Ophthalmological device

Abstract

An ophthalmological device according to a non-limiting embodiment of the present disclosure comprises an OCT scanner and one or more processors connected to a storage device. The OCT scanner includes an interference optical system and an optical path length changing unit. The interference optical system has a sample arm and a reference arm. The optical path length changing unit changes the optical path length of at least one of the sample arm and the reference arm. The storage device pre-stores calibration information including one or more calibration parameter values. The one or more processors generate an OCT image of an eye to be examined on the basis of data collected by the OCT scanner by applying an OCT scan to the fundus of the eye to be examined. The one or more processors receive optical path length information indicating the optical path length of the arms when the data is collected. In addition, the one or more processors calculate the intraocular distance of the eye to be examined on the basis of the calibration information, the OCT image, and the optical path length information.

Description

ophthalmology equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 642,111, entitled "METHODS FOR ESTIMATING OCULAR AXIS LENGTH," filed May 3, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to ophthalmic devices.

[0003] Various imaging modalities are used in ophthalmology practice, including fundus cameras, scanning laser ophthalmoscopy (SLO), slit lamp microscopes, and optical coherence tomography (OCT). OCT can be used for both structural and functional imaging.

[0004] OCT structural imaging is a technique for representing the spatial distribution of OCT signal intensity, which varies depending on the structure of a test object, as an image. Images generated by this technique are called OCT intensity images or simply intensity images.

[0005] OCT intensity images are used to measure eye dimensions. A typical example of dimension measurement is the measurement of a parameter (intraocular distance) defined as the distance between two different positions in the eye. There are various types of intraocular distances, such as axial length, corneal thickness, anterior chamber depth, lens thickness, and vitreous cavity depth.

[0006] OCT functional imaging is a technique that expresses changes in OCT signals according to the function of a test object as images. Applications in the field of ophthalmology include OCT angiography, which images the vascular network at the fundus of the eye, and OCT blood flow measurement, which images the dynamics of blood flow within the blood vessels at the fundus of the eye. Images generated by this technique are called OCT functional images or simply functional images.

[0007] U.S. Pat. No. 1,013,400

[0008] One non-limiting object of the present disclosure is to provide a novel intraocular distance measurement technique using OCT.

[0009] An ophthalmic device according to a non-limiting embodiment of the present disclosure includes an OCT scanner and one or more processors. The OCT scanner is configured to collect data by applying an OCT scan to a fundus of a test eye. The one or more processors are connected to a storage device. The OCT scanner includes an interference optical system and an optical path length changing unit. The interference optical system has a sample arm and a reference arm. The optical path length changing unit is configured to change the optical path length of at least one of the sample arm and the reference arm. The storage device pre-stores calibration information including one or more calibration parameter values. The one or more processors are configured to perform the following processes: generating an OCT image of the test eye based on data collected from the fundus of the test eye by the OCT scanner; receiving optical path length information indicating the optical path lengths of the arms when the data was collected; and calculating the intraocular distance of the test eye based on the calibration information, the OCT image, and the optical path length information.

[0010] Exemplary embodiments of the present disclosure can provide a novel technique for measuring intraocular distances using OCT.

[0011] FIG. 1 is a flowchart showing a usage pattern according to a non-limiting embodiment. FIG. 2 is a schematic diagram showing the configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 3 is a schematic diagram showing the configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 4 is a schematic diagram showing the configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 5 is a schematic diagram showing the configuration of an ophthalmic apparatus according to a non-limiting embodiment. FIG. 6 is a schematic diagram showing the configuration of an ophthalmic apparatus according to a non-limiting embodiment.

[0012] An exemplary embodiment according to the present disclosure will now be described.

[0013] At least a portion of the functionality of some elements of embodiments according to the present disclosure may be implemented using circuitry or processing circuitry. The circuitry or processing circuitry may be a general purpose processor, a special purpose processor, an integrated circuit, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), an Application Specific Integrated Circuit (ASIC), a programmable logic device (e.g., a Simple Programmable Logic Device (SPLD), a Complex Programmable Logic Device (CPLD), a Field Programmable Gate Array (FPGA)), or a combination of these devices configured and / or programmed to perform at least some of the disclosed functions. The term "circuitry," "unit," "means," or the like may refer to hardware that performs at least some of the disclosed functions or that is configured and / or programmed to perform at least some of the disclosed functions. This hardware may be the hardware described in this disclosure or may include known hardware and / or hardware that is configured and / or programmed to perform at least some of the functions described in this disclosure. In the case of a processor, where the hardware can be considered as a certain type of circuitry, the term "circuitry," "unit," "means," or the like may refer to a combination of hardware and software. This software can be used to configure the hardware and / or the processor.

[0014] The present disclosure provides several embodiments for measuring intraocular distances using OCT. The present disclosure also provides several embodiments that can achieve improved OCT-based ophthalmic examinations, such as improved OCT-based ophthalmic disease screening.

[0015] Two or more embodiments according to the present disclosure may be at least partially combined, and the resulting embodiment may at least partially exhibit the functions and effects of the combined embodiments.

[0016] Various imaging modalities are used in ophthalmologic disease screening. Some screening methods refer to fundus photographs obtained with a fundus camera or SLO, intensity images obtained with OCT, and functional information to evaluate the state of fundus tissue (e.g., nerve fiber layer thickness, ganglion cell layer thickness, etc.) and assess disease risk based on the results. There is a demand in medical settings for the automation of these processes. In particular, since screening involves a large number of subjects, there is a strong demand for improved efficiency through automation.

[0017] Currently, some screening facilities perform examinations using a standalone ophthalmologic device (sometimes called an OCT device) that has both a fundus photography function (e.g., a fundus camera function, an SLO function, etc.) and an OCT function. Such facilities include medical examination facilities and small-scale medical institutions. These facilities desire automated evaluation using a standalone OCT device.

[0018] Ophthalmic examinations can be affected by ocular parameters. For example, in fundus measurements using OCT, the imaging range (OCT scan area) varies depending on individual differences in ocular parameters. In optic disc measurements and retinal thickness measurements, the size of the fundus area to which the OCT scan is applied (scan size) varies depending on the axial length and ocular refractive power of the subject's eye. Generally, even if the scanning conditions (e.g., the maximum angle of deflection of the measurement light) are the same, the longer the axial length, the larger the size of the fundus area actually scanned. In many fundus measurements, OCT scans are performed with a predetermined scan size as the target. However, the size of the fundus area depicted in the actual OCT image (actual scan size) is affected by individual differences in axial length. Therefore, if the ocular parameters of the subject's eye are not taken into consideration, the quality of the fundus examination (e.g., sensitivity, specificity, accuracy, precision, reproducibility, etc.) will be reduced. This problem can become more pronounced when comparative evaluations are performed using standard values ​​(reference databases). Non-limiting examples of reference databases include a healthy eye database (normal eye database), a diseased eye database (e.g., a severe myopia database), and a real-world database.

[0019] The normal eye database is a database created from a data set collected by examining predetermined measurement indices of healthy eyes (normal eyes) that satisfy predetermined conditions under favorable conditions. For example, the normal eye database is a database created based on data collected from a large number of sample eyes whose measurement indices fall within the normal range. The diseased eye database is a database created based on measurement indices collected from a large number of sample eyes with a specific disease. Some measurement indices are any type of metric derived from data acquired by OCT scans and are used to understand and evaluate the condition of the eye. A non-limiting example of a measurement indices that is affected by ocular parameters is the distribution of fundus tissue thickness.

[0020] A real-world database is a database created based on real-world data collected without restricting attributes. Real-world data is data obtained from various sources related to outcomes of heterogeneous populations in real-world environments. Real-world data is not collected according to a specific research protocol, but rather data generated, for example, from daily clinical practice or personal health care. Real-world data is understood to be a different type of data from data obtained from randomized controlled trials. Real-world data is a dataset collected from various sample eyes that reflect reality and everyday life. Compared to normal eye datasets, real-world data are characterized by a large sample size, a wide range of values, and a large variation in the attributes of the sample eyes (e.g., age). Non-limiting examples of real-world data include electronic medical record data, medical imaging data, image interpretation data, medical fee statements, health insurance claim data, and patient surveys.

[0021] In conventional screening settings, it has been common to correct the OCT imaging range by measuring the ocular parameters of the subject's eye separately from the OCT scan. U.S. Pat. No. 1,013,400 (Patent Document 1) discloses a technique for estimating the axial length based on a reference arm length, a sample arm length, and a working distance, and determining the imaging range based on this estimated axial length. In addition, some conventional techniques define multiple ranges for the axial length, which is the ocular parameter that most affects the imaging range, prepare reference databases corresponding to each range, select a reference database according to the axial length of the subject's eye, and evaluate the subject's eye using the selected reference database.

[0022] Some embodiments of the present disclosure propose a novel method for estimating intraocular distance based on parameters of an ophthalmic device when an OCT scan is applied (e.g., an arm length of an OCT optical system), an image obtained by the OCT scan (OCT image), and calibration parameters of the ophthalmic device. The obtained estimate of intraocular distance may be used in any manner.

[0023] Axial length is one representative intraocular distance. The intraocular distance may be a distance parameter obtained by subtracting a factor corresponding to at least a portion of the anterior segment from the axial length. An example of this distance parameter is the vitreous chamber depth (VCD = AEL - (CCT + ACD)), which is obtained by subtracting the central corneal thickness (CCT) and the anterior chamber depth (ACD) from the axial length (AEL). OCT scans of the fundus are performed by deflecting the measurement light around a pivot set in or near the pupil. The vitreous chamber depth VCD is an intraocular distance that approximates the distance between the pivot and the fundus, and therefore affects the dimensions of the area of ​​the fundus to which the OCT scan is applied. The intraocular distances that can be employed are not limited to these, and may also include pupil thickness (the dimension of the pupil in the depth direction), anterior chamber depth, and crystalline lens thickness.

[0024] Some embodiments can improve the quality (sensitivity, specificity, etc.) of ophthalmic disease screening without using an ocular parameter measuring device, such as an axial length measuring device, separately from the OCT device.

[0025] Some embodiments may use the estimated intraocular distance to scale the fundus OCT image.

[0026] Some embodiments may use the estimated intraocular distance to scale measurement distribution data obtained from fundus OCT images, such as fundus tissue thickness distribution data generated by applying dimensional measurement analysis to the fundus OCT images.

[0027] Some embodiments may use the estimated intraocular distance to perform scaling to match dimensions of measurement data obtained from the fundus OCT image with dimensions of predetermined reference data, such as relative scaling between the measurement data and the reference data, or relative scaling between the fundus OCT image and the reference data, which may be, for example, a reference database.

[0028] Some embodiments may use the estimated intraocular distance to evaluate an ophthalmic disease, such as assessing the presence or absence of myopia, the degree of myopia, or changes in myopic status over time.

[0029] The present disclosure particularly describes in detail several non-limiting embodiments related to ophthalmic devices. The ophthalmic device of the present disclosure may be an ophthalmic imaging device (OCT device) with an OCT scanning function or an ophthalmic information processing device without an OCT scanning function. It will be understood by those skilled in the art that the present disclosure also provides embodiments in categories other than ophthalmic devices. For example, the present disclosure explicitly or implicitly provides embodiments of a control method for an ophthalmic device, an ophthalmic system, an OCT method, an information processing method, a medical method (e.g., an intraocular distance estimation method, an ophthalmic disease evaluation method, an ophthalmic disease screening method, an ophthalmic image analysis method, etc.), a program that causes a computer to execute each step of any of the methods, and a recording medium (a computer-readable non-transitory recording medium) on which any of the programs is recorded. The present disclosure also provides embodiments that at least partially combine embodiments of two or more categories freely selected from these various categories. Furthermore, the present disclosure provides embodiments that at least partially combine embodiments of two or more categories related to one category.

[0030] A usage pattern according to some embodiments will now be described. Fig. 1 shows a non-limiting example of this usage pattern. Fig. 2 shows a non-limiting example of the configuration of an ophthalmic device that can be employed to realize this usage pattern. Fig. 2 is a schematic diagram showing only some elements used in describing the embodiments, rather than showing all elements of an actual ophthalmic device.

[0031] The ophthalmic device 300 of this example includes an OCT scanner 310 and a processor 320. The processor 320 includes one or more processors. The processor 320 is connected to a storage device 330. The storage device 330 may be a component of the ophthalmic device 300 or may be located external to the ophthalmic device 300. Non-limiting examples of the external storage device 330 include an external storage device and a network-attached storage (NAS).

[0032] The storage device 330 stores various types of information. For example, the storage device 330 stores information related to the calibration of the ophthalmic apparatus 300. This information is called calibration information. The calibration information includes, for example, information used in the calibration and / or information obtained in the calibration. Specific examples of calibration information will be described later.

[0033] The OCT scanner 310 collects data by applying an OCT scan to the fundus of the subject's eye E. Note that the subject's eye E is not a component of the OCT scanner 310. The processor 320 executes various processes according to a program, such as control, calculation, image processing, analysis, and evaluation. The processor 320 may include a machine learning engine that executes processes using a model created using machine learning.

[0034] The OCT scanner 310 includes an interference optical system configured as a fiber optical system. The type of interference optical system is not limited to a fiber optical system, and may be a bulk optical system or a combination of a fiber optical system and a bulk optical system.

[0035] The OCT scanner 310 splits light output from a light source 311 into reference light and measurement light using a fiber coupler 312. The interference optical system has a reference arm that guides the reference light and a sample arm that guides the measurement light. The reference light is guided by the reference arm to a reference mirror 314 via a lens group 313. The reference light reflected by the reference mirror 314 is guided to the fiber coupler 312 via the lens group 313. The measurement light is guided by the sample arm to the subject's eye E via a lens 315 and an optical scanner 316. Return light of the measurement light from the subject's eye E is guided to the fiber coupler 312 via the optical scanner 316 and lens 315. The fiber coupler 312 superimposes the return light of the measurement light from the subject's eye E on the return light of the reference light from the reference mirror 314 to generate interference light. The photodetector 317 detects this interference light and generates an electrical signal (interference signal). If spectral domain OCT is employed, the photodetector 317 includes a spectrometer. If swept source OCT is employed, the photodetector 317 includes a balanced photodiode.

[0036] The processor 320 controls the OCT scanner 310, generates an image based on the interference signal from the photodetector 317, processes the image, analyzes the image, and performs evaluation processing.

[0037] The reference mirror 314 is moved by a reference mirror moving mechanism 314A. This changes the optical path length of the reference arm (reference arm length). The reference mirror moving mechanism 314A includes an actuator that operates under the control of the processor 320. This actuator is, for example, a stepping motor (pulse motor). In this way, the processor 320 can change the reference arm length by controlling the reference mirror moving mechanism 314A.

[0038] The usage mode of FIG. 1 includes a series of steps shown in steps S1 to S6.

[0039] In step S1, the ophthalmic device 300 is calibrated. Calibration is performed, for example, during manufacturing, before shipping, or during maintenance. Calibration is a process of checking the discrepancy between data acquired by the ophthalmic device 300 and reliable reference data (standard data) and adjusting elements of the ophthalmic device 300 as necessary. This ensures the accuracy of the acquired data, the reliability and consistency of the device, and compliance with quality control and regulations.

[0040] The ophthalmic apparatus 300 is calibrated using a model (called an eye model, a simulated eye, a model eye, or the like) having a shape that mimics a standard eyeball. In the calibration, first, data is collected by applying an OCT scan to the eye model using the ophthalmic apparatus 300. Next, an OCT image is generated based on the collected data.

[0041] Next, the generated OCT image (and / or collected data) is evaluated. This evaluation includes a step of determining whether the OCT image (and / or collected data) conforms to predetermined criteria. Non-limiting examples of the evaluated parameters (referred to as calibration parameters) include image brightness, image quality (noise, contrast, etc.), and the imaging position of the fundus of the model eye (simulated fundus). If it is determined that a certain calibration parameter does not conform to the criteria, the ophthalmic device 300 is adjusted (corrected) so that the calibration parameter conforms to the criteria.

[0042] As a specific example, calibration of the imaging position of a simulated fundus will be described. Generally, in a fundus OCT image, it is desirable that the fundus image be positioned within a predetermined depth range in the image frame. If the fundus image is positioned above the depth range (closer to the cornea), the edge of the fundus image, which has a downward convex shape, may extend beyond the upper edge of the image frame. Conversely, if the fundus image is positioned below the depth range, the central portion of the fundus image may extend beyond the lower edge of the image frame. In either case, a problem occurs in which the imaging range of the fundus is narrowed. To avoid such a problem, calibration is performed so that the fundus image is positioned within a predetermined depth range in the image frame.

[0043] The OCT image used for calibrating the imaging position of the simulated fundus is, for example, a B-scan image or a three-dimensional image of a model eye having a simulated fundus (simulated retina). The first step of the calibration is to detect the image of the simulated fundus by applying segmentation to the OCT image obtained by the ophthalmologic apparatus 300.

[0044] The next step is to determine the depth position in the image frame of the simulated fundus image detected from the OCT image of the model eye. The depth position is a position defined in a direction (depth direction) along the side edges (edges perpendicular to both the top and bottom edges) of the image frame. The definition of the depth position of the simulated fundus image is determined in advance. For example, the depth position of the simulated fundus image may be any of the average depth position, the shallowest position, and the deepest position of the simulated fundus image, or the depth position of a specific portion of the simulated fundus image.

[0045] The next step is to calculate the difference between the depth position of the simulated fundus image and the reference depth position. The reference depth position is a position (coordinate) in the depth direction of the image frame that is predetermined so that the simulated fundus image is positioned within the aforementioned predetermined depth range. When actually capturing an image of the subject's eye, the ophthalmic apparatus 300 automatically adjusts the optical path length of the interference optical system to visualize a retinal image of the subject's eye (e.g., an image of a specific retinal tissue, such as an image of the retinal pigment epithelium (RPE)) at the reference depth position. This automatic adjustment is a process of adjusting the optical path length of the sample arm and / or the reference arm, and is referred to as auto-Z. Furthermore, the ophthalmic apparatus 300 performs automatic tracking control to maintain the visualization state achieved by auto-Z (i.e., a state in which the retinal image of the subject's eye is visualized at the reference depth position). This automatic tracking control is a process of adjusting the optical path length of the sample arm and / or the reference arm, and is referred to as Z-lock or auto-Z-lock. For details about auto-Z and Z-lock, see U.S. Pat. No. 10,314,480.

[0046] The next step is to determine the values ​​of the optical path length parameters of the interference optical system (the optical path length parameters of the sample arm and / or the optical path length parameters of the reference arm) so as to eliminate or minimize the difference between the depth position of the simulated fundus image and the reference depth position.

[0047] The parameter value determined in this way is used as a reference value for the optical path length of the interference optical system. Information indicating this reference value is called reference optical path length information (m ０ ) The reference optical path length information for the ophthalmic apparatus 300 in FIG. 2 may include control information for an actuator of the reference mirror moving mechanism 314A that moves the reference mirror 314. For example, the reference optical path length information may be information indicating the number of steps of the stepping motor of the reference mirror moving mechanism 314A. In other words, the reference optical path length information may be information indicating the number of pulses included in a control signal applied from the processor 320 to the stepping motor of the reference mirror moving mechanism 314A. Another example of the reference optical path length information may be information indicating the position of the reference mirror 314. The reference optical path length information is a non-limiting example of a parameter value (calibration parameter value) determined by calibration. The reference optical path length information is stored in the storage device 330 as one piece of calibration information.

[0048] The information indicating the reference depth position is referred to as reference depth position information (z ０ ) The reference depth position information is used as a target depth position at which a retinal image is positioned in Auto-Z. The reference depth position information may be information indicating the coordinates of a pixel in an OCT image (coordinates in the depth direction). The reference depth position information is a non-limiting example of a calibration parameter value. The reference depth position information is stored in the storage device 330 as one piece of calibration information.

[0049] The reference mirror moving mechanism 314A (and the processor 320 that controls it) that moves the reference mirror 314 is a non-limiting example of an element (optical path length changing unit) that changes the optical path length of the interference optical system (the reference arm in this example). As described above, the reference optical path length information may be expressed as information indicating the number of steps of the stepping motor of the reference mirror moving mechanism 314A (i.e., information indicating the number of pulses included in the control signal applied from the processor 320 to the stepping motor of the reference mirror moving mechanism 314A). In a non-limiting example, the information indicating the optical path length of the interference optical system (sample arm and / or reference arm) may be expressed as the number of steps of the optical path length changing operation performed by the optical path length changing unit (i.e., as the number of pulses included in the control signal of the processor 320 to the optical path length changing unit). The operating distance corresponding to one step of the stepping motor is called the step size, and the information indicating the step size is called step size information (m ｓｔｅｐ ) The step size corresponds to the unit step angle (basic step angle) and the unit movement distance of the reference mirror 314. By multiplying the step size by the number of steps, it is possible to determine the movement distance of the reference mirror 314, the position of the reference mirror 314 after the movement, and the rotation angle of the stepping motor. The step size information is stored in the storage device 330 as one piece of calibration information.

[0050] In some non-limiting examples, information indicating a position in an OCT image may be expressed as pixel coordinates (pixel position). For example, as described above, reference depth position information may be expressed as pixel coordinates (coordinates in the depth direction) in an OCT image. Information indicating the actual dimensions (resolution) corresponding to one pixel of an OCT image is called resolution information. In particular, information indicating the actual dimensions in the depth direction (depth resolution) corresponding to one pixel is called depth resolution information (z ｓｔｅｐ) The actual distance in the depth direction can be calculated by multiplying the depth resolution by the number of pixels arranged in the depth direction. The depth resolution information is stored in the storage device 330 as one piece of calibration information. The actual dimensions are values ​​obtained by converting the dimensions in the image space (pixel space) of the OCT image into dimensions in real space. Similarly, the actual distance is a value obtained by converting the distance in image space into distance in real space. The actual distance is also called the physical distance, real-world distance, etc.

[0051] The calibration information may include information about the eye model (calibration eye model) used to calibrate the ophthalmic device 300. This information is referred to as eye model information. The eye model information may include values ​​of any type of ocular parameters. In some non-limiting examples, the eye model information may include information (reference intraocular distance information) indicating a value of a predetermined intraocular distance (reference intraocular distance) in the calibration eye model. The reference intraocular distance information may include, for example, reference axial length information indicating a value of the axial length (reference axial length) in the calibration eye model, reference corneal thickness information indicating a value of the corneal thickness (reference corneal thickness), reference anterior chamber depth information indicating a value of the anterior chamber depth (reference anterior chamber depth), reference lens thickness information indicating a value of the lens thickness (reference lens thickness), and reference vitreous cavity depth information indicating a value of the vitreous cavity depth (reference vitreous cavity depth).

[0052] As described above, in step S1, the ophthalmic apparatus 300 is calibrated using the calibration eye model, calibration information is generated based on information used for the calibration and information obtained by the calibration, and the generated calibration information is stored in the storage device 330 of the ophthalmic apparatus 300. After step S1, steps S2 to S6 are performed during medical treatment in a medical setting.

[0053] In step S2, the scan conditions of the ophthalmic apparatus 300 are adjusted according to the subject's eye E. The scan conditions are various conditions set for an OCT scan. Non-limiting examples of the scan conditions include a scan pattern (e.g., B-scan, raster scan, Lissajous scan, cross scan, multi-cross scan, radial scan, etc.), adjustment of the optical path length of the interference optical system (in this example, adjustment of the position of the reference mirror 314), diopter adjustment, alignment, focusing, etc. The adjustment of the scan conditions may be performed in a conventional manner. At least a part of the adjustment of the scan conditions may be automated. For example, adjustment of the optical path length, alignment, focusing, etc. are automated in many ophthalmic apparatuses.

[0054] In step S3, the OCT scanner 310 applies an OCT scan to the fundus of the subject's eye E under the scan conditions set in step S2 to collect data. The collected data is sent to the processor 320.

[0055] In step S4, the processor 320 saves the scan conditions used in the OCT scan in step S3 in the storage device 330. The saved scan conditions may be the scan conditions set in step S2 and / or the scan conditions obtained by further adjustments performed during the OCT scan in step S3. The saved scan conditions include at least information indicating the optical path length of the interference optical system applied during the OCT scan in step S3 (optical path length information).

[0056] In step S5, the processor 320 generates an OCT image based on the data collected from the fundus of the subject's eye E in step S3. This OCT image generation may be performed by conventional signal processing. The processor 320 associates the scan conditions saved in step S4 with the OCT image saved in step S5. This association is performed using, for example, an identifier of the subject (subject ID) and an identifier of the subject's eye E (information indicating the right eye or the left eye).

[0057] The step of saving the scan conditions and the step of generating and saving the OCT image may be performed in reverse order, or at least a part of the step of saving the scan conditions and at least a part of the step of generating and saving the OCT image may be performed in parallel.

[0058] At the stage when step S5 is completed, the storage device 330 stores the calibration information saved in step S1, the scan conditions saved in step S4, and the OCT image saved in step S5.

[0059] In step S6, the processor 320 reads the calibration information, the scan conditions for the subject's eye E, and the OCT image from the storage device 330. The processor 320 receives from the storage device 330 optical path length information indicating at least the optical path length of the interference optical system applied during the OCT scan in step S3. The processor 320 calculates the intraocular distance of the subject's eye E based on the calibration information, the scan conditions, and the OCT image. The method for calculating this intraocular distance may be any method, and may be performed using a pre-prepared arithmetic expression, a model constructed using machine learning (a machine learning engine), or a combination of the arithmetic expression and a machine learning engine, for example.

[0060] Some non-limiting aspects of the embodiment shown in Figures 1 and 2 are described below.

[0061] The ophthalmic device 300 includes an OCT scanner 310 that applies an OCT scan to the fundus of the subject's eye 3 to collect data, and a processor 320 connected to a storage device 330. The processor 320 includes one or more processors. The OCT scanner 310 includes an interference optical system having a reference arm formed by a group of elements including a lens group 313 and a reference mirror 314, and a sample arm formed by a group of elements including a lens 315 and an optical scanner 316. The OCT scanner 310 further includes a reference mirror moving mechanism 314A that changes the optical path length of the reference arm. The reference mirror moving mechanism 314A is one exemplary example of an optical path length changing unit. More generally, the optical path length changing unit is configured to change the optical path length of at least one of the sample arm and the reference arm. The storage device 330 pre-stores calibration information including one or more calibration parameter values. The processor 320 generates an OCT image of the subject's eye E based on data collected from the OCT scanner 310 (OCT image generation processing). The processor 320 also receives optical path length information indicating the optical path length of the interference optical system (in this example, the optical path length of the reference arm) when data was collected from the subject's eye E by the OCT scanner 310 (optical path length information reception processing). The optical path length information may be provided, for example, from the OCT scanner 310 (in this example, the reference mirror moving mechanism 314A, a position sensor (not shown) that detects the position of the reference mirror 314, etc.) or from an optical path length change control (in this example, a module within the processor 320 that controls the reference mirror moving mechanism 314A). Furthermore, the processor 320 calculates the intraocular distance of the subject's eye E based on the calibration information stored in the storage device 330, the generated OCT image, and the received optical path length information (intracorporeal distance calculation processing). The intraocular distance calculated by the ophthalmic apparatus 300 may be any type of distance that can be calculated using the optical path length of an interference optical system, and non-limiting examples thereof include the axial length, corneal thickness, anterior chamber depth, lens thickness, and vitreous cavity depth. The ophthalmic apparatus 300 configured in this manner provides a novel intraocular distance measurement technology that uses OCT. Some non-limiting examples of the characteristics (actions, effects, advantages, possible uses, applicability, etc.) of this novel technology will be described below.

[0062] In some non-limiting aspects, the calibration information includes reference optical path length information indicating a reference value of the optical path length of the interference optical system. The reference optical path length information includes at least a reference value of the optical path length of an arm whose optical path length is variable. The calibration information of the ophthalmic device 300 according to this aspect includes a reference value of the optical path length of the reference arm. As described above, the reference optical path length information (reference value of the optical path length of the reference arm) included in the calibration information of the ophthalmic device 300 is referred to as "m ０ The optical path length information received in the optical path length information receiving process is indicated by "m." In the intraocular distance calculation process, the processor 320 of this embodiment calculates the optical path length information (m) and the reference optical path length information (m ０ ) and the difference (Δm = mm ０ ) is calculated. This difference Δm is called first difference information. The processor 320 calculates the intraocular distance of the subject's eye E using this first difference information Δm. That is, the processor 320 calculates the intraocular distance of the subject's eye E based on at least the first difference information and the OCT image. The calculation of this aspect is carried out, for example, using at least the reference optical path length information (m ０ This is performed by substituting at least the optical path length information (m) and a value obtained from the OCT image into a predetermined arithmetic expression containing the reference optical path length information (m) as a constant. This aspect provides an example of a process for calculating the intraocular distance based on the calibration information, the OCT image, and the optical path length information. ０ ) is applicable.

[0063] In some non-limiting aspects, optical path length information (m) of the interference optical system when data is collected from the subject's eye E by the OCT scanner 310 and reference optical path length information (m) included in the calibration information stored in the storage device 330 ０ ) are expressed as the number of steps in changing the optical path length of the interference optical system by the reference mirror moving mechanism 314A (optical path length changing unit). Furthermore, the calibration information of this aspect includes step size information (m ｓｔｅｐIn the intraocular distance calculation process, the processor 320 of this embodiment uses the number of steps (m) indicated by the optical path length information and the number of steps (m) indicated by the reference optical path length information. ０ ) and the difference step number (Δm = mm ０ ) as the first difference information; and ｓｔｅｐ ) to convert the difference step number (Δm) into an actual distance (first distance D1=m ｓｔｅｐ ×Δm) and a third calculation to calculate the intraocular distance of the subject's eye E using the first distance D1. In the third calculation, the processor 320 calculates the intraocular distance of the subject's eye E based on at least the first distance D1 and the OCT image. The series of calculations performed in this mode includes, for example, at least the reference optical path length information (m ０ ) and step size information (m ｓｔｅｐ This is performed by substituting at least the optical path length information (m) and a value obtained from the OCT image into a predetermined arithmetic expression containing the reference optical path length information (m) as a constant. This aspect provides an example of a process for calculating the intraocular distance based on the calibration information, the OCT image, and the optical path length information. ０ ) and step size information (m ｓｔｅｐ ) is applicable when

[0064] In some non-limiting aspects, the calibration information includes reference depth position information indicating a reference depth position in an OCT image. The reference depth position is a position in an image frame that is set in a calibration operation as a suitable imaging position for a retinal image. In an ophthalmic device capable of executing Auto-Z, the reference depth position information is used as a target depth position for a retinal image by Auto-Z. As described above, the reference depth position information included in the calibration information of the ophthalmic device is referred to as "z ０ In the intraocular distance calculation process, the processor 320 of this embodiment analyzes an OCT image generated based on data collected from the subject's eye E to obtain depth position information indicating the depth position of a predetermined portion of the fundus of the subject's eye E. This depth position information is indicated by "z." Furthermore, the processor 320 calculates the depth position information (z) and the reference depth position information (z ０ ) and the difference (Δz = z − z ０) is calculated. This difference Δz is called second difference information. The processor 320 calculates the intraocular distance of the subject's eye E using the second difference information Δz. That is, the processor 320 calculates the intraocular distance of the subject's eye E based on at least the second difference information and the optical path length information. The calculation of this aspect is carried out, for example, using at least the reference depth position information (z ０ This is performed by substituting at least the depth position information (z) and the optical path length information (m) into a predetermined arithmetic expression containing the reference depth position information (z) as a constant. This aspect provides an example of a process for calculating the intraocular distance based on the calibration information, the OCT image, and the optical path length information. ０ ) is applicable.

[0065] In some non-limiting aspects, the depth position information (z) obtained from the OCT image of the subject's eye E and the reference depth position information (z) included in the calibration information stored in the storage device 330 are used. ０ ) are expressed as pixel positions in the OCT image (image frame). Furthermore, the calibration information of this aspect includes depth resolution information (z ｓｔｅｐ In the intraocular distance calculation process, the processor 320 of this embodiment further includes a pixel position (z) indicated by the depth position information and a pixel position (z) indicated by the reference depth position information. ０ ) and the difference pixel position (Δz = z - z ０ ) as the second difference information, and ｓｔｅｐ ) to convert the difference pixel position (Δz) into an actual distance (second distance D2=z ｓｔｅｐ ×Δz) and a third calculation to calculate the intraocular distance of the subject's eye E using the second distance D2. In the third calculation, the processor 320 calculates the intraocular distance of the subject's eye E based on at least the second distance D2 and the optical path length information. The series of calculations performed in this mode includes, for example, at least the reference depth position information (z ０ ) and depth resolution information (z ｓｔｅｐThis is performed by substituting at least the depth position information (z) and the value of the optical path length information (or a value obtained from the optical path length information) into a predetermined arithmetic expression including the reference depth position information (z) as a constant. This aspect provides an example of a process for calculating the intraocular distance based on the calibration information, the OCT image, and the optical path length information, and the calibration information is used as the reference depth position information (z). ０ ) and depth resolution information (z ｓｔｅｐ ) is applicable when

[0066] In some non-limiting aspects, the ophthalmic apparatus 300 is configured to be able to perform auto Z and Z lock. The auto Z and Z lock are performed in a conventional manner under the control of the processor 320. Briefly, the processor 320 controls the scan control to control the OCT scanner 310 to repeatedly scan the fundus of the subject's eye E to repeatedly collect data, and to determine whether a predetermined portion of the fundus (e.g., the RPE) is at a reference depth position (z ０ ) is displayed. The scan control is a control for acquiring a live OCT image (OCT observation image), and the scan pattern applied is typically a B scan. By this combined control, the reference depth position (z ０ A live OCT image is obtained in which a predetermined portion of the fundus is continuously depicted at a depth position at or near the reference depth (D2). The OCT scanner 310, under the control of the processor 320, applies an OCT scan to the fundus of the subject's eye E to collect data during or after execution of the combined control. The processor 320 generates an OCT image of the subject's eye E based on the data collected by the OCT scan. The processor 320 can calculate the intraocular distance of the subject's eye E using the OCT image in which the fundus is depicted at a suitable depth position. This aspect provides an example of a process for calculating the intraocular distance based on calibration information, an OCT image, and optical path length information, and is applicable when the ophthalmic apparatus has auto-Z and Z-lock functions.

[0067] In some non-limiting aspects, the processor 320 may perform the following series of processes using depth position information (z) from the OCT image of the subject's eye E. The processor 320 of this aspect performs a process (segmentation) of analyzing the OCT image of the subject's eye E to identify an image of a predetermined portion of the fundus, and a calculation to calculate an average depth position of the image of the identified predetermined portion. This average depth position may be, for example, the average value of the depth coordinates of a group of pixels that make up the image of the predetermined portion. In this aspect, the average depth position thus obtained is used as the depth position information (z). The processor 320 of this aspect calculates the average depth position (z) and the reference depth position information (z) by using the average depth position (z) and the reference depth position information (z). ０ ) is obtained, and the intraocular distance of the subject's eye E is calculated based on at least this second difference information (z) and the optical path length information. This aspect provides an example of a process for calculating the intraocular distance based on the calibration information, the OCT image, and the optical path length information, and in particular provides an example of a process for obtaining depth position information (z).

[0068] In some non-limiting aspects, the calibration information includes reference intraocular distance information indicating a reference intraocular distance in a calibration model eye. The reference intraocular distance information may be any type of intraocular distance value, but in some examples, the reference intraocular distance information may be a reference axial length (AL) ０ ) The processor 320 of this embodiment calculates the intraocular distance of the subject's eye E based on calibration information including reference intraocular distance information, an OCT image, and optical path length information. The calculation of this embodiment is performed, for example, by substituting at least the optical path length information (m) and a value obtained from the OCT image into a predetermined arithmetic expression including at least the reference intraocular distance information as a constant. This embodiment provides one example of a process for calculating the intraocular distance based on calibration information, an OCT image, and optical path length information, and is applicable when the calibration information includes reference intraocular distance information.

[0069] The aspect described next is a combination of several of the above aspects. The calibration information of this aspect is reference optical path length information (m ０ ) and reference depth position information (z ０) and reference axial length information (AL ０ In this embodiment, the optical path length information (m) and the reference optical path length information (m ０ ) are expressed as the number of steps in changing the optical path length of the reference arm by the reference mirror moving mechanism 314A (optical path length changing unit). Also, the reference depth position information is expressed as a pixel position in the OCT image. Furthermore, the calibration information of this aspect includes step size information (m ｓｔｅｐ ) and depth resolution information (z ｓｔｅｐ In the intraocular distance calculation process, the processor 320 executes a series of processes described below. First, the processor 320 calculates the number of steps m indicated by the optical path length information and the number of steps m indicated by the reference optical path length information. ０ Calculate the difference step number Δm, which is the difference between ０ Next, the processor 320 calculates the difference step number Δm by adding the step size information m ｓｔｅｐ to calculate the first distance D1: D1=m ｓｔｅｐ ×Δm. The processor 320 also analyzes the OCT image of the subject's eye E to obtain depth position information z indicating a pixel position corresponding to the depth position of a predetermined portion of the fundus. Next, the processor 320 compares the pixel position z indicated by the depth position information with the pixel position z indicated by the reference depth position information. ０ Calculate the difference pixel position Δz, which is the difference between ０ Next, the processor 320 calculates the depth resolution information z ｓｔｅｐ to calculate the second distance D2: D2 = z ｓｔｅｐ ×Δz. Furthermore, the processor 320 calculates the first distance D1, the second distance D2, and the reference axial length AL ０ The axial length (estimated value) AL of the subject eye E is calculated by adding ｅｓｔ Calculate: AL ｅｓｔ = D1 + D2 + AL ０ The axial length estimation in this embodiment is carried out, for example, using reference optical path length information m ０ and step size information m ｓｔｅｐand reference depth position information z ０ and depth resolution information z ｓｔｅｐ and the reference axial length AL ０ This is performed by substituting the optical path length information m and the depth position information z into the following equation, which includes the following as constants: AL ｅｓｔ = m ｓｔｅｐ × (mm ０ ) + z ｓｔｅｐ ×(z-z ０ ) + AL ０ This aspect provides an example of a process for calculating the intraocular distance based on calibration information, an OCT image, and optical path length information, and is applicable to a case where the calibration information includes reference optical path length information, step size information, reference depth position information, depth resolution information, and reference axial length.

[0070] In some non-limiting embodiments, the storage device 330 stores an arbitrary OCT image of the subject's eye E. This OCT image may be the OCT image used to calculate the intraocular distance or a different OCT image. This OCT image may be generated by the ophthalmic device 300 or a different device. The processor 320 of this embodiment scales this OCT image based on the intraocular distance of the subject's eye E. This scaling is a process of enlarging or reducing the image depicted in the OCT image. Scaling changes the resolution of the OCT image (the actual size corresponding to one pixel). As described above, even when OCT scans are performed under the same scanning conditions (particularly, the maximum deflection angle of the measurement light), the size of the fundus region depicted in the resulting OCT image (the actual scan size) depends on the axial length of the subject's eye. The relationship between the axial length and the scan size when the maximum deflection angle of the measurement light is constant can be calculated and is known. By using predetermined information (relationship information) in which this relationship is recorded, the processor 320 can scale the OCT image of the subject's eye E based on the calculated axial length of the subject's eye E. By using an OCT image with corrected scale, comparative observation, diagnosis, and analysis can be optimized. The same applies when an intraocular distance other than the axial length is used.

[0071] In some non-limiting aspects, the storage device 330 stores distribution data of predetermined measurement values ​​at the fundus of the subject's eye E. The distribution data may be generated, for example, based at least on data collected from the fundus of the subject's eye E by an OCT scan, or based at least on an OCT image generated from the collected data. The distribution data may be data representing any type of measurement value in any form. A non-limiting example of the distribution data is fundus tissue thickness distribution data. The processor 320 of this aspect scales the distribution data based on the intraocular distance of the subject's eye E. The scaling of this aspect is a process of expanding or reducing the arrangement interval of data groups recorded in the distribution data. Similar to the scaling of the OCT image described above, the processor 320 can scale the distribution data of the subject's eye E based on the above-mentioned relationship information and the calculated axial length of the subject's eye E. Using the scale-corrected distribution data allows for optimal comparison of the distribution data and for optimal diagnosis and analysis. The same applies when an intraocular distance other than the axial length is used.

[0072] In some non-limiting embodiments, the storage device 330 stores measurement data obtained from an OCT image of the fundus of the subject's eye E and pre-created reference data. The measurement data includes, for example, one or more measurement values ​​for any type of parameter generated from any OCT image of the subject's eye E. The reference data includes one or more reference values ​​for the same type of parameter as the measurement data. In a non-limiting example, the measurement data is fundus tissue thickness distribution data, and the reference data is a reference database (reference data set) showing a standard distribution of fundus tissue thickness. The processor 320 of this embodiment performs relative scaling between the measurement data and the reference data based on the intraocular distance of the subject's eye E. This relative scaling changes the scale of at least one of the measurement data and the reference data so that the scale of the measurement data matches the scale of the reference data. The processor 320 evaluates the measurement data by comparing the measurement data to which this relative scaling has been applied with the reference data. This can improve the quality of the evaluation.

[0073] In some non-limiting aspects, the processor 320 performs myopia evaluation based on the calculated intraocular distance of the subject's eye E. The intraocular distance threshold for distinguishing between myopic eyes and normal eyes and the intraocular distance threshold for distinguishing the degree of myopia are set in advance. The processor 320 determines the presence or absence of myopia and the degree of myopia by comparing the value of the intraocular distance (e.g., axial length) of the subject's eye E with these thresholds. This can improve the quality of the evaluation of myopia (particularly axial myopia).

[0074] The ophthalmic apparatus 300 described above is an ophthalmic imaging modality including an OCT scanner 310 that applies an OCT scan to the subject's eye E. In contrast, an ophthalmic apparatus according to some embodiments is an ophthalmic information processing apparatus that does not include an OCT scanner. This ophthalmic information processing apparatus may be, for example, a computer configured to operate in conjunction with the ophthalmic imaging modality, a computer connectable to the ophthalmic imaging modality via a local area network (LAN), or a computer connectable to the ophthalmic imaging modality via a wide area network (WAN), or a combination thereof. Two non-limiting aspects of an embodiment of an ophthalmic apparatus that functions as such an ophthalmic information processing apparatus are described below. Unless otherwise specified, any of the features related to the ophthalmic apparatus 300 described above may be applied, at least in part, to these non-limiting aspects.

[0075] A first aspect of an ophthalmic apparatus functioning as an ophthalmic information processing apparatus will be described with reference to FIG. 3 . The ophthalmic apparatus 400 according to this aspect includes a processor 420. The processor 420 includes one or more processors. The processor 420 is connected to a storage device 430. The storage device 430 may be an element of the ophthalmic apparatus 400 or may be located outside the ophthalmic apparatus 400. The storage device 430 stores calibration information related to the ophthalmic apparatus 400. The calibration information according to this aspect may be the same as the calibration information related to the ophthalmic apparatus 300 described above.

[0076] Reference numeral 450 in Fig. 3 denotes an ophthalmic OCT apparatus. The ophthalmic OCT apparatus 450 is a separate apparatus from the ophthalmic apparatus 400. The ophthalmic OCT apparatus 450 has a configuration similar to that of the OCT scanner 310 described above. That is, the ophthalmic OCT apparatus 450 includes an interference optical system having a sample arm and a reference arm, and collects data by applying an OCT scan to the fundus of the subject's eye. At least one of the sample arm and the reference arm is configured to change its optical path length.

[0077] Data collected from the subject's eye by the ophthalmic OCT device 450 through OCT scanning and optical path length information indicating the optical path length of the interference optical system when the data was collected are provided directly or indirectly from the ophthalmic OCT device 450 to the ophthalmic device 400. The processor 420 of the ophthalmic device 400 stores the collected data and the optical path length information in the storage device 430. The processor 420 generates an OCT image based on the collected data provided from the ophthalmic OCT device 450 (OCT image generation processing). The processor 420 also receives the optical path length information (optical path length information reception processing). The processor 420 then calculates the intraocular distance of the subject's eye based on the calibration information stored in the storage device 430, the generated OCT image, and the received optical path length information (intraocular distance calculation processing). The ophthalmic device 400 configured in this manner provides a novel intraocular distance measurement technique using OCT.

[0078] A second aspect of an ophthalmic apparatus functioning as an ophthalmic information processing device will now be described. As with the first aspect, reference will be made to FIG. 3 . The ophthalmic apparatus 400 according to this aspect includes a processor 420 connected to a storage device 430. The storage device 430 stores calibration information related to the ophthalmic apparatus 400. The ophthalmic OCT apparatus 450 applies an OCT scan to the fundus of the subject's eye to collect data and generates an OCT image based on the collected data. The OCT image of the subject's eye generated by the ophthalmic OCT apparatus 450 and optical path length information indicating the optical path length of the interference optical system when the OCT scan is applied to the subject's eye are provided directly or indirectly from the ophthalmic OCT apparatus 450 to the ophthalmic apparatus 400. The processor 420 of the ophthalmic apparatus 400 receives the OCT image of the subject's eye and the optical path length information (information reception processing). Furthermore, the processor 420 calculates the intraocular distance of the subject's eye based on the calibration information stored in the storage device 430, the OCT image of the subject's eye, and the optical path length information (intraocular distance calculation process). The ophthalmic apparatus 400 configured in this manner provides a novel intraocular distance measurement technique that uses OCT.

[0079] Next, various matters related to the embodiments of the present disclosure will be described based on U.S. Provisional Patent Application No. 63 / 642,111, which is the basis of the present disclosure. Although matters related to the axial length will be mainly described below, those skilled in the art will understand that similar matters can be applied to other intraocular distances.

[0080] Axial length and other aspects of the eye affect OCT measurements. While techniques for performing corrections using axial length values ​​measured using dedicated in vivo eye measurement devices are known, these values ​​are often unavailable when analyzing OCT images. This disclosure relates to a technique for estimating intraocular distance from metadata and image data of an ophthalmic device. This disclosure also relates to a method for utilizing estimated values ​​of intraocular distance. A robotic OCT device can be configured that automatically positions the center of rotation (pivot position) of the OCT measurement beam on the pupil plane using estimated values ​​of intraocular distance. Using this robotic OCT device, robust measurements can be provided for many in vivo eyes.

[0081] The present disclosure provides techniques for estimating biometric parameters based on information obtained from robotic or non-robotic OCT devices, and further provides techniques for using the information to improve the quality of OCT data analysis. For example, the present disclosure provides a description of using metadata obtained in an OCT scan (data collection) to obtain an estimate of axial length, using the estimate of axial length to improve screening for eye diseases such as glaucoma, obtaining estimates of other biometric parameters (e.g., corneal curvature), and using the estimated biometric information as input for other estimation processes (e.g., disease detection, feature detection).

[0082] The inventors first investigated the correlation between the reference mirror position of the interference optical system and the value of axial length. OCT scans and axial length measurements were applied to a large number of sample eyes, and a calculation formula for axial length estimation was derived based on these results. Linear fitting was also performed using the reference mirror position and axial length. It was found that using these results resulted in a large range of axial length values ​​corresponding to any reference mirror position, making the calculation impractical. This was thought to be due to the fact that only the reference mirror position was considered. Based on this consideration, the inventors adopted an approach in which the calculation formula was fitted using the corresponding OCT scans, biometric measurements, and OCT data, and also used data handled in the calibration of the device (calibration information) and data at the time of the OCT scan (scanning conditions). The inventors further investigated the correlation between the depth position of the retinal tissue image in the OCT image in addition to the reference mirror position. As a result, the aforementioned calculation formula for axial length estimation, "AL ｅｓｔ = m ｓｔｅｐ × (mm ０ ) + z ｓｔｅｐ ×(z-z ０ ) + AL ０ " was derived. The first term on the right side of the formula, "m ｓｔｅｐ × (mm ０ ) is related to the reference mirror position. ｓｔｅｐ ×(z-z ０) refers to the depth position of the retinal tissue image in the OCT image. The instrument was calibrated in air, and the distance was converted to a value in the ocular tissue using a predetermined refractive index value (1.34618).

[0083] Furthermore, the inventors verified the derived axial length estimation formula. To this end, two datasets were prepared. The first validation dataset consisted of 232 OCT scan data and axial length measurements collected from a group of healthy eyes at three U.S. facilities participating in a prospective clinical trial of the applicant's OCT device product. The second validation dataset consisted of 11,360 OCT scan data and axial length measurements collected from a group of healthy eyes and pathological eyes during annual health checkups conducted at a corporate health checkup center in Japan. The axial length measurements in both validation datasets were obtained using an axial length measurement device. Furthermore, eyes with an axial length of less than 18 mm were excluded from the second validation dataset. From each OCT scan data included in these validation datasets, an axial length estimation formula was used to calculate an axial length estimate (AL). ｅｓｔ ) was calculated, and the correspondence between the measured axial length and the estimated axial length was plotted to calculate the root mean square error (RMSE). As a result, it was confirmed that the error of this axial length estimation formula was stable and sufficiently small. The inventors also conducted verification using parameters other than axial length. For example, when the relationship between the distance between the macula and the optic disc (macular-optic disc distance) and the estimated axial length obtained using the axial length estimation formula was verified, no significant correlation was found. From the above, it is believed that the axial length estimation formula derived by the inventors is useful for estimating axial length.

[0084] Several non-limiting aspects of how the axial length estimate obtained by the axial length estimation formula derived by the inventors can be used will be described. One aspect is the improvement of glaucoma screening. Measurement of retinal tissue layer thickness is very important in clinical diagnosis. For example, glaucoma is detected by comparing the retinal tissue layer thickness of the subject eye with a reference database (RDB). This reference database is often a database of normal eyes. Glaucoma diagnosis software evaluates the magnitude of retinal tissue layer thickness. Some software compares the retinal tissue layer thickness of the subject to be evaluated with the reference database to determine a percentile value, and evaluates this percentile value on a three-level scale. The evaluation results are presented in colors: green (5% or more), yellow (1% to less than 5%), and red (less than 1%).

[0085] In such glaucoma evaluations, anatomical structures such as axial length affect the measurement data of retinal tissue layer thickness. For example, eyes with a long axial length (myopic eyes) tend to be evaluated as yellow or red. This is because when an OCT scan targeting a fundus area of ​​a predetermined size (e.g., 6 mm x 6 mm) is applied to an eye with a long axial length, a wider area (e.g., 6.3 mm x 6.3 mm) is scanned. In this case, without dimensional correction (magnification correction), the obtained layer thickness value may be smaller than the actual value, resulting in a false positive. Note that typical reference databases do not reflect a wide range of anatomical structures, and individual differences such as axial length are often ignored by averaging.

[0086] Several non-limiting aspects for improving glaucoma screening are described. Some aspects may apply magnification correction (dimension correction) to OCT data (OCT images, analysis data, etc.) using an estimated axial length. The inventors created a reference database of normal eyes (normal eye database) and a reference database with axial length correction (corrected axial length database) from a reference database containing 398 OCT scan data sets acquired in clinical trials of the applicant's OCT device product. 2,119 real-world data sets (OCT scan data sets) examined at an imaging center were used as the test dataset for normal eyes, and normal peripapillary retinal nerve fiber layer thickness (normal cpRNFL thickness) and peripapillary retinal nerve fiber layer thickness with axial length correction (corrected axial length cpRNFL thickness) were determined. The corrected axial length cpRNFL thickness was generated by replacing the default value of axial length (24.39 mm) with the estimated value. As a result, it was confirmed that the percentage of 2,119 test data judged as yellow (1% or more and less than 5%) or red (less than 1%) was lower when axial length correction was performed than when no correction was performed, which confirmed that false positives in glaucoma screening were reduced and specificity was improved.

[0087] Some embodiments can identify eyes with high axial myopia (HAM) using axial length estimates and create a reference database of eyes with high axial myopia (HAM reference database). The HAM-RDB can be used for glaucoma screening. The inventors prepared a test dataset (HAM test dataset) including eyes with high axial myopia but not glaucoma (normal HAM eyes) and eyes with high axial myopia and glaucoma (glaucomatous HAM eyes). A conventional reference database installed in the applicant's OCT device product and the HAM reference database were applied to this test dataset. The evaluation was performed considering four summary parameters: total cpRNFL thickness, superior quadrant (SQ) cpRNFL thickness, inferior quadrant (IQ) cpRNFL thickness, and temporal quadrant (TQ) cpRNFL thickness. The criteria were whether any one of these four was yellow (1% to less than 5%) or red (less than 1%). The results of this test confirmed that using the HAM reference database reduced false positives and improved specificity in myopic glaucoma screening.

[0088] The inventors also investigated anatomical parameters other than axial length. The optical path length of the interference optical system of an OCT device (e.g., the position of the reference mirror) varies depending on parameters other than axial length. Such parameters include the corneal curvature radius (K1, K2), the anterior chamber depth, and the lens thickness. It is also possible to correct OCT data using such additional parameters in addition to axial length. If these additional parameters can be estimated, the accuracy of the correction can be further improved.

[0089] By incorporating the estimated parameters into a machine learning model, it is possible to predict the presence or absence of diseases of interest (e.g., arteriosclerosis, diabetes, hypertension) or features associated with long-axis eyes (e.g., myopic choroidal neovascularization, staphyloma, lacquer cracks). Furthermore, tracking biometric parameters over time as myopia progresses may provide useful information for managing and preventing myopia progression. If the estimates obtained using OCT are sufficiently accurate, clinicians can track the biometric values ​​along with their impact on retinal nerve fiber layer thickness and other important parameters. Furthermore, biometric parameters can be estimated by incorporating OCT device parameters into a machine learning model.

[0090] Some embodiments are capable of generating a life-size 3D fundus map. A typical axial length estimate is calculated based on the central or average depth position of the retinal pigment epithelium (RPE) in an OCT image. Meanwhile, the fundus shape can be determined from 3D OCT scan data, and additional scan corrections can be applied to represent the fundus shape in life-size. Furthermore, the axial length estimate is expressed as an absolute value only for the central region of the fundus. By correcting the peripheral region using the axial length estimate in the central region, it is possible to determine the curvature of the peripheral region and create an axial length map (intracorporeal distance map).

[0091] The ophthalmic apparatus according to some embodiments has a function of collecting data by applying an OCT scan to a subject's eye, a function of generating an OCT image from the collected data, and a function of calculating an intraocular distance based on the OCT image (see the embodiments shown in FIGS. 1 and 2 ).

[0092] In some embodiments, the ophthalmic device has the function of externally receiving data collected from the test eye by OCT scanning, the function of generating an OCT image from the received data, and the function of calculating the intraocular distance based on the OCT image (see the embodiment shown in Figure 3).

[0093] In some embodiments, the ophthalmic device has the function of externally receiving an OCT image generated from data collected from the test eye by an OCT scan, and the function of calculating the intraocular distance based on the OCT image (see the embodiment shown in Figure 3).

[0094] The ophthalmic device according to some embodiments has a function of performing additional processing based on the intraocular distance. The additional processing may be any type of data processing that can be performed based on the intraocular distance and / or at least data generated from the intraocular distance. Non-limiting examples of the additional processing include scaling of the OCT image, scaling of distribution data of measurement values ​​at the fundus, relative scaling between measurement data and reference data, etc.

[0095] The OCT method implemented in the embodiments may be any. Some embodiments use either spectral-domain OCT or swept-source OCT. Spectral-domain OCT is a technique in which light from a low-coherence light source is split into measurement light and reference light, return light of the measurement light from the test object is superimposed on the reference light to generate interference light, the spectral distribution of the generated interference light is detected with a spectrometer, and image generation processing such as Fourier transform is applied to the detected spectral distribution. Swept-source OCT is a technique in which light from a tunable light source is split into measurement light and reference light, return light of the measurement light from the test object is superimposed on the reference light to generate interference light, the generated interference light is detected with a balanced photodiode, and image generation processing such as Fourier transform is applied to detection data collected in response to wavelength sweeping and scanning of the measurement light. In brief, spectral-domain OCT is an OCT method that acquires the spectral distribution of interference light in a spatially resolved manner, and swept-source OCT is an OCT method that acquires the spectral distribution of interference light in a time-resolved manner. Some embodiments may use other OCT methods (e.g., time-domain OCT).

[0096] The ophthalmic apparatus according to the embodiment described below has a fundus camera function for generating digital fundus photographs. However, the ophthalmic apparatus according to another embodiment may have another fundus imaging modality. For example, the ophthalmic apparatus according to some embodiments may have the function as any one of an SLO, a slit lamp microscope, and a surgical microscope as a fundus imaging modality.

[0097] Unless otherwise specified, this disclosure may use the term "image data" to refer to a collection of pixel data and the term "image" to refer to visual information generated from this image data interchangeably.

[0098] 4 to 7 show the configuration of an ophthalmic apparatus according to a non-limiting embodiment. The ophthalmic apparatus 1 is a specific example of the above-described ophthalmic apparatus 300. Any feature related to the ophthalmic apparatus 300 can be applied at least partially to the ophthalmic apparatus 1.

[0099] The ophthalmologic apparatus 1 includes a fundus camera unit 2, an OCT unit 100, and an arithmetic and control unit 200. The fundus camera unit 2 includes elements of a fundus camera and an OCT scanner. The OCT unit 100 includes elements of an OCT scanner. The arithmetic and control unit 200 includes one or more processors that perform various processes (such as calculation, analysis, and control) and a storage device.

[0100] The fundus camera unit 2 will now be described. Fig. 4 shows a non-limiting configuration of the fundus camera unit 2. The fundus camera unit 2 is capable of photographing the fundus Ef and the anterior segment of the subject's eye E. The digital image generated by the fundus camera unit 2 is typically a front image. The fundus camera unit 2 acquires observation images by video recording using near-infrared fixed light as illumination light, and acquires photographed images by photography using visible flash light as illumination light.

[0101] The fundus camera unit 2 includes an illumination optical system 10 and an imaging optical system 30. The illumination optical system 10 irradiates illumination light onto the subject's eye E. The imaging optical system 30 images the subject's eye E being irradiated with the illumination light. The fundus camera unit 2 guides measurement light provided from the OCT unit 100 to the subject's eye E, and also guides return light of the measurement light projected onto the subject's eye E to the OCT unit 100.

[0102] The observation illumination light output from the observation light source 11 of the illumination optical system 10 is reflected by the concave mirror 12, passes through the condenser lens 13, and passes through the visible cut filter 14 to become near-infrared light.It is then focused near the imaging light source 15, reflected by the mirror 16, and passed through the relay lens system 17, relay lens 18, aperture 19, and relay lens system 20 to be guided to the aperture mirror 21.It is reflected by the mirror portion around the central hole of the aperture mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E. The return light of the observation illumination light projected onto the subject's eye E is refracted by the objective lens 22, passes through the dichroic mirror 46, passes through the central hole of the aperture mirror 21, passes through the dichroic mirror 55, passes through the photographing focusing lens 31, is reflected by the mirror 32, passes through the half mirror 33A, is reflected by the dichroic mirror 33, and is imaged on the light-receiving surface of the image sensor 35 by the imaging lens 34. The image sensor 35 detects the return light at regular time intervals. The focus of the photographing optical system 30 is adjusted according to the photographing region.

[0103] The imaging illumination light output from the imaging light source 15 is projected onto the fundus oculi Ef along the same path as the observation illumination light. The return light of the imaging illumination light from the subject's eye E is guided to the dichroic mirror 33 along the same path as the return light of the observation illumination light, passes through the dichroic mirror 33, is reflected by a mirror 36, and is imaged by an imaging lens 37 on the light-receiving surface of an image sensor 38.

[0104] The liquid crystal display (LCD) 39 displays a fixation target (fixation target image) used to guide and fixate the line of sight. The light beam output from the LCD 39 is reflected by the half mirror 33A, reflected by the mirror 32, passes through the photographing focusing lens 31 and the dichroic mirror 55, passes through the central hole of the aperture mirror 21, transmits through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the fundus Ef.

[0105] The alignment optical system 50 generates an alignment index used to align the ophthalmic apparatus 1 with the subject's eye E. Alignment light output from a light-emitting diode (LED) 51 passes through an aperture 52, an aperture 53, and a relay lens 54, is reflected by a dichroic mirror 55, passes through the central hole of the aperture mirror 21, transmits through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E. Return light of the alignment light from the subject's eye E is guided to the image sensor 35 via the same path as the return light of the observation illumination light. By referring to the alignment index image generated by the image sensor 35, a user can perform manual alignment and / or the ophthalmic apparatus 1 can perform automatic alignment.

[0106] The focusing optical system 60 generates a split index used for focus adjustment of the subject's eye E. The focusing optical system 60 moves along the optical path (illumination optical path) of the illumination optical system 10 in conjunction with movement of the photographing focusing lens 31 along the optical path (photography optical path) of the photographing optical system 30. The reflecting rod 67 is inserted into and removed from the illumination optical path. When performing focus adjustment, the reflective surface of the reflecting rod 67 is tilted and positioned in the illumination optical path. The focusing light output from the LED 61 passes through the relay lens 62, is split into two beams by the split index plate 63, passes through the two-hole diaphragm 64, is reflected by the mirror 65, is once imaged and reflected by the condenser lens 66 on the reflective surface of the reflecting rod 67, passes through the relay lens 20, is reflected by the aperture mirror 21, passes through the dichroic mirror 46, is refracted by the objective lens 22, and is projected onto the subject's eye E. The return light of the focusing light from the subject's eye E is guided to the image sensor 35 through the same path as the return light of the alignment light. By referring to the split target image generated by the image sensor 35, manual focusing by the user and / or autofocusing by the ophthalmic apparatus 1 is performed.

[0107] The diopter correction lenses 70 and 71 are selectively inserted into the photographing optical path between the aperture mirror 21 and the dichroic mirror 55. The diopter correction lens 70 is a plus lens for correcting farsightedness, and the diopter correction lens 71 is a minus lens for correcting nearsightedness.

[0108] The dichroic mirror 46 combines the fundus imaging optical path and the OCT optical path (sample arm). The dichroic mirror 46 reflects light in the wavelength band used for OCT and transmits light for fundus imaging. The sample arm is provided with, in order from the OCT unit 100 side, a collimator lens unit 40, a retroreflector 41, a dispersion compensation member 42, an OCT focusing lens 43, an optical scanner 44, and a relay lens 45. The retroreflector 41 is movable along the optical path of the measurement light LS incident thereon and is used to correct the optical path length according to the axial length and adjust the interference state. The retroreflector 41 is moved by a retroreflector (RR) driver 41A shown in FIG. 6. The dispersion compensation member 42 is used for dispersion compensation between the sample arm and the reference arm. The OCT focusing lens 43 is movable along the sample arm and is used to adjust the focus of the sample arm. The movement of the OCT focusing lens 43 is coordinated with the movement of the imaging focusing lens 31 and the movement of the focus optical system 60. The optical scanner 44 is positioned at a position substantially conjugate with the pupil of the subject's eye E by alignment, and changes the traveling direction of the measurement light LS. The optical scanner 44 includes, for example, a galvano scanner that deflects the measurement light LS in the x direction and a galvano scanner that deflects it in the y direction.

[0109] In the present disclosure, the direction of the optical axis of the fundus camera unit 2 (objective lens 22) is defined as the z-direction, one direction perpendicular to the z-direction is defined as the x-direction, and a direction perpendicular to both the z-direction and the x-direction is defined as the y-direction. In many ophthalmic examinations, alignment in the xy directions is performed to align the device optical axis (in this embodiment, the optical axis of the objective lens 22) with the ocular axis of a seated or standing subject, and alignment in the z direction is performed to align the distance between the device optical system (e.g., the objective lens 22) and the subject's eye with a predetermined value (working distance). In accordance with the conventions in the ophthalmic field, the present disclosure defines the direction of the axis of the subject's eye E as the z-direction, the horizontal direction as the x-direction, and the vertical direction (the subject's body axis direction) as the y-direction. When performing an examination on a subject in a different position, directions can be defined in accordance with these definitions.

[0110] The OCT unit 100 will now be described. FIG. 5 shows a non-limiting configuration of the OCT unit 100. The OCT unit 100 has a spectral-domain OCT optical system. This OCT optical system includes an interference optical system. This interference optical system splits light from a low-coherence light source (broadband light source) into measurement light LS and reference light LR, guides the reference light LR using a reference arm, projects the measurement light LS onto the subject's eye E using a sample arm, and generates interference light LC by superimposing the return light of the measurement light LS from the subject's eye E on the reference light LR that has passed through the reference arm. A spectroscope 130 generates an electrical signal (interference signal) that indicates the spectral distribution of the interference light LC.

[0111] The light source unit 101 outputs broadband low-coherence light L0, and includes an optical output device such as a superluminescent diode (SLD), an LED, or a semiconductor optical amplifier (SOA).

[0112] Low-coherence light L0 output from light source unit 101 is guided by optical fiber 102 to polarization controller 103, where its polarization state is adjusted, and then guided by optical fiber 104 to fiber coupler 105, where it is split into measurement light LS and reference light LR. The measurement light LS is guided by a sample arm, and the reference light LR is guided by a reference arm.

[0113] The reference light LR is guided by an optical fiber 110 to a collimator 111 where it is converted into a parallel beam, passes through an optical path length correction member 112 for compensating for the optical distance between the sample arm and the reference arm, passes through a dispersion compensation member 113 for compensating for dispersion between the sample arm and the reference arm, and is then guided to a retroreflector 114. The retroreflector 114 is movable in a direction along the optical path of the reference light LR incident thereon. The retroreflector 114 is moved by a retroreflector (RR) driver 114A shown in FIG. 6. The movement of the retroreflector 114 is used to correct the optical path length based on the axial length of the subject's eye E and to adjust the interference state. The reference light LR that has passed through the retroreflector 114 passes through the dispersion compensation member 113 and the optical path length correction member 112, is converted from a parallel beam into a focused beam by the collimator 116, is guided through the optical fiber 117 to the polarization controller 118 where its polarization state is adjusted, is guided through the optical fiber 119 to the attenuator 120 where its light amount is adjusted, and reaches the fiber coupler 122 via the optical fiber 121.

[0114] On the other hand, the measurement light LS is guided through an optical fiber 127 to a collimator lens unit 40, where it is converted into a parallel beam, passes through a retroreflector 41, a dispersion compensation member 42, an OCT focusing lens 43, an optical scanner 44, and a relay lens 45, is reflected by a dichroic mirror 46, is refracted by an objective lens 22, and is projected onto the subject's eye E. The measurement light LS is scattered and reflected at various depth positions in the subject's eye E. Return light of the measurement light LS from the subject's eye E is guided by a sample arm to a fiber coupler 105, and reaches a fiber coupler 122 via an optical fiber 128.

[0115] The fiber coupler 122 generates interference light LC by superimposing the measurement light LS incident from the optical fiber 128 and the reference light LR incident from the optical fiber 121. The interference light LC is guided to the spectroscope 130 via the optical fiber 129. The spectroscope 130 converts the incident interference light LC into a parallel beam using a collimator lens, resolves this parallel beam into multiple spectral components using a diffraction grating, and projects these spectral components onto an image sensor via a lens. This image sensor is, for example, a line sensor, and detects the multiple spectral components of the interference light LC to generate an electrical signal (interference signal, detection signal). The interference signal, which includes information on the spectral distribution of the interference light LC, is sent to the arithmetic and control unit 200.

[0116] The OCT unit 100 of some embodiments may include a swept-source OCT optical system. In this case, the light source unit 101 includes, for example, a tunable light source (e.g., a near-infrared tunable laser) that rapidly changes the wavelength of emitted light. Furthermore, the swept-source OCT optical system splits the interference light LC at a predetermined ratio (e.g., 1:1) to generate a pair of interference light beams, which are then detected by balanced photodiodes. The balanced photodiodes detect each of the pair of interference light beams and output the difference between the pair of detection signals obtained. This difference signal is sent to a data acquisition system (DAQ). The light source unit 101 provides the data acquisition system with a clock synchronized with the wavelength sweep. The data acquisition system samples the difference signal input from the balanced photodiode based on the clock from the light source unit 101. Data (interference signals) obtained by sampling the difference signals are provided to subsequent processing (e.g., image generation).

[0117] In the exemplary configurations shown in FIGS. 4 and 5 , optical path length changing elements (retroreflectors 41 and 114) are provided in both the sample arm and the reference arm. In some embodiments, an optical path length changing element may be provided in only one of the sample arm and the reference arm. The type of optical path length changing element is not limited to that of this embodiment. In some embodiments, the optical path length changing element in the reference arm may be a movable reflecting member (reference mirror) (see reference mirror 314 in FIG. 2 ). More generally, the optical path length changing element functions to relatively change the length of the sample arm and the length of the reference arm, i.e., to move the coherence gate of an interference optical system having the sample arm and the reference arm. Such an optical path length changing element functions as the optical path length changing section described above.

[0118] The moving mechanism 150 will be described. The moving mechanism 150 moves the optical system of the ophthalmologic apparatus 1. In some embodiments, the moving mechanism 150 moves at least the fundus camera unit 2 three-dimensionally. This three-dimensional movement is realized by, for example, a combination of movement in the x direction, movement in the y direction, and movement in the z direction.

[0119] The arithmetic and control unit 200 will now be described. The arithmetic and control unit 200 executes various processes such as control, calculation, analysis, etc. This disclosure will describe some non-limiting examples of processes that can be executed by the arithmetic and control unit 200.

[0120] The hardware elements of the arithmetic control unit 200 include, for example, a processor, random access memory (RAM), read-only memory (ROM), a hard disk drive (HDD), a solid-state drive (SSD), and a communication interface. Storage devices such as the HDD and SSD store various computer programs.

[0121] In some embodiments, the arithmetic and control unit 200 includes a user interface (also called a human-machine interface) such as an operation device, an input device, a display device, etc. In some embodiments, at least a part of the user interface is arranged as a peripheral device of the ophthalmologic apparatus 1.

[0122] 6 mainly illustrates a non-limiting configuration of the processing system of the ophthalmologic apparatus 1, and particularly illustrates a non-limiting configuration of the arithmetic and control unit 200. The arithmetic and control unit 200 includes a control unit 210, an image generation unit 220, and a data processing unit 230. The arithmetic and control unit 200 may include at least a part of a user interface 240.

[0123] The control unit 210 includes one or more processors, and is configured to control each unit of the ophthalmologic apparatus 1. The control unit 210 includes a main control unit 211 and a storage unit 212.

[0124] The main control unit 211 includes a processor and is configured to control elements of the ophthalmic apparatus 1 (for example, some elements shown in FIGS. 4 to 7). The main control unit 211 may also control external equipment (apparatus, device, system, etc.) connected to the ophthalmic apparatus 1. The functions of the main control unit 211 are realized by cooperation between hardware including circuits and control software.

[0125] The storage unit 212 includes a storage device such as an HDD, an SSD, etc. The storage unit 212 stores various types of information. For example, as shown in FIG. 7 , the storage unit 212 stores calibration information 213 and optical path length information 214.

[0126] The calibration information 213 is generated based on information used for calibrating the ophthalmologic apparatus 1 or information obtained by the calibration. The calibration information 213 includes one or more calibration parameter values.

[0127] The calibration information 213 may include reference optical path length information indicating a reference value of the optical path length of the arms (sample arm and / or reference arm) of the interference optical system of the ophthalmic apparatus 1. If the optical path length of the sample arm is changeable, the calibration information 213 includes reference optical path length information of the sample arm. The reference optical path length information of the sample arm may be, for example, information indicating the reference position of the retroreflector 41 or information indicating the reference state of the retroreflector driver 41A. If the optical path length of the reference arm is changeable, the calibration information 213 includes reference optical path length information of the reference arm. The reference optical path length information of the reference arm may be, for example, information indicating the reference position of the retroreflector 114 or information indicating the reference state of the retroreflector driver 114A.

[0128] The calibration information 213 may include step size information indicating a step size for changing the optical path length of an arm (sample arm and / or reference arm) of the interference optical system of the ophthalmic apparatus 1. If the optical path length of the sample arm is changeable, the calibration information 213 includes step size information of the sample arm. The step size information of the sample arm is, for example, information indicating a unit movement distance of the retroreflector 41 and corresponds to a unit operation amount (unit drive amount) of the retroreflector driver 41A. The unit movement distance is a physical distance in real space. If the optical path length of the reference arm is changeable, the calibration information 213 includes step size information of the reference arm. The step size information of the reference arm is, for example, information indicating a unit movement distance of the retroreflector 114 and corresponds to a unit operation amount (unit drive amount) of the retroreflector driver 114A. In this example, the change amount of the optical path length of the arm can be expressed as the number of unit movement distances (number of steps). The optical path length of the arm corresponding to the position of the retroreflector 41 (or 114) at any point in time can be expressed as the quotient (number of steps) obtained by dividing the distance between a predetermined origin and the retroreflector 41 (or 114) by the unit movement distance.

[0129] The calibration information 213 may include reference depth position information indicating a reference depth position in an OCT image generated by the ophthalmic apparatus 1. The reference optical path length information is used as a target depth position at which a retinal image is to be positioned in Auto-Z.

[0130] The calibration information 213 may include depth resolution information indicating the depth resolution of the OCT image generated by the ophthalmic apparatus 1. In this example, any depth position in the OCT image can be expressed as a pixel position. The depth resolution represents the actual dimension in the depth direction corresponding to one pixel.

[0131] The calibration information 213 may include reference intraocular distance information indicating the value of the intraocular distance (reference intraocular distance) in the model eye (calibration model eye) used for calibrating the ophthalmic apparatus 1. The reference intraocular distance information may be, for example, reference axial length information indicating the value of the axial length (reference axial length) in the calibration model eye.

[0132] The optical path length information 214 indicates the optical path lengths of the arms (sample arm and / or reference arm) of the interference optical system when an OCT scan is applied to the fundus Ef of the subject's eye E. If the optical path length of the sample arm is changeable, the optical path length information 214 includes the optical path length information of the sample arm. If the optical path length of the reference arm is changeable, the optical path length information 214 includes the optical path length information of the reference arm.

[0133] As shown in FIG. 7 , the storage unit 212 may store an OCT image 215. The OCT image 215 may be any OCT image generated based on data collected by applying an OCT scan to the fundus Ef of the subject's eye E. The storage unit 212 may store distribution data 216. The distribution data 216 is data representing the distribution of predetermined measurement values ​​in the fundus Ef of the subject's eye E, and may be, for example, fundus tissue thickness distribution data. The storage unit 212 may store measurement data 217 and reference data 218. The measurement data 217 may be one or more measurement values ​​of any type (i.e., one measurement value or a set of measurement values) obtained from an OCT image of the fundus Ef of the subject's eye E. The reference data 218 is data used as a standard for evaluating the measurement data. For example, the measurement data is fundus tissue thickness distribution data of the subject's eye E, and the reference data is a reference database (reference data set) of the fundus tissue thickness distribution.

[0134] The image generating unit 220 is configured to process data collected by applying an OCT scan to the fundus Ef of the subject's eye E to generate OCT image data. The image generating unit 220 includes one or more processors. The functions of the image generating unit 220 are realized by cooperation between hardware including circuits and image generating software. The processing performed by the image generating unit 220 is similar to image generation in conventional spectral domain OCT. The image generating unit 220 of some embodiments performs processing similar to image generation in conventional swept-source OCT.

[0135] The image generating unit 220 of this embodiment generates cross-sectional image data by processing the data (interference signal including information on the spectral distribution of the interference light LC) generated by the spectroscope 130. This image generation processing includes sampling (A / D conversion), denoising, filtering, fast Fourier transform (FFT), and the like, similar to conventional spectral domain OCT.

[0136] The OCT image data generated by the image generator 220 is a data set including a group of image data. This group of image data is a group of A-scan image data generated by imaging the reflection intensity profile of each of a plurality of A-lines arranged in the area where the OCT scan was applied. Such OCT image data is an example of an OCT intensity image.

[0137] The OCT image data may be stack data generated by embedding multiple B-scan image data in a single three-dimensional coordinate system. The image generator 220 can generate volume data (voxel data) by applying a voxelization process to the stack data. The stack data and volume data are examples of three-dimensional image data in which positions are expressed using a three-dimensional coordinate system (x-y-z coordinate system), and are also examples of three-dimensional OCT intensity images.

[0138] The image generating unit 220 can process the three-dimensional image data. For example, the image generating unit 220 can generate new image data by applying rendering to the three-dimensional image data. This rendering method may be any method, such as volume rendering, surface rendering, multiplanar reconstruction (MPR), maximum intensity projection (MIP), minimum intensity projection (MIP), or average intensity projection (AIP).

[0139] As a non-limiting example of rendering, the image generation unit 220 may generate projection image data by accumulating 3D image data in the z direction. As another example, the image generation unit 220 may generate shadowgram data by accumulating a portion of the 3D image data (3D partial image data) in the z direction. The 3D partial image data is extracted from the 3D image data using a known segmentation method. The projection image data and shadowgram data are 2D image data whose positions are expressed using a 2D coordinate system (xy coordinate system). The direction in which the 3D image data is accumulated is not limited to the z direction. Therefore, the image generation unit 220 can generate 2D image data of any orientation from the 3D image data.

[0140] In addition to the above-described OCT structural imaging, the ophthalmic apparatus 1 may be configured to perform OCT functional imaging. Non-limiting examples of OCT functional imaging include OCT angiography, OCT blood flow measurement, OCT elastography, and OCT polarimetry. OCT angiography is a technique for imaging a vascular network by measuring and visualizing changes in OCT signals according to blood flow. OCT blood flow measurement is a technique for measuring and visualizing the dynamics of blood flow within blood vessels. OCT elastography is a technique for measuring and visualizing the distribution of strain and stiffness in biological tissue. OCT polarimetry is a technique for measuring and visualizing the structural birefringence of fibrous tissue in a living organism.

[0141] The data processing unit 230 performs various types of data processing. For example, the data processing unit 230 processes images (fundus images, anterior segment images, etc.) acquired by the fundus camera unit 2, and processes images (OCT images) acquired using OCT scanning. The data processing unit 230 includes one or more processors. The data processing unit 230 is realized by cooperation between hardware including circuits and data processing software. Some non-limiting examples of the configuration and operation of the data processing unit 230 are described below.

[0142] The data processing unit 230 includes an intraocular processing calculation unit 231. The intraocular distance calculation unit 231 receives an OCT image of the fundus Ef of the subject's eye E and optical path length information when the data used to generate the OCT image was collected from the fundus Ef by OCT scanning. The OCT image is provided to the intraocular distance calculation unit 231, for example, directly from the image generation unit 220, or is provided to the intraocular distance calculation unit 231 from the image generation unit 220 via the main control unit 211. The optical path length information is, for example, stored in the memory unit 212 by the main control unit 211 during OCT scanning (optical path length information 214), and is read from the memory unit 212 by the main control unit 211 and provided to the intraocular distance calculation unit 231. The intraocular distance calculation unit 231 is configured to calculate the intraocular distance of the subject's eye E based on the calibration information 213, the OCT image, and the optical path length information 214. The calculated intraocular distance may be the axial length of the eye.

[0143] As described above, examples of information included in the calibration information 213 include reference optical path length information, step size information, reference depth position information, depth resolution information, and reference intraocular distance information.

[0144] When the calibration information 213 includes reference optical path length information, the intraocular distance calculation unit 231 can execute a process of obtaining first difference information indicating the difference between the optical path length information and the reference optical path length information, and a process of calculating the intraocular distance using the obtained first difference information. The process of calculating the intraocular distance using the first difference information may be executed based on at least the first difference information and an OCT image. For example, the process may be executed based on the calibration information 213 (information separate from the reference optical path length information), the first difference information, and the OCT image.

[0145] When the calibration information 213 includes reference optical path length information and step size information, the intraocular distance calculation unit 231 can calculate, as first difference information, a differential step number, which is the difference between the number of steps indicated by the optical path length information and the number of steps indicated by the reference optical path length information. Furthermore, the intraocular distance calculation unit 231 can perform a process of converting the differential step number into a physical distance (first distance) using the step size information, and a process of calculating the intraocular distance using the first distance. The process of converting the differential step number into the first distance using the step size information may be performed based on at least the first distance and an OCT image. For example, this process may be performed based on the calibration information 213 (information separate from the reference optical path length information and the step size information), the first distance, and an OCT image.

[0146] When the calibration information 213 includes reference depth position information, the intraocular distance calculation unit 231 can execute the following processes: analyzing an OCT image of the subject's eye E to obtain depth position information indicating the depth position of a predetermined portion of the fundus oculi Ef; obtaining second difference information indicating the difference between the obtained depth position information and the reference depth position information; and calculating the intraocular distance using the obtained second difference information. The process of calculating the intraocular distance using the second difference information may be executed based on at least the second difference information and optical path length information. For example, this process may be executed based on the calibration information 213 (information different from the reference depth position information), the second difference information, and the optical path length information.

[0147] When the calibration information 213 includes reference depth position information and depth resolution information, the intraocular distance calculation unit 231 can calculate, as second difference information, a difference pixel position, which is the difference between a pixel position indicated by the depth position information and a pixel position indicated by the reference depth position information. Furthermore, the intraocular distance calculation unit 231 can perform a process of converting the difference pixel position into a physical distance (second distance) using the depth resolution information, and a process of calculating the intraocular distance using the second distance. The process of calculating the intraocular distance using the second distance may be performed based at least on the second distance and optical path length information. For example, this process may be performed based on the calibration information 213 (information separate from the reference depth position information and depth resolution information), the second difference information, and the optical path length information.

[0148] The ophthalmologic apparatus 1 may be configured to be able to perform auto-Z and Z-lock. In this case, the main controller 211 is configured to perform a combination of scan control, which controls the fundus camera unit 2 (particularly the optical scanner 44) and the OCT unit 100 to apply repeated scans to the fundus Ef of the subject's eye E to repeatedly collect data, and optical path length control, which controls the optical path length change unit (one or both of the retroreflector drivers 41A and 114) to depict a predetermined portion of the fundus Ef at a reference depth position based on the data collected by this repeated scan. Furthermore, the main controller 211 is configured to control the fundus camera unit 2 and the OCT unit 100 to apply an OCT scan to the fundus Ef to collect data to be provided for generating an OCT image used in the intraocular distance calculation process, during or after the execution of this combination control.

[0149] The intraocular distance calculation part 231 may be configured to perform the process of calculating depth position information of a predetermined part of the fundus Ef from an OCT image of the subject's eye E in the following manner. The intraocular distance calculation part 231 in this example performs a process of analyzing the OCT image of the subject's eye E to identify an image of a predetermined part of the fundus Ef, and a process of calculating an average depth position of the image of the identified predetermined part. Information indicating the calculated average depth position is used as the depth position information in this example.

[0150] When the calibration information 213 includes reference optical path length information, step size information, reference depth position information, depth resolution information, and reference axial length information (information indicating the axial length of the calibration model eye), the intraocular distance calculation unit 231 performs the following processes: calculating a differential step number, which is the difference between the number of steps indicated by the optical path length information and the number of steps indicated by the reference optical path length information; and calculating a first distance by multiplying the calculated differential step number by the step size information. The intraocular distance calculation unit 231 also performs the following processes: analyzing an OCT image of the subject's eye E to obtain depth position information indicating a pixel position corresponding to the depth position of a predetermined portion of the fundus Ef; calculating a differential pixel position, which is the difference between the pixel position indicated by the obtained depth position information and the pixel position indicated by the reference depth position information; and multiplying the calculated differential pixel position by the depth resolution information to calculate a second distance. Furthermore, the intraocular distance calculation unit 231 calculates the axial length of the subject's eye E by adding the first distance, the second distance, and the reference axial length.

[0151] The data processing unit 230 may include any of an OCT image scaling unit 232 , a distribution data scaling unit 233 , a relative scaling unit 234 , a measurement data evaluation unit 235 , and a myopia evaluation unit 236 .

[0152] When the data processing unit 230 includes the OCT image scaling unit 232, the storage unit 212 stores a previously acquired OCT image 215 of the subject's eye E. The main controller 211 reads the OCT image 215 from the storage unit 212 and provides it to the OCT image scaling unit 232. The main controller 211 also provides the intraocular distance of the subject's eye E calculated by the intraocular distance calculation unit 231 to the OCT image scaling unit 232. The OCT image scaling unit 232 scales the OCT image 215 based on the intraocular distance of the subject's eye E. In a non-limiting example, the OCT image scaling unit 232 can scale an OCT intensity image of the subject's eye E and / or scale an OCT functional image of the subject's eye E.

[0153] When the data processing unit 230 includes the distribution data scaling unit 233, the storage unit 212 stores previously acquired distribution data 216 of the subject's eye E. The main control unit 211 reads the distribution data 216 from the storage unit 212 and provides the distribution data 216 to the distribution data scaling unit 233. The main control unit 211 also provides the intraocular distance of the subject's eye E calculated by the intraocular distance calculation unit 231 to the distribution data scaling unit 233. The distribution data scaling unit 233 scales the distribution data 216 based on the intraocular distance of the subject's eye E. In a non-limiting example, the distribution data scaling unit 233 can scale the fundus tissue thickness distribution data of the subject's eye E.

[0154] When the data processing unit 230 includes a relative scaling unit 234 and a measurement data evaluation unit 235, the storage unit 212 stores previously acquired measurement data 217 of the subject's eye E and previously created reference data 218. The main control unit 211 reads the measurement data 217 and the reference data 218 from the storage unit 212 and provides them to the relative scaling unit 234. The main control unit 211 also provides the intraocular distance of the subject's eye E calculated by the intraocular distance calculation unit 231 to the relative scaling unit 234. The relative scaling unit 234 performs relative scaling between the measurement data 217 and the reference data 218 based on the intraocular distance of the subject's eye E, thereby matching the scale of the measurement data 217 with the scale of the reference data 218. The measurement data evaluation unit 235 evaluates the measurement data 217 by comparing the measurement data 217 and the reference data 218, whose scales have been matched by relative scaling. In a non-limiting example, the relative scaling unit 234 can perform relative scaling between the fundus tissue thickness distribution data of the subject's eye E and a reference database (reference data set) of fundus tissue thicknesses so that the scale of the fundus tissue thickness distribution data matches the scale of the reference database. The measurement data evaluation unit 235 compares the fundus tissue thickness distribution data and the reference database, the scales of which are matched, to determine a percentile value, and evaluates the percentile value in three levels: green (5% or more), yellow (1% or more and less than 5%), and red (less than 1%).

[0155] When the data processing unit 230 includes the myopia evaluation unit 236, the main control unit 211 provides the intraocular distance of the subject's eye E calculated by the intraocular distance calculation unit 231 to the myopia evaluation unit 236. The myopia evaluation unit 236 evaluates myopia based on the intraocular distance of the subject's eye E. In a non-limiting example, the intraocular distance calculation unit 231 calculates the axial length of the subject's eye E, and the myopia evaluation unit 236 evaluates axial myopia based on the axial length of the subject's eye E. This evaluation may be performed by comparing the axial length of the subject's eye E with a pre-created reference database of axial myopia. For example, the myopia evaluation unit 236 can calculate a percentile value of the axial length of the subject's eye E relative to the reference database and derive an evaluation result based on this percentile value. Alternatively, the myopia evaluation unit 236 can derive an evaluation result by comparing the axial length of the subject's eye E with one or more thresholds determined based on the reference database.

[0156] The user interface 240 includes a display unit 241 and an operation unit 242. The display device 3 in Fig. 4 is an example of the display unit 241. The operation unit 242 includes an operation device and an input device. Examples of devices in the operation unit 242 include a switch, a lever, a mouse, a trackball, a keyboard, and an operation panel.

[0157] As described above, the ophthalmic apparatus 1 having the elements (hardware elements, software elements) shown in Figures 4 to 7 provides a non-limiting example of the ophthalmic apparatus 300 in Figure 2. It will be understood by those skilled in the art that the ophthalmic apparatus 1 also provides a non-limiting example of the ophthalmic apparatus 400 in Figure 3.

[0158] According to some embodiments, a novel intraocular distance estimation technique can be provided that uses calibration information of an ophthalmic device (OCT device). Furthermore, the quality of the estimation process is improved by taking into account both the calibration information indicating the conditions for the calibration of the OCT device and the conditions for OCT imaging of the subject's eye. The present disclosure provides various embodiments that achieve at least these advantageous effects.

[0159] In some embodiments, calibration of the OCT device involves adjusting the optical path length of an arm of the interference optical system so that a simulated retinal image in an OCT image obtained by applying an OCT scan to a calibration model eye having a reference axial length is positioned at a reference depth position. Reference optical path length information determined by this calibration is included in the calibration information, along with reference axial length information and reference depth position information. Furthermore, step size information and depth resolution information are included in the calibration information as conditions indicating the characteristics of the OCT device. In some embodiments, the OCT device focuses on the difference in the optical path length of the interference optical system during OCT scanning and the difference in the depth position of the fundus image depicted in the OCT image as differences between the OCT imaging conditions for the calibration model eye and the OCT imaging conditions for the test eye, and estimates the axial length of the test eye by correcting the reference axial length of the calibration model eye using both of these differences. This provides a novel and high-quality axial length estimation technique.

[0160] Although several embodiments according to the present disclosure have been described above with reference to the drawings, these are non-limiting examples, and various configurations other than those described above may also be adopted.

[0161] In addition, in the multiple processing procedures and usage modes used in the above description, multiple steps (processes) are described in order. However, the order of steps performed in each processing procedure and each usage mode is not limited to the order described. In each processing procedure and each usage mode, the order of steps described in this disclosure can be changed to the extent that the content is not affected. Furthermore, the multiple embodiments described in this disclosure can be at least partially combined to the extent that the content is not contradictory.

[0162] It will be understood by those skilled in the art that the present disclosure also provides embodiments in categories other than ophthalmic devices (ophthalmic imaging devices, ophthalmic information processing devices). For example, the present disclosure provides an embodiment of a method for controlling an ophthalmic device, an embodiment of a program for causing a computer to execute each step of the method, and an embodiment of a computer-readable non-transitory recording medium on which the program is recorded. The recording medium may take any form. For example, the recording medium may include any one or more of a magnetic disk, an optical disk, a magneto-optical disk, and a semiconductor memory.

[0163] The present disclosure is merely an example of how to implement the present invention, and those who intend to implement the present invention can make any modifications (omissions, substitutions, additions, etc.) within the scope of the gist of the present invention.

[0164] 1 Ophthalmic device 300 Ophthalmic device 310 OCT scanner 320 Processor 330 Storage device

Claims

1. An ophthalmic device comprising an optical coherence tomography (OCT) scanner that applies an OCT scan to the fundus of a subject's eye to collect data, and one or more processors connected to a storage device, wherein the OCT scanner includes: an interference optical system having a sample arm and a reference arm; and an optical path length changer that changes the optical path length of at least one of the sample arm and the reference arm; the storage device pre-stores calibration information including one or more calibration parameter values; the one or more processors generate an OCT image of the subject's eye based on the data collected by the OCT scanner, receive optical path length information indicating the optical path length at the time the data was collected, and calculate the intraocular distance of the subject's eye based on the calibration information, the OCT image, and the optical path length information.

2. The ophthalmic device of claim 1, wherein the calibration information includes reference optical path length information indicating a reference value of the optical path length, and the one or more processors determine first difference information indicating a difference between the optical path length information and the reference optical path length information, and calculate the intraocular distance using the first difference information.

3. The ophthalmic device of claim 2, wherein each of the optical path length information and the reference optical path length information is expressed as the number of steps in the change of the optical path length by the optical path length changing unit, the calibration information further includes step size information indicating the step size in the change of the optical path length by the optical path length changing unit, and the one or more processors calculate, as the first difference information, a differential step number that is the difference between the number of steps indicated by the optical path length information and the number of steps indicated by the reference optical path length information, convert the differential step number into a first distance using the step size information, and calculate the intraocular distance using the first distance.

4. An ophthalmic device according to any one of claims 1 to 3, wherein the calibration information includes reference depth position information indicating a reference depth position in an OCT image, and the one or more processors: analyze the OCT image of the subject's eye to obtain depth position information indicating the depth position of a predetermined part of the fundus; obtain second difference information indicating the difference between the depth position information and the reference depth position information; and calculate the intraocular distance using the second difference information.

5. An ophthalmic device according to claim 4, wherein each of the depth position information and the reference depth position information is expressed as a pixel position in an OCT image, the calibration information further includes depth resolution information indicating the depth resolution of the OCT image, and the one or more processors calculate, as the second difference information, a differential pixel position which is the difference between the pixel position indicated by the depth position information and the pixel position indicated by the reference depth position information, convert the differential pixel position to a second distance using the depth resolution information, and calculate the intraocular distance using the second distance.

6. An ophthalmic device according to claim 4 or 5, wherein the one or more processors perform combined control of scan control that controls the OCT scanner to apply repeated scans to the fundus to repeatedly collect data, and optical path length control that controls the optical path length changing unit so that the specified portion of the fundus is depicted at the reference depth position based on the data collected by the repeated scans, and the OCT scanner applies the OCT scan to the fundus to collect the data to be provided for generating the OCT image during or after execution of the combined control.

7. An ophthalmic device according to any one of claims 4 to 6, wherein the one or more processors analyze the OCT image of the subject's eye to identify an image of the specified area, calculate an average depth position of the image of the specified area, and the depth position information indicates the average depth position.

8. An ophthalmologic device according to any one of claims 1 to 7, wherein the calibration information includes reference intraocular distance information indicating a reference intraocular distance in a calibration model eye.

9. The calibration information includes reference optical path length information indicating a reference value of the optical path length, reference depth position information indicating a reference depth position in an OCT image, and reference axial length information indicating a reference axial length in a calibration model eye, each of the optical path length information and the reference optical path length information being expressed as a step number in changing the optical path length by the optical path length changing unit, and the reference depth position information being expressed as a pixel position in the OCT image, and the calibration information further includes step size information indicating a step size in changing the optical path length by the optical path length changing unit, and depth resolution information indicating a depth resolution of the OCT image, and the one or more processors calculate a differential step number which is the difference between the step number indicated by the optical path length information and the step number indicated by the reference optical path length information, multiply the differential step number by the step size information to calculate a first distance, analyze the OCT image of the test eye to determine depth position information indicating a pixel position corresponding to the depth position of a predetermined portion of the fundus, 2. The ophthalmic device of claim 1, further comprising: a differential pixel position that is the difference between the pixel position indicated by the depth position information and the pixel position indicated by the reference depth position information; a second distance that is calculated by multiplying the differential pixel position by the depth resolution information; and an axial length of the subject's eye that is calculated by adding the first distance, the second distance, and the reference axial length.

10. The ophthalmic device according to any one of claims 1 to 8, wherein the one or more processors calculate at least the axial length as the intraocular distance.

11. The ophthalmic device according to any one of claims 1 to 10, wherein the storage device further stores an OCT image of the subject's eye, and the one or more processors perform scaling of the OCT image based on the intraocular distance of the subject's eye.

12. An ophthalmic device according to any one of claims 1 to 10, wherein the storage device further stores distribution data of predetermined measurement values ​​at the fundus of the subject's eye, and the one or more processors scale the distribution data based on the intraocular distance of the subject's eye.

13. An ophthalmic device according to any one of claims 1 to 10, wherein the storage device further stores measurement data obtained from an OCT image of the fundus of the subject's eye and reference data created in advance, and the one or more processors perform relative scaling between the measurement data and the reference data based on the intraocular distance of the subject's eye, and evaluate the measurement data by comparing the measurement data to which the relative scaling has been applied with the reference data.

14. The ophthalmic device according to any one of claims 1 to 13, wherein the one or more processors perform an evaluation of myopia based on the intraocular distance of the subject's eye.

15. An ophthalmic device comprising one or more processors connected to a storage device, which processes data collected by an optical coherence tomography (OCT) scanner including an interference optical system having a sample arm and a reference arm, at least one of which is capable of changing the optical path length, by applying an OCT scan to the fundus of a subject's eye, wherein the storage device pre-stores calibration information including one or more calibration parameter values ​​acquired in calibration of the OCT scanner, and the one or more processors: generate an OCT image of the subject's eye based on the data collected by the OCT scanner; receive optical path length information indicating the optical path length when the data was collected; and calculate the intraocular distance of the subject's eye based on the calibration information, the OCT image, and the optical path length information.

16. An ophthalmic device comprising one or more processors connected to a storage device, which processes an OCT image generated by an optical coherence tomography (OCT) scanner including an interference optical system having a sample arm and a reference arm, at least one of which is capable of changing the optical path length, by applying an OCT scan to the fundus of a test eye, wherein the storage device pre-stores calibration information including one or more calibration parameter values ​​acquired in calibration of the OCT scanner, and the one or more processors receive the OCT image and optical path length information indicating the optical path length when the OCT scan was applied to the fundus of the test eye, and calculate the intraocular distance of the test eye based on the calibration information, the OCT image, and the optical path length information.

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