Apparatus for examining the retina of an eye

Abstract

The invention relates to an apparatus for examining the retina (10) of an eye (7), comprising an OCT device (2) for recording OCT images (14) by means of optical coherence tomography (OCT) and a further device (4) for recording further images (13) of the retina (10), characterized in that a data processing unit (18) uniquely assigns an OCT image (14) to at least one further image (13) and uses structures (17) of the retina (10) captured both in the OCT image (14) and the further image (13) as calibration targets for the OCT device (2) and the further device (4).

Description

[0001] Patent application

[0002] Device for examining the retina of an eye

[0003] The invention relates to a device according to the preamble of claim 1.

[0004] Optical coherence tomography (OCT) is an imaging technique that can be used to create two- and three-dimensional images of light-scattering structures. This method typically involves splitting light with a specific bandwidth into two beams using a beam splitter. The first beam falls on the sample or object to be examined, while the second beam travels through a reference path. The light reflected from the sample or object interferes with the reference beam. Signals from the interference allow the sample to be examined with depth resolution, i.e., at the depth of the optical axis of the first beam, using A-scans. It is also possible to scan the sample flatly or laterally with the first beam to obtain OCT images. A B-scan is made up of multiple A-scans.

[0005] In the field of intraoperative OCT, it is of utmost importance that an OCT scan position for obtaining an OCT image and, in particular, a microscope image can be clearly assigned to each other. This assignment is typically achieved using calibration targets that are recognizable in both modalities or image categories. Both image categories visualize the calibration target, and a suitable coordinate transformation is determined that governs the assignment of scan points for an OCT image to pixels for a microscope image.

[0006] This calibration assumes that there are no additional optical elements in a system that affect the two image categories differently. However, this is often the case in retinal imaging.

[0007] To image the retina of an eye, an additional lens (e.g., the Oculus BIOM (brand name)) is pivoted into a beam path, creating an image to infinity. The refractive elements of the eye being examined then focus rays through the lens as close to the retina as possible.

[0008] The non-collinearity of an OCT beam or OCT beam path with the imaging beam path of a microscope results in a shift of pixels in the two image categories. This shift varies in different eyes due to individual refraction. The surgical-specific configuration of an additional optic, for example, the focus position of a magnifying glass in the Oculus BIOM and the relative eye position, has a similar influence.

[0009] Furthermore, individual chromatic aberrations in an eye, even with collinearity of the aforementioned optical paths, shift the image points on the retina. For these reasons, an imaging system cannot be calibrated across the board. Without individual calibration, misinterpretations can occur during surgery.

[0010] The invention is therefore based on the object of specifying a device by means of which both OCT images and other images can be generated which depict or capture the same area to be examined as accurately as possible and without optical offset relative to one another.

[0011] The present invention solves the aforementioned problem by the features of claim 1. According to the invention, a device for examining the retina of an eye comprises an OCT device for acquiring OCT images using optical coherence tomography and a further device for acquiring images of the retina. Furthermore, according to the invention, a data processing unit uniquely assigns an OCT image to at least one further image and uses retinal structures captured by both the OCT image and the further image as calibration targets for the OCT device and the further device.

[0012] According to the invention, it was initially recognized that there is a need, particularly during a surgery, for an individual, preferably continuous, calibration of an OCT scan position with respect to another image, for example, a microscope image. It was then recognized that by using the aforementioned structures, an individual calibration is possible, which can override a blanket calibration, at least temporarily. This ensures that the scan position and the other image are displayed correctly. The images capture or depict the same area to be examined with as much detail as possible and without any optical offset relative to each other.

[0013] According to the invention, it has been recognized in particular that the previously known intraoperative OCT systems do not adequately address the following problem: the problem of the scan position in the retinal region not being clearly assigned to the subsequent image, namely a microscope image. The technical solution described here makes it possible to perform OCT scans at precisely defined positions.

[0014] With this in mind, the data processing unit could use the positions of the structures in the OCT image and the other image to align the scan coordinates of the OCT image with the corresponding pixel coordinates of the other image. This allows characteristic structures to be precisely used as calibration targets.

[0015] The data processing unit could use the scan coordinates of the OCT image and the

[0016] Pixel coordinates of the rest of the image are converted into one another through coordinate transformation. This allows different elements representing an area to be placed on top of or next to each other and analyzed.

[0017] The OCT image could be designed as an en-face image, generated from an OCT volumetric scan of the eye tissue. Especially during surgery, an en-face OCT image, i.e., an OCT cross-sectional image, allows this image to be registered with the other images from the other device.

[0018] This maps the pixels and scan coordinates to each other. This makes individual calibration particularly effective. This individual calibration then temporarily overwrites a blanket calibration. This ensures that the scan position and a subsequent image are displayed correctly.

[0019] The OCT volume scan could be stored in a data storage device. This allows access to the OCT volume scan at any time. An en-face image provides cross-sectional views of the tissue. Depending on the size, acquiring an en-face image or an en-face scan takes a significant amount of time. Therefore, it is advantageous to use a particularly fast OCT system. A-scan rates in the MHz range are particularly preferred here. Particularly fast scanners and fast scanner control are also preferred. Closed scan patterns, such as a spiral, can further increase scan efficiency, allowing for quasi-continuous recalibration at specific intervals if necessary.

[0020] The data processing unit and / or a control unit could align the scan position or acquisition position of the OCT image on the retina with that of the other image, preferably simultaneously, so that any optical offset of the beam paths of the OCT device and the other device is compensated for by additional optical components and / or the refractive behavior of the examined eye. This allows optical-mechanical influences to be compensated electronically and thus quickly.

[0021] The data processing unit and / or the control unit could periodically align the scan position or acquisition position of the OCT image on the retina with that of the other image. This allows calibration to be adapted to changing acquisition conditions. Surgery can be performed reliably over an extended period because the device recalibrates itself automatically and / or at predefined time intervals.

[0022] The OCT image could not be visualized. Alternatively or additionally, the OCT image could be configured as an image dataset. This makes it possible to visualize only the remaining image for analysis, while using the OCT image data only for calibration purposes.

[0023] The additional image could be a fundus image. The additional device could therefore include an SLO (scanning laser ophthalmoscope) or a fundus camera.

[0024] The further device could be designed as a microscope, particularly a surgical microscope, and the further image as a microscopic image. This allows highly magnified images of areas of the retina to be taken.

[0025] Posterior segment imaging using OCT in a surgical microscope is an important addition to existing OCT systems. Posterior segment procedures, which rely on high positioning accuracy, play a major role in ophthalmic surgery.

[0026] The device described here could also be used for high-precision subretinal injection, particularly in gene therapy for the treatment of retinal diseases. For this purpose, it is essential to align the OCT image or OCT cross-sectional image with the injection needle in order to observe the injection volume. This can reduce the administered volume of the very expensive drug, leading to significant cost savings.

[0027] An arrangement could comprise a device of the type described here and additional optical components for examining the retina of an eye. The drawing shows

[0028] Fig. 1 shows a schematic diagram of the beam paths of an OCT device and a microscope, and

[0029] Fig. 2 in the upper view on the left a microscope image and on the right an en face image taken with an OCT device, which are registered to each other by a process step shown schematically in the middle and are transformed by a process step shown schematically.

[0030] Fig. 1 shows a non-collinearity of an OCT beam path 1 of an OCT device 2 relative to the imaging beam path 3 of another device 4, here specifically a microscope, which causes an offset of the image points 5, 6 in the image categories OCT image 14 and another image 13, namely microscope image.

[0031] This offset is caused, among other things, by the individual refraction of the eye 7 to be examined, in particular by its eye lens 8.

[0032] Another influence is the operation-specific configuration of an additional optic, namely the focus position of a magnifying glass 9 and the relative eye position.

[0033] Furthermore, the individual chromatic aberrations of the eye 7, even assuming collinearity of the two beam paths 1, 3, shift the image points 5, 6 on the retina 10.

[0034] The device, which comprises the OCT device 2 and the microscope, is assigned a front lens 11 and a reducing lens 12.

[0035] Fig. 1 schematically shows a device for examining the retina 10 of an eye 7, comprising an OCT device 2 for recording OCT images 14 by means of optical coherence tomography (OCT) and a further device 4 for recording further images 13 of the retina 10. Such images are shown in Fig. 2. The further device 4 is designed as a microscope, in particular a surgical microscope, and the further image 13 is designed as a microscope image.

[0036] Fig. 2 schematically shows that, in addition to continuous microscope images 13, a single OCT volume is acquired, from which an OCT image 14, namely an en face image, is generated. The OCT image 14 is configured as an en face image, which is generated from an OCT volume image of the tissue of the eye 7. The OCT volume image is stored in a data storage device. This OCT image 14 is not necessarily used for visualization, but preferably or only for registration 15. The OCT image 14 is therefore preferably not visualized and configured as an image data set.

[0037] In the en face view, some of the same structures 17 appear as in the microscope image 13. This allows for use for registration 15. Using known registration methods, a transformation of images 13 and 14 can be found and applied. This transformation aligns the structures 17 of the two image categories.

[0038] This transformation is not only valid for the en face image, but generally describes the transformation of the scan coordinates to the corresponding pixel coordinates of the microscope. This opens up possibilities, such as the correct positioning of a B-scan as it should be performed in the microscope image or based on the microscope image.

[0039] Fig. 1 and 2 therefore schematically show that a data processing unit 18 uniquely assigns an OCT image 14 to at least one image 13 and uses structures 17 of the retina 10, which are captured by both the OCT image 14 and the image 13, as calibration targets for the OCT device 2 and the further device 4.

[0040] Based on the positions of the structures 17 in the images 13, 14, the data processing unit 18 matches the scan coordinates of the OCT image 14 with the corresponding pixel coordinates of the image 13. The data processing unit 18 converts the scan coordinates of the OCT image 14 and the pixel coordinates of the image 13 into one another through coordinate transformation.

[0041] The data processing unit 18 and a control unit 19 align the scanning position or acquisition position of the OCT image 14 on the retina 10 with that of the image 13, preferably simultaneously, so that an optical offset of the beam paths 1, 3 of the OCT device 2 and the further device 4 is compensated by additional optical components and / or refractive behavior of the examined eye 7.

[0042] The data processing unit 18 and the control unit 19 periodically align the scanning position or acquisition position of the OCT image 14 on the retina 10 with that of the image 13 in order to adapt a calibration to changing recording conditions.

[0043] Fig. 1 also shows an arrangement comprising a device of the type described here and additional optical components for examining the retina

[0044] 10 of an eye 7. The additional components include a magnifying glass 9, a frontal lens

[0045] 11 and a reducing lens 12.

[0046] List of reference symbols:

[0047] 1 OCT beam path

[0048] 2 OCT device

[0049] 3 imaging beam path of 4

[0050] 4 additional equipment, here specifically microscope

[0051] 5 pixels of 1

[0052] 6 pixels out of 3

[0053] 7 Eye

[0054] 8 eye lens

[0055] 9 Magnifying glass

[0056] 10 Retina

[0057] 11 Frontal lens

[0058] 12 reducing lens

[0059] 13 further picture, here specifically microscope image

[0060] 14 OCT image or en face image

[0061] 15 Registration

[0062] 16 Transformation

[0063] 17 structures out of 10

Claims

Patent claims 1. A device for examining the retina (10) of an eye (7), comprising an OCT device (2) for recording OCT images (14) by means of optical coherence tomography (OCT) and a further device (4) for recording further images (13) of the retina (10), characterized in that a data processing unit (18) uniquely assigns an OCT image (14) to at least one further image (13) and uses structures (17) of the retina (10) that are captured by both the OCT image (14) and the further image (13) as calibration targets for the OCT device (2) and the further device (4).

2. Device according to claim 1, characterized in that the data processing unit (18) matches the scan coordinates of the OCT image (14) with the corresponding pixel coordinates of the further image (13) on the basis of the positions of the structures (17) in the images (13, 14).

3. Device according to claim 1 or 2, characterized in that the data processing unit (18) converts the scan coordinates of the OCT image (14) and the pixel coordinates of the further image (13) into one another by coordinate transformation.

4. Device according to one of the preceding claims, characterized in that the OCT image (14) is designed as an en face image which is generated from an OCT volume image of the tissue of the eye (7).

5. Device according to claim 4, characterized in that the OCT volume recording is stored in a data memory.

6. Device according to one of the preceding claims, characterized in that the data processing unit (18) and / or a control unit (19) brings or bring the scanning position or detection position of the OCT image (14) on the retina (10) into line with that of the further image (13), preferably simultaneously, so that an optical offset of the beam paths (1, 3) of the OCT device (2) and the further device (4) is compensated by additional optical components and / or refractive behavior of the examined eye (7).

7. Device according to one of the preceding claims, characterized in that the data processing unit (18) and / or a control unit (19) brings or brings the scanning position or detection position of the OCT image (14) on the retina (10) into line with that of the further image (13) in periodic repetition in order to adapt a calibration to changing recording conditions.

8. Device according to one of the preceding claims, characterized in that the OCT image (14) is not visualized and / or is designed as an image data set.

9. Device according to one of the preceding claims, characterized in that the further device (4) is designed as a microscope and the further image (13) is designed as a microscope image.

10. Arrangement comprising a device according to one of the preceding claims and additional optical components for examining the retina (10) of an eye (7).

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