Patent Application
20250082199
This application claims priority to European Application No. EP 23 197 119.3, filed Sep. 13, 2023, which is hereby incorporated by reference in entirety for all purposes.
Example aspects herein generally relate to the field of optical coherence tomography (OCT) imaging systems and, in particular, to Fourier-domain OCT imaging systems for acquiring optoretinography (ORG) data indicative of a physiological response of a retina of an eye of a subject to an optical stimulus.
Optical coherence tomography (OCT) is an imaging technique based on low-coherence interferometry, which is widely used to acquire high-resolution two- and three-dimensional images of optical scattering media, such as biological tissue.
OCT imaging systems can be classified as being time-domain OCT (TD-OCT) or Fourier-domain OCT (FD-OCT) (also referred to as frequency-domain OCT), depending on how depth ranging is achieved. In TD-OCT, an optical path length of a reference arm of the imaging system's interferometer is varied in time during the acquisition of a reflectivity profile of the scattering medium being imaged by the OCT imaging system (referred to herein as the “imaging target”), the reflectivity profile being commonly referred to as a “depth scan” or “axial scan” (“A-scan”). In FD-OCT, a spectral interferogram resulting from an interference between light in the reference arm and light in the sample arm of the interferometer at each A-scan location is Fourier transformed to simultaneously acquire all points along the depth of the A-scan, without requiring any variation in the optical path length of the reference arm. FD-OCT can allow much faster imaging than scanning of the sample arm mirror in the interferometer, as all the back-reflections from the sample are measured simultaneously. Two common types of FD-OCT are spectral-domain OCT (SD-OCT) and swept-source OCT (SS-OCT). In SD-OCT, a broadband light source delivers many wavelengths to the imaging target, and all wavelengths are measured simultaneously using a spectrometer as the detector. In SS-OCT (also referred to as time-encoded frequency-domain OCT), the light source is swept through a range of wavelengths, and the temporal output of the detector is converted to spectral interference.
OCT imaging systems can also be classified as being point-scan (also known as “point detection” or “scanning point”), line-scan or full-field, depending on how the imaging system is configured to acquire OCT data at locations on the imaging target. A point-scan OCT imaging system acquires OCT data by scanning a focused sample beam across the surface of the imaging target, typically along a single line (which may be straight, or alternatively curved so as to define a circle or a spiral, for example) or along a set of (usually substantially parallel) lines on the surface of the imaging target, and acquiring an axial depth profile (A-scan) for each of a plurality of points along the line(s), one single point at a time, to build up OCT data comprising a one- or two-dimensional array of A-scans representing a two-dimensional (i.e. a B-scan) or three-dimensional (i.e. a C-scan or volumetric scan) reflectance profile of the sample.
A line-scan OCT imaging system acquires OCT data by scanning a focused line of light across the surface of the imaging target. Measured reflectance from the imaging target is used to generate OCT data comprising a two-dimensional reflectance profile (i.e. a B-scan) of the sample. By scanning the focused line of light across a plurality of locations on the imaging target, OCT data comprising a three-dimensional reflectance profile (i.e. a C-scan or volumetric scan) of the sample can be obtained. Typically, the focused line of light is straight and is scanned in a direction perpendicular to it, although in some instances it may be curved with the scanning direction adjusted accordingly. A full-field OCT imaging system acquires OCT data by projecting a beam of light onto the imaging target to acquire OCT data comprising a three-dimensional reflectance profile (i.e. a C-scan or volumetric scan) of the sample.
OCT imaging systems can also be classified as being phase-resolved, where both the intensity and phase of the light reflected from the imaging target are measured as a function of axial depth. Modern FD-OCT imaging systems often have a degree of phase stability that allows them to function as phase-resolved OCT imaging systems.
Optoretinography (ORG) generally refers to the detection of a physiological response of a retina of an eye to an optical stimulus (i.e. light-induced functional activity of the retina). ORG techniques include the non-invasive optical imaging of this physiological response of the retina. For example, OCT imaging systems can be used to image retinal neurons exhibiting a change in dimension (size) in response to excitation by the optical stimulus. These changes in dimension have been shown to be detectable by phase-resolved OCT imaging systems and are typically changes in length of the outer segments of cone photoreceptors in the retina that are detected by measuring the change in axial depth of the inner-outer segment (IS/OS) junction and of the cone outer segment tip (COST) of the cone photoreceptors.
There is provided, in accordance with a first example aspect herein, a Fourier-domain optical coherence tomography (FD-OCT) apparatus arranged to acquire optoretinography, (ORG) data that is indicative of a physiological response of a retina of an eye of a subject to an optical stimulus. The FD-OCT apparatus comprises an optical system operable to apply the optical stimulus to the retina, an FD-OCT imaging system operable to acquire OCT data by imaging a portion of the retina, and a controller. The controller is arranged to: control the FD-OCT imaging system to acquire OCT data of a plurality of portions of the retina such that, for each portion of the plurality of portions of the retina, at least some of the OCT data acquired from the portion is acquired after a respective optical stimulus has been applied to the portion by the optical system; generate, based on the acquired OCT data, respective ORG data for each portion of the plurality of portions of the retina which is indicative of the respective response of the portion of the retina to the optical stimulus applied to the portion of the retina by the optical system; and store, for each portion of the plurality of portions of the retina, the respective ORG data generated for the portion in association with a respective indication of a position in a visual field of the eye of a point that is optically conjugate with a corresponding position of the portion on the retina.
The controller may be further arranged to determine a respective indication of a position on the retina of each portion of the plurality of portions of the retina at which OCT data is to be acquired by the FD-OCT imaging system by determining, for each point of a plurality of points in the visual field of the eye, a respective indication of a corresponding position on the retina that is optically conjugate with the point. Alternatively, the controller may be further arranged to: determine a respective indication of a position on the retina of each portion of the plurality of portions of the retina at which OCT data is to be acquired by the FD-OCT imaging system based on an image of the retina of the eye; and determine, for each portion of the plurality of portions of the retina, the respective indication of the position in the visual field of the eye of the point that is optically conjugate with the position of the portion on the retina.
The FD-OCT apparatus may further comprise a display device, and the controller may be further arranged to: acquire data indicating how measurements of the subject's ability to see optical stimuli applied confined to respective different portions of the retina of the eye at different respective locations on the retina are distributed over at least a part of a visual field of the eye; control the display device, based on at least some of the acquired data, to display a first map indicative of how the subject's ability to see the optical stimuli is distributed over the at least a part of a visual field of the eye; and control the display device, based on at least some of the stored ORG data and the associated stored indications, to display a second map for comparison with the first map, the second map indicating how the physiological response of the retina to the optical stimulus indicated by at least some of the stored ORG data is distributed over the at least a part of the visual field of the eye.
There is provided, in accordance with a second example aspect herein, a Fourier-domain optical coherence tomography (FD-OCT) apparatus arranged to acquire optoretinography (ORG) data that is indicative of a physiological response of a retina of an eye of a subject to an optical stimulus. The FD-OCT apparatus comprises an optical system operable to apply the optical stimulus to the retina, an FD-OCT imaging system operable to acquire OCT data by imaging a portion of the retina, and a controller. The controller is arranged to: control the FD-OCT imaging system to acquire OCT data of a plurality of portions of the retina such that, for each portion of the plurality of portions of the retina, at least some of the OCT data acquired from the portion is acquired after a respective optical stimulus has been applied to the portion by the optical system; generate, based on the acquired OCT data, respective ORG data for each portion of the plurality of portions of the retina which is indicative of the respective response of the portion of the retina to the optical stimulus applied to the portion of the retina; store, for each portion of the plurality of portions of the retina, the respective ORG data generated from OCT data acquired from the portion in association with a respective indication of a location of the portion on the retina; and acquire data indicating how measurements of the subject's ability to see optical stimuli that are confined to respective different portions of the retina of the eye at different respective locations on the retina are distributed over the at least a part of the retina of the eye. The controller may be arranged to acquire the data, which indicates how measurements of the subject's ability to see optical stimuli applied to respective different locations on the retina of the eye are distributed over at least a part of the retina of the eye, by: receiving visual field test data acquired from the eye by a visual field-testing device, the visual field test data comprising measurements of the subject's ability to see optical stimuli applied from a plurality of points in the visual field of the eye of the subject; and determining, for each point of the plurality of points in the visual field of the eye, a respective indication of a corresponding position on the retina that is optically conjugate with the point. Alternatively, the controller may be arranged to acquire the data, which indicates how measurements of the subject's ability to see optical stimuli applied to respective different locations on the retina of the eye are distributed over at least a part of the retina of the eye, by: receiving indications, provided by the subject, of whether the subject saw the respective optical stimulus applied to each portion of the plurality of portions of the retina by the optical system; and associating each of the received indications with a respective indication of a location of the respective portion on the retina. In either case, the FD-OCT apparatus may further comprise a display device, and the controller may be further arranged to: control the display device, based on at least some of the acquired data, to display a first map indicative of how the subject's ability to see the optical stimuli with the eye is distributed over at least a part of the retina of the eye; and control the display device, based on at least some of the generated ORG data and positions of the portions of the retina from which the at least some of the ORG data was generated, to display a second map for comparison with the first map, the second map being indicative of how the response of the retina to optical stimulus, which is indicated by the at least some of the generated ORG data is distributed over the at least a part of the retina of the eye.
The controller may be further arranged to compare data of the first map with data of the second map and identify, based on the comparison, at least one of: one or more first regions of the at least a part of the visual field, indicating that the subject is able to see visual field test optical stimuli in the one or more first regions of the at least a part of the visual field, and indicating that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which satisfies a predetermined condition; one or more second regions of the at least a part of the visual field, indicating that the subject has an inability to see visual field test optical stimuli in the one or more second regions of the at least a part of the visual field, and indicating that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which satisfies the predetermined condition; one or more third regions of the at least a part of the visual field, indicating that the subject is able to see visual field test optical stimuli in the one or more third regions of the at least a part of the visual field, and indicating that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which does not satisfy the predetermined condition; or one or more fourth regions of the at least a part of the visual field, indicating that the subject has an inability to see visual field test optical stimuli in the one or more fourth regions of the at least a part of the visual field, and indicating that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which does not satisfy the predetermined condition.
The FD-OCT apparatus of an example embodiment may further comprise a fixation target arranged to fix a gaze direction of the eye, and the optical system may be operable to apply the optical stimulus to the retina such that an illumination of the retina by the optical stimulus is confined to a portion of the retina, the optical system being controllable by the controller to vary a location on the retina at which the optical stimulus is to be applied and comprising a light source arranged to generate light which provides the optical stimulus, and one or more scanning elements arranged to direct the light to the retina. In this example embodiment, the controller may be further arranged to: acquire an indicator of a target location on the retina at which the optical stimulus is to be applied by the optical system; use the acquired indicator to control the one or more scanning elements of the optical system, while a position of the fixation target relative to the eye remains fixed, to direct the light to a first portion of the retina which is at the target location; control the FD-OCT imaging system to acquire OCT data of a second portion of the retina, wherein at least a part of the second portion of the retina is disposed in relation to the first portion so as to be stimulated by the applied optical stimulus during acquisition of at least some of the OCT data; and generate ORG data based on the acquired OCT data of the second portion of the retina.
In the FD-OCT apparatus of the example embodiment, the FD-OCT imaging system may further comprise an interferometer having a sample arm and a reference arm, and a detector arranged to detect an interference between sample OCT light propagating along the sample arm after having been scattered from the retina, and reference OCT light propagating along the reference arm. At least one of the one or more scanning elements may be further arranged to direct the sample OCT light toward the second portion of the retina, and the sample OCT light scattered from the second portion of the retina toward the detector.
Alternatively, the FD-OCT imaging system may comprise an interferometer having a sample arm and a reference arm, one or more scanning elements, and a detector arranged to detect an interference between sample OCT light propagating along the sample arm after having been scattered from the retina, and reference OCT light propagating along the reference arm. Furthermore, the one or more scanning elements may be arranged to direct the sample OCT light toward the second portion of the retina, and the sample OCT light scattered from the second portion of the retina toward the detector. In this alternative, the one or more scanning elements of the optical system are different from the one or more scanning elements of the FD-OCT imaging system. In addition, the controller may be arranged to use the acquired indicator to control the one or more scanning elements of the optical system independently from the one or more scanning elements of the FD-OCT imaging system while the position of the fixation target relative to the eye remains fixed.
Each first portion of the retina may be smaller than a region of the retina over which the FD-OCT imaging system is operable to acquire OCT data. There is provided, in accordance with a third example aspect herein, a computer-implemented method of controlling a Fourier-domain optical coherence tomography (FD-OCT) apparatus to acquire optoretinography (ORG) data indicative of a physiological response of a retina of an eye of a subject to an optical stimulus. The FD-OCT apparatus comprises an optical system operable to apply the optical stimulus to the retina, and an FD-OCT imaging system operable to acquire OCT data by imaging a portion of the retina. The method comprises: controlling the FD-OCT imaging system to acquire OCT data of a plurality of portions of the retina such that, for each portion of the plurality of portions of the retina, at least some of the OCT data acquired from the portion is acquired after a respective optical stimulus has been applied to the portion by the optical system; generating, based on the acquired OCT data, respective ORG data for each portion of the plurality of portions of the retina which is indicative of the respective response of the portion of the retina to the optical stimulus applied to the portion of the retina by the optical system; and storing, for each portion of the plurality of portions of the retina, the respective ORG data generated for the portion in association with a respective indication of a position in a visual field of the eye of a point that is optically conjugate with a corresponding position of the portion on the retina.
There is provided, in accordance with a fourth example aspect herein, a computer-implemented method of controlling a Fourier-domain optical coherence tomography (FD-OCT) apparatus to acquire optoretinography (ORG) data indicative of a physiological response of a retina of an eye of a subject to an optical stimulus. The FD-OCT apparatus comprises an optical system operable to apply the optical stimulus to the retina, and an FD-OCT imaging system operable to acquire OCT data by imaging a portion of the retina. The method comprises: controlling the FD-OCT imaging system to acquire OCT data of a plurality of portions of the retina such that, for each portion of the plurality of portions of the retina, at least some of the OCT data acquired from the portion is acquired after a respective optical stimulus has been applied to the portion by the optical system; generating, based on the acquired OCT data, respective ORG data for each portion of the plurality of portions of the retina which is indicative of the respective response of the portion of the retina to the optical stimulus applied to the portion of the retina; storing, for each portion of the plurality of portions of the retina, the respective ORG data generated from OCT data acquired from the portion in association with a respective indication of a location of the portion on the retina; and acquiring data indicating how measurements of the subject's ability to see optical stimuli that are confined to respective different portions of the retina of the eye at different respective locations on the retina are distributed over the at least a part of the retina of the eye.
There is provided, in accordance with a fifth example aspect herein, a computer program comprising computer-readable instructions which, when executed by a computer, cause the computer to perform a method according to at least one of the third example aspect and the fourth example aspect above. The computer program may be stored on a non-transitory computer-readable storage medium or may be carried by a signal, for example.
Example embodiments will now be explained in detail, by way of non-limiting example only, with reference to the accompanying figures described below. Like reference numerals appearing in different ones of the figures can denote identical or functionally similar elements, unless indicated otherwise.
Visual field tests are widely used to determine the extent of, and function within, the visual field of an eye. A visual field test relies on the subject to provide an indication (often in the form of a button press or by verbal communication) that they are able to see an optical stimulus presented to the subject from a location within the visual field of the eye being tested. Perimetry is a type of visual field test where the visual field of the eye is systematically measured. A variety of perimetry techniques are known such as automatic static perimetry, the Goldmann method and microperimetry, for example.
Such visual field tests are based on the output of the whole visual pathway of the eye, i.e. the collective functionally of the visual pathway which results in the subject's perception of whether or not they are able to see an optical stimulus being presented to them. Accordingly, it is difficult or impossible to attribute an inability of a subject to see an applied optical stimulus within the visual field of their eye recorded in a visual field test to a particular intermediary within the visual pathway of the eye, and this limits both the extent and accuracy to which a clinically useful diagnosis can be made. Prior efforts to fill this gap in physiological information regarding the visual pathway have tended to focus on microperimetry, whereby the visual field data is displayed on a retinal image to facilitate the correlation of functional abnormalities with structural features on the retina. However, this relies on an interpretation of structural features on the retina's surface, rather than providing any definitive indication of the function of the retina at a given point in the eye.
In view of the above-described problems, the inventors have devised a Fourier-domain optical coherence tomography (FD-OCT) apparatus which is arranged to acquire optoretinography (ORG) data and store this data in association with an indication of a position in a visual field of the eye of a point that is optically conjugate with a corresponding position of the OCT data used to generate the ORG data, so that the ORG data may be displayed alongside visual field test data acquired by a perimetry device, for example. The inventors have also devised a FD-OCT apparatus which is arranged to acquire data indicating how the subject's ability to see optical stimuli is distributed over a part of the retina (as may be acquired from a microperimetry device, for example) and, for comparison, further data which is derived from acquired ORG data and indicates how the response of the retina to optical stimuli is distributed over the part of the retina.
The ORG data may thus be used to provide information, complementary to that acquired from a visual field test or the like, regarding the functionality of the photoreceptor cells of the eye that form part of within the visual pathway of the subject. This information may allow the clinician to gain a valuable insight quickly and easily into possible causes of a vision loss (or impaired vision) in a region of the eye's visual field or retina identified by the results of a visual field test. The information may, for example, allow the clinician to quickly and accurately identify a region of the eye's visual field or retina for which a loss of impairment of vision due to the abnormal functionality of photoreceptor cells can be ruled out with a reasonable degree of certainty. The information may further enable the identification of false positives in the visual field test (e.g. where the subject has indicated they are able to see the optical stimulus but there has been no observed retinal response to corroborate this) and the affirmation of negative results, thus improving the accuracy of the visual field test data.
Example embodiments of the aforementioned FD-OCT imaging apparatus will now be described in detail with reference to the accompanying drawings.
The fixation target 110 is arranged to fix a gaze direction 161 of the eye 160 (i.e. a direction away from the eye 160 along the visual axis of the eye 160). This fixation may occur be when the eye 160 fixates on the fixation target 110. That is, the fixation target 110 is arranged to be viewable by the eye 160 so as to fix the gaze direction 161 of the eye 160 when gazed at by the eye 160, during acquisition of the ORG data 150. However, the fixation target 110 may alternatively be arranged to fix the gaze direction 161 of the eye 160 when the other eye of the subject fixates on the fixation target 110. In the majority of subjects that do not have strabismus or the like, the muscles that control eye movement work together and point both eyes in the same direction so that the fixation of the gaze direction of one of the eyes by the fixation target 110 results in the other eye (even when this other eye cannot see the fixation target 110) having the same gaze direction. For example, where the eye 160 is the right eye of the subject then the gaze direction 161 of the eye 160 may fixed by virtue of the left eye of the subject fixating on the fixation target 110. The position of the fixation target 110 relative to the eye 160 may, as in the present example embodiment, be controllable by the controller 140 so as to control a gaze direction 161 of the eye 160 when the eye 160 fixates on the fixation target 110. However, the position of the fixation target 110 may alternatively be set in a fixed position, relative to the expected position of the eye 160 (i.e. the location where the eye 160 is placed relative to the FD-OCT imaging system 130 for the FD-OCT imaging system 130 to acquire the AS-OCT image) during manufacture or installation/set-up of the FD-OCT imaging system 130. The fixation target 110 may be integrated into the FD-OCT apparatus 100 so as to be viewable by the eye 160 in various ways that are well-known to those skilled in the art or as is described in U.S. Pat. No. 11,253,146 B2, the contents of which are hereby incorporated by reference in their entirety.
Furthermore, the fixation target 110 may be implemented in a form other than a graphic displayed by a display device 200. For example, the fixation target 110 may include a light source (e.g. a light-emitting diode) attached to an actuator that is controllable by the controller 140 to move the light source relative to the eye 160 so as to control a gaze direction 161 of the eye 160 when the eye 160 fixates on the light source.
The optical system 120 is operable to apply the optical stimulus to the retina of the eye 160 such that the illumination of the retina by the optical stimulus is confined to (and may span or fill) a portion of the retina, the optical system 120 being controllable, while the gaze direction of the eye 160 remains fixed by the fixation target 110, to vary a location on the retina of the eye 160 at which the optical stimulus is to be applied. In other words, the optical system 120 is controllable to apply the optical stimulus to each of a plurality of different portions of the retina of the eye 160 whereby, when the optical stimulus is applied to a portion of the plurality of portions of the retina of the eye 160, the optical stimulus is not applied to any of the other portions of the plurality of portions of the retina. The optical system 120 is controllable to vary the location on the retina at which the optical stimulus is to be applied while a position of the fixation target 110 relative to the eye 160 remains fixed (and the gaze direction 161 of the eye 160 remains fixed on the fixation target 110), as described in more detail below.
The optical stimulus may, as in the present example embodiment, be a flash of light of a predetermined duration which is applied to the retina of the eye 160 along an optical path 121 of the optical system 120. The duration of the flash of light is typically much shorter than the time period within which OCT data is acquired by FD-OCT imaging system 130 for generating the ORG data 150, and may be dependent on the intensity of the stimulus. The duration of the flash may be between 5 ms and 50 ms, for example. The duration of the optical stimulus may be controlled by the controller 140, as described in more detail below.
The FD-OCT imaging system 130 (which may be a phase-stable FD-OCT imaging system) may, as in the present example embodiment, be a point-scan FD-OCT imaging system. However, the FD-OCT imaging system 130 may take other forms, such as a line-scan or full-field FD-OCT imaging system. The FD-OCT imaging system 130 is operable to acquire complex OCT data 135 by imaging a portion of the retina of the eye 160. The OCT data 135 may, as in the present example embodiment, comprise a temporal sequence of OCT images, such as a temporal sequence of A-scans, B-scans or C-scans, for example.
The OCT light source 321 of the FD-OCT imaging system 320 is arranged to generate an OCT beam Lb. The OCT light source 321 may, as in the present example embodiment, comprise an illumination source and an illumination source aperture. In this case, the illumination source is arranged to emit light through the light source aperture to generate the OCT beam Lb, such that the shape and size (e.g. diameter, in case of the light source aperture being circular) of the illumination source aperture defines the cross-sectional shape and size (e.g. diameter) of the OCT beam Lb (i.e. so that these sizes and shapes are the same). The illumination source may, where the FD-OCT imaging system 320 is a swept-source OCT (SS-OCT) imaging system, be a swept illumination source arranged to generate light having a wavelength that is swept over a range of wavelengths during a scan performed by the SS-OCT imaging system or, where the FD-OCT imaging system 320 is a spectral-domain OCT (SD-OCT) imaging system, be a broadband light source which is arranged to generate light simultaneously having a range of wavelengths (i.e. a broad spectral content) during a scan performed by the SD-OCT imaging system. The illumination source may be any known swept or broadband source (as the case may be). For example, the illumination source may comprise a laser or a light emitting diode.
The OCT light source 321 may comprise further components, such as one or more collimating lenses for collimating light from the light source, for example. Further, the OCT light source 321 may alternatively take other forms where the FD-OCT imaging system 320 is a line-field or full-field FD-OCT imaging system as would be readily appreciated by those skilled in the art. For example, where the FD-OCT imaging system 320 is a line-field FD-OCT imaging system, the OCT light source 321 may be arranged to generate a line of light and may comprise a laser and a one or more cylindrical lenses (e.g. combination of a plano-concave lens and a plano-convex lens that are arranged to focus the beam from the laser in respective directions that are orthogonal to one another to form a line of light), although any other kind of spatial light modulator for beam shaping known to those versed in the art may alternatively be employed.
The interferometer 322 is arranged to split the OCT beam Lb from the OCT light source 321 to propagate along a sample arm 324 of the interferometer 322, as sample OCT light Lo, and to propagate along a reference arm 325 of the interferometer 322, as reference OCT light Lr. The interferometer 322 is further arranged to receive light Lc which has been scattered by a portion of the retina of the eye 160 and collected by the scanning system 310, to generate an interference light LI resulting from an interference between the reference OCT light Lr and the collected light Lc, and to output the interference light LI to the detector 323. In other words, the reference OCT light Lr propagating along the reference arm 325 and the collected light Lc which has been scattered by the portion of the retina of the eye 160 and collected by the scanning system 310 during a scan performed by the FD-OCT imaging system 320 are guided to coincide and interfere with one another, and the resulting interference line of light LI is directed to and received by the detector 323.
The interferometer 322 may, as in the present example embodiment, be a Michelson interferometer using a beam-splitter 326 to split the OCT beam Lb to propagate along the sample arm 324 and the reference arm 325 of the interferometer 322, and to interfere the reference OCT light Lr that has been reflected from a reference mirror 327 with the collected light Lc from the scanning system 310. Although a Michelson interferometer has been described, those skilled in the art will appreciate that the interferometer 322 is not so limited and any interferometer suitable for OCT may be used such as, for example, a Mach-Zehnder interferometer. Further, those skilled in the art will appreciate that the interferometer 322 may also be adapted as appropriate where the FD-OCT imaging system 320 is a line-scan or full-field FD-OCT imaging system. For example, where the FD-OCT imaging system 320 is a line-scan FD-OCT imaging system, the interferometer 322 may be a free-space interferometer using at least one beam splitter. Furthermore, the interferometer 322 is not limited to being a free-space interferometer, and may instead be a fibre-based interferometer. In this case, the interferometer may employ a fibre coupler to split the OCT beam Lb to propagate along the sample arm and reference arm of the interferometer 322, and to interfere the reference light Lr and the collected light Lc.
The scanning system 310 is arranged to perform a (e.g. a one- or two-dimensional) point-scan of the sample OCT light Lo across the portion of the retina of the eye 160, and collect light Lc which has been scattered by the portion of the retina of the eye 160 during the point scan. The scanning system 310 is therefore arranged to acquire A-scans at respective scan locations that are distributed (e.g. one- or two-dimensionally) across the portion of the retina of the eye 160, by sequentially illuminating the scan locations with the sample OCT light Lo, one scan location at a time, and collecting at least some of the light Lc scattered by the portion of the retina of the eye 160 at each scan location. By acquiring the successive A-scans, the scanning system 310 is thus able to acquire B-scans and/or C-scans, of the retina of the eye 160.
The sample OCT light Lo enters the scanning system 310 from the interferometer 322 and propagates to the beam splitter 311. The sample OCT light Lo is then reflected, in sequence, by the first scanning element 312, the first curved mirror 313, the second scanning element 314 and the second curved mirror 315, before being incident on the portion of the retina of the eye 160. The light Lc which has been scattered by the portion of the retina of the eye 160 and collected by the scanning system 310 follows the same optical path through the scanning system 310 as the sample OCT light Lo, but in reverse order, and exits the scanning system 310 after having propagated via the beam splitter 311.
The point scan is performed by the scanning system 310 by the first scanning element 312 rotating around the first axis (not shown) to scan the sample OCT light Lo in a first direction, or a direction opposing the first direction, across the portion of the retina of the eye 160, and/or by the second scanning element 314 rotating around the second axis 316 to scan the sample OCT light Lo in a second direction, or in a direction opposing the second direction, across the portion of the retina of the eye 160. The second direction may, as in the present example embodiment, be orthogonal to the first direction. Thus, by rotating the first scanning element 312 and the second scanning element 314, it is possible to steer the sample OCT light Lo to any position on the portion of the retina of the eye 160 that is within the field of view of the FD-OCT apparatus 100. As described above, the rotation of the first scanning element 312 and the second scanning element 314 is coordinated by the controller 140, or by a dedicated scanning system controller (not shown), such that the sample OCT light Lo is scanned across the portion of the retina of the eye 160 in accordance with a predefined scan pattern. The predefined scan pattern may be any suitable scan pattern known to those versed in the art, for example a unidirectional scan (wherein a set of parallel scan lines are followed in a common direction, along which they extend), a circular scan, a serpentine scan or spiral scan, which may either be present, or at manufacture selected by the user of the FD-OCT apparatus 100.
The first curved mirror 313 and the second curved mirror 315 may, as in the present example embodiment, be respective ellipsoidal mirrors each having a first focal point and a conjugate second focal point. The first scanning element 312 is located at the first focal point FP1 of the first curved mirror 313, and the second scanning element 314 is located at the second focal point FP2 of the first curved mirror 313. The second scanning element 314 is also located at the first focal point FP3 of the second curved mirror 315, and the eye 160 is in a vicinity of the second focal point FP4 of the second curved mirror 315. More specifically, the pupil of the eye 160 is located at the second focal point FP4 of the second curved mirror 315 such that the optical path of the scanning system 310 may be steered in two-dimensions across a region of the retina of the eye 160. However, the first curved mirror 313 and the second curved mirror 315 may be any reflective components having an aspherical reflective surface, such as a shape of a conical section like a parabola or hyperboloid, or may, more generally, have a shape described by one or more polynomial functions of two variables. The use of curved mirrors in the scanning system 310 allows the FD-OCT imaging system 130 to function as a wide-field FD-OCT imaging system, or an ultra-widefield (UWF) FD-OCT imaging system, as in described in further detail in WO 2014/53824 A1, the content of which is hereby incorporated by reference in its entirety. However, the scanning system 310 is not so limited.
The first scanning element 312 and the second scanning element 314 may, as in the present example embodiment, each be a galvanometer optical scanner (a “H-galvo” and a “V-galvo”, respectively). However, another type of scanning element could alternatively be used, such as a MEMS scanning mirror or a resonant scanning mirror, for example.
The detector 323 is arranged to detect the interference light LI. That is, the detector 323 is arranged to receive the interference light LI from the interferometer 322 and generate a detection signal Sa based on the received interference line of light LI. The detector 323 generates the detection signal Sa by performing a photoelectric conversion of the interference light Ly that is incident on photodetector elements of the detector 323. The specific form of the detector 323 depends on the form in which the FD-OCT imaging system 320 is implemented. For example, where the FD-OCT imaging system 320 is implemented as an SD-OCT imaging system, the detector 322 comprises a spectrometer, which may have a diffraction grating, Fourier transform lens, and a detector array (or a line scan camera). Where the FD-OCT imaging system 320 is implemented as a SS-OCT imaging system, the light detector 120 may comprise a balanced photodetector set-up comprising two photodetectors (e.g. reverse-biased photodiodes), whose output photocurrents are subtracted from one another, with the subtracted current signal being converted into a voltage detection signal by a transimpedance amplifier. The detection signal Sa may, as in the present example embodiment, then be processed by OCT data processing hardware of the FD-OCT imaging system 320 to generate the OCT data 135. However, the functions of the OCT data processing hardware may alternatively be performed by the controller 140 (i.e. the detection signal Sa may be received and processed by the controller 140 to generate the OCT data 135).
Where the FD-OCT imaging system 320 is line-scan system rather than a point scan system, the OCT light source 321 generates a line of light, as described above. In such a case, the interferometer 322 is instead arranged to split the line of light, rather than the OCT beam Lb, into the sample OCT light as a sample OCT line of light. The scanning system 310 is arranged to perform a line-scan of the sample OCT line of light across the portion of the retina of the eye 160 and collect light Lc which has been scattered by the portion of the retina of the eye 160 during the line scan. Accordingly, the scanning system 310 may further comprise a lens arranged to focus the sample OCT line of light at the first focal point FP1 of the first scanning element 312. The sample OCT line of light is then reflected, in sequence, by the first scanning element 312, the first curved mirror 313, the second scanning element 314 and the second curved mirror 315, before being incident on the portion of the retina of the eye 160, and the light scattered from the portion of the retina of the eye 160 travels back to the detector 323 (i.e. as adapted for a line-scan system) via the scanning system 310, in the same manner described above for the point-scan implementation. The sample OCT line of light may thus be steered, in two dimensions, within the eye by rotating the first scanning element 312 and the second scanning element 314 such that a scan of eye 160 may be performed by the scanning system 310 as coordinated by the controller 140 or the dedicated scanning system controller. However, as a sample OCT line of light is incident on the portion of the retina, the scanning system 310 thus acquires at least one B-scan (e.g. successive B-scans forming a C-scan) of the retina of the eye 160 rather than acquiring at least one A-scan as in the point-scan implementation.
The light source 301 of the optical system 300 is arranged to generate light Ls as the optical stimulus. The light Ls may, as in the present example embodiment, be of one or more wavelengths in the visible spectrum of the human eye, although it may more generally be of any wavelength(s) for stimulating a physiological response of a retina of an eye 160. The light source 301 may be arranged to generate a plurality of lights of different wavelengths, each of which may be used as the optical stimulus as desired, (e.g. by use of broadband spectrum source, which may produce white light, filtered by at least one tuneable or removable spectral filter) although this may alternatively be achieved by the optical system 300 comprising additional light sources arranged to generate light of different wavelengths to that of the light Ls which may be the optical stimulus (these light sources may be combined to a single output of the light source 301 using fibre couplers, wavelength division multiplexing (WDM) fibres, beam splitters or dichroic mirrors).
In addition, the light source 301 may be controllable by the controller 140 to generate the light Ls at a desired light intensity.
The light source 301 may, as in the present example embodiment, comprise an illumination source (e.g. a light-emitting diode) and an illumination source aperture in a similar manner to as described above with the OCT light source 321. The light source 301 may comprise further components, such as one or more collimating lenses for collimating light from the light source, for example. The controller 140 controls the light source 301 of the optical system 300 to generate the light Ls as the optical stimulus, as described below, and may further control the light source 301 to vary the duration of the optical stimulus provided by the light source 301.
The beam splitter 311 may, as in the present example embodiment, be a cube beam splitter. However, it may instead be a dichroic mirror, for example.
The optical system 300 shares the scanning system 310 used by the FD-OCT imaging system 320 to perform the point-scan. This is achieved by using the beam splitter 311 to couple the optical path along which the light Ls travels with the optical path along which the sample OCT light Lo travels through the scanning system 310, although any other suitable arrangement for coupling the two optical paths may be used. The optical path along which the light Ls travels through the scanning system 310 when generated by the light source 301 may be coupled to the optical path along which the sample OCT light Lo travels through the scanning system 310 with the beam splitter 311 such that these optical paths run along a common axis, although the optical paths may alternatively run along axes offset by a predetermined amount (e.g. by adjusting the incident location of one of the optical paths on the beam splitter 311).
The scanning system 310 is thus further arranged to direct the light Ls to the retina of the eye 160. The light Ls enters the scanning system 310 via the beam splitter 311, and is then reflected, in sequence, by the first scanning element 312, the first curved mirror 313, the second scanning element 314 and the second curved mirror 315, before being applied to the retina of the eye 160.
In the same manner as with the sample OCT light Lo, the optical system 300 is controllable to vary a location on the retina of the eye 160 at which the light Ls is to be applied by the first scanning element 312 rotating around the first axis (not shown) to move the optical path of the scanning system 310 in the first direction, or in the direction opposite the first direction, across the retina of the eye 160, and by the second scanning element 314 rotating around the second axis 316 to move the optical path of the scanning system 310 in the second direction, or in the direction opposite the second direction, across the retina of the eye 160. By rotating the first scanning element 312 and the second scanning element 314, it is thus possible to steer, in two-dimensions, the optical path along which the light Ls travels such that the light Ls may be applied to any position on the retina of the eye 160. Accordingly, by controlling the timing and the duration of the light Ls generated by the light source 301, and the ranges and rates of rotation of the first scanning element 312 and/or the second scanning element 314, the controller 140 can cause any position on the retina of the eye 160 to be stimulated by the light Ls for a required duration of time. This duration of time may be controlled by the controller 140 along with the intensity of the light Ls generated by the light source 301 so as to obtain a predetermined degree of bleaching of the retina of the eye 160. For example, the degree of bleaching obtained may be between 10% and 66%. Higher bleaching values may be preferable for studying the alpha wave in the ORG data 150 (i.e. the fast retina response).
By the optical system 300 sharing the scanning system 310 with the FD-OCT imaging system 320, the full field of view of the FD-OCT imaging system 320 may be accessed by the optical system 300 without any additional scanning hardware. This reduces the complexity of the FD-OCT apparatus 100 and may allow easier integration of the optical system 300 into complex sample arms, for example where the FD-OCT imaging system 320 is a UWF FD-OCT imaging system, as described above.
As the third scanning element 343 used by the scanning system 342 to direct the light Ls to the retina of the eye 160 is different to the first scanning element 312, it may be independently controlled by the controller 140. Accordingly, the optical path along which the light Ls travels through the scanning system 310 when generated by the light source 301 can be varied in the first direction (or in the direction opposite the first direction) independently of the optical path along which the sample OCT light Lo travels through the scanning system 310. Thus, the optical path along which the light Ls travels through the scanning system 310 is coupled to the optical path along which the sample OCT light Lo travels through the scanning system 310 in one dimension only, which adds an additional degree of freedom to the variation of the optical stimulus on the retina of the eye 160 as compared to the implementations of
Although the example embodiment of
The scanning system 362 may further comprise a beam splitter 366, and the fixation target 335 as described above in relation to
The third scanning element 363 and the fourth scanning element 364 used by the scanning system 362 to direct the light Ls to the retina of the eye 160 are different to the first scanning element 312 and the second scanning element 314 that are used by the scanning system 362 to direct the sample OCT light Lo to the retina, and scanning elements 363 and 364 may be controlled by the controller 140 independently of scanning elements 312 and 314. Accordingly, the optical path, along which the light Ls travels through the scanning system 362 when generated by the light source 301 can be varied in the first direction (or in the direction opposite the first direction), and in the second direction (or in the direction opposite the second direction), independently of the optical path along which the sample OCT light Lo travels through the scanning system 362. Thus, the optical path along which the light Ls travels through the scanning system 362 is not coupled to the optical path along which the sample OCT light Lo travels through the scanning system 362, allowing the variation of the optical stimulus on the retina of the eye 160 to be independently controlled with two degrees of freedom, although at the expense of increasing the complexity of the FD-OCT apparatus 100 as compared to the implementations described above with reference to
Although the scanning system 362 comprises a third scanning element 363 and a fourth scanning element 364, these may alternatively be replaced by a single two-dimensional scanner (e.g. a micro-electromechanical system (MEMS) scanner).
The scanning system 372 may further comprise a beam splitter 366, and the fixation target 335 as described above in relation to
As a further alternative implementation of the example embodiment, the optical system 120 may comprise a spatial light modulator, which is controllable by the controller 140 to vary a location on the retina at which the light Ls is to be applied. For example, the spatial light modulator may comprise a projector having the light source 301, a collimator and a dynamic amplitude mask (e.g. in the form of a digital micromirror device (DMD), which is arranged to be illuminated by the collimated light and is controllable by the controller 140 to allow the collimated light Ls generated by the light source 301 to pass via only a predefined portion of the dynamic amplitude mask so as to vary the location on the retina where light from the light source 301 is incident. Where the dynamic amplitude mask is provided in the form of a DMD, the DMD may comprise an array of rotatable micromirrors, which are individually controllable by the controller 140 to switch from being in one of a first and a second, different orientation to the other of the first and second orientation. More specifically, the DMD may be configured to set each micromirror in the DMD either to a first orientation, to reflect light from the light source 301 towards the eye 160, or to a second orientation such as to reflect incident light away from the eye 160 and thus prevent light from the light source 301 from reaching the eye 160. In this manner, the use of DMD allows binary amplitude modulation of the light received at each micromirror position on the DMD. It should be noted, however, that the functionality of the dynamic amplitude mask may be provided by any suitable type of spatial light modulator other than a DMD, such an array of liquid crystal cells, or an analog micromirror array, for example. For example, in an alternative example embodiment, where the dynamic amplitude mask comprises an array of liquid crystal cells, the liquid crystal in each liquid crystal cell of the array may be individually switchable between a first liquid crystal phase and a second liquid crystal phase. A liquid crystal cell that is in the first liquid crystal phase transmits light Ls incident thereon towards the eye 160. A liquid crystal cell that is in the second liquid crystal phase, on the other hand, blocks incident light Ls, preventing it from being transmitted to the eye 160. Furthermore, the unmasked portion of the dynamic amplitude mask may consist of liquid crystal cells of the array having liquid crystals in the first phase, while the masked portion of the dynamic amplitude mask may comprise liquid crystal cells of the array having liquid crystals in the second phase. The spatial light modulator may, as a further example, comprise an array of light sources (e.g. LEDs) that are arranged to provide corresponding collimated, spatially separated beams of light, and which are controllable by the controller 140 so as to provide control of the location(s) on the retina at which the optical stimulus is applied.
In addition, the spatial light modulator may be used to vary the location on the retina of the eye 160 at which the light Ls is to be applied when the FD-OCT imaging system 130 is a full-field FD-OCT imaging system, by way of example.
It should be noted that, although the above-described arrangements for varying the location on the retina at which the optical stimulus is to be applied are described within the context of an FD-OCT imaging system 130 which is arranged to deliver a single sample OCT beam Lo to the retina of the eye 160, the present disclosure is not so limited, and these arrangements for varying the location on the retina at which the optical stimulus is to be applied may also be used within multi-beam FD-OCT imaging systems that are arranged to simultaneously deliver multiple sample OCT beams to the retina.
The above-described arrangements may allow the location on the retina at which the optical stimulus is applied to be set with greater accuracy than in a case where this location is set by eye steering, e.g. by the fixation target 110 being moved laterally relative to the eye 160 (i.e. in the field of view of the eye 160) to vary the location on the retina at which the optical stimulus is applied. In addition, keeping the fixation target 110 at a fixed location during the acquisition of the ORG data 150 may improve patient comfort and improve the ease of use of the system. Further, some of the above-described arrangements for varying the location on the retina at which the optical stimulus is to be applied make use of the existing optics of the OCT sample arm, thus enabling easier integration of the optical system 120 into existing OCT systems.
Returning to
The controller 140 (and the dedicated scanning system controller, where provided) may be provided in any suitable form, for example as a programmable signal processing hardware 400 of the kind illustrated schematically in
It should be noted, however, that the controller 140 may alternatively be implemented in non-programmable hardware, such as an ASIC, an FPGA or other integrated circuit dedicated to performing the functions of the controller 140 described above, or a combination of such non-programmable hardware and programmable hardware as described above with reference to
The map display device 142 may, as in the present example embodiment, be arranged to receive data from the controller 140 for displaying to the user (e.g. a clinician), for example, and the communication interface 410 may be arranged to receive inputs from the user of the FD-OCT apparatus 100 such as those as required by the controller 140. For example, the map display device 142 may receive and display the ORG data 150, or a graphical representation thereof, or may be controlled by the controller 140 to display the maps described herein below. The inputs from the user of the FD-OCT apparatus 100 may include, for example, the indicator 141, or an indication of the second portion of the retina as will be later described, which the map display device 142 may transmit to the controller 140. The map display device 142 may be an LCD screen, for example, and may comprise programmable signal processing hardware 400 of the kind illustrated schematically in
In process S51 of
In process S52 of
In the present example embodiment, as shown in
In process S53 of
The acquisition of the OCT data 135 may, as in the present example embodiment, be of a temporal sequence of OCT images of the second portion of the retina of the eye 160 within a first period of time (i.e. a period of time between the time of acquisition of the first OCT image in the temporal sequence of OCT images and the time of acquisition of the last OCT image in the temporal sequence of OCT images). Accordingly, in the present example embodiment as shown in
At least a part of the second portion of the retina of the eye 160 is disposed in relation to the first portion so as to be stimulated (or at least partially illuminated) by the applied optical stimulus during acquisition of at least some of the OCT data 135. That is, during the performance of process S53 for a second portion of the retina, the controller 140 previously performs process S52 and uses the acquired indicator 141 to control the optical system 120 to apply the optical stimulus to the corresponding first portion of the retina of the eye 160 at a first time which falls within the first period of time so that at least some of the OCT images in the temporal sequence of OCT images are acquired after the first time, and at least a part of the second portion of the retina of the eye 160 in each of these OCT images is stimulated (or at least partially illuminated) by the applied optical stimulus. The second portion of the retina may at least partially overlap the corresponding first portion of the retina, or it may alternatively be disposed away from but sufficiently close to the corresponding first portion for the light incident on the first portion to scatter into at least some of the second portion or otherwise cause at least a part of the second portion of the retina to be provided with an optical stimulus for stimulating the region of the retina therein. Examples of the location of second portions of the retina of the eye 160 relative to corresponding first portions of the retina of the eye 160 are described in more detail below.
In a variant of the example embodiment, the controller 140 may first acquire an indication of the location of the second portion of the retina, as described above, at which the OCT data 135 is to be acquired, and may subsequently generate the indicator 141 such that the first portion of the retina, which is at the target location, stimulates at least a part of the second portion of the retina (i.e. such that the ORG data 150 may be generated at the location of the second portion of the retina). For example, the location of first portion may be selected to lie along a predetermined scan pattern which is used to acquire the OCT data 135. Accordingly, the same rotation of one or both of the first scanning element 312 and the second scanning element 314 in
Referring again to
The controller 140 may generate the ORG data 150 based on the acquired OCT data 135 using any of the techniques known to those skilled in the art, for example, the velocity-based ORG technique described in Kari V. Vienola, et al., “Velocity-based optoretinography for clinical applications,” Optica 9, 1100-1108 (2022), the content of which is herein incorporated by reference in its entirety. In brief, this velocity-based ORG technique generates ORG data based on acquired OCT data (which, in this case, comprises a temporal sequence of B-scans) by firstly flattening each of the B-scans such that the photoreceptor inner and outer segment (IS/OS) and cone outer segment (COST) reflections lie at the same height for each A-scan in each respective B-scans. Then, a moving (e.g. 10 ms) time window is used to select a group of (e.g. five) sequential B-scans with motion corrected relative to the first B-scan in the series. The phase data cube of each complex data cube for each spatial coordinate pair in the volume is then unwrapped in the temporal dimension to minimise the magnitude of the difference in phase between data cubes of consecutive phase B-scans. After unwrapping, a rate of phase change is calculated for each coordinate pair by using a least-squares linear fit with respect to time to calculate the instantaneous velocity for each spatial location. These instantaneous velocities and the B-scan amplitude, if desired, are averaged in the lateral dimension to give instantaneous, depth-dependent measures of velocity and backscattering, respectively. By shifting the (10 ms) time window a time series of depth profiles is constructed, separately for velocity and reflectively. Both of these may be visualised in time-depth coordinates, as M-scans. The velocities of the IS/OS and COST layers are subsequently extracted and the difference between them is the rate of the contraction/elongation of the OS in the region as a function of time, which may form the ORG data 150 (or, alternatively, the OS length response may be the ORG data 150). However, these techniques may be applied to other retinal layers such as, for example, the rod photoreceptors by extracting the velocities of the IS/OS and ROST layers. Alternatively, the magnitude of the so-called “alpha wave” (i.e. the fast retinal response, which is typically on a timescale of a few milliseconds) in the data of the rate of contraction/elongation of the outer segment (OS) as a function of time may be determined and saved as (or as a part of) the ORG data 150. Additionally or alternatively, the magnitude of the so-called “beta wave” (i.e. the slow response, which is typically on a timescale of a few seconds) may be determined and saved as (or as a part of) the ORG data 150. As a further alternative, the ORG data 150 may comprise a value (e.g. on a predefined scale, for example a scale of 1 to 10) which is indicative of a quality of a retinal response at the location of the second portion of the retina which is generated by comparing the retinal response indicated by the acquired ORG data with the response of a healthy retina. The healthy retinal response may be obtained from ORG data at a location on the retina of the eye 160 which is assessed by a clinician to be healthy or may be obtained from ORG data of a sample healthy eye, for example.
The controller 140 may generate the ORG data 150 based on the acquired OCT data 135 using intensity-based ORG techniques such as, for example, the OCT brightness change and OCT band analysis techniques described in Kim T-H, Ma G, Son T and Yao X, “Functional Optical Coherence Tomography for Intrinsic Signal Optoretinography: Recent Developments and Deployment Challenges”, Front. Med. 9:864824, (2022), the contents of which are incorporated by reference herein in their entirety. OCT brightness change techniques may be used to detect local variations in pixel intensity value caused by the light stimulus on the retina. The data processing technique used in OCT brightness change analysis techniques may comprise registering raw OCT B-scans to account for eye movements, normalizing the pixel intensities based on the inner retinal intensity to limit the effect of pupillary response, identifying “active” intrinsic optical signal (IOS) pixels (i.e. pixels exhibiting a significant change in intensity after the light stimulus, which can be positive where intensity increased or negative where intensity decreased) and quantifying the number of these active IOS pixels for analysis. OCT band analysis techniques may include, for example, deconvolution methods for band analysis (e.g. of the hyper- and hypo-reflective bands in the retina). Where intensity-based ORG techniques are used, the OCT data may be acquired by OCT imaging systems which are not phase stable.
In particular, where the optical system 300 shares the scanning system 310 with the FD-OCT imaging system 320, the radius of the light beam (as the light Ls generated by the light source 301) may be set such that the light beam illuminates the whole of the second portion of the eye 160 while the light beam is at each scan location within the second portion of the eye 160. For example, where the second portion is a straight portion corresponding to a straight B-scan, the radius of the light beam may be set so as to illuminate the whole straight portion when the light beam is at the first scan location (corresponding to the first A-scan of the straight B-scan) and at each subsequent scan location. This arrangement prevents the ‘flickering’ which may be perceived by a part of the retina due to the alternate illumination and lack thereof of the part of the retina by the light beam as it moves between scan locations, which may improve the quality of the generated ORG data.
Although the respective first portions and the respective second portions in
Further, although the respective first portions are shown to be larger than the respective second portions in
Rather than acquiring a single indicator 141 of a single target location and corresponding OCT data 135 acquired for that target location, the controller 140 may alternatively acquire a plurality of indicators each indicative of a respective target location on the retina, and process respective OCT data of respective second portions of the retina corresponding to respective first portions of the retina at each of the target locations to generate respective ORG data during the ORG capture session.
In process S71 of
In process S72 of
In process S73 of
In process S74 of
It is noted that the controller 140 may, as in the present example embodiment, first acquire a first indicator of the plurality of indicators 141 and use this to acquire first OCT data corresponding to the first indicator. The controller 140 may then repeat this OCT data acquisition process (workflow) using each of the remaining indicators of the plurality of indicators 141 until respective OCT data has been acquired for each of the remaining indicators 141. The controller 140 may then process the respective OCT data to generate the respective ORG data in process S74 of
The controller 140 may perform processes S72 and S73 of
It is noted that the controller 140 may first acquire respective second indicators of the plurality of second portions of the retina at which the respective OCT data is to be acquired, and may then generate the plurality of indicators 141 such that each first portion of the retina, whose location on the retina is indicated by the respective one of the indicators 141, stimulates at least a part of a respective second portion of the retina (i.e. such that respective ORG data may be generated based on respective OCT data at the respective second portion of the retina) when the optical stimulus is applied to the first portion of the retina.
In some cases, the controller 140 may advantageously split the processing of the OCT data, to generate the ORG data 150, into smaller steps.
The controller 140 of FD-OCT apparatus 100 may, as in the present example embodiment, be used to store, for each second portion of the second portions of the retina of the eye 160 described with reference to
The data items that are stored in association with one another by the controller 140 as described above may be generated in different ways. For example (as discussed in more detail below, with reference to
Alternatively, the locations of points on the retina that are to be stimulated by the optical system 120 and have OCT data acquired therefrom by the FD-OCT imaging system 130 may be selected by the controller 140 based on an image of the retina of the eye 160, so that the ORG data 150 that is ultimately generated by the controller 140 is derived from one or more regions of the retina that are of interest to study. The ORG data 150 generated in this way may similarly be compared with measurements that have been (or will be) acquired in a visual field test, by mapping positions on the retina associated with items of the OCT/ORG data to conjugate positions in the visual field of the eye 160. Although the items of ORG data 150 and the measurements in the visual field test may not have been acquired at respective sets of points that are optically conjugate in this case, a meaningful comparison may nevertheless be made. This alternative is described in more detail below, with reference to
In process S1101 of
In process S1102 of
The position of the second portion of the retina may include a representative location of the second portion of the retina (for example, a point (e.g. a central point) along a scan line on the retina along which repeat B-scans are taken as the OCT data 135). Thus, the position of the second portion may be that of a point, defined in cartesian coordinates (xx, yn, zn) or in any other coordinate system, relative to a reference location (e.g. a point on the retina at which the optical axis or visual axis of the eye 160 passes, or the location of an anatomical feature on the retina, such as the fovea or the optic disc). The corresponding position in the visual field of the eye 160 that is optically conjugate with a position of a second portion of the retina may be a point whose location may, for example, be defined in terms of a first angle α from the visual axis of the eye 160 which is in the temporal-nasal direction of the eye 160, and a second angle β from the visual axis of the eye 160 which is in the superior-inferior direction of the eye 160, or in any other suitable coordinate system.
In process S1201 of
In process S1202 of
In process S1203 of
The stored respective ORG data and associated respective indications of positions in the visual field of the eye 160 may be used to compliment a visual field test of the eye 160 in providing further information that may be helpful in determining the cause of any blind spots or reduced retinal sensitivity within the visual field of the eye 160.
In process S1401 of
Referring to
In process S1502 of
In process S1503 of
The controller 140 may alternatively acquire the aforementioned data (indicating how measurements of the subject's ability to see optical stimuli that are confined to respective different portions of the retina of the eye 160 at different respective locations on the retina are distributed over at least a part of a visual field of the eye 160) by receiving visual field test data which has been acquired from the eye 160 (e.g. by a kinetic or static perimetry device). For example, the visual field test data may be acquired from the eye 160 by performing a visual field test on the eye 160 using a visual field-testing device such as, for example, an Octopus™ visual field test device or a Humphrey™ Field Analyzer (HFA). The visual field test data may more generally be acquired via forms of perimetry including, for example, the use of a tangent screen, the use of a Goldmann perimeter, automated perimetry and microperimetry (which is described in more detail below). Further, the form of perimetry may use either a static or kinetic presentation of the visual field test stimulus so as to perform a static perimetry test or a kinetic perimetry test, for example, and the visual field test stimulus used may be selected so as to perform a photoreceptor specific perimetry test, such as a photopic perimetry test or a scotopic perimetry test, for example.
The visual field test data acquired from the eye 160 may comprise values indicative of the subject's ability to see optical stimuli in the visual field of the eye 160 presented at each of a plurality of different locations in the visual field of the eye 160. For example, where the visual field test data is acquired from the eye 160 by performing a visual field test on the eye 160 using the HFA, the values may be indicative of the patient's retinal sensitivity (e.g. in dB) in a numerical display output from the FHA or may be the greyscale values in a greyscale plot output from the HFA. More generally, the values may be binary (e.g. a “1” or a “0”), dependent upon whether the subject indicated that they saw the optical stimuli or may be indicative of a threshold light intensity at which the subject indicated that they could see the optical stimuli a certain proportion (e.g. 50%) of the time. The locations in the visual field of the eye 160 may be defined a coordinate system similar to those described in relation to process S1101 of
Referring again to
Referring again to
For comparison purposes, the locations in the visual field of the eye 160 at which the stored ORG data 150 are displayed on the second map of process S1403 of
In optional process S1404 of
In the present example embodiment, the one or more first regions (i.e. different first regions) of the displayed visual field indicate that the subject is able to see optical stimuli in the one or more first regions, and further indicate that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which satisfies the predetermined condition. These one or more first regions can thus be taken to correspond to regions of the retina that have a healthy (normal) functioning.
The one or more second regions (i.e. different second regions) of the displayed visual field indicate that the subject has an inability to see optical stimuli in the one or more second regions, and further indicate that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which satisfies the predetermined condition. These one or more second regions can thus be taken to correspond to regions of the retina where, despite the retina responding to the optical stimulus normally, the subject could not see the applied stimuli (although this does not rule out that the subject might have been able to see stimuli of higher intensity, had these been applied in the visual field test). This indicates to a clinician that the cause of the subject's inability to see is unlikely to be malfunctioning retinal photoreceptors but may originate elsewhere, for example in the communication pathway between the retinal photoreceptors and the brain of the subject, for example. This may guide the clinician to reach the correct diagnosis more quickly.
The one or more third regions (i.e. different third regions) of the displayed visual field indicate that the subject can see optical stimuli in the one or more third regions, and further indicate that one or more corresponding regions of the retina provided a response to the optical stimulus which does not satisfy the predetermined condition. These one or more third regions can thus be associated with the subject having falsely indicated they could see optical stimuli. Such regions may be investigated again with a further visual field test or excluded from (or weighted with reduced confidence in) the analysis of the function of the retina, thus further improving the accuracy of any diagnosis made by the clinician.
The one or more fourth regions (i.e. different fourth regions) of the displayed visual field indicate that the subject has an inability to see optical stimuli in the one or more fourth regions, and further indicate that one or more corresponding regions of the retina provided a physiological response to the optical stimulus which does not satisfy the predetermined condition. These one or more fourth regions thus correspond to one or more regions of retina that are not functioning healthily, the identification of which may save the clinician time when performing their analysis of retinal function of the eye 160 by focusing their attention initially on these regions.
Optionally, in process S1405 of
Although the display of the first map indicative of the subject's ability to see optical stimuli as distributed over at least a part of a visual field of the eye 160 and of the second map indicative of the physiological response of the retina to optical stimuli indicated by the stored respective indications as distributed over the at least a part of the visual field of the eye 160 has been described above, the controller 140 may, in an alternative implementation of the example embodiment, control the map display device 142 to display a fourth map indicative of the subject's ability to see optical stimuli with the eye 160 as distributed over at least a part of the retina of the eye 160, and a fifth map indicative of the physiological response of the retina to the optical stimulus indicated by at least some of the stored ORG data as distributed over the at least a part of the retina of the eye 160. This may be preferable to the clinician as it allows a comparison of the visual field test data and ORG data when overlaid on an image of the retina of the eye 160 to be made, so to enable the two sets of data to be used to interpret structural features of the eye 160 in the image, for example. In particular, the fourth map may be that obtained from a microperimetry test of the eye 160, allowing the respective ORG data to be mapped to, and displayed alongside, microperimetry results acquired by the controller 140, as described below.
In process S2101 of
In process S2102 of
Referring to
In process S1902 of
As an alternative to processes S1901 and S1902, the controller 140 may receive visual field test data acquired from the eye 160 by a visual field-testing device, the visual field test data indicating how measurements of the subject's ability to see optical stimuli applied to respective different locations on the retina of the eye 160 are distributed over at least a part of the retina of the eye 160. For example, the visual field test data may be acquired from a microperimetry device (e.g. Nidek™ MP-3 microperimeter, the Zeiss Humphrey™ Field Analyzer Model 860 or the Haag-Streit Octopus 900 Pro™), the output of which also includes, as the distribution information, indications of the locations on the retina of the eye 160 (for example, in the form of coordinates of points on an image of the retina acquired by the microperimetry device) to which the optical stimuli from the microperimetry device were delivered.
In process S1903 of
In process S1904 of
Returning to
In optional process S2104 of
The fourth map and the fifth map may be superimposed in the same manner described above with respect to the first map and second map Further, the controller 140 may identify one or more first regions, one or more second regions, one or more third regions, and one or more fourth regions as distributed over at least a part of the retina of the eye 160 by comparing the fourth map and the fifth map in the same manner to as described above with respect to the first map and the second map. In addition, these identified regions may be displayed by the map display device 142 in at least one of the fourth map, the fifth map and a sixth map indicative of the at least a part of the retina of the eye 160 in the same manner as described above for the first map, second map and the third map. Note that the controller 140 may perform the above-described processes to control the map display device 142 to display at least one of the fourth map, the fifth map and the sixth map in addition to at least one of the first map, the second map and the third map.
Although the FD-OCT apparatus 100 of the example embodiment described above comprises a steerable optical system 120, which is controllable by the controller 140 to vary a location on the retina at which the optical stimulus is to be applied whilst a fixed gaze direction of the eye is maintained by the fixation target 110 (by virtue of the position of the fixation target 110 relative to the eye 160 remaining fixed), and which applies a localised stimulus that is confined to a portion of the retina, the forms of the fixation target and of the optical system for providing the optical stimulus are not so limited. For example, in some example embodiments, particularly where relatively small amounts of ORG data are being acquired in each imaging session, the fixation target may be dispensed with altogether, and the subject may be asked to maintain a central gaze direction during the session. In other example embodiments, the optical system which provides the localised optical stimulus may not be steerable, and the location on the retina at which the optical stimulus is to be applied may be adjusted by instead varying the position of a fixation target relative to the eye 160, so as to perform eye-steering. In other example embodiments, a conventional optical system, which provides flood (widefield) illumination of the retina instead of a localised optical stimulus, may be employed. However, where such a conventional optical system is being used, the acquisition of OCT data 135 from a plurality of portions of the retina would generally necessitate the use of a light adaptation period between the acquisition of OCT data at each portion (since all portions intended for imaging would typically be illuminated by the optical system), which would slow down the generation of the ORG data 150 by the FD-OCT apparatus and may degrade its quality owing to movements of the subject caused by the more prolonged imaging procedure and associated likely increased degree of discomfort in interfacing with the FD-OCT apparatus 100.
In alternative example embodiments of the kinds set out above, the controller 140 may be generally arranged to: (i) control the FD-OCT imaging system 130 to acquire OCT data 135 of a plurality of portions of the retina such that, for each portion of the plurality of portions of the retina, at least some of the OCT data acquired from the portion is acquired after a respective optical stimulus has been applied to the portion by the optical system 120; (ii) generate, based on the acquired OCT data 135, respective ORG data 150 for each portion of the plurality of portions of the retina which is indicative of the respective response of the portion of the retina to the optical stimulus applied to the portion of the retina; and (iii) store, for each portion of the plurality of portions of the retina, the respective ORG data 150 generated for the portion in association with a respective indication of a position in a visual field of the eye 160 of a point that is optically conjugate with a corresponding position of the portion on the retina.
Furthermore, in such alternative example embodiments, the controller 140 may perform a method of controlling a FD-OCT apparatus to acquire ORG data 150 that is indicative of a physiological response of the retina of the eye 160 to an optical stimulus, as will now be described with reference to
In process S3101 of
In process S3102 of
In process S3103 of
Alternatively, the controller 140 may perform a method of controlling a FD-OCT apparatus to acquire ORG data 150 that is indicative of a physiological response of the retina of the eye 160 to an optical stimulus, as will now be described with reference to
In process S4101 of
In process S4102 of
In process S4103 of
In process S4104 of
The controller 140 may then control the display device 142, based on at least some of the data acquired in process S4104 of
The methods described above with reference to
In the foregoing description, example aspects are described with reference to several example embodiments. Accordingly, the specification should be regarded as illustrative, rather than restrictive. Similarly, the figures illustrated in the drawings, which highlight the functionality and advantages of the example embodiments, are presented for example purposes only. The architecture of the example embodiments is sufficiently flexible and configurable, such that it may be utilized in ways other than those shown in the accompanying figures.
Some aspects of the examples presented herein, such as functions of the controller 140, may be provided as a computer program, or software, such as one or more programs having instructions or sequences of instructions, included or stored in an article of manufacture such as a machine-accessible or machine-readable medium, an instruction store, or computer-readable storage device, each of which can be non-transitory, in one example embodiment. The program or instructions on 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. The machine- or computer-readable medium, instruction store, and storage device may include, but are not limited to, floppy diskettes, optical disks, and magneto-optical disks or other types of media/machine-readable medium/instruction store/storage device 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. The terms “computer-readable”, “machine-accessible medium”, “machine-readable medium”, “instruction store”, and “computer-readable storage device” used herein shall include any medium that is capable of storing, encoding, or transmitting instructions or a sequence of instructions for execution by the machine, computer, or computer processor and that causes the machine/computer/computer processor to perform any one of the methods described herein. Furthermore, it is common in the art to speak of software, in one form or another (e.g., program, procedure, process, application, module, unit, logic, and so on), as taking an action or causing a result. Such expressions are merely a shorthand way of stating that the execution of the software by a processing system causes the processor to perform an action to produce a result.
Some or all of the functionality of the controller 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.
A computer program product may be provided in the form of a storage medium or media, instruction store(s), or storage device(s), having instructions stored thereon or therein which can be used to control, or cause, a computer or computer processor to perform any of the procedures of the example embodiments described herein. The storage medium/instruction store/storage device may include, by example and without limitation, an optical disc, a ROM, a RAM, an EPROM, an EEPROM, a DRAM, a VRAM, a flash memory, a flash card, a magnetic card, an optical card, nanosystems, a molecular memory integrated circuit, a RAID, remote data storage/archive/warehousing, and/or any other type of device suitable for storing instructions and/or data.
Stored on any one of the computer-readable medium or media, instruction store(s), or storage device(s), some implementations include software for controlling both the hardware of the system and for enabling the system or microprocessor to interact with a human user or other mechanism utilizing the results of the example embodiments described herein. Such software may include without limitation device drivers, operating systems, and user applications. Ultimately, such computer-readable media or storage device(s) further include software for performing example aspects of the invention, as described above.
Included in the programming and/or software of the system are software modules for implementing the procedures described herein. In some example embodiments herein, a module includes software, although in other example embodiments herein, a module includes hardware, or a combination of hardware and software.
While various example embodiments of the present invention have been described above, it should be understood that they have been presented by way of example, and not limitation. It will be apparent to persons skilled in the relevant art(s) that various changes in form and detail can be made therein. Thus, the present invention should not be limited by any of the above-described example embodiments, but should be defined only in accordance with the following claims and their equivalents. It is also to be understood that any procedures recited in the claims need not be performed in the order presented.
While this specification contains many specific embodiment details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular embodiments described herein. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.
In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.
Having now described some illustrative embodiments and embodiments, it is apparent that the foregoing is illustrative and not limiting, having been presented by way of example. In particular, although many of the examples presented herein involve specific combinations of apparatus or software elements, those elements may be combined in other ways to accomplish the same objectives. Acts, elements and features discussed only in connection with one embodiment are not intended to be excluded from a similar role in other embodiments or embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23 197 119.3 | Sep 2023 | EP | regional |
