Apparatus for performing gonioscopy

Abstract

The present invention relates to an apparatus (13) for performing gonioscopy, which is capable of acquiring a three-dimensional volume (14) of a sample as a raw data set by optical coherence tomography. With a view to overcoming the technical drawbacks of gonioscopy lenses, the apparatus is characterized in that it comprises a visualization unit (15) capable of generating a virtual gonioscopy view (15a) from the raw data set, which appears to be taken from a virtual camera plane (16) located inside the sample. The present invention also relates to a method for acquiring the structure of the iridocorneal angle (14).

Description

[Technical Field]

[0001] The present invention relates to a device according to the preamble of claim 1. [Background technology]

[0002] The term optical coherence tomography (usually abbreviated as OCT) is understood as an imaging method that allows two- and three-dimensional images to be obtained from light-scattering structures. In this method, light with a specific bandwidth is usually split into two partial beams in a beam splitter. The first partial beam is incident on the sample or object to be examined, while the second partial beam is transmitted through a reference section. The light reflected from the sample or object interferes with the reference beam. The interference signal can be used to examine the sample with depth resolution, i.e., at the depth of the optical axis of the first partial beam, by a so-called A-scan. Furthermore, the first partial beam can also be scanned horizontally or laterally across the sample to obtain OCT images.

[0003] In the human eye, the cornea and iris form a structure in the anterior chamber of the eye. This structure is called the iridocorneal angle. Aqueous humor flows out of the iridocorneal angle. Pathological changes in the iridocorneal angle can lead to increased intraocular pressure and the development of glaucoma. The so-called Schlemm's canal extends in a circular shape in the scleral part of the iridocorneal angle, i.e., in the scleral region, and forms a collecting canal, i.e., a drainage canal, for aqueous humor.

[0004] The structures at the iridocorneal angle of the eye cannot be seen directly without technical assistance due to the refractive relationship at the cornea and the opacity of the sclera to visible light. To visualize the structures, a gonioscopy lens is currently used that directly contacts the cornea, avoiding the refraction of its anterior surface, and peers "beyond the angle" into the iridocorneal angle by means of a mirror system. Surgery is performed exclusively through this lens.

[0005] The use of gonioscopy lenses and visualization through them restricts the surgeon in many ways. Handling the lenses and interpreting the visualization of structures is generally difficult to master. The surgeon must directly guide the lens with one hand during surgery. This restricts the surgeon from using this hand for other purposes, such as guiding another instrument or controlling visualization in parallel.

[0006] The surgeon can only see the surface of the tissue; information from deeper tissue remains hidden. Furthermore, external instruments used during surgery may obstruct the view of structures at the iridocorneal angle.

[0007] This may be due to the flat field of view caused by the deflection of the contact lens. However, glaucoma surgery must be able to be performed without contact lenses. Therefore, there is a need to improve visualization of structures in the iridocorneal angle during surgery. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention aims to overcome the technical drawbacks of gonioscopy lenses. [Means for solving the problem]

[0009] The present invention achieves the above-mentioned object by means of the features of claim 1.

[0010] In accordance with the present invention, it has first been recognized that structures in the iridocorneal angle of the human eye should be captured as optically as possible. It has also been recognized that there is a need for improved visualization of structures in the iridocorneal angle region during surgery. Specifically, it has been recognized that this can be achieved by visualizing structures such as Schlemm's canal, especially at depth. It has also been recognized that such visualization of the surgery should not be hindered by surgical instruments. In accordance with the present invention, it has been recognized that gonioscopy can be performed using an OCT device by acquiring a three-dimensional volume of a sample, i.e., an OCT volume, as a raw data set using optical coherence tomography, and providing a visualization unit capable of generating a virtual gonioscopy view from the raw data set, which appears to be taken from a virtual camera plane located within the sample. The virtual gonioscopy procedure described herein does not require refractive lenses, thereby further freeing up the surgeon's hands.

[0011] The visualization unit can render images of the 3D volume, treating it as a raw data set, and generate a virtual gonioscopy view from a virtual camera plane using this raw data set. Thus, OCT volumes can be acquired intraoperatively over a circularly related angle at the limbus, the transition zone between the cornea and the sclera. The OCT volumes are then rendered onto a virtual camera inside the anterior chamber, resulting in a frontal view similar to that seen through a gonioscopy lens. In this way, the aforementioned drawbacks of glaucoma surgical intervention can be overcome.

[0012] "The virtual gonioscopy OCT image allows the surgeon to operate based on the virtual gonioscopy image. Furthermore, this rendered virtual gonioscopy allows visualization of deep tissue and structures, such as the extent of Schlemm's canal, which is hidden by the trabecular meshwork of the anterior chamber. This is a crucial advantage for the surgeon, especially since Schlemm's canal is the target site for the implant."

[0013] The real and virtual camera planes may subtend an angle ranging from 80° to 140°, and preferably are oriented orthogonally to each other, allowing for quantitative measurement of the extent of anatomical structures as well as visualization of structures (e.g., Schlemm's canal) that are actually hidden in the reflected light image.

[0014] At least one volume or OCT volume may be acquired by the detection unit along a circular arc section, preferably over an angular range of 10° to 120°. Advantageously, the OCT volume is acquired so that the limbus of the eye, which contains the structures necessary for glaucoma surgical intervention, is located within the volume. Advantageously, the OCT volume encompasses at least 10° to 120° of the circular angle of the limbus, since this corresponds to the preferred viewing angle in gonioscopy.

[0015] Against this background, multiple volumes or OCT volumes can be acquired in temporal succession and acquired as raw data sets. To ensure a sufficiently high lateral resolution at a sufficiently high image repetition rate, it is advantageous to visualize only a small region around the angular range of interest within a small volume of the limbus.

[0016] Said arc section can be part of a ring segment or part of a spiral, in particular an elliptical spiral, and it is technically advantageous to scan a ring segment around the annulus when a large viewing angle range is required, or an elliptical spiral when a smaller viewing angle range is required.

[0017] External instruments for the sample surgery can be displayed transparently in the virtual gonioscopy display by the visualization unit or optically removed therefrom. Due to the steeper light angle of OCT imaging compared to gonioscopy, the external instruments used do not cast shadows on the view of the iridocorneal angle. Therefore, since the view from the anterior chamber is only virtual, it is possible to subtract the instruments used in the surgery from the gonioscopy display or display them semi-transparently, which is not possible with conventional gonioscopy.

[0018] The OCT system may include a tracking unit that can track the light for optical coherence tomography through the volume of the sample's movement. As mentioned above, when the OCT volume is scanned in a small area around the limbus, it is advantageous to track the eye's movement relative to the microscope and track the scan between volumes accordingly. The tracking information can be generated from the OCT data itself or by an additional camera, for example, the microscope itself.

[0019] Furthermore, it is advantageous to follow the relevant limbal region with another imaging modality, which controls the lateral positioning of the OCT volume, advantageously using an operating microscope image.

[0020] The apparatus may include an adjustment unit, which may be used to automatically determine and define the virtual camera plane based on the structure of the sample. Alternatively or additionally, the adjustment unit may be manually operable so that the position and orientation of the virtual camera plane can be set under user control. The viewpoint of the virtual view is preferably determined automatically, i.e., based on the segmentation of the eye structures in the OCT data (e.g., the corneal apex and iris plane). The surgeon can adjust the automatically adopted viewpoint of the view corresponding to the virtual camera plane. For this purpose, the height of the camera plane or the rotation of the plane around the optical axis of the eye can be controlled. While conventional gonioscopy requires training, the correct view is automatically adopted using the apparatus described herein.

[0021] The volume may be acquired at a repetition rate in the range of 1 Hz to 1 kHz. Alternatively or additionally, the latency for the virtual gonioscopy display to be available may be less than 500 ms. Structures of the iridocorneal angle can be adequately acquired by selecting this frequency range. It is particularly advantageous for the OCT volume to be acquired at a repetition rate of at least 20 Hz. It is also advantageous for the latency for the rendered virtual gonioscopy display to be available to be less than 100 ms. This allows the surgeon to fully understand the situation.

[0022] A method of performing virtual gonioscopy using an apparatus for performing optical coherence tomography, particularly an apparatus of the type described herein, rather than a gonioscopy lens, includes: - illuminating the eye from a real camera plane by optical coherence tomography and acquiring a three-dimensional volume of the eye from the real camera plane as a raw data set; generating a virtual gonioscopy display from the raw data set, the virtual gonioscopy display arising from a virtual camera plane within the eye and allowing a top view of the ocular structures; displaying the iridocorneal angle structures of the eye in a virtual gonioscopy display; Includes.

[0023] Such a method, performed by the apparatus described herein, allows the omission of a gonioscopy lens.

[0024] In the sense described above, the volume or OCT volume should not be selected to be unnecessarily large, since in that case a high repetition rate cannot be achieved under conditions of high-density scanning and coverage. Each OCT volume thus acquired is projected onto a virtual camera plane. The projection should be performed so that the image resembles a view through a gonioscopy lens.

[0025] The projection should now be such that the scleral zone, the ciliary body and the trabecular meshwork can be distinguished with as high a contrast as possible.

[0026] With this background, the aforementioned structures may include Schlemm's canal, ciliary body bands, scleral bands, trabecular meshwork, and / or Schwalbe's lines. One of the clinical targets in many glaucoma surgical interventions is Schlemm's canal. Because this canal is not visible in microscopic images, surgeons focus on the pigmented trabecular meshwork behind which Schlemm's canal is located. Schlemm's canal can be visualized or segmented using an OCT device and highlighted accordingly.

[0027] The volume can be acquired over an angular range of 10° to 120° along the limbus path. The volume scan pattern should be designed so that the minimum distance between OCT voxels perpendicular to the limbus is small enough to adequately scan the transitions between structures (ciliary band, scleral band, Schwalbe's line). Given these requirements, the use of high-speed OCT is clearly advantageous.

[0028] The volume can be projected onto a virtual camera plane such that the projection image resembles the view through a gonioscopy lens, creating a virtual gonioscopy view, allowing the surgeon to use familiar depictions they already know from practice.

[0029] Various methods are possible for projecting the relevant structures in the OCT volume. A simple pinhole camera model can be used as a model for the virtual camera. The OCT volume is then mapped onto the display pixels of the virtual camera by central projection. The camera center can be located here at a finite or infinite location.

[0030] Advantageously, the transition from the anterior chamber to the fixed structures iris, ciliary body, sclera, trabecular meshwork and cornea is segmented. Using the segmentation line, a frontal projection can be calculated from the thin part of the boundary layer onto the virtual camera plane by central projection.

[0031] Another approach involves ray casting through the pixels of the virtual camera plane. For this purpose, voxels of the OCT volume are assigned opacity using an appropriate opacity function depending on their intensity. The opacity function is advantageously selected so that "aqueous humor" voxels are assigned no opacity and all tissues are assigned maximum opacity. To ensure a good quality depiction, it is advantageous for the OCT device to have high sensitivity. The next most transparent tissue after aqueous humor is the cornea. Its contrast with the aqueous humor should be sufficiently large. The ray casting projection is performed so that for each pixel of the virtual camera, a beam is calculated that is assigned according to a central projection through the OCT volume. The intensities of the OCT voxels are weighted according to their opacity and summed. However, the voxel intensities are only summed from the camera plane in the beam direction until the summed opacity value exceeds a threshold.

[0032] The positioning and alignment of the virtual camera plane should be automatically preselected, but the user should be able to change the positioning and alignment with some freedom.

[0033] The methods described herein may be performed intraoperatively, particularly during glaucoma surgical intervention.

[0034] Below, the method is described based on any refinements.

[0035] Structures of the iridocorneal angle of the eye that are important for diagnosis and treatment cannot be seen under the operating microscope without technical assistance.

[0036] Using the method described here, structures at the iridocorneal angle can be viewed while using a surgical microscope with intraoperative OCT, without the need for additional equipment.

[0037] A volume tomography image is generated of an information-containing region at the limbus of the eye so that structures necessary for diagnosis or surgical treatment, i.e., the scleral spur, the ciliary body, the trabecular meshwork, Schlemm's canal, etc., can be seen.

[0038] This tomographic image must be further processed so that it can be used for the applications mentioned above.

[0039] For this purpose, a virtual camera view is generated from this tomographic data in order to visualize the aforementioned structures as they appear.

[0040] Advantageously, this virtual gonioscopy view is based on the view that is familiar to the surgeon, produced by a gonioscopy lens.

[0041] For this purpose, a virtual camera plane is advantageously placed in the anterior chamber in a corresponding pose and the tomographic data is projected onto this plane in such a way that the above-mentioned anatomical structures are displayed with high contrast.

[0042] It is also advantageous to display in this projection important structures within the ocular tissue, such as Schlemm's canal, which are often target variables for surgical intervention, information or structures that can be obtained from tomographic images, in contrast to conventional methods.

[0043] Advantageously, important structures, such as the scleral promontory, can be highlighted by automatic segmentation. Advantageously, the pose and position of the virtual camera plane are adopted automatically.

[0044] A good configuration is obtained from the automatic segmentation of the anatomical structures of the eye: the posterior cornea, the scleral promontory, and the anterior iris. These information or structures are advantageously generated from tomographic OCT data and surgical microscope images.

[0045] The surgeon should also be able to control the configuration of the camera plane, so it is advantageous if the degrees of freedom of control are pre-defined and operable, for example, via a foot pedal, a 3D mouse or a touch panel.

[0046] Advantageously, the angle of rotation of the camera normal relative to the iris plane is controllable, as is the distance of the camera plane from the scleral spur, the rotation of the camera plane parallel to the limbus, and / or the width and height of the camera plane.

[0047] Also advantageous is an optional virtual camera plane in the tomographic data set transformed into cylindrical coordinates, where the cylinder axis points in a direction similar to the optical axis of the eye, which corresponds to a cylindrical camera plane of corresponding position and shape.

[0048] A typical display screen or binoculars can be used to visualize the virtual camera view.

[0049] Advantageously, an interactive augmented reality visualization of structures in the tomographic OCT data and the surgical camera images is provided.

[0050] For example, the projection of a selected virtual camera plane can be visualized on the surgical microscope image.

[0051] Additionally, the visible area of ​​the currently projected iridocorneal angle can be visualized in the camera image.

[0052] It is also advantageous to visualize the segmented scleral promontory in a virtual display.

[0053] Display of a projection of Schlemm's canal is also advantageous.

[0054] Still images can be visualized to assess the iridocorneal angle structures before or after surgical intervention.

[0055] For the surgical intervention itself or for the evaluation of dynamic processes, images can be displayed at a repetition rate that is at most a conventional video rate.

[0056] A necessary condition for this is to shorten the imaging time and at the same time increase the spatial scan density so that the iridocorneal structures can be seen with a sufficiently high resolution.

[0057] To achieve this with current technical possibilities, a small volume should be imaged in the corresponding limbal region.

[0058] An OCT device with a high equivalent A-scan rate is advantageous. In embodiments with a scanning system, a high rate of scanning motion is advantageous.

[0059] Control of the OCT volume can be advantageously achieved by assessing the relevant scan range: for example, the limbus can be segmented at a selected angle from the surgical camera image, and the scanner of the OCT system can be controlled from the modality registration information so that only the smallest possible volume region is scanned with a sufficiently high scan density. [Brief explanation of the drawings]

[0060] [Figure 1] 1 shows a detailed cross-section of the human eye. [Figure 2] It shows a detailed cross-section of a human eye with a classic gonioscopy lens in place, showing the light path through the lens and external equipment casting a shadow on the actual iridocorneal angle being examined. [Figure 3] Detailed cross-section of a human eye, where the light of the OCT device penetrates to obtain the iridocorneal angle from the virtual camera plane, showing the structures at the iridocorneal angle and the cross-section through the virtual camera, showing the shadow of external equipment on the iris that is not involved in the surgery. [Figure 4] 1 shows a top view of the anterior segment structures, with possible target volume projections and possible camera plane selections shown. [Figure 5]Figures 5 and 6 show two visualizations of the same OCT volume image based on two virtual gonioscopy views, each showing specific details of the iridocorneal angle. [Figure 6] Figures 5 and 6 show two visualizations of the same OCT volume image based on two virtual gonioscopy views, each showing specific details of the iridocorneal angle. DETAILED DESCRIPTION OF THE INVENTION

[0061] FIG. 1 shows a detailed cross-sectional view of a human eye 1, in which the cornea 2 and iris 3 form a structure in the anterior chamber of the eye. This structure is called the iridocorneal angle 4. Aqueous humor, shown here by a dotted line, drains from the iridocorneal angle 4. The so-called Schlemm's canal 5 runs circularly in the scleral portion, or region, of the iridocorneal angle 4, forming a collecting or drainage canal for aqueous humor. Also shown in FIG. 1 are the lens 6, trabecular meshwork 7, sclera 8, and ciliary body 9.

[0062] 2 shows that a gonioscopy lens 10 is placed on the cornea 2. The structures at the iridocorneal angle 4 of the eye 1 cannot be seen directly without technical assistance due to the refractive conditions at the cornea 2. To visualize said structures, a gonioscopy lens 10 is currently used that is in direct contact with the cornea 2 and avoids refraction at its anterior surface. Currently, surgery is performed exclusively with this gonioscopy lens 10.

[0063] However, the optical path 11 of the gonioscopy lens 10 casts a shadow of the device 12 onto the relevant structures of the iridocorneal angle 4, namely Schlemm's canal 5 and trabecular meshwork 7. The iridocorneal angle 4 itself is largely in the shadow of the device 12.

[0064] 3 shows how a three-dimensional volume 14 of a sample, i.e. a human eye 1, can be obtained as a raw data set by optical coherence tomography (OCT) using an apparatus 13 for performing gonioscopy. The apparatus is equipped with a visualization unit 15 that can be used to generate a virtual gonioscopy view 15a from the raw data set, which appears to be taken from a virtual camera plane 16 located inside the sample, here the eye 1. The virtual gonioscopy view 15a is displayed on a monitor of the apparatus 13.

[0065] The OCT optical path 17 of the device 13 does not cast a shadow of the device 12 onto Schlemm's canal 5 and trabecular meshwork 7, which are relevant structures of the iridocorneal angle 4. Instead, the shadow of the device 12 is cast onto the iris 3, which is not involved in the surgery. In Figure 4, compared to Figure 3, the gonioscopy lens 10 is not used, but rather the device 13, i.e., the OCT device.

[0066] A visualization unit 15 of the device 13 renders an image of the 3D volume 14, i.e., treats it as a raw data set, and uses this raw data set to generate a virtual gonioscopy view 15a from a virtual camera plane 16. The real camera plane 18 and the virtual camera plane 16 subtend an angle 19 ranging from 80° to 140°.

[0067] 4 shows schematically that at least one volume 14 can be imaged by a detection unit 20 along a circular arc section, preferably over an angular range 23 of 10° to 120°. Shown in FIG. 4 are the pupil 21, the limbus 22, the circular angular range 23 for imaging, the virtual camera plane 16, and the camera center 24. Multiple volumes 14 can be imaged consecutively in time and obtained as raw data sets. The arc sections are part of ring segments 25.

[0068] By means of the visualization unit 14, external instruments 12 for surgery on the eye 1 can be displayed transparently in the virtual gonioscopy display 15a or optically removed therefrom.

[0069] A tracking unit 26 is provided that can follow the movement of the sample with light for performing optical coherence tomography on the volume 14. An adjustment unit 27 is also provided, which can be used to automatically determine and define the virtual camera plane 16 based on the structure of the sample. The adjustment unit 27 is manually operable so that the position and orientation of the virtual camera plane 16 can be set under user control.

[0070] The volume 14 can be imaged at a repetition rate ranging from 1 Hz to 1 kHz. The latency before the virtual gonioscopy display 15a can be displayed is less than 500 ms.

[0071] The apparatus 13 described herein implements a method for performing virtual gonioscopy that uses an apparatus 13 for performing optical coherence tomography rather than a gonioscopy lens 10. In this regard, an apparatus 13 of the type described above can be used to perform the method.

[0072] This method will be explained briefly with reference to Figures 3 to 6. - illuminating the eye 1 from a real camera plane 18 by optical coherence tomography and acquiring a three-dimensional volume 14 of the eye 1 from the real camera plane 18 as a raw data set; generating a virtual gonioscopy display 15a from the raw data set, the virtual gonioscopy display 15a arising from a virtual camera plane 16 located within the eye 1 and allowing a top view of the structures of the eye 1; displaying the structure of the iridocorneal angle 4 of the eye 1 in a virtual gonioscopy display 15a; Includes.

[0073] 5 and 6 show two visualizations of the same OCT volume image of volume 14, thus showing details of the iridocorneal angle in each case. When observing these two visualizations, it should be taken into account that the cross-sectional images are shown exactly through the mechanical axis of device 12. In the gonioscopy en face view, only part of the view is obscured by the shadow of device 12.

[0074] The structures include Schlemm's canal 5, the ciliary body band, the scleral band, the trabecular meshwork 7, and / or Schwalbe's lines.

[0075] The volume 14 is projected onto a virtual camera plane 16 such that the projected image resembles the view through the gonioscopy lens 10, thereby forming a virtual gonioscopy view 15a.

[0076] The volume 14 is imaged over an angular range 23 of 10° to 120° along the path of the annulus 22, as shown schematically in FIG.

[0077] The method is performed intraoperatively, particularly during glaucoma surgical intervention. [Explanation of symbols]

[0078] 1 eye 2 Cornea 3. Iris 4 Iris corneal angle 5 Schlemm's canal 6 crystalline lens 7 Trabecular Meshwork 8. Sclera 9 Ciliary body 10 Gonioscopy Lenses 11 Gonioscopy lens optical path 12 Equipment 13 Equipment 14 in 1 volume 15 Visualization Unit 15a Virtual Gonioscopy Display 16 Virtual Camera Plane 17 OCT optical path of the device 17 18 Real Camera Plane 19 angle 20 Detection Unit 21 Pupil 22 limbus 23 Angle Range 24 Camera-centric 25 ring segments 26 Follower Unit 27 Adjustment Unit

Claims

1. 1. An apparatus (13) for performing gonioscopy, capable of acquiring a three-dimensional volume (14) of a sample as a raw data set by optical coherence tomography, characterized in that it comprises a visualization unit (15) capable of generating from the raw data set a virtual gonioscopy view (15a) that appears to be taken from a virtual camera plane (16) located inside the sample.

2. 2. The apparatus of claim 1, wherein the visualization unit (15) renders an image of the three-dimensional volume (14), i.e., treats it as a raw data set, and uses the raw data set to generate the virtual gonioscopy view (15a) from the virtual camera plane (16).

3. 3. The device according to claim 1 or 2, characterized in that the real camera plane (18) and the virtual camera plane (16) subtend an angle (19) ranging from 80° to 140°, and preferably both camera planes (16, 18) are oriented orthogonal to each other.

4. 3. The device according to claim 1, wherein at least one volume (14) can be imaged by the detection unit (20) along an arc section, preferably over an angular range (23) of 10° to 120°.

5. 3. Apparatus according to claim 1 or 2, characterized in that a plurality of volumes (14) can be acquired successively in time and acquired as raw data sets.

6. 5. Device according to claim 4, characterized in that the arc section is part of a ring segment (25) or part of a spiral, in particular an elliptical spiral.

7. 3. The device according to claim 1 or 2, characterized in that the visualization unit (15) allows external instruments (12) for the operation of the sample to be displayed transparently in the virtual gonioscopy display (15a) or to be optically removed therefrom.

8. 3. The device according to claim 1 or 2, characterized in that it comprises a tracking unit (26) capable of tracking the light for performing the optical coherence tomography along the volume (14) of movement of the sample.

9. 3. The device according to claim 1 or 2, characterized in that it comprises an adjustment unit (27) by means of which the virtual camera plane (16) can be determined and defined automatically based on the structure of the sample and / or the adjustment unit (27) is manually operable so that the position and orientation of the virtual camera plane (16) can be set under user control.

10. 3. The device according to claim 1 or 2, characterized in that the volume (14) can be imaged at a repetition rate in the range of 1 Hz to 1 kHz and / or the latency before the virtual gonioscopy display (15a) can be displayed is less than 500 ms.

11. 1. A method for performing virtual gonioscopy using a device (13) for performing optical coherence tomography, in particular a device according to claim 1 or 2, rather than a gonioscopy lens (10), comprising: - illuminating the eye (1) from a real camera plane (18) by optical coherence tomography and acquiring a three-dimensional volume (14) of said eye (1) from said real camera plane (18) as a raw data set; generating a virtual gonioscopy display (15a) from said raw data set, said virtual gonioscopy display (15a) arising from a virtual camera plane (16) located within said eye (1) and allowing a top view of the structures of said eye (1); displaying the structures of the iridocorneal angle (4) of said eye (1) in said virtual gonioscopy display (15a); A method comprising:

12. 12. The method of claim 11, wherein the structures include Schlemm's canal (5), the ciliary body band, the scleral band, the trabecular meshwork (7), and / or Schwalbe's wire.

13. 12. The method of claim 11, wherein the imaging of the volume (14) is performed over an angular range (23) of 10° to 120° along the path of the annulus (22).

14. 12. The method of claim 11, wherein the volume (14) is projected onto the virtual camera plane (16) such that the projected image resembles a view through a gonioscopy lens (10) to form the virtual gonioscopy view (15a).

15. 12. The method according to claim 11, characterized in that it is performed intraoperatively, in particular during a glaucoma surgical intervention.

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