated in the light source unit in sync with the output timing of each wavelength scanned by the wavelength-tunable light source within a predetermined wavelength range. The light source unit, for example, branches the light of each output wavelength to generate two branched lights, causes one of these branched lights to lag, and combines these branched lights, detects the obtained combined light, and generates a clock based on its detection signal. The data acquisition system performs sampling of the detection signal (difference signal) input from the photodetector according to the clock. The data obtained through this sampling is used for processing such as image construction.

[0086] Figure 1 as well as Figure 2 The ophthalmic apparatus 1 shown includes both a component for changing the length of the measuring arm (e.g., a Littertow mirror 41) and a component for changing the length of the reference arm (e.g., a Littertow mirror 114 or a reference mirror), but only one of these components may be provided. The position of the coherence gate is changed by altering the difference between the measuring arm length and the reference arm length (optical path length difference), but the component for changing the optical path length difference is not limited to the component illustrated in this embodiment, and any component (optical component, mechanism, etc.) may be used.

[0087] <Arithmetic Control Unit 200>

[0088] The computational control unit 200 controls various parts of the ophthalmic device 1. Furthermore, the computational control unit 200 performs various computational processes. For example, the computational control unit 200 performs signal processing such as Fourier transform on the spectral distribution acquired by the beam splitter 130 to form the reflection intensity status of each A-line. Moreover, the computational control unit 200 forms image data by imagerizing the reflection intensity status of each A-line. The computational processing for this purpose is the same as that of conventional spectral domain OCT.

[0089] The arithmetic control unit 200 may include, for example, a processor, RAM (Random Access Memory), ROM (Read Only Memory), a hard disk drive, a communication interface, etc. Various computer programs are stored in the storage device such as the hard disk drive. The arithmetic control unit 200 may also include operating instruments, input instruments, display instruments, etc.

[0090] <User Interface 240>

[0091] The user interface 240 includes a display unit 241 and an operation unit 242. The display unit 241 includes a display device 3. The operation unit 242 includes various operating instruments and input instruments. The user interface 240 may also include an instrument that integrates display and operation functions, such as a touch screen. Embodiments that do not include at least a portion of the user interface 240 may also be constructed. For example, the display instrument may be an external device connected to an ophthalmic imaging device.

[0092] <Front-Eye Camera 300>

[0093] The anterior eye camera 300 captures images of the anterior eye of the examined eye E from two or more different directions. The anterior eye camera 300 includes an imaging device 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 surface of the fundus camera unit 2 (see reference). Figure 4A The front-eye camera 300A and front-eye camera 300B are shown. Figure 1 as well as Figure 4A As shown, the front eye camera 300A and the front eye camera 300B are positioned away from the optical path passing through the objective lens 22. Hereinafter, one or both of the front eye camera 300A and the front eye camera 300B will sometimes be referred to by reference numeral 300. Additionally, a front eye camera that can be used in place of the front eye camera 300A and the front eye camera 300B will sometimes be referred to by reference numeral 300.

[0094] In this embodiment, two front-eye cameras 300A and a front-eye camera 300B are provided, but the number of front-eye cameras 300 can be any number of two or more. Considering the computational processing described later, it is sufficient to be able to capture images of the front-eye structure from two different directions (but it is not limited to this). Alternatively, movable front-eye cameras 300 can be provided to sequentially capture images of the front eye from two or more different positions.

[0095] In this embodiment, a front-eye camera 300 is provided separately from the illumination optical system 10 and the imaging optical system 30. However, for example, the imaging optical system 300 can also be used to capture images of the front eye. That is, one of the two or more front-eye cameras 300 can be the imaging optical system 30. In this embodiment, the front-eye camera 300 can capture images of the front eye from two (or more) different directions.

[0096] A structure for illuminating the anterior eye may also be provided. This anterior eye illumination component may include, for example, more than one light source. Typically, at least one light source (e.g., an infrared light source) may be positioned near each of two or more anterior eye cameras 300.

[0097] When two or more anterior eye cameras 300 are set up, the anterior eye can be photographed substantially simultaneously from two or more different directions. "Substantially simultaneously" means that, in addition to the two or more anterior eye cameras shooting at the same time, it also allows for situations where the left and right shooting timings are different due to eye movement, which can be ignored. Through this substantially simultaneous shooting, images of the examined eye E in substantially the same position and orientation can be obtained by two or more anterior eye cameras.

[0098] Shooting using two or more front-eye cameras can be either dynamic or static. In dynamic shooting, by controlling the timing of the start of the shot, or by controlling the frame rate and the timing of each frame, it is possible to achieve virtually simultaneous front-eye shooting, as described above. Similarly, in static shooting, by controlling the timing of the shot, it is possible to achieve virtually simultaneous front-eye shooting.

[0099] <Control System>

[0100] Figure 3A as well as Figure 3B An example of the structure of the control system (processing system) of the ophthalmic device 1 is shown. The control unit 210, the image forming unit 220, and the data processing unit 230 are provided, for example, in the arithmetic control unit 200.

[0101] <Control Unit 210>

[0102] The control unit 210 includes a processor that controls various parts of the ophthalmic device 1. The control unit 210 includes a main control unit 211 and a storage unit 212.

[0103] <Main Control Unit 211>

[0104] The main control unit 211 includes a processor that controls the various components of the ophthalmic device 1 (including...). Figures 1 to 3B (The elements shown). The main control unit 211 is implemented through the cooperation of hardware including circuitry and control software.

[0105] The imaging focusing lens 31, configured in the imaging optical path, and the focusing optical system 60, configured in the illumination optical path, move integrally or in conjunction with an imaging focusing drive unit (not shown) under the control of the main control unit 211. The Littoral mirror 41, mounted on the measurement arm, moves via a Littoral mirror (RR) drive unit 41A under the control of the main control unit 211. The OCT focusing lens 43, mounted on the measurement arm, moves via an OCT focusing drive unit 43A under the control of the main control unit 211. Furthermore, the movement of the OCT focusing lens 43 can be performed in conjunction with the movement of the imaging focusing lens 31 and the focusing optical system 60. The Littoral mirror 114, mounted on the reference arm, moves via a Littoral mirror (RR) drive unit 114A under the control of the main control unit 211. The mechanisms illustrated here typically include actuators such as pulse motors that operate under the control of the main control unit 211. The optical scanner 44, mounted on the measurement arm, operates under the control of the main control unit 211. Furthermore, the main control unit 211 can control any component included in the ophthalmic device 1, such as the polarization controller 103, polarization controller 118, attenuator 120, various light sources, various optical components, various instruments, and various mechanisms. In addition, the main control unit 211 can control any peripheral instruments (devices, equipment, instruments, etc.) connected to the ophthalmic device 1, and control any devices, equipment, instruments, etc. accessible through the ophthalmic device 1.

[0106] The moving mechanism 150, for example, moves the fundus camera unit 2 at least in three dimensions. In a typical example, the moving mechanism 150 includes an x-stage capable of moving in the ±x direction (left-right direction), an x-moving mechanism for moving the x-stage, a y-stage capable of moving in the ±y direction (up-down direction), a y-moving mechanism for moving the y-stage, a z-stage capable of moving in the ±z direction (depth direction), and a z-moving mechanism for moving the z-stage. These moving mechanisms each include actuators such as pulse motors that operate under the control of the main control unit 211.

[0107] <Storage Unit 212>

[0108] Storage unit 212 stores various types of data. Data stored in storage unit 212 includes, for example, image data containing OCT images, fundus image data, and information about the examined eye. Information about the examined eye includes patient information such as patient ID and name, identification information for the left / right eye, and electronic medical record information.

[0109] <Image forming unit 220>

[0110] The image forming unit 220 forms OCT image data based on data acquired by the beam splitter 130. The image forming unit 220 includes a processor. The image forming unit 220 is implemented through the cooperation of hardware including circuitry and image forming software.

[0111] The image forming unit 220 forms cross-sectional image data based on the data acquired by the beam splitter 130. This image forming process is the same as conventional spectral domain OCT, including signal processing such as sampling (A / D conversion), noise removal (noise reduction), filtering, and high-speed Fourier transform (FFT).

[0112] The image data formed by the image forming unit 220 is a set of image data (a set of A-scan image data) formed by imagerizing the reflection intensity of multiple A-lines (scan lines along the z-direction) arranged in the area to be scanned by OCT.

[0113] Image data formed by the image forming unit 220 may be, for example, one or more B-scan image data, or stacked data formed by embedding multiple B-scan image data into a single three-dimensional coordinate system. The image forming unit 220 may also perform voxelization processing on the stacked data to construct volume data (voxel data). Stacked data and volume data are typical examples of three-dimensional image data expressed through a three-dimensional coordinate system.

[0114] The image forming unit 220 is capable of processing 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 projection (MIP), minimum projection (MinIP), surface rendering, and multi-plane reconstruction (MPR). Furthermore, the image forming unit 220 can project the three-dimensional image data in the z-direction (A-line direction, depth direction) to construct projection data. Additionally, the image forming unit 220 can project a portion of the three-dimensional image data (three-dimensional local image data) in the z-direction to construct a shadow image. Moreover, the three-dimensional local image data can be segmented and defined, for example, on the three-dimensional image data.

[0115] <Data Processing Department 230>

[0116] The data processing unit 230 performs various data processing operations. For example, the data processing unit 230 can perform image processing and analysis on OCT image data, and on observed image data or captured image data. The data processing unit 230 includes, for example, at least one processor and a dedicated circuit board. The data processing unit 230 is implemented through the cooperation of hardware including circuitry and data processing software.

[0117] Next, explain the process. Figures 1 to 3A The ophthalmic device 1 is implemented using the required components (hardware components and software components). An example of the functional structure of the ophthalmic device 1 is shown in... Figure 3B As shown. Furthermore... Figure 3B The elements shown are related to Figure 3A The same elements are shown with the same reference numerals in the accompanying drawings.

[0118] <Scanning Unit 410>

[0119] The scanning unit 410 acquires data by performing an OCT scan on the eye being examined, E. The data acquired by the scanning unit 410 may be, for example, first data acquired by the beam splitter 130, second data (sampling data, reflection intensity status, image data, etc.) generated from the first data by the image forming unit 220, or data (image data, etc.) generated from the second data by the data processing unit 230, etc. Thus, the scanning unit 410 may include at least the beam splitter 130, and may also include at least a portion of the image forming unit 220, and may further include at least a portion of the data processing unit 230.

[0120] The scanning unit 410 includes an interferometric optical system, which includes the aforementioned measuring arm for guiding the measuring light LS to the eye under examination E and the aforementioned reference arm for guiding the reference light LS. As mentioned above, the measuring arm is equipped with an OCT focusing lens 43, a light scanner 44, etc., and the reference arm is equipped with a polarization controller 118, an attenuator 120, etc. The interferometric optical system includes a beam splitter 130.

[0121] Furthermore, the scanning unit 410 includes an arm length changing unit disposed on at least one of the measuring arm and the reference arm. The arm length changing unit includes either or both of the following combinations: a combination of a Littoral mirror 41 and a Littoral mirror drive unit 41A, and a combination of a Littoral mirror 114 and a Littoral mirror drive unit 114A. The arm length changing unit changes the arm length under the control of the scanning control unit 450, described later. More specifically, when the arm length changing unit includes a combination of a Littoral mirror 41 and a Littoral mirror drive unit 41A, the arm length changing unit is capable of changing the measuring arm length. Additionally, when the arm length changing unit includes a combination of a Littoral mirror 114 and a Littoral mirror drive unit 114A, the arm length changing unit is capable of changing the reference arm length.

[0122] <Offset Measurement Unit 420>

[0123] The offset measuring unit 420 measures the offset of the examined eye E relative to a preset reference position. The alignment control unit 440, described later, performs alignment control based on the offset measurement results (offset information) obtained by the offset measuring unit 420. The alignment control includes control of the moving mechanism 150 based on the offset information. For example, the alignment control is a process of moving the optical system (at least the measuring arm) in a manner that eliminates the offset obtained by the offset measuring unit 420.

[0124] The offset of the examined eye E from the reference position is a relative position with respect to the reference position, typically a vector (direction and magnitude).

[0125] The reference position is set, for example, based on the optical system of ophthalmic device 1. Typical reference positions include reference positions in the x-direction, y-direction, and z-direction. That is, typical reference positions are three-dimensional positions. Reference positions are not limited to three-dimensional positions; they can also be two-dimensional or one-dimensional positions.

[0126] As mentioned above, the offset of the examined eye E from the reference position is a relative position. Therefore, when the reference position is set based on the optical system of the ophthalmic device 1, the offset of the examined eye E from the optical system of the ophthalmic device 1 is synonymous with the offset of the optical system from the examined eye E. Furthermore, when the reference position is not set based on the optical system of the ophthalmic device 1, the offset of the examined eye E from the optical system of the ophthalmic device 1 with respect to that reference position is also synonymous with the offset of the optical system from the examined eye E.

[0127] The reference positions in the x-direction and y-direction (xy reference positions) are, for example, the positions of the optical axis (optical axis of objective lens 22) of the ophthalmic device 1. In this case, the offset measuring unit 420 can determine the offset of the examined eye E from the optical axis position in the xy plane (xy coordinate system).

[0128] On the other hand, the reference position in the z direction (z reference position) is, for example, a position located at a predetermined distance from the optical system (in front of the objective lens 22) of the ophthalmic device 1 in the +z direction. In this case, the offset measuring unit 420 can calculate the offset of the examined eye E from the z reference position in the z direction (z coordinate).

[0129] The predetermined distance used to define the z-reference position is, for example, a pre-set running distance or a distance to which a predetermined value is added. Examples of such predetermined values ​​include half the radius of corneal curvature and the distance between the cornea and the pupil.

[0130] When alignment is performed using the corneal surface as a reference, the running distance can be used as the predetermined distance mentioned above. When alignment is performed using a bright spot formed in the anterior eye (Pulkiner phenomenon) as a reference, the distance obtained by adding half the value of the corneal radius of curvature to the running distance can be used as the predetermined distance mentioned above. When alignment is performed using the pupil as a reference, the distance obtained by adding the value of the corneal-pupil distance to the running distance can be used as the predetermined distance mentioned above. Furthermore, the corneal radius of curvature and the corneal-pupil distance can be values ​​obtained by actually measuring the tested eye E.

[0131] As an example of a three-dimensional reference position, there exists a position on the optical axis of the ophthalmic device 1 that is separated from the aforementioned predetermined distance from the front of the objective lens 22 in the +z direction.

[0132] To determine the offset of the examined eye E from the reference position, the position of the examined eye E needs to be defined. The position of the examined eye E can be defined, for example, as the location of the bright spot formed in the anterior eye, the location of the pupil center (pupil centroid), or the location of the corneal apex.

[0133] When the position of the eye to be examined, E, is defined as the bright spot position, the offset measuring unit 420 can, for example, determine the bright spot position from two anterior eye images acquired by two anterior eye cameras 300 and calculate the offset of the eye to be examined, E, from the reference position, according to the processing method disclosed by the applicant in Japanese Patent Application Publication No. 2017-074115 and Japanese Patent Application Publication No. 2017-225638.

[0134] When the position of the eye being examined, E, is defined as the pupil center position, the offset measuring unit 420 can, for example, determine the pupil center position from two anterior eye images acquired by two anterior eye cameras 300 and calculate the offset of the eye being examined, E, from the reference position, according to the processing method disclosed by the applicant in Japanese Patent Application Publication No. 2013-248376 and Japanese Patent Application Publication No. 2017-225638.

[0135] When the position of the eye being examined, E, is defined as the corneal apex position, the offset measuring unit 420 can, for example, determine the corneal apex position from two anterior eye images acquired by two anterior eye cameras 300 and calculate the offset of the eye being examined, E, from the reference position, according to the processing method disclosed by the applicant in Japanese Patent Application Publication No. 2017-225638.

[0136] Furthermore, the definitions of the reference position, the position of the examined eye E, the processing method for determining the position of the examined eye E, and the calculation method for the offset of the examined eye E from the reference position are not limited to the examples mentioned above and can be arbitrary. For example, an alignment method based on the positional relationship of two bright spots or an alignment method utilizing optical sectioning can be applied.

[0137] Figure 3B The displacement measurement unit 420 shown is an example applicable when the position of the examined eye E is defined as the bright spot position. The displacement measurement unit 420 in this example includes an alignment optics system 50, two anterior eye cameras 300, and a displacement calculation unit 430. The displacement calculation unit 430 is contained within the data processing unit 230 and is implemented through the cooperation of hardware including circuitry and displacement calculation software.

[0138] As mentioned above, the alignment optical system 50 projects an alignment mark onto the anterior eye of the examined eye E. That is, the alignment optical system 50 is equivalent to a projection system that projects a light beam onto the anterior eye of the examined eye E.

[0139] When the beam is projected through the alignment optical system 50, the two anterior eye cameras 300 capture images of the anterior eye of the eye being examined, E, from different directions. This results in two anterior eye images corresponding to these different directions. In each of these anterior eye images, a bright spot is drawn representing the image of the beam projected through the alignment optical system 50, serving as an alignment marker.

[0140] The offset calculation unit 430 calculates the offset of the examined eye E from a predetermined reference position based on the positions of two bright spots drawn in each of the two anterior eye images acquired by the two anterior eye cameras 300.

[0141] Similar to the processing methods disclosed in Japanese Patent Application Publication No. 2017-074115 and Japanese Patent Application Publication No. 2017-225638, the offset calculation unit 430 analyzes two anterior eye images to detect bright spots, and determines the position of the examined eye E based on the two bright spots detected from the two anterior eye images.

[0142] For example, the offset calculation unit 430 can calculate the distance between the examined eye E and the ophthalmic device 1 (objective lens 22) in the direction (z direction) along the optical axis of the ophthalmic device 1 based on the relative positions of the two bright spots detected from the 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 examined eye E and the ophthalmic device 1 in the z direction is consistent with the running distance.

[0143] Furthermore, the offset calculation unit 430 can calculate the offset between the examined eye E and the ophthalmic device 1 in a direction orthogonal 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 offset, the alignment control unit 440 can control the movement mechanism 150 to make the optical axis of the ophthalmic device 1 coincide with the axis of the examined eye E.

[0144] In addition, when a bright spot cannot be detected from either or both of the two anterior eye images, other alignment methods can be used (e.g., alignment with the pupil center as a reference).

[0145] As described in detail below, the ophthalmic device 1 performs a first OCT scan on a first region (e.g., the anterior ocular region) containing a first part (e.g., the corneal surface) of the examined eye E, and a second OCT scan on a second region (e.g., the posterior ocular region) containing a second part (e.g., the retinal surface). The offset measurement unit 420 performs a first offset measurement to acquire first offset information before the first OCT scan and performs a second offset measurement to acquire second offset information before the second OCT scan. Typically, the first offset measurement is performed just before the first OCT scan, and the second offset measurement is performed just before the second OCT scan.

[0146] Furthermore, the execution order of the first OCT scan and the second OCT scan is arbitrary; the second OCT scan can be performed after the first OCT scan, or the first OCT scan can be performed after the second OCT scan.

[0147] Alignment Control Unit 440

[0148] The alignment control unit 440 performs a first alignment control of the moving mechanism 150 based on the first offset information obtained by the offset measuring unit 420 before the first OCT scan, and a second alignment control of the moving mechanism 150 based on the second offset information obtained by the offset measuring unit 420 before the second OCT scan.

[0149] For example, the alignment control unit 440 performs first alignment control in a manner that eliminates the offset indicated by the first offset information and performs second alignment control in a manner that eliminates the offset indicated by the second offset information, using the same principles as the alignment methods disclosed in Japanese Patent Application Publication No. 2017-074115, Japanese Patent Application Publication No. 2017-225638, or Japanese Patent Application Publication No. 2013-248376.

[0150] The alignment control unit 440 is included in the control unit 210 and is implemented through the cooperation of hardware including circuitry and alignment control software.

[0151] <Scanning Control Unit 450>

[0152] The scan control unit 450 performs control for the aforementioned first OCT scan and second OCT scan. That is, the scan control unit 450 performs first scan control to cause the scan unit 410 to perform a first OCT scan on a first region (e.g., the anterior eye region) including a first part (e.g., the corneal surface) of the examined eye E, and second scan control to cause the scan unit 410 to perform a second OCT scan on a second region (e.g., the posterior eye region) including a second part (e.g., the retinal surface).

[0153] The first and second scan controls each include, for example, control of the arm length changing unit (one or both of the Littoral mirror drive unit 41A and the Littoral mirror drive unit 114A), control of the light source unit 101, and control of the optical scanner 44. Furthermore, the first and second scan controls may each include control of the polarization controller 103, control of the polarization controller 118, control of the attenuator 120, control of the OCT focusing drive unit 43A, etc. Examples of the first and second scan controls will be described later.

[0154] The scanning control unit 450 is included in the control unit 210 and is implemented through the cooperation of hardware including circuitry and scanning control software.

[0155] <Distance Calculation Unit 460>

[0156] The distance calculation unit 460 calculates the distance between a first part included within the applicable range of the first OCT scan and a second part included within the applicable range of the second OCT scan based on first data acquired through the first OCT scan and second data acquired through the second OCT scan. That is, the distance calculation unit 460 calculates the distance between the first part and the second part of the examined eye E based on the first data acquired by the scanning unit 410 under first scan control and the second data acquired by the scanning unit 410 under second scan control.

[0157] For example, when the first region is the corneal surface and the second region is the retinal surface, that is, when a first OCT scan is performed on the anterior eye region including the corneal surface and a second OCT scan is performed on 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 calculates the distance between the corneal apex and the center of the macula (fovea), i.e., the axial length.

[0158] For example, the distance calculation unit 460 performs distance calculation through a series of processes (first process to fourth process) as shown below. Here, the execution order of the first process to the third process is arbitrary, and any two or more of these processes can be executed in parallel.

[0159] In the first process, the distance calculation unit 460 calculates the difference between the first arm length applicable under the first scan control and the second arm length applicable under the second scan control. The first arm length and the second arm length are obtained, for example, from the scan control unit 450 that performs the first scan control and the second scan control. Alternatively, either or both of the first arm length and the second arm length can be detected by a component that detects the arm length, such as a position sensor that detects the position of either or both of the Littoral reflector 41 and the Littoral reflector 114.

[0160] In the second processing, the distance calculation unit 460 analyzes the first data acquired by the scanning unit 410 under the first scan control to determine the position (first position) in the first data corresponding to the first part of the examined eye E. For example, if the first part 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 determine the first position corresponding to the corneal surface (typically, the corneal apex) of the examined eye E. Typically, the first position is the signal position in the reflection intensity status generated from the detection signal acquired by the first OCT scan, or the pixel position in the A-scan image data obtained by imagerizing the reflection intensity status.

[0161] In the third processing, the distance calculation unit 460 analyzes the second data acquired by the scanning unit 410 under the second scan control to determine the position (second position) in the second data corresponding to the second part of the examined eye E. For example, if the second part is the retinal surface, the distance calculation unit 460 analyzes the second data acquired from the second OCT scan of the posterior eye region to determine the second position corresponding to the retinal surface (typically, the macula center) of the examined eye E. Typically, the second position is the signal position in the reflection intensity status generated from the detection signal acquired by the second OCT scan, or the pixel position in the A-scan image data obtained by imagerizing the reflection intensity status.

[0162] In the fourth process, the distance calculation unit 460 calculates the distance between the first part and the second part based on the arm length difference calculated in the first process, the first position determined in the second process, and the second position determined in the third process.

[0163] Typically, in the fourth process, the distance calculation unit 460 calculates the axial length of the examined eye E based on the arm length difference calculated in the first process, the corneal apex position determined in the second process, and the macular center position determined in the third process. A brief summary of this calculation process is as follows: Figure 5 As shown in the image.

[0164] The corneal apex of the examined eye E is indicated by reference numeral C, and the macula center is indicated by reference numeral M. Reference numerals A1 and A2 represent 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 each A-scans. Figure 5 This indicates that the first OCT scan A1 and the second OCT scan A2 were performed under good alignment conditions. That is, Figure 5 The illustration shows the case where a first OCT scan A1 is performed in a manner that passes through the corneal apex C and a second OCT scan A2 is performed in a manner that passes through the macula center M.

[0165] The reflection intensity obtained by the first OCT scan A1 is denoted by reference numeral P1, and the reflection intensity obtained by the second OCT scan A2 is denoted by reference numeral P2. The z-axis of the first reflection intensity P1 is denoted by "z1", and the z-axis of the second reflection intensity P2 is denoted by "z2".

[0166] The first OCT scan A1 of the anterior eye region is performed with the coherence gate configured at any position in the anterior eye. For example, the coherence gate is configured at a position halfway away from the corneal curvature radius (the bright spot formation position) in the +z direction from the corneal apex C. The reference numeral z1(0) indicates the coherence gate position applicable in the first OCT scan A1 in this example.

[0167] On the other hand, the second OCT scan A2 of the posterior eye region is performed with the coherence gate configured at any position in the posterior eye. For example, the coherence gate is configured in the vitreous body close to the retinal surface. The reference numeral z2(0) indicates the coherence gate position applicable in the second OCT scan A2 in this example.

[0168] The distance calculation unit 460 calculates the difference between the coherence gate position z1(0) applicable in the first OCT scan A1 and the coherence gate position z2(0) applicable in the second OCT scan A2. This difference is equivalent to... Figure 5 The attached figure shows the reference Δz. 12 This is equivalent to the difference in arm length between the first OCT scan A1 and the second OCT scan A2. This process is an example of the first process described above.

[0169] The first reflection intensity condition P1 includes a peak corresponding to the corneal surface, a peak corresponding to the posterior surface of the cornea, a peak corresponding to the lens surface, and a peak corresponding to the posterior surface of the lens. The distance calculation unit 460 determines the peak corresponding to the corneal surface from among the multiple peaks included in the first reflection intensity condition P1. This peak determination includes, for example, a process of determining the peak with the maximum intensity. Alternatively, the peak determination may also include a process of determining the peak with the smallest z1 coordinate value (the peak located on the -z1 side) among the peaks with intensities exceeding a predetermined threshold. The z1 coordinate value of the peak corresponding to the corneal surface determined in this way is denoted by "z". c "" indicates the coordinate value of z1 in this example. c Corresponding to the position of the corneal apex C. Calculate the z1 coordinate value z. c This processing is an example of the second processing described above.

[0170] The second reflection intensity state P2 includes, in addition to the peak corresponding to the retinal surface, multiple peaks corresponding to the inner retinal layer, peaks corresponding to the choroid, etc. The distance calculation unit 460 determines the peak corresponding to the retinal surface from the multiple peaks included in the second reflection intensity state P2. This peak determination includes, for example, a process of determining the peak with the maximum intensity. Alternatively, the peak determination may also include a process of determining the peak with the smallest z2 coordinate value (the peak located on the -z2 side) among the peaks with intensities exceeding a predetermined threshold. The z2 coordinate value of the peak corresponding to the retinal surface determined in this way is denoted by "z". M "" indicates the z2 coordinate value in this example. M Corresponding to the position of the macula center M, calculate the z2 coordinate value z. M This processing is an example of the third processing mentioned above.

[0171] The distance calculation unit 460 calculates the arm length difference Δz based on the data obtained in the first processing. 12 The corneal vertex position z determined in the second treatment cThe pupil center position z determined in the third process M Calculate the distance (axial length) between the corneal apex C and the macular center M. Figure 5 In the example shown, the axial length AL is calculated using the following formula: AL = Δz 12 +(z1(0)-z c )+(z M -z2(0)). Furthermore, the sign of the reference numerals included on the right is determined by the setting of the coherence gate position, the setting of the first part, the setting of the second part, etc., and the axial length AL is usually calculated using the following formula: AL=Δz 12 ±|z c -z1(0)|±|z M -z2(0)|. This process, used to determine the axial length of the eye, is an example of the fourth process.

[0172] <action>

[0173] An example illustrating the operation of the ophthalmic device 1 according to this embodiment. An example of the operation of the ophthalmic device 1 is shown below. Figure 6 As shown. In this example, for example, a fixed target used for macular imaging is shown to the eye being examined, E.

[0174] (S1: Perform alignment)

[0175] First, the ophthalmic device 1 is aligned with the eye being examined, E.

[0176] In this example, firstly, the alignment control unit 440 illuminates the light-emitting diode 51 of the alignment optical system 50. This projects a light beam onto the anterior eye region of the examined eye E, creating a bright spot in the anterior eye region. Two anterior eye cameras 300 then photograph the anterior eye region from different directions from which the projected light beams are projected. This results in a pair of anterior eye images, each showing a bright spot.

[0177] The offset calculation unit 430 calculates the offset of the examined eye E relative to a predetermined reference position from each determined bright spot position in a pair of anterior eye images. The alignment control unit 440 controls the movement mechanism 150 to eliminate the offset calculated by the offset calculation unit 430.

[0178] In this example, a series of processes, including front-eye imaging from two front-eye cameras 300, offset calculation from the offset calculation unit 430, and movement control from the alignment control unit 440, are repeatedly executed at predetermined time intervals, thereby gradually improving the alignment and maintaining a good alignment. The latter is called tracking.

[0179] (S2: Change the arm length to obtain the corneal signal)

[0180] If a good alignment is achieved through step S1, the scanning control unit 450 (and the data processing unit 230) changes either or both of the measuring arm length and the reference arm length to obtain a signal corresponding to the cornea of ​​the examined eye E. The measuring arm length is changed by controlling the Litertow mirror drive unit 41A, and the reference arm length is changed by controlling the Litertow mirror drive unit 114A.

[0181] Furthermore, considering that the corneal position is determined according to the running distance, the Litero reflector drive unit (either one or both of Litero reflector drive unit 41A and Litero reflector drive unit 114A) can be controlled with a predetermined control amount to position the Litero reflector (either one or both of Litero reflector 41A and Litero reflector 114A) at a position corresponding to the arm length (either the measuring arm length and the reference arm length) from which the corneal position is determined according to the predetermined running distance.

[0182] The processing in step S2 includes, for example, the "automatic Z" processing disclosed by the applicant in Japanese Patent Application Publication No. 2017-184874. Automatic Z is an automatic process for finding a suitable arm length (here, an arm length from which the corneal signal is obtained). Alternatively, the arm length adjustment in step S2 can be performed using a different process than automatic Z. In addition to automatic Z, the "Z-locking" processing disclosed in that document can also be performed. Z-locking is an automatic process for maintaining the appropriate image drawing state achieved through automatic Z.

[0183] After the arm length adjustment in step S2, alignment can be performed again using the same method as in step S1.

[0184] Here, focusing can also be achieved near the cornea by moving the OCT focusing lens 43. For example, since the corneal position is determined by the travel distance as described above, the position of the corresponding OCT focusing lens 43 can be predetermined and moved to that position. Additionally, considering the strong signal intensity from in front of the cornea, the OCT focusing lens 43 can be moved to focus on the retina at the same time as acquiring the corneal signal. In this case, the OCT focusing lens 43 can be moved either in conjunction with the movement of the focusing optical system 60, or the movement of the OCT focusing lens 43 can be determined by the amount of movement specified by the focusing optical system 60.

[0185] (S3: Apply OCT scan to the anterior eye area)

[0186] If the arm length adjustment in step S2 is completed, the scan control unit 450 performs control for applying OCT scanning to the anterior eye region of the examined eye E. In this example, the scan control unit 450 performs first scan control to cause the scan unit 410 to perform OCT scanning of the anterior eye region containing the corneal surface of the examined eye E.

[0187] The OCT scan applicable here is, for example, an A scan. Other applicable scan modes will be described later.

[0188] (S4: Generate reflection intensity status)

[0189] The scanning unit 410 (image forming unit 220) generates a reflection intensity status from the data acquired by the OCT scan in step S3. This reflection intensity status is data corresponding to the A-line applied in the A-scan in step S3.

[0190] (S5: Record the position and reflection intensity of the Littoral reflector)

[0191] The ophthalmic device 1 (e.g., distance calculation unit 460) records the position of the Littoral mirror during the OCT scan performed in step S3 and the reflection intensity generated in step S4.

[0192] When the measuring arm length is changed in step S2, the position of the Littoral reflector 41 is recorded; when the reference arm length is changed in step S2, the position of the Littoral reflector 114 is recorded. Here, the position of the Littoral reflector 41 is determined, for example, based on the control settings of the Littoral reflector drive unit 41A or by detecting the position of the Littoral reflector 41. Similarly, the position of the Littoral reflector 114 is determined, for example, based on the control settings of the Littoral reflector drive unit 114A or by detecting the position of the Littoral reflector 114.

[0193] (S6: Change the arm length to obtain the signal from the retina)

[0194] Next, the scanning control unit 450 (and the data processing unit 230) changes either or both of the measuring arm length and the reference arm length to obtain a signal corresponding to the retina of the examined eye E. This process is performed in the same manner as step S2.

[0195] (S7: Perform alignment)

[0196] If the arm length adjustment in step S6 is completed, the ophthalmic device 1 is aligned with the eye being examined, E. The alignment is performed in the same manner as in step S1.

[0197] When the OCT focusing lens 43 is moved to focus near the cornea when a signal from the cornea is acquired (as described above), the OCT focusing lens 43 can be moved at this stage to focus on the retina. At this time, the OCT focusing lens 43 can be moved either in conjunction with the movement of the focusing optical system 60 or by an amount of movement determined by the focusing optical system 60.

[0198] (S8: Apply OCT scan to the posterior eye area)

[0199] If the alignment in step S7 is completed, the scan control unit 450 performs control for applying an OCT scan to the posterior eye region of the examined eye E. In this example, the scan control unit 450 performs a second scan control that causes the scan unit 410 to perform an OCT scan of the posterior eye region including the retinal surface of the examined eye E.

[0200] The OCT scan applicable here is, for example, an A scan. Other applicable scan modes will be discussed later.

[0201] (S9: Generate reflection intensity status)

[0202] The scanning unit 410 (image forming unit 220) generates a reflection intensity status from the data acquired by the OCT scan in step S8. This reflection intensity status is data corresponding to the A-line applied in the A-scan in step S8.

[0203] (S10: Record the position and reflection intensity of the Littoral reflector)

[0204] The ophthalmic device 1 (e.g., distance calculation unit 460) records the position of the Littoral mirror during the OCT scan performed in step S8 and the reflection intensity generated in step S9. This process is performed in the same manner as step S5.

[0205] (S11: Calculate the axial length of the eye)

[0206] The distance calculation unit 460 calculates the distance between the corneal surface and the retinal surface based on the position and reflection intensity of the Littoral reflector recorded in step S5 and the position and reflection intensity of the Littoral reflector recorded in step S10.

[0207] 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 Littoral reflector recorded in step 5 (i.e., the first arm length applicable in the anterior eye OCT scan) and the position of the Littoral reflector recorded in step 10 (i.e., the second arm length applicable in the posterior eye OCT scan). Furthermore, the distance calculation unit 460 analyzes the reflection intensity recorded in step 5 to determine the position corresponding to the corneal surface (first position) and analyzes the reflection intensity recorded in step S10 to determine the position corresponding to the retinal surface (second position). Finally, the distance calculation unit 460 calculates the axial length of the examined eye E based on the difference in arm lengths, the first position, and the second position. This completes the actions described in this example (end).

[0208] <Variations on the First Embodiment>

[0209] This section describes variations applicable to the ophthalmic device 1 according to the first embodiment. Furthermore, unless otherwise specified, the reference numerals used in the description of the ophthalmic device 1 will be used in the following description.

[0210] <First Variation Example>

[0211] For example, when the examined eye has floaters, the opacities moving within the vitreous body may adversely affect the posterior ocular OCT scan.

[0212] To address this issue, multiple OCT scans can be performed on the posterior eye. These repeated OCT scans are executed by the scanning unit 410 under the control of the scanning control unit 450. Each OCT scan is typically an A scan, but it is not limited to this and can be any scanning mode such as a B scan or a three-dimensional scan.

[0213] This example illustrates an applicable repetitive OCT scan (multiple OCT scans). The ophthalmic device in this example first performs an A scan. When repeating the A scan a predetermined number of times (e.g., 10 times) fails to adequately determine the distance, the ophthalmic device switches the scanning mode from A scan to another scanning mode. This other scanning mode is, for example, a B scan. The determination of whether the distance measurement was performed appropriately includes, for example, comparing the intensity of the interference signal obtained by the OCT scan (which is the A scan at this stage) with a predetermined threshold. When the interference signal intensity is above the threshold, the distance measurement is determined to be performed appropriately; when the interference signal intensity is below the threshold, the distance measurement is determined to be performed inappropriately. The scan line length of the B scan in this example is arbitrary, typically shorter than a typical B scan (e.g., 1 mm). When repeating the B scan a predetermined number of times (e.g., 10 times) also fails to adequately determine the distance, the ophthalmic device switches the scanning mode from B scan to another scanning mode. This other scanning mode is, for example, a radar scan. The determination of whether the distance measurement was performed appropriately using the B scan is performed in the same manner as in the case of the A scan. The size of the radar scan in this example is arbitrary, typically smaller than a normal radar scan (e.g., each scan line is 1 mm long). By switching between these scan modes, a signal corresponding to the retina can be obtained at any stage.

[0214] More generally, the ophthalmic device in this example first applies a first scanning mode. The ophthalmic device in this example determines whether the data obtained by the OCT scan in the first scanning mode meets predetermined conditions. If repeating the OCT scan in the first scanning mode a predetermined number of times still fails to meet the conditions, the ophthalmic device in this example switches from the first scanning mode to a second scanning mode. The ophthalmic device in this example determines whether the data obtained by the OCT scan in the second scanning mode meets predetermined conditions. If repeating the OCT scan in the second scanning mode a predetermined number of times still fails to meet the conditions, the ophthalmic device in this example switches from the second scanning mode to a third scanning mode. Thus, the ophthalmic device in this example, by considering predetermined conditions, determines whether appropriate data is obtained by the OCT scan in the q-th scanning mode. When appropriate data is not obtained, it switches from the q-th scanning mode to the (q+1)-th scanning mode to perform an OCT scan (q is an integer greater than or equal to 1). Here, at least two scanning modes are preset, and the scanning mode transition conditions are also preset. Furthermore, the (q+1)-th scanning mode may be applied, for example, at a different location than the q-th scanning mode and / or within a wider range than the q-th scanning mode. By gradually shifting this scanning mode, signals corresponding to the retina can be detected at any stage, even when floaters are present in the eye being examined.

[0215] In multiple OCT scans, the orientation of the light scanner 44 can be either constant or variable. In the former case, other OCT scans may be unaffected by the movement of vitreous opacities, or even if one OCT scan is affected by opacities, other OCT scans may be unaffected. In the latter case, the influence of vitreous opacities can be actively avoided. However, in the latter case, it is preferable to limit the range of orientation variation of the light scanner 44 so that the object of distance measurement (e.g., the center of the macula) does not fall outside the applicable range of the OCT scan. In particular, when using A-scan, it is necessary to limit the orientation variation of the light scanner 44 to a small range. The range of orientation variation of the light scanner 44 is preset, for example, in response to the applicable scanning mode.

[0216] The scanning unit 410 generates reflection intensity status or image data from the detection signals obtained through multiple OCT scans. This yields a data set (multiple data sets) corresponding to the multiple OCT scans.

[0217] The distance calculation unit 460 obtains a single data point from a data set acquired through multiple OCT scans, and can use this single data point to perform distance calculations.

[0218] For example, the distance calculation unit 460 can generate a single data point by averaging at least two data points from a plurality of data points included in a data set (i.e., arithmetic mean). By averaging two or more data points obtained through two or more OCT scans applied to the (substantially) same location of the examined eye E, noise caused by vitreous opacities, etc., can be reduced or removed.

[0219] In other examples, the distance calculation unit 460 can select one data point from a set of data acquired through multiple OCT scans. In data selection, a predetermined evaluation value (e.g., contrast) derived from the data is referenced. Therefore, even if one of the multiple data points in the set is affected by vitreous opacities, data that is not affected or minimally affected can be selected.

[0220] Furthermore, when a single piece of data obtained by the distance calculation unit 460 does not meet predetermined conditions (e.g., contrast conditions), the ophthalmic device 1 may display a message prompting the re-performation of a posterior ocular OCT scan or the re-performation of a posterior ocular OCT scan.

[0221] <Second Variation>

[0222] To accurately determine the distance between two parts of the examined eye E, it is necessary to correctly identify the two parts. For this purpose, OCT scanning can be applied to the three-dimensional region of the examined eye E. Examples of scanning modes used for this purpose include three-dimensional scanning, radar scanning, and multi-line cross-scanning. Here, radar scanning is a scanning mode consisting of multiple line scans arranged radially (multiple B scans), and multi-line cross-scanning is a scanning mode consisting of two groups of line scans that are orthogonal to each other.

[0223] The scanning control unit 450, for example, in at least one of anterior eye OCT scanning and posterior eye OCT scanning, causes the scanning unit 410 to perform an OCT scan of a three-dimensional region of the examined eye E.

[0224] Typically, the scanning control unit 450 can cause the scanning unit 410 to perform an OCT scan of a three-dimensional region of the corneal surface containing the examined eye E during anterior ocular OCT scanning. Under well-aligned conditions, an OCT scan is performed on the three-dimensional region of the anterior ocular region containing the corneal apex of the examined eye E.

[0225] Furthermore, during posterior eye OCT scanning, the scanning control unit 450 causes the scanning unit 410 to perform an OCT scan of a three-dimensional region of the retinal surface including the examined eye E. With proper alignment, an OCT scan is performed on the three-dimensional region of the posterior eye including the macula of the examined eye E.

[0226] The distance calculation unit 460 analyzes the data obtained by OCT scanning of the three-dimensional region of the examined eye E, thereby determining the feature positions corresponding to the feature points of the examined eye E.

[0227] Typically, the distance calculation unit 460 analyzes data acquired through a three-dimensional OCT scan of the anterior eye region containing the corneal apex of the examined eye E, thereby determining the feature position corresponding to the corneal apex. This process includes, for example, determining an image region corresponding to the corneal surface from data of the three-dimensional region of the anterior eye region, and determining the feature position (corneal apex position) corresponding to the corneal apex from the shape of the image region.

[0228] Furthermore, the distance calculation unit 460 analyzes data acquired through an OCT scan of a three-dimensional region of the posterior eye containing the macula of the examined eye E, thereby determining a feature location corresponding to the macula. This process includes, for example, determining an image region corresponding to the retinal surface (internal limiting membrane, etc.) from data of the three-dimensional region of the posterior eye, and determining a feature location (macula location) corresponding to the macula from the shape of the image region, the location of a predetermined tissue, and the location of a predetermined site. As an example of a predetermined tissue, there is a retinal accessory tissue (layer tissue), and as an example of a predetermined site, there is the optic nerve head.

[0229] The distance calculation unit 460 calculates the length of a line segment with the determined feature position as one end. This line segment length is the distance to the target.

[0230] When the corneal apex position is determined from data acquired via anterior ocular OCT scan and the macular center position is determined from data acquired via posterior ocular 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 is equivalent to the axial length of the examined eye E.

[0231] <Effect>

[0232] The effects of the ophthalmic device 1 of the first embodiment and its modifications will be explained.

[0233] The ophthalmic device 1 includes a scanning unit 410, a moving mechanism 150, an offset measuring unit 420, a scanning control unit 450, an alignment control unit 440, and a distance calculation unit 460.

[0234] The scanning unit 410 is configured to perform OCT scanning on the eye being examined, E. The moving mechanism 150 is configured to move at least a portion of the scanning unit. The offset measuring unit 420 measures the offset of the eye being examined, E, from a predetermined reference position.

[0235] The scan control unit 450 performs a first scan control that causes the scan unit 410 to perform an OCT scan of a first region (e.g., the anterior eye region) including a first part (e.g., the corneal surface) of the examined eye E, and a second scan control that causes the scan unit 410 to perform an OCT scan of a second region (e.g., the posterior eye region) including a second part (e.g., the retinal surface) different from the first part. The OCT scan performed under the first scan control is called the first OCT scan, and the OCT scan performed under the second scan control is called the second OCT scan.

[0236] The alignment control unit 440 performs a first alignment control of the moving mechanism 150 based on the first offset information of the examined eye E obtained by the offset measuring unit 420 before the first scan control, and a second alignment control of the moving mechanism 150 based on the second offset information of the examined eye E obtained by the offset measuring unit 420 before the second scan control. Furthermore, the ophthalmic device 1 is capable of performing alignment in the xy direction and alignment in the z direction.

[0237] The distance calculation unit 460 calculates the distance (e.g., axial length) between the first part and the second part 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.

[0238] According to this ophthalmic device 1, alignment is performed before each first OCT scan and second OCT scan, thus enabling the first and second OCT scans to be performed in a well-aligned state. Therefore, for example, when the second OCT scan is performed after the first OCT scan, even if the eye being examined is moved between the first and second OCT scans, the reliability of distance measurement can be ensured because the second OCT scan is performed after aligning the moved eye.

[0239] As an arbitrary configuration, the scanning unit 410 of the ophthalmic device 1 includes an interferometric optical system comprising a measuring arm that guides the measuring light LS to the examined eye E and a reference arm that guides the reference light LR. Furthermore, as an arbitrary configuration, the scanning unit 410 is disposed on at least one of the measuring arm and the reference arm, and includes an arm length changing unit that changes the arm length under the control of the scanning control unit 450. A Littrow mirror 41 and a Littrow mirror drive unit 41A are examples of arm length changing units disposed on the measuring arm. A Littrow mirror 114 and a Littrow mirror drive unit 114A are examples of arm length changing units disposed on the reference arm.

[0240] In addition to the above, as an arbitrary structure, the distance calculation unit 460 can perform the following series of processes: (1) processing to calculate the difference (arm length difference) between the first arm length applicable under the first scan control (first OCT scan) and the second arm length applicable under the second scan control (second OCT scan); (2) processing to parse the first data obtained by the first OCT scan to determine the first position (e.g., the signal position corresponding to the first part of the examined eye E); (3) processing to parse the second data obtained by the second OCT scan to determine the second position (e.g., the signal position corresponding to the second part of the examined eye E); (4) processing to calculate the distance (e.g., axial length) between the first part and the second part based on the arm length difference calculated in (1), the first position determined in (2), and the second position determined in (3).

[0241] Based on this arbitrary structure, specific processing can be provided for calculating the distance between the first and second parts of the examined eye E.

[0242] As an arbitrary structure, the scan control unit 450 can cause the scan unit 410 to perform multiple OCT scans under at least one of first scan control (first OCT scan) and second scan control (second OCT scan). In this case, the distance calculation unit 460 can acquire a single data point from the data set acquired through the multiple OCT scans. Here, the distance calculation unit 460 performs an arithmetic average on the data set acquired through the multiple OCT scans, thereby generating a single data point. Furthermore, the distance calculation unit 460 can use the acquired single data point to calculate the distance between the first part and the second part.

[0243] According to this arbitrary structure, even when turbidity or other substances moving within the vitreous body adversely affect posterior ocular OCT scans, the reliability of distance measurement can be improved by reducing and removing noise caused by turbidity or other substances, and by selecting data that is not affected by turbidity or other substances with minimal impact.

[0244] As an arbitrary structure, the scanning control unit 450 can cause the scanning unit 410 to perform an OCT scan of a three-dimensional region of the examined eye E under at least one of a first scanning control (first OCT scan) and a second scanning control (second OCT scan). In this case, the distance calculation unit 460 can determine the feature position corresponding to the feature point of the examined eye E by analyzing the data obtained by the OCT scan of the three-dimensional region. Moreover, the distance calculation unit 460 can calculate the distance between the first part and the second part using the length of a line segment with the feature position as one end.

[0245] As a first typical example, the scan control unit 450, under first scan control (first OCT scan), enables the scan unit 410 to perform an OCT scan of a three-dimensional region encompassing the corneal surface of the examined eye E. Furthermore, the distance calculation unit 460, by analyzing the data acquired through the OCT scan of this three-dimensional region, can determine the feature position corresponding to the corneal apex of the examined eye E. In this case, the distance calculation unit 460 can calculate the distance between the first and second locations using the length of a line segment with the corneal apex as one end.

[0246] As a second typical example, the scan control unit 450 can, under second scan control (second OCT scan), cause the scan unit to perform an OCT scan of a three-dimensional region including the retinal surface of the examined eye E. Furthermore, the distance calculation unit 460 can determine the feature position corresponding to the macular center of the examined eye E by analyzing the data acquired through the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460 can calculate the distance between the first and second locations using the length of a line segment with the macular center as one end.

[0247] By combining the first and second typical examples, the length of the line segment with the corneal vertex as one end and the macula center as the other end can be determined, which is the axial length of the examined eye E.

[0248] As an arbitrary structure, the offset measuring unit 420 includes an alignment optical system 50 (projection system), two (or more) anterior eye cameras 300 (two or more imaging units), and an offset calculation unit 430. The alignment optical system 50 projects a light beam onto the anterior eye of the eye being examined, E. The two (or more) anterior eye cameras 300 capture images of the anterior eye of the eye being examined, E, from different directions. The offset calculation unit 430 calculates the offset of the eye being examined, E, from a predetermined reference position based on the positions of the light beam images (bright spots) drawn in the two (or more) anterior eye images acquired by the two (or more) anterior eye cameras 300.

[0249] Based on this arbitrary structure, a specific structure and processing can be provided for measuring the offset of the examined eye E from a predetermined reference position.

[0250] Furthermore, any items described in the first embodiment (structure, components, processing, action, function, etc.) and any known items can be combined into the ophthalmic device listed in this effect section.

[0251] The first embodiment provides a control method for an ophthalmic device. The ophthalmic device includes a scanning unit 410 for OCT scanning of an eye E to be examined, a moving mechanism 150 for moving at least a portion of the scanning unit 410, and a deviation measuring unit 420 for measuring the deviation of the eye E from a predetermined reference position.

[0252] The 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.

[0253] The first alignment control step controls the movement mechanism 150 based on the first offset information of the examined eye E obtained by the offset measuring unit 420. The first scan control step causes the scanning unit 410 to perform an OCT scan of a first region containing the first part of the examined eye E. This OCT scan is called the first OCT scan.

[0254] The second alignment control step controls the movement mechanism 150 based on the second offset information of the examined eye E obtained by the offset measurement unit 420. The second scan control step causes the scanning unit 410 to perform an OCT scan of a second region containing the examined eye E, which is different from the first region. This OCT scan is called the second OCT scan.

[0255] The distance calculation step calculates the distance between the first part and the second part based on the first data obtained by the scanning unit 410 in the first scanning control step and the second data obtained by the scanning unit 410 in the second scanning control step.

[0256] According to the control method of this ophthalmic device, since alignment is performed before each first OCT scan and second OCT scan, the first and second OCT scans can be performed in a well-aligned state. Therefore, the reliability of distance measurement can be ensured.

[0257] Furthermore, any items described in the first embodiment (structure, elements, processing, actions, functions, etc.) and any known items can be combined into this control method.

[0258] A program can be configured to enable a computer to execute this control method. This program may, for example, include any of the aforementioned programs for operating the ophthalmic device 1 of the first embodiment or its modifications.

[0259] Alternatively, a computer-readable non-volatile storage medium storing such a program can be manufactured. This non-volatile storage medium can be of any form; examples include magnetic disks, optical disks, optical discs, and semiconductor memories.

[0260] <Second Implementation>

[0261] As explained above, the first embodiment improves the reliability of distance measurement of the examined eye by aligning the two scans before each first and second OCT scan. In other words, the first embodiment improves the reliability of distance measurement by enhancing the reliability of the first and second OCT scans.

[0262] In response, the second embodiment improves the reliability of distance measurement by correcting the alignment error present in the OCT scan during data processing.

[0263] Hereinafter, unless specifically mentioned, descriptions of items identical to those in the first embodiment will be omitted. Furthermore, elements in the second embodiment that are identical to those in the first embodiment will be labeled with the same reference numerals as their corresponding elements in the first embodiment. Additionally, in the following description, reference will be made to the elements of the first embodiment as needed.

[0264] <structure>

[0265] An example of the structure of the ophthalmic device in this embodiment is shown below. Figure 7 As shown. The ophthalmic device 1A has the same hardware structure as the ophthalmic device 1 of the first embodiment (see reference). Figure 1 , Figure 2 , Figure 3A , Figure 4A as well as Figure 4B ). Alternative to the first embodiment Figure 3B Applicable to the structure shown Figure 7 The structure shown.

[0266] In the ophthalmic device 1A, the scanning unit 410, the offset measuring unit 420, and the moving mechanism 150 have the same structure, function, and effect as in the first embodiment.

[0267] The scanning unit 410 acquires data by performing an OCT scan on the eye being examined, E. Similar to the first embodiment, the scanning unit 410 includes an interference optical system comprising a measurement arm that guides the measurement light LS to the eye being examined, and a reference arm that guides the reference light LS. Furthermore, similar to the first embodiment, the scanning unit 410 includes an arm length adjustment section provided on at least one of the measurement arm and the reference arm.

[0268] The offset measuring unit 420 measures the offset of the examined eye E from a preset reference position. Similar to the first embodiment, the offset measuring unit 420 may include an alignment optical system 50, a front eye camera 300, and an offset calculation unit 430. Figure 7 The offset measuring unit 420 shown is an example applicable when the position of the examined eye E is defined as the bright spot position. When using other definitions (e.g., pupil center position, corneal apex position, etc.), a structure that responds accordingly is applicable.

[0269] The alignment control unit 440A, described later, can perform alignment control based on the offset measurement results (offset information) obtained by the offset measurement unit 420. Furthermore, the distance calculation unit 460A, described later, can calculate a predetermined distance within the examined eye E, taking into account the offset information obtained by the offset measurement unit 420.

[0270] As described in detail below, the ophthalmic device 1A performs a first OCT scan on a first region (e.g., the anterior ocular region) containing a first part (e.g., the corneal surface) of the examined eye E, and a second OCT scan on a second region (e.g., the posterior ocular region) containing a second part (e.g., the retinal surface). Furthermore, the order in which the first and second OCT scans are performed is arbitrary.

[0271] The offset measurement unit 420 is capable of performing a first offset measurement to obtain first offset information in response to a first OCT scan and performing a second offset measurement to obtain second offset information in response to a second OCT scan.

[0272] The first offset measurement is performed at any time before, during, and after the first OCT scan. Similarly, the second offset measurement is performed at any time before, during, and after the second OCT scan. Typically, the first offset measurement is performed at any time before, during, and immediately after the first OCT scan, and the second offset measurement is performed at any time before, during, and immediately after the second OCT scan.

[0273] The distance calculation unit 460A, described later, can calculate a predetermined distance within the examined eye E by considering either or both of the first offset information and the second offset information obtained by the offset measurement unit 420. Furthermore, the alignment control unit 440A, described later, can perform alignment control based on either the first offset information or the second offset information obtained by the offset measurement unit 420. Moreover, the structure of performing alignment control based on the first offset information (first alignment control) and performing alignment control based on the second offset information (second alignment control) is equivalent to the first embodiment.

[0274] Similar to the first embodiment, the moving mechanism 150 is capable of moving the scanning unit 410 (in particular, the measuring arm of the interference optical system) relative to the eye being examined E.

[0275] Alignment control unit 440A and scanning control unit 450A are provided in control unit 210A. Control unit 210A is provided instead of control unit 210 in the first embodiment. Control unit 210A includes a processor that controls various parts of ophthalmic device 1A. Control unit 210A includes a main control unit (not shown) and a storage unit. Control unit 210A is implemented through the cooperation of hardware including circuitry and control software.

[0276] Similar to the first embodiment, the alignment control unit 440A performs alignment control of the moving mechanism 150 based on the offset information obtained by the offset measuring unit 420.

[0277] The scan control unit 450A performs first scan control, causing the scan unit 410 to perform an OCT scan of a first region (e.g., the anterior eye region) containing a first part (e.g., the corneal surface) of the examined eye E, and second scan control, causing the scan unit 410 to perform an OCT scan of a second region (e.g., the posterior eye region) containing a second part (e.g., the retinal surface) different from the first part. The first and second scan controls are performed in the same manner as the scan control unit 450 of the first embodiment. The OCT scan performed by the first scan control is called the first OCT scan, and the OCT scan performed by the second scan control is called the second OCT scan.

[0278] As mentioned above, the offset measurement unit 420 performs offset measurement of the examined eye E before, during, or after the execution of the first scan control to obtain first offset information, and performs offset measurement of the examined eye E before, during, or after the execution of the second scan control to obtain second offset information.

[0279] The distance calculation unit 460A calculates the distance (e.g., axial length) between a first part (e.g., corneal surface) and a second part (e.g., retinal surface) of the examined eye E based on either or both of the first offset information and the second offset information, the first data obtained by the first OCT scan, and the second data obtained by the second OCT scan.

[0280] In other words, the distance calculation unit 460A considers either or both of the alignment error (first offset information) during the first OCT scan and the alignment error (second offset information) during the second OCT scan when performing distance calculation.

[0281] The distance calculation unit 460A performs the following series of processes, for example. First, the distance calculation unit 460A calculates the difference (arm length difference) between the first arm length applicable in the first OCT scan and the second arm length applicable in the second OCT scan. Second, the distance calculation unit 460A analyzes the first data acquired through the first OCT scan to determine a first position (e.g., the signal position on the corneal surface) corresponding to a first part of the examined eye E. Third, the distance calculation unit 460A analyzes the second data acquired through the second OCT scan to determine a second position (e.g., the signal position on the retinal surface) corresponding to a second part of the examined eye E. The first to third processes are performed in the same manner as in the first embodiment. Fourth, the distance calculation unit 460A calculates the distance between the first part and the second part based on the arm length difference calculated in the first process, the first position determined in the second process, the second position determined in the third process, and the offset information (at least one of the first offset information and the second offset information) acquired by the offset measurement unit 420.

[0282] Reference Figure 8An example illustrating this computational processing. (Compared to the first embodiment) Figure 5 Similarly, in the attached diagram, reference numeral C denotes the corneal apex of the examined eye E, and reference numeral M denotes the macula. The straight line Ax passing through the corneal apex C and the macula M represents the axial length of the examined eye E.

[0283] In the attached diagram, reference numeral K denotes the center of curvature of the corneal surface at the corneal apex C. The center of curvature K is the center of the curvature circle (contact circle) at the corneal apex C. The radius of this curvature circle, i.e., the radius of curvature of the corneal surface at the corneal apex C, is denoted as r.

[0284] In the attached figure, reference numeral G indicates the path (incident path) of the measuring light LS projected toward the center of the macula M. Reference numeral H indicates the intersection of the incident path G and the corneal surface of the tested eye E, i.e., the incident position of the measuring light LS on the tested eye E.

[0285] The offset (height) of the incident path G relative to the axial length Ax is denoted as h. If we assume that the shape of the corneal surface is substantially spherical, or if we assume that the height h is sufficiently small (i.e., if we assume that the alignment error is sufficiently small), then we can consider 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.

[0286] The angle formed by the line segment connecting the incident position H and the center of curvature K relative to the axial length Ax is denoted as θ. Similarly, the angle formed by the line segment connecting the incident position H and the center of the macula M relative to the axial length Ax is denoted as φ.

[0287] The length of the line segment connecting the incident position H and the center of the macula M is denoted as ALm. This length ALm is equivalent to the measured value of the axial length of the examined eye E obtained from OCT scanning using measurement light LS projected onto the center of the macula M through the incident path G.

[0288] The axial length (true value) of the examined eye E is set as AL. Additionally, the axial (Ax) component of the vector along the axial direction Ax—the distance between the corneal vertex C and the incident position H, i.e., the vector originating from the corneal vertex C and ending at the incident position H—is set as AL1. Furthermore, the axial (Ax) component of the vector along the axial direction Ax—the distance between the incident position H and the macula center M, i.e., the vector originating from the macula center M and ending at the incident position H—is set as AL2.

[0289] from Figure 8 It can be seen that the axial length AL is expressed by the following formula: AL=AL1+AL2=(rr×cosθ)+ALm×cosφ=(rr×cos(arcsin(h / r)))+ALm×cos(arcsin(h / ALm)).

[0290] Here, the corneal curvature radius r is obtained in advance using a corneal shape measuring device such as a corneal curvature meter. Additionally, the height h is the alignment error in the xy direction measured by the offset measuring unit 420, and is included in the offset information. Furthermore, the axial length measurement value ALm is obtained using the ophthalmic device 1A in the same manner as in the first embodiment. The axial length AL is calculated by substituting these values ​​r, h, and ALm into the above formula.

[0291] The distance calculation unit 460A, for example, stores the above formula and the corneal curvature radius value (r) of the examined eye E in advance. The distance calculation unit 460A calculates the axial length value (AL) of the examined eye E by substituting the corneal curvature radius value (r), the xy-direction offset (h) included in the offset information obtained by the offset measurement unit 420, and the axial length value (ALm) measured by OCT scanning into the above formula.

[0292] Furthermore, this example illustrates the case where alignment errors exist in the xy direction during posterior eye OCT scanning. However, it will be readily apparent to those skilled in the art that the same calculations are performed for cases where alignment errors exist in the xy direction during anterior eye OCT scanning, as well as for cases where alignment errors exist in both anterior and posterior eye OCT scanning.

[0293] In addition, this example only considers measuring the refraction of light LS on the corneal surface, but other refractive index boundaries can also be considered. For example, the refraction of light LS on the posterior surface of the cornea, the lens surface, and the posterior surface of the lens can also be considered.

[0294] In addition to the alignment error in the xy direction, the alignment error in the z direction can also be considered. Similar to the first embodiment, the alignment error in the z direction is calculated by the offset measuring unit 420.

[0295] <action>

[0296] Hereinafter, examples of the operation of the ophthalmic device 1A of this embodiment will be described. Hereinafter, a first operation example of calculating distance by considering both first offset information and second offset information will be described, and a second operation example of calculating distance by considering the second offset information while using the first offset information for alignment will be described.

[0297] <Example of the first action>

[0298] The first action example of ophthalmic device 1A is in Figure 9 As shown. In this example, for example, a fixed target used for macular imaging is shown to the eye being examined, E. Alternatively, preparatory alignment may be performed before step S21.

[0299] (S21: Change the arm length to obtain the corneal signal)

[0300] Using the same method as step S2 in the first embodiment, the scanning control unit 450A (and the data processing unit 230) changes either or both of the measuring arm length and the reference arm length to obtain a signal corresponding to the cornea of ​​the examined eye E.

[0301] (S22: Obtain the first offset information)

[0302] If the arm length changes at the end of step S21, the offset measurement unit 420 performs a first offset measurement corresponding to the first OCT scan (anterior eye OCT scan) to obtain first offset information.

[0303] (S23: Apply OCT scan to the anterior eye area)

[0304] If the offset information acquisition in step S22 is completed, the scan control unit 450A performs control for applying an OCT scan to the anterior eye region of the examined eye E. In this example, the scan control unit 450A performs a first scan control to cause the scan unit 410 to perform an OCT scan of the anterior eye region containing the corneal surface of the examined eye E. Step S23 is performed in the same manner as step S3 in the first embodiment.

[0305] (S24: Generate reflection intensity status)

[0306] The scanning unit 410 (image forming unit 220) generates a reflection intensity status from the data acquired by the OCT scan in step S23. This reflection intensity status is, for example, data corresponding to the A-line applied in the A-scan in step S23.

[0307] (S25: Record the position, reflection intensity, and first offset information of the Littoral mirror)

[0308] The ophthalmic device 1 (e.g., distance calculation unit 460A) records the position of the Littoral mirror during the OCT scan performed in step S23 and the reflection intensity generated in step S24, using the same method as step S5 in the first embodiment. Furthermore, the ophthalmic device 1 (e.g., distance calculation unit 460A) records the first offset information obtained in step S22.

[0309] (S26: Change the arm length to obtain the signal from the retina)

[0310] Next, the scanning control unit 450A (and the data processing unit 230) changes either or both of the measuring arm length and the reference arm length to obtain a signal corresponding to the retina of the examined eye E.

[0311] (S27: Obtain the second offset information)

[0312] If the arm length adjustment in step S26 is completed, the offset measurement unit 420 performs a second offset measurement corresponding to the second OCT scan (posterior eye OCT scan) to obtain second offset information. This process is performed in the same manner as step S22.

[0313] (S28: Apply OCT scan to the posterior eye area)

[0314] If the offset information acquisition in step S27 is completed, the scan control unit 450A performs control for applying an OCT scan to the posterior eye region of the examined eye E. In this example, the scan control unit 450A performs a second scan control that causes the scan unit 410 to perform an OCT scan of the posterior eye region including the retinal surface of the examined eye E.

[0315] (S29: Generation of reflection intensity status)

[0316] The scanning unit 410 (image forming unit 220) generates a reflection intensity status from the data acquired by the OCT scan in step S28. This reflection intensity status is, for example, data corresponding to the A-line of the A-scan applied in step S28.

[0317] (S30: Record the position, reflection intensity, and second offset information of the Littoral mirror)

[0318] The ophthalmic device 1 (e.g., distance calculation unit 460A) records the position of the Littoral mirror during the OCT scan performed in step S28, the reflection intensity status generated in step S29, and the second offset information obtained in step S27, in the same manner as step S25.

[0319] (S31: Calculate the axial length of the eye)

[0320] The distance calculation unit 460A calculates the distance between the corneal surface and the retinal surface based on the position, reflection intensity, and first offset information of the Littoral reflector recorded in step S25, and the position, reflection intensity, and second offset information of the Littoral reflector recorded in step S30.

[0321] 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 Littoral reflector recorded in step 25 (i.e., the first arm length applicable to anterior eye OCT scanning) and the position of the Littoral reflector recorded in step 30 (i.e., the second arm length applicable to posterior eye OCT scanning). Furthermore, the distance calculation unit 460A analyzes the reflection intensity recorded in step 25 to determine the position corresponding to the corneal surface (first position), and analyzes the reflection intensity recorded in step S30 to determine the position corresponding to the retinal surface (second position). In addition to the arm length difference, the first position, and the second position, the distance calculation unit 460A also calculates the axial length of the examined eye E based on the first offset information recorded in step S25 and the second offset information recorded in step S30. This calculation, for example, follows the same procedure as... Figure 8 The method described above will be performed together. Furthermore, in this example, one can consider both alignment errors in the anterior eye OCT scan and alignment errors in the posterior eye OCT scan. That concludes the execution of this example (end).

[0322] <Example of the second action>

[0323] The second action example of ophthalmic device 1A is in Figure 10 As shown. In this example, for instance, the fixed target for macular imaging is shown toward the eye being examined, E. Alternatively, preparatory alignment may be performed before step S41.

[0324] (S41: Change the arm length to obtain the corneal signal)

[0325] The scanning control unit 450A (and the data processing unit 230) changes either or both of the measuring arm length and the reference arm length to obtain a signal corresponding to the cornea of ​​the examined eye E.

[0326] (S42: Obtain first offset information and perform alignment)

[0327] If the arm length change in step S41 ends, the offset measurement unit 420 performs a first offset measurement corresponding to the first OCT scan (anterior eye OCT scan) to acquire first offset information. The alignment control unit 440A performs alignment control on the moving mechanism 150 based on the acquired first offset information. The alignment control is performed in the same manner as in the first embodiment.

[0328] (S43: Apply OCT scan to the anterior eye area)

[0329] If the alignment in step S42 is completed, the scan control unit 450A performs control for applying an OCT scan to the anterior eye region of the examined eye E. In this example, the scan control unit 450A performs a first scan control to cause the scan unit 410 to perform an OCT scan of the anterior eye region containing the corneal surface of the examined eye E. This anterior eye OCT scan can be assumed to be performed under good alignment conditions.

[0330] (S44: Generate reflection intensity status)

[0331] The scanning unit 410 (image forming unit 220) generates a reflection intensity status from the data acquired by the OCT scan in step S43. This reflection intensity status is, for example, data corresponding to the A-line of the A-scan applied in step S43.

[0332] (S45: Record the position and reflection intensity of the Littoral reflector)

[0333] The ophthalmic device 1 (e.g., distance calculation unit 460A) records the position of the Littoral mirror during the OCT scan performed in step S43 and the reflection intensity generated in step S44.

[0334] (S46: Change the arm length to obtain the signal from the retina)

[0335] Next, the scanning control unit 450A (and the data processing unit 230) changes either or both of the measuring arm length and the reference arm length to obtain a signal corresponding to the retina of the examined eye E.

[0336] (S47: Obtain the second offset information)

[0337] If the arm length adjustment in step S46 is completed, the offset measurement unit 420 performs a second offset measurement corresponding to the second OCT scan (posterior eye OCT scan) to obtain second offset information. Unlike the anterior eye OCT scan, which is assumed to be performed under good alignment, a good alignment cannot be guaranteed in posterior eye alignment. Therefore, the second offset information is only considered in the distance calculation (step S51 described later).

[0338] (S48: Apply OCT scan to the posterior eye area)

[0339] If the offset information acquisition in step S47 is completed, the scan control unit 450A performs control for applying an OCT scan to the posterior eye region of the examined eye E. In this example, the scan control unit 450A performs a second scan control that causes the scan unit 410 to perform an OCT scan of the posterior eye region including the retinal surface of the examined eye E.

[0340] (S49: Generating reflection intensity status)

[0341] The scanning unit 410 (image forming unit 220) generates a reflection intensity status from the data acquired by the OCT scan in step S48. This reflection intensity status is, for example, data corresponding to the A-line of the A-scan applied in step S48.

[0342] (S50: Record the position, reflection intensity, and second offset information of the Littoral mirror)

[0343] The ophthalmic device 1 (e.g., distance calculation unit 460A) records the position of the Littoral mirror during the OCT scan performed in step S48, the reflection intensity status generated in step S49, and the second offset information obtained in step S47.

[0344] (S51: Calculate the axial length of the eye)

[0345] The distance calculation unit 460A calculates the distance between the corneal surface and the retinal surface based on the position and reflection intensity of the Littoral reflector recorded in step S45, the position and reflection intensity of the Littoral reflector recorded in step S50, and the second offset information.

[0346] 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 Littoral reflector recorded in step 45 (i.e., the first arm length applicable to anterior eye OCT scan) and the position of the Littoral reflector recorded in step 50 (i.e., the second arm length applicable to posterior eye OCT scan). Furthermore, the distance calculation unit 460A analyzes the reflection intensity recorded in step 45 to determine the position corresponding to the corneal surface (first position), and analyzes the reflection intensity recorded in step S50 to determine the position corresponding to the retinal surface (second position). In addition to the arm length difference, the first position, and the second position, the distance calculation unit 460A also calculates the axial length of the examined eye E based on the second offset information recorded in step S50. This calculation, for example, follows the same procedure as... Figure 8 The method described above will be executed. This completes the action example for this task (end).

[0347] <Variations on the Second Embodiment>

[0348] The following describes the variations that can be applied to the ophthalmic device 1A in the second embodiment. Furthermore, unless otherwise specifically mentioned, the reference numerals used in the description of ophthalmic device 1 and / or ophthalmic device 1A are used in the following description.

[0349] <First Variation Example>

[0350] Similar to the first variation of the first embodiment, in order to address the adverse effects of vitreous opacities moving within the vitreous body on posterior ocular OCT scans, multiple OCT scans can be performed on the posterior ocular region. These repeated OCT scans are executed by the scanning unit 410 under the control of the scanning control unit 450A.

[0351] The scanning unit 410 generates reflection intensity status or image data from the detection signals obtained through multiple OCT scans. This yields a data set (multiple data sets) corresponding to the multiple OCT scans. The distance calculation unit 460A obtains a single data set from the data set acquired through the multiple OCT scans and can perform distance calculations using that single data set.

[0352] <Second Variation>

[0353] Similar to the second variation of the first embodiment, in order to accurately determine the two parts of the examined eye E, an OCT scan can be applied to the three-dimensional region of the examined eye E. The scan control unit 450A, for example, causes the scan unit 410 to perform an OCT scan of the three-dimensional region of the examined eye E in at least one of anterior eye OCT scan and posterior eye OCT scan.

[0354] The distance calculation unit 460A analyzes data acquired through OCT scanning of a three-dimensional region of the examined eye E, determines the feature positions corresponding to feature points of the examined eye E, and calculates the length of a line segment with the determined feature positions as one end. This line segment length is the distance to the target being measured.

[0355] <Effect>

[0356] The effects of the ophthalmic device 1A of the second embodiment and its modifications are explained.

[0357] The ophthalmic device 1A includes a scanning unit 410, a displacement measuring unit 420, a scanning control unit 450A, and a distance calculation unit 460A.

[0358] The scanning unit 410 performs an OCT scan on the eye being examined, E. The offset measuring unit 420 measures the offset of the eye being examined, E, from a predetermined reference position.

[0359] The scanning control unit 450A performs a first scan control that causes the scanning unit 410 to perform an OCT scan of a first region (e.g., the anterior eye region) containing a first part (e.g., the corneal surface) of the eye being examined E, and a second scan control that causes the scanning unit 410 to perform an OCT scan of a second region (e.g., the posterior eye region) containing a second part (e.g., the retinal surface) that is different from the first part.

[0360] The distance calculation unit 460A calculates the distance (e.g., axial length) between the first part and the second part of the examined eye E based on at least one of the first offset information of the examined eye E obtained by the offset measurement unit 420 corresponding to the first scan control and the second offset information of the examined eye E obtained by the offset measurement unit 420 corresponding to the second scan control, the first data obtained by the scanning unit 410 under the first scan control, and the second data obtained by the scanning unit 410 under the second scan control.

[0361] According to this ophthalmic device 1A, the alignment error (offset information) in either or both of the first and second OCT scans can be acquired, and distance calculation can be performed taking this alignment error into account. Therefore, even in the case where the second OCT scan is performed after the first OCT scan, the reliability of the distance measurement can be ensured, even if the eye is moved between the first and second OCT scans.

[0362] As an arbitrary structure, the offset measuring unit 420 can acquire offset information corresponding to one of the scanning controls, the first scan control and the second scan control, and acquire another offset information before the other scan control. Furthermore, the ophthalmic device 1A may include a moving mechanism 150 and an alignment control unit 440A. The moving mechanism 150 moves at least a portion of the scanning unit 410. The alignment control unit 440A performs alignment control of the moving mechanism 150 based on the other offset information before the other scan control. The distance calculation unit 460A is capable of performing distance calculation based on the offset information, the first data, and the second data.

[0363] For example, in Figure 10 In the second example of operation shown, the offset measuring unit 420 acquires first offset information and performs alignment before the first scan control, and performs distance calculation based on the second offset information, first data and second data acquired corresponding to the second scan control.

[0364] Based on this arbitrary structure, distance calculation can be performed by performing one of the first OCT scan and the second OCT scan after alignment, while taking into account the alignment error in the other, enabling distance measurement to be performed with high reliability.

[0365] As an arbitrary structure, the scanning unit 410 may include an interferometric optical system and an arm length changing unit. The interferometric optical system includes a measuring arm that guides the measuring light LS to the eye being examined E and a reference arm that guides the reference light LR. The arm length changing unit is provided on at least one of the measuring arm and the reference arm, and changes the arm length under the control of the scanning control unit 450A. The Littrow mirror 41 and the Littrow mirror drive unit 41A are examples of the arm length changing unit provided on the measuring arm. The Littrow mirror 114 and the Littrow mirror drive unit 114A are examples of the arm length changing unit provided on the reference arm.

[0366] In addition to the above, as an arbitrary structure, the distance calculation unit 460A can perform the following series of processes: (1) processing to calculate the difference (arm length difference) between the first arm length applicable under the first scan control (first OCT scan) and the second arm length applicable under the second scan control (second OCT scan); (2) processing to parse the first data obtained by the first OCT scan to determine the first position (e.g., the signal position on the corneal surface) corresponding to the first part of the examined eye E; (3) processing to parse the second data obtained by the second OCT scan to determine the second position (e.g., the signal position on the retinal surface) corresponding to the second part of the examined eye E; (4) processing to calculate the distance (e.g., axial length) between the first part and the second part based on at least one of the arm length difference calculated in (1), the first position determined in (2), the second position determined in (3), the first offset information and the second offset information obtained by the offset measurement unit 420.

[0367] Here, the distance calculation unit 460A can be configured as follows. First, the distance calculation unit 460A calculates a provisional distance between the first part and the second part based on the arm length difference, the first position, and the second position. Furthermore, the distance calculation unit 460A calculates the distance between the first part and the second part based on this provisional distance, at least one of the first offset information and the second offset information, and the pre-acquired corneal curvature radius of the examined eye E.

[0368] As a specific example of this distance calculation, when the provisional distance between the first part and the second part is set to ALm, one of the first offset information and the second offset information is set to h, the corneal curvature radius is set to r, and the distance (true value) between the first part and the second part is set to AL, the distance calculation unit 460A can calculate the distance AL by the formula AL=(rr×cos(arcsin(h / r)))+ALm×cos(arcsin(h / ALm)).

[0369] Based on these arbitrary structures, specific processing can be provided for calculating the distance between the first and second parts of the examined eye E.

[0370] As an arbitrary structure, the scan control unit 450A can cause the scan unit 410 to perform multiple OCT scans under at least one of first scan control (first OCT scan) and second scan control (second OCT scan). In this case, the distance calculation unit 460A can acquire a single data point from the data set acquired through the multiple OCT scans. Here, the distance calculation unit 460A can generate a single data point by performing an arithmetic average on the data set acquired through the multiple OCT scans. Furthermore, the distance calculation unit 460A can use the acquired single data point to calculate the distance between the first part and the second part (e.g., the aforementioned provisional distance).

[0371] According to this arbitrary structure, even when turbidity or other substances moving within the vitreous body adversely affect posterior ocular OCT scans, the reliability of distance measurement can be improved by reducing and removing noise caused by turbidity or other substances, and by selecting data that is not affected by turbidity or other substances with minimal impact.

[0372] As an arbitrary structure, the scanning control unit 450A can cause the scanning unit 410 to perform an OCT scan of a three-dimensional region of the examined eye E under at least one of first scanning control (first OCT scan) and second scanning control (second OCT scan). In this case, the distance calculation unit 460A can determine the feature position corresponding to the feature point of the examined eye E by analyzing the data obtained by the OCT scan of the three-dimensional region. Moreover, the distance calculation unit 460A can calculate the distance between the first part and the second part (e.g., the aforementioned provisional distance) using the length of a line segment with the feature position as one end.

[0373] As a first typical example, the scan control unit 450A can, under first scan control (first OCT scan), cause the scan unit 410 to perform an OCT scan of a three-dimensional region including the corneal surface of the examined eye E. Furthermore, the distance calculation unit 460A can determine the feature position corresponding to the corneal apex of the examined eye E by analyzing the data acquired through the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460A can calculate the distance between the first and second parts (e.g., the aforementioned provisional distance) using the length of a line segment with the corneal apex as one end.

[0374] As a second typical example, the scan control unit 450A can, under second scan control (second OCT scan), cause the scanning unit to perform an OCT scan of a three-dimensional region including the retinal surface of the examined eye E. Furthermore, the distance calculation unit 460A can determine the feature position corresponding to the macular center of the examined eye E by analyzing the data acquired through the OCT scan of this three-dimensional region. In this case, the distance calculation unit 460A can calculate the distance between the first and second portions (e.g., the aforementioned provisional distance) using the length of a line segment with the macular center as one end.

[0375] By combining the first and second typical examples, the length of the line segment with the corneal vertex as one end and the macula center as the other end can be determined, which is the axial length of the examined eye E.

[0376] As an arbitrary structure, the offset measuring unit 420 includes an alignment optical system 50 (projection system), two (or more) anterior eye cameras 300 (two or more imaging units), and an offset calculation unit 430. The alignment optical system 50 projects a light beam onto the anterior eye of the eye being examined, E. The two (or more) anterior eye cameras 300 capture images of the anterior eye of the eye being examined, E, from different directions. The offset calculation unit 430 calculates the offset of the eye being examined, E, from a predetermined reference position based on the positions of the light beam images (bright spots) drawn in the two (or more) anterior eye images acquired by the two (or more) anterior eye cameras 300.

[0377] Based on this arbitrary structure, a specific structure and processing can be provided for measuring the offset of the examined eye E from a predetermined reference position.

[0378] Furthermore, any items described in the second embodiment (structure, components, processing, operation, function, etc.) and any known items can be combined into the ophthalmic device listed in this effects section. Additionally, any items described in the first embodiment (structure, components, processing, operation, function, etc.) can be combined into the ophthalmic device listed in this effects section.

[0379] The second embodiment provides a control method for an ophthalmic device. The ophthalmic device includes a scanning unit 410 for OCT scanning of an eye E to be examined, and a deviation measuring unit 420 for measuring the deviation of the eye E from a predetermined reference position.

[0380] The control method includes a first scan control step, a second scan control step, an offset measurement step, and a distance calculation step.

[0381] The first scan control step causes the scanning unit 410 to perform an OCT scan of a first region containing a first part of the examined eye E. This OCT scan is called the first OCT scan. Furthermore, the second scan control step causes the scanning unit 410 to perform an OCT scan of a second region containing a second part of the examined eye E that is different from the first part. This OCT scan is called the second OCT scan.

[0382] The offset measurement step causes the offset measurement unit 420 to perform at least one of the steps of acquiring first offset information of the examined eye E corresponding to the first scan control and acquiring second offset information of the examined eye E corresponding to the second scan control.

[0383] The distance calculation step calculates the distance between the first part and the second part of the examined eye E based on at least one of the first offset information and the second offset information obtained through the offset measurement step, the first data obtained by the scanning unit 410 in the first scan control step, and the second data obtained by the scanning unit 410 in the second scan control step.

[0384] According to the control method of this ophthalmic device, the alignment error (offset information) in either or both of the first and second OCT scans can be obtained, and the distance can be calculated taking into account the alignment error. Therefore, the reliability of the distance measurement can be ensured.

[0385] Furthermore, any items described in the first embodiment (structure, elements, processing, action, function, etc.), any items described in the second embodiment (structure, elements, processing, action, function, etc.), and any known items can be combined into this control method.

[0386] A program can be configured to enable a computer to execute this control method. This program may, for example, include any of the aforementioned programs for operating the ophthalmic device 1A of the second embodiment or its modifications.

[0387] Alternatively, a computer-readable non-volatile storage medium storing such a program can be manufactured. This non-volatile storage medium can be of any form; examples include magnetic disks, optical disks, optical discs, and semiconductor memories.

[0388] Other matters

[0389] The above description is merely an embodiment of the present invention. Those who wish to implement the present invention can make any modifications (omissions, substitutions, additions, etc.) within the scope of the present invention.

[0390] For example, the ophthalmic device of the embodiment may include a structure for measuring the characteristics of the examined eye. Specifically, the ophthalmic device of the embodiment may include a structure for measuring the corneal radius of curvature of the examined eye. The structure for measuring the corneal radius of curvature may include the same optical system, computing system, and control system as conventional corneal shape measuring devices. As an example of a structure for measuring the corneal radius of curvature, there is a structure using a corneal disc (corneal ring) or a Placido disc (Plasido ring) disclosed by the applicant in Japanese Patent Application Publication No. 2017-063978. Alternatively, the corneal radius of curvature can also be measured by anterior ocular OCT scanning. Furthermore, the structure for measuring the corneal radius of curvature is not limited to these examples and may be a structure utilizing any known technology.

[0391] The characteristics of the examined eye that can be measured by the ophthalmic device according to the embodiments are not limited to the corneal radius of curvature. For example, the ophthalmic device according to the embodiments may include a structure for measuring the refractive power (spherical power, astigmatism power, astigmatic axis angle, etc.) of the examined eye. The structure for measuring the refractive power of the examined eye may include the same optical system, computing system, and control system as conventional refractive power measuring devices (refractometers). As an example of a structure for measuring refractive power, there is a structure disclosed by the applicant in Japanese Patent Application Publication No. 2017-063978.

[0392] In the case where the ophthalmic device in the embodiment has an ocular refractive power measurement function, the ophthalmic device uses a focal optical system 60 instead of the aforementioned disclosure, and can use the ocular refractive power measurement function to determine the focal position, so that the OCT focusing lens 43 can be moved to focus at that position.

[0393] In the aforementioned disclosures, methods using alignment markers and methods utilizing an anterior eye camera were described as applicable alignment methods, but other alignment methods may also be used. As an example of other alignment methods, methods utilizing optical sectioning exist. Furthermore, alignment methods using ophthalmic devices employing optical sectioning are disclosed, for example, in Japanese Patent Application Publication Nos. 2012-148032 and 2018-050922.

[0394] The offset measuring unit of the ophthalmic device in this example measures the offset of the examined eye relative to a predetermined reference position using optical sectioning. The predetermined reference position is, for example, a position corresponding to a travel distance, i.e., a position away from the examined eye along the z-direction from the predetermined travel distance. The measured offset is typically the offset in the z-direction.

[0395] The offset measurement unit in this example includes a projection system that projects a beam of light obliquely onto the anterior eye portion of the examined eye, and an image sensor that detects the reflected beam of the projected beam from the anterior eye portion. The structure and configuration of the projection system and image sensor are the same as those of conventional optical sectioning alignment components.

[0396] A typical projection system includes a light source and a lens. The optical axis of a typical projection system is tilted at a first angle relative to the optical axis of the measuring arm (the optical axis of the objective lens) in a first direction. A typical image sensor is a CCD image sensor or a CMOS image sensor, and is either a line sensor or a region sensor. Typically, an imaging lens is positioned between the image sensor and the eye being examined, E. The optical axis of the detection system, including the image sensor and the imaging lens, is tilted at a second angle equal to the first angle relative to the optical axis of the measuring arm in a second direction opposite to the first direction.

[0397] With this structure and configuration, the image sensor can detect the reflected light beam when the projection system and detection system are within a predetermined range relative to the eye being examined. Furthermore, if the relative position between the projection system / detection system and the eye being examined changes, the detection position of the reflected light beam by the image sensor changes. That is, in response to the relative position between the projection system / detection system and the eye being examined, the projection position of the reflected light beam onto the light-receiving area (light-receiving device array) of the image sensor changes.

[0398] The offset measurement unit in this example includes an offset calculation unit that calculates the offset of the examined eye based on the detection position of the reflected beam by the image sensor. The offset calculation unit in this example performs the same calculation as conventional optical sectioning alignment components, typically calculating the offset in the z-direction. The offset calculation unit in this example is implemented through the cooperation of hardware including circuitry and offset calculation software.

[0399] Based on this example, it is possible to provide a specific structure and process for determining the deviation of the examined eye from a predetermined reference position in the same way as in the case of using an alignment mark or using two or more anterior eye cameras.

Claims

1. An ophthalmic device comprising: The scanning unit performs optical coherence tomography (OCT) scans on the eye being examined. The moving mechanism moves at least a portion of the scanning unit; The offset measuring unit measures the offset of the examined eye from a predetermined reference position. The scanning control unit executes a first scanning control and a second scanning control. The first scanning control causes the scanning unit to perform optical coherence tomography (OCT) scanning of a first region, which includes a first part of the examined eye. The second scanning control causes the scanning unit to perform OCT scanning of a second region, which includes a second part different from the first part. The alignment control unit performs a first alignment control and a second alignment control. The first alignment control controls the moving mechanism based on the first offset information of the examined eye obtained by the offset measuring unit before the first scanning control. The second alignment control controls the moving mechanism based on the second offset information of the examined eye obtained by the offset measuring unit before the second scanning control. as well as The distance calculation unit calculates the distance between the first part and the second part based on first data acquired by the scanning unit under the first scanning control and second data acquired by the scanning unit under the second scanning control. Under the scanning control of at least the region containing the corneal apex in the first scanning control and the second scanning control, the scanning control unit causes the scanning unit to perform multiple optical coherence tomography scans. The scanning control unit performs the following controls: The scanning unit is controlled in such a way that a first scanning mode is applied to the eye being examined; The intensity of the interference signal obtained in the first scanning mode is compared with a predetermined threshold. Even if the intensity of the interference signal is less than the predetermined threshold after repeating the first scanning mode a predetermined number of times, the scanning unit is controlled to apply a second scanning mode to the eye under examination in a position different from the first scanning mode and / or in a range wider than the first scanning mode. Furthermore, control is implemented to limit the range of orientation changes of the optical scanner of the scanning unit, so that the first part and / or the second part do not leave the applicable range of the optical coherence tomography. The distance calculation unit obtains a single data point from the data set acquired through the multiple optical coherence tomography scans, wherein the intensity of the interference signal satisfies the predetermined threshold, and uses the single data point to calculate the distance.

2. The ophthalmic device according to claim 1, wherein, The scanning unit includes: An interferometric optical system includes a measuring arm for guiding measuring light to the eye under examination, and a reference arm for guiding reference light; and An arm length changing unit is disposed on at least one of the measuring arm and the reference arm, and changes the arm length under the control of the scanning control unit. The distance calculation unit calculates the difference between the first arm length applicable under the first scanning control and the second arm length applicable under the second scanning control, and parses the first data to determine the first position corresponding to the first part, parses the second data to determine the second position corresponding to the second part, and calculates the distance based on the difference, the first position and the second position.

3. The ophthalmic device according to claim 1, wherein, Under at least one of the first scan control and the second scan control, the scan control unit causes the scan unit to perform optical coherence tomography (OCT) scanning of a three-dimensional region of the examined eye. The distance calculation unit analyzes the data obtained by optical coherence tomography of the three-dimensional region, determines the feature position corresponding to the feature point of the examined eye, and calculates the distance as the length of a line segment with the feature position as one end.

4. The ophthalmic device according to claim 3, wherein, Under the first scan control, the scan control unit causes the scan unit to perform optical coherence tomography (OCT) scans of a three-dimensional region including the corneal surface of the examined eye. The distance calculation unit analyzes the data obtained from optical coherence tomography of the three-dimensional region to determine the feature position corresponding to the corneal vertex.

5. The ophthalmic device according to claim 3, wherein, Under the second scan control, the scan control unit causes the scan unit to perform optical coherence tomography (OCT) scans of a three-dimensional region including the retinal surface of the eye being examined. The distance calculation unit analyzes the data obtained from optical coherence tomography of the three-dimensional region to determine the feature location corresponding to the center of the macula.

6. The ophthalmic device according to any one of claims 1 to 5, wherein, The offset measuring unit includes: The projection system projects a light beam onto the anterior part of the eye being examined. Two or more imaging units, taking images of the anterior eye of the examined eye from different directions; and The offset calculation unit calculates the offset of the examined eye based on the position of the beam image drawn in two or more anterior eye images obtained by the two or more imaging units.

7. The ophthalmic device according to any one of claims 1 to 5, wherein, The offset measuring unit includes: The projection system projects a light beam obliquely toward the anterior part of the eye being examined. An image sensor detects the reflected beam of the light source from the anterior eye; and The offset calculation unit calculates the offset of the examined eye based on the detection position of the reflected beam by the image sensor.

8. A method for controlling an ophthalmic device, the ophthalmic device comprising: The scanning unit performs optical coherence tomography (OCT) scans on the eye being examined. The moving mechanism moves at least a portion of the scanning unit; and an offset measuring unit that measures the offset of the examined eye from a predetermined reference position, wherein the control method includes: The first alignment control step controls the moving mechanism based on the first offset information of the examined eye obtained by the offset measuring unit. The first scanning control step causes the scanning unit to perform an optical coherence tomography scan of a first region, the first region including a first part of the eye being examined; The second alignment control step controls the moving mechanism based on the second offset information of the examined eye obtained by the offset measuring unit. A second scanning control step involves causing the scanning unit to perform an optical coherence tomography scan of a second region, the second region including a second portion different from the first portion; and The distance calculation step calculates the distance between the first part and the second part based on the first data obtained by the scanning unit in the first scanning control step and the second data obtained by the scanning unit in the second scanning control step. In at least the scanning control steps containing the corneal apex in the first and second scanning control steps, the scanning unit performs multiple optical coherence tomography scans. The first scan control step and the second scan control step further include: The step of controlling the scanning unit in a manner that applies a first scanning mode to the eye being examined; The step of comparing the intensity of the interference signal obtained in the first scanning mode with a predetermined threshold; The step of controlling the scanning unit to apply a second scanning mode to the examined eye at a location different from the first scanning mode and / or in a range wider than the first scanning mode, even when the intensity of the interference signal is less than the predetermined threshold after repeating the first scanning mode a predetermined number of times; and The step of controlling the orientation variation range of the optical scanner of the scanning unit to ensure that the first part and / or the second part do not leave the applicable range of the optical coherence tomography (OCT) scan. In the distance calculation step, a single data point whose intensity of the interference signal satisfies the predetermined threshold is obtained from the data set acquired through the multiple optical coherence tomography scans, and the distance is calculated using the single data point.

9. A computer-readable non-volatile storage medium storing a program that causes a computer to perform the control method of claim 8.

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