System and method for improving scleral spur visibility in anterior segment oct images

Abstract

To provide a system and a method for improving scleral spur visibility in anterior segment OCT images.SOLUTION: There is provided a system arranged to process an anterior-segment optical coherence tomography (AS-OCT) image comprising representations of portions of a scleral spur of an eye to obtain a geometric measurement value of the eye. The system comprises data processing hardware arranged to: process the AS-OCT image to acquire respective locations in the AS-OCT image of the representations of the portions of the scleral spur of the eye in the AS-OCT image; and obtain the geometric measurement value based on the acquired locations. The system further comprises an OCT imaging system which is operable to acquire the AS-OCT image and comprises a fixation target to fix 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 pupillary 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.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Exemplary aspects of the present disclosure relate generally to the field of optical coherence tomography (OCT) imaging systems, and more particularly, to an OCT imaging system for obtaining an OCT image of at least a portion of the anterior chamber of an eye. [Background technology]

[0002] Optical coherence tomography (OCT) is an imaging technique based on low-coherence interferometry that is widely used to obtain high-resolution two- and three-dimensional images of light-scattering media such as biological tissue.

[0003] As is well known, OCT imaging systems can be classified as time-domain OCT (TD-OCT) or Fourier-domain OCT (FD-OCT) (also called frequency-domain OCT) depending on how the depth range is achieved. In TD-OCT, the optical path length of the reference arm of an interferometer in the imaging system is varied in time during acquisition of a reflectance profile of a scattering medium (herein referred to as an "imaged object") being imaged by the OCT imaging system, the reflectance profile being commonly referred to as a "depth scan" or "axial scan" ("A-scan"). In FD-OCT, the spectral interferogram resulting from the interference of light in the reference arm with light in the sample arm of the interferometer at each A-scan position is Fourier transformed to simultaneously acquire all points along the depth of the A-scan without requiring a change in the optical path length of the reference arm. FD-OCT can enable much faster imaging than scanning the sample arm mirror in an interferometer, since 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 imaged subject and measures all wavelengths simultaneously using a spectrometer as a detector. In SS-OCT (also called time-encoded frequency-domain OCT), a light source is swept across a range of wavelengths and the time output of the detector is converted to spectral interference.

[0004] OCT imaging systems can also be classified as point-scanning (also known as "point detection" or "scan point"), line-scanning, or full-field-scanning, depending on how the imaging system is configured to acquire OCT data at the location of the imaged object. Point-scanning OCT imaging systems acquire OCT data by scanning a focused sample beam across the surface of the imaged object, typically along a single line (which may be straight, for example, or curved to define a circle or spiral), or along a set of (usually substantially parallel) lines on the surface of the imaged object, one point at a time, acquiring an axial depth profile (A-scan) for each of multiple points along the line, to construct OCT data that includes a one- or two-dimensional array of A-scans that represent a two-dimensional (i.e., B-scan) or three-dimensional (i.e., C-scan or volume scan) reflectance profile of the sample.

[0005] Line-scan OCT imaging systems acquire OCT data by scanning a focused line of light across the surface of an imaged object. The measured reflectance from the imaged object is used to generate OCT data that includes a two-dimensional reflectance profile (i.e., B-scan) of the sample. By scanning a focused light beam across multiple locations of the imaged object, OCT data that includes a three-dimensional reflectance profile (i.e., C-scan or volume scan) of the sample can be obtained. Typically, the focused light beam is straight and scanned in a direction perpendicular thereto, but in some cases it may be curved with the scan direction adjusted accordingly. Full-field OCT imaging systems acquire OCT data by projecting a light beam onto the imaged object to acquire "in-plane" B-scans (orthogonal to the aforementioned B-scans), which can be stacked to create a three-dimensional reflectance profile (i.e., C-scan or volume scan) of the sample.

[0006] Anterior segment OCT (AS-OCT) imaging can be performed using one of the various types of OCT imaging systems summarized above to obtain a cross-sectional image (usually a B-scan or C-scan) of at least a portion of the anterior segment of the eye. AS-OCT imaging is performed for a variety of reasons related to eye health, such as glaucoma evaluation and cataract surgery (e.g., for biometry and pachymetry). An important aspect for glaucoma evaluation is determining the drainage capacity at the cornea / sclera / iris junction, which requires good visibility of this region. Although it is possible to perform a scan limited to this region (typically using a specialized lens adapter), for efficiency of data capture and storage, it is preferable to capture a complete anterior chamber OCT image (also broadly referred to as a "full chamber" or "complete anterior segment" OCT image), which encompasses the entire anterior chamber of the eye, as well as the surrounding portions of the anterior segment of the eye, typically including the cornea, sclera, iris, anterior portion of the lens, and the scleral promontory.

[0007] AS-OCT imaging can be performed not only for glaucoma evaluation, but also for various other purposes in which geometric measurements of the eye are made. Such geometric measurements can include, for example, measurements of distances within the eye, such as the anterior chamber width (ACW, also known as the promontory distance or angle distance), lens volt (LV), angle opening distance (AOD, e.g., AOD500) or anterior chamber depth (ACD), or measurements of angles within the eye, such as the anterior chamber angle (ACA), trabecular meshwork-iris angle (TIA) or iris-lens angle, and / or related areas, such as the trabecular meshwork-iris area (TISA, e.g., TISA500). Geometric measurements often rely on accurate identification of the location of one or more portions of the scleral promontory of the eye in the AS-OCT image (the scleral promontory is in the angle region of the anterior part of the eye where the iris meets the sclera), which can serve as a useful landmark or reference point. The better the visibility of the scleral promontory target, the more accurate measurements can be based thereon. However, in AS-OCT images, for example in the form of AS-OCT B-scans, portions of the scleral promontory that face each other in the AS-OCT B-scan (i.e., representations of the scleral promontory appearing on both sides of the anterior segment imaged in the B-scan) tend to have different visibility and contrast. As a result, it is often difficult to accurately locate at least one of the portions of the scleral promontory and thus obtain accurate geometric measurements from the image. It is therefore highly desirable to be able to more accurately locate the scleral promontory in AS-OCT images (e.g., full-cavity OCT images). Summary of the Invention

[0008] According to a first exemplary aspect of the present specification, a system is provided that is configured to process an anterior segment optical coherence tomography (AS-OCT) image including a representation of a portion of the scleral promontory of the eye to obtain geometric measurements of the eye. The system includes data processing hardware configured to process the AS-OCT image to obtain respective positions of the AS-OCT image of the representation of the portion of the scleral promontory of the eye in the AS-OCT image and obtain geometric measurements based on the obtained positions. The system further includes an OCT imaging system operable to obtain the AS-OCT image, the OCT imaging system including a fixation target arranged to fix the gaze direction of the eye during acquisition of the AS-OCT image such that an axis of the AS-OCT image corresponding to the pupil axis of the eye is aligned with a direction of the AS-OCT image corresponding to the axial imaging direction of the OCT imaging system. The fixation target may be positioned to fix the gaze direction of the eye during acquisition of the AS-OCT images 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, such that the axis of the AS-OCT image corresponding to the pupil axis of the eye (rather than the axis of the AS-OCT image corresponding to the visual axis of the eye) is aligned with the direction of the AS-OCT image corresponding to the axial imaging direction of the OCT imaging system. Thus, the fixation target may be positioned to fix the gaze direction of the eye during acquisition of the AS-OCT images 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.

[0009] According to a second exemplary aspect of the present specification, there is provided a use of a fixation target of an OCT imaging system for equalizing image contrast in a representation of a portion of the scleral promontory of an eye in an anterior segment OCT, AS-OCT image acquired by an OCT imaging system, the fixation target being used to equalize image contrast by fixing the gaze direction of the eye during acquisition of the AS-OCT image such that an axis of the AS-OCT image corresponding to the pupil axis of the eye is aligned with a direction of the AS-OCT image corresponding to an axial direction of the OCT imaging system. 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 such that an axis of the eye, rather than a visual axis of the eye, is aligned with an axial direction of the OCT imaging system, the axis of the AS-OCT image corresponding to a pupil axis of the eye (rather than an axis of the AS-OCT image corresponding to a visual axis of the eye) and thus aligned with a direction of the AS-OCT image corresponding to an axial direction of the OCT imaging system. Thus, the fixation target can fix the gaze direction of the eye during acquisition of AS-OCT images such that the pupillary 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.

[0010] According to a third exemplary aspect of the present disclosure, there is provided a method for processing anterior segment optical coherence tomography (AS-OCT) images acquired by an OCT imaging system, the images including a representation of a portion of a scleral promontory of an eye, to obtain geometric measurements based on one or more anatomical features of the AS-OCT images. The method includes acquiring the AS-OCT images while a gaze direction of the eye is fixed by the eye fixating on a fixation target such that an axis of the AS-OCT images corresponding to a pupil axis of the eye is aligned with a direction of the AS-OCT images corresponding to an axial imaging direction of the OCT imaging system, processing the acquired AS-OCT images to obtain respective positions of the AS-OCT images of the representation of the portion of the scleral promontory of the eye in the AS-OCT images, and obtaining geometric measurements based on the acquired positions of the AS-OCT images. The AS-OCT images can be acquired while the gaze direction of the eye is fixed by the eye fixating on a fixation target, such that the pupillary axis of the eye, rather than the visual axis of the eye, is aligned with the axial imaging direction of the OCT imaging system, such that the axis of the AS-OCT image corresponding to the pupillary axis of the eye (rather than the axis of the AS-OCT image corresponding to the visual axis of the eye) is aligned with the direction of the AS-OCT image corresponding to the axial direction of the OCT imaging system. Thus, the AS-OCT images can be acquired while the gaze direction of the eye is fixed by the eye fixating on a fixation target, such that the pupillary 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. Exemplary embodiments will now be described in detail, by way of non-limiting example only, with reference to the accompanying drawings, in which like reference numbers appearing in different drawings may indicate identical or functionally similar elements, unless otherwise indicated, and in which: [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of a system 100 according to a first exemplary embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram of a B-scan 200 acquired by the OCT imaging system 110 of the system 100 according to a first exemplary embodiment of the present disclosure. [Diagram 3]FIG. 3 is a schematic diagram of a front view of a display device 300 of system 100 displaying a graphic 310 as an example of a fixation target for fixing the gaze direction of the eye. [Figure 4] FIG. 4 is a schematic diagram of programmable signal processing hardware that may be configured to perform the functions of the data processing hardware 150 and / or controller 115 of the OCT imaging system 110 described herein. [Diagram 5] FIG. 5 is a flow diagram illustrating a process in which an AS-OCT image 130 acquired by the OCT imaging system 110 is processed by the data processing hardware 150 of the system 100 to obtain geometric measurements of the eye, according to a first exemplary embodiment of the present specification. [Figure 6] FIG. 6 is a flow chart showing a process in 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 an AS-OCT image 130 in the first exemplary embodiment of the present specification. [Figure 7] FIG. 7 is a flow chart illustrating an alternative process by which the controller 115 of the OCT imaging system 110 can obtain an indication of the orientation of the eye's pupillary axis 153 relative to the eye's visual axis, ({φ}N), in a first alternative implementation of the first exemplary embodiment of the present specification. [Figure 8] FIG. 8 is a schematic diagram of an exemplary calibration B-scan 800 acquired by the OCT imaging system 110 in a first alternative implementation of the first exemplary embodiment herein. [Figure 9] FIG. 9 is a flow chart of a process in which the controller 115 of the OCT imaging system 110 in a first alternative implementation of the first exemplary embodiment of the present specification can determine the orientation of the axis of the calibration B-scan corresponding to the pupil axis of the eye relative to the direction of the calibration B-scan corresponding to the axial imaging direction of the OCT imaging system 110. [Figure 10]FIG. 10 is a flow diagram illustrating a second alternative process by which the controller 115 of the OCT imaging system 110 can obtain an indication of the orientation of the eye's pupil axis relative to the eye's visual axis, ({φ}N), in a second alternative implementation of the first exemplary embodiment of the present specification. [Figure 11A] FIG. 11A is a schematic diagram of an exemplary first calibration B-scan 1100 according to a second alternative implementation of the first exemplary embodiment of the present specification. [Figure 11B] FIG. 11B is a schematic diagram of an exemplary calibration second B-scan 1140 according to a second alternative implementation of the first exemplary embodiment of the present specification. [Figure 12A] FIG. 12A shows an uncorrected B-scan 1200. [Figure 12B] FIG. 12B illustrates a B-scan 1250 that has been corrected in accordance with a first exemplary embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The inventors have recognized that due to misalignment of the visual and pupillary axes of the eye, conventional OCT imaging systems for AS-OCT imaging (e.g., for full-chamber imaging) tend to acquire AS-OCT B-scans in which anatomical features such as the iris appear at a slight tilt relative to the lateral direction of the B-scan, i.e., perpendicular to the axial direction of the B-scan (the axial direction being the direction of the B-scan along which each of the constituent A-scan elements of the B-scan are aligned). This tilt is generally considered a nuisance and is typically compensated for in post-processing to provide the clinician with a symmetrical B-scan.

[0013] Upon more detailed examination of the AS-OCT B-scans, the inventors found that the degree of tilt observed in the acquired B-scan correlates with the visibility and contrast of the representation of opposing portions of the scleral promontory in the B-scan (i.e., different cross-sectional views of the scleral promontory appearing on either side of the B-scan, e.g., as shown at 1201 and 1202 in FIG. 12A). More specifically, the inventors noticed that the difference between the visibility (or contrast) of each of the representations of two opposing portions of the scleral promontory in the B-scan tended to increase as the degree of tilt of the anterior ocular anatomical features relative to the frame of the B-scan increased.

[0014] The inventors further recognized that the overall visibility or contrast of the representation of the scleral promontory portion of the AS-OCT B-scan, and therefore the accuracy of the measurements made using these landmarks, may be improved by eliminating or at least reducing the tilt of the B-scan at its source, in particular by modifying the acquisition of the B-scan so that the pupillary axis (rather than the visual axis) of the eye is aligned with the axial imaging direction of the OCT imaging system. More specifically, the OCT imaging system may be modified to include a fixation target positioned to fix the gaze direction of the eye during the acquisition of the B-scan, such that the axis of the B-scan corresponding to the pupillary axis of the eye is aligned with the direction of the B-scan corresponding to the axial imaging direction of the OCT imaging system. This not only eliminates or reduces the degree of tilt of the B-scan, but also tends to equalize the visibility or contrast of the representation of the scleral promontory of the B-scan, allowing for more accurate geometric measurements of the anterior segment of the eye. It will be appreciated that although the foregoing discussion is framed in the context of B-scans, the principles described are generally also applicable to anterior segment OCT (AS-OCT) images in the form of C-scans.

[0015] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

[0016] FIG. 1 is a schematic diagram of a system 100 according to a first exemplary embodiment herein configured to process AS-OCT images to obtain geometric measurements of the eye.

[0017] The system 100 includes an OCT imaging system 110 controlled by its controller 115 and including a fixation target 120. The OCT imaging system 110 is configured to acquire an AS-OCT image 130 of the eye 140 including a representation of (opposing) portions of the scleral promontory of the eye 140 (e.g., portions of the scleral promontory on either side of the anterior chamber of the eye 140). The AS-OCT image 130 of the eye 140 may be a full-cavity AS-OCT image encompassing the entire anterior chamber of the eye 140 and a peripheral portion of the anterior portion of the eye 140 including the (opposing) portions of the scleral promontory of the eye 140. During acquisition of the AS-OCT image 130, the fixation target 120 is positioned to fix the gaze direction 151 of the eye 140 such that an axis of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with a direction of the AS-OCT image corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0018] The system 100 further includes data processing hardware 150 configured to process the AS-OCT image 130 to obtain geometric measurements 160 of the eye 140. The geometric measurements 160 of the eye 140 are obtained by the data processing hardware 150 based on the position of the representation of the (opposing) portion of the scleral promontory of the eye 140 in the AS-OCT image 130 and, depending on the selected geometric measurements 160, on the representation of one or more other anatomical features of the eye 140 in the AS-OCT image 130, as will be described in more detail below. The data processing hardware 150 may be provided as a separate component from the OCT imaging system 110, as in this exemplary embodiment, but the data processing hardware 150 may alternatively form part of the OCT imaging system 110, for example whose functions are performed by the controller 115.

[0019] The OCT imaging system 110 may be, as in this exemplary embodiment, a point-scanning Fourier domain OCT imaging system. However, the form of the OCT imaging system 110 is not so limited and may alternatively take the form of a time domain system, or may further alternatively be a line-scan or full-field OCT imaging system. Furthermore, the OCT imaging system 110 may be operable to obtain both AS-OCT and posterior segment OCT (PS-OCT) images of the eye 140.

[0020] 2 is a schematic illustration of an AS-OCT image 130 in the exemplary form of a full-cavity B-scan 200 representing a cross-section of the entire anterior chamber of the eye 140 and a peripheral portion of the anterior segment of the eye 140 (including an opposing portion of the scleral promontory 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 pupillary axis 153 of the eye 140, and a second axis 202 corresponding to the visual axis of the eye 140 that defines the gaze direction 151 of the eye 140. However, the AS-OCT image 130 may more typically be a B-scan that does not encompass the entire anterior chamber of the eye 140, but still includes a representation of the (opposing) portion of the scleral promontory of the eye 140 (e.g., a B-scan covering a portion of the anterior chamber of the eye 140 along the axial direction including a portion of the scleral promontory of the eye 140). Alternatively, the AS-OCT image 130 may be a C-scan including a representation of the (opposite) portion of the scleral promontory of the eye 140, which may include the entire anterior chamber of the eye 140 and the surrounding portions of the anterior segment of the eye 140, as described below.

[0021] The fixation target 120 is positioned to fixate the gaze direction 151 of the eye 140 (i.e., along the visual axis of the eye 140, away from the eye 140) during acquisition of the AS-OCT image 130 such that an axis 203 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction 201 of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110. That is, the fixation target 120 is positioned such that when the eye 140 fixates to fixate the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image (130), the axis 203 of the AS-OCT image 130, which represents the pupil axis 153 of the eye 140, is parallel to the direction 201 of the AS-OCT image 130, which represents the axial imaging direction 111 of the OCT imaging system 110. The axis 203 may more generally be aligned with the direction 201 to within a predetermined tolerance (e.g., 0.01, 0.1 or 1 degree). This is shown in Figure 2, where the placement of the fixation target 120 fixes the gaze direction 151 of the eye 140 during acquisition of the B-scan 200 such that the axis 203 of the B-scan 200, which corresponds to the pupillary axis 153 of the eye 140, is parallel to the direction 201 in the B-scan 200, which corresponds to the axial imaging direction 111 of the OCT imaging system 110.

[0022] The position of the fixation target 120 relative to the eye 140 may be controllable by the OCT imaging system 110 (specifically, by its controller 115) to control the gaze direction 151 of the eye 140 when the eye 140 fixates on the fixation target 120, as in this exemplary embodiment. A process in which the OCT imaging system 110 sets the fixation target 120 to fixate the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 such that an axis 203 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction 201 of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110 will be described in more detail below. However, the position of the fixation target 120 may alternatively be set relative to the expected position of the eye 140 during manufacture (i.e., the position set by the position of a chin rest, etc., where the eye 140 is positioned relative to the OCT imaging system 110 and the OCT imaging system 110 acquires the AS-OCT image 130) so that during acquisition of the AS-OCT image 130, the axis 203 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction 201 of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0023] The fixation target 120 can be integrated into the sample arm of the OCT imaging system 110 by using a beam splitter / combiner to couple light from the fixation target 120 into the optical path of the sample arm, as in this exemplary embodiment. If the OCT imaging system 110 is a line-scan or point-scan OCT imaging system, the beam splitter / combiner can be placed between the scanning mirrors and the eye 140 or in front of at least one of the scanning mirrors in the optical path toward the eye 140. If the fixation target 120 is placed in front of at least one of the scanning mirrors in the optical path toward the eye 140, the light from the fixation target 120 can be pulsed to coincide with a predetermined position of at least one of the scanning mirrors to ensure that the position of the fixation target 120 from the perspective of the eye 140 remains fixed as at least one of the scanning mirrors moves.

[0024] 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 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 axis 203 based on a ray tracing model of the optical system of the eye and the OCT imaging system 110 between the fixation target 120 and the eye 140. Alternatively, the position of the fixation target 120 relative to the eye 140 required to achieve the alignment between the above-mentioned direction 201 and axis 203 can be estimated based on triangulation using the optical path length L from a point of the eye 140 (e.g., the center of the pupil or the geometric center of the eyeball) to the fixation target 120.

[0025] 3 is a schematic diagram of an exemplary implementation of the OCT imaging system 110, where the 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 is controllable by the controller 115 to control the gaze direction 151 of the eye 140 when the eye 140 fixates 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 the 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 indicated by the arrows in FIG. 3, to move (direct) the gaze direction 151 of the eye 140 when the eye 140 fixates on the graphic 310. In FIG. 3, the graphic 310 takes the form of a dot, but it will be understood that the form of the graphic is not so limited and may instead be provided as a cross, a circle, or any shape to which the eye 140 can fixate. The fixation target 120 may also be realized in forms 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 controllable by the controller 115 to move the light source relative to the eye 140 so as to control the gaze direction 151 of the eye 140 when the eye 140 fixates the light source.

[0026] The data processing hardware 150 is configured to process the AS-OCT images 130 to obtain respective positions in the AS-OCT images 130 of the representation of the (opposing) portion of the scleral promontory of the eye 140 in the AS-OCT images 130, as will be described in more detail below with reference to process S52 of Figure 5. The data processing hardware 150 is further configured to obtain (or determine) geometric measurements 160 based on the obtained positions, as will be described below with reference to process S53 of Figure 5.

[0027] The data processing hardware 150 and controller 115 of the OCT imaging system 110 may be provided in any suitable form, for example as programmable signal processing hardware 400 of the type shown generally in FIG.

[0028] The programmable signal processing device 400 includes a communication interface (I / F) 410 for communicating data with the outside world. If the device 400 implements the data processing hardware 150, the I / F 410 can be configured to receive the AS-OCT image 130 from the OCT imaging system 110 and output the geometric measurements 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. If the device 400 implements the controller 115 of the OCT imaging system 110, the I / F 410 can be configured to receive instructions for acquiring the AS-OCT image 130 (e.g., target positions and commands for starting an acquisition procedure) and output the AS-OCT image 130.

[0029] The signal processing hardware 400 further includes a processor (e.g., a central processing unit, CPU, and / or a graphics processing unit, GPU) 420, a working memory 430 (e.g., random access memory), and an instruction store 440 that stores a computer program 445 that includes computer readable instructions that, when executed by the processor 420, cause the processor 420 to perform various functions, including the functions of the data processing hardware 150 and / or 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 store 440 may include a ROM (e.g., in the form of an Electrically Erasable Programmable Read Only Memory (EEPROM) or flash memory) that is preloaded with computer readable instructions. Alternatively, the instruction store 440 may include a RAM or similar type of memory, and the computer readable instructions of the computer program 445 may be input from a computer program product, such as a non-transitory computer readable storage medium 450 in the form of a CD-ROM, DVD-ROM, etc., or a computer readable signal 460 carrying the computer readable instructions. In either 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 described herein. In other words, the data processing hardware 150 of the first exemplary embodiment may include a computer processor 420 and a memory 440 that stores computer readable instructions, when executed by the computer processor 420, that cause the computer processor 420 to process the AS-OCT images 130 to obtain respective positions in the AS-OCT images 130 of the representation of the (opposing) portion of the scleral promontory of the eye 140 in the AS-OCT images 130, and to obtain geometric measurements 160 based on the obtained positions.Similarly, the controller 115 of the OCT imaging system 110 of the first exemplary 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 exemplary embodiment (including the process of S51 in FIG. 5 and the processes of FIGS. 6, 7, 9, and 10).

[0030] 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 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 with non-programmable hardware, such as dedicated ASICs, FPGAs, or other integrated circuits 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 a combination of such non-programmable hardware and programmable hardware as described above with reference to FIG.

[0031] FIG. 5 is a flow diagram illustrating how an AS-OCT image 130 acquired by an OCT imaging system 110 may be processed by data processing hardware 150 to obtain geometric measurements 160 of an eye 140, as in this exemplary embodiment.

[0032] 5, the OCT imaging system 110 acquires the AS-OCT image 130 while the gaze direction 151 of the eye 140 is fixed by the eye 140 fixating the fixation target 120 such that the axis 203 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction 201 of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110. The process of the controller 115 of the OCT imaging system 110 setting the fixation target 120 in this manner to fix the gaze direction 151 of the eye 140 will be described in more detail below. However, as mentioned above, the fixation target 120 may alternatively be set to fix the direction 151 of the eye 140 in the manner described above during manufacture of the OCT imaging system 110.

[0033] 5, the data processing hardware 150 processes the acquired AS-OCT images 130 to obtain the respective positions of the representations of the (opposite) portions of the scleral promontory of the eye 140 in the AS-OCT images 130. This can be accomplished using any of the techniques known to those skilled in the art. For example, the data processing hardware 150 can use a deep learning method that utilizes a trainable multi-layer neural network to identify the positions of the (opposite) portions of the scleral promontory of the eye 140 in the B-scan 200. As another example, the data processing hardware 150 can process the acquired AS-OCT images 130 by displaying them to a user on a display screen and acquiring respective positions of the AS-OCT images 130 of the representation of the (opposing) portion of the scleral promontory of the eye 140 in the AS-OCT images 130 by receiving designations of these positions input by the user after inspecting the displayed AS-OCT images 130 (e.g., using a mouse and / or keyboard, or via one or more touch interactions, if the display screen is a touch screen). Further details of exemplary techniques known to those skilled in the art are published in Benjamin Y. Xu et al., “Deep Neural Network for Scleral Spur Detection in Anterior Segment OCT Images: The Chinese American Eye Study”, Transl Vis Sci Technol., 30 March 2020, which is incorporated herein by reference in its entirety.

[0034] In process S53 of FIG. 5, the data processing hardware 150 acquires (or determines) geometric measurements 160 based on the acquired positions. This can be accomplished using techniques 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 acquired positions of the representation of the portion of the scleral promontory in the B-scan 200. As a further 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 promontory in the B-scan 200 and the boundary of the anterior chamber (e.g., the anterior iris surface and the posterior cornea surface) in the B-scan 200. The boundary of the anterior chamber in the B-scan 200 can be determined by the data processing hardware 150 using an anterior chamber segmentation technique known to those skilled in the art, such as anterior chamber segmentation using deep learning methods. Further details regarding the determination of anterior chamber angle parameters can be found in Guangqian Yang et al., “Automatic measurement of anterior chamber angle parameters in AS-OCT images using deep learning,” Biomed.Opt.Express 14, 1378-1392 (2023), the entire contents of which are incorporated by reference into this specification.

[0035] FIG. 6 is a flow chart showing a process by which, as in this exemplary embodiment, the controller 115 of the OCT imaging system 110 can set the fixation target 120 to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 in step S51 of FIG. 5.

[0036] In optional process S61 of Figure 6, the controller 115 obtains the laterality of the eye 140 (i.e., whether the eye 140 is the right or left eye of the subject). The controller 115 may obtain the laterality of the eye 140 by, for example, receiving input from a clinician operating the OCT imaging system 110. However, the laterality of the eye 140 may alternatively be determined automatically by the controller 115 using techniques known to those skilled in the art. As noted above, process S61 is optional and may not be performed, as described below in connection with alternative implementations of the first exemplary embodiment.

[0037] 6, the controller 115 obtains an indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 (e.g., as defined by an angle, e.g., as in a polar coordinate system, or as defined by two angles, e.g., as in a spherical coordinate system) based on the relative orientations of the pupillary axis and visual axis of the sample set of eyes and the obtained laterality measurements of the eye 140. The controller 115 can obtain the indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye from data from a memory of the OCT imaging system 110 (e.g., memory 440 of FIG. 4). However, the orientation index I may alternatively be obtained in other ways, for example by downloading the index I from a remote server or by retrieving from a remote server measurements of the relative orientation of the pupillary and visual axes of the eyes of a sample set of eyes corresponding to the obtained laterality of the eye 140 and calculating a representative value (e.g., average or median) of the retrieved measurements as the orientation index I.

[0038] The measurements of the relative orientation of the pupillary axis and visual axis of the eyes of the sample eye pair (i.e., as sampled from a population) may, in this exemplary embodiment, be obtained by providing respective first values ​​(φNT ,φ SI ) R and further including respective second values ​​(φ NT ,φ SI ) L Thus, the memory accessed by the controller 115 may include a representative value (e.g., an average or median) of the first value (φ NT ,φ SI ) R and the representative value of the second value (φ NT ,φ SI ) L from which the controller 115 can store the orientation index (φ NT ,φ SI ) K However, the memory of the OCT imaging system 110 may alternatively store the first value (φ NT ,φ SI ) R and the second value (φ NT ,φ SI ) L , and the controller 115 retrieves a set of values ​​corresponding to the measure of laterality of the eye 140 and uses them to determine a representative value (φ NT ,φ SI ) K may be calculated.

[0039] Additionally, the measurement of the relative orientation of the pupillary and visual axes of the eyes of the eye sample set can take other forms. For example, under the assumption of symmetry between the right and left eyes of the eye sample set, the measurement of the relative orientation can be a value indicative of a first component of the kappa angle in the nasal-temporal direction and a second component of the kappa angle in the superior-inferior direction (φ NT ,φ SI ) EThus, the obtained measure of laterality of eye 140 can be used to resolve relative orientation measurements in the reference coordinate system of OCT imaging system 110 to obtain an orientation measure I when the nasal-temporal direction is flipped between the left and right eyes (i.e., the directions defining the positive angles of the right and left eyes are flipped with respect to a common reference frame).

[0040] Additionally, the orientation index I may approximate the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis of the eye 140 in one direction. In such a case, the measurement of relative orientation may be a value indicative of the kappa angle (φ NT ) or value(φ SI Although the relative orientation is described above as being relative to the nasal-temporal direction and the superior-inferior direction, any two orthogonal directions in the plane defined by the nasal-temporal direction and the superior-inferior direction (or any first and second directions having at least a component orthogonal to the first direction) may be used as a frame of reference.

[0041] 7 is a flow diagram illustrating an alternative process to process S62 of FIG. 6 in which the controller 115 of the OCT imaging system 110 can obtain an indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 in a first alternative implementation of the present exemplary embodiment. The inventors have recognized that the visual axis 152 of the eye 140 may be difficult to identify in an AS-OCT image of the eye 140 based on the anatomical features of the eye 140 in some cases, but by manipulating the gaze direction 151 of the eye 140 using the fixation target 120, it can be positioned to be parallel to the axial imaging direction 111 of the OCT imaging system 110, and thus the orientation of the pupillary axis 153 of the eye 140 (which can be more easily identified based on at least the anatomical features of the eye 130 in the AS-OCT image) can be determined relative to the assumed location of the visual axis of the eye 130. When the alternative process described below is used, process S61 of FIG. 6 may be omitted.

[0042] 7, the controller 115 controls the OCT imaging system 110 (e.g., by a calibration B-scan having an axis corresponding to the pupillary axis 153 of the eye 140) to acquire a calibration B-scan of at least a portion of the anterior segment of the eye 140 to determine an orientation of the axis of the calibration B-scan corresponding to the pupillary axis 153 of the eye 140 with respect to an orientation of the calibration B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110. The controller 115 controls the OCT imaging system 110 to acquire a calibration B-scan parallel to the B-scan 200 by setting the gaze direction 151 of the eye 140 using the fixation target 120 such 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 acquisition of the calibration B-scan, the controller 115 sets the position of the fixation target 110 relative to the eye such that when the gaze direction 151 of the eye 140 is fixed 140 by the fixation target 120 at a set position, the gaze direction 151 of the eye 140 (which is along the visual axis of the eye 140) 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 a peripheral portion of the anterior part of the eye 140, including at least a portion of the scleral promontory of the eye 140. It should be noted that the calibration B-scan is acquired prior to the B-scan 200 and is therefore parallel to the expected or predetermined plane of the B-scan 200.

[0043] 8 is a schematic diagram of an exemplary calibration B-scan 800 acquired in the manner described above by OCT imaging system 110. As shown, an axis 802 of the calibration B-scan 800, which corresponds to the visual axis of the eye 140, is parallel to a direction 801 of the calibration B-scan 800, which corresponds to the axial imaging direction 111 of the OCT imaging system 110, but may more generally be aligned with direction 801 within a predetermined tolerance (e.g., 0.01, 0.1, or 1 degree) from direction 801.

[0044] In process S72 of Fig. 7, the controller 115 determines the orientation of the axis of the calibration B-scan 800 corresponding to the pupillary axis 153 of the eye 140 relative to the direction of the calibration B-scan 800 corresponding to the axial imaging direction 111 of the OCT imaging system 110 as an indication I of the orientation of the pupillary 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 pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 in the calibration B-scan 800 corresponds to the orientation of the pupillary 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 can therefore be used as an acquired indication of orientation for the purposes of correction applied in process S63 of Fig. 6, which will be described in detail below.

[0045] FIG. 9 is a flow chart showing a process in which, as in a first alternative embodiment of this exemplary embodiment, the controller 115 of the OCT imaging system 110 can determine the orientation of the axis of the calibration B-scan 800 corresponding to the pupil axis 153 of the eye 140 relative to the direction of the calibration B-scan 800 corresponding to the axial imaging direction 111 of the OCT imaging system 110, as in process S72 of FIG. 7.

[0046] In process S91 of Fig. 9, the controller 115 identifies (or locates) representations of anatomical features of the eye 140 in the calibration B-scan 800 in order to determine the orientation of the axis of the calibration B-scan 800 corresponding to the pupillary axis 153 of the eye 140 with respect to the orientation of the calibration B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110. For example, in the calibration B-scan 800 of Fig. 8, a representation of opposing portions 804, 805 of the scleral promontory of the eye 140 is identified (as a line 806 connecting the opposing portions 804, 805 of the scleral promontory, which is expected to be parallel to the pupillary plane of the eye 140, can be used to approximate the orientation of the pupillary axis 153 of the eye 140 in the calibration B-scan 800 relative to the frame of the calibration B-scan 800). However, other anatomical features suitable for this purpose may be identified, such as the pupil being identified in the calibration B-scan 800 in order to directly obtain the pupillary plane. Such representations of scleral spurs or other anatomical features may be identified using any of the techniques known to those skilled in the art. For example, the controller 115 may use deep learning methods that utilize trainable multi-layer neural networks to identify the representations of anatomical features in the calibration B-scan 800. As another example, the controller 115 may obtain the identifications of the representations of anatomical features in the calibration B-scan 800 by processing the calibration B-scan 800 by displaying it to a user on a display screen and receiving designations of their positions entered by the user after inspecting the displayed calibration B-scan 800 (e.g., using a mouse and / or keyboard if the display screen is a touch screen, or via one or more touch interactions).

[0047] In process S92 of Figure 9, the controller 115 determines an orientation of the aforementioned axis of the calibration B-scan relative to the aforementioned direction of the calibration B-scan based on the identified representation of the anatomical features of the eye 140. Continuing with the example of the calibration B-scan 800 of Figure 8, the direction orthogonal to the line 806 of the plane of the calibration B-scan 800 indicates the orientation of the axis 803 of the calibration B-scan 800. This orthogonal direction can therefore be used to determine the orientation of the axis 803 of the calibration B-scan 800 relative to the direction 801 of the calibration B-scan 800.

[0048] 10 is a flow diagram illustrating a second alternative process in which the controller 115 of the OCT imaging system 110 can 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, as in a second alternative embodiment of the present exemplary embodiment. The second alternative process is similar to the first alternative process, but obtains a three-dimensional arrangement of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140, and is therefore 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 of a C-scan (as the AS-OCT image 130). When the second alternative process described below is used, process S61 of FIG. 6 may be omitted.

[0049] In process S101 of FIG. 10, 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 the anterior segment of the eye 140 to determine a first orientation of a first axis of the first calibration B-scan corresponding to the pupil axis 153 of the eye 140 relative to a first direction of the first calibration B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110 (e.g., by a first calibration B-scan having a first axis corresponding to the pupil axis 153 of the eye 140). In process S101 of FIG. 10, the controller 115 further 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 to determine a second orientation of the second axis of the second calibration B-scan corresponding to the pupil axis 153 of the eye 140 relative to a second direction of the second calibration B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110 (e.g., by a second calibration B-scan having a second axis corresponding to the pupil axis 153 of the eye 140), where the plane of the first cross section is perpendicular to the plane of the second cross section. The controller 115 does this by controlling the fixation target 120 to set the gaze direction 151 of the eye 140 such 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 acquisition of the first and second calibration B-scans, the controller 115 sets the position of the fixation target 110 relative to the eye 140 such that when the gaze direction of the eye 140 is fixed at the position set by the fixation target 120, the gaze direction 151 of the eye 140 (along which the visual axis of the eye 140 is) is aligned with the axial imaging direction 111 of the OCT imaging system 110. The first and second cross sections may be of the entire anterior chamber of the eye 140 and a peripheral portion of the anterior segment of the eye 140, respectively, and each may include at least a portion of the scleral promontory of the eye 140.

[0050] 11A and 11B are schematic diagrams, respectively, of an exemplary first calibration B-scan 1100 and an exemplary second calibration B-scan 1150. As shown, the respective axes 1102, 1152 of the calibration B-scans 1100, 1150, which correspond to the visual axis of the eye 140, are parallel to the respective directions 1101, 1151 of the calibration B-scans 1100, 1150, which correspond to the axial imaging direction 111 of the OCT imaging system 110, but may more generally be aligned with the respective directions 1101, 1151 within a predetermined tolerance (e.g., 0.01, 0.1 or 1 degree) from the respective directions 1101, 1151.

[0051] In process S102 of Figure 10, the controller 115 determines a first orientation of a first axis of the first calibration B-scan corresponding to the pupil axis 153 of the eye 140 relative to a first direction of the first calibration B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110. For example, in Figure 11A, the OCT imaging system 110 determines the first orientation as an 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 can determine the first orientation via the process of Figure 9, as described in detail above.

[0052] In process S103 of Figure 10, the controller 115 determines a second orientation of a second axis of the second calibration B-scan corresponding to the pupil axis 153 of the eye 140 relative to a second direction of the second calibration B-scan corresponding to the axial imaging direction 111 of the OCT imaging system 110. For example, referring to Figure 11B, the controller 115 determines the second orientation as an 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 1050 corresponding to the axial imaging direction 111 of the OCT imaging system 110. The controller 115 can determine the second orientation via the process of Figure 9 as described above.

[0053] 10, the controller 115 determines an index I of an orientation of the pupillary 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). When the first cross section is perpendicular to the second cross section, the determined first orientation and the determined second orientation define an orientation of the pupillary 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 can use the determined first orientation and the determined second orientation as an indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140, or can decompose the determined first orientation and the determined second orientation, for example, as an indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 into a first component in a nasal-downward direction (using an acquired indication of the lateral difference of the eye 140, or if no indication is acquired, resolving the first component with respect to a direction along a horizontal axis that falls along the nasal-downward direction) and a second component in an up-down direction. Alternatively, if the AS-OCT image 130 is a B-scan 200, the OCT imaging system 110 can determine an index 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 decomposing the determined first orientation and the determined second orientation into a cross-sectional plane of the B-scan 200 and using this as the determined index I.

[0054] The first and second alternative processes described above allow for the performance of a patient-specific alignment of the pupil axis 153 of the eye 140 to the axial imaging direction 111 of the OCT imaging system 110, which may further improve the accuracy and reliability of the acquired geometric measurements of the eye 140 due to the further reduction in image contrast differences of opposing parts of the scleral promontory of the eye in the AS-OCT images 130. However, the process of the first exemplary embodiment utilizing relative orientation measurements from a sample set of eyes allows for a faster alignment to be achieved without the need to acquire one or more calibration AS-OCT images, and thus may reduce the acquisition time of the geometric measurements of the eye 140 compared to the alternative embodiment. This process may therefore be preferred for clinical applications where processing efficiency / throughput is important and the achievable improvement in the accuracy of the acquired geometric measurements of the eye 140 may be sufficient not to warrant the use of the alternative embodiment described above.

[0055] 6, in step S63, the controller 115 uses the acquired indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 to set the fixation target 120 to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130, so that the axis 203 of the AS-OCT image 130 is aligned with the direction 201 of the AS-OCT image 130. The OCT imaging system 110 can achieve this, as in the present exemplary embodiment, by setting the position of the fixation target 120 using the acquired indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 such 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, 0.1, or 1 degree). 2 may be acquired by OCT imaging system 110 at any cross-section of eye 140 and have an axis 203 parallel to direction 201. Similarly, as discussed above, when AS-OCT image 130 is provided in the form of an OCT C-scan, alignment in three-dimensional space of gaze direction 151 of eye 140 with axial imaging direction 111 may result in the axis of the C-scan corresponding to the pupil axis of eye 140 being aligned with the direction of the C-scan corresponding to axial imaging direction 111.

[0056] However, the controller 115 can alternatively 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 such that the projection of the gaze direction 151 of the eye 140 onto the plane is aligned with the projection of the axial imaging direction 111 of the OCT imaging system 110 onto the plane in which the B-scan 200 is acquired. For example, the acquired indication I of orientation in process S52 (or its alternative embodiment) can provide information for setting the position of the fixation target 120 such that the axis 203 of the B-scan 200 is aligned with the direction 201 of the B-scan 200 because the controller 115 has already resolved the acquired indication in process S62 or S104 into the (expected or predetermined) plane of the B-scan 200 or has acquired indications from a calibration B-scan parallel to the B-scan 200 in process S72. The controller 115 can alternatively perform such a resolution of the acquired indications at this stage. For example, if the acquired indication is of an orientation having two directional components, the controller 115 may at this stage use information about the position of the plane of the B-scan 200 relative to the nasal-temporal and superior-inferior directions to resolve the acquired indication I of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 into the plane of the B-scan 200, for example, to determine the orientation φ of the pupillary axis 153 of the eye 140 relative to the visual axis 152 of the eye 140 as it appears in the B-scan 200. b Therefore, the controller 115 adjusts the orientation φ so that the axis 203 of the B-scan 200 is parallel to the direction 201 of the B-scan 200. b The position of the fixation target 120 can be set using

[0057] Alternatively, if the acquired index I in process S62 is oriented in one direction (e.g., nasal-temporal or superior-inferior), the controller 115 can set the position of the fixation target 120 so that when the B-scan 200 or future B-scans are acquired in a plane whose acquired orientation is defined in one direction, the axis of the B-scan corresponding to the pupil axis of the eye 140 is aligned with the direction of the B-scan corresponding to the axial imaging direction 110 of the OCT imaging system 110.

[0058] In the above, it has been described that the fixation target 120 is positioned to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that the axis 203 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction 201 of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110. However, the fixation target 120 may also be positioned to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130 so that the axis of the AS-OCT image 130 corresponding to the optical axis of the eye 140 is aligned with the direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110. In such a case, in process S62 of Fig. 6, the measurements are instead related to the relative orientation of the optical and visual axes of the eye of the sample set of eyes (i.e., the alpha angle of the eye in the sample set of eyes instead of the kappa angle), and in the alternative processes of Fig. 7 and Fig. 10, the orientation of each of the calibration B-scans is that of the respective axis of each of the calibration B-scans corresponding to the optical axis of the eye 140 relative to the respective direction of each of the B-scans corresponding to the axial imaging direction 111 of the OCT imaging system 110. More generally, the fixation target 120 can be positioned to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130, such that the position of the representation of the opposing portions of the scleral promontory of the eye 140 in the AS-OCT image 130 in the direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110 (i.e., the axial direction in the AS-OCT image 130 in which the data elements of the component A-scans are arranged) is horizontal to that direction. For example, if the AS-OCT image 130 is a B-scan, then representations of opposing portions of the scleral promontory appear at the same height in the B-scan, i.e., the axial positions in the AS-OCT image 130 of the representations of opposing portions of the scleral promontory of the eye 140 in the AS-OCT image 130 are equal (within a predetermined tolerance) along that direction.In other words, the fixation target 120 may be positioned to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image so that the representations of opposing portions of the scleral promontory of the eye 140 in the AS-OCT image 130 have respective axial depths (i.e., respective positions along the axial direction in the AS-OCT image 130) that are substantially the same.

[0059] In the first exemplary embodiment described above and its variations, the above-described control of the fixation target 120 can make the image contrast of the representations of opposing portions of the scleral promontory of the eye 140 in the AS-OCT image 130 acquired by the OCT imaging system 110 the same or nearly the same. Thus, the required degree of alignment between the axis 203 of the AS-OCT image 130, which corresponds to the pupil axis 153 of the eye 140, and the direction 201 of the AS-OCT image 130, which corresponds to the axial imaging direction 111 of the OCT imaging system 110, can be such that an acceptable degree of equalization of the scleral promontory contrast can be achieved.

[0060] For example, Fig. 12A shows a B-scan 1200 acquired by a conventional OCT imaging system, where tilt correction is usually applied only in post-processing. As can be seen in Fig. 12A, the difference in image contrast between the representations 1201 and 1202 of the opposing parts of the scleral promontory of the eye 140 is significant, which limits the accuracy and reliability of the geometric measurements of the eye determined based on the B-scan 1200. For comparison, Fig. 12B shows a B-scan 1250 acquired by the OCT imaging system 110 according to the present exemplary embodiment. As can be seen in Fig. 12B, the contrast between the representations 1251 and 1252 of the opposing parts of the scleral promontory of the eye 140 is nearly equal, which can significantly improve the accuracy and reliability of the geometric measurements.

[0061] Some of the above exemplary embodiments are summarized in the following numbered clauses E1-E14.

[0062] E1. Use of a fixation target 120 of an optical coherence tomography (OCT) imaging system for equalizing image contrast of representations of opposing portions of the scleral promontory of an eye 140 in anterior segment OCT AS-OCT images acquired by an OCT imaging system 110, 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 such that the axis of the AS-OCT image 130 corresponding to the pupillary axis 153 of the eye 140 is aligned with the direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0063] E2. Fixation target 120 is Obtaining a laterality index of the eye 140; obtaining an indication of an orientation of the pupillary 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 pupillary axis and the visual axis of the eyes of the sample set of eyes and the obtained indication of laterality of the eye 140; setting a position of the fixation target 120 relative to the eye 140 using the acquired indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 such that the axis of the AS-OCT image 130 is aligned with the direction of the AS-OCT image 130 when the gaze direction 151 of the eye 140 is fixed at the position set by the fixation target 120; The use described in E1 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 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0064] E3. The AS-OCT image 130 is a B-scan 200 including a representation of an opposing portion of the scleral promontory of the eye 140; Fixation target 120, obtaining an indication of an orientation of a pupillary axis 153 of the eye 140 relative to a visual axis of the eye 140, acquiring a calibration B-scan 800 of at least a portion of an anterior segment of the eye 140, the calibration B-scan 800 being parallel to the B-scan 200 by setting a gaze direction 151 of the eye 140 using a fixation target 120 such that the visual axis of the eye 140 is aligned with an axial imaging direction 111 of the OCT imaging system 110; determining an orientation of an axis 803 of the calibration B-scan 800 corresponding to the pupillary axis 153 of the eye 140 relative to a direction 801 of the calibration B-scan 800 corresponding to an axial imaging direction 111 of the OCT imaging system 110 as an indication of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis of the eye 140; and using the obtained indication of orientation to set a position of the fixation target 120 relative to the eye 140 during acquisition of the AS-OCT image 130 such that the axis 203 of the B-scan 200 is aligned with the direction 201 of the B-scan 200 when the gaze direction 151 of the eye 140 is fixed in the position set by the fixation target 120; The use described in E1 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 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0065] E4. Identifying representations of anatomical features 804, 805 of the eye 140 in the calibration B-scan 800 to determine an orientation of an axis 803 of the calibration B-scan 800 corresponding to the pupil axis 153 of the eye 140 relative to a direction 801 of the calibration B-scan 800 corresponding to an axial imaging direction 111 of the OCT imaging system 110; determining an orientation of an axis 803 of the calibration B-scan 800 relative to a direction 801 of the calibration B-scan 800 based on the identified representations of the anatomical features 804, 805 of the eye 140; The use according to E3, as determined by

[0066] E5. Fixation target 120 is Obtaining an indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140, by using a fixation target 120 to set the gaze direction 151 of the eye 140 so that the visual axis of the eye 140 is aligned with the axial imaging direction 111 of the OCT imaging system 110, obtaining a first calibration B-scan 1100 of a first cross-section of at least a portion of the anterior segment of the eye 140, and a second calibration B-scan 1140 of a second cross-section of at least a portion of the anterior segment of the eye 140, where 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 of the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 of 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 of the second calibration B-scan 1140 corresponding to a pupil axis 153 of the eye 140 relative to a second direction 151 of the second calibration B-scan 1140 corresponding to an axial imaging direction 111 of the OCT imaging system 110; - determining an indication of an orientation of a pupillary 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, thereby obtaining an indication of an orientation of the pupillary axis 153; setting the position of the fixation target 120 relative to the eye 140 using the acquired indication of orientation during acquisition of the AS-OCT image 130 such that, when the gaze direction 151 of the eye 140 is fixed at a position set by the fixation target 120, an axis of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with a direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110; The use described in E1 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 of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with the direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110.

[0067] E6. The first direction is Identifying a representation of a first anatomical feature of the eye 140 in the first calibration B-scan 1100 to determine an orientation of a first axis 1103 of the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 of the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110; determining an orientation of a first axis 1103 of the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 of the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110 based on a representation of a first anatomical feature of the eye 140 in the first calibration B-scan 1100; The second direction is Identifying a representation of a second anatomical feature of the eye 140 in the second calibration B-scan 1140 to determine an orientation of a second axis 1153 of the second calibration B-scan 1140 corresponding to a pupil axis 153 of the eye 140 relative to a second direction 1151 of the second calibration B-scan 1140 corresponding to an axial imaging direction 111 of the OCT imaging system 110; The use described in E5, by determining an orientation of a second axis 1153 of the second calibration B-scan 1140 corresponding to the pupil axis 153 of the eye 140 relative to a second direction 1151 of the second calibration B-scan 1140 corresponding to the axial imaging direction 111 of the OCT imaging system 110 based on a representation of a second anatomical feature of the eye 140 in the second calibration B-scan 1140.

[0068] E7. The use of any one of E1 to E6, wherein the fixation target 120 includes a graphic 310 displayed by the display device 300, and the display position of the graphic 310 relative to the eye 140 is controllable to control the gaze direction 151 of the eye 140 when the eye 140 fixates on the graphic 310.

[0069] E8. A method of processing an anterior segment optical coherence tomography (AS-OCT) image acquired by an OCT imaging system 110, the AS-OCT image including a representation of an opposing portion of a scleral promontory of an eye, to obtain geometric measurements 160 based on one or more anatomical features of the AS-OCT image 130, the method comprising: acquiring S51 an AS-OCT image 130 while a gaze direction 151 of the eye 140 is fixed by the eye 140 fixating on a fixation target 120 such that an axis of the AS-OCT image 130 corresponding to a pupil axis 153 of the eye 140 is aligned with a direction of the AS-OCT image 130 corresponding to an axial imaging direction 111 of the OCT imaging system 110; processing S52 the acquired AS-OCT images 130 to obtain respective positions in the AS-OCT images 130 of representations of opposing portions of the scleral promontory of the eye 140 in the AS-OCT images 130; and obtaining S53 geometric measurements 160 based on the acquired positions of the AS-OCT images 130.

[0070] E9. Setting a fixation target 120 to fix the gaze direction 151 of the eye 140 during acquisition of the AS-OCT image 130, Obtaining a laterality index of the eye 140 (S61); obtaining S62 an indication of an orientation of the pupillary 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 pupillary axis and the visual axis of the eyes of the sample set of eyes and the obtained indication of laterality of the eye 140; using the obtained indication of the orientation of the pupil axis 153 of the eye 140 relative to the visual axis of the eye 140 to set the position of the fixation target 120 relative to the eye 140 such that the axis of the AS-OCT image 130 is aligned with the direction of the AS-OCT image 130 when the gaze direction 151 of the eye 140 is fixed at the position set by the fixation target 120 S63; The method of E8, further comprising setting a fixation target 120 by

[0071] E10. The AS-OCT image 130 is a B-scan 200 including a representation of the opposing portions of the scleral promontory of the eye, with the fixation target 120 being obtaining an indication of an orientation of a pupillary axis 153 of the eye 140 relative to a visual axis of the eye 140, acquiring S71 a calibration B-scan 800 of at least a portion of an anterior segment of the eye 140, the calibration B-scan 800 being parallel to the B-scan 200 by setting a gaze direction 151 of the eye 140 using a fixation target 120 such that the visual axis of the eye 140 is aligned with an axial imaging direction 111 of the OCT imaging system 110; determining S72 an orientation of an axis 803 of the calibration B-scan 800 corresponding to the pupillary axis 153 of the eye 140 relative to a direction 801 of the calibration B-scan 800 corresponding to an axial imaging direction 111 of the OCT imaging system 110 as an indication of the orientation of the pupillary axis 153 of the eye 140 relative to the visual axis of the eye 140; using the acquired indication of orientation S63 to set a position of the fixation target 120 relative to the eye 140 during acquisition of the AS-OCT image 130 such that the axis of the B-scan is aligned with the direction of the B-scan when the gaze direction 151 of the eye 140 is fixed at the position set by the fixation target 120; The method according to E8, wherein the gaze direction 151 of the eye 140 is fixed during acquisition of the B-scan 200.

[0072] E11. The orientation of the axis 803 of the calibration B-scan 800 relative to the direction 801 of the calibration B-scan 800 is Identifying S91 representations of anatomical features 804, 805 of the eye 140 in the calibration B-scan 800 to determine an orientation of an axis 803 of the calibration B-scan 800 relative to a direction 801 of the calibration B-scan 800; determining S92 an orientation of an axis 803 of the calibration B-scan 800 relative to a direction 801 of the calibration B-scan 800 based on the identified representations of the anatomical features 804, 805 of the eye 140; The method according to E10, wherein the method is determined by

[0073] E12. Fixation target 120 is obtaining an indication of an orientation of a pupillary axis 153 of the eye 140 relative to a visual axis of the eye 140, acquiring 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 1140 of a second cross-section of at least a portion of the 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 the first calibration B-scan 1100 and the second calibration B-scan 1140 are acquired using a fixation target 120 to set a gaze direction 151 of the eye 140 such that the visual axis of the eye 140 is aligned with an axial imaging direction 111 of the OCT imaging system 110; Determining S102 a first orientation of a first axis 1103 of the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 of the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110; Determining S103 a second orientation of a second axis 1153 of the second calibration B-scan 1140 corresponding to a pupil axis 153 of the eye 140 relative to a second direction 1151 of the second calibration B-scan 1140 corresponding to an axial imaging direction 111 of the OCT imaging system 110; determining S104 an indication of an orientation of a pupillary 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, thereby obtaining an indication of the orientation of the pupillary axis 153; using the acquired indication of orientation during acquisition of the AS-OCT image 130 to set a position of the fixation target 120 relative to the eye 140 such that, when the gaze direction 151 of the eye 140 is fixed at a position set by the fixation target 120, an axis of the AS-OCT image 130 corresponding to the pupil axis 153 of the eye 140 is aligned with a direction of the AS-OCT image 130 corresponding to the axial imaging direction 111 of the OCT imaging system 110; S63; The method according to E8, wherein the gaze direction 151 of the eye 140 is fixed during acquisition of the B-scan 200.

[0074] E13. The orientation of the first axis 1103 of the first calibration B-scan 1100 relative to the first direction 1101 of the first calibration B-scan 1100 is: Identifying S91 a representation of a first anatomical feature of the eye 140 in the first calibration B-scan 1100 to determine an orientation of a first axis 1103 of the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 of the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110; determining S91 an orientation of a first axis 1103 of the first calibration B-scan 1100 corresponding to a pupil axis 153 of the eye 140 relative to a first direction 1101 of the first calibration B-scan 1100 corresponding to an axial imaging direction 111 of the OCT imaging system 110 based on a representation of a first anatomical feature of the eye 140 in the first calibration B-scan 1100; an orientation of a second axis 1153 of the second calibration B-scan 1140 relative to a second direction 1151 of the second calibration B-scan 1140 is Identifying S91 a representation of a second anatomical feature of the eye 140 in the second calibration B-scan 1140 to determine an orientation of a second axis 1153 of the second calibration B-scan 1140 corresponding to a pupil axis 153 of the eye 140 relative to a second direction 1151 of the second calibration B-scan 1140 corresponding to an axial imaging direction 111 of the OCT imaging system 110; determining an orientation of a second axis 1153 of the second calibration B-scan 1140 corresponding to a pupil axis 153 of the eye 140 relative to a second direction 1151 of the second calibration B-scan 1140 corresponding to an axial imaging direction 111 of the OCT imaging system 110 based on the representation of a second anatomical feature of the eye 140 in the second calibration B-scan 1140 S92; The method according to E12, wherein the

[0075] E14. The method of any one of E8 to E13, wherein the geometric measurement 160 is a measurement of the anterior chamber angle of the eye 140.

[0076] In the preceding description, exemplary aspects have been described with reference to several exemplary embodiments. This specification should therefore be considered illustrative rather than restrictive. Similarly, the diagrams shown in the drawings that highlight features and advantages of the exemplary embodiments are presented for illustrative purposes only. The architecture of the exemplary embodiments is sufficiently flexible and configurable to be utilized in ways other than those shown in the accompanying figures.

[0077] Some aspects of the examples presented herein, such as the functionality of the controller 115 and / or data processing hardware 140, may be provided as computer programs, or software, e.g., one or more programs having instructions or sequences of instructions contained or stored in an article of manufacture, such as a machine-accessible or machine-readable medium, instruction store, or computer-readable storage device, each of which may be non-transitory in an example embodiment. The programs or instructions in the non-transitory machine-accessible medium, machine-readable medium, instruction store, or computer-readable storage device may be used to program a computer system or other electronic device. Machine or computer-readable media, instruction stores, and storage devices may include, but are not limited to, floppy diskettes, optical disks, and magneto-optical disks, or other types of media / machine-readable media / instruction stores / storage devices suitable for storing or transmitting electronic instructions. The techniques described herein are not limited to any particular software configuration. They may find applicability in any computing or processing environment. As used herein, the terms "computer-readable," "machine-accessible medium," "machine-readable medium," "instruction store," and "computer-readable storage device" are intended to include any medium that can store, encode, or transmit instructions or sequences of instructions for execution by a machine, computer, or computer processor, causing the machine / computer / computer processor to perform any one of the methods described herein. Furthermore, it is common in the art to refer to software in one form or another (e.g., program, procedure, process, application, module, unit, logic, etc.) as taking an action or causing a result. Such expressions are merely a shorthand way of stating that execution of the software by a processing system causes the processor to perform an operation to produce a result.

[0078] Some or all of the functionality of controller 115 and / or data processing hardware 140 may also be implemented by the preparation of application specific integrated circuits, field programmable gate arrays, or by interconnecting an appropriate network of conventional component circuits.

[0079] The computer program product may be provided in the form of one or more storage media, instruction stores, or storage devices having instructions stored thereon that can be used to cause a computer or computer processor to control or execute any of the procedures of the exemplary embodiments described herein. Storage media / instruction storage devices may include, by way of example and not limitation, optical disks, ROM, RAM, EPROM, EEPROM, DRAM, VRAM, flash memory, flash cards, magnetic cards, optical cards, nanosystems, molecular memory integrated circuits, RAID, remote data storage / archive / warehousing, and / or any other type of device suitable for storing instructions and / or data.

[0080] Some implementations stored on any one of the one or more computer readable media, one or more instruction stores, or one or more storage devices include software for controlling both the hardware of the system and for enabling the system or microprocessor to utilize the results of the exemplary embodiments described herein to interact with a human user or other mechanisms. Such software may include, but is not limited to, device drivers, operating systems, and user applications. Finally, such computer readable media or storage devices further include software for performing the exemplary aspects of the present invention, as described above.

[0081] The programming and / or software of the system includes software modules for performing the procedures described herein, in some exemplary embodiments herein the modules include software, while in other exemplary embodiments herein the modules include hardware or a combination of hardware and software.

[0082] 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 by way of limitation. It will be apparent to those skilled in the art that various changes in form and detail can be made. For example, although the processes shown in Figures 5 to 7, 9, and 10 are performed in the order indicated by the arrows between the steps therein, some of the processes may be performed in parallel. For example, processes S102 and S103 in Figure 10 may be performed in parallel. Thus, the present invention should not be limited by any of the exemplary embodiments described above, but should be defined only in accordance with the following claims and their equivalents.

[0083] Moreover, the purpose of the Abstract is to enable the Patent Office and the public, particularly those skilled in the art, scientists, engineers and practitioners who are not familiar with patent or legal terms or phrases, to quickly determine the nature and substance of the technical disclosure of the present application from a cursory inspection. The Abstract is not intended to be limiting in any way with respect to the scope of the exemplary embodiments presented herein. It should also be understood that the steps recited in the claims need not be performed in the order presented.

[0084] Although this specification contains many specific embodiment details, these should not be construed as limitations on the scope of any invention or what may be claimed, but rather as descriptions of features specific to the specific embodiments described herein. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in a particular combination and initially claimed as such, one or more features from a claimed combination may, in some cases, be deleted from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0085] In certain circumstances, multitasking and parallel processing may be advantageous. Furthermore, the separation of various components in the above-described embodiments should not be understood to require such separation in all embodiments, and it should be understood that the program components and systems described may generally be integrated together in a single software product or packaged into multiple software products.

[0086] Having now described several exemplary embodiments and implementations, it is clear that the above are presented by way of example and not by way of limitation. In particular, while many of the examples presented herein include specific combinations of device or software elements, those elements may be combined in other ways to achieve the same purpose. Operations, elements, and features discussed only in relation to one embodiment are not intended to be excluded from a similar role in other embodiments or implementations.

Claims

1. 1. A system (100) configured to process an AS-OCT image (130), which is an optical coherence tomography image of an anterior segment of an eye (140) including a representation of a portion of a scleral spur of the eye (140), to obtain geometric measurements (160) of the eye (140), the system (100) comprising: Data processing hardware (150), processing the AS-OCT images (130) to obtain respective positions in the AS-OCT images (130) of the representations of the portions of the scleral spur of the eye (140) in the AS-OCT images (130); data processing hardware (140) configured to obtain the geometric measurements (160) based on the obtained positions; A system (100) comprising: an OCT imaging system (110) operable to acquire the AS-OCT image (130), the OCT imaging system (110) including a fixation target (120) positioned to fix a gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) such that an axis of the AS-OCT image (130) corresponding to a pupil axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to an axial imaging direction (111) of the OCT imaging system (110).

2. the OCT imaging system (110) including a controller (115) configured to control the OCT imaging system (110) to obtain the AS-OCT image (130); The controller (115): obtaining a laterality index of the eye (140); obtaining an indication of an orientation of the pupillary axis (153) of the eye (140) relative to the visual axis of the eye (140) based on measurements of relative orientations of the pupillary axis (153) and visual axis of the eyes of the sample set of eyes and the obtained indication of the laterality of the eye (140); setting a position of the fixation target (120) relative to the eye (140) using the acquired indication of the orientation of the pupil axis (153) of the eye (140) relative to the visual axis of the eye (140) such that, when the gaze direction (151) of the eye (140) is fixed at the position set by the fixation target (120), the axis of the AS-OCT image (130) is aligned with the direction of the AS-OCT image (130); The system (100) of claim 1, further configured to control the fixation target (120) to fix the gaze direction (151) of the eye (140) during acquisition of the AS-OCT image (130) by:

3. the AS-OCT image (130) being a B-scan (200) including the representation of the portion of the scleral spur of the eye (140), the OCT imaging system (110) including a controller (115) configured to control the OCT imaging system (110) to obtain the AS-OCT image (130), the controller (115) being configured to: obtaining an indication of an orientation of the pupillary axis (153) of the eye (140) relative to a visual axis of the eye (140), controlling the OCT imaging system (110) to obtain a calibration B-scan (800) of at least a portion of the anterior segment of the eye (140), the calibration B-scan (800) being parallel to the calibration B-scan (800) by controlling the fixation target (120) to set the gaze direction (151) of the eye (140) such that the visual axis of the eye (140) is aligned with the axial imaging direction (111) of the OCT imaging system (110); obtaining an indication of the orientation of the pupillary axis (153) of the eye (140) relative to the visual axis of the eye (140) by determining an orientation of an axis (803) of the calibration B-scan (800) corresponding to the pupillary axis (153) of the eye (140) relative to a direction (801) of the calibration B-scan (800) corresponding to the axial imaging direction (111) of the OCT imaging system (110); using the acquired indication of orientation to set a position of the fixation target (120) relative to the eye (140) during acquisition of the AS-OCT image (130) such that when the gaze direction (151) of the eye (140) is fixed at the set position by the fixation target (120), the axis (203) of the B-scan (200) is aligned with the direction (201) of the B-scan (200); 2. The system (100) of claim 1, further configured to control the fixation target (120) to fix the gaze direction (151) of the eye (140) during acquisition of the B-scan (200) by:

4. The controller (115): identifying representations of anatomical features (804, 805) of the eye (140) in the calibration B-scan (800) to determine the orientation of the axis (803) of the calibration B-scan (800) relative to the direction (801) of the calibration B-scan (800); determining an orientation of the axis (803) of the calibration B-scan (800) relative to the direction (801) of the calibration B-scan (800) based on the identified representations of the anatomical features (804, 805) of the eye (140); 4. The system (100) of claim 3, configured to determine the orientation of the axis (803) of the calibration B-scan (800) relative to the direction (801) of the calibration B-scan (800) by:

5. the OCT imaging system (110) including a controller (115) configured to control the OCT imaging system (110) to obtain the AS-OCT image (130); The controller (115): obtaining an indication of an orientation of the pupillary axis (153) of the eye (140) relative to a visual axis of the eye (140), 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 the anterior segment of the eye (140) by using the fixation target (120) to set the gaze direction (151) of the eye (140) such that the visual axis of the eye (140) is aligned with the axial imaging direction (111) of the OCT imaging system (110) and a second calibration B-scan (1140) of a second cross-section of at least a portion of the anterior segment of the eye (140), the plane of the first cross-section being perpendicular to the plane of the second cross-section; determining a first orientation of a first axis (1103) of the first calibration B-scan (1100) corresponding to the pupillary axis (153) of the eye (140) relative to a first direction (1101) of the first calibration B-scan (1100) corresponding to the axial imaging direction (111) of the OCT imaging system (110); determining a second orientation of a second axis (1153) of the second calibration B-scan (1140) corresponding to the pupillary axis (153) of the eye (140) relative to a second direction (1151) of the second calibration B-scan (1140) corresponding to the axial imaging direction (111) of the OCT imaging system (110); determining the indication of an orientation of the pupillary axis (153) of the eye (140) relative to the visual axis of the eye (140) based on the determined first orientation and the determined second orientation, thereby obtaining an indication of an orientation of the pupillary axis (153); setting a position of the fixation target (120) relative to the eye (140) using the acquired indication of orientation during acquisition of the AS-OCT image (130) such that, when the gaze direction (151) of the eye (140) is fixed at the set position by the fixation target (120), an axis of the AS-OCT image (130) corresponding to the pupil axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to the axial imaging direction (111) of the OCT imaging system (110); 2. The system (100) of claim 1, further configured to control the fixation target (120) to fix the gaze direction (151) of the eye (140) during acquisition of the B-scan (200) by:

6. The controller (115): identifying a representation of a first anatomical feature of the eye (140) in the first calibration B-scan (1100) to determine an orientation of the first axis (1103) of the first calibration B-scan (1100) corresponding to the pupillary axis (153) of the eye (140) relative to the first direction (1101) of the first calibration B-scan (1100) corresponding to the axial imaging direction (111) of the OCT imaging system (110); determining an orientation of the first axis (1103) of the first calibration B-scan (1100) corresponding to the pupil axis (153) of the eye (140) relative to the first direction (1101) of the first calibration B-scan (1100) corresponding to the axial imaging direction (111) of the OCT imaging system (110) based on the representation of the first anatomical feature of the eye (140) of the first calibration B-scan (1100); and the controller (115) is configured to determine the orientation of the first axis (1103) of the first calibration B-scan (1100) relative to the first direction (1101) of the first calibration B-scan (1100) by identifying a representation of a second anatomical feature of the eye (140) in the second calibration B-scan (1140) to determine an orientation of the second axis (1153) of the second calibration B-scan (1140) corresponding to the pupillary axis (153) of the eye (140) relative to the second direction (1151) of the second calibration B-scan (1140) corresponding to the axial imaging direction (111) of the OCT imaging system (110); determining an orientation of the second axis (1153) of the second calibration B-scan (1140) corresponding to the pupil axis (153) of the eye (140) relative to the second direction (1151) of the second calibration B-scan (1140) corresponding to the axial imaging direction (111) of the OCT imaging system (110) based on the representation of the second anatomical feature of the eye (140) of the second calibration B-scan (1140); 6. The system (100) of claim 5, configured to determine the orientation of the second axis (1153) of the second calibration B-scan (1140) relative to the second direction (1151) of the second calibration B-scan (1140) by:

7. The system (100) of any one of claims 1 to 6, wherein the geometric measurement (160) is a measurement of the anterior chamber angle of the eye (140).

8. The system (100) of any one of claims 1 to 7, wherein the OCT imaging system (110) further includes a display device (300) configured to display a graphic (310) as the fixation target (120), and the controller (115) is configured to control the display position of the graphic (310) relative to the eye (140) so as to control the gaze direction (151) of the eye (140) when the eye (140) fixates on the graphic (310).

9. Use of a fixation target (120) of an OCT imaging system (110), which is an optical coherence tomography imaging system, for equalizing image contrast of a representation of a portion of the scleral promontory of an eye (140) in an AS-OCT image (130), which is an OCT image of the anterior segment of the eye acquired by the 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) such that an axis of the AS-OCT image (130) corresponding to a pupillary axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to an axial imaging direction (111) of the OCT imaging system (110).

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

11. the AS-OCT image (130) is a B-scan (200) including the representation of the portion of the scleral spur of the eye (140); The fixation target (120) obtaining an indication of an orientation of the pupillary axis (153) of the eye (140) relative to a visual axis of the eye (140), acquiring a calibration B-scan (800) of at least a portion of the anterior segment of the eye (140), the calibration B-scan (800) being parallel to the B-scan (200) by setting the 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); obtaining an indication of the orientation of the pupillary axis (153) of the eye (140) relative to the visual axis of the eye (140) by determining an orientation of an axis (803) of the calibration B-scan (800) corresponding to the pupillary axis (153) of the eye (140) relative to a direction (801) of the calibration B-scan (800) corresponding to the axial imaging direction (111) of the OCT imaging system (110); using the acquired indication of orientation to set a position of the fixation target (120) relative to the eye (140) during acquisition of the AS-OCT image (130) such that when the gaze direction (151) of the eye (140) is fixed at the set position by the fixation target (120), the axis (203) of the B-scan (200) is aligned with the direction (201) of the B-scan (200); The use of claim 9, wherein the AS-OCT image (130) is used to equalize the image contrast by fixing the line of sight (151) of the eye (140) during acquisition of the AS-OCT image (130) so that the axis of the AS-OCT image (130) corresponding to the pupil axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to the axial imaging direction (111) of the OCT imaging system (110).

12. The fixation target (120) obtaining an indication of an orientation of the pupillary axis (153) of the eye (140) relative to a visual axis of the eye (140), by using the fixation target (120) to set the gaze direction (151) of the eye (140) such that the visual axis of the eye (140) is aligned with the axial imaging direction (111) of the OCT imaging system (110); obtaining a first calibration B-scan (1100) of a first cross-section of at least a portion of the anterior segment of the eye (140); and a second calibration B-scan (1140) of a second cross-section of at least a portion of the anterior segment of the eye (140), the plane of the first cross-section being perpendicular to the plane of the second cross-section; determining a first orientation of a first axis (1103) of the first calibration B-scan (1100) corresponding to the pupillary axis (153) of the eye (140) relative to a first direction (1101) of the first calibration B-scan (1100) corresponding to the axial imaging direction (111) of the OCT imaging system (110); determining a second orientation of a second axis (1153) of the second calibration B-scan (1140) corresponding to the pupillary axis (153) of the eye (140) relative to a second direction (1151) of the second calibration B-scan (1140) corresponding to the axial imaging direction (111) of the OCT imaging system (110); determining the indication of an orientation of the pupillary axis (153) of the eye (140) relative to the visual axis of the eye (140) based on the determined first orientation and the determined second orientation, thereby obtaining an indication of an orientation of the pupillary axis (153); setting a position of the fixation target (120) relative to the eye (140) using the acquired indication of orientation during acquisition of the AS-OCT image (130) such that an axis of the AS-OCT image (130) corresponding to the pupil axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to the axial imaging direction (111) of the OCT imaging system (110) when the gaze direction (151) of the eye (140) is fixed at a position set by the fixation target (120); The use of claim 9, wherein the AS-OCT image (130) is used to equalize the image contrast by fixing the line of sight (151) of the eye (140) during acquisition of the AS-OCT image (130) so that the axis of the AS-OCT image (130) corresponding to the pupil axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to the axial imaging direction (111) of the OCT imaging system (110).

13. The use of any one of claims 9 to 12, wherein the fixation target (120) comprises a graphic (310) displayed by a display device (300), and the display position of the graphic (310) relative to the eye (140) is controllable to control the gaze direction (151) of the eye (140) when the eye (140) fixates on the graphic (310).

14. 1. A method of processing an AS-OCT image (130), which is an optical coherence tomography image of an anterior segment of an eye (140) acquired by an OCT imaging system (110), including a representation of a portion of a scleral spur of an eye (140), to obtain geometric measurements (160) based on one or more anatomical features of the AS-OCT image (130), the method comprising: acquiring (S51) the AS-OCT image (130) while a gaze direction (151) of the eye (140) is fixed by the eye (140) fixating on a fixation target (120) such that an axis of the AS-OCT image (130) corresponding to a pupil axis (153) of the eye (140) is aligned with a direction of the AS-OCT image (130) corresponding to an axial imaging direction (111) of the OCT imaging system (110); processing (S52) the acquired AS-OCT image (130) to obtain a respective position in the AS-OCT image (130) of the representation of the portion of the scleral spur of the eye (140) in the AS-OCT image (130); and obtaining (S53) the geometric measurements (160) based on the obtained positions of the AS-OCT images (130).

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

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