System and method for improving scleral process visibility in anterior OCT images

Abstract

The invention relates to a system and method for improving scleral process visibility in anterior OCT images. The system is arranged to process an anterior optical coherence tomography, AS-OCT, image comprising a representation of a portion of scleral process of the eye to obtain geometric measurements of the eye, the system comprising data processing hardware, the data processing hardware is arranged to: process the AS-OCT image to obtain a respective position in the AS-OCT image of a representation of a portion of scleral process of the eye in the AS-OCT image; and obtaining a geometric measurement result based on the obtained position. The system further includes an OCT imaging system operable to acquire an AS-OCT image and including a fixation target for fixing a gaze direction of the eye during acquisition of the AS-OCT image such that an axis in the AS-OCT image corresponding to a pupil axis of the eye is aligned with a direction in the AS-OCT image corresponding to an axial imaging direction of the OCT imaging system.

Description

field

[0002] Example aspects herein relate generally to the field of optical coherence tomography (OCT) imaging systems, and in particular, to OCT imaging systems for acquiring OCT images of at least a portion of an anterior chamber of an eye. background

[0004] Optical coherence tomography (OCT) is an imaging technique based on low-coherence interferometry that is widely used to acquire high-resolution two-dimensional and three-dimensional images of optically scattering media such as biological tissues.

[0005] As is well known, OCT imaging systems can be classified as time domain OCT (TD-OCT) or Fourier domain OCT (FD-OCT) (also known as frequency domain OCT) according to how depth ranging is achieved. In TD-OCT, the optical path length of the reference arm of the interferometer of the imaging system varies with time during the acquisition of the reflectivity profile of the scattering medium (referred to herein as the "imaging target") imaged by the OCT imaging system, and the reflectivity profile is generally referred to as a "depth scan" or "axial scan" ("A scan"). In FD-OCT, the spectral interference pattern generated by the interference between the light in the reference arm of the interferometer and the light in the sample arm at each A scan position is Fourier transformed to simultaneously acquire all points along the depth of the A scan without any change in the optical path length of the reference arm. FD-OCT can allow much faster imaging than the scanning of the sample arm mirror in the interferometer because all back reflections from the sample are measured simultaneously. Two common types of FD-OCT are spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). In SD-OCT, a broadband light source delivers many wavelengths to the imaging target, and a spectrometer is used as a detector to measure all wavelengths simultaneously. In SS-OCT (also known as time-coded frequency-domain OCT), the light source is swept over a range of wavelengths, and the temporal output of the detector is converted into spectral interferometry.

[0006] OCT imaging systems may also be classified as point scanning (also referred to as "point detection" or "scanning point"), line scanning, or full-field, depending on how the imaging system is configured to acquire OCT data at locations on an imaging target. Point scanning OCT imaging systems acquire OCT data by scanning across the surface of an imaging target with a focused sample beam, typically along a single line (which may be straight, or alternatively curved to define a circle or spiral) or a set of (usually substantially parallel) lines on the imaging target surface, and acquiring an axial depth profile (A-scan) for each of a plurality of points along the line, one point at a time, to create OCT data comprising a one-dimensional or two-dimensional array of A-scans representing a two-dimensional (i.e., B-scan) or three-dimensional (i.e., C-scan or volume scan) reflectance profile of the sample.

[0007] Line scanning OCT imaging systems acquire OCT data by scanning with focused light across the surface of an imaging target. The measured reflectance from the imaging target is used to generate OCT data including a two-dimensional reflectance distribution (i.e., a B-scan) of the sample. By scanning with focused light across multiple locations on the imaging target, OCT data including a three-dimensional reflectance distribution (i.e., a C-scan or volume scan) of the sample can be obtained. Typically, the focused light is straight and is scanned in a direction perpendicular to it, although in some cases it can be curved and the scanning direction adjusted accordingly. Full-field OCT imaging systems acquire OCT data by projecting a light beam onto an imaging target to acquire an "en-face" B-scan (orthogonal to the aforementioned B-scan), which can be stacked to produce a three-dimensional reflectance distribution (i.e., a C-scan or volume scan) of the sample.

[0008] Anterior segment OCT (AS-OCT) imaging can be performed using one of the various types of OCT imaging systems summarized above to obtain a tomographic image (typically a B-scan or C-scan) of at least a portion of the anterior segment of the eye. AS-OCT imaging is performed for various reasons related to eye health, such as for glaucoma assessment and cataract surgery (e.g., for biometry and corneal thickness measurement). A key aspect of glaucoma assessment is to determine the drainage capacity of the cornea / sclera / iris junction, which requires good visibility to this area. Although scans limited to this area can be performed (usually using a specialized lens adapter), for efficiency of data capture and storage, it is preferred to capture a full anterior chamber OCT image (also widely referred to as a "full chamber" or "full anterior segment" OCT image), which covers the entire anterior chamber of the eye and the surrounding portions of the anterior segment of the eye, typically including the cornea, sclera, iris, the anterior portion of the lens, and the scleral spur.

[0009] AS-OCT imaging can be used not only for glaucoma assessment, but also for various other purposes in which geometric measurements of the eye are made. Such geometric measurements can include measurements of distances within the eye, such as the anterior chamber width (ACW, also known as spur-to-spur or corner-to-corner distance), lens vault (LV), angle opening distance (AOD, e.g., AOD500), or anterior chamber depth (ACD) of the eye, or measurements of angles within the eye, such as, for example, the anterior chamber angle (ACA), trabecular-iris angle (TIA), or iris-lens angle of the eye, and / or related areas, such as, for example, the trabecular-iris space area (TISA; e.g., TISA500). Geometric measurements typically rely on accurate identification of the location of one or more portions of the spur of the eye (the spur is in the angular region where the iris meets the sclera in the anterior segment) within the AS-OCT image, which identified location can serve as a useful landmark or reference point. The better the visibility of the scleral prominence landmark, the more accurate the measurements based on the landmark. However, in an AS-OCT image, for example, in the form of an AS-OCT B-scan, the visibility or contrast of portions of the scleral prominence that are opposite to each other in the AS-OCT B-scan (i.e., representations of the scleral prominence that appear on opposite sides of the anterior segment imaged in the B-scan) often differ. As a result, it is often difficult to accurately locate at least one of the portions of the scleral prominence, and therefore difficult to obtain accurate geometric measurements from the image. Therefore, it is highly desirable to be able to more accurately locate the scleral prominence in an AS-OCT image (e.g., a whole-chamber OCT image).

[0010] Overview

[0011] According to a first exemplary aspect of the present invention, a system is provided, which is arranged to process an anterior segment optical coherence tomography (AS-OCT) image including a representation of a portion of a scleral protrusion of an eye to obtain geometric measurements of the eye. The system includes data processing hardware, which is arranged to: process the AS-OCT image to obtain a corresponding position in the AS-OCT image of a representation of the portion of the scleral protrusion of the eye; and obtain geometric measurements based on the acquired position. The system also includes an OCT imaging system operable to acquire the AS-OCT image, the OCT imaging system including a fixation target, which is arranged to fix the gaze direction of the eye during the acquisition of the AS-OCT image, so that the axis corresponding to the pupil axis of the eye in the AS-OCT image is aligned with the direction in the AS-OCT image corresponding to the axial imaging direction of the OCT imaging system. The fixation target may be arranged to fix the gaze direction of the eye during acquisition of the AS-OCT image, such that the pupil axis of the eye (rather than the visual axis of the eye) is aligned with the axial imaging direction of the OCT imaging system, wherein the axis corresponding to the pupil axis of the eye in the AS-OCT image (rather than the axis corresponding to the visual axis of the eye in the AS-OCT image) is correspondingly aligned with the direction corresponding to the axial imaging direction of the OCT imaging system in the AS-OCT image. Thus, the fixation target may be arranged to fix the gaze direction of the eye during acquisition of the AS-OCT image, such that the pupil axis of the eye is more closely aligned with the axial imaging direction of the OCT imaging system than the visual axis of the eye.

[0012] According to a second exemplary aspect of the present invention, there is provided a use of a fixation target of an OCT imaging system for equalizing image contrast of a representation of a portion of a scleral protrusion of an eye in an anterior segment OCT (AS-OCT) image acquired by the OCT imaging system, wherein the fixation target is used to equalize image contrast by fixing the gaze direction of the eye during acquisition of the AS-OCT image so that an axis corresponding to the pupil axis of the eye in the AS-OCT image is aligned with a direction corresponding to the axial imaging direction of the OCT imaging system in the AS-OCT image. The fixation target may be used to equalize image contrast by fixing the gaze direction of the eye during acquisition of the AS-OCT image so that the pupil axis of the eye (rather than the visual axis of the eye) is aligned with the axial imaging direction of the OCT imaging system, wherein the axis corresponding to the pupil axis of the eye in the AS-OCT image (rather than the axis corresponding to the visual axis of the eye in the AS-OCT image) is correspondingly aligned with a direction corresponding to the axial imaging direction of the OCT imaging system in the AS-OCT image. Thus, the fixation target can fix the gaze direction of the eye during acquisition of AS-OCT images so that the pupil axis of the eye is more closely aligned with the axial imaging direction of the OCT imaging system than the visual axis of the eye.

[0013] According to a third exemplary aspect of the present invention, there is provided a method for processing an anterior segment optical coherence tomography (AS-OCT) image acquired by an OCT imaging system to obtain geometric measurements based on one or more anatomical features in the AS-OCT image, the AS-OCT image including a representation of a portion of a scleral protrusion of an eye. The method includes: acquiring the AS-OCT image while fixing the gaze direction of the eye by having the eye gaze at a fixation target so that an axis corresponding to the pupil axis of the eye in the AS-OCT image is aligned with a direction corresponding to the axial imaging direction of the OCT imaging system in the AS-OCT image; processing the acquired AS-OCT image to acquire a corresponding position of the representation of the portion of the scleral protrusion of the eye in the AS-OCT image in the AS-OCT image; and obtaining geometric measurements based on the position in the acquired AS-OCT image. The AS-OCT image can be acquired while the gaze direction of the eye is fixed by having the eye gaze on a fixation target, so that the pupil axis of the eye (rather than the visual axis of the eye) is aligned with the axial imaging direction of the OCT imaging system, wherein the axis corresponding to the pupil axis of the eye in the AS-OCT image (rather than the axis corresponding to the visual axis of the eye in the AS-OCT image) is correspondingly aligned with the direction corresponding to the axial imaging direction of the OCT imaging system in the AS-OCT image. Therefore, the AS-OCT image can be acquired while the gaze direction of the eye is fixed by having the eye gaze on a fixation target, so that the pupil axis of the eye is more closely aligned with the axial imaging direction of the OCT imaging system than the visual axis of the eye. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Example embodiments will now be described in detail, by way of non-limiting example only, with reference to the accompanying drawings described below.Unless otherwise indicated, like reference numerals appearing in different figures of the drawings may represent the same element or a functionally similar element.

[0016] Figure 1 is a schematic diagram of a system 100 according to a first exemplary embodiment of the present invention.

[0017] Figure 2 is a schematic diagram of a B-scan 200 acquired by the OCT imaging system 110 of the system 100 according to the first example embodiment herein.

[0018] Figure 3 is a schematic diagram of a front view of a display device 300 of the system 100, which displays a graphic 310 as an example of a fixation target for fixing the gaze direction of the eyes.

[0019] Figure 4is a schematic diagram of programmable signal processing hardware that may be configured to perform the functions of the data processing hardware 150 and / or the controller 115 of the OCT imaging system 110 described herein.

[0020] Figure 5 is a flow chart illustrating a process by which the data processing hardware 150 of the system 100 processes the AS-OCT images 130 acquired by the OCT imaging system 110 to obtain geometric measurements of the eye, according to a first example embodiment herein.

[0021] Figure 6 is a flow chart illustrating a process in the first example embodiment herein by which the controller 115 of the OCT imaging system 110 controls the fixation target 120 to fix the gaze direction of the eye 140 during acquisition of the AS-OCT image 130 .

[0022] Figure 7 is a flow chart illustrating an alternative process in a first alternative implementation of the first example embodiment herein by which the controller 115 of the OCT imaging system 110 may obtain an indication of the orientation of the pupil axis 153 of the eye relative to the visual axis of the eye.

[0023] Figure 8 is a schematic diagram of an example calibration B-scan 800 acquired by the OCT imaging system 110 in a first alternative implementation of the first example embodiment herein.

[0024] Fig. 9 is a flowchart of a process in a first alternative implementation of the first example embodiment of the present invention, by which the controller 115 of the OCT imaging system 110 can determine the orientation of the axis corresponding to the pupil axis of the eye in the calibration B-scan relative to the direction corresponding to the axial imaging direction of the OCT imaging system 110 in the calibration B-scan.

[0025] Fig.10 is a flow chart illustrating a second alternative process in a second alternative implementation of the first example embodiment herein by which the controller 115 of the OCT imaging system 110 may obtain an indication of the orientation of the pupil axis of the eye relative to the visual axis of the eye.

[0026] Fig.11A and Fig. 11B Schematic diagrams of an example first calibration B-scan 1100 and an example calibration second B-scan 1150 , respectively, according to a second alternative implementation of the first example embodiment herein.

[0027] Fig. 12A and Fig. 12BThey are respectively an uncorrected B-scan 1200 and a corrected B-scan 1250 according to the first example embodiment herein.

[0028] Detailed Description of Example Embodiments

[0029] The inventors have recognized that, because the visual axis and pupillary axis of the eye are not aligned, conventional OCT imaging systems used for AS-OCT imaging (e.g., for whole chamber imaging) tend to acquire AS-OCT B-scans in which anatomical features (such as the iris) are presented at a small tilt relative to the lateral direction in the B-scan, i.e., perpendicular to the axial direction in the B-scan (the axial direction is the direction in the B-scan along which the elements of each component A-scan of the B-scan are arranged). This tilt is generally viewed as objectionable and is typically compensated for in post-processing to provide a symmetrical B-scan to the clinician.

[0030] In careful examination of the AS-OCT B-scans, the inventors have found that the degree of tilt observed in the acquired B-scan is consistent with the representation of the opposite portion of the scleral process in the B-scan (i.e., different cross-sectional views of the scleral process appearing on opposite sides of the B-scan, e.g., Fig. 12A More specifically, the inventors have noticed that the difference between the respective visibilities (or contrasts) of the representations of two opposing portions of the scleral protuberance in the B-scan tends to increase as the degree of inclination of the anatomical features of the anterior segment relative to the frame of the B-scan increases.

[0031] The inventors have further recognized that the overall visibility or contrast of the representation of portions of the scleral prominence in an AS-OCT B-scan, and therefore the accuracy of measurements made using these landmarks, can be improved by eliminating or at least reducing tilt in the B-scan at the source of the B-scan, specifically by modifying the acquisition of the B-scan so that the pupil axis of the eye (rather than the visual axis) is aligned with the axial imaging direction of the OCT imaging system. More specifically, the OCT imaging system can be modified to include a fixation target that is arranged to fix the gaze direction of the eye during the acquisition of the B-scan so that the axis corresponding to the pupil axis of the eye in the B-scan is aligned with the direction corresponding to the axial imaging direction of the OCT imaging system in the B-scan. This can not only eliminate or reduce the degree of tilt in the B-scan, but also tends to equalize the visibility or contrast of the representation of the scleral prominence in the B-scan, thereby allowing more accurate geometric measurements of the anterior segment of the eye. It should be understood that although the foregoing discussion has been conducted in the context of a B-scan, the principles described are generally applicable to anterior segment OCT (AS-OCT) images in the form of a C-scan.

[0032] Example embodiments will now be described in detail with reference to the accompanying drawings.

[0033] Figure 1 is a schematic diagram of a system 100 arranged to process AS-OCT images to obtain geometric measurements of an eye according to a first example embodiment herein.

[0034] The system 100 includes an OCT imaging system 110, which is controlled by its controller 115 and includes a fixation target 120. The OCT imaging system 110 is arranged to acquire an AS-OCT image 130 of an eye 140, which includes a representation of a (opposite) portion of the scleral process of the eye 140 (e.g., a portion of the scleral process located at the opposite side of the anterior chamber of the eye 140). The AS-OCT image 130 of the eye 140 may be a whole chamber AS-OCT image, which covers the entire anterior chamber of the eye 140 and surrounding portions of the anterior segment of the eye 140, including the (opposite) portion of the scleral process of the eye 140. During acquisition of the AS-OCT image 130, the fixation target 120 is arranged to fix the gaze direction 151 of the eye 140 so that the axis corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image.

[0035] The system 100 further comprises data processing hardware 150 arranged to process the AS-OCT image 130 to obtain geometrical measurements 160 of the eye 140. The geometrical measurements 160 of the eye 140 are obtained by the data processing hardware 150 based on the positions of the representations of (relative) parts of the scleral prominences of the eye 140 in the AS-OCT image 130 and, depending on the selected geometrical measurements 160, based on the positions of the representations of one or more other anatomical features of the eye 140 in the AS-OCT image 130, as described in more detail below. Although the data processing hardware 150 may be provided as a separate component from the OCT imaging system 110 as in the present example embodiment, the data processing hardware 150 may alternatively be formed as part of the OCT imaging system 110, the functions of which are performed, for example, by the controller 115.

[0036] As in the present example embodiment, the OCT imaging system 110 may be a point scanning Fourier domain OCT imaging system. However, the form of the OCT imaging system 110 is not limited thereto, and may alternatively take the form of a time domain system, and further may alternatively be a line scanning or full field OCT imaging system. Furthermore, the OCT imaging system 110 may be operable to acquire both AS-OCT images and posterior segment OCT (PS-OCT) images of the eye 140.

[0037] Figure 2is a schematic diagram of an AS-OCT image 130 in the exemplary form of a whole chamber B-scan 200, which represents a cross-section of the entire anterior chamber of the eye 140 and surrounding portions of the anterior segment of the eye 140, including an opposing portion of the scleral process of the eye 140. The B-scan 200 includes a direction 201 corresponding to the axial imaging direction 111 of the OCT imaging system 110, an axis 203 corresponding to the pupil axis 153 of the eye 140, and a second axis 202 corresponding to the visual axis of the eye 140, which defines the gaze direction 151 of the eye 140. However, the AS-OCT image 130 may more generally be a B-scan that does not include the entire anterior chamber of the eye 140, but nonetheless includes a representation of a (opposite) portion of the scleral process of the eye 140 (e.g., the B-scan covers a segment of the anterior chamber of the eye 140 along the axial direction, which segment includes the portion of the scleral process of the eye 140). As described below, the AS-OCT image 130 may alternatively be a C-scan including a representation of a (relative) portion of the scleral process of the eye 140 , which may encompass the entire anterior chamber of the eye 140 and surrounding portions of the anterior segment of the eye 140 .

[0038] The fixation target 120 is arranged to fix the gaze direction 151 of the eye 140 (i.e., a direction away from the eye 140 along the visual axis of the eye 140) during acquisition of the AS-OCT image 130 so that an axis 203 corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with a direction 201 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130. That is, the fixation target 120 is arranged so that when the eye 140 fixates the fixation target 120 so as to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130, the axis 203 representing the pupil axis 153 of the eye 140 in the AS-OCT image 130 is parallel to the direction 201 representing the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130. More generally, axis 203 may be aligned with direction 201 within a predetermined tolerance (e.g., 0.01 degrees, 0.1 degrees, or 1 degree). Figure 2 , where the arrangement of the fixation target 120 has fixed the gaze direction 151 of the eye 140 during the acquisition of the B-scan 200, so that the axis 203 corresponding to the pupil axis 153 of the eye 140 in the B-scan 200 is parallel to the direction 201 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the B-scan 200.

[0039] As in the present example embodiment, the position of the fixation target 120 relative to the eye 140 may be controlled by the OCT imaging system 110 (specifically by the controller 115 thereof) so as to control the gaze direction 151 of the eye 140 when the eye 140 is fixated on the fixation target 120. The process by which the OCT imaging system 110 sets the fixation target 120 to fix the gaze direction 151 of the eye 140 during the acquisition of the AS-OCT image 130 is described in more detail below, such that an axis 203 corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with a direction 201 in the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110. However, the position of the fixation target 120 can alternatively be set during manufacturing relative to an expected position of the eye 140 (i.e., a position set by the position of a chin rest, etc., where the eye 140 is positioned relative to the OCT imaging system 110 so that the OCT imaging system 110 acquires the AS-OCT image 130) such that during acquisition of the AS-OCT image 130, an axis 203 in the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with a direction 201 in the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0040] The fixation target 120 may be integrated into the sample arm of the OCT imaging system 110 by coupling light from the fixation target 120 into the optical path of the sample arm using a beam splitter / beam combiner, as in the present example embodiment. In the case where the OCT imaging system 110 is a line scan or point scan OCT imaging system, the beam splitter / beam combiner may be placed between the scanning mirrors and the eye 140 or before the at least one scanning mirror in the optical path toward the eye 140. In the case where the fixation target 120 is placed before the at least one scanning mirror in the optical path toward the eye 140, the light from the fixation target 120 may be pulsed to coincide with a predefined position of the at least one scanning mirror, thereby ensuring that the position of the fixation target 120 remains fixed relative to the viewing angle of the eye 140 as the at least one scanning mirror moves.

[0041] The OCT imaging system 110 can set the position of the fixation target 120 to achieve the alignment between the above-mentioned direction 201 and the axis 203 using techniques known to those skilled in the art. For example, the position of the fixation target 120 relative to the eye 140 can be set to achieve the alignment between the above-mentioned direction 201 and the axis 203 based on a ray tracing model of the eye and the optical devices of the OCT imaging system 110 between the fixation target 120 and the eye 140. Alternatively, the optical path length L from a point within the eye 140 (e.g., the center of the pupil or the geometric center of the eyeball) to the fixation target 120 can be used to estimate the position of the fixation target 120 relative to the eye 140 required to achieve the alignment between the above-mentioned direction 201 and the axis 203 based on trigonometry.

[0042] Figure 3 is a schematic diagram of an example embodiment of an OCT imaging system 110 in which a fixation target 120 takes the form of a graphic 310 displayed by a display device 300 forming part of the OCT imaging system 110. The display position of the graphic 310 relative to the eye 140 can be controlled by the controller 115 to control the gaze direction 151 of the eye 140 when the eye 140 is fixated on the graphic 310. In other words, the position of the eye 140 relative to the OCT imaging system 110 is fixed (e.g., by placing the patient's chin on a chin rest of the OCT imaging system 110), and the display position of the graphic 310 moves around the displayable area of ​​the display device 300, as shown. Figure 3 As shown by the arrow in , in order to move (manipulate) the gaze direction 151 of the eye 140 when the eye 140 is looking at the graphic 310. Although the graphic 310 is Figure 3 140, but it should be understood that the form of the graphic is not limited thereto and may alternatively be provided in a cross, a circle, or any shape that the eye 140 can gaze at. In addition, the fixation target 120 may be implemented in a form other than a display device. For example, the fixation target 120 may include a light source (e.g., a light emitting diode) attached to an actuator that may be controlled by the controller 115 to move the light source relative to the eye 140, thereby controlling the gaze direction 151 of the eye 140 when the eye 140 gazes at the light source.

[0043] The data processing hardware 150 is arranged to process the AS-OCT image 130 to obtain a representation of (relative) parts of the scleral protrusions of the eye 140 in the AS-OCT image 130 at corresponding positions in the AS-OCT image 130, details of which are described below with reference to Figure 5 The data processing hardware 150 is also arranged to obtain (or determine) a geometric measurement result 160 based on the acquired position, as described below with reference to Figure 5 The process S53 is described.

[0044] The data processing hardware 150 and the controller 115 of the OCT imaging system 110 may be provided in any suitable form, such as as Figure 4 Programmable signal processing hardware 400 of the type schematically shown in FIG.

[0045] The programmable signal processing device 400 includes a communication interface (I / F) 410 for externally communicating data. In the case where the device 400 implements the data processing hardware 150, the I / F 410 can be arranged to receive the AS-OCT image 130 from the OCT imaging system 110, and output the geometric measurement results 160 and / or a graphical representation thereof (e.g., overlaid on the AS-OCT image 130) for display on a display such as a computer screen. In the case where the device 400 implements the controller 115 of the OCT imaging system 110, the I / F 410 can be arranged to receive instructions for acquiring the AS-OCT image 130 (e.g., a target position and a command to start an acquisition procedure), and output the AS-OCT image 130.

[0046] The signal processing hardware 400 also includes a processor (e.g., a central processing unit CPU and / or a graphics processing unit GPU) 420, a working memory 430 (e.g., a random access memory), and an instruction storage device 440 storing a computer program 445, which includes computer-readable instructions that, when executed by the processor 420, cause the processor 420 to perform various functions, including those of the data processing hardware 150 and / or the controller 115 of the OCT imaging system 110 described herein. The working memory 430 stores information used by the processor 420 during execution of the computer program 445. The instruction storage device 440 may include a ROM (e.g., in the form of an electrically erasable programmable read-only memory (EEPROM) or flash memory) preloaded with computer-readable instructions. Alternatively, the instruction storage device 440 may include a RAM or similar type of memory, and the computer-readable instructions of the computer program 445 may be input to the instruction storage device 440 from a computer program product (e.g., a non-transitory computer-readable storage medium 450 in the form of a CD-ROM, DVDROM, etc.) or a computer-readable signal 460 carrying the computer-readable instructions. In any case, the computer program 445, when executed by the processor 420, causes the processor 420 to perform the functions of the data processing hardware 150 and / or the controller 115 of the OCT imaging system 110, as described herein. In other words, the data processing hardware 150 of the first example embodiment may include a computer processor 420 and a memory 440 storing computer-readable instructions, which, when executed by the computer processor 420, causes the computer processor 420 to process the AS-OCT image 130 to obtain a representation of a (relative) portion of the scleral protrusion of the eye 140 in the AS-OCT image 130 at a corresponding position in the AS-OCT image 130, and to obtain geometric measurements 160 based on the acquired position. Similarly, the controller 115 of the OCT imaging system 110 of the first example embodiment may include a computer processor 420 and a memory 440 storing computer readable instructions that, when executed by the computer processor 420, cause the computer processor 420 to perform the processes described below in this example embodiment (including Figure 5 The process of S51 and Figure 6 , Figure 7 , Fig. 9 and Fig.10 process).

[0047] It should be noted that the functions of both the data processing hardware 150 and the controller 115 of the OCT imaging system 110 may be performed by the programmable signal processing hardware 400. Furthermore, the data processing hardware 150 and / or the controller 115 of the OCT imaging system 110 may alternatively be implemented in non-programmable hardware (such as an ASIC, FPGA, or other integrated circuit dedicated to performing the described functions of the data processing hardware 150 and / or the controller 115 of the OCT imaging system 110, as the case may be) or in such non-programmable hardware and as described above with reference to Figure 4 The invention is implemented in a combination of programmable hardware as described.

[0048] Figure 5 is a flow chart illustrating a process by which an AS-OCT image 130 acquired by an OCT imaging system 110 may, as in this example embodiment, be processed by data processing hardware 150 to obtain geometric measurements 160 of an eye 140 .

[0049] exist Figure 5 In process S51, the OCT imaging system 110 acquires the AS-OCT image 130 while fixing the gaze direction 151 of the eye 140 by the eye 140 gazing at the fixation target 120, so that the axis 203 corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with the direction 201 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130. The process of setting the fixation target 120 by the controller 115 of the OCT imaging system 110 to fix the gaze direction 151 of the eye 140 in this manner is described in more detail below. However, as previously described, the fixation target 120 may alternatively be set in the aforementioned manner during the manufacture of the OCT imaging system 110 to fix the direction 151 of the eye 140.

[0050] exist Figure 5In process S52, the data processing hardware 150 processes the acquired AS-OCT image 130 to obtain the corresponding position of the (relative) part of the scleral protrusion of the eye 140 represented in the AS-OCT image 130 in the AS-OCT image 130. This can be achieved using any technology well known to those skilled in the art. For example, the data processing hardware 150 can use a deep learning method that uses a trainable multi-layer neural network to identify the position of the (relative) part of the scleral protrusion of the eye 140 in the B-scan 200. As another example, the data processing hardware 150 can process the acquired AS-OCT image 130 by causing the acquired AS-OCT image 130 to be displayed to a user on a display screen, and obtain the corresponding positions in the AS-OCT image 130 of the (relative) portions of the scleral spur of the eye 140 represented in the AS-OCT image 130 by receiving a designation of these positions that has been entered by a user (e.g., using a mouse and / or keyboard, or via one or more touch interactions if the display screen is a touch screen) after the displayed AS-OCT image 130 has been examined. Additional details of example techniques known to those skilled in the art are provided in "Deep Neural Network for Scleral Spur Detection in Anterior Segment OCT Images: Chinese American Eye Study," published by Benjamin Y. Xu et al. in Transl Vis Sci Technol. on March 30, 2020, which is hereby incorporated by reference in its entirety.

[0051] exist Figure 5In process S53, the data processing hardware 150 obtains (or determines) a geometric measurement result 160 based on the acquired position. This can be achieved using techniques well known to those skilled in the art. For example, the data processing hardware 150 can determine the ACW of the eye 140 as the distance between the acquired positions of the representation of the portion of the scleral protrusion in the B-scan 200. As another example, the data processing hardware 150 can determine any of the AOD, TIA, TISA and ACA of the eye 140 based on the acquired positions of the representation of the portion of the scleral protrusion in the B-scan 200 and the boundaries of the anterior chamber in the B-scan 200 (e.g., the anterior iris surface and the posterior corneal surface). The boundaries of the anterior chamber in the B-scan 200 can be determined by the data processing hardware 150 using anterior chamber segmentation techniques well known to those skilled in the art (such as anterior chamber segmentation using deep learning methods). Additional details on determining anterior chamber angle parameters can be found in “Automatic measurement of anterior chamber angle parameters in AS-OCT images using deep learning,” Guangqian Yang et al., 2023, Biomed. Opt. Express, Vol. 14, pp. 1378-1392, which is hereby incorporated by reference in its entirety.

[0052] Figure 6 is a flow chart illustrating a process by which the controller 115 of the OCT imaging system 110 may, as in the present example embodiment, Figure 5 During the acquisition of the AS-OCT image 130 in step S51 , the fixation target 120 is set to fix the gaze direction 151 of the eye 140 .

[0053] exist Figure 6 In optional process S61, the controller 115 obtains the laterality of the eye 140 (i.e., whether the eye 140 is the right eye or the left eye of the subject). For example, the controller 115 can obtain an indication of the laterality of the eye 140 by receiving input from a clinician operating the OCT imaging system 110. However, alternatively, the indication of the laterality of the eye 140 can be automatically determined by the controller 115 using techniques known to those skilled in the art. As described above, process S61 is optional and may not be performed, as described below with respect to alternative implementations of the first example embodiment.

[0054] exist Figure 6In process S62, the controller 115 obtains an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 (e.g., as defined by an angle in a polar coordinate system, or as defined by two angles in a spherical coordinate system) based on the measurement results of the relative orientations of the pupil axis and the visual axis in the eye in the eye sample set and the obtained laterality of the eye 140. The controller 115 may obtain an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 ... Figure 4 The apparatus may obtain an indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye from data stored in the memory 440 of the remote server. However, the indication I of the orientation may alternatively be obtained in other ways, such as by downloading the indication I from a remote server, or by retrieving the measurement results of the relative orientation of the pupil axis and the visual axis in the eyes in the eye sample set (corresponding to the acquired laterality of the eye 140) from the remote server and calculating a representative value (e.g., an average or median) of the retrieved measurement results as the indication I.

[0055] As in this example embodiment, the measurements of the relative orientation of the pupil axis and the visual axis in the eyes in the eye sample set (ie, the set sampled from the population) may include corresponding first values The first value indicating a first component of the kappa angle of the right eye (i.e., the angle between the pupil axis and the visual axis in the eye) in the nasal-temporal direction (e.g., where a positive angle direction is from the nasal side to the temporal side of the eye) and a second component of the kappa angle of the right eye in the superior-inferior direction (e.g., where a positive angle direction is from the superior side to the inferior side of the eye), and the measurement result also includes a corresponding second value The second value Indicates a first component of the kappa angle of the left eye in the nasotemporal direction and a second component of the kappa angle of the left eye in the up-down direction. Therefore, the memory accessed by the controller 115 may store a first value A representative value (such as the mean or median) of The controller 115 can select a representative value of the first value The representative value and the second value Get the orientation indication from the representative value of as a representative value corresponding to an indication of the laterality of the eye 140. However, the memory of the OCT imaging system 110 may alternatively store the first value and the second value And the controller 115 may retrieve a set of values ​​corresponding to the indication of the laterality of the eye 140 and use the set of values ​​to calculate a representative value as an indication of orientation.

[0056] Furthermore, the measurement of the relative orientation of the pupil axis and the visual axis in the eyes in the eye sample set may take other forms. For example, assuming symmetry between the right eye and the left eye in the eye sample set, the measurement of the relative orientation may include a value of The value Indicating a first component of the kappa angle in the nasotemporal direction and a second component of the kappa angle in the superior-inferior direction for a corresponding eye in the eye sample set. The acquired indication of the laterality of the eye 140 can therefore be used to interpret the measurement results of the relative orientation in the reference frame of the OCT imaging system 110 to obtain the indication of orientation I, because the nasotemporal direction is flipped between the right eye and the left eye (i.e., the directions defining positive angles in the right eye and the left eye are reversed relative to the common reference frame).

[0057] Furthermore, the indication of orientation I may approximate, in one direction, the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140. In this case, the measurement of relative orientation may include a value or value One dimension of the kappa angle is indicated in the nasotemporal direction or in the superior-inferior direction, respectively (and optionally for the right eye or the left eye, or when symmetry is assumed), as described in more detail below. Although the relative orientation is described above as relative to the nasotemporal direction and the superior-inferior direction, any two orthogonal directions in the plane defined by the nasotemporal direction and the superior-inferior direction (or any first direction and a second direction having at least a component orthogonal to the first direction) can be used as a reference system.

[0058] Figure 7 In the first alternative embodiment of this example embodiment, Figure 6 140 , by which the controller 115 of the OCT imaging system 110 may obtain an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140. The inventors have recognized that, although in some cases it may be difficult to identify the visual axis 152 of the eye 140 within the AS-OCT image of the eye 140 based on anatomical features of the eye 140, by manipulating the gaze direction 151 of the eye 140 using the fixation target 120, the visual axis 152 may be arranged to be parallel to the axial imaging direction 111 of the OCT imaging system 110, thereby allowing the orientation of the pupil axis 153 of the eye 140 to be determined relative to the hypothetical position of the visual axis of the eye 140 (which may be more easily identified based on at least the anatomical features of the eye 130 in the AS-OCT image). In the case of using the alternative process described below, the orientation of the pupil axis 153 of the eye 140 may be omitted. Figure 6 Process S61 in .

[0059] exist Figure 7In process S71 of the embodiment, the controller 115 controls the OCT imaging system 110 to acquire a calibration B-scan of at least a portion of the anterior segment of the eye 140 for determining an orientation of an axis corresponding to a pupil axis 153 of the eye 140 in the calibration B-scan relative to a direction corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the calibration B-scan (e.g., by causing the calibration B-scan to have an axis corresponding to the pupil axis 153 of the eye 140). The controller 115 controls the OCT imaging system 110 to acquire a calibration B-scan parallel to the B-scan 200 by setting a gaze direction 151 of the eye 140 using the fixation target 120 so that a visual axis 152 of the eye 140 is aligned with the axial imaging direction 111 of the OCT imaging system 110. That is, during acquisition of the calibration B-scan, the controller 115 sets the position of the fixation target 120 relative to the eye 140 so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the gaze direction 151 of the eye 140 (along which the visual axis of the eye 140 extends) is aligned with the axial imaging direction 111 of the OCT imaging system 110. The calibration B-scan may encompass the entire anterior chamber of the eye 140 and surrounding portions of the anterior segment of the eye 140, and may include at least a portion of the scleral process of the eye 140. Note that the calibration B-scan is acquired prior to the B-scan 200, so it is parallel to the expected or predetermined plane of the B-scan 200.

[0060] Figure 8 is a schematic diagram of an example calibration B-scan 800 acquired in the manner described above by the OCT imaging system 110. As shown, an axis 802 in the calibration B-scan 800 corresponding to the visual axis of the eye 140 is parallel to a direction 801 in the calibration B-scan 800 corresponding to the axial imaging direction 111 of the OCT imaging system 110, but more generally, the axis 802 may be aligned with the direction 801 within a predetermined tolerance (e.g., 0.01 degrees, 0.1 degrees, or 1 degree) relative to the direction 801.

[0061] exist Figure 7In process S72, the controller 115 determines the orientation of the axis corresponding to the pupil axis 153 of the eye 140 in the calibration B-scan 800 relative to the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the calibration B-scan 800 as an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140. Since the calibration B-scan 800 is parallel to the B-scan 200, the orientation of the pupil axis 153 of the eye 140 in the calibration B-scan 800 relative to the visual axis 152 of the eye 140 will correspond to the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 in the B-scan 200 subsequently acquired by the OCT imaging system 110, and thus the orientation of the pupil axis 153 of the eye 140 in the calibration B-scan 800 relative to the visual axis 152 of the eye 140 can be used as an indication I in the calibration B-scan 800. Figure 6 The acquired orientation indication is applied for correction purposes in process S63, which will be described in detail below.

[0062] Fig. 9 is a flow chart illustrating a process by which the controller 115 of the OCT imaging system 110 may, as in a first alternative implementation of the present example embodiment, determine the orientation of an axis in the calibration B-scan 800 corresponding to the pupil axis 153 of the eye 140 relative to a direction in the calibration B-scan 800 corresponding to the axial imaging direction 111 of the OCT imaging system 110, as Figure 7 The same as process S72.

[0063] exist Fig. 9 In process S91 of FIG. 8 , controller 115 identifies (or locates) a representation of an anatomical feature of eye 140 within calibration B-scan 800 for determining an orientation of an axis in calibration B-scan 800 corresponding to pupil axis 153 of eye 140 relative to a direction in the calibration B-scan corresponding to axial imaging direction 111 of OCT imaging system 110. For example, Figure 8In the calibration B-scan 800 of the eye 140, representations of opposing portions 804, 805 of the scleral protuberances of the eye 140 are identified (because the orientation of the pupil axis 153 of the eye 140 in the calibration B-scan 800 relative to the frame of the calibration B-scan 800 can be approximated using a line 806 connecting the opposing portions 804, 805 of the scleral protuberances, which line 806 is expected to be parallel to the pupil plane of the eye 140). However, other anatomical features suitable for this purpose can be identified, such as identifying the pupil in the calibration B-scan 800 to directly obtain the plane of the pupil. Such representations of the scleral protuberances or other anatomical features can be identified using any technique well known to those skilled in the art. For example, the controller 115 can employ a deep learning method that can utilize a trainable multi-layer neural network to identify representations of anatomical features in the calibration B-scan 800. As another example, the controller 115 may process the calibration B-scan 800 by causing the calibration B-scan 800 to be displayed to the user on a display screen, and obtain identification of representations of anatomical features in the calibration B-scan 800 by receiving designations of those locations that have been entered by the user (e.g., using a mouse and / or keyboard, or via one or more touch interactions if the display screen is a touch screen) after examining the displayed calibration B-scan 800.

[0064] exist Fig. 9 In process S92, the controller 115 determines the orientation of the aforementioned axis in the calibration B-scan relative to the aforementioned direction in the calibration B-scan based on the representation of the identified anatomical feature of the eye 140. Figure 8 In the example of calibration B-scan 800 of FIG. 8 , a direction orthogonal to line 806 in the plane of calibration B-scan 800 indicates the direction of axis 803 in calibration B-scan 800. Therefore, this orthogonal direction can be used to determine the orientation of axis 803 in calibration B-scan 800 relative to direction 801 in calibration B-scan 800.

[0065] Fig.10 1 is a flow chart illustrating a second alternative process by which the controller 115 of the OCT imaging system 110 may, as in a second alternative implementation of the present example embodiment, obtain an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140. The second alternative process is similar to the first alternative process, but obtains a three-dimensional orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140, making the second alternative process particularly, but not exclusively, suitable for aligning the pupil axis 153 of the eye 140 with the axial imaging direction 111 of the OCT imaging system 110 in a C-scan (as an AS-OCT image 130). In the case of using the second alternative process described below, the controller 115 of the OCT imaging system 110 may be omitted. Figure 6 Process S61.

[0066] exist Fig.10 In process S101, the controller 115 controls the OCT imaging system 110 to acquire a first calibration B-scan of a first cross-section of at least a portion of an anterior segment of the eye 140, for determining a first orientation of a first axis corresponding to a pupil axis 153 of the eye 140 in the first calibration B-scan relative to a first direction corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the first calibration B-scan (e.g., by making the first calibration B-scan have a first axis corresponding to the pupil axis 153 of the eye 140). Fig.10 In process S101, the controller 115 also controls the OCT imaging system 110 to acquire a second calibration B-scan of a second cross-section of at least a portion of the anterior segment of the eye 140, for determining a second orientation of a second axis corresponding to a pupil axis 153 of the eye 140 in the second calibration B-scan relative to a second direction corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the second calibration B-scan (e.g., by causing the second calibration B-scan to have a second axis corresponding to the pupil axis 153 of the eye 140). Here, the plane of the first cross-section is perpendicular to the plane of the second cross-section. The controller 115 achieves this by controlling the fixation target 120 to set the gaze direction 151 of the eye 140 so that the visual axis 152 of the eye 140 is aligned with the axial imaging direction 111 of the OCT imaging system 110. That is, during the acquisition of the first calibration B-scan and the second calibration B-scan, the controller 115 sets the position of the fixation target 120 relative to the eye 140 so that when the gaze direction of the eye 140 is fixed by the fixation target 120 at the set position, the gaze direction 151 of the eye 140 (along which the visual axis of the eye 140 extends) is aligned with the axial imaging direction 111 of the OCT imaging system 110. The first cross-section and the second cross-section may each be a cross-section of the entire anterior chamber of the eye 140 and the surrounding portion of the anterior segment of the eye 140, and may each include at least a portion of the scleral process of the eye 140.

[0067] Fig.11A and Fig. 11B Schematic diagrams of an example first calibration B-scan 1100 and an example second calibration B-scan 1150, respectively. As shown, respective axes 1102, 1152 in the calibration B-scans 1100, 1150 corresponding to the visual axis of the eye 140 are parallel to respective directions 1101, 1151 in the calibration B-scans 1100, 1150 corresponding to the axial imaging direction 111 of the OCT imaging system 110, but more generally, they may be aligned with their respective directions 1101, 1151 within a predetermined tolerance (e.g., 0.01 degrees, 0.1 degrees, or 1 degree) relative to their respective directions 1101, 1151.

[0068] exist Fig.10In process S102, the controller 115 determines a first orientation of a first axis corresponding to the pupil axis 153 of the eye 140 in the first calibration B-scan relative to a first direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the first calibration B-scan. Fig.11A , the OCT imaging system 110 determines the first orientation as the orientation of an axis 1103 corresponding to the pupil axis 153 of the eye 140 relative to a direction 1101 in the first calibration B-scan 1100 corresponding to the axial imaging direction 111 of the OCT imaging system 110. The controller 115 may determine the first orientation as the orientation of an axis 1103 corresponding to the pupil axis 153 of the eye 140 relative to a direction 1101 in the first calibration B-scan 1100 corresponding to the axial imaging direction 111 of the OCT imaging system 110. Fig. 9 The process of determining the first orientation is as described in detail above.

[0069] exist Fig.10 In process S103, the controller 115 determines a second orientation of a second axis corresponding to the pupil axis 153 of the eye 140 in the second calibration B-scan relative to a second direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the second calibration B-scan. Fig. 11B , the controller 115 determines the second orientation as the orientation of an axis 1153 corresponding to the pupil axis 153 of the eye 140 relative to a direction 1151 in the second calibration B-scan 1150 corresponding to the axial imaging direction 111 of the OCT imaging system 110. As described above, the controller 115 may determine the second orientation as the orientation of an axis 1153 corresponding to the pupil axis 153 of the eye 140 relative to a direction 1151 in the second calibration B-scan 1150 corresponding to the axial imaging direction 111 of the OCT imaging system 110. Fig. 9 The process is used to determine the second orientation.

[0070] exist Fig.10In process S104, the controller 115 determines an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 based on the first orientation (determined in process S102) and the second orientation (determined in process S103). Because the first cross-section is perpendicular to the second cross-section, the determined first orientation and the determined second orientation define the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 in three dimensions relative to the frame of the first cross-section and / or the second cross-section. Thus, the controller 115 may use the determined first orientation and the determined second orientation as an indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140, or, for example, may resolve the determined first orientation and the determined second orientation into a first component in the subnasal direction (using the acquired indication of the laterality of the eye 140, or, if no indication is acquired, resolving the first component relative to a direction along a horizontal axis that follows the subnasal direction) and a second component in the superior-inferior direction as the indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140. Alternatively, in the case where the AS-OCT image 130 is a B-scan 200, the OCT imaging system 110 may determine the indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 based on the determined first orientation and the determined second orientation by resolving the determined first orientation and the determined second orientation into a plane of a cross section of the B-scan 200 and using this as the determined indication I.

[0071] The first and second alternative processes described above may allow for a patient-specific alignment of the pupil axis 153 of the eye 140 with the axial imaging direction 111 of the OCT imaging system 110 to be performed, thereby further improving the accuracy and reliability of the acquired geometric measurements of the eye 140, due to the fact that the image contrast differences between the representations of the opposing portions of the scleral process of the eye in the AS-OCT image 130 are further reduced. However, the process of the first example embodiment utilizing measurements of relative orientations from a sample set of eyes may allow for a faster alignment without the need to acquire one or more calibration AS-OCT images, thereby reducing the acquisition time of geometric measurements of the eye 140 compared to the alternative implementation. Therefore, this process may be preferred for clinical applications where process efficiency / throughput is important and the achievable improvement in the accuracy of the acquired geometric measurements of the eye 140 may be sufficient that use of the alternative implementation described above is not necessary.

[0072] Return to Figure 6In process S63, the controller 115 sets the fixation target 120 using the acquired indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140, so that the fixation target 120 fixes the gaze direction 151 of the eye 140 during the acquisition of the AS-OCT image 130, so that the axis 203 in the AS-OCT image 130 is aligned with the direction 201 in the AS-OCT image 130. As in the present example embodiment, the OCT imaging system 110 can achieve this by setting the position of the fixation target 120 using the acquired indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140, so that the gaze direction 151 of the eye 140 is aligned with the axial imaging direction 111 of the OCT imaging system 110 within a predetermined tolerance (e.g., 0.01 degrees, 0.1 degrees, or 1 degree). Therefore, Figure 2 The B-scan 200 can be acquired by the OCT imaging system 110 in any cross-sectional plane of the eye 140 and has an axis 203 parallel to the direction 201. Similarly, where the AS-OCT image 130 is provided in the form of an OCT C-scan, as described above, the alignment of the gaze direction 151 of the eye 140 with the axial imaging direction 111 in three-dimensional space can result in the axis corresponding to the pupil axis of the eye 140 in the C-scan being aligned with the direction corresponding to the axial imaging direction 111 in the C-scan.

[0073] However, the controller 115 may alternatively achieve this by using the acquired indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 to set the position of the fixation target 120 so that the projection of the gaze direction 151 of the eye 140 into a plane is aligned with the projection of the axial imaging direction 111 of the OCT imaging system 110 onto the plane, which is the plane in which the B-scan 200 is acquired. For example, the orientation indication I acquired in process S52 (or an alternative embodiment thereof) may provide information to set the position of the fixation target 120 so that the axis 203 in the B-scan 200 is aligned with the direction 201 in the B-scan 200, which is achieved by the controller 115 having parsed the indication acquired in process S62 or S104 into the (expected or predetermined) plane of the B-scan 200, or having acquired the indication in process S72 from a calibration B-scan parallel to the B-scan 200. The controller 115 may alternatively perform such parsing of the acquired indication at this stage. For example, in the case where the acquired indication is an orientation having components in two directions, at this stage, the controller 115 may use information about the position of the plane of the B-scan 200 relative to, for example, the nasotemporal direction and the superior-inferior direction to resolve the acquired indication I of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 into the plane of the B-scan 200 to obtain the orientation of the pupil axis 153 of the eye 140 relative to the visual axis 152 of the eye 140. As the orientation will appear in the B-scan 200. Therefore, the controller 115 can use the orientation The position of the fixation target 120 is set so that the axis 203 in the B-scan 200 is parallel to the direction 201 in the B-scan 200 .

[0074] Alternatively, if the indication I acquired in process S62 is an orientation in one direction (e.g., in the nasotemporal direction or in the superior-inferior direction), the controller 115 can set the position of the fixation target 120 so that if the B-scan 200 or a future B-scan is acquired in a plane in which the acquired orientation is confined to that one direction, the axis in the B-scan corresponding to the pupil axis of the eye 140 will be aligned with the direction in the B-scan corresponding to the axial imaging direction 110 of the OCT imaging system 110.

[0075] Although the fixation target 120 is described above as being arranged to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that the axis 203 corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with the direction 201 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130, the fixation target 120 may alternatively be arranged to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that the axis corresponding to the optical axis of the eye 140 in the AS-OCT image 130 is aligned with the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130. In this case, in Figure 6 In process S62 of , the measurement results instead relate to the relative orientation of the optical axis and the visual axis in the eyes in the eye sample set (i.e., the alpha angle of the eyes in the eye sample set, rather than the kappa angle), and Figure 7 and Fig.10 In an alternative process in the AS-OCT image 130, the corresponding orientation in the corresponding calibration B-scan is the orientation of the corresponding axis corresponding to the optical axis of the eye 140 in the corresponding calibration B-scan relative to the corresponding direction in the corresponding B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110. More generally, the fixation target 120 can be arranged to fix the gaze direction 151 of the eye 140 during the acquisition of the AS-OCT image 130 so that the positions of the representations of the relative portions of the scleral prominence of the eye 140 in the AS-OCT image 130 in the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 (i.e., the axial direction in the AS-OCT image 130 along which the data elements constituting the A-scan are arranged) are level with respect to the direction. For example, in the case where the AS-OCT image 130 is a B-scan, the representations of the relative portions of the scleral prominence will appear at the same height in the B-scan. That is, the positions of the representations of the relative portions of the scleral protrusions of the eye 140 in the AS-OCT image 130 in the axial direction in the AS-OCT image 130 are equal along the direction (within a predetermined tolerance). In other words, the fixation target 120 may be arranged to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image so that the representations of the relative portions of the scleral protrusions of the eye 140 in the AS-OCT image 130 have substantially the same corresponding axial depths (i.e., corresponding positions along the axial direction in the AS-OCT image 130).

[0076] In the above-described first exemplary embodiment and its variations, the control of the fixation target 120 is described so that the image contrast of the representation of the relative parts of the scleral protrusion of the eye 140 in the AS-OCT image 130 acquired by the OCT imaging system 110 is the same or nearly the same. Therefore, the necessary degree of alignment between the axis 203 corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 and the direction 201 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130 can be achieved to achieve an acceptable balance of the scleral protrusion contrast.

[0077] For example, Fig. 12A FIG. 1 shows a B-scan 1200 acquired by a conventional OCT imaging system, to which tilt correction is typically only applied in post-processing. Fig. 12A As can be seen in FIG. 1 , the difference in image contrast between representations 1201 and 1202 of opposing portions of the scleral protrusions of eye 140 is significant, which will limit the accuracy and reliability of geometric measurements of the eye determined based on B-scan 1200. For comparison, Fig. 12B FIG. 1 shows a B-scan 1250 acquired by the OCT imaging system 110 according to this example embodiment. Fig. 12B As can be seen in FIG. 1 , the contrast between representations 1251 and 1252 of opposing portions of the scleral protrusion of eye 140 is approximately equal, which can significantly improve the accuracy and reliability of the geometric measurement results.

[0078] Some of the example embodiments described above are summarized in the following numbered clauses E1 to E14.

[0079] E1. Purpose of a fixation target 120 of an optical coherence tomography (OCT) imaging system for equalizing the image contrast of relative portions of the scleral protrusion of an eye 140 represented in an anterior segment OCT (AS-OCT) image acquired by an OCT imaging system 110, wherein the fixation target 120 is used to equalize the image contrast by fixing a gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that an axis corresponding to a pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with a direction corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130.

[0080] E2. The use according to E1, wherein the fixation target 120 is used to equalize image contrast by fixing the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that an axis corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with a direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130 in the following manner:

[0081] obtaining an indication of the laterality of the eye 140;

[0082] obtaining an indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 based on the measurements of the relative orientations of the pupil axis and the visual axis in the eye in the eye sample set and the obtained indication of the laterality of the eye 140; and

[0083] The position of the fixation target 120 relative to the eye 140 is set using an indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140, so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the axis in the AS-OCT image 130 is aligned with the direction in the AS-OCT image 130.

[0084] E3. The use according to E1, wherein

[0085] The AS-OCT image 130 is a B-scan 200 that includes a representation of the relative portion of the scleral projections of the eye 140, and

[0086] The fixation target 120 is used to equalize image contrast by fixing the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that the axis corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130 in the following manner:

[0087] An indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 is obtained by:

[0088] Acquiring a calibration B-scan 800 of at least a portion of an anterior segment of the eye 140 by setting a gaze direction 151 of the eye 140 using the fixation target 120 such that the visual axis of the eye 140 is aligned with the axial imaging direction 111 of the OCT imaging system 110, wherein the calibration B-scan 800 is parallel to the B-scan 200; and

[0089] determining an orientation of an axis 803 in the calibration B-scan 800 corresponding to a pupil axis 153 of the eye 140 relative to a direction 801 in the calibration B-scan 800 corresponding to an axial imaging direction 111 of the OCT imaging system 110 as an indication of an orientation of the pupil axis 153 of the eye 140 relative to a visual axis of the eye 140; and

[0090] During acquisition of the AS-OCT image 130, the acquired indication of the orientation is used to set the position of the fixation target 120 relative to the eye 140 so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the axis 203 in the B-scan 200 is aligned with the direction 201 in the B-scan 200.

[0091] E4. The use according to E3, wherein the orientation of the axis 803 corresponding to the pupil axis 153 of the eye 140 in the calibration B-scan 800 relative to the direction 801 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the calibration B-scan 800 is determined by:

[0092] identifying representations of anatomical features 804, 805 of the eye 140 within the calibration B-scan 800 for use in determining an orientation of an axis 803 in the calibration B-scan 800 relative to a direction 801 in the calibration B-scan 800; and

[0093] The orientation of the axis 803 in the calibration B-scan 800 relative to the direction 801 in the calibration B-scan 800 is determined based on the identified representations of the anatomical features 804 , 805 of the eye 140 .

[0094] E5. The use according to E1, wherein the fixation target 120 is used to equalize image contrast by fixing a gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 such that an axis corresponding to a pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with a direction corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130 in the following manner:

[0095] An indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 is obtained by:

[0096] acquiring a first calibration B-scan 1100 of a first cross-section of at least a portion of an anterior segment of the eye 140 and a second calibration B-scan 1150 of a second cross-section of at least a portion of the anterior segment of the eye 140 by using the fixation target 120 to set a gaze direction 151 of the eye 140 such that a visual axis of the eye 140 is aligned with an axial imaging direction 111 of the OCT imaging system 110, wherein a plane of the first cross-section is perpendicular to a plane of the second cross-section;

[0097] determining a first orientation of a first axis 1103 in the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 in the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110;

[0098] determining a second orientation of a second axis 1153 in the second calibration B-scan 1150 corresponding to a pupil axis 153 of the eye 140 relative to a second direction 1151 in the second calibration B-scan 1150 corresponding to an axial imaging direction 111 of the OCT imaging system 110; and

[0099] determining an indication of an orientation of a pupil axis 153 of the eye 140 relative to a visual axis of the eye 140 based on the determined first orientation and the determined second orientation; and

[0100] During acquisition of the AS-OCT image 130, an indication of the acquired orientation is used to set the position of the fixation target 120 relative to the eye 140 so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the axis corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130.

[0101] E6. The use according to E5, wherein

[0102] The first orientation is determined by:

[0103] identifying a representation of a first anatomical feature of the eye 140 within the first calibration B-scan 1100 for determining an orientation of a first axis 1103 corresponding to a pupil axis 153 of the eye 140 in the first calibration B-scan 1100 relative to a first direction 1101 in the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110; and

[0104] determining, based on a representation of a first anatomical feature of the eye 140 within the first calibration B-scan 1100, an orientation of a first axis 1103 corresponding to a pupil axis 153 of the eye 140 in the first calibration B-scan 1100 relative to a first direction 1101 corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the first calibration B-scan 1100,

[0105] And the second orientation is determined by:

[0106] identifying a representation of a second anatomical feature of the eye 140 within the second calibration B-scan 1150 for determining an orientation of a second axis 1153 corresponding to a pupil axis 153 of the eye 140 in the second calibration B-scan 1150 relative to a second direction 1151 in the second calibration B-scan 1150 corresponding to an axial imaging direction 111 of the OCT imaging system 110; and

[0107] Based on the representation of a second anatomical feature of the eye 140 within the second calibration B-scan 1150, the orientation of a second axis 1153 corresponding to the pupil axis 153 of the eye 140 in the second calibration B-scan 1150 relative to a second direction 1151 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the second calibration B-scan 1150 is determined.

[0108] E7. The use according to any one of E1 to E6, wherein the fixation target 120 comprises a graphic 310 displayed by a display device 300, wherein the display position of the graphic 310 relative to the eye 140 is controllable so as to control the gaze direction 151 of the eye 140 when the eye 140 gazes at the graphic 310.

[0109] E8. A method of processing an anterior segment optical coherence tomography (AS-OCT) image acquired by an OCT imaging system 110 to obtain geometric measurements 160 based on one or more anatomical features in the AS-OCT image 130, the AS-OCT image including a representation of relative portions of a scleral protuberance of an eye, the method comprising:

[0110] acquiring S51 an AS-OCT image 130 while fixing a gaze direction 151 of the eye 140 by the eye 140 gazing at a fixation target 120 such that an axis in the AS-OCT image 130 corresponding to a pupil axis 153 of the eye 140 is aligned with a direction in the AS-OCT image 130 corresponding to an axial imaging direction 111 of the OCT imaging system 110;

[0111] Processing the AS-OCT image 130 acquired at S52 to acquire the representation of the relative portions of the scleral protrusions of the eye 140 in the AS-OCT image 130 at the corresponding positions in the AS-OCT image 130; and

[0112] Based on the position in the acquired AS-OCT image 130 , geometrical measurements 160 are obtained S53 .

[0113] E9. The method according to E8 further includes setting the fixation target 120 to fix the gaze direction 151 of the eye 140 during the acquisition of the AS-OCT image 130 by:

[0114] Obtaining S61 an indication of the laterality of the eye 140;

[0115] obtaining S62 an indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 based on the measurements of the relative orientations of the pupil axis and the visual axis in the eye in the eye sample set and the obtained indication of the laterality of the eye 140; and

[0116] The position of the fixation target 120 relative to the eye 140 is set using the indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 obtained by S63, so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the axis in the AS-OCT image 130 is aligned with the direction in the AS-OCT image 130.

[0117] E10. The method of E8, wherein the AS-OCT image 130 is a B-scan 200 including a representation of an opposing portion of a scleral protrusion of the eye, and the fixation target 120 is set during acquisition of the B-scan 200 to fix the gaze direction 151 of the eye 140 by:

[0118] An indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 is obtained by:

[0119] acquiring S71 a calibration B-scan 800 of at least a portion of an anterior segment of the eye 140 by setting a gaze direction 151 of the eye 140 using the fixation target 120 so that the visual axis of the eye 140 is aligned with the axial imaging direction 111 of the OCT imaging system 110, wherein the calibration B-scan 800 is parallel to the B-scan 200; and

[0120] determining S72 an orientation of an axis 803 in the calibration B-scan 800 corresponding to a pupil axis 153 of the eye 140 relative to a direction 801 in the calibration B-scan 800 corresponding to an axial imaging direction 111 of the OCT imaging system 110 as an indication of an orientation of the pupil axis 153 of the eye 140 relative to a visual axis of the eye 140; and

[0121] During acquisition of the AS-OCT image 130, the indication of the orientation acquired by S63 is used to set the position of the fixation target 120 relative to the eye 140 so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the axis in the B-scan is aligned with the direction in the B-scan.

[0122] E11. The method according to E10, wherein the orientation of axis 803 in calibration B-scan 800 relative to direction 801 in calibration B-scan 800 is determined by:

[0123] identifying S91 a representation of anatomical features 804, 805 of the eye 140 within the calibration B-scan 800 for use in determining an orientation of an axis 803 in the calibration B-scan 800 relative to a direction 801 in the calibration B-scan 800; and

[0124] An orientation of an axis 803 in the calibration B-scan 800 relative to a direction 801 in the calibration B-scan 800 is determined S92 based on the identified representations of the anatomical features 804 , 805 of the eye 140 .

[0125] E12. The method according to E8, wherein during the acquisition of the B-scan 200, the fixation target 120 is set to fix the gaze direction 151 of the eye 140 by:

[0126] An indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 is obtained by:

[0127] Acquire S101 a first calibration B-scan 1100 of a first cross-section of at least a portion of an anterior segment of the eye 140 and a second calibration B-scan 1150 of a second cross-section of at least a portion of an anterior segment of the eye 140, wherein a plane of the first cross-section is perpendicular to a plane of the second cross-section, and set a gaze direction 151 of the eye 140 using a fixation target 120 such that a visual axis of the eye 140 is aligned with an axial imaging direction 111 of the OCT imaging system 110, thereby acquiring the first calibration B-scan 1100 and the second calibration B-scan 1150;

[0128] Determining S102 a first orientation of a first axis 1103 corresponding to a pupil axis 153 of the eye 140 in the first calibration B-scan 1100 relative to a first direction 1101 corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the first calibration B-scan 1100;

[0129] Determine S103 a second orientation of a second axis 1153 corresponding to pupil axis 153 of eye 140 in second calibration B-scan 1150 relative to a second direction 1151 corresponding to axial imaging direction 111 of OCT imaging system 110 in second calibration B-scan 1150; and

[0130] determining S104 an indication of an orientation of a pupil axis 153 of the eye 140 relative to a visual axis of the eye 140 based on the determined first orientation and the determined second orientation; and

[0131] During the acquisition of the AS-OCT image 130, the indication of the orientation acquired by S63 is used to set the position of the fixation target 120 relative to the eye 140, so that when the gaze direction 151 of the eye 140 is fixed by the fixation target 120 at the set position, the axis corresponding to the pupil axis 153 of the eye 140 in the AS-OCT image 130 is aligned with the direction corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the AS-OCT image 130.

[0132] E13. The method according to E12, wherein

[0133] The orientation of the first axis 1103 in the first calibration B-scan 1100 relative to the first direction 1101 in the first calibration B-scan 1100 is determined by:

[0134] identifying S91 a representation of a first anatomical feature of the eye 140 within the first calibration B-scan 1100 for determining an orientation of a first axis 1103 corresponding to a pupil axis 153 of the eye 140 in the first calibration B-scan 1100 relative to a first direction 1101 corresponding to an axial imaging direction 111 of the OCT imaging system 110 in the first calibration B-scan 1100; and determining S92 an orientation of the first axis 1101 corresponding to the pupil axis 153 of the eye 140 in the first calibration B-scan 1100 relative to a first direction 1103 corresponding to the axial imaging direction 111 of the OCT imaging system 110 in the first calibration B-scan 1100 based on the representation of the first anatomical feature of the eye 140 within the first calibration B-scan 1100, and

[0135] The orientation of the second axis 1153 in the second calibration B-scan 1150 relative to the second direction 1151 in the second calibration B-scan 1150 is determined by:

[0136] Identify S91 the representation of the second anatomical feature of the eye 140 in the second calibration B-scan 1150, and use it to determine the orientation of the second axis 1153 corresponding to the pupil axis 153 of the eye 140 in the second calibration B-scan 1150 relative to the second direction 1151 in the second calibration B-scan 1150 corresponding to the axial imaging direction 111 of the OCT imaging system 110; and determine S92 the orientation of the second axis 1153 corresponding to the pupil axis 153 of the eye 140 in the second calibration B-scan 1150 relative to the second direction 1151 in the second calibration B-scan 1150 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0137] E14. A method according to any one of E8 to E13, wherein the geometric measurement result 160 is a measurement result of the anterior chamber angle of the eye 140.

[0138] In the foregoing description, example aspects have been described with reference to several example embodiments. Therefore, the description should be regarded as illustrative rather than restrictive. Similarly, the drawings shown in the accompanying drawings highlighting the features and advantages of the example embodiments are presented for illustrative purposes only. The architecture of the example embodiments is sufficiently flexible and configurable that it can be utilized in ways other than those shown in the accompanying drawings.

[0139] In an example embodiment, some aspects of the examples given herein, such as the functionality of the controller 115 and / or the data processing hardware 150, may be provided as a computer program or software, such as one or more programs having instructions or sequences of instructions, included or stored in an article of manufacture, such as a machine-accessible or machine-readable medium, an instruction storage device, or a computer-readable storage device, each of which may be non-transitory. The program or instructions on a non-transitory machine-accessible medium, a machine-readable medium, an instruction storage device, or a computer-readable storage device may be used to program a computer system or other electronic device. The machine-readable medium or computer-readable medium, the instruction storage device, and the storage device may include, but are not limited to, a floppy disk, an optical disk, and a magneto-optical disk or other types of media / machine-readable media / instruction storage devices / storage devices suitable for storing or transmitting electronic instructions. The techniques described herein are not limited to any particular software configuration. They may find application in any computing or processing environment. As used herein, the terms "computer-readable", "machine accessible medium", "machine-readable medium", "instruction storage", and "computer-readable storage device" shall include any medium that can store, encode, or transmit instructions or sequences of instructions for execution by a machine, computer, or computer processor and cause the machine / computer / computer processor to perform any of the methods described herein. Furthermore, it is common in the art to refer to software in one or another form (e.g., program, procedure, process, application, module, unit, logic, etc.) as taking an action or causing a result. Such an expression is merely a shorthand way of stating that execution of the software by a processing system causes the processor to perform an action to produce a result.

[0140] Some or all of the functionality of controller 115 and / or data processing hardware 150 may also be implemented through the preparation of application specific integrated circuits, field programmable gate arrays or by interconnecting an appropriate network of conventional component circuits.

[0141] The computer program product may be provided in the form of one or more storage media, instruction storage means or storage devices having stored thereon or therein instructions that can be used to control or cause a computer or computer processor to perform any process of the example embodiments described herein. The storage medium / instruction storage means / storage device may include, by way of example and without limitation, an optical disk, ROM, RAM, EPROM, EEPROM, DRAM, VRAM, flash memory, flash memory card, magnetic card, optical card, nanosystem, molecular memory integrated circuit, RAID, remote data storage / archiving / warehousing device, and / or any other type of device suitable for storing instructions and / or data.

[0142] Some embodiments stored on any one of one or more computer-readable media, instruction storage devices, or storage devices include hardware for controlling the system and software for enabling the system or microprocessor to interact with a human user or other mechanism using the results of the example embodiments described herein. Such software may include, without limitation, device drivers, operating systems, and user applications. Ultimately, as described above, such computer-readable media or storage devices also include software for executing example aspects of the present invention.

[0143] Software modules for implementing the processes described herein are included in the programming and / or software of the system. In some example embodiments herein, the modules include software, but in other example embodiments herein, the modules include hardware or a combination of hardware and software.

[0144] Although various exemplary embodiments of the present invention have been described above, it should be understood that they are presented by way of example and not limitation. It will be apparent to those skilled in the relevant art that various changes may be made in form and detail. For example, although Figures 5 to 7 , Fig. 9 and Fig.10 The processes shown in are performed in the order indicated by the arrows between the steps, but some processes can be performed in parallel. For example, Fig.10 The processes S102 and S103 in the embodiment may be executed in parallel. Therefore, the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the appended claims and their equivalents.

[0145] Furthermore, the purpose of the Abstract is to enable patent offices and the public in general, and especially scientists, engineers, and practitioners in the art who are not familiar with patent or legal terminology or wording, to quickly determine the nature and essence of the technical disclosure of the present application based on a cursory inspection. The Abstract is not intended to be limiting in any way with respect to the scope of the example embodiments presented herein. It should also be understood that any process recited in the claims need not be performed in the order presented.

[0146] Although this specification contains many specific embodiment details, these should not be understood as limitations on the scope of any invention or content that may be claimed, but should be understood as descriptions of features specific to the specific embodiments described herein. Certain features described in this specification in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. In addition, although features may be described above as acting in a specific combination and even initially claimed as such, one or more features from the claimed combination may be deleted from the combination in some cases, and the claimed combination may be directed to a sub-combination or a variant of the sub-combination.

[0147] In some cases, multitasking and parallel processing may be advantageous. In addition, the separation of the various components in the above-described embodiments should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

[0148] Now that some illustrative embodiments and embodiments have been described, it is apparent that the foregoing embodiments are illustrative rather than restrictive and have been presented by way of example. In particular, although many of the examples presented herein relate to specific combinations of devices or software elements, these elements may be combined in other ways to achieve the same purpose. Actions, elements, and features discussed only in conjunction with one embodiment are not intended to be excluded from similar roles in the embodiments or other embodiments.

Claims

1. A system (100) arranged to process an anterior segment optical coherence tomography (AS-OCT) image (130) comprising a representation of a portion of a scleral protrusion of an eye (140) to obtain geometric measurements (160) of the eye (140), the system (100) comprising: Data processing hardware (150), the data processing hardware (150) being arranged to: processing the AS-OCT image (130) to obtain the corresponding position of the portion of the scleral protrusion of the eye (140) represented in the AS-OCT image (130) in the AS-OCT image (130); as well as obtaining the geometric measurement result based on the acquired position (160); as well as An OCT imaging system (110) is operable to acquire the AS-OCT image (130), the OCT imaging system (110) comprising a fixation target (120), the fixation target (120) being arranged to fix a gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) such that an axis corresponding to a pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with a direction in the AS-OCT image (130) corresponding to an axial imaging direction (111) of the OCT imaging system (110).

2. The system (100) according to claim 1, wherein: The OCT imaging system (110) comprises a controller (115) arranged to control the OCT imaging system (110) to acquire the AS-OCT image (130), the controller (115) further arranged to control the fixation target (120) to fix a gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) by: obtaining an indication of laterality of the eye (140); Obtaining an indication of the orientation of a pupil axis (153) of the eye (140) relative to the visual axis of the eye (140) based on measurements of the relative orientation of the pupil axis and the visual axis in the eyes in the eye sample set and the obtained indication of the laterality of the eye (140); as well as The position of the fixation target (120) relative to the eye (140) is set using an indication of the orientation of the pupil axis (153) of the eye (140) relative to the visual axis of the eye (140), so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis in the AS-OCT image (130) is aligned with the direction in the AS-OCT image (130).

3. The system (100) of claim 1, wherein: The AS-OCT image (130) is a B-scan (200), the B-scan (200) comprising a representation of a portion of a scleral protrusion of the eye (140), and the OCT imaging system (110) comprises a controller (115) arranged to control the OCT imaging system (110) to acquire the AS-OCT image (130), the controller (115) further being arranged to control the fixation target (120) to fix a gaze direction (151) of the eye (140) during acquisition of the B-scan (200) by: An indication of the orientation of a pupil axis (153) of the eye (140) relative to a visual axis of the eye (140) is obtained by: Controlling the OCT imaging system (110) to acquire a calibration B-scan (800) of at least a portion of an anterior segment of the eye (140) by controlling the fixation target (120) to set a gaze direction (151) of the eye (140) such that a visual axis of the eye (140) is aligned with an axial imaging direction (111) of the OCT imaging system (110), wherein the calibration B-scan (800) is parallel to the B-scan; as well as determining an orientation of an axis (803) in the calibration B-scan (800) corresponding to a pupil axis (153) of the eye (140) relative to a direction (801) in the calibration B-scan (800) corresponding to an axial imaging direction (111) of the OCT imaging system (110) as an indication of an orientation of the pupil axis (153) of the eye (140) relative to a visual axis of the eye (140); as well as During acquisition of the AS-OCT image (130), the acquired indication of the orientation is used to set the position of the fixation target (120) relative to the eye (140) so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis (203) in the B-scan (200) is aligned with the direction (201) in the B-scan (200).

4. The system (100) according to claim 3, wherein: The controller (115) is arranged to determine the orientation of an axis (803) in the calibration B-scan (800) relative to a direction (801) in the calibration B-scan (800) by: identifying a representation of anatomical features (804, 805) of the eye (140) within the calibration B-scan (800) for use in determining an orientation of an axis (803) in the calibration B-scan (800) relative to a direction (801) in the calibration B-scan (800); as well as An orientation of an axis (803) in the calibration B-scan (800) relative to a direction (801) in the calibration B-scan (800) is determined based on a representation of the identified anatomical features (804, 805) of the eye (140).

5. The system (100) of claim 1, wherein: The OCT imaging system (110) comprises a controller (115) arranged to control the OCT imaging system (110) to acquire the AS-OCT image (130), the controller (115) further arranged to control the fixation target (120) to fix a gaze direction (151) of the eye (140) during acquisition of the B-scan (200) by: An indication of the orientation of the pupil axis of the eye (140) relative to the visual axis of the eye (140) is obtained by: Controlling the OCT imaging system (110) to acquire a first calibration B-scan (1100) of a first cross-section of at least a portion of an anterior segment of the eye (140) and a second calibration B-scan (1150) of a second cross-section of at least a portion of an anterior segment of the eye (140) by setting a gaze direction (151) of the eye (140) using the fixation target (120) such that a visual axis of the eye (140) is aligned with an axial imaging direction (111) of the OCT imaging system (110); wherein the plane of the first cross-section is perpendicular to the plane of the second cross-section; determining a first orientation of a first axis (1103) in the first calibration B-scan (1100) corresponding to a pupil axis (153) of the eye (140) relative to a first direction (1101) in the first calibration B-scan (1100) corresponding to an axial imaging direction (111) of the OCT imaging system (110); determining a second orientation of a second axis (1153) in the second calibration B-scan (1150) corresponding to a pupil axis (153) of the eye (140) relative to a second direction (1151) in the second calibration B-scan (1150) corresponding to an axial imaging direction (111) of the OCT imaging system (110); as well as determining an indication of an orientation of a pupil axis (153) of the eye (140) relative to a visual axis of the eye (140) based on the determined first orientation and the determined second orientation; as well as During acquisition of the AS-OCT image (130), the acquired indication of the orientation is used to set the position of the fixation target (120) relative to the eye (140) so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis corresponding to the pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with the direction in the AS-OCT image (130) corresponding to the axial imaging direction (111) of the OCT imaging system (110).

6. The system (100) according to claim 5, wherein: The controller (115) is arranged to determine the orientation of the first axis (1103) in the first calibration B-scan (1100) relative to the first direction (1101) in the first calibration B-scan (1100) by: identifying a representation of a first anatomical feature of the eye (140) within the first calibration B-scan (1100) for determining an orientation of the first axis (1103) in the first calibration B-scan (1100) corresponding to a pupil axis (153) of the eye (140) relative to the first direction (1101) in the first calibration B-scan (1100) corresponding to an axial imaging direction (111) of the OCT imaging system (110); and determining, based on the representation of a first anatomical feature of the eye (140) within the first calibration B-scan (1100), an orientation of the first axis (1103) corresponding to a pupil axis (153) of the eye (140) in the first calibration B-scan (1100) relative to the first direction (1101) corresponding to an axial imaging direction (111) of the OCT imaging system (110) in the first calibration B-scan (1100), and wherein the controller (115) is arranged to determine the orientation of the second axis (1153) in the second calibration B-scan (1150) relative to the second direction (1151) in the second calibration B-scan (1150) by: identifying a representation of a second anatomical feature of the eye (140) within the second calibration B-scan (1150) for determining an orientation of a second axis (1153) in the second calibration B-scan (1150) corresponding to a pupil axis (153) of the eye (140) relative to a second direction (1151) in the second calibration B-scan (1150) corresponding to an axial imaging direction (111) of the OCT imaging system (110); and Based on the representation of a second anatomical feature of the eye (140) in the second calibration B-scan (1150), an orientation of the second axis (1153) corresponding to the pupil axis (153) of the eye (140) in the second calibration B-scan (1150) relative to the second direction (1151) corresponding to the axial imaging direction (111) of the OCT imaging system (110) in the second calibration B-scan (1150) is determined.

7. The system (100) according to any preceding claim, wherein: The geometric measurement (160) is a measurement of the anterior chamber angle of the eye (140).

8. The system (100) according to any preceding claim, wherein: The OCT imaging system (110) further comprises a display device (300) arranged to display a graphic (310) as the fixation target, wherein the controller (115) is arranged to control a display position of the graphic (310) relative to the eye (140) so as to control a gaze direction (151) of the eye (140) when the eye (140) is fixating on the graphic (310).

9. Use of a fixation target (120) of an optical coherence tomography (OCT) imaging system for equalizing the image contrast of a portion of a scleral protrusion of an eye (140) in an anterior segment OCT (AS-OCT) image acquired by the OCT imaging system (110), wherein: The fixation target (120) is used to equalize the image contrast by fixing the gaze direction (151) of the eye (140) during the acquisition of the AS-OCT image (130) so that the axis corresponding to the pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with the direction corresponding to the axial imaging direction (111) of the OCT imaging system (110) in the AS-OCT image (130).

10. The use according to claim 9, wherein The fixation target (120) is used to equalize the image contrast by fixing the gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) so that an axis corresponding to the pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with a direction corresponding to the axial imaging direction (111) of the OCT imaging system (110) in the AS-OCT image (130) in the following manner: obtaining an indication of laterality of the eye (140); Obtaining an indication of the orientation of a pupil axis (153) of the eye (140) relative to the visual axis of the eye (140) based on measurements of the relative orientation of the pupil axis and the visual axis in the eyes in the eye sample set and the obtained indication of the laterality of the eye (140); as well as The position of the fixation target (120) relative to the eye (140) is set using an indication of the orientation of the pupil axis (153) of the eye (140) relative to the visual axis of the eye (140), so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis in the AS-OCT image (130) is aligned with the direction in the AS-OCT image (130).

11. The use according to claim 9, wherein The AS-OCT image (130) is a B-scan (200) comprising a representation of a portion of a scleral protrusion of the eye (140), and The fixation target (120) is used to equalize the image contrast by fixing the gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) so that an axis corresponding to the pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with a direction corresponding to the axial imaging direction (111) of the OCT imaging system (110) in the AS-OCT image (130) in the following manner: An indication of the orientation of a pupil axis (153) of the eye (140) relative to a visual axis of the eye (140) is obtained by: Acquiring a calibration B-scan (800) of at least a portion of an anterior segment of the eye (140) by setting a gaze direction (151) of the eye (140) using the fixation target (120) such that a visual axis of the eye (140) is aligned with an axial imaging direction (111) of the OCT imaging system (110), wherein the calibration B-scan (800) is parallel to the B-scan; as well as determining an orientation of an axis (803) in the calibration B-scan (800) corresponding to a pupil axis (153) of the eye (140) relative to a direction (801) in the calibration B-scan (800) corresponding to an axial imaging direction (111) of the OCT imaging system (110) as an indication of an orientation of the pupil axis (153) of the eye (140) relative to a visual axis of the eye (140); as well as During acquisition of the AS-OCT image (130), the acquired indication of the orientation is used to set the position of the fixation target (120) relative to the eye (140) so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis (203) in the B-scan (200) is aligned with the direction (201) in the B-scan (200).

12. The use according to claim 9, wherein The fixation target (120) is used to equalize the image contrast by fixing the gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) so that an axis corresponding to the pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with a direction corresponding to the axial imaging direction (111) of the OCT imaging system (110) in the AS-OCT image (130) in the following manner: An indication of the orientation of a pupil axis (153) of the eye (140) relative to a visual axis of the eye (140) is obtained by: Acquiring a first calibration B-scan (1100) of a first cross-section of at least a portion of an anterior segment of the eye (140) and a second calibration B-scan (1150) of a second cross-section of at least a portion of an anterior segment of the eye (140) by setting a gaze direction (151) of the eye (140) using the fixation target (120) such that a visual axis of the eye (140) is aligned with an axial imaging direction (111) of the OCT imaging system (110), wherein a plane of the first cross-section is perpendicular to a plane of the second cross-section; determining a first orientation of a first axis (1103) in the first calibration B-scan (1100) corresponding to a pupil axis (153) of the eye (140) relative to a first direction (1101) in the first calibration B-scan (1100) corresponding to an axial imaging direction (111) of the OCT imaging system (110); determining a second orientation of a second axis (1153) in the second calibration B-scan (1150) corresponding to a pupil axis (153) of the eye (140) relative to a second direction (1151) in the second calibration B-scan (1150) corresponding to an axial imaging direction (111) of the OCT imaging system (110); as well as determining an indication of an orientation of a pupil axis (153) of the eye (140) relative to a visual axis of the eye (140) based on the determined first orientation and the determined second orientation; as well as During acquisition of the AS-OCT image (130), the acquired indication of the orientation is used to set the position of the fixation target (120) relative to the eye (140) so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis corresponding to the pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with the direction in the AS-OCT image (130) corresponding to the axial imaging direction (111) of the OCT imaging system (110).

13. The use according to any one of claims 9 to 12, wherein The fixation target (120) includes a graphic (310) displayed by a display device (300), wherein the display position of the graphic (310) relative to the eye (140) is controllable so as to control the gaze direction (151) of the eye (140) when the eye (140) gazes at the graphic (310).

14. A method of processing an anterior segment optical coherence tomography (AS-OCT) image acquired by an OCT imaging system (110) to obtain geometric measurements (160) based on one or more anatomical features in the AS-OCT image (130), the AS-OCT image comprising a representation of a portion of a scleral protrusion of an eye (140), the method comprising: Acquiring (S51) the AS-OCT image (130), while fixing the gaze direction (151) of the eye (140) by causing the eye (140) to gaze at a fixation target (120), such that an axis corresponding to a pupil axis (153) of the eye (140) in the AS-OCT image (130) is aligned with a direction corresponding to an axial imaging direction (111) of the OCT imaging system (110) in the AS-OCT image 130; processing (S52) the acquired AS-OCT image (130) to obtain the corresponding position of the portion of the scleral protrusion of the eye (140) represented in the AS-OCT image (130) in the AS-OCT image (130); as well as The geometrical measurement result (160) is obtained (S53) based on the acquired position in the AS-OCT image (130).

15. The method according to claim 14, further comprising setting the fixation target (120) to fix the gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) by: obtaining (S61) an indication of the laterality of the eye (140); Obtaining (S62) an indication of the orientation of the pupil axis (153) of the eye (140) relative to the visual axis of the eye (140) based on the measurements of the relative orientation of the pupil axis and the visual axis in the eye in the eye sample set and the indication of the laterality of the eye (140) obtained; and The position of the fixation target (120) relative to the eye (140) is set using an indication of the orientation of the pupil axis (153) of the eye (140) relative to the visual axis of the eye (140) obtained by (S63), so that when the gaze direction (151) of the eye (140) is fixed by the fixation target (120) at the set position, the axis in the AS-OCT image (130) is aligned with the direction in the AS-OCT image (130).

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