System for determining the spatial arrangement of an optical instrument

Abstract

System (100) for determining a spatial arrangement of an optical instrument (40), comprising: a control unit (20) which is configured to to receive a time-resolved OCT signal (19) of a sample (50) from an OCT system (10); to determine a relative arrangement between the optical instrument (40) and at least one element (52) of the sample (50) based on the OCT signal (19), wherein the relative arrangement comprises a lateral arrangement between a vertex (42) of the optical instrument (40) and a vertex (53) of the at least one element (52) of the sample (50) and / or a distance between the optical instrument (40) and the at least one element (52) of the sample (50); and to determine an output based on the determined relative arrangement.

Description

Subject matter of the invention

[0001] The present invention relates to a system for determining and preferably adapting a spatial arrangement of an optical instrument by determining a relative arrangement between an optical instrument and at least one element of a sample. The present invention further relates to a method for determining and preferably adapting a spatial arrangement of the optical instrument. Technological background

[0002] The use of technological aids is an integral part of modern medicine. Imaging techniques and robotic systems are now used as routinely in surgery as in diagnostics. The use of imaging techniques allows for the visualization and differentiation of diverse structures within the patient, and the image data obtained from the patient can be advantageously used in diagnostics as well as in therapeutic and surgical procedures.

[0003] For example, a surgeon can use patient image data to better plan a surgical procedure and also receive support during the procedure itself. Robotic visualization systems are used to support surgeons during surgical procedures. These systems typically have at least one camera for capturing images of the area to be operated on, which is supported by a tripod with an articulated structure. The tripod allows the camera to be positioned relative to the patient through translational and / or rotational movements in order to capture images of a desired field of view (FOV) of the area to be operated on. The use of optical stereo cameras enables the acquisition of 3D image data.In addition to acquiring surface information within a desired field of view, for example, using reflected or backscattered visible light, methods now exist for acquiring depth information within that field. These methods include optical coherence tomography (OCT), which allows for the three-dimensional microscopic imaging of optically transparent and / or reflective objects, thus enabling the acquisition of volumetric images of biological tissue within the viewed field of view. Optical coherence tomography (OCT) is essentially an interferometric method using broadband light with a short coherence length. Systems for acquiring OCT data therefore typically include an interferometer and a broadband light source with a spectral width greater than 1% of the central wavelength.

[0004] OCT data acquisition can be performed sequentially or in parallel. Sequential acquisition of OCT data is achieved, for example, by splitting a low-coherence source light beam into a sample beam and a reference beam using a beam splitter. These beams are then directed through two arms of an interferometer, with a movable reference mirror in the reference beam path and the object under investigation in the sample beam path. By moving the reference mirror, the path difference between the sample and reference beams, and thus the measured depth, can be adjusted. A mirror in the sample beam path scans the sample beam two-dimensionally, resulting in a three-dimensional scan of the sample.

[0005] In such a time-domain OCT (TD OCT) data acquisition, the spectral width of the light source Δγ corresponds to a coherence length L. C from LC =λ* / Δλ. The axial resolution of an OCT system corresponds to the coherence length L. C The axial resolution of the light used is the resolving power of objects that are separated along the optical axis by at least the coherence length. For example, a near-infrared light source with a central wavelength of 800 nm and a spectral width of 80 nm has a coherence length of 7 µm, and an OCT system with such a source therefore has an axial resolution of approximately 1–10 µm. The transverse resolution of an OCT system is determined by the optics used in the optical path, in particular by the objective lens that focuses the light onto the object being examined.

[0006] Sequential acquisition of OCT data is also possible in the frequency domain (frequency domain OCT - FD OCT), where a distinction is generally made between the use of a tunable source (swept source OCT) and the use of a dispersive detector (spectral domain OCT - SD OCT). In swept source OCT, the frequency of the excitation light source, for example, a laser, is tuned, allowing the path difference between the sample and reference beams, and thus the scanned sample depth, to be varied even without a movable reference mirror. SD OCT also uses a broadband light source, but the frequency components of the interference signal are separated before detection, for example, by an optical grating. OCT enables the acquisition of cross-sectional and volumetric data of biological tissue and can significantly increase the information available to a surgeon.Therefore, the integration of OCT into surgical microscopes is desirable in order to be able to display both video data of the surface of a desired field of view and depth and / or cross-sectional images of the field of view, for example simultaneously and / or superimposed.

[0007] The generation of OCT images from OCT signals is performed computationally, for example, using volume rendering, ray tracing, and / or ray marching. These methods inherently offer more diverse image generation possibilities than the methods or algorithms typically used to generate the (partially three-dimensional) video image data from the image signals acquired by an operating microscope. Therefore, methods for generating OCT images (or for visualizing OCT signals) need to be developed that select from the many available options those that best meet the requirements of medical practice.

[0008] During ophthalmological treatment, imaging of the posterior segment of the eye, or fundus, is often necessary. This is done in a so-called posterior mode, in contrast to imaging the anterior segment of the eye in an anterior mode. When imaging the posterior segment during an ophthalmological or surgical procedure, indirect fundus imaging is typically achieved by positioning an additional optical system below an operating microscope, such as the Zeiss Artevo 800. One such optical system is the Zeiss RESIGHT 700. For indirect fundus imaging, an ophthalmoscopic magnifying lens is suspended a few millimeters (approximately 2-5 mm) above the eye, creating an intermediate image (hence the name "indirect fundus image") which is then displayed to the operator through the operating microscope.

[0009] Correct positioning of the ophthalmic magnifier over the patient's eye is crucial for intraoperative imaging. Incorrect positioning of the magnifier relative to the eye leads to adverse effects on the imaging. Even slight deviations between the eye and the optics or operating microscope can impair indirect fundus imaging. This effect is also known as the "eye-box problem" and can, for example, lead to a partial disappearance of the video image. Positioning the ophthalmic magnifier together with the operating microscope is usually achieved by manually moving the operating microscope. To do this, the operator views the image on the operating microscope while simultaneously adjusting the position of the patient or the operating microscope. This is done in addition to focusing on the fundus, which is performed, for example, using a varioscope (e.g., Zeiss Resight 700).This manual positioning is disadvantageously prone to errors, which can lead to the aforementioned problems (“eye-box problem”).

[0010] US 2016 / 0360959A1 discloses an OCT tracking system. The OCT tracking system comprises an imaging unit for generating a fundus image of a patient's eye and a tracking unit for processing the generated fundus image. The OCT tracking system further comprises an OCT system whose X-ray scanner is communicatively connected to the tracking unit.

[0011] US 8 860 796 B2 discloses an optical OCT imaging system for imaging an eye including a source with an associated source arm and a reference arm with an associated reference arm path having an associated reference arm path length.

[0012] The OCT imaging system includes a module for adjusting the length of the reference arm path.

[0013] The object of the present invention is therefore to provide an improved system and an improved method for determining a spatial arrangement of an optical instrument which overcomes or at least reduces the disadvantages of the prior art and enables improved imaging, in particular for indirect fundus imaging. Description of the invention

[0014] The problem according to the invention is solved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims.

[0015] A first aspect of the present disclosure relates to a system for determining the spatial arrangement of an optical instrument. The system according to the present disclosure includes a control unit configured to receive a time-resolved OCT signal from a sample, preferably from a sample and the optical instrument, from an OCT system. The sample may be, for example, a surgical site of a patient, in particular an eye in ophthalmic surgery. However, the sample may also be any other surgical site, such as brain tissue in neurosurgery, tissue in the ear, nose, and throat region in ENT surgery, or gums, tartar, or dental nerves in dental surgery. Likewise, it may be any other tissue or preparation (in vivo, in vitro, or in situ).The time-resolved OCT signal is preferably acquired by generating a light signal and partially directing it as a sample beam onto the sample using the interferometer, and then superimposing it in the interferometer with a reference beam also generated from the light signal to create an interference pattern.

[0016] The control unit of the system according to the present disclosure is further configured to determine a relative arrangement between the optical instrument and at least one element of the sample based on the OCT signal, wherein the relative arrangement comprises a lateral arrangement between a vertex of the optical instrument and a vertex of the at least one element of the sample and / or a distance between the optical instrument and the at least one element of the sample. The OCT signal comprises section or volume data of biological tissue, which can be represented as depth and / or cross-sectional images and provide depth information about the sample. According to the present disclosure, a relative arrangement and / or relative orientation between the optical instrument and the at least one element of the sample is enabled based on this section or volume data.

[0017] In other words, according to the present disclosure, a positional relationship between the at least one element of the sample and the optical instrument is determined. Accordingly, at least implicitly, a first position of the at least one element of the sample and a second position of the optical instrument are determined and related to each other in order to ascertain the relative arrangement between the two components. The relative arrangement or positional relationship preferably includes a lateral positional relationship, for example, a lateral offset. Furthermore, the positional relationship preferably includes a distance, preferably a distance along an optical axis of the operating microscope, between the at least one element of the sample and the optical instrument.The distance is preferably measured and evaluated between points, lines and / or surfaces defined by the user that correspond to at least one element of the sample or the optical instrument.

[0018] The relative arrangement is determined with or without generating an OCT image. Preferably, the relative arrangement is determined directly from the OCT signal, i.e., from the raw OCT data, as explained in detail below. Alternatively, an OCT image is first generated from the OCT signal, and the relative arrangement is then determined from this image. Image analysis can be performed using known image analysis algorithms. Preferably, this is done using an automated approach based on a trained artificial network and / or based on classical image processing.The algorithms include, for example, edge detection algorithms such as Canny, Sobel, and Roberts, which can be used to detect boundaries between different regions in the image, and / or shape analysis algorithms, such as Fourier descriptors and Hu moments, to quantify one or more geometric properties, such as shape, size, extent, orientation, curvature, and / or symmetry of the sample and / or the optical instrument. The relative arrangement preferably describes the spatial position between the optical instrument and the at least one element of the sample, particularly in a coordinate system of the OCT system and / or in a coordinate system of an operating microscope. The control unit of the system according to the present disclosure is further configured to determine an output based on the determined relative arrangement.This output regarding the relative arrangement of the optical instrument and the specimen is preferably provided directly to a user, thus enabling targeted manual or semi-automated adjustment of the relative position. Equally preferred is the output regarding the relative arrangement being provided internally to a control unit of at least one actuator (the operating microscope and / or the optical instrument) to enable fully automated adjustment of the relative position. Thus, according to the present disclosure, the system advantageously enables an improved relative arrangement of the optical instrument and the specimen, and consequently, improved fundus imaging. By determining the relative arrangement and generating an output based on it, information is provided that enables improved use of the optical instrument and can therefore increase the quality of a treatment or procedure.The system according to the present disclosure preferably comprises a display means configured for the time-resolved display of image data. The display means is preferably one or more screens, for example, at least one screen of an operating microscope, a screen permanently installed in an operating room, or a head-mounted display (HMD), such as video glasses. The screen is preferably a 4K and / or 8K capable screen and / or a 3D screen configured for stereoscopic display. The control unit is preferably connected to the display means, particularly for one-way or two-way data transmission. The control unit of the system according to the present disclosure is preferably configured to determine a time-resolved OCT image with the at least one element of the sample based on the received time-resolved OCT signal.The control unit of the system according to the present disclosure is further preferably configured to display the acquired time-resolved OCT image on the display medium. In other words, the control unit is configured to drive the display medium to display the time-resolved OCT image with the at least one element of the sample on the display medium. The display is advantageously performed with the at least one element of the sample.

[0019] The control unit is preferably configured to control an OCT system for acquiring a time-resolved OCT signal of the sample, preferably of a selected region of interest (ROI) of the sample, wherein the region of interest is preferably selected by a user. Furthermore, the system according to the present disclosure preferably includes an OCT system. The OCT system preferably includes a light source, for example a broadband light source, for illuminating the sample. This light source is preferably a sweepable laser, for example a broadband laser, a supercontinuum laser, and / or an ultrashort pulse laser. The sweepable laser can be a narrowband light source at a given time, but its mid-frequency can be selectively varied over time, or it can be composed of a plurality of narrowband light sources.However, other broadband sources can also be used, such as a superluminescent diode, for example in an FD-OCT.

[0020] According to a preferred embodiment, the OCT system employs a swept-source light source. This advantageously provides a degree of freedom of, for example, 30 mm to 40 mm in depth measurement, thus enabling extensive scanning in the depth direction of the optical instrument or the beam path of the OCT system, and preferably the operating microscope. Therefore, a swept-source OCT signal can be advantageously determined that includes both the optical instrument and at least one element of the sample. Thus, the relative arrangement of the optical instrument and the sample can preferably be determined from a single OCT signal. In other words, the time-resolved OCT signal received by the OCT system includes not only the sample but also the optical instrument.

[0021] The OCT system further preferably comprises an interferometer designed for generating and superimposing a sample beam and a reference beam, for example, a Michelson, Mach-Zehnder, or Koster interferometer. The interferometer preferably includes a beam splitter for generating and superimposing the sample and reference beams from the light of the broadband source, a reference beam path, and a sample beam path. The interferometer further preferably includes means for setting a sample depth under investigation. Depending on the measurement method, these means can be a means for generating a path difference (such as a mirror movable in the reference beam in SD-OCT), a means for separating light with a specific path difference (such as an optical grating in FD-OCT), or a means for generating light with a specific path difference (such as a tunable source in swept-source OCT).

[0022] The OCT system further comprises a scanning mechanism designed to scan the sample with the sample beam. The scanning mechanism is specifically designed to scan the sample beam across the sample in two dimensions. Preferably, the scanning mechanism is a scanning mirror; however, other scanning mechanisms, such as a fiber optic scanner, a prism scanner, a Palmer scanner, or the like, can also be used. A scanning mechanism is unnecessary in an OCT system configured for full-field OCT.

[0023] The OCT system also includes a detector designed to detect an interference pattern generated by the superposition of the sample beam and the reference beam. This detector can be, for example, a line detector, a two-dimensional detector array, a photodetector, or a dispersive detector. The detector may be, for example, a CCD or a CMOS detector.

[0024] The OCT signal is preferably an interference signal, where the modulation of the interference signal's envelope encodes the sample's reflection properties. Using the scanning mechanism, the sample can be scanned two-dimensionally at a depth determined by the path difference. The scanning mechanism employed, the means used to select or generate the path difference (e.g., an adjustable mirror in the reference beam, an optical grating in front of the detector, or a tunable broadband light source), and the detector's repetition rate determine the clock frequency (frame rate) of the time-resolved OCT signal.The control unit computationally determines a time-resolved OCT image based on the OCT signal, preferably by means of volume raycasting, volume rendering, ray tracing and / or ray marching, wherein according to the invention a time-resolved OCT image is determined with the at least one object and with the virtual surface, wherein a reflection of the at least one object of the OCT image is determined on the virtual surface.

[0025] The OCT system preferably includes the optical instrument such that both components are fixedly aligned relative to each other, i.e., in a predefined positional relationship. Therefore, the information about the position and orientation of the optical instrument is inherently provided by the position and orientation of the OCT system, enabling the determination of the relative arrangement between the sample element and the optical instrument. Thus, the position of the optical instrument is known via the OCT signal. Consequently, it is advantageously possible to determine the relative arrangement by evaluating an OCT signal that only images the sample and thus contains only information about the sample.

[0026] In a preferred embodiment of the system according to the present disclosure, the optical instrument comprises (or is) a magnifying glass, an ophthalmic magnifying glass, a contact lens, a lens, and / or a vitrectomy lens. By determining the spatial arrangement between the at least one element of the sample and the aforementioned optical instruments, improved alignment and thus improved imaging can be achieved. For example, an ophthalmic magnifying glass serves for indirect fundus imaging, and by determining the relative arrangement, the quality of the indirect fundus imaging can be derived or optimized.

[0027] Preferably, the sample comprises an eye, and the at least one element of the sample comprises a pupil, cornea, and / or retina, preferably at least one surface of the cornea and / or retina. Using these reference points, the relative arrangement between the sample (eye) and the optical instrument can be determined particularly advantageously during ophthalmic treatments. For this purpose, specific geometric properties are advantageously available, such as the shape, size, extent, orientation, curvature, and / or symmetry of both the at least one element (for example, the curved cornea or retina) and the optical instrument. Based on these geometric properties, a positional relationship between an element of the sample, for example, the cornea, and a lower or upper contour of the ophthalmoscopic lens can be advantageously determined.Both surfaces are fundamentally convex, and thus, despite their different radii of curvature, their lateral positional relationship can be determined based on their vertices. The same applies, for example, to the retina and a lower or upper contour of the ophthalmoscopic lens. Contours with opposing curvature can also be positioned relative to each other based on their vertices. Particularly preferably, the sample comprises an eye, and the optical instrument an ophthalmoscopic lens, which is positioned a few millimeters, preferably 2-5 mm, above the eye for indirect fundus imaging.

[0028] In a further preferred embodiment of the system according to the present disclosure, the time-resolved OCT signal includes a cornea scan. Accordingly, the OCT signal contains, among other things, information about the cornea, its arrangement, and its geometric properties. The cornea thus serves as at least one element for determining the relative arrangement to the optical instrument. Even with limited depth of field or limited information relating only to the anterior segment of the eye, this makes it possible to determine the relative arrangement. In a further preferred embodiment of the system according to the present disclosure, the time-resolved OCT signal (alternatively or additionally) includes a retina scan. Accordingly, the OCT signal contains, among other things, information about the retina, its arrangement, and its geometric properties.Modern OCT systems, especially swept-source OCT systems, can provide sufficient depth information to include elements of the fundus for determining their relative arrangement. When performing fundus imaging, the surgeon is interested in cross-sectional images of the retina, so the OCT data must include corresponding retinal information.

[0029] In a preferred embodiment of the method according to the present disclosure, the time-resolved OCT signal comprises data attributable to the optical instrument. Accordingly, the OCT signal is based, among other things, on a light signal backscattered from a surface of the optical instrument. This advantageously enables the determination of geometric properties of the surface of the optical instrument and thus the determination of the spatial orientation of the optical instrument based on the OCT signal. This is preferably done alternatively and / or additionally to determining (deriving) the spatial orientation of the optical instrument based on information about the spatial orientation of the OCT system.

[0030] Preferably, the imaging depth of the OCT signal is greater than the eye length of the sample, and the control unit is configured to determine the eye length of the sample based on the OCT signal and to determine the relative arrangement based on the determined eye length. With such an OCT imaging depth, an area above the cornea can also be imaged. The eye length is typically between 30 mm and 40 mm. Accordingly, the OCT imaging depth preferably encompasses 30 mm to 45 mm. In particular, modern SS-OCT (swept source OCT) systems are characterized by such a high imaging depth (depth of the cross-sectional image). In the region of the anterior segment of the eye, the OCT sample beam is only slightly deflected during a scan of the fundus and is not focused on the cornea.Due to the high sensitivity of modern SS-OCT systems, the surface of the cornea and / or optical instrument can still be advantageously reconstructed from the OCT signal. Since the ophthalmoscopic lens is positioned only a few millimeters above the patient's eye during indirect fundus imaging, the OCT signal also images the cornea and the lower surface of the lens. Preferably, the OCT signal thus encompasses a portion of the cornea of ​​the sample, a portion of the retina of the sample, and / or a portion of the optical instrument. When all these areas are present, the OCT image depth extends over the entire length of the eye and additionally includes a portion of the optical instrument. Based on this data, the relative arrangement can be determined with particular accuracy and reliability.In a particularly preferred embodiment of the system according to the present disclosure, the control unit is further configured to determine a positioning target based on the relative arrangement. Accordingly, based on the determined relative arrangement, it is first ascertained whether and to what extent the determined relative arrangement deviates from a desired relative arrangement. The positioning target then serves to correct this deviation. An improvement in the relative arrangement advantageously leads to improved imaging, in particular to improved fundus imaging. In other words, the relative arrangement is used to determine whether a suitable alignment exists between the optical instrument and the at least one element of the sample. This assessment is preferably based on criteria such as the lateral orientation and distance between the two components.Lateral alignment involves determining whether a lateral offset exists, which, for example, can restrict the image area during indirect fundus imaging. A similar principle applies to the distance, which also influences the image area; an incorrect distance can result in a significant portion of the posterior segment of the eye no longer being adequately visible. Therefore, the positioning specification advantageously provides instructions that enable improved relative positioning and enhanced imaging.

[0031] Preferably, the control unit is further configured to output the positioning specification to a user and / or to align the sample and / or the optical instrument based on the positioning specification. Thus, the user receives specific instructions for aligning the sample and the optical instrument. Alternatively, automated alignment is performed by a suitable positioning device, which is designed to exchange information with the control unit and can adjust the position of the sample or the optical instrument. If the optical instrument is permanently attached to an operating microscope, the positioning specification preferably aligns the operating microscope and thus indirectly the optical instrument.

[0032] The determination of the relative arrangement of the sample and the optical instrument according to the present disclosure is preferably carried out continuously, in response to the detection of the insertion of the optical instrument into a selected field of view or in response to the detection of a change in the scaling of the OCT signal over a period of time. For example, the system has a holder for optical instruments that can be inserted into the field of view, the current state of this holder is detectable, and this indicates whether the optical instrument has been inserted into the beam path or not (for example, a holder with a position sensor that can be pivoted into the beam path of an OCT system). In this case, the determination of the relative arrangement according to the present disclosure is preferably carried out when the holder is pivoted into the field of view.In a further preferred embodiment, the relative arrangement according to the present disclosure is determined when a temporal profile of the OCT signal shows a change in the scaling of the acquired OCT signal. This is preferably achieved by continuous OCT image recognition, whereby a sudden change in the size of the optical instrument or a sample element can be detected.

[0033] In a further preferred embodiment of the system according to the present disclosure, the control unit is additionally configured to receive a time-resolved image signal of the sample from an operating microscope system and to evaluate the relative arrangement in response to the detection of a characteristic structure, a change in image quality and / or sharpness of the image signal over a period of time. Here, too, the evaluation can be performed using the raw data or a generated image.

[0034] According to the invention, the relative arrangement comprises a lateral arrangement between a vertex of the optical instrument and a vertex of the at least one element of the sample and / or a distance between the optical instrument and the at least one element of the sample. In other words, a relative arrangement is determined based on the vertices of the optical instrument and the at least one element of the sample. Preferably, this is done using the OCT signal, which for this purpose comprises line scans, i.e., B-scans. The corresponding vertex of the sample element or optical instrument can be determined from these scans. The relative arrangement is determined by comparing the vertices. Preferably, the B-scans are used to determine whether axes through the vertices are parallel to each other.The axes are the vertex axes, defined by the vertices and axes of symmetry of the sample element or optical instrument. If these axes are not parallel to each other, this indicates a misalignment, such as an inclination of the eye relative to the optical instrument and vice versa. It is also preferred to determine whether both vertices lie on a straight line along the depth direction (optical axis of the OCT system or surgical microscope), i.e., whether they exhibit an offset perpendicular to the depth direction in a B-scan. The distance between the optical instrument and at least one element of the sample thus refers to a depth direction, i.e., the z-direction.

[0035] In a particularly preferred embodiment of the system according to the present disclosure, the OCT signal comprises a plurality of A-scans and / or B-scans, and the control unit is further configured to determine an OCT image from the plurality of A-scans or B-scans, to determine the height and / or inclination of the optical instrument and / or the at least one element of the sample, and to determine the relative arrangement based on the determined height and / or inclination. For example, a lateral displacement of the sample leads to an inclination of the cornea in the OCT image. This follows from the imaging processes underlying OCT imaging, in particular from the use of time-of-flight information to determine the OCT signal. Accordingly, the relative (lateral) arrangement can advantageously be inferred from such an inclination.The light travel times of the OCT sample beam, and thus the distances between the lens and the cornea depicted in the OCT image, increase in B-scans with larger lateral displacements. This causes the cornea to appear to be in a lower position in the OCT image. Conversely, if the cornea is optimally (laterally) positioned, it will be depicted in the highest possible position in a B-scan. The relative position can therefore be determined using the height of at least one element, for example, by varying a relative position until the corneal height depicted in the B-scan is maximized.

[0036] In a particularly preferred embodiment of the system according to the present disclosure, the OCT signal comprises data from a scan operation that includes at least 60%, preferably at least 80%, and particularly preferably at least 90% of the retina, the cornea, and / or the optical instrument. The data present in the OCT signal depend on the scan operation of the OCT system. For example, during a retinal scan, the OCT probe beam is deflected only slightly in the region of the anterior segment of the eye or the optical instrument and is not focused on the cornea. Due to the high sensitivity of modern SS-OCT systems, the surface (cornea and / or optical instrument) can nevertheless be reconstructed from the OCT signal. In other words, during indirect fundus imaging, where an ophthalmoscopic lens is positioned only a few millimeters above the patient's eye, the cornea and the lower surface of the lens are also imaged in the OCT signal.While these areas of the OCT signal are not relevant for fundus imaging, they can be advantageously used to determine the relative arrangement of the optical element and the sample. In an alternative embodiment, the cornea is scanned so that the OCT signal covers a large area of ​​the cornea. The OCT sample beam is scanned over larger areas of the cornea, whereas, if necessary, only peripheral areas of the retina are scanned. Accordingly, the relative arrangement is then determined based on the OCT signal encompassing the cornea. In principle, the accuracy of determining the relative arrangement can be improved the more data of at least one element of the sample is present in the OCT signal; that is, the larger the area of ​​the sample element scanned by the OCT sample beam.When generating a B-scan, this refers to the scanned length of the at least one element; in a C-scan, it refers to the scanned area of ​​the at least one element. In this context, the area specifications mentioned above refer to the proportion of a scanned (overscanned) length or area to the total length or area of ​​the sample element or optical instrument. The scanned (overscanned) length or area is not the sum of all scan points, but rather the length or area covered (enclosed) by the scan points. In a further preferred embodiment, the OCT signal comprises first and second data points based on a subdivision of the scanning process.Preferably, the OCT signal comprises first data (first OCT signal) based on a scan optimized for determining the relative arrangement, and second data (second OCT signal) based on a scan optimized for imaging the area to be imaged. For example, a first scan is performed covering as large an area as possible (preferably according to the area specifications given above), including the cornea. This provides an OCT signal for a corresponding portion of the cornea, which is particularly suitable for determining the relative arrangement. Furthermore, a second scan is performed to scan the fundus. Thus, advantageously, sufficient data is available to enable the determination of the relative arrangement.

[0037] In a particularly preferred embodiment of the system according to the present disclosure, the OCT signal comprises a plurality of laterally shifted B-scans, and the control unit is configured to determine a plurality of laterally shifted OCT images based on the plurality of laterally shifted B-scans, to determine a plurality of inclinations and / or heights of the at least one element of the sample in the plurality of laterally shifted OCT images, and to determine a plurality of relative arrangements based on the plurality of inclinations and / or heights. For example, a shift of the sample in the x- and / or y-direction leads to an inclination of the cornea in the OCT image. Thus, in order to center the optical instrument relative to the sample in the x- and / or y-direction, the inclination of the cornea in the determined OCT images can be optimized.An OCT image with a symmetrically and horizontally aligned cornea indicates an optimized relative arrangement of the optical instrument and the sample (eye). However, if the eye is moved laterally to the OCT system and the optical instrument, the corneal tilt increases, and the cornea appears to move further downwards in the depth direction (z-direction) of the OCT image. This is because the path length of the rays between the optical instrument (ophthalmoscopic loupe) and the cornea increases when the eye is moved laterally (angle ratio).

[0038] The displacement range is small, allowing only a few millimeters of movement before the cornea disappears from the B-scan. Therefore, the relative arrangement is critical for OCT imaging, particularly in posterior mode for scanning the fundus. Based on the multitude of laterally shifted B-scans acquired according to this embodiment, the inclination of the sample element, and consequently the relative arrangement, can be optimized. Preferably, the positioning specification described above is determined from the multitude of B-scans or OCT images, with the positioning specification preferably corresponding to the relative arrangement of the multitude of relative arrangements that can be assigned to a maximum of the multitude of heights and / or a minimum of the multitude of inclinations.Accordingly, the best possible arrangement can be successively determined using an OCT signal, preferably obtained by lateral displacement of the sample and / or the optical instrument.

[0039] In a particularly preferred embodiment of the system according to the present disclosure, it further comprises an OCT system (as described above) and a surgical microscopy system configured to acquire a time-resolved image signal of the selected field of view of the sample. The surgical microscopy system includes an image sensor configured to acquire a time-resolved image signal of the selected field of view (region of interest - ROI) of a sample, and preferably optics, which may include, for example, an objective lens and an eyepiece, but may also include further components, in particular additional lenses, mirrors, beam splitters, and / or the like. The optics and the image sensor are preferably integrated, for example, as parts of a camera of a surgical microscope.According to this embodiment, the control unit is further designed and configured to determine video image data corresponding to the acquired time-resolved image signal. The time-resolved image signal is, in particular, a multitude of signals assigned to surface elements of the sample, which are acquired sequentially or simultaneously for a specific grid of the sample surface, the grid being determined by a scanning mechanism and / or the image sensor. The time-resolved image signal also has a clock frequency (frame rate) that is determined by a scanning mechanism and / or the image sensor. The control unit generates video image data from this image signal with a grid (resolution) and a frame rate suitable for display on the display device.The control unit is further equipped to display the video image data simultaneously or sequentially with the time-resolved OCT image and / or with the virtual area on the display device.

[0040] In a preferred embodiment of the system according to the present disclosure, the control unit is further configured to identify the optical instrument and / or the at least one element of the sample by segmenting the OCT signal or the OCT image.

[0041] By segmenting the OCT signal, the control unit is advantageously able to identify the position of the optical instrument and / or at least one element of the sample within the OCT volume. Various algorithms for automatically segmenting objects in image data are known to those skilled in the art. These algorithms include traditional threshold-based image processing algorithms as well as newer, machine learning-based 2D and 3D segmentation networks (for example, a U-Net segmentation network). The control unit is preferably configured to obtain the segmentations from individual 2D OCT B-scans or directly from the entire 3D OCT volume. The positions obtained in this way are advantageously usable in volume rendering, ray tracing, and / or ray marching, as described above. Preferably, the segmentation comprises a combination of a convolutional neural network and traditional image processing.This enables real-time processing.

[0042] The system according to the present disclosure preferably further comprises an interface designed to capture user input. The interface is preferably a hand switch, a foot switch, and / or means for detecting head and / or eye movements or an actual gaze direction, for example, integrated into video glasses or a head-mounted display (HMD). The interface can also be designed to capture voice commands and may include at least one microphone for this purpose. Equally preferably, the interface is a keyboard, a joystick, a mouse, a touchscreen, or a combination thereof.

[0043] According to this preferred embodiment, the control unit is further configured to control the interface for capturing user input. Preferably, the user input is preceded by an input prompt, which is, for example, output to the user via the output device. Also preferably, the user input is a selection from a plurality of predefined input options, which is, for example, an instruction to perform the alignment based on the positioning output. Also preferably, the user input is freely definable by the user within a predefined framework. Also preferably, the control unit is configured to support the user during input, for example, by displaying a plurality of dialogs for the targeted querying of specific user inputs.

[0044] Another aspect of the present disclosure relates to a method for determining the spatial arrangement of an optical instrument. This method includes the step of receiving a time-resolved OCT signal of a sample from an OCT system (as described above). The method further includes the step of determining a relative arrangement between the optical instrument and at least one element of the sample based on the OCT signal. Finally, the method according to the present disclosure generates an output based on the determined relative arrangement. The method according to the present disclosure realizes the same advantages as the system according to the present disclosure, and in this regard, reference is made to the above statements.

[0045] In a preferred embodiment of the method according to the present disclosure, it further comprises the steps of determining a positioning specification based on the relative arrangement and outputting the positioning specification to a user and / or performing an alignment of the sample and / or the optical instrument based on the determined positioning specification. Further preferred embodiments of the method according to the present disclosure correspond to further preferred embodiments of the system according to the present disclosure and realize the same advantages as the embodiments.

[0046] Another aspect of the present disclosure relates to a computer program comprising instructions which, when executed by a control unit as described above, preferably an operating microscope as described above, cause the system or operating microscope as described above to execute the method according to the invention as described above. The computer program preferably comprises instructions which, when executed by a control unit as described above, preferably an operating microscope, cause the system or operating microscope as described above to execute the method according to the invention according to one of the preferred embodiments as described above.The computer program according to the invention is preferably stored in volatile memory, for example a RAM element, or in a non-volatile storage medium, such as a CD-ROM, a flash memory or the like.

[0047] Further preferred embodiments of the invention are evident from the remaining features mentioned in the dependent claims and the figures described below. Unless otherwise specified in a particular case, the various embodiments of the invention mentioned in this application can be advantageously combined with one another. Description of the characters

[0048] The invention is explained below using exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1a a schematic representation of a relative arrangement of an eye and an ophthalmoscopic magnifying lens; Fig. 1b an indirect fundus image using the arrangement of Fig. 1; Fig. 2a - 2d Influences of the relative arrangement of the eye and the ophthalmoscopic lens on indirect fundus imaging; Fig. 3 a schematic representation of a system for evaluating the spatial arrangement of an optical instrument according to a first embodiment; Fig. 4 a schematic representation of a system for evaluating the spatial arrangement of an optical instrument according to a second embodiment; Fig. 5a a representation of the visualization of an OCT image with an anterior and posterior segment of the eye and a surface of an ophthalmoscopic magnifying lens; Fig. 5b a schematic representation of beam paths of two OCT sample beams at two scan points of the OCT image from Fig. 5a; Fig. 5c a schematic representation of a relative arrangement with hybrid representation of the OCT image from Fig. 5a; Fig. Figures 6a-6e show a visualization of multiple OCT images of a laterally displaced eye; and Fig. 7. A representation of the visualization of a multitude of OCT images of an eye shifted in depth direction; Fig. 8 a schematic flowchart of a procedure according to an implementation form.

[0049] Fig. Figure 1a shows a schematic representation of the arrangement of a patient's eye 50 and an ophthalmic magnifying lens 40. The eye 50 comprises a retina 51 and a cornea 52. For indirect fundus imaging (viewing the posterior segment of the eye) during an ophthalmic surgical procedure, an additional optical instrument, namely an ophthalmic magnifying lens 40, is swung below an operating microscope (not shown). The ophthalmic magnifying lens 40, which is positioned a few millimeters (approx. 2-5 mm) above the eye 50 using a holder 43, produces an intermediate image for indirect fundus imaging. This intermediate image is magnified and displayed to the surgeon in eyepieces or other display media, as exemplified in Figure 1a. Fig. 1b is shown.

[0050] The positioning of the ophthalmic magnifying lens 40 over the patient's eye 50 is crucial for intraoperative imaging. Lateral displacement of the ophthalmic magnifying lens 40 relative to the eye 50, as well as a different distance between the ophthalmic magnifying lens 40 and the eye 50, have adverse effects on imaging (visual or other possible imaging modalities, e.g., OCT, LSO).

[0051] The influence of relative arrangement on indirect fundus imaging is described in the Fig. Figures 2a to 2d show this. For this purpose, an artificial glass test eye 50 is shown in various relative arrangements to the ophthalmoscopic magnifying lens 40 and the operating microscope, which is preferably connected to the ophthalmoscopic magnifying lens 40. A checkerboard pattern 51 is printed on the fundus of the artificial glass test eye 40 to better visualize the effects as a simulation of the retina 51. A lateral displacement of the ophthalmoscopic magnifying lens 40 allows the video image to be viewed as shown in Figures 2a to 2d. Fig. The images shown in 2c disappear depending on the degree of displacement. The OCT images not shown here are still visible, but also disappear from a certain degree of displacement. The influence of a distance between the eye 50 and the ophthalmoscopic magnifying lens 40 in the depth direction or z-direction is shown in Fig. Figure 2d shows that since the OCT beam path between the ophthalmoscopic magnifying lens 40 and the eye 50 ideally runs parallel, the B-scans are less affected. In contrast, the pupillary misalignment is clearly visible in the video image and causes a significantly reduced field of view. Fig. Figure 2b shows the combined effect of a lateral displacement and an increased working distance. A correct relative arrangement, however, is shown in Fig. 2a shown.

[0052] Fig. Figure 3 shows a schematic representation of a system 100 for evaluating the spatial arrangement of an optical instrument according to a first embodiment.

[0053] System 100 comprises an OCT system 10, which includes a broadband light source 11, such as a superluminescent diode or a tunable laser. The light from the broadband light source 11 is directed into an interferometer with a beam splitter 14 and a movable mirror 15. In the beam splitter 14, the light is split into a sample beam 12 and a reference beam 13. The sample beam 12 is scanned by means of a scanning mirror 16, for example, over the eye of a patient 50 positioned in the field of view of the sample beam path. The reference beam 13 is directed onto the movable mirror 15 and reflected from there back onto the beam splitter 14. The sample beam 12 interacts with the eye of the patient 50, is scattered from there back to the scanning mirror 16, and from there directed onto the beam splitter 14.There, the backscattered sample beam 12 and the reflected reference beam 13 are superimposed, with a path difference between the superimposed beams 12 and 13 being set by the movable mirror 15. The interference pattern 17 thus generated is detected by a detector 18, for example, a CCD detector or a CMOS detector, and transmitted as an OCT signal 19 to a control unit 20, the control unit 20 being configured to carry out the disclosed method. Furthermore, an optical instrument 40 arranged in the beam path 12 of the OCT system 10 is shown. In other words, the sample beam 12 is backscattered by the optical instrument 40, for example, a surface thereof, and the backscattered component is superimposed with the reference beam 13 in the interferometer 14. A reference pattern 17 generated by this superposition is detected by the detector 18 as an OCT signal 19.

[0054] Fig. Figure 4 shows a schematic representation of a system 100 for evaluating the spatial arrangement of an optical instrument according to a second embodiment. The OCT system 10 includes, among other things, the same components as the system described in relation to Fig. The OCT system 10 described in section 2 is described below. A repeated description of these components is omitted here. Furthermore, the OCT system 10 features... Fig. Figure 3 comprises an operating microscope system 30, which is designed to acquire an image signal 33 from a field of view 34, wherein this field of view 34 can include both the patient's eye 50 and the optical instrument 40. Likewise, an operating microscope system can include an OCT system 10. The schematic arrangement of the OCT system 10 next to the operating microscope system 30 is for clarity only. Preferably, the operating microscope system 30 includes the OCT system.

[0055] The operating microscope system 30 comprises at least one imaging sensor 32 designed to capture the image signal 33 and an optical system 31. The imaging sensor 32 and the optical system 31 are part of a main observation camera of the operating microscope system 30. The operating microscope system 30 also comprises a peripheral camera 24, which is designed to display the patient's eye 50 at a lower zoom level than the main observation camera. The operating microscope system 30 further comprises a beam splitter arranged in the beam path 35 of the operating microscope system 30 for partially deflecting object rays onto an eyepiece 38 and thus onto the eye of an observer 37. In addition, the operating microscope system 30 comprises a further light source 36 for illuminating the patient's eye 50.The main observation camera transmits image signals 33 via a suitable data connection to the control unit 20, to which the surrounding camera 24 is also connected. The control unit 20 is connected to a memory 21, on which, for example, algorithms for image recognition and previously known parameters of previously known optical instruments are stored. The control unit 20 is also connected to a user interface 22 for capturing user input and to an output device 23 for output. Fig. Figure 4 further shows a mounting 43 of the optical instrument 40 with which it is fixed to optics 31 of the main observation camera. In the embodiment of the Fig. 3 and Fig. The time-resolved OCT signal 19, acquired by the detector 18, is transmitted to the control unit 20. Based on the OCT signal 19, the control unit 20 determines a relative arrangement between the optical instrument 40 and at least one element of the sample 50, and outputs a result based on this relative arrangement. The relative arrangement is preferably determined directly from the OCT signal 19, i.e., from the raw data. Alternatively, an OCT image is first acquired from the OCT signal, and the relative arrangement is then determined from this image. This is preferably done using an OCT image evaluation unit. The image evaluation is performed using known algorithms. For clarity, the determination is performed using an OCT image in the present embodiment.

[0056] Fig. Figure 5a shows a visualization of an OCT image with an anterior and posterior segment of the eye 60, 70, and a surface 41 of an ophthalmoscopic lens 40. The posterior segment 70 contains, among other structures, the retina 51. The anterior segment 60 contains the cornea 52. Here, the curvature of the retina 51 and the curvature of the surface 41 of the ophthalmoscopic lens 40 are clearly visible. However, the cornea 52 shows only a slight curvature. This can be seen from Fig. Explain section 5b. This section shows beam paths for two OCT sample beams at two scan points (A-scans) used for cross-sectional image generation. In the upper cross-sectional image, the laser beam is only slightly deflected during a scan and is not focused on cornea 52. Therefore, only a significantly smaller area of ​​cornea 52 is scanned, which in turn makes the curvature less pronounced. However, due to the high sensitivity of modern SS-OCT systems, the surfaces (cornea 52 and ophthalmoscopic lens 40) can still be reconstructed from the OCT signal 19. Fig. Figure 5c shows a schematic representation of a relative arrangement with hybrid representation of the OCT image from Fig. 5a. The OCT depth-sectional image is divided into two partial images, with the posterior segment of the eye 70 displayed enlarged for visualization and the anterior segment 60 used to determine the relative arrangement and for the automatic alignment of the operating microscope 30. For illustration, the cornea 52 is shown in a first view and a magnified view; the same applies to the surface 41 of the ophthalmoscopic magnifying lens 40.

[0057] The control unit 20 determines a distance D in the depth direction of the OCT image, i.e. in the z-direction. Zbetween the surface 41 of the ophthalmoscopic lens 40 and the at least one element of the sample 40, where the at least one element is, for example, the cornea 52. Furthermore, a lateral displacement is preferably determined by, among other things, comparing vertices 42, 53, which are assigned to the surface 41 of the ophthalmoscopic lens 40 and the cornea 52. The vertices 42, 53 also serve as reference points for determining the distance. The control unit 20 thereby determines the relative arrangement. Preferably, it is determined using B-scans whether axes through the vertices 42, 53 run parallel to each other.Preferably, it is checked whether both vertices 42, 53 are arranged on a straight line OA running along the depth direction, i.e., the optical axis of the system, and thus exhibit an offset with respect to a B-scan along an axis perpendicular to the depth direction (x- or y-axis). Such an optical axis OA is shown in the figure, and it can be deduced that there is no offset in the x-direction.

[0058] The Fig. Figures 6a to 6e show a visualization of numerous OCT images of a laterally displaced eye 50. This illustration is intended to explain the influence of the relative arrangement on the OCT images and the insights gained from this for determining the relative arrangement. The ophthalmoscopic lens 40, or rather its position, serves as the reference for determining the relative arrangement of the patient's eye 50 and preferably aligning it automatically. In this case, the image depth is sufficient to image the ophthalmoscopic lens 40 including the cornea 52. The image depth here is approximately 30 mm, which can be achieved, for example, with an SS-OCT. In posterior mode, the determination and alignment are preferably separated between the x, y, and z directions.

[0059] Fig. Figure 6c shows an optimal alignment between cornea 52 and ophthalmoscopic magnifying lens 40. Fig. 6b and Fig. Figure 6d shows a displacement of the cornea 52 by ± 1 mm in the x-direction.

[0060] Fig. 6a and Fig. 6e show a further displacement in the ± x direction. The OCT images show that the lateral displacement leads to a tilt / skew 54 of the cornea 52 in the OCT image. To center the ophthalmoscopic lens 40, the corneal tilt 54 is determined and reduced. The goal is to obtain a cornea 52 that appears as symmetrical and straight as possible in the B-scans. Another effect can also be observed in the B-scans. As the eye 50 is moved further laterally, the tilt 54 increases, and the cornea 52 migrates further and further downwards in the OCT image until it eventually disappears completely. This is because the path length of the rays between the ophthalmoscopic lens 40 and the cornea 52 increases when the eye is moved laterally (angle ratio). In general, the displacement range is small. Only a few millimeters of displacement are possible before the cornea 52 disappears in the B-scan.Thus, the inclination of at least one element of the sample, in this case the cornea 52, can be used to determine the relative arrangement and, in a further step, to determine a positioning specification based on the determined relative arrangement. Based on the positioning specification, the optical instrument 40 or the eye 50 is then preferably aligned. Priority is initially given to the lateral x and y directions.

[0061] Preferably, the magnifying lens holder 43 is perfectly aligned with an OCT system 10 or a microscope head of the operating microscope system 30. Accordingly, the ophthalmic magnifying lens 40 and the OCT system 10 or the microscope head perform identical movements. The OCT system 10 is then moved laterally over a specific area and continuously records B-scans. Only changes in the x and y directions are considered. The z-position must remain constant. The B-scans are evaluated and compared. A relative arrangement is thus continuously determined by the control unit 20. When the cornea 52 is optimally positioned, it is located at the highest possible position in the B-scan. The propagation lengths of the laser beam, and thus the distances displayed between the ophthalmic magnifying lens 40 and the cornea 52 in the B-scan, increase with larger lateral displacements.This results in the cornea 52 appearing to lie in a lower position in the OCT image, thus reducing its height 55. Furthermore, the inclination 54 of the cornea 52 is evaluated. At the optimal position, the mean inclination 54 of the cornea (for scans in the x-direction) should be zero.

[0062] For the axial alignment, i.e., in the z-direction, different criteria are considered for determining the relative alignment. However, the same conditions apply as for the lateral alignment. The theoretical distance between an ideal cornea 52 and the surface 41 of the ophthalmoscopic lens 40 is predetermined. The anterior chamber of the human eye 50 has an individual thickness. To align the pupils, the ophthalmoscopic lens 40 would therefore have to be actually aligned with the patient's pupil. One approach is to determine the distance between the corneal surface and the pupil based on previous anterior measurements. The theoretical distances can then be modified according to the patient's measurement result. In this way, the individual distance between the cornea 52 and the patient's pupil can be taken into account.Another important prerequisite is the previously performed lateral alignment, since, as already mentioned, a lateral offset can affect the z-position of the cornea 52. The distance between the ophthalmoscopic lens 40 and the cornea 52 is in air. This simplifies measurement, as the optical path length in air equals the geometric path length. Furthermore, dispersion can be neglected. A calibrated B-scan of the ophthalmoscopic lens 40, including the cornea 52, with the precisely known depth of field can be used. Both the ophthalmoscopic lens 40 and the cornea 52 must be identified. Subsequently, the absolute distance between them can be calculated. The deviation from the configuration-dependent theoretical distance can be determined in metric dimensions. The z-position of the microscope head is then preferably adjusted accordingly.

[0063] The influence of the relative arrangement in the z-direction on the imaging is described in Fig. Figure 7 shows the ophthalmoscopic lens 40 and the cornea 52 of eye 50. Eye 50 is optimally positioned in the central B-scan. From left to right, eye 50 was moved in the z-direction in 1 mm increments. In the lower positions, the resulting signal from eye 50 decreases. Therefore, the focus position was changed in the three B-scans on the left side to ensure that the cornea 52 could still be visualized. As eye 50 moves closer to the ophthalmoscopic lens 40, a change in shape becomes visible. The laser beams exit the ophthalmoscopic lens 40 at different angles depending on the scanning angle. The position at which the beams strike the corneal surface is thus influenced by the z-position. In the B-scans, this can lead to a change in the displayed corneal shape.The effect also occurs in all posterior configurations, but the shape of the cornea 52 and its behavior are different in each case. Fig.Figure 8 shows a schematic flowchart of a method according to one implementation form. The method comprises a first step S100 of receiving a time-resolved OCT signal 19 of a sample 50 from an OCT system 10. The OCT signal 19 preferably comprises a plurality of tuples, wherein at least one tuple of the plurality of tuples represents a volume element of the sample 50 and at least one tuple of the plurality of tuples represents a volume element of the optical instrument 40. The method further comprises a second step S200 of determining a relative arrangement between the optical instrument 40 and at least one element of the sample 50 based on the OCT signal 19. Finally, in a third step S300, an output is determined based on the determined relative arrangement.Subsequently, in step S400, a positioning specification is determined based on the relative arrangement, and finally, in step S500, the positioning specification is output to a user and / or an alignment of the sample 40 and / or the optical instrument 40 is carried out based on the determined positioning specification. Reference symbol list 100 System 10 OCT system 11 broadband light source 12 Sample beam 13 Reference beam 14 beam splitters (interferometers) 15 movable mirrors (interferometer) 16 Scan mechanism (scan mirror) 17 interference patterns 18 Detector 19 OCT signal OA optical axis 20 Control unit 21 storage 22 User interface 23 expenditure funds 24 Surround camera 30 operating microscope system 31 Optics 32 imaging sensor 33 Image signal 34 field of vision 35 Beam path 36 Light source 37 Eye of a beholder 38 eyepiece 40 optical instrument / ophthalmoscope magnifying glass 41 surface 42 Vertex 43 bracket 50 samples per patient's eye 51 Retina / Checkerboard pattern 52 Element of the sample / cornea 53 Vertex 54 Inclination / tilt of the cornea 55 Height of the cornea 60 anterior segment of the eye 70 posterior segment of the eye d distance between optical instrument and eye D Z Distance between optical instrument and at least one element of the sample

Claims

System (100) for determining a spatial arrangement of an optical instrument (40), comprising: a control unit (20) configured to receive a time-resolved OCT signal (19) of a sample (50) from an OCT system (10); determining, based on the OCT signal (19), a relative arrangement between the optical instrument (40) and at least one element (52) of the sample (50), wherein the relative arrangement comprises a lateral arrangement between a vertex (42) of the optical instrument (40) and a vertex (53) of the at least one element (52) of the sample (50) and / or a distance between the optical instrument (40) and the at least one element (52) of the sample (50); and determining an output based on the determined relative arrangement. System (100) according to claim 1, wherein the optical instrument (40) comprises a magnifying glass, an ophthalmoscopic magnifying glass, a contact lens, a lens and / or a vitrectomy lens. System (100) according to claim 1 or 2, wherein the sample (50) comprises an eye (50) and the at least one element (52) of the sample (50) comprises a pupil, cornea (52) and / or retina (51), preferably at least one surface of the cornea (52) and / or retina (51). System (100) according to claim 3, wherein the time-resolved OCT signal (19) comprises a cornea scan and / or a retina scan. System (100) according to one of claims 3 or 4, wherein an imaging depth of the OCT signal exceeds an eye length of the sample (50) and the control unit is configured to determine the eye length based on the OCT signal and to determine the relative arrangement based on the determined eye length. System (100) according to one of the preceding claims, wherein the control unit (20) is further configured to determine a positioning specification based on the relative arrangement. System (100) according to claim 6, wherein the control unit (20) is further configured to output the positioning specification to a user and / or to align the sample (50) and / or the optical instrument (40) based on the positioning specification. System (100) according to one of the preceding claims, wherein the control unit (20) is configured to continuously determine the relative arrangement in response to the detection of the insertion of the optical instrument (40) into a selected field of view (34) or in response to the detection of a change in the scaling of the OCT signal (19) in a time course of the OCT signal (19). System (100) according to one of the preceding claims, wherein the control unit (20) is further configured to: receive a time-resolved image signal (33) of the sample (50) from an operating microscope system (30); and evaluate the relative arrangement in response to the detection of a characteristic structure, a change in the image quality and / or sharpness of the image signal (33) in a time course of the time-resolved image signal (33). System (100) according to one of the preceding claims, wherein the OCT signal (19) comprises a plurality of A-scans and / or B-scans and the control unit (20) is configured to determine an OCT image from the plurality of A-scans or B-scans, to determine a height (55) and / or an inclination (54) of the optical instrument (40) and / or of the at least one element (52) of the sample (50), and to determine the relative arrangement based on the determined height (55) and / or the determined inclination (53). System (100) according to one of the preceding claims, wherein the OCT signal (19) comprises data from a scan operation comprising at least 60%, preferably at least 80% and particularly preferably at least 90% of the retina (51), the cornea (52) and / or the optical instrument (40). System (100) according to one of the preceding claims, wherein the OCT signal (19) comprises a plurality of laterally shifted B-scans and the control unit (20) is configured to determine a plurality of laterally shifted OCT images based on the plurality of laterally shifted B-scans, to determine a plurality of inclinations (54) and / or heights (55) of the at least one element (52) of the sample (50) in the plurality of laterally shifted OCT images, and to determine a plurality of relative arrangements based on the plurality of inclinations (54) and / or heights (55). System (100) according to one of the preceding claims, further comprising: an OCT system (10), an operating microscope system (30) designed to capture a time-resolved image signal (33) of the selected field of view (34) of the sample (50), wherein the control unit (20) is further configured to determine corresponding video image data on the basis of the captured time-resolved image signal (33), and to display the video image data simultaneously or sequentially with the time-resolved OCT image and / or with the virtual area on a display means. Method for determining a spatial arrangement of an optical instrument (40), comprising the method steps: Receiving (S100) a time-resolved OCT signal (19) of a selected field of view (34) of a sample (50) from an OCT system (10); Determining (S200) a relative arrangement between the optical instrument (40) and at least one element (52) of the sample (50) based on the OCT signal (19); and Determining (S300) an output based on the determined relative arrangement. The method of claim 14, wherein the method further comprises the following steps: determining (S400) a positioning specification based on the relative arrangement; and outputting (S500) the positioning specification to a user and / or performing (S500) an alignment of the sample (50) and / or the optical instrument (40) based on the determined positioning specification.

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