Device for examining or treating a human eye

[0001] The invention relates to a device for examination or treatment on the human eye.

[0002] Laser irradiation is used in numerous techniques of treatments on the human eye. In some of these techniques, focused laser radiation is used to remove the eye tissue. In this case, it is necessary to control the focus of the radius on the eye so that the removal of the tissue takes place at the defined position of the eye. Due to eye movements during the procedure, however, it is possible to move the eye in relation to the laser beam radius. This may lead to a deviation between the set position and the actual position of the removal.

[0003] For this reason, it is desirable to follow the eye movements and take them into account when controlling the radius. Eye trackers are used to record eye movements. Currently, two-dimensional eye tracking is particularly typical, which is based on registering the pupil's eye edge by only one camera. From the contrast jump jasnociemne on the edge of the pupil (iris) calculates the center of the pupil, which then serves as the coordinate for laser removal. Control of the laser beam is then taking into account the eye pupil's eye position determined by the device. However, the position of the pupil center is not always on the symmetry axis of the eye or the visual axis of the patient's vision (for example, by asymmetric shifting of the pupil center with different pupil size or deviation from round symmetry in some patients). Such a deviation may lead to suboptimal results of the procedure.

[0004] In order to avoid such misplacements in the pupil's center of the pupil's inaccuracy in the laser procedure, pupil tracking can be complemented by tracking a limbus which is oriented on the unchanged clear-dark transition of the white sclera (eye skin) to the iris. Significant pupil center shifts can be detected in this way and included in the removal program as so-called Pupil Center Shift Correction (PCSC).

[0005] Overall, the state of the art currently uses two-dimensional camera image recording to track eye movements. The position data derived from this, however, may be erroneous because proper eye movements occur in three-dimensional space, and thus must be described by three translational movements and three rotational movements. In addition, eye trackers, which are based on two-dimensional camera images, allow only intermediate recording of 3D data by a computationally intensive reconstruction. Currently available are image-based eye trackers that allow five- or six-dimensional eye tracking. By additional projection of the light pattern from the eye strips and by recording these strips (registration of curvature, position and deformation of the strips), the location and orientation of the eye is deduced. However, the registration procedure is also intense in terms of calculation and time-consuming. Therefore, the image transmission speed used

There are now limited eye tracker devices, and often too slow to correct the position of the eye with the use of laser light. In addition, camera systems used for this purpose only detect light scattered or reflected by the eye of the patient, therefore it is necessary to ensure adequate eye lighting (which, however, may have a negative effect on the treatment), and at the same time it is possible to avoid lighting other side lighting from the room to the eye .

[0006] WO 99/65431 relates to a method and apparatus for tracking (tracking) a surface position of an object. The device is created as an OCT tracking device, the controller processes the recorded output signal and detects the peak interference signal on its basis.

[0007] US 5,644,642 relates to an eye tracking method and apparatus using OCT coherence tomography. The OCT device scans the OCT radius accordingly to any two-dimensional scanning path. The output data of the OCT device is provided as input data on the analysis computer to determine the center of the pupil of the eye or the initial border of the pupil iris.

[0008] US 2006/0187462 relates to a method and apparatus for improving the power and optical accuracy of OCT coherence tomography and describes a scan with reference to specific sample markers. In this case, OCT data is recorded in the first scan and the second scan, the object markers are identified based on them and the location changes are determined. The scans are carried out in such a way that different cross-sections in the sample are measured while the scan patterns are used, in particular, unidirectional raster scanning, bidirectional scanning or axial scanning, measured at various lateral positions on the sample.

[0009] WO 03/070090 relates to a method and apparatus for performing eye OCT testing using a tracking system to focus the OCT scanning radius on a desired property in retinal tissue.

[0010] WO 03/105678 relates to a method and apparatus for optical imaging. Optical imaging is based on OCT optical coherence tomography, with two-dimensional images being generated and based on them a three-dimensional image of the sample is constructed. The single-scan OCT scanning technique can be used to track accidental changes in the gap between the sample and the imaging device, i.e. the axial movements of the sample.

[0011] An object of the invention is to provide a device for examination or treatment on a human eye that includes an eye tracker device that can provide results regarding eye movements at high speed and precision.

[0012] This object is achieved by a device according to claim 1 and a method according to claim 4.

[0013] In order to achieve this object of the invention, a device for examination or treatment on the human eye is provided, with an eye tracker device for recording eye movements and for eye movements.

- providing a signal representative of the recorded eye movements, the eye tracker having interferometric image recording apparatus adapted for temporary recording, which operates on the basis of a three-dimensional optical coherence tomography, and an analysis module determining the eye motions from cross-sectional images .

[0014] The image recording interferometer may have, for example, a scanning speed of> 200,000 linear scans per second, wide lateral scanning ranges> = 15 mm, depth ranges> 8 to 12 mm, high speed digital (CCD, CMOS) digital cameras max. 12,000 pixels per line or more, high reading speed of around 140 kHz, high documenting sensitivity> -90 dB and high resolution in the range from <1 to 10 μm. A three-dimensional image transfer rate of 500 frames per second or more is possible.

[0015] The invention is advantageous in that due to the use of the interferometric measuring method, light falling from another side lighting from the room to the eye does not interfere with eye tracking because only the coherent and not incoherent light is captured in the measurement process.

[0016] The invention also enables the use of high resolution, high measuring speed and high sensitivity of interferometric image recording devices that work on the basis of three-dimensional optical coherence tomography, not only so far for tomography, i.e. for structural measurement of a specific segment of the eye, but also to measure the position and orientation of the eye in space. The decisive factor here is that only data (one or more) of interferometric image recording devices are used to determine position, orientation and motion signals, which enable image recording with X, Y and Z coordinate coordinates to each image point.

[0017] By means of temporarily recording the cross-sectional images of the eye, it is thus possible to determine the respective eye movements. Such eye movements include cyclotors movements (flat revolutions around the optical axis of the eye), rolling movements (eye rotation around the axis, perpendicular to the optical axis of the eye) and translational movements in all three spatial directions. The accuracy of the measurement of the six-dimensional eye movements due to the use of interferometric image recording devices can be much higher than in the case of cameras based on the eye tracker type. The device according to the invention also offers a much higher speed when recording eye movements.

[0018] According to a further embodiment of the invention the interferometric image recording device may be designed to register at least two rectangular cross-sectional images of the eye, which each represent a cross section substantially along the visual axis of the eye. However, cross-sectional images can also follow the visual axis of the eye, parallel to the visual axis of the eye or substantially along the central (optical) axis of the eye, along the central axis of the eye, parallel to the central axis of the eye or on the apex of the eye. Two cross-sectional images arranged rectangular to each other enable registration of the orientation and position of rolling movements and translational movements in

- direction X and Y (a simple notation is used here, in which the direction of the radius of measurement of the interferometric image recording device runs along Z, and X and Y together with Z complete the three-dimensional Cartesian coordinate system). Also, the translational shift and / or translational movement in the Z direction can be determined based on such cross-sectional images. The recording may take place, for example, by comparing with one or more of the earlier ones (e.g., before the beginning of the treatment) cross-sectional images. In particular, high-resolution three-dimensional complete cross-section images can be used for comparison purposes.

[0019] In addition, the interferometric image recording device is intended to record at least one cross-sectional image of the eye that represents a section along the edge of the iris of the eye. On the basis of such a cross-sectional image, significant structures (e.g. in the iris) can be identified and used to determine the cyclotourism of the eye. This type of cross-section should be understood as an eye shot from the front.

[0020] The image recording device and the analysis module are preferably designed to time-record multiple cross-sectional images of the eye and to determine from the cross-sectional images the temporal topography of the partial region of the eye as a signal representative of eye movement. Many cross-sectional images of the eye may correspond, for example, to sections of the eye that are moved parallel to one another. The partial region of the eye may include, e.g., the cornea, the lens of the eye, the front chamber range, the sclera, the iris, the cornea apex, the center of the eye lens and / or the hole, completely or partially.

[0021] The invention thus enables the recording of the partial eye range (eg on the basis of temporal corneal tomography) of the translational and revolving movements of the eye based on time-based tomography and at the same time the orientation of the eye surgery at any point in the partial range (eg on the corneal apex). Any point can be any marked feature of the partial eye range. This allows selection of the marked feature of the partial eye range, on the basis of which it is possible to orientate and precisely perform a specific eye surgery. For example, when corneal laser treatment is inadequate, it is advisable to choose a corneal apex as a marked feature and to orientate on it. Orientation on the pupil / iris, as in the prior art, is also possible with the invention, but it is not necessary. preferably,

[0022] The invention thus makes it possible to take into account cross-sectional data of specific features of the eye and defined from cross-sectional images of eye movements during eye surgery.

[0023] The features of the eye may, for example, be exemplified by the corneal apex, the point on the inner side of the cornea, the midpoint of the pupil, the midpoint of the eye lens or well (the spot of the most intense vision).

The interferometric image recording device and the control device may also be intended to identify a deviation of the actual focusing point of the treatment laser beam from the predetermined focusing point of the treatment laser beam on or in the eye and output of the information signal, the control device being able to output e.g. to interrupt or stop the emission of the laser beam to the eye.

[0025] According to another aspect of the invention, there is a method of examining a human eye, comprising the steps of:

- temporary recording of cross-sectional images of the eye based on three-dimensional optical coherence tomography,

- determination of eye movements from cross-sectional images, and

- outputting a signal representative of registered eye movements.

Also in the aspect of the method, when recording cross-sectional images, at least two perpendicular cross-sectional images of the eye can be recorded, which each represent a cross section substantially along the visual axis of the eye. In addition, also in the method, it is possible that at least one cross-sectional image of the eye, which represents the cross section substantially along the edge of the iris, is recorded when recording cross-sectional images.

[0027] It is also possible that a plurality of cross-sectional images of the eye are temporally recorded and from the cross-sectional images the temporal topography of the partial eye range is determined as a signal representative of eye movement.

[0028] The invention is defined by the claims and below is explained in more detail on the basis of the attached drawings, showing:

Fig. 1 embodiment of a device for examination or treatment on the human eye,

Fig. 2 a schematic view of the human eye in cross-section,

Fig. 3 a schematic view of the centering error as a consequence of the movement of the rolling eye, and Fig. 4a and 4b are schematic views of the course of cross-sectional images in the eye.

[0029] Fig. 1 schematically illustrates an embodiment of a human eye examination or treatment device. The device is generally designated as 10. The device includes an eye tracker 12. The eye tracker device 12 includes an image recording apparatus 14 interferometrically connected to an image recording apparatus 14, an analysis module 16. An image recording apparatus 14 is made, for example, as a device. OLCR (OLCR: Optical Low Coherence Reflectometry) and sends a measuring radius that using (semi-permeable or

-6dwubarwnego)the reflecting mirror 18 or other suitable radius-reflecting components are provided along the optical path of the ray 20 to the subject eye 22. The image measuring beam sent by the image-measuring device 14 passes through a measuring scanner 38 that allows the measuring beam to be deflected. Thus, it is possible to external and internal examination of the eye 22 by a measuring radius at various sites of the eye tissue. The image-recording device 14 inserts the measured radius into interference with the rebounding beam returning from the eye. The cross-sectional images of the eye can be temporally recorded from such acquired interference measurement data. The image recording device 14 operates on the basis of two- or three-dimensional optical coherence tomography.

The analysis module 16 receives from the interferometric image-recording device 14 data that includes recorded cross-sectional images and calculates from these cross-sectional images in addition to the position and orientation of the eye in the three-dimensional space also eye movements 22. The eye movements present translational motions along three spatial X directions, Y, Z and rotational movements around three spatial axes X, Y, Z. The drawn coordinate system presents three spatial directions X, Y, Z, with the Z axis defining the direction of the rays 20. The eye tracker 12 determines the signals for registered eye movements representative through connection 24.

[0030] The device 10 further comprises a device 26 for laser surgery. It contains a laser 28 that sends a correspondingly intense (with high repeatability or continuous) laser beam. The laser beam expands along the optical path of the rays 30 and reaches the subject eye 22. In the course of the rays 30 are placed various components for guiding and forming the laser beam. In particular, these components include a focusing lens 32 and a scanner 34 in front of the lens 32, by means of which it is possible to deflect the laser beam 28 formed by the objective lens 32 along the direction of X, Y and Z. The control system 36 controls the scanner 34 on the basis of a specific control program that implements the delete profile created in eye 22. In the range between the mirror 18 and the eye 22, the measurement radius of the image recording device 14 and the treatment laser beam extend in a collinear or at least essentially collinear manner. Alternatively or additionally, the laser treatment device 26 may be constructed in such a way that the laser 28 is formed as an ultra-short pulse laser that reproduces a pulsed laser beam with a pulse duration in the pico-, femto or attosecond range and is suitable for cutting in eye tissue, which is necessary for example for LASIK or cataract surgery. The laser surgery device allows, for example, cutting accuracy ± 10 μm or even ± 1 μm. the laser treatment device 26 can be made in such a way that the laser 28 is formed as an ultra-short pulse laser that reproduces a pulsed laser beam with a pulse duration in the pico-, femto or attosecond range and is suitable for cutting in the tissue of the eye, it is necessary for example for LASIK or for cataract surgery. The laser surgery device allows, for example, cutting accuracy ± 10 μm or even ± 1 μm. the laser treatment device 26 can be made in such a way that the laser 28 is formed as an ultra-short pulse laser that reproduces a pulsed laser beam with a pulse duration in the pico-, femto or attosecond range and is suitable for cutting in the tissue of the eye, it is necessary for example for LASIK or for cataract surgery. The laser surgery device allows, for example, cutting accuracy ± 10 μm or even ± 1 μm.

The image of the cross-section of the eye recorded by the image-recording device 14 is schematically represented, for example, in Figure 2. In this figure, the apex (i.e., the furthest away from the center of the eye) is visible, the iris 42, the iris 44, the pupil 46 and the lens 48 In addition, an axis 50 is drawn in figure 2, which shows, for example, the central (optical) axis of the eye 22 or the axis of the eye's view. In this case, axis 50 is represented by the position of apex 40 and the position of the pupil center 52.

[0032] For the removal of the eye tissue, it is necessary to precisely position the appropriate part of the tissue in position and orientation relative to the device 10. However, it can not be ruled out that the eye will move or distort relative to the X, Y, Z coordinate system during the procedure (and thus in relation to device 10).

[0033] Eye trackers are known in the prior art, based on recording the position of the pupil center 52 in eye 22 by means of cameras for two-dimensional registration of the pupil center 52 in the XY plane. If it is intended to remove the eye tissue in a given position that is different from the position of the eye center 52, suboptimal results of the treatment are possible based on the eye's rotation, as more fully explained in Fig. 3.

[0034] Fig. 3 shows a schematic view of the pupil 46 and the eye cornea 42 at and with the orientation in the X, Y, Z coordinate system. The straight 54 runs here parallel to the Z axis and along the optical path of the radius 20. If in the preset position 56 on or in (e.g., after unveiling intracerebral tissue by deflecting the tissue plate (flap) in LASIK, i.e. Laser In Situ Keratomileusis), the cornea 42 is removed from the eye tissue, the rotation of the eye 22 to that shown by the straight line 60 of the eye 22 leads to position deflection actual tissue removal relative to the tissue removal target position 56, as in the prior art - eye tracking refers only to the two-dimensional registration of the pupil center 52.In this case, the rotary movement leads to a lateral translation of the set position 56 relative to the actual position 58 along the X and Z axes.

[0035] The orientation of the pupil removal process can therefore be undesirable. On the other hand, the orientation of the removal process on the visual axis may be advantageous. The visual axis is located near the optical axis of the eye and extends approximately through the corneal apex and the center of the eye lens.

[0036] Eye tracking according to the invention is based on the temporal recording of cross-sectional images of the eye by interferometric image recording based on three-dimensional optical coherence tomography. The analysis module 16 may temporarily determine the spatial position and orientation of the removed tissue segment or the treated segment of the eye tissue (e.g., as part of cataract surgery) and its translational and rotational movement, and transmit a representative signal for this data based on the connection via the three-dimensional image information. 24 to the laser control system 36 to set the focal point of the treatment laser according to a signal representative of the recorded data. In addition, the eye tracking according to the invention for controlling the focus may be based, for example, on Apex 40, whose position - in contrast to the center of the pupil 52 - does not change with variable irradiation. In addition, the invention makes it possible to select from the cross-sectional images the orientation means for laser removal which is placed close to the tissue to be treated, i.e. for example apex 40 as a means of orienting to corneal surgery 42. It is advisable to register at least two rectangular cross-sectional images 62, 64 of the eye 22, which represent a section substantially along the visual axis 50 or other suitable axis of the eye 22, see Fig. 4a. Alternatively or additionally, it is reasonable to register at least which is located close to the tissue to be treated, i.e. for example, apex 40 as a means of orienting the corneal procedure 42. It is reasonable to register at least two rectangular cross-sectional images 62, 64 of the eye 22, which represent a section substantially along the visual axis 50 or other the corresponding axis of the eye 22, see Fig. 4a. Alternatively or additionally, it is reasonable to register at least which is located close to the tissue to be treated, i.e. for example, apex 40 as a means of orienting the corneal procedure 42. It is reasonable to register at least two rectangular cross-sectional images 62, 64 of the eye 22, which represent a section substantially along the visual axis 50 or other the corresponding axis of the eye 22, see Fig. 4a. Alternatively or additionally, it is reasonable to register at least

One cross-sectional image 66 of the eye 22, which represents the cross section substantially along the edge 68 of the iris 44 (i.e. the pupil edge) of the eye 22, see FIG. 4b. It is also possible to three-dimensional, especially temporary, complete image recording (three-dimensional tomography) consisting of multiple cross-sectional images parallel to cross-sectional image 62, multiple cross-sectional images parallel to cross-sectional image 64 and / or multiple cross-sectional images parallel to cross-sectional image 66. Such complete recording The image may represent, e.g., temporal 3D topography of the cornea 42, on the basis of which translational and rotational eye movements can be determined and the laser beam radius at the point of this 3D topography (such as apex 40 cornea) can be determined.