DEVICE AND METHOD FOR DISPLAYING THE ASTIGMATISM AXIS OF THE EYE

Description

[0001] In eye surgery, it is important to know the precise orientation and position of the eye, with a particularly accurate understanding of the eye's torsion being crucial. This includes, for example, laser-assisted in situ keratomileusis (LASIK) or the use of toric intraocular lenses in cataract surgery to correct astigmatism.

[0002] Toric intraocular lenses, or TIOLs for short, do not have a spherical geometry. They are characterized by a maximum and a minimum curvature (principal curvatures) along two mutually perpendicular meridians through the apex. The direction of greatest curvature is indicated by markings on the TIOL surface, the design of which varies from manufacturer to manufacturer.

[0003] The optimal torsional orientation of the two main curvature directions of the TIOL is patient-specific and depends on the orientation or direction of the eye's corneal astigmatism axis. Complete compensation of the astigmatism is achieved when the physician aligns the direction indicated by markings or surface markings on the TIOL with the eye's astigmatism axis.

[0004] Consequently, for the success of the operation, it is crucial to know the exact position of the patient's astigmatism axis during the implantation of the TIOL and to present this information to the doctor.

[0005] For performing eye surgery, a guidance system is attached to the operating microscope, which provides the doctor with detailed data about the eye, such as its orientation and position relative to the microscope or operating microscope.

[0006] Intraoperative display of the eye's astigmatism axis during surgery helps the doctor to insert toric intraocular lenses or TIOLs that compensate for astigmatism or astigmatic refractive error of the eye's cornea.

[0007] Several methods are known to be used for this purpose. These can be divided into manual methods, image processing methods, and measurement methods.

[0008] In the most common manual methods, the patient's astigmatism axis is determined preoperatively during diagnosis using, for example, a keratograph, and recorded as an angle to the horizontal. On the day of surgery, the patient, in a seated position, has the orientation of the astigmatism axis, or axis orientation, manually marked on the surface of the eye with a stamp. During the operation, this marking is visible through the eyepiece of the operating microscope and can be used by the surgeon as a guide for lens implantation.

[0009] However, these methods have the disadvantage that the visibility of the marking can decrease over time, which can be caused, for example, by rinsing procedures during surgery. Furthermore, the accuracy of the marking's angular orientation can suffer due to the manual nature of the application, often leading to inaccuracies. In addition, the head orientation during marking application may differ from the head orientation during diagnosis, resulting in an offset error.

[0010] In image processing-based methods, a reference image of the eye is simultaneously captured and stored using a camera during the diagnostic determination of the astigmatism axis. The scleral blood vessels visible in the image, or the iris pattern, are automatically searched for in current intraoperative images from the operating microscope's camera with the aid of a computer unit. This allows the relative rotation of the eye around the viewing direction between the time of diagnosis and surgery to be determined using matching and registration algorithms. Once this rotation or torsion is determined, the current intraoperative orientation of the astigmatism axis, calculated as the sum of the angles of the orientation during diagnosis and the torsion, can be incorporated into the microscope's optical path, thus serving as a guide for the surgeon.

[0011] However, this approach has several disadvantages. Firstly, the absence of prominent blood vessels and iris structures can prevent image processing algorithms from adequately determining torsion, or even from doing so at all. In this case, determining the current astigmatism axis is impossible. Furthermore, bleeding during surgery can prevent scleral blood vessels, which are clearly visible during diagnosis, from being detected in the current surgical image. This makes it impossible to register prominent vascular structures between the diagnostic image and the current surgical image, and the current astigmatism axis cannot be determined. If the orientation of the microscope and its associated camera is changed intraoperatively, for example, rotated around the viewing direction, a recalculation of the torsion is necessary to display the correct target orientation of the TIOL to be implanted.This procedure absolutely requires a reference image at the time of diagnosis, which is not provided by all diagnostic devices.

[0012] The third group, measurement methods, includes newer techniques that do not require reference images from the diagnostic procedure, as the position or orientation of the astigmatism axis is directly measured again intraoperatively while the patient is already in a supine position. One such method is disclosed in publication WO2015176699A2, in which the astigmatism of the corneal surface is measured using a camera and an illumination unit. This eliminates the need for image processing to register a correlation between a diagnostic image and a current intraoperative image from the operating microscope camera. The disadvantages of the previously described methods are eliminated, as the result does not depend on the accuracy of manually applied markings or on the simultaneous presence and quality of prominent structures in the diagnostic and surgical images.

[0013] Other well-known measurement methods use wavefront aberrometry to determine the astigmatism of the eye.

[0014] US 2011 / 157553 A1 describes a surgical microscope system with optics for generating an image of the eye during eye surgery. Images of the eye are captured with a camera. An eye tracker analyzes the images received by the camera. A pattern generator overlays a pattern onto the image displayed on a screen. The pattern moves along with the image of the eye.

[0015] WO 2012 / 041349 A1 discloses an arrangement for performing surgical treatment of an eye, comprising a diagnostic device configured to acquire ocular structure data. A data processing unit is configured to generate a structural image based on the ocular structure data acquired by the diagnostic device, containing at least one image of a characteristic ocular structure and at least one position marker arranged relative to the image of the characteristic ocular structure. An image data overlay device is configured to overlay the structural image generated by the data processing unit onto an image produced by an operating microscope during the performance of surgical treatment of the eye.

[0016] US 2011 / 0019151 A1 describes an ophthalmic surgical microscopy system comprising an imaging optic for generating an image of an object plane and an electronic image sensor that captures the image of the object plane and is connected to a processing unit for calculating the position of the center of a circular structure of a patient's eye. The processing unit is designed to calculate the position of the patient's eye outside the center of the circular structure and is equipped with at least one marker. Using image processing, the processing unit determines the position of the at least one marker relative to the calculated center by correlating it with comparative information, and also uses image processing to determine the angular position of the at least one marker relative to the calculated center.

[0017] US 2011 / 230751 A1 discloses an image processing system for computer-assisted eye surgery, comprising the acquisition of a reference image of the eye and the enrichment of the reference image by inserting additional contextual information that assists the surgeon in performing the eye surgery. The reference image is registered with a real-time image of the eye. The contextual information is overlaid on the real-time image of the eye based on tracking of eye movement, so that the contextual information is displayed in the same position despite eye movement.

[0018] US 2015 / 077528 A1 discloses a surgical guidance system to assist a surgeon during a surgical procedure on a patient. The system includes an image acquisition device configured to generate essentially real-time digital video data representing patient images from one of the patient's eyes. The system further includes a processor coupled to the image acquisition device and configured to receive the digital video data from the image acquisition device, receive external data from an external data source, and generate composite digital image data based on the digital video data and the external data.The system further includes a display device coupled to the processor, the display device being configured to show the surgeon superimposed images from the composite digital image data with procedural prompts corresponding to the patient images and the external data.

[0019] The publication BRUNA V. VENTURA ET AL: "Surgical management of astigmatism with toric intraocular lenses", ARQUIVOS BRASILEIROS DE OFTALMOLOGIA, Vol. 77, No. 2, pages 125-131, describes an ophthalmic operating microscope in which an astigmatism axis is continuously updated in real time during an operation by means of intraoperative eye tracking as a superimposed image.

[0020] However, it is possible that the surgeon may change the orientation of the microscope or microscope camera. After such a change, the operation can no longer be continued with the same coordinates regarding the axis of astigmatism, or errors may occur concerning the orientation of the TIOL. In this case, a new measurement of the astigmatism axis is necessary so that the target orientation of the TIOL to be implanted can be displayed correctly.

[0021] US 2008 / 204864 A1 describes a microscope device with position sensing, used to determine the position of the microscope in space. The device includes a microscope and an accelerometer to detect the three-dimensional position of the microscope. The acquired data is used to determine the position of the microscope and display it in a manner similar to a navigation system. Additional accelerometers may be included for redundancy.

[0022] In practice, changes in the microscope's orientation during surgery cannot be ruled out, necessitating continuous processing or measurement of the astigmatism axis in image processing procedures. Various factors, such as occlusions, corneal reflections, foreign objects, bleeding, etc., can distort the calculated or measured results regarding the astigmatism axis.

[0023] If the astigmatism axis is measured intraoperatively and before any procedure, with the patient in a supine position, it can be assumed that the measured astigmatism axis physically corresponds to the axis determined during diagnosis. A further difficulty arises from the fact that some surgical steps can temporarily or permanently alter the orientation of the astigmatism axis, for example, when mechanical pressure is applied to the eye or incisions are made at the limbus to open the anterior chamber. Consequently, subsequent measurements of the astigmatism axis no longer reproduce the original, i.e., preoperative, axis. As a result, the target orientation of the implanted TIOL is no longer correctly indicated.

[0024] The object of the invention is to display the orientation of the astigmatism axis in the image of the eye more quickly, accurately and robustly during the operation, in order to provide correct information about the position or orientation of the axis of the astigmatism to be corrected at all times.

[0025] In particular, errors arising from changes in the operating microscope's orientation during surgery and from changes in the astigmatism axis caused by certain surgical steps should be avoided. Both of these factors currently result in incorrect information about the orientation of the astigmatism axis being corrected later in the operation. Furthermore, the robustness of determining the current axis position should be improved.

[0026] The problem is solved by the device according to claim 1 and by the method according to claim 13. Further features and details are set out in the dependent claims, the description and the drawings.

[0027] The device according to the invention for displaying the astigmatism axis of the eye comprises an observation unit for observing the eye, a display unit for displaying the orientation of the astigmatism axis of the eye in an image of the eye, a sensor device for generating sensor data that characterizes a change in the orientation of the observation unit relative to the eye, and a computing unit, wherein the sensor device comprises at least one rotation rate sensor attached to the observation unit to detect a rotation angle of the observation unit about its observation direction, and the computing unit is configured toUsing the sensor data from the rotation rate sensor, the current orientation of the astigmatism axis in the image of the eye is calculated from the orientation of the astigmatism axis in the image of the eye at a first time point and from the rotation angle of the observation unit around its observation direction at the first time point and at a current second time point, and is made available to the display unit for display in the current image of the eye.

[0028] This ensures that if the orientation of the observation unit relative to the eye changes, particularly if it is rotated around the observation direction, the operation can continue with correct data. Specifically, after a change in the orientation of the observation unit, the orientation of the eye's actual astigmatism axis continues to be displayed correctly.

[0029] A further advantage is that a diagnostic image is not required. Even if the orientation of the astigmatism axis changes due to surgical steps, the orientation of the preoperative astigmatism axis or the target orientation of the TIOL to be implanted can always be correctly specified.

[0030] Furthermore, the robustness of determining the current axis position is increased. While direct measurements and image processing can be subject to errors and inaccuracies due to occlusions, foreign objects, rinsing processes, etc., the solution according to the invention offers the advantage of being completely insensitive to such influences, since, for example, only the movement of the microscope is measured.

[0031] Advantageously, the observation unit includes an operating microscope or is designed as an operating microscope.

[0032] In particular, the observation unit may include a camera for recording images of the eye or be designed as a camera.

[0033] Advantageously, the display unit includes a display or is designed as a display.

[0034] Preferably, the display unit comprises a mirror arrangement for reflecting the axis position or orientation of the astigmatism axis into the beam path of the observation unit or the operating microscope. The display unit can, in particular, be designed as a display including a mirror arrangement for reflection into the beam path of the observation unit or the operating microscope. In particular, relatively small displays, e.g., in the size of 2" to 3", can be used. However, other display technologies can also be employed.

[0035] Advantageously, a memory is provided to store a value or reference value that represents the orientation of the eye's astigmatism axis at an initial point in time. This value thus characterizes the orientation of the astigmatism axis that is to be corrected by the operation and is displayed in the image. In particular, the angular position of the astigmatism axis is stored as the reference value.

[0036] Since surgical procedures often alter astigmatism, the angle of the measured astigmatism axis before such procedures is stored as a reference value representing the reference orientation of the astigmatism axis. This ensures that astigmatism-altering surgical procedures do not distort the displayed orientation of the astigmatism axis being corrected.

[0037] In particular, the memory also serves to store a reference orientation of the observation unit, i.e., the microscope or camera. Thus, the orientation of the observation unit, microscope, and / or camera that was valid at the time of the reference measurement of the astigmatism axis orientation can be stored. Subsequently calculated microscope or camera orientations can then refer to this stored orientation of the observation unit as a reference orientation.

[0038] In particular, by determining the orientation of the astigmatism axis with an initial measurement or reference measurement, and subsequently evaluating the sensor signals to determine the change in orientation of the operating microscope or observation unit compared to its orientation during the reference measurement, increased robustness and lower susceptibility to error are achieved in calculating the current orientation of the astigmatism axis in the image of the eye compared to astigmatism measurement methods or the application of image processing algorithms, whose accuracy or success in registering (or matching) diagnostic images and current camera images can be negatively affected by image quality, the presence of occlusions and foreign objects, such as surgical instruments, bleeding, etc.

[0039] Compared to measuring systems, this offers the same advantage, since their results are also based on the evaluation of camera images. Therefore, any influences on the eye's image or its visibility can have a negative impact.

[0040] A further advantage is that the calculation time with the proposed sensor-based solution is considerably shorter due to its much lower complexity, resulting in reduced latency in displaying the current astigmatism axis. Furthermore, the eye illumination after the reference measurement can be drastically reduced, leading to increased patient comfort.

[0041] Preferably, the sensor device determines not only the rotation of the observation unit around its observation direction but also its position during operation. In particular, the sensor device can be used to determine both the rotation and the position of the observation unit. The sensor device measures the rotation angle of the operating microscope or the observation unit around the observation direction or around the optical axis of the operating microscope.

[0042] Preferably, the sensor device measures angular velocities, from which, with continuous monitoring and appropriate positioning on the microscope or the observation unit, for example its rotation around the observation direction relative to the reference measurement can be derived.

[0043] Advantageously, the sensor system includes, in addition to one or more rotation rate sensors, such as gyroscope sensors, one or more inertial measurement units (IMUs), which also contain, for example, the gyroscope sensors. These sensors can also be combined with each other. In particular, this enables the calculation of the relative position or orientation of the microscope or microscope camera with respect to a reference orientation.

[0044] Preferably, the sensor device comprises one or more accelerometers, compass sensors, or direction sensors, which can also be combined with each other. This simplifies or improves the calculation of the orientation and position of the observation unit, in particular the microscope or its components. Errors, such as drift in the data, are reduced or even eliminated.

[0045] Advantageously, the sensor device comprises sensors that measure the adjustment of the joints of the observation unit or the operating microscope, using potentiometers or rotary encoders for this purpose. This provides a particularly simple method for measuring position, direction, or orientation, with these sensors, potentiometers, or rotary encoders preferably being arranged at the joints of the operating microscope and, more preferably, integrated into the joints.

[0046] In particular, the sensor device comprises one or more sensors for determining the orientation and / or position of the patient's head. Specifically, either the orientation or the orientation and position of the head is measured. Specifically, any rotation or twisting of the patient's head around the observation direction or around the optical axis of the observation unit or the operating microscope is measured.

[0047] The patient, or rather their head, can be tracked in position. This ensures that any rotation of the patient's head, and thus their eye, around the optical axis of the microscope camera or the observation direction is detected and taken into account by the processing unit. This means that a rotation of the patient's head does not distort the measurement result.

[0048] The term "observation direction" or "optical axis" refers in particular to the optical axis of the operating microscope or, more generally, the observation unit, which corresponds to the observation direction defined, for example, by the optical axis of the entrance optics of the operating microscope or the observation unit.

[0049] Furthermore, sensors can be provided, in particular, to measure the orientation and position of the operating table, which supports the patient during the operation and on which the patient, and especially their head, is fixed. These sensors can be arranged individually or in combination and designed as part of the overall sensor system. This prevents a distortion of the measurement results if the orientation of the patient table changes during the operation. This is particularly useful if a significant rotation of the head around the line of sight or the optical axis of the observation unit is physically impossible due to the way the patient is positioned.

[0050] Preferably, the alignment or position of the patient's bed, and thus also its location or orientation, is tracked using sensors.

[0051] In particular, a tracking device is provided which tracks the orientation and position of the observation unit, especially the operating microscope, and tracks the position, orientation, and location of the patient's head.

[0052] The orientation of the current astigmatism axis to be displayed is calculated in this case from the reference orientation of the astigmatism axis, the orientation of the microscope or camera relative to its orientation at the reference time, and the orientation of the head or the patient's bed, if the head is fixed to the bed, also relative to the reference time. The reference position of the head or the patient's bed is measured during the reference measurement of the astigmatism axis analogously to the determination of the reference position or reference orientation of the microscope.

[0053] The processing unit is preferably designed such that it determines the direction or orientation of the eye's astigmatism axis as the sum of the angles derived from the reference orientation or reference angle position of the astigmatism axis and the angular position of the operating microscope or camera relative to the optical axis, calculated by the sensor unit and relative to the angular position during the reference measurement. In other words, the sum of the angles is calculated from the angle of the astigmatism axis at the first measurement point (=reference orientation) and the angle of a subsequent rotation of the microscope or microscope camera around the observation direction, which is determined from the signals of the sensor device.

[0054] The inventive method for displaying the astigmatism axis of the eye comprises the steps of: providing an observation unit for observing the eye; providing the orientation of the astigmatism axis of the eye in an image of the eye for display on a display unit during observation of the eye; capturing and storing sensor data that characterizes a change in the orientation of the observation unit relative to the eye;wherein the rotation angle of the observation unit about its observation direction is detected, and using the sensor data of the rotation rate sensor, the current orientation of the astigmatism axis in the image of the eye is calculated from the orientation of the astigmatism axis in the image of the eye at a first time point and from the rotation angle of the observation unit about its observation direction at the first time point and at a current second time point, and is made available to the display unit for display in the current image of the eye;

[0055] Preferably, the orientation of the observation unit relative to the eye is determined at the first time point T1 and at the second time point T2, and the orientation of the astigmatism axis A of the eye at the second time point T2 is determined from the sensor data and displayed.

[0056] To determine the orientation of the astigmatism axis to be displayed at the second time point T2, the orientation of the astigmatism axis at the first time point T1 is used.

[0057] Advantageously, the orientation of the observation unit is monitored. In particular, the position and orientation of the operating microscope are tracked.

[0058] In particular, the rotation angle of an operating microscope around its observation direction or around its optical axis is determined in order to determine the orientation of the operating microscope or the microscope camera.

[0059] Advantageously, the orientation and / or position of the patient's head and / or a patient table on which the patient is fixed is measured in order to detect any rotation of the head around the observation direction or the optical axis of the observation unit and to use this information in calculating the current orientation of the astigmatism axis. The orientation of the patient's head and / or the patient table can also be tracked.

[0060] In particular, the current or currently calculated orientation of the astigmatism axis is displayed on a screen, advantageously in a current image of the eye, and / or it is superimposed into the beam path of an operating microscope. This allows it to be updated when the orientation of the operating microscope changes.

[0061] According to an aspect not covered by the invention, a method for displaying the astigmatism axis of the eye is shown, comprising the following steps: capturing images of the eye with an operating microscope and / or a camera; capturing a first measurement indicating the orientation of the astigmatism axis in the image of the eye at a first time point T1; capturing and storing the orientation of the operating microscope at the first time point; capturing the orientation of the operating microscope at a second time point T2; and displaying a corrected orientation of the astigmatism axis A of the eye in the image of the eye at the second time point T2, wherein the corrected orientation is determined from the first measurement and from the orientation of the operating microscope at the second time point T2 or from the change in orientation of the operating microscope compared to the orientation at time point T1.

[0062] Preferably, the first measurement is taken while the patient is in the operating position.

[0063] Advantageously, the first measurement is taken before any surgical steps are performed that alter the astigmatism axis.

[0064] The advantages and details described in connection with the device, which are explained in more detail below, also apply to the method according to the invention and vice versa.

[0065] The invention is described below using the figures as an example. They show: Figure 1 a schematic representation of a device according to the invention; Figure 2 an exemplary sensor arrangement with a computing unit and a display unit in a schematic representation; Figure 3A a field of view of a microscope, which schematically shows the eye and the astigmatism axis; Figure 3B the field of view according to Figure 3A, however, after a rotation of the operating microscope around the gravitational vector; Figure 3C the field of view according to Figure 3A , however, after a rotation of the patient's head or the operating table around the gravitational vector.

[0066] Figure 1 Figure 1 shows a preferred embodiment of the invention, a device 100 which serves to display the eye with its astigmatism axis during eye surgery. A microscope or operating microscope 10 serves as the observation unit for observing the eye 13 of a patient.

[0067] A camera is designed as an integrated component of the microscope head 10a and records images 12 of the eye 13 (see Figure 3A A display unit 11 serves to display the orientation R of the astigmatism axis A of the eye 13 in the displayed or recorded images 12 of the eye, which is captured by the operating microscope 10.

[0068] A sensor 20a enables the determination of the orientation or position of the operating microscope 10. The sensor 20a can be configured as an inertial measurement unit (IMU) and continuously measures accelerations and angular velocities in three degrees of freedom each. However, according to the invention, it can also be configured as a separate rotation rate sensor or gyroscope sensor.

[0069] Furthermore, a computing unit 30 is provided which calculates the current orientation R' of the astigmatism axis A in the respective current image 12 of the eye 13 (see Figures 3A to 3CAccording to the invention, the calculation is performed from the orientation R of the astigmatism axis A of the eye 13 at a first time point T1, and the respective orientation of the operating microscope 10, derivable from the sensor data, at the first time point T1 and at a second time point T2, which is the current time point. That is, from the originally correctly determined orientation of the astigmatism axis in image 12 of the eye 13 and the subsequent change in the orientation of the operating microscope 10, the orientation R' of the astigmatism axis in the current image of the eye is determined.

[0070] The computing unit 30 can consist of several components. For example, it could be one or more microcontrollers in combination with a PC. The microcontrollers read the sensors and forward the data either directly or after processing it to the PC, which performs the final calculations and transmits the results to the display unit.

[0071] The computing unit 30 is coupled to the display unit 11 in order to provide the display unit 11 with the current orientation R' of the astigmatism axis.

[0072] The operating microscope 10 comprises a holder 101 in the form of a carrying frame with several elements that are movable relative to each other and are movably connected by joints 10b. The central part of the operating microscope 10 is a microscope head 10a with the integrated camera, which is movably attached to the holder 101.

[0073] The operating microscope 10 has an eyepiece 14 through which the doctor views the magnified image of the patient's eye 13 during the operation.

[0074] Before and during the operation, the movable operating microscope 10 with its camera is aligned with the patient's eye 13. This direction forms the observation direction O and corresponds to the optical axis of the light entry optics of the operating microscope 10 as well as the camera integrated in the microscope head 10a.

[0075] The sensor 20a, attached to the microscope head 10a, measures changes in the position and / or orientation of the camera. This detects a rotation of the operating microscope 10 around the observation direction O. If the operating microscope 10 is directed vertically downwards towards the eye 13 of the supine patient, the observation direction O corresponds to the direction of the gravitational pulley g, which is in Figure 1 runs in the opposite direction to the Z-direction.

[0076] The sensor 20a, designed as an inertial measuring unit or, according to the invention, as a rotation rate or gyroscope sensor, measures the rotation or angular velocity, or, according to the invention, the rotation rate, of the camera and the microscope head 10a about the observation direction O, here i.e., about the Z-direction. With the aid of the processing unit 30, the relative angular position of the camera about the observation direction can be determined, for example.

[0077] In addition to the sensor 20a shown here, the preferred embodiment includes sensors 21 that measure the position of the joints 10b of the operating microscope 10. The sensors 21 are designed as potentiometers or rotary encoders and are located in the joints 10b of the operating microscope 10 or its mount 101. This allows for the detection of rotational movements of the components of the mount 101 relative to one another, from which the position and orientation of the operating microscope 10 or its camera 10a can be determined.

[0078] The sensors 21 for measuring the position of the joints 10b can be arranged additionally or alternatively to the one or more rotation rate or gyroscope sensors 20a.

[0079] The preferred embodiment of the invention presented here additionally comprises one or more sensors 22 attached to the patient's head 60, which measure or detect a rotation of the patient's head 60 about the observation direction O. The sensors 22 are preferably rotation rate or gyroscope sensors, or they are configured as inertial measurement units (IMUs). This allows a rotation of the patient's head 60 during the operation to be taken into account when determining the orientation of the astigmatism axis A of the eye in the displayed image 12 of the eye.

[0080] An operating table 40 is used to support the patient during surgery. The patient is typically secured to the operating table 40 in such a way that the patient's head 60 cannot move or is fixed to the operating table 40.

[0081] The device shown here as a preferred example further comprises a sensor 23 that measures the orientation and / or position of the operating table 40. Rotations of the table around the gravitational direction Z or around the observation direction ODh are of particular importance. The operating table 40 can be tracked with respect to its position and orientation using one or more sensors 23 if a change in orientation of the operating table 40 during the operation cannot be ruled out. This is particularly useful if a relevant rotation of the head 60 around the optical axis of the observing microscope camera is physically impossible due to the way the patient is positioned, that is, if the patient's head 60 is fixed to the operating table 40 in such a way that it cannot move relative to it.

[0082] Thus, the patient's head 60 can also be spatially tracked, analogous to the operating microscope 10 or the camera integrated into the microscope head 10a. If rotation of the patient's head relative to the table is impossible due to the positioning, then it is sufficient if either the head or the table is equipped with a sensor.

[0083] The sensors 20a, 21, 22, 23 can be arranged individually or in combination to detect the relative rotation between the surgical camera and the eye 13 around the observation direction O. Individually or in combination, they form a sensor assembly 20. This assembly is coupled to the processing unit 30 such that the signals from the sensors 20a, 21, 22, 23 are transmitted to the processing unit 30. This is done via an electrical connection, which can also be wireless.

[0084] The processing unit 30 calculates the current orientation R' of the astigmatism axis A in image 12 of eye 13 during the eye surgery. As long as there is no change in the orientation or position of the operating microscope 10 relative to the patient's eye 13, the current orientation R' of the astigmatism axis A corresponds to the actual orientation R of the astigmatism axis. However, this assumes that the actual orientation of the astigmatism axis, which was diagnostically determined before the operation, has not changed due to specific surgical steps. The calculation is described below with reference to the Figure 3A , 3B, 3C explained in more detail.

[0085] The processing unit 30 includes a memory 31 which, among other things, stores the orientation R of the astigmatism axis A of the eye as a reference value for subsequent calculations. The memory also stores the measured values ​​determined by the sensor device 20, which are used to calculate the current orientation R'.

[0086] The display unit 11 is coupled to the processing unit 30 to display the calculated orientation R' of the astigmatism axis A in the image 12 of the eye 13. The display unit 11 is, for example, a display that reproduces the image captured by the camera integrated in the microscope head 10a. In addition to the captured image, the astigmatism axis A is displayed in the current orientation R' calculated by the processing unit 30, or superimposed on the image 12 of the eye 13.

[0087] However, it is also possible that the display unit 11 can be viewed through the eyepiece of the operating microscope 10 or is integrated into the operating microscope 10.

[0088] Figure 2 shows in detail the computing unit 30, the display unit 11, as well as the sensors 20a, 22 and 23, as described above with reference to Figure 1 The sensors 20a, 22, and 23 form, or are part of, the sensor assembly 20 and are designed as rotation rate sensors, gyroscope sensors, or IMUs. At least one sensor 20a is arranged on the microscope head 10a to determine its orientation or position with the aid of the processing unit, while one or more sensors 22 and 23 are attached to the patient's head 30 and the operating table 40, respectively, to enable the determination of the orientation or position of the head 60 and the operating table 40, respectively.

[0089] The computing unit 30 continuously reads the angular velocities measured by the gyroscopes or IMUs and calculates the orientation relative to a reference orientation.

[0090] The sensors of the sensor device 20 are connected to the processing unit 30 via electrical connections 61, 62, 63. These electrical connections can also be wireless. They serve to transmit the sensor signals to the processing unit 30.

[0091] The processing unit 30 is connected to the display unit 11 via a further electrical connection 64, which is, for example, wireless. The processing unit 30 generates signals to control the display unit 11 in order to display the current orientation R' of the astigmatism axis A in the image 12 of the eye 13, which is calculated from the values ​​measured by the sensors.

[0092] Figure 3AThe field of view of the microscope camera, in which the image 12 of the patient's eye 13 is located, is shown. The field of view is displayed on the display unit 11 (see Figure 1 ). Also shown in Figure 12 is the astigmatism axis A of the eye 13, which in the example shown is approximately aligned in the Y direction.

[0093] Figure 3B The image shows the field of view of the microscope camera, but here the displayed image 12 has been rotated about the Z-direction, which is perpendicular to the image plane. This rotation of the image about the Z-direction is caused, for example, by a counterclockwise rotation of the operating microscope 10 about the observation direction O (see Fig. 1 ). Due to the rotation of image 12, the eye 13 in image 12 is shown rotated clockwise.

[0094] Without the calculation and correction of the displayed orientation of the astigmatism axis A according to the invention, it would not rotate with the image and would therefore be displayed incorrectly. This incorrectly displayed orientation is represented by the dashed line E in Figure 3D. The resulting error corresponds to the rotation angle α, i.e., the angle of rotation of the operating microscope 10 or of the image 12. α = Winkel y → , y → new bzw . α = Winkel x → , x → new

[0095] The processing unit 30 now calculates the new or corrected orientation R' or angular position of the astigmatism axis A in image 12 from the signals supplied by the sensor device 20, so that it is displayed correctly with respect to the eye 13, i.e., relative to the eye 13. The correction angle corresponds to the angle α, i.e., the angle by which image 12 has been rotated relative to its initial position.

[0096] Figure 3CFigure 1 illustrates the case where the patient's head 60 has rotated around the observation direction O. This could have been caused by the patient himself and / or by a rotation of the operating table 40 around the observation direction O. In this example, it is assumed that there has been no change in the orientation of the operating microscope 10.

[0097] As a result of the rotation of the head 60, the orientation of the eye 13 in Figure 12, or rather the astigmatism axis, no longer corresponds to the original orientation; that is, the eye 13 is shown rotated in Figure 12. Without the calculation of the orientation of the astigmatism axis A according to the invention, it would again be displayed incorrectly, as shown by the dashed line E. That is, in this example, it would still be shown running approximately parallel to the direction of the y-axis of the image, just as its position in Figure 12 was originally determined before the rotation of the head 60 (see Figure 12). Figure 3A ).

[0098] Using the sensor device 20 and the processing unit 30, this error is now corrected. The actual, current orientation of the astigmatism axis A of the eye is calculated by correcting its angular position by the angle β.

[0099] This angle β corresponds to the rotation angle of the head 60° around the observation direction O. β = Winkel Rot Kopf

[0100] If the head is positioned in such a way that rotation relative to the patient bed is prevented by fixation, a head sensor is not required. Instead, a sensor attached to the bed can be used to detect head rotation and thus eye rotation. In such a case, β corresponds to the rotation angle of the patient bed. β = Winkel Rot Liege

[0101] An additional head sensor would be redundant, as it would measure the same rotation, rotation rate, or angular velocity around the observation direction as the sensor on the couch, i.e., the same angle β would result. β = Winkel Rot Liege = Winkel Rot Kopf

[0102] As a result of this calculation, the astigmatism axis A in Figure 12 is shown in the direction R'. Due to the calculation and the actual orientation of the astigmatism axis A of the eye, which was previously diagnosed, the orientation R' corresponds to this.

[0103] The individual steps of the procedure are explained below: To display the astigmatism axis of the eye during eye surgery, an image 12 of the eye 13 is first captured with the operating microscope 10. This is done at time T1, when the operating microscope 10 has not yet been rotated relative to the patient's eye 13. In this state, an initial measurement is taken, which indicates the orientation R of the astigmatism axis A in image 12. Thus, the orientation R of the astigmatism axis A at time T1 in image 12 of the eye 13 corresponds to the actual orientation ( see Figure 3A ). In the Figure 3AIn the example shown, this is approximately 90 degrees to the x-axis of the image.

[0104] Now the angular position OP1 of the microscope head 10a is initialized around the observation direction at this first time point with, for example, 0 degrees and stored as the reference orientation, i.e. OP1 := 0 degrees.

[0105] During the operation, the angular position or rotation OP2 of the microscope head 10a, and thus of the integrated camera, around the observation direction is determined again, i.e., at a later, second time point T2. At this time point, the microscope head 10a, and thus the integrated camera, has been rotated, for example, 30 degrees counterclockwise around the z-axis. The new orientation of the camera relative to the orientation at time point T1 corresponds to the angle OP2-OP1, which in this case is plus 30 degrees. d . h . OP 2 − OP 1 = + 30 Grad .

[0106] The sign is positive because the rotation of the operating microscope 10 around the z-axis was counterclockwise. The angle of rotation of the operating microscope 10 is: α = ΔOP = OP 2 − OP 1 , In this example, that means: ΔOP = +30 degrees - 0 degrees, so α = + 30 Grad

[0107] This has caused the orientation of eye 13 in the image to rotate by 30 degrees clockwise (see Figure 3B ). This means that the rotation of the eye in image 12 at time T2 is: ΔA = − ΔOP , hier also ΔA = − 30 Grad

[0108] The corrected orientation R' of the astigmatism axis A in Figure 12 is then calculated. First, the initial measurement is used, which represents the orientation R of the astigmatism axis A in Figure 12 at the first time point T1. In this example, R = 90 degrees. The angle ΔA is then added to the angle R, which represents the original orientation R of the astigmatism axis at time T1. R ′ = R + ΔA , bzw . R ′ = R − ΔOP = R − OP 2 − OP 1 = R − α = 90 Grad − 30 Grad = 60 Grad

[0109] The orientation R' of the astigmatism axis A of eye 13 calculated in this way at time T2 is displayed by means of the display device in image 12 of the eye.

[0110] However, the angle of the relative rotation between the operating microscope 10 or the camera in 10a and the eye 13 can change, as shown above. Figure 3C depicted, not only from a rotation of the operating microscope 10 with the camera, but also from a rotation of the patient's head 60.

[0111] In this case, R' is calculated as follows: R ′ = R + β where β denotes the angle of the rotation of the head 60 about the z-direction or about the direction of the gravitational vector g.

[0112] Taking all rotations into account, the corrected angle for the representation of the astigmatism axis R' in image 12 of eye 13 is given by: R ′ = R − α + β

[0113] The angular position and calculation of R' can also be performed multiple times or continuously, meaning that the position or orientation of the operating microscope 10 is monitored or tracked during the operation. This means that the orientation or position of the operating microscope 10, the patient's head 60, and the operating table 40 are advantageously measured and tracked multiple times during the operation, so that at every point in the operation the orientation R' of the astigmatism axis A is correctly displayed in image 12 of the eye, regardless of any rotations around the observation direction O that may have occurred in the meantime.

[0114] If the position or orientation of the eye's astigmatism axis changes due to surgical procedures, as can occur, for example, with incisions at the iris margin, the previously determined, preoperative position of the astigmatism axis A is nevertheless displayed on the display unit 11, since the astigmatism axis is not remeasured on the eye during the operation. Instead, the original astigmatism axis A with its original orientation R in the displayed image is always used as the basis, along with the subsequent relative rotation between the operating microscope 10 or the camera in 10a and the eye 13 around the observation direction Z that occurs during the operation.

[0115] The device and method according to the invention offer the advantage that a diagnostic image is not required. Despite a possible change in the orientation of the astigmatism axis due to surgical steps, the orientation of the preoperative axis or the target orientation of the IOL to be implanted can be displayed at any time. Determining the orientation of the astigmatism axis A by a reference measurement and subsequent evaluation of sensor signals is far less complex and error-prone than continuous, camera-based direct measurement or the application of image processing algorithms, the accuracy of which can be negatively affected by image quality, the presence of foreign objects such as surgical instruments, occlusions, or bleeding when registering a diagnostic image with current camera images, etc.

Claims

1. Device designed to display the astigmatism axis of the eye, comprising an observation unit (10) for observing the eye (13), a display unit (11) designed to display the orientation (R) of the astigmatism axis (A) of the eye (13) in an image (12) of the eye (13), a sensor device (20) designed to generate sensor data that indicates a change in the orientation of the observation unit (10) relative to the eye (13), and a computing unit (30), characterized in that the sensor device (20) comprises at least one rotation rate sensor (20a) which is attached to the observation unit (10) and which is designed to detect an angle of rotation of the observation unit (10) about its observation direction (O), and the computing unit (30) is designed to use the sensor data of the rotation rate sensor (20a) to calculate from the orientation (R) of the astigmatism axis (A) in the image (12) of the eye (13) at a first point in time (T1) and from the rotation angle of the observation unit (10) around its observation direction (O) at the first point in time (T1) and at a current second point in time (T2), the current orientation (R') of the astigmatism axis (A) in the image (12) of the eye (13), and to provide it to the display unit (30) for display in the current image (12) of the eye (13).

2. Device according to claim 1, characterized in that the observation unit (10) comprises a surgical microscope or is configured as such.

3. Device according to claim 1 or 2, characterized in that the observation unit (10) comprises a device (10a) for capturing images of the eye (13) or is configured as such.

4. Device according to any one of the preceding claims, characterized in that the display unit (11) is configured as a display.

5. Device according to any one of the preceding claims, characterized in that the display unit (11) comprises a mirror arrangement for coupling into the optical path of the observation unit (10).

6. Device according to any one of the preceding claims, characterized by a memory (31) for storing a reference value representing the orientation (R) of the astigmatism axis (A) of the eye (13) at the first point in time (T1), and / or for storing a reference orientation of the observation unit (10).

7. Device according to any one of the preceding claims, characterized in that the sensor device (20) determines the position of the observation unit (10).

8. Device according to any one of the preceding claims, characterized in that the sensor device (20) comprises one or more inertial measurement units.

9. Device according to any one of the preceding claims, characterized in that the sensor device (20) comprises one or more sensors selected from the group consisting of acceleration sensors, direction sensors, compass sensors, and sensors (21) for measuring the angular position of the joints (10b) of the observation unit (10).

10. Device according to any one of the preceding claims, characterized in that the sensor device (20) comprises one or more sensors (22) for determining the orientation and / or position of the head (60) of the patient.

11. Device according to any one of the preceding claims, characterized in that the sensor device comprises one or more sensors (23) for determining the orientation and / or position of an operating table (40).

12. Device according to any one of the preceding claims, characterized by a device for tracking the position and / or orientation of the observation unit (10) and / or the orientation and / or position of the head (60) of the patient.

13. Method for displaying the astigmatism axis of the eye, characterized by the steps of: providing an observation unit (10) for observing the eye (13); providing the orientation (R) of the astigmatism axis of the eye (13) in an image (12) of the eye (13) for display on a display unit (11) during observation of the eye (13); acquiring and storing sensor data indicating a change in the orientation of the observation unit (10) relative to the eye (13); characterized in that the rotation angle of the observation unit (10) about its observation direction (O) is detected by a rotation rate sensor (20a), and using the sensor data of the rotation rate sensor (20a), the current orientation (R') of the astigmatism axis (A) in the image (12) of the eye (13) is calculated from the orientation (R) of the astigmatism axis (A) in the image (12) of the eye (13) at a first point in time (T1) and from the rotation angle of the observation unit (10) about its observation direction (O) at the first point in time (T1) and at a current second point in time (T2), and is provided to the display unit (30) for display in the current image (12) of the eye (13).

14. Method according to claim 13, characterized in that the orientation of the observation unit (10) is tracked.

15. Method according to claim 13 or 14, characterized in that the orientation and / or position of the head (60) of a patient and / or of a patient table (40) is measured in order to detect a rotation of the head (60) about the observation direction (O) or the optical axis of the observation unit (10) and to use it in calculating the current orientation (R') of the astigmatism axis.

16. Method according to any one of claims 13 to 15, characterized in that the current orientation (R') of the astigmatism axis is displayed on a display and / or is coupled into the optical path of a surgical microscope.