METHOD AND DEVICE FOR DETERMING THE ORIENTATION OF THE EYE DURING EYE SURGERIES

Abstract

Disclosed are a method and a device for controlling an eye surgery system, wherein a light pattern is generated on an eye by an illumination device and is captured by a camera unit while the patient is in the position in which he or she will undergo the surgery. At least one property of the eye characterizing the current orientation of the eye during the surgery is determined from the light pattern by a computing unit.

Claims

1. A method for determining the orientation of the eye during eye operations, characterized by the following steps: generating a light pattern on the eye and capturing the light pattern while the patient is in the operation position; and determining at least one property of the eye from the light pattern captured when the patient is in the operation position, said property characterizing the current orientation of the eye.

2. The method as claimed in claim 1, characterized in that the property determined from the light pattern is used to control a light marking generated on the eye and/or to correct the position of the ablation locations during a laser treatment of the eye, depending on the current orientation of the eye, and/or to determine the viewing direction.

3. The method as claimed in claim 1, characterized in that the property ascertained from the light pattern is a specific topographic property of the eye.

4. The method as claimed in claim 1, characterized in that the property ascertained from the light pattern characterizes the position of the astigmatism axis of the eye and/or a direction with a defined relationship thereto.

5. The method as claimed in claim 1, characterized in that the property ascertained by the light pattern is determined by collecting data of the eye during the operation, the data, in particular, being obtained from topometric, topographic, keratometric, keratographic or ophthalmometric measurements.

6. The method as claimed in claim 5, characterized in that the current data, or variables derivable therefrom, are compared to corresponding data ascertained during the diagnosis, or variables derivable therefrom, in order to determine therefrom a change in position during the operation in relation to the time of diagnosis.

7. The method as claimed in claim 5, characterized in that the data collected during the operation and the associated images are stored and used as reference data or reference images for the subsequent image-processing-based steps.

8. The method as claimed in claim 1, characterized in that the light pattern on the eye is generated by a diffuse or afocal illumination source.

9. The method as claimed in claim 2, characterized in that the light marking indicates one or more of the following information items on the eye during the eye operation: a) a spatial marking which is required or helpful for the operation; b) the intended orientation of an intraocular lens to be inserted into the eye; c) the intended position of an incision to be carried out; d) the position of limbus and/or pupil; e) the direction of the astigmatism axis or a direction with a defined relationship thereto.

10. The method as claimed in claim 1, characterized in that light for generating the light marking on the eye is incident at an angle α to the axis along which the light pattern on the eye is captured.

11. The method as claimed in claim 1, characterized in that the light pattern generated on the eye comprises specific reflection forms.

12. An apparatus for determining the orientation of the eye during eye operations, comprising: an illumination device for generating a light pattern on the eye of a patient in the operation position; and a camera device to capture the light pattern generated on the eye during the eye operation; characterized by a computer unit configured to ascertain at least one property of the eye, which is dependent on the current orientation of the eye, from the captured light pattern during the eye operation.

13. The apparatus as claimed in claim 12, characterized by a fastening device for fastening the illumination device and/or the camera device to an operation microscope.

14. The apparatus as claimed in claim 12, characterized by a control unit configured to control a second illumination device for generating a light marking on the eye on the basis of the currently ascertained property of the eye during the eye operation and/or to control an ablation laser on the basis of the currently ascertained property of the eye during the eye operation.

15. The apparatus as claimed in claim 12, characterized in that the property ascertained from the light pattern characterizes a specific position-dependent characteristic of the eye and/or a specific topographic property of the eye and/or the position of the astigmatism axis or a direction with a defined relationship thereto.

16. The apparatus as claimed in claim 12, characterized by a second illumination device for generating a light marking on the eye, which displays one or more of the following information items on the eye during the eye operation: a) a spatial marking which is required or helpful for the operation; b) the intended orientation of an intraocular lens to be inserted into the eye; c) the intended position of an incision to be carried out; d) the position of limbus and/or pupil; e) the direction of the astigmatism axis or a direction with a defined relationship thereto.

17. The apparatus as claimed in claim 12, characterized in that the illumination device generates diffuse or afocal light for generating the light pattern.

18. The apparatus as claimed in claim 12, characterized in that the second illumination device is arranged in such a way that the light for generating the light marking is incident at an angle α to the axis along which the light pattern on the eye is captured.

19. The apparatus as claimed in claim 12, characterized in that the illumination device is configured in such a way that specific reflection forms are generated on the eye.

20. An operating microscope for eye operations, characterized by an apparatus as claimed in claim 12.

21. A control unit for eye surgery systems, characterized in that it is configured to carry out the method as claimed in claim 1.

22. A computer program for controlling an eye surgery system, comprising program steps for carrying out the method as claimed in claim 1.

Description

[0079] Below, the invention is described in an exemplary manner on the basis of the figures. In detail:

[0080] FIG. 1 shows an apparatus in accordance with a preferred embodiment of the invention, which is fastened to an operating microscope;

[0081] FIGS. 2a-2c show preferred examples of light patterns generated on the eye;

[0082] FIGS. 3a and 3b show different light-source arrangements as an illumination device for generating light patterns on the eye;

[0083] FIG. 3c shows a diffuse light source of the illumination device comprising a diffusor element;

[0084] FIGS. 3d and 3e show illumination devices for generating specific reflection shapes on the eye;

[0085] FIG. 4a shows images of the eye at the diagnosis and during the operation, wherein a twist or torsion of the eye about the viewing axis has taken place between the two recordings;

[0086] FIGS. 4b and 4c show images of the eye with light reflections having specific reflection shapes;

[0087] FIG. 5 shows an operating microscope comprising the apparatus according to the invention;

[0088] FIG. 6 shows an operating microscope according to the invention, in which the internal camera of the operating microscope is used as a camera for capturing the light pattern generated on the eye;

[0089] FIG. 7 shows an operating microscope which comprises the apparatus 10 according to the invention, with an illustration of the angles α1 and α2 with the optical axis of the internal camera for capturing the image of the eye;

[0090] FIG. 8 shows an image of an eye which is tilted or rotated to the right in the illustration; and

[0091] FIG. 9 shows an image of an eye with a light pattern projected thereon for detecting a tilt of the eye.

[0092] FIG. 1 shows an apparatus 10 in accordance with a preferred embodiment of the invention, which is fastened to an operating microscope 20. The operating microscope 20 comprises eyepieces 21, 22, through which the medical practitioner peers onto the eye 30 of the patient during the operation. The apparatus 10 for determining the orientation of the eye 30 is arranged on the side of the operating microscope 20 facing the eye 30. The apparatus 10 comprises a camera 11 and an illumination device 12 which serves to generate a light pattern on the eye 30. The camera 11 serves to capture the light pattern generated on the eye and is connected to a computer unit 13. From the captured light pattern, the computer unit 13 ascertains a parameter which is characteristic for the current orientation of the eye 30.

[0093] Appropriately designed light sources are used in order to generate diffuse light or afocal illumination by way of the illumination device 12. However, for example, diffusor elements may also be arranged in the beam path downstream of the light source as an attachment, for example if LEDs or optical waveguides serve as light sources of the illumination device.

[0094] A holder 14 which holds the camera 11 and the illumination device 12 and connects these to the operating microscope 20 serves as a fastening device. However, a camera integrated into the operating microscope may also serve to capture the light pattern generated on the eye.

[0095] The current orientation of the eye is understood to mean, in particular, the torsional position, i.e. the angle of rotation of the eye about the axis of the viewing direction.

[0096] Optionally, provision is additionally made of a second illumination device 15 or a light-pattern generator.

[0097] The second illumination device 15 serves to generate a light marking on the eye 30, the location or position of which light marking is controlled on the eye 30 on the basis of the parameter ascertained by the computer unit 13 from the image data of the camera 11. Advantageously, the second illumination device 15 is likewise fastened to the holder 14. It is also possible to determine the viewing direction with appropriate moving or static patterns.

[0098] The eye 30 comprises the sclera 31, the iris 32, the pupil 33 and the cornea 36.

[0099] FIGS. 2a-2c show preferred examples of the light pattern 40 generated on the eye 30. Once again, the sclera 31, the iris 32 and the pupil 33 are shown as parts of the eye 30. The light patterns 40 arise as a result of the light reflections on the cornea of the eye 30.

[0100] The light pattern 40 shown in FIG. 2a consists of an ellipse-like arrangement of light points. In this example, the light points or the corneal light reflections are generated by a circular arrangement of LEDs with diffusor elements disposed upstream thereof as an illumination device 12 of the apparatus 10 (see FIG. 1). The deformation to an ellipse-like arrangement emerges from the astigmatism of the eye 30. The longitudinal axis of the ellipse approximately corresponds to the astigmatism axis 34 of the eye 30.

[0101] In FIG. 2b, a ring-shaped or circular diffuse light source is used as illumination device 12 (see FIG. 1) for illuminating the eye 30. An ellipse-like light reflection on the cornea of the eye 30 emerges as light pattern 40. In this example too, the ellipse-like form of the light pattern 40 arises from the astigmatism of the eye 30, with the semi-major axis of the ellipse approximately corresponding to the astigmatism axis 34 of the eye 30 and specifying the direction thereof.

[0102] An arrangement of a plurality of ring-shaped, diffuse light sources, which are arranged as concentric circles, is used in FIG. 2c as an illumination device for illuminating the eye 30. Ellipse-like light reflections on the cornea of the eye 30 emerge as light pattern 40. In this example too, the ellipse-like shape of the light pattern 40 arises from the astigmatism of the eye 30, the semi-major axes of the ellipses approximately corresponding to the astigmatism axis 34 of the eye 30 and specifying the direction thereof.

[0103] In accordance with the invention, it is not necessary for the torsion, i.e. the relative twist of the eye between diagnosis and operation, to be determined indirectly by means of image processing by an image-feature-based comparison between a diagnostic image and an operation image. Instead, relevant parameters of the eye, such as e.g. the astigmatism axis, are determined directly during the operation by e.g. topometric, topographic, keratometric, keratographic or ophthalmometric measurements. Hence, there is independence from the image material of the diagnosis.

[0104] FIGS. 3a and 3b show, in a plan view from below, i.e. as seen from the operation object or the patient eye, a fastening device 14 with the camera 11, the illumination device 12 for generating the light pattern and the second illumination device 15. The illumination device 12 comprises a ring-shaped arrangement of diffuse or afocal light sources. The camera 11 is optional for the case where the integrated camera of the operating microscope is not used. Various light-source arrangements for generating the light pattern on the eye 30 are shown as illumination device 12.

[0105] The light sources of the illumination device 12 generate diffuse or afocal light. To this end, the holder 14 (see FIG. 1) may be equipped with a number of LEDs with diffusor elements placed in front thereof (FIG. 3b) or e.g. with diffusely luminous rings which are embodied as concentric circles (FIG. 3a). However, instead of the luminous LEDs or rings, the use of bright, non-luminous points or circles which are illuminated by a secondary light source is also possible.

[0106] FIG. 3c shows, as an example, a diffuse light source 12a of the illumination device 12 comprising an LED 121 and a diffusor element 122 arranged in front of the LED 121 as an attachment, said diffusor element being configured as a light-scattering film or glass pane.

[0107] FIGS. 3d and 3e show, as further examples, the fastening device 14 as already described in FIGS. 3a and 3b, wherein the illumination device 12 is designed to generate specific reflection shapes on the eye. For this purpose, individual light elements or light sources 12a of the illumination device 12 have a specific geometric shape, which is designed in such a way that the light reflection generated through it on the eye differs from other light reflections or foreign reflections.

[0108] In the shown examples, the individual light sources of the illumination device 12 have a rectangular, square, rhomboid or else ring-shaped design, with the light sources being provided in a defined arrangement with their different geometric shapes. The light reflections generated thereby on the eye are very clearly visible and may be distinguished very easily from the light reflections on the eye originating from other light sources.

[0109] Optionally, or additionally, the individual light sources of the illumination device 12 may also be operated in a pulsed manner or may emit light with specific or different wavelengths in order to generate a specific reflection shape or a specific light reflection on the eye, which may be distinguished from other light reflections on the eye.

[0110] FIG. 4a shows, as an example, images of the eye 30 at the diagnosis (left image) and during the operation (right image), with a ring, as shown in FIG. 3b and described further above, equipped with LEDs and diffusor elements placed in front thereof being used as illumination device 12 (see FIG. 1). The reference signs in each case denote the same elements of the eye 30 as in the preceding figures. In this example, the position of the measured astigmatism axis 34 has changed at the time of the operation in relation to the position thereof at the time of the diagnosis. This change is referred to as static torsion. Errors due to this torsion are avoided by the invention.

[0111] FIGS. 4b and 4c show, as further examples, images of the eye 30 with light reflections which have specific reflection shapes on the eye. The same reference signs as in the preceding figures denote the same elements and were already described above. The reflection shape depicted in FIG. 4b is generated by the illumination device 12 shown in FIG. 3d, while the reflection shape depicted in FIG. 4c is generated by the illumination device shown in FIG. 3e. For elucidation purposes, foreign reflections 77 are additionally shown in FIG. 4c; these are very easily identifiable as such on account of the specific reflection shape of the illumination device.

[0112] However, the ascertained position of the astigmatism axis 34 during the operation may, optionally, also be compared to the axis position during the diagnosis, said axis position preferably having been ascertained according to the same principle or else by means of a different method.

[0113] The measurement principle during the diagnosis and during the operation need not necessarily be identical. However, parameters which may be compared in terms of the spatial position thereof need to be derivable in each case. By way of example, a topographic measurement using so-called Placido rings may be carried out during the diagnosis, from which, initially, the spatially resolved surface curvature and, subsequently, both the eye surface itself and the astigmatism axis may be calculated. On the other hand, the eye surface may be measured as a point cloud during the operation, for example by way of strip-projection techniques. The astigmatism axis 34 may also be derived therefrom. As already mentioned above, it is now possible, either, to compare the 3D surface point clouds to one another by means of registration or else only the orientation of the astigmatism axis derivable therefrom in each case, in order to ascertain the torsion between diagnosis and operation.

[0114] However, it is also possible to directly measure the eye surface during the diagnosis and the operation. Here, in particular, it is also possible to apply triangulation methods, strip-projection techniques, stereo vision or similar methods. As a result, a 3D point cloud, which represents the eye surface, is generated. The point clouds arising during diagnosis and operation may be compared to one another. From this registration process, it is likewise possible, inter alia, to calculate the torsion.

[0115] However, from a technical point of view, it is easiest if the same measurement method is used during the operation as at the diagnosis. By way of example, if a ring-like arrangement of LEDs with diffusor elements placed in front thereof is used during the diagnosis for an astigmatism measurement, then such an arrangement may likewise be used during the operation. The astigmatism axes ascertained in each case may subsequently be compared. The torsion emerges from the angle included between these axes.

[0116] FIG. 5 shows an operating microscope 20 which comprises the apparatus 10 according to the invention. The elements of the operating microscope 20, including the apparatus 10 which is integrated therein or fastened thereto in a removable manner, are provided with the same reference signs as in FIG. 1. A light marking 50 is generated on the eye 30 by the second illumination device 15. The position and orientation of the light marking 50 on the eye 30 is controlled on the basis of the parameter ascertained by the computer unit 13 from image data of the camera 11 or an integrated microscope camera.

[0117] To this end, the computer unit serves as a control unit 13a or has the latter integrated therein. In this example, the astigmatism axis 34 of the eye 30 ascertained from the light pattern 40 during the operation (see FIGS. 2a to 2c) is indicated on the eye 30 by the light marking 50 and is therefore visible to the medical practitioner on the eye 30.

[0118] The elements of the eye 30 are as described above and provided with the same reference signs. The data connection between the camera 11 and the computer or control unit 13 or 13a is not depicted in FIG. 5 for reasons of clarity.

[0119] The position of the astigmatism axis 34 or the intended orientation of an intraocular lens to be inserted is projected directly onto the eye and therefore indicated to the medical practitioner directly on the eye by way of the second illumination device 15 in the form of a projector or a laser, such as e.g. a line or point laser.

[0120] To this end, the computer unit 13 evaluates the camera images of the microscope and instructs the projector or a pattern generator to generate e.g. a line as light marking 50 which, for example, indicates the astigmatism axis 34 of the eye 30 or an axis with a defined relationship thereto. Other information is also expedient, such as e.g. the locations at which incisions should be performed. The position thereof is also determined by evaluating the reflections of the light sources or the illumination device 12 generated on the cornea.

[0121] The computer unit 13 may additionally track the eye 30 so that the projector or laser is always able to generate the line at the same position, e.g. always at the center of the limbus. That is to say, the computer unit 13 is able to simultaneously track the eye, e.g. the pupil or the limbus, and instruct the projector or the second illumination device 15 to project the intended axis, which is visible to the medical practitioner, in the center of the pupil or the center of the limbus.

[0122] Tracking algorithms may ascertain the current eye position, including the torsion, and thus facilitate the projection of e.g. a co-migrating intended axis of the intraocular lens onto the eye. The display of further information is also possible, such as the locations at which the incisions should be made, the edge of the limbus, the optical and visual axes of the patient, the position of the capsulorhexis, etc.

[0123] If use is made of a projector or, in general, a pattern generator as an illumination device 15 which is provided for visualizing e.g. the astigmatism axis, it is also possible to generate 3D data with the aid of the camera 11 or the internal microscope camera, which includes an angle with the projection or illumination device 15, where necessary. A point cloud representing the eye surface or parts thereof is generated in the computer unit 13 with the aid of specific static or moving patterns. As a result thereof, it is possible, for example, to determine the viewing direction of the eye 30. If there is a certain amount of asphericity of the eye surface or of parts thereof, this also allows the dynamic or intraoperative torsion to be determined. It is likewise possible to ascertain the orientation of operating instruments situated in the field of view of the pattern and the camera 11.

[0124] When collecting the intraoperative eye data, for example with the aid of the reflections or with the aid of the aforementioned pattern generator, reflections also arise on the intraocular lens in the case of an appropriate angle of incidence, which reflections may be used for determining a position. Using this, it is possible, for example, to compare the axis of a toric lens with the astigmatism axis of the cornea and thus ascertain a possible incorrect orientation of the intraocular lens. It is likewise possible to detect an oblique position of the lens.

[0125] FIG. 6 shows an operating microscope 20 according to the invention, in which the internal camera of the operating microscope 20 is used as camera 11 for capturing the light pattern generated on the eye. The elements denoted by the further reference signs were already described above.

[0126] FIG. 7 shows an operating microscope 20 which comprises the apparatus 10 according to the invention, as already described in relation to FIGS. 1 and 5. For reasons of clarity, the computer unit 13 (see FIG. 5) has not been depicted in this figure. The depicted elements are provided with the same reference signs as in FIGS. 1 and 5. Additionally, diffusor elements 122, which are placed in front of the LEDs of the first illumination device 12, are explicitly depicted. The camera 11 is optional for the case where the integrated camera of the operating microscope is not used for capturing the light patterns on the eye 30. However, it may also be used in addition to an integrated camera of the operating microscope.

[0127] In the example shown here, the second illumination device 15 in the form of a pattern generator generates a line pair 151, 152, which is projected onto the eye 30. The individual lines 151, 152 include the angles α1 and α2 with the optical axis AI of the internal camera of the operating microscope 20. These angles are advantageously of the order of approximately 5 to 45 degrees. The angles which the lines 151, 152 include with the optical axis of the optional camera 11 are not depicted for reasons of clarity.

[0128] The fact that the angles α1 and α2 are greater than zero facilitates the determination of alignment or tilt of the eye 30. The greater the tilt or rotation of the eye about the horizontal and vertical axes thereof, the less the center of the reflections coincides with the apex of the cornea 36. As a result, the statements from the calculations based on the reflection patterns no longer relate to the corneal apex. Depending on the tilt, the calculated astigmatism axis may deviate from the central astigmatism axis and it is therefore only still comparable with the astigmatism axis during the diagnosis to restricted extent.

[0129] By way of example, an eye tilt of 5° already results in a decentration of 1 mm of the light reflection center from the apex. This value rises to approximately 2 mm at 10°. For elucidation purposes, the decentration is depicted in FIG. 8, wherein the eye 30 is rotated to the right in the shown example. The employed reference signs denote the elements of the eye 30 as already described above.

[0130] The fact that the center of the reflections and the center of the pupil or the limbus do not correspond in the camera image may only be used to restricted extent for determining a tilt since there need not necessarily be a coincidence between reflection center and center of pupil or limbus in the case of an asymmetrically shaped limbus or pupil, even in the case of a vanishing tilt. It is also possible that the limbus, in part, is so out of focus that the limbus center may no longer be reliably identified or determined.

[0131] By way of example, the tilt may be detected by virtue of generating a light pattern on the eye at arbitrary times with the aid of a pattern generator. This is shown as an example in FIG. 9. The employed reference signs denote the elements of the eye 30 as were already described above.

[0132] In order to determine the tilt of the eye 30, the points of intersection P1, P2, P3, P4 of the light pattern, which is a line pair in the depicted example and which is projected onto the eye 30 as shown in FIG. 7, with the limbus are ascertained. Subsequently, the 3D-coordinates of these points of intersection P1, P2, P3, P4 are calculated after a preceding, patient-independent calibration process, with the aid of which 3D-coordinates an equalization plane is approximated. Finally, the normal of the plane specifies the eye orientation. The shown line pair is only one example of many possible patterns. However, there must be at least three points not lying on one line.

[0133] It is also possible to combine displaying the astigmatism axis 34 and calculating the tilt, for example by virtue of generating a relatively tight line pair on the eye 30, which, on the one hand, ascertains a tilt and, on the other hand, displays the ascertained astigmatism axis. In particular, a specific color or blinking of the lines generated on the eye supplies the medical practitioner with indications for the current tilt.

[0134] Alternatively, the eye orientation may also be ascertained without a pattern generator but with the aid of an additional camera by means of stereo vision. To this end, the edge of the limbus, for example, is detected in both camera images in order subsequently to use the respective image coordinates for calculating the spatial position thereof.

[0135] A substantial advantage of the system and method according to the invention lies in the fact that the re-measurement of eye parameters, such as e.g. the astigmatism axis, means that there is no dependence on image material from the diagnosis.

[0136] In particular, it is possible to introduce intraocular lenses with a high accuracy at the envisaged position, for example in relation to the axis position of the eye, into the eye without a torsion of the eye during the operation, or between the time of diagnosis and the time of operation, impairing the accuracy. In the process, the lens axis may be oriented along the axis position of the eye, which is visible to the medical practitioner during the operation.

[0137] The static torsion, in particular, may be measured very well during laser treatments. It is also possible, for example, to rotate shot patterns during laser treatments in accordance with the measured intraoperative axis position prior to the start of the treatment such that the treatment errors as a result of the static torsion are avoided.