Method and device for generating control data with an optimised cut geometry and cut sequence for correcting the refraction of an eye
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- CARL ZEISS MEDITEC AG
- Filing Date
- 2024-08-21
- Publication Date
- 2026-07-01
Smart Images
Figure EP2024073395_27022025_PF_FP_ABST
Abstract
Description
[0001] Method and device for generating control data with an optimized cutting geometry and cutting sequence for a correction of the refraction of an eye
[0002] The present invention relates to a planning method for generating control data for correcting the refraction of an eye with a main optical axis and a cornea by corneal modification, comprising receiving data representing a refractive correction requirement, calculating a corneal tissue volume to be removed, wherein the calculation is based on the refractive correction requirement, and calculating a cut surface completely surrounding the tissue volume, wherein the cut surface has a cap cut, a lenticule cut, a lateral cut, and an access cut. The present invention further relates to a corresponding planning unit, an ophthalmic laser therapy device, and a computer program product with program code.
[0003] Human vision defects have long been corrected with lenses in the form of eyeglasses. However, in recent years, various approaches have been developed to correct these defects by modifying the cornea. The modification alters the curvature of the cornea and thus the refractive power of the eye. This is typically achieved by removing corneal tissue. By removing corneal tissue from the eye, the refractive power of the cornea is altered in such a way that—taking into account the overall imaging properties of the eye—the refractive error is reduced or even completely eliminated (see, for example, US 6110166 A).
[0004] Carl Zeiss Meditec AG has developed a particularly gentle corneal modification procedure called SMILE. In this procedure, a femtosecond laser creates flat incisions in the cornea that enclose a lenticule-shaped piece of corneal tissue. This lenticule is removed from the cornea through an access incision (also called an incision). This changes the curvature of the anterior surface of the cornea (i.e., at the interface between the cornea and air). This change in curvature alters the refractive power of the cornea, thus correcting any refractive error.
[0005] To create the flat incisions in the cornea, laser radiation for treating the eye is focused within the tissue - i.e. below the surface of the tissue - in such a way that optical breakthroughs are created in the tissue. Various processes initiated by the laser radiation take place sequentially in the tissue. If the power density of the radiation exceeds a threshold, an optical breakthrough occurs, which creates a plasma bubble in the material. This plasma bubble grows after the optical breakthrough occurs due to expanding gases. If the optical breakthrough is not maintained, the gas created in the plasma bubble is absorbed by the surrounding material and the bubble disappears again. However, this process takes much longer than the formation of the bubble itself. A plasma bubble that separates previously joined layers of material is usually referred to as photodisruption.For simplicity, these processes are summarized here under the term "optical breakthrough." This term encompasses not only the actual optical breakthrough, but also the resulting effects in the material. If a large number of optical breakthroughs are created next to one another in the fabric, a flat cut (cut surface) can be created.
[0006] A cut surface that defines a lenticule in the cornea of an eye typically has a cap cut, a lenticule cut, a lateral cut, and an access cut. The cap cut (also called a cap cut or flap cut) limits the lenticule - the volume of tissue to be isolated in the cornea for removal - anteriorly, towards the front of the cornea. The lenticule cut limits the lenticule posteriorly, towards the retina of the eye. The lenticule cut can, for example, be created in one partial cut with a decreasing path radius (i.e. from the outside in) and in another partial cut with a increasing path radius (i.e. from the inside out) (cf. WO 2009 / 121593 A1). Lenticule cut and cap cut can also have partial cuts that are generated with different control of the laser beam source (cf. WO 2007 / 042190 A2).The lateral incision (also called sidecut or lenticule side cut) delimits the lenticule laterally relative to the main optical axis of the eye and extends to both the cap incision and the lenticule incision. The access incision extends to both the cap incision and the anterior aspect of the cornea. The access incision can thus be used to remove the (isolated) tissue volume contained within the cornea. The exact location of the access incision may vary from that of the cap incision (see also DE 10 2012 022 080 A1).
[0007] In a procedure that has been established for many years, the lenticule incision (including a transition zone) is first created from the outside to the inside, followed by the lateral incision, then the cap incision (from the inside to the outside) and finally the access incision (cf. Shah, Rupal, and Samir Shah. “Effect of scanning patterns on the results of femtosecond laser lenticule extraction refractive surgery.” Journal of cataract and refractive surgery vol. 37,9 (2011 ): 1636-47. doi: 10.1016 / j.jcrs.2011 .03.056, and Ang, M., Gatinel, D., Reinstein, DZ et al. Refractive surgery beyond 2020. Eye 35, 362-382 (2021 ). https: / / doi.org / 10.1038 / s41433-020-1096-5). However, it has been shown that during the creation of the cuts, disturbances in the cornea can occur in the form of distortion, since the gas produced during the optical breakthrough creates pressure in the tissue.Additionally or alternatively, an opaque bubble layer (OBL) may form. Both effects can lead to the planned incisions not being made at the correct location in the cornea, and thus the individual incisions not being properly connected to define the lenticule to be removed. Furthermore, Chapter 11 of Sekundo, Walter (ed.) (2015): “Small Incision Lenticule Extraction (SMILE). Principles, Techniques, Complication Management, and Future Concepts.” Cham: Springer International Publishing (SpringerLink: Books) shows that an incision made after one of the aforementioned disorders has developed will exhibit irregularities that can lead to delayed visual recovery. This means that the time until best-corrected visual acuity is achieved postoperatively is extended.In addition, the described disturbances in the tissue can lead to individual incisions - such as the lenticule incision and the lateral incision - not being correctly connected to each other, which can lead to difficulties in removing the lenticule or to inaccurate refractive correction.
[0008] The object of the present invention is therefore to provide a method and a device for generating control data for correcting the refraction of an eye, which reduce the risk of disturbances due to distortions in the cornea and due to the formation of an OBL or prevent the occurrence altogether, so that the tissue volume to be removed is completely delimited and delayed visual recovery is prevented.
[0009] According to the invention, the object is achieved by the features of the independent claims. Preferred developments and refinements are the subject of the dependent claims.
[0010] A first aspect of the invention relates to planning methods for generating control data for correcting the refraction of an eye by corneal modification. The eye whose refraction is to be corrected has a principal optical axis and a cornea. The planning method, which can be carried out, for example, in a planning unit, comprises the step of receiving data representing a refraction correction requirement. Reception can occur via a first interface of the planning unit, via which the refraction correction requirement is provided. The first interface can be a plug or a socket for a cable (e.g., USB, Firewire, RS232, CAN bus, Ethernet, etc.); it can also be a wireless interface such as a WLAN, UMTS, or Bluetooth receiver.The planning method further comprises the step of calculating a tissue volume (also called a lenticule) of the cornea to be removed. The calculation is carried out based on the refractive correction required. The tissue volume is calculated in such a way that the refraction of the eye whose refraction is to be corrected can be corrected (changed or adjusted) according to the refractive correction required after the calculated tissue volume has been removed. The calculation can be carried out in a calculation device that is configured to receive the data on the refractive correction required, for example, via the aforementioned first interface. The calculation device can be a computer having a processor and a memory. The calculation device can comprise at least one processor or processing element, e.g., a CPU.A central processing unit (CPU) (optionally in the form of a microprocessor), a graphics processing unit (GPU), a tensor processing unit (TPU), and / or a field programmable gate array (FPGA). The computing device may comprise a computer memory, optionally a semiconductor memory chip. The processor may be configured to execute a computer program. The computer program may be stored in the computer memory.
[0011] In a further step, the planning process involves calculating a cutting surface that completely defines the tissue volume. This calculation can be performed using the calculation facility described above. Completely defining the cut surface means that the tissue volume may still be connected to the adjacent cornea via tissue bridges. These tissue bridges can be severed when the tissue volume is removed from the cornea. Any existing tissue bridges serve as "predetermined breaking points" when the tissue volume is removed. The calculated cutting surface is not limited to the boundary (edge) of the tissue volume.
[0012] The incision surface features a cap cut (also called a cap cut or flap cut), which delimits the tissue volume anteriorly, at least in sections. The cap cut thus delimits the tissue volume toward the front of the cornea, i.e., toward a boundary between the eye and the surrounding air. The cap cut can extend radially beyond the tissue volume, so that a section of the cap cut does not delimit the tissue volume. This means that, viewed from the main optical axis, the cap cut can be at a greater distance from the main optical axis than the tissue volume.
[0013] The incision surface also includes a lenticule cut, which delimits the tissue volume posteriorly. The lenticule cut thus delimits the tissue volume toward the lens or retina of the eye. The lenticule cut can also extend radially beyond the tissue volume.
[0014] In addition, the cut surface features a side cut (also called a lenticule side cut), which radially delimits the tissue volume relative to the main optical axis. The side cut extends at least to the cap cut and at least to the lenticule cut. The side cut can, for example, have the shape of the shell of a truncated cone (with a circular or elliptical base) or a cylinder (circular cylinder or elliptical cylinder). The side cut is preferably self-contained.
[0015] The incision surface also includes an access incision (also called an incision or incision) that extends from the front of the cornea at least to the cap incision. Typically, the access incision only extends over a limited azimuth angle relative to the main optical axis. The access incision can run perpendicular to the front of the cornea. However, it can also have an angle other than 90° relative to the front of the cornea. Preferably, the access incision is inclined so that a separation tool inserted through the cornea can be moved in the direction of the main optical axis during insertion, as this facilitates insertion. The access incision is therefore typically a cut that does not delimit or border the tissue volume. The access incision can be designed in the shape of a circular segment or as a stripe or line.
[0016] For the purposes of the application, the term “cut” is to be understood as a generic term for the cap cut, lenticule cut, lateral cut and access cut.
[0017] According to the invention, the calculated cap cut comprises an outer cap cut (also called clearance) and an inner cap cut. The outer cap cut extends radially from a maximum distance from the main optical axis at least to the side cut, and the inner cap cut extends radially from the main optical axis at least to the side cut.
[0018] The planning method further comprises the step of generating control data describing the cutting surface. This generation can be performed in the calculation device described above. According to the invention, the generated control data represent a schedule in which the outer cap cut occurs before the side cut, the side cut occurs before the lenticule cut, and the lenticule cut occurs before the inner cap cut. The schedule is therefore a chronological schedule.
[0019] In other words: If the control data is fed to an ophthalmic laser therapy device and the control data is executed there, the outer cap cut is created before the lateral cut, the lateral cut before the lenticule cut and the lenticule cut before the inner cap cut in the eye to be corrected.
[0020] The inventive workflow ensures that disturbances caused by corneal distortions and the formation of an OBL due to an initially high gas pressure caused by an optical breakthrough during the creation of the incision surface are shifted to an area—namely, the outer cap incision—where these disturbances have little influence on the refraction to be corrected, as they have little or no impact on the shape (geometry) of the tissue volume to be removed. It has been observed that, surprisingly, the resulting gas pressure dissipates along the incisions already created, so that even for incisions that delimit the tissue volume (at least in sections) (such as the lateral incision, the lenticule incision, and the inner cap incision), the gas pressure can dissipate toward the outer cap incision.The described cutting sequence ensures that for most cuts there is a connection to a radially outer area - namely the outer cap cut - so that this area can serve as a "reservoir" for pressure equalization.
[0021] It should be noted that other cuts can be made before, after, or between the aforementioned cuts. However, preferably no further cut is provided in the schedule between the outer cap cut and the lateral cut, as well as between the lateral cut and the lenticule cut, and / or between the lenticule cut and the inner cap cut. In other words, the outer cap cut is advantageously made immediately before the lateral cut, the side cut is advantageously made immediately before the lenticule cut, and / or the lenticule cut is advantageously made immediately before the inner cap cut. In this way, the risk of the eye whose refraction is to be corrected moving during the cuts is reduced. The risk of the cuts no longer extending relative to one another as desired is reduced, so that the tissue volume to be removed can be reliably and completely defined.
[0022] The planning method according to the invention preferably comprises the step of providing the control data. The provision can be performed via the first interface as described above; however, the provision can also be performed via a second interface that is different from the first interface.
[0023] It should be noted that the described planning procedure can be performed without requiring the eye requiring refraction correction to be connected to an ophthalmic laser therapy device. Rather, all steps of the planning procedure can be performed well (e.g., hours or days) before a laser therapy procedure, so that the control data is already available before the eye is optically coupled to the ophthalmic therapy device.
[0024] According to an advantageous embodiment of the planning method, the control data is generated in such a way that it represents a schedule in which the inner cap cut is performed before the access cut. Since the access cut has only minimal influence on the refractive correction to be achieved, it is advantageous to perform this cut only after all cuts that delimit the tissue volume to be removed.
[0025] Alternatively, the planning process is designed to generate the control data to represent a schedule in which the access cut occurs before the outer canopy cut. This allows pressure equalization to occur not only via the outer canopy cut but also via the access cut, further reducing the occurrence of disturbances due to distortion or OBL.
[0026] In a further advantageous embodiment, the planning method is characterized in that the lenticule incision has a central zone and a transition zone, or consists of a central zone and a transition zone. The central zone intersects the main optical axis. The transition zone adjoins the central zone radially and extends at least as far as the lateral incision.
[0027] Typically, the central zone of the lenticule incision extends to a radial distance from the main optical axis of between 2 mm and 4 mm, preferably between 2.5 mm and 3.5 mm. The transition zone of the lenticule incision adjoins this radially; it thus "connects" the central zone with the lateral incision. The transition zone can extend radially over a range of more than 0 mm up to 2 mm, preferably between 0.05 mm (e.g., for a sphero-cylinder; in some countries also at least 0.25 mm) and 1.5 mm. If hyperopia is to be corrected, the transition zone typically extends radially over at least 1 mm.The shape (particularly the curvature) of the central zone, together with the shape (particularly the curvature) of the inner cap cut, essentially determines the geometry of the tissue volume to be removed radially around the main optical axis and is thus essentially responsible for refractive correction through corneal modification (corneal harvesting). Therefore, the central zone extends to the above-mentioned preferred radial distances from the main optical axis to ensure that the central zone contains the largest possible proportion of the cornea used (and corrected) for imaging the retina of the eye, even when the pupil of the eye to be corrected is wide open. The radial distance is preferably larger than the wide-open pupil of the eye (for example, when seeing in the dark; during scotopic vision).
[0028] The purpose of the transition zone of the lenticule incision is to smooth the front surface of the cornea after the tissue volume has been removed, so that only a small cavity remains in the cornea after the removal; preferably, no cavity remains. Thus, the transition zone typically does not serve to correct the curvature in the central region of the front surface of the cornea (around the main optical axis); rather, it is responsible for "smoothing" the front surface of the cornea in an area that is not typically used for imaging light onto the retina. Furthermore, smoothing can prevent re-epithelialization of the front surface of the cornea.
[0029] Dividing the lenticule cut into a transition zone and a central zone is particularly advantageous when the refractive correction required is hyperopia, since in this case the radius of curvature of the central zone is smaller than that of the cap cut. Such a division can also be advantageous when correcting myopia with astigmatism. However, when correcting pure (spherical) myopia, a transition zone can be omitted.
[0030] According to an advantageous further development of the aforementioned embodiment of the planning method, the control data is generated in such a way that it represents a schedule in which the transition zone occurs before the central zone. This means that when the control data is executed in an ophthalmic laser therapy device, the transition zone of the lenticule cut is generated first in the eye to be corrected, followed by the central zone of the lenticule cut.
[0031] In this way, it is ensured that any gas pressure occurring in both the transition zone and the central zone can equalize towards the outer cap cut (via the side cut).
[0032] Preferably, the central zone in the schedule is directly adjacent to the transition zone.
[0033] In a further advantageous embodiment, the planning method is characterized in that the control data further represent an execution of the lenticule cut, in which the cut is executed with a decreasing distance from the main optical axis. Thus, in this embodiment, the generated control data represents not only a schedule, but also a temporal execution of a cut—in this case, the lenticule cut. In other words: if the generated control data are executed on an ophthalmic laser system, the lenticule cut is created from the outside (greater radial distance from the main optical axis) to the inside (up to the main optical axis).
[0034] If the lenticule cut consists of a multitude of optical apertures created using laser pulses, the trajectory along which the laser pulses are temporally introduced into the cornea can be spiral or elliptical. The trajectory can also be circular or elliptical with decreasing radii.
[0035] If the lenticule cut has a transition zone and a central zone (or consists of these two zones), the control data represent a schedule in which the transition zone occurs before the central zone. The control data additionally represents an execution of the two zones of the lenticule cut from the outside to the inside. According to an advantageous embodiment of the planning method, it is characterized in that the control data further represent an execution of the lateral cut in which the lateral cut is executed in the direction of a retina of the eye. When the control data are executed, the lateral cut is thus executed such that the cut occurs from the side of the cut facing the front of the cornea towards the side facing the retina. The cut is generated as from anterior to posterior.
[0036] In this way, there is advantageously a connection to the outer cap cut already at the beginning of the creation of the side cut (as soon as the side cut and the outer cap cut touch), so that any resulting gas pressure can equalize in the direction of the outer cap cut.
[0037] If the lateral cut consists of a multitude of optical breakthroughs generated using laser pulses, the lateral cut can be created in the form of adjacent circular or elliptical paths from the front (anterior) to the back (posterior). Alternatively, the lateral cut can also be created in the form of a spiral path (or an elliptical spiral path) or a helix or coil (from front to back). It is also conceivable for the lateral cut to be composed of a multitude of cuts, each created from anterior to posterior for a fixed azimuth angle (or azimuth angle range of less than 5°) with respect to the main optical axis.
[0038] In prior art methods, as described at the beginning, it is customary to perform the lateral incision in such a way that it is created at a decreasing distance from the front of the cornea. The reason for this is that it can be avoided that the laser beam (including its beam cone) irradiates an already formed gas bubble. This causes a type of "shadowing," which would lead to a deterioration in beam quality, so that the desired optical breakthrough might not occur. In a further advantageous embodiment, the planning method is therefore characterized in that the lateral incision is calculated in such a way that an imaginary extension of the lateral incision beyond the front of the cornea encloses an angle of a > 90° with the tangent to the front of the cornea at the intersection point of the imaginary extension, preferably a > 105°, particularly preferably a > 120°.The angle a between the extension of the lateral incision and the tangent at the front of the cornea is measured outside the cornea in the direction of the main optical axis.
[0039] If the lateral cut and the cap cut are calculated in this way, the lateral cut can be carried out particularly easily from anterior (front) to posterior (back) without the laser beam (including its beam cone) penetrating an already formed gas bubble, which could result in shadowing.
[0040] According to an advantageous embodiment, the planning method is characterized in that the control data further represent an execution of the outer cap cut, in which the outer cap cut is executed in the direction of the main optical axis. When the control data is executed, the outer cap cut is thus executed over time with a decreasing distance from the main optical axis. The reduction can be monotonous or strictly monotonous. If the outer cap cut is composed of a plurality of optical apertures generated by laser pulses, the path along which the laser pulses are introduced into the cornea over time can have the shape of a spiral (strict monotony). The path can also have the shape of circles with decreasing radii (monotony). If the outer cap cut is generated using an elliptical spiral or ellipses, the two semi-axes can decrease (strictly) monotonically.
[0041] If the control data ensures that the outer cap cut is created from the outside inward, it can be advantageously ensured that initial disturbances caused by distortions in the cornea or by the formation of an OBL due to an initially high gas pressure caused by an optical breakthrough during the creation of the cut surface occur in a region of the cornea that is as far as possible from a corneal area used for imaging light onto the retina. Thus, the gas pressure of a later-created section of the outer cap cut can be balanced toward the first-created section.
[0042] In a further advantageous embodiment, the planning method is characterized in that the control data further represent an execution of the inner cap cut, in which the inner cap cut is executed away from the main optical axis. When the control data is executed, the inner cap cut is thus executed over time with an increasing distance from the main optical axis. The enlargement can be monotonic or strictly monotonic. If the inner cap cut is composed of a large number of optical breakthroughs generated by laser pulses, the path along which the laser pulses are introduced into the cornea over time can have the shape of a spiral (strict monotonicity). The path can also have the shape of circles with increasing radii (monotonicity). If the inner cap cut is generated using an elliptical spiral or ellipses, the two semi-axes can increase (strictly) monotonically.
[0043] If the control data ensures that the inner cap cut is created from the inside out, this can advantageously ensure that at locations in the central region of the cornea (i.e., near the main optical axis), the time between the first lenticule cut (or its central zone) and the subsequently created, overlying inner cap cut is minimized. This minimizes potential tissue distortion caused by the gas from the lenticule cut, since the distortion caused by the gas only occurs over time. It is also particularly advantageous to create the lenticule cut (or its central zone) from the outside in.
[0044] According to an advantageous embodiment, the planning method is characterized in that the cap section is calculated such that the outer cap section extends radially beyond the side section in the direction of the main optical axis. Additionally or alternatively, the cap section is calculated such that the inner cap section extends radially beyond the side section, viewed radially from the main optical axis. For this purpose, the inner or outer cap section preferably extends radially beyond the side section, viewed radially from the main optical axis, by at least 5 pm, particularly preferably by at least 20 pm or by at least 50 pm.
[0045] If the inner and / or outer cap incision extends radially outwards or inwards beyond the lateral incision, this advantageously ensures that the tissue volume is completely delimited for removal even in the event of slight movements of the eye to be corrected during the creation of the incisions.
[0046] According to an advantageous further development of the aforementioned design of the planning method, the inner cap incision and the outer cap incision at least partially overlap. This advantageously ensures that the tissue volume is completely delimited for removal, even with slight lateral movements of the eye to be corrected during the creation of the incisions.
[0047] According to a further advantageous (additional or alternative) development of the aforementioned embodiment of the planning method, this is characterized in that the lateral incision extends beyond the inner and / or outer cap incision. This means that the minimum distance of the lateral incision to the front of the cornea is less than the distance of the intersection point of the lateral incision with the inner and / or outer cap incision from the front of the cornea. In this way, it can also be advantageously ensured here that even in the event of slight lateral movements of the eye to be corrected during the creation of the incisions, the tissue volume is completely delimited for removal. For this purpose, the lateral incision preferably extends beyond the inner and / or outer cap incision by at least 5 μm, particularly preferably by at least 20 μm or by at least 50 μm.In a further advantageous embodiment, the planning method is characterized in that the cap cut is calculated such that a distance of the outer cap cut from the front of the cornea is greater than a distance of the inner cap cut from the front of the cornea.
[0048] A cap cut typically extends parallel to the front of the cornea. This means that for any point on the cap cut, the shortest distance to the front of the cornea is constant. This means that the distance to the front corresponds exactly to the distance along the (local) surface normal to the cap cut. If both the inner and outer cap cuts extend parallel to the front of the cornea, this constant distance across the inner cap cut (in the configuration described here) is smaller than the constant distance across the outer cap cut.
[0049] If the inner and / or outer cap cut do not extend parallel to the front of the cornea, the distances to the front are determined and (radially) averaged where the side cut extends to the inner or outer cap cut, ie where the side cut touches or intersects the inner / outer cap cut.
[0050] Alternatively, the planning method is characterized in that the cap cut is calculated such that a distance of the outer cap cut from the front of the cornea is smaller than a distance of the inner cap cut from the front of the cornea.
[0051] Particularly preferably (in both alternatives), the cap cut is additionally calculated such that the outer cap cut extends radially in the direction of the main optical axis beyond the side cut, and / or that the inner cap cut extends radially from the main optical axis beyond the side cut, and / or that the side cut extends beyond the inner and / or outer cap cut. For this purpose, the inner and / or outer cap cut (or the side cut) preferably extends radially from the main optical axis (or axially in a direction parallel to the main optical axis) by at least 5 pm beyond the side cut (or beyond the inner and / or outer cap cut), particularly preferably it extends by at least 20 pm or 50 pm.In this way, it can be particularly well ensured that even in the event of slight movements of the eye to be corrected during the creation of the incisions, the tissue volume is completely defined for removal.
[0052] According to an advantageous embodiment, the planning method is characterized in that the access incision is calculated such that it extends to the outer cap incision. The access incision can extend to the outer cap incision at any radial distance from the main optical axis. Therefore, the access incision does not have to extend to the outer cap incision at a maximum radial distance. This advantageously ensures that the cap incision (which preferably occurs after the inner cap incision or as the last incision of the calculated incision surface) extends to the outer cap incision, even in the event of slight movement of the eye to be corrected during the creation of the incisions.Advantageously, the cap incision extends beyond the outer cap incision, viewed from the front of the cornea, preferably by at least 5 pm, particularly preferably by at least 20 pm or 50 pm.
[0053] If the generated control data is intended for an ophthalmic laser therapy device that has a contact lens through which the eye to be corrected can be coupled to the laser therapy device, the access incision can be calculated such that it extends from a location on the anterior surface of the cornea that radially does not reach the boundary defined by the contact lens. At the same time, the outer cap incision can extend to this boundary.
[0054] An access incision at a smaller radial distance from the main optical axis than the maximum radial extent of the outer cap incision is particularly advantageous when follow-up treatment of a previously corrected eye is required. In this case, when creating a new access incision, which is usually formed as a flap incision, the previously created access incision does not need to be considered if the new access incision is placed at the outer, radial edge of the outer cap incision.In this case, this new access incision can advantageously be created particularly easily, since the inventive sequence of the incisions and their execution particularly efficiently reduces disturbances caused by distortions in the cornea as well as by the formation of an OBL due to an initially high gas pressure due to an optical breakthrough during the creation of the incision surface, so that the geometry of the outer cap incision is also retained and can therefore be particularly easily hit by the new access incision.
[0055] It is known that there are contact lenses for ophthalmic laser therapy devices that feature a so-called "gas escape." This gas escape allows gas to escape from the eye via the access incision through a section of the contact lens surface that is in contact with the front of the cornea. According to an advantageous development of the described embodiment, the planning method is characterized in that the access incision is calculated such that it extends on the front of the cornea to a location that can be assigned to a gas escape of a contact lens. The calculation therefore takes into account the geometry and, if applicable, the orientation of a contact lens that is to be used for the planned refractive correction procedure. This ensures that any gas pressure that occurs can be equalized from the eye via the access incision.Additionally or alternatively, the access incision can extend to the edge of the contact lens. For femtosecond LASIK, this is described as an example in: Wu, Ningling; Christenbury, Joseph G.; Dishler, Jon G.; Bozkurt, Tahir Kansu; Duel, Daniel; Zhang, Lijun; Hamilton, D. Rex (2017), "A Technique to Reduce Incidence of Opaque Bubble Layer Formation During LASIK Flap Creation Using the VisuMax Femtosecond Laser.", Journal of refractive surgery (Thorofare, NJ: 1995) 33 (9), pp. 584-590. DOI: 10.3928 / 1081597X-20170621-06. This can further reduce the risk of OBL occurring. A second aspect of the invention relates to a planning unit for generating control data for correcting the refraction of an eye by corneal modification.The planning unit has a computing device designed to receive data representing a refraction correction requirement and to carry out a planning method according to one of the embodiments described above. The computing device can comprise at least one processor or processing element, e.g. a CPU (central processing unit) (optionally in the form of a microprocessor), a GPU (graphics processing unit), a TPU (tensor processing unit) and / or an FPGA (field programmable gate array). The computing device can comprise a computer memory, optionally a semiconductor memory chip. The processor can be configured to execute a computer program. The computer program can be stored in the computer memory.
[0056] Furthermore, the calculation device is designed to provide the generated control data.
[0057] To receive the data representing the refractive correction requirement and to forward said data to the calculation device, the planning unit further comprises a first interface connected to the calculation device. This allows the calculation device (via the first interface) to receive the information about the refractive correction requirement for generating the control data.
[0058] Furthermore, the planning unit has a second interface connected to the computing device via which the generated control data is provided—for example, to an ophthalmic laser therapy device in which the generated control data can be executed. The second interface can be identical to the first interface.
[0059] The interfaces of the planning unit can be a plug or socket for a cable (e.g., USB, Firewire, RS232, CAN bus, Ethernet, etc.); it can also be a wireless interface such as a WLAN, UMTS, or Bluetooth receiver.
[0060] A third aspect of the invention relates to an ophthalmic laser therapy device. According to the invention, this device comprises a planning unit as described above. Furthermore, the laser therapy device has a control unit that is connected to the planning unit via the second interface for receiving the control data for controlling the ophthalmic laser therapy device. The control data generated in the planning unit can thus be provided via the second interface, which can be configured as described above, so that they can be executed by the ophthalmic laser therapy device to correct the refraction of an eye (according to its refraction correction requirements). The control data can form a control data set for this purpose. The control unit is connected to the devices of the ophthalmic laser therapy device described below in order to control them.This is typically done using signal data transmitted from the control unit to the various devices via signal data lines or wirelessly. The signal data is generated in the control unit based on the provided control data.
[0061] The control unit can typically access all controllable devices of the ophthalmic laser therapy device. It can be a single-part or multi-part unit and can communicate with the controllable devices of the ophthalmic laser therapy device via wired or wireless communication channels.
[0062] The ophthalmic laser therapy device further comprises a laser device for providing a laser beam, preferably a pulsed laser beam. The laser device is preferably a device that provides laser pulses with a pulse duration of femtoseconds or picoseconds, and whose focused laser beam is capable of severing the tissue of a patient's eye by means of optical breakdown due to nonlinear absorption. For this purpose, the laser device can comprise, for example, a femtosecond laser or a picosecond laser.
[0063] A femtosecond laser, for example, has a wavelength in a range from 750 nm to 1100 nm. However, the use of femtosecond lasers at other wavelengths is also conceivable in principle. The pulse duration of a femtosecond or picosecond laser that can be used here can be selected from a pulse duration range of 50 fs to 5 ps. The pulse energy of a femtosecond or picosecond laser that can be used here is advantageously in a pulse energy range of 20 nJ to 2 pJ. A pulse energy of approximately 130 nJ is particularly preferred. Typically, a laser device can provide laser pulses with a laser pulse frequency of up to 50 MHz. However, the laser device can be designed to reduce the laser pulse frequency.
[0064] The ophthalmic laser therapy device further comprises a focusing device for focusing the laser beam at a focus for transecting the cornea. The focusing device is designed to focus the laser beam in the tissue of the patient's eye, so that an optical breakthrough is achieved at the focus. The focusing device is preferably designed to take into account the optical properties of the patient's eye (such as the radii of curvature of the optically effective interfaces—for example, on the cornea—or the refractive indices of the tissue being irradiated). Furthermore, the focusing device can be designed to generate a focus of the laser beam in the tissue of the patient's eye, with a contact lens arranged in front of the patient's eye in the beam path.
[0065] In addition, the ophthalmic laser therapy device includes a scanning device for shifting the focus of the laser beam in the cornea of the eye to create the cutting surface.
[0066] The scanning device of the ophthalmic laser therapy device allows the focus of the laser beam to be shifted or scanned within the tissue of the eye. Scanning the laser beam should be possible without restriction in all three spatial directions: x, y, and z. The scanning device should therefore be designed to perform both lateral scans in the x and y directions as well as z scans along the optical axis of the pulsed laser beam.
[0067] The ophthalmological laser therapy device according to the invention allows the control data generated by the planning unit to be used in such a way that a cutting surface can be created in an eye by means of (pulsed) laser radiation, wherein the cutting surface completely delimits a tissue volume, so that by removing the tissue volume from the cornea via the access incision, the refraction of the eye can be corrected according to its refraction correction requirement.The control data provided by the planning unit represent a schedule that particularly efficiently reduces the occurrence of disturbances caused by distortions in the cornea and by the formation of an OBL, since the initial high gas pressure during the creation of the incision surface is shifted to an area (namely the outer cap incision) in which these disturbances have little influence on the refraction to be corrected, since the shape (geometry) of the tissue volume to be removed is not affected at all or only minimally.
[0068] It should be noted that ophthalmic laser therapy devices according to the description are particularly suitable for generating the calculated incision surface due to their high precision. In principle, the planning unit according to the invention (configured to execute a planning method according to the invention in one of the above-described forms and embodiments) is not limited to use in a laser-based device. The calculated control data can also be used in a device that can generate an incision surface in the eye using a different mechanism of action.
[0069] A fourth aspect of the invention relates to a computer program product with program code. If this program code is loaded into a computer, it executes a planning method as described above. A fifth aspect of the invention relates to a method for correcting the refraction of an eye through corneal modification. According to the invention, the method comprises planning steps according to a planning method as described above. Furthermore, the method comprises cutting the cornea of the eye according to the calculated cutting area. Furthermore, the method comprises removing the tissue volume from the cornea of the eye through the access incision.
[0070] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.
[0071] The invention is explained in more detail below with reference to exemplary embodiments and figures, which also disclose essential features of the invention. They show:
[0072] - Fig. 1 is a schematic diagram of the creation of a cutting surface in an eye using a laser beam;
[0073] - Fig. 2 shows a section through the cornea of an eye with a cut surface as produced by a prior art method;
[0074] - Fig. 3 shows a section through the cornea of an eye with a cut surface as produced according to a first embodiment of the method according to the invention without a transition zone - for example for a myopic refraction correction requirement;
[0075] - Fig. 4 shows a section through the cornea of an eye with a cut surface as produced according to a second embodiment of the method according to the invention with a transition zone - for example for a hyperopic refraction correction requirement;
[0076] - Fig. 5 shows a section through the cornea of an eye with a cut surface as produced according to a third embodiment of the method according to the invention (with transition zone);
[0077] - Fig. 6 shows a diagram of an embodiment of an ophthalmic laser therapy device according to the invention. Fig. 1 shows a schematic diagram for creating a cut surface in an eye using a laser beam. A laser beam 115 is concentrated into a focus 125 by means of a focusing device 120. For simplicity, the focusing device 120 is shown here as a single lens. It is understood that the focusing device 120 can have multiple diffractive and / or refractive optical elements. The focusing device 120 is designed such that it can create a focus 125 within the tissue of an eye 70; the tissue here is the cornea 80 of the eye 70. At the focus 125, the energy of the laser beam 115 is so great that an optical breakthrough is caused in the cornea 80.If a plurality of optical apertures are created adjacent to one another in the cornea 80, a cut surface 10 can be created. In Fig. 1, the cut surface 10 delimits a tissue volume 60 (represented by a dot pattern). If this tissue volume 60 is removed from the cornea 80 of the eye 70 via an access incision (not shown), the refraction of the eye 70 can be corrected.
[0078] Fig. 2 shows a cross-sectional image through the cornea of an eye with a cut surface as created according to a flowchart for a prior art method. The cut through the cornea encompasses the main optical axis A. The prior art example shown relates to a tissue volume 60 to be removed (represented by a dot pattern) for the correction of hyperopia. For this purpose, the lenticule cut is divided into a transition zone 42 and a central zone 44. According to the prior art flowchart, the transition zone 42 is created first, then the central zone 44, then the lateral cut 30, followed by the cap cut 20. Finally, the access cut 50 is created. The order in which the cuts are created according to the prior art flowchart is represented by the numbers 1 to 5 in the arrows.The arrows represent the directions in which the cuts are made: Both the transition zone 42 and the central zone 44 of the lenticule cut are created with decreasing distance from the main optical axis A (shown as a dashed line); see the arrow directions of arrow 1, which is assigned to the transition zone 42, and of arrow 2, which is assigned to the central zone 44. The cap cut 20, on the other hand, is created with increasing distance from the main optical axis A; see the arrow directions of arrow 4, which is assigned to the cap cut 20. The lateral cut 30 is made with decreasing distance from the front surface 85 of the cornea; see the arrow direction of arrow 3, which is assigned to the lateral cut 30. The lateral cut 30 is therefore created away from the retina (not shown) of the eye.Finally, the access incision 50 is made at a decreasing distance from the anterior surface 85 of the cornea; see the direction of arrow 5, which is associated with the access incision 50.
[0079] If myopia with astigmatism is to be corrected, the transition zone 42 is typically very small. In this case, the prior art deviates from the sequence described above and sometimes creates the central zone 44 first, followed by the transition zone 42, the lateral cut 30, and the cap cut 20.
[0080] Fig. 3 shows a cross-sectional image (as in Fig. 2) through the cornea of an eye with a cut surface 10, as generated according to a flowchart for a first embodiment of the planning method according to the invention. In this embodiment, the lenticule cut 40 is not divided into a central zone and a transition zone. This can occur, for example, in a myopic refractive correction (without astigmatism).
[0081] According to the flowchart of the first embodiment, the outer cap cut 22 is created first, then the side cut 30, then the lenticule cut 40, followed by the inner cap cut 24. Finally, the access cut 50 is created. The order of creating the cuts according to the flowchart is also represented here by the numbers 1 to 5 in the arrows.
[0082] The flow chart of this embodiment ensures that disturbances caused by distortions in the cornea or by OBL are shifted to an area where these effects have little impact on the result of the refractive correction, namely the outer cap incision 22. If the side incision 30 is created, the outer cap incision 22 is already present, so that a pressure increase occurring in the area of the side incision 30 can be compensated in the direction of the outer cap incision 22. The same applies to the lenticule incision 40: if this is created, a pressure increase via the side incision 30 can be compensated in the direction of the outer cap incision 22. Finally, this also applies to the inner cap incision 24: if this is created, a pressure increase in the direction of the outer cap incision 22 can be compensated.For all of the aforementioned incisions created after the outer cap incision 22 according to the schedule, a connection to the outer cap incision 22 is provided, through which an increase in pressure can be compensated. This ensures that the incisions delimiting the tissue volume 60 to be removed (represented by a dot pattern) can be created with particular precision, thus reducing the risk of delayed visual recovery and meeting the desired refractive correction requirement with particular precision.
[0083] Deviating from the sequence shown in Fig. 3, the access incision 50 could also be created before or between the other mentioned incisions in the flowchart. However, it is advantageous to create the access incision after the inner cap incision 24 or before the outer cap incision 22, since this allows the tissue volume 60 to be removed to be cut in the shortest possible time.
[0084] In principle, the aforementioned cuts can each be created in any direction. However, there is an advantageous embodiment for each cut. This is represented by the directions of the arrows: The outer cap cut 22 is advantageously created with decreasing distance from the main optical axis A; see direction of arrow 1, which is assigned to the outer cap cut 22. The outer cap cut 22 is therefore made in the direction of the main optical axis A. In this way, a pressure increase that occurs near the tissue volume 60 to be removed can already be compensated in the direction of greater radial distances from the main optical axis A (i.e. away from the tissue volume 60). Additionally or alternatively, the creation of the lateral cut 30 is advantageously carried out with increasing distance from the front side 85 of the cornea; see direction of arrow 2, which is assigned to the lateral cut 30.The lateral cut 30 is therefore created in the direction of the retina (not shown) of the eye. This advantageously ensures that a connection to the outer cap cut 22 is already present at the beginning of the creation of the lateral cut 30, via which connection any increasing pressure can be compensated. The lenticule cut 40 is additionally or alternatively advantageously created with a decreasing distance from the main optical axis A; see direction of arrow 3, which is assigned to the lenticule cut 40. This advantageously ensures that a connection to the outer cap cut 22 (via the lateral cut 30) is already present at the beginning of the creation of the lenticule cut 40, via which connection any increasing pressure can be compensated. Finally (additionally or alternatively) the inner cap cut 24 is advantageously created with an increasing distance from the main optical axis A; seeDirection of arrow 4, which is assigned to the inner cap cut 24. The inner cap cut 24 is therefore made away from the main optical axis A. This has the advantage that the time that elapses between the creation of the lenticule cut 40 (or its central zone 44, which is described in Fig. 4) in a central area around the main optical axis A and the creation of the inner cap cut 24, also in the central area around the main optical axis A, is particularly minimized. Since this area is particularly critical for vision (and visual acuity) during the day (with a relatively small "daylight pupil" of the eye), the influence of any minimal distortions in the tissue that may occur is minimized. Finally, the access cut 50 is (additionally or alternatively) made at a decreasing distance from the front surface 85 of the cornea; see direction of arrow 5, which is assigned to the access cut 50.
[0085] It is particularly advantageous to perform not just individual cuts, but all of the aforementioned cuts in the manner (direction) described. Fig. 3 also shows angle a, which is formed by an imaginary extension (shown as a dotted line) of the lateral cut 30 beyond the front surface 85 of the cornea with a tangent (shown as a line of dots and dashes) at the intersection point of the imaginary extension with the front surface 85 of the cornea. Angle a is determined at the intersection point of the front surface 85 of the cornea and the imaginary extension of the lateral cut 30. Angle a is measured outside the cornea of the eye and in the direction of the main optical axis A. Angle a shown in Fig. 3 is greater than 90°.In this way, the creation of the lateral cut 30 can be carried out particularly easily from anterior to posterior, since an influence (shading) of the laser beam (including its beam cone) by gas bubbles that have already formed can be avoided.
[0086] Fig. 4 shows a cross-sectional image (as in Figs. 2 and 3) through the cornea of an eye with a cut surface 10, as generated according to a flowchart for a second embodiment of the planning method according to the invention. In this embodiment, the lenticule cut is divided into a central zone 44 and a transition zone 42. This can occur, for example, in a myopic refractive correction need with astigmatism (as shown here in Fig. 4) or in a hyperopic refractive correction need.
[0087] According to the flowchart of the second embodiment, the outer cap cut 22 is created first, then the side cut 30, then the transition zone 42 of the lenticule cut, then the central zone 44 of the lenticule cut, followed by the inner cap cut 24. Finally, the access cut 50 is created. The order of creating the cuts according to the flowchart is also represented here by the numbers 1 to 6 in the arrows.
[0088] The advantages of the flow chart have already been discussed in connection with Fig. 3. By dividing the lenticule cut 40 from Fig. 3 into a central zone 44 and a transition zone 42, whereby according to the flow chart the creation of the central zone 44 takes place after the transition zone 42, it is additionally advantageously ensured that even during the creation of the central zone 44, a pressure increase in the direction of the outer cap cut 22 can be compensated (via the previously created transition zone 42 and the side cut 30).
[0089] In principle, in the second embodiment, the aforementioned cuts can also be created in any direction. However, here too, there is an advantageous embodiment for each cut. This is again represented by the directions of the arrows. In addition to the cut embodiments discussed in relation to Fig. 3, the transition zone 42 is advantageously created with a decreasing distance from the main optical axis A; see the direction of arrow 3, which is assigned to the transition zone 42. In this way, it is advantageously ensured that, right at the start of the creation of the transition zone 42, a connection to the outer cap cut 22 (via the side cut 30) is present, via which any pressure increase that occurs can be compensated. Additionally or alternatively, the central zone 44 is advantageously created with a decreasing distance from the main optical axis A; see the direction of arrow 4, which is assigned to the central zone 44.In this way, it is advantageously ensured that already at the beginning of the creation of the central zone 44 there is a connection to the outer cap cut 22 (via the side cut 30 and the transition zone 42), via which a pressure increase that occurs can be compensated.
[0090] Angle a is also shown in Fig. 4. As in Fig. 3, it is also greater than 90°; it amounts to approximately 120°.
[0091] Fig. 5 shows a sectional image (as in Figs. 2, 3 and 4) through the cornea of an eye with a cutting surface 10, as generated according to a flow chart for a third embodiment of the planning method according to the invention. In this embodiment too (as in Fig. 4 for the second embodiment), the lenticule cut 40 is divided into a central zone 44 and a transition zone 42. The curvatures of the central zone 44 and the inner cap cut 24 are suitable in this example for correcting a need for hyperopic refractive correction; however, the flow chart according to the third embodiment is not limited to such a need for refractive correction. In contrast to the second embodiment, in this third embodiment the outer cap cut 22 and the inner cap cut 24 have different distances to the front side 85 of the cornea. Within the outer 22 and inner 24 zones, respectively, the outer cap cut 22 and the inner cap cut 24 are at different distances from the front side 85 of the cornea.In the example shown, the distances to the front side 85 of the inner 24 cap cut are constant (the distance is determined locally along a surface normal on the cap cut); the distance from the front side 85 to the outer cap cut 22 is greater than the distance to the inner cap cut 24. The cut geometry shown here can advantageously ensure that the tissue volume 60 is completely delimited for removal, even with slight movements of the eye to be corrected during the creation of the cuts. Alternatively, the inner cap cut 24 could also have a greater distance to the front side 85 of the cornea than the outer cap cut 22.
[0092] Furthermore, for the embodiment shown in Fig. 5, the inner cap cut 24 is calculated such that it extends radially (as viewed from the main optical axis A) beyond the side cut 30. In addition, the outer cap cut 22 is calculated such that it also extends radially (as viewed from the main optical axis A) beyond the side cut 30. Finally, the side cut 30 is calculated such that it extends beyond both the outer cap cut 22 and the inner cap cut 24. The three aforementioned cuts therefore not only extend towards one another, but each extend beyond an intersection point. This advantageously ensures that the tissue volume 60 is completely delimited for removal, even in the event of slight movements of the eye to be corrected during the creation of the cuts.This advantage is not only limited to cut surfaces 10 where the distance of the outer cap cut 22 to the front surface 85 of the cornea is greater than that of the inner cap cut 24. Rather, the advantage can also be achieved with the same distances.
[0093] In the third embodiment, the angle a (not shown) can also have a value of more than 90°. Fig. 6 schematically illustrates an embodiment of an ophthalmic laser therapy device 100. During operation of the ophthalmic laser therapy device 100, a laser device 110 emits a pulsed laser beam 115. The laser beam 115 is deflected laterally (in the x and y directions) by a scanning device 130 and axially (z direction) by another scanning device 135. A focusing device 120 focuses the pulsed laser beam 115 into a focus 125 in the cornea 80. Fig. 6 shows an example of the focus 125 for two positions in the cornea 80 for different settings of the lateral scanning device 130 and the axial scanning device 135. A possibly existing, advantageous fixation of the eye by means of a patient interface relative to the ophthalmological laser therapy device 100 is not shown.
[0094] During operation, the laser device 110, the scanning devices 130, 135, and the focusing device 120 are controlled fully automatically via signal data transmitted from a control unit 140 to the respective devices 110, 120, 130, 135. This is indicated by arrows pointing from the control unit 140 to the devices 110, 120, 130, and 135, respectively. The control unit 140 ensures suitably synchronous operation of the laser device 110, the three-dimensional scanning devices 130, 135, and, if applicable, the focusing device 120. The signal data can be transmitted via signal data lines or wirelessly. The signal data required during operation is determined in the control unit 140 based on the control data. The control unit 140 receives the control data beforehand from the planning unit P as a control data set via unspecified communication paths such as control lines (in Fig.6 as a solid line between the planning unit P and the control unit 140). The control data can also be transmitted using memory chips (e.g., via USB or memory stick), magnetic storage devices (e.g., floppy disks), wirelessly via radio (e.g., WLAN, UMTS, Bluetooth), or wired (e.g., USB, Firewire, RS232, CAN bus, Ethernet, etc.). As an alternative to direct communication, it is also possible to arrange the planning device P spatially separate from the control unit 140 and to provide a corresponding data transmission channel. The transmission preferably takes place before the operation of the ophthalmological laser therapy device 100, i.e., before control signals are transmitted to the laser device 110, the scanning devices 130, 135, and, if applicable, to the focusing device 120.
[0095] The control data record is transmitted to the control unit 140 of the ophthalmic laser therapy device 100 via interface S2 of the planning device P. Preferably, operation of the ophthalmic laser therapy device 100 is blocked until a valid control data record is available at the control unit 140. A valid control data record can be a control data record that is generally suitable for use with the control unit 140 of the ophthalmic laser therapy device 100. In addition, validity can also be linked to the passing of further tests. For this purpose, it can be checked, for example, whether additional information about the ophthalmic laser therapy device 100, e.g., a device serial number, or about the patient, e.g.,a patient identification number, match other information that was, for example, read out on the ophthalmic laser therapy device 100 or entered separately as soon as the patient is in the correct position for operation of the ophthalmic laser therapy device 100.
[0096] The planning device P generates the control data or control data set, which is provided to the control unit 140 of the ophthalmic laser therapy device 100 for performing the surgical procedure. In the embodiment shown here, the refraction correction requirement is entered via an input device (not shown) and provided to the planning unit P via interface S1. The input device can be part of the ophthalmic laser therapy device 100.
[0097] The planning unit P comprises a calculation device C. This is connected to the interface S1 and receives the refraction correction requirement of the eye. In the calculation device C, control data for correcting the refraction of the eye by means of corneal modification are then calculated. The control data are transmitted to the control unit 140 via the further interface S2. Using the transmitted control data, the control unit 140 can generate signal data and transmit it to the devices 110, 120, 130, 135, so that a cut surface 10 can be created in the cornea 80 of the eye.
[0098] It should be noted again that the planning unit P can generate the control data regardless of whether the eye is connected to the ophthalmic laser therapy device 100 or not. The features of the invention mentioned above and described in various embodiments can be used not only in the specified exemplary combinations, but also in other combinations or alone, without departing from the scope of the present invention.
[0099] A description of a device related to process features applies analogously to the corresponding process with regard to these features, while process features represent functional features of the described device.
Claims
Patent claims 1. Planning method for generating control data for correcting the refraction of an eye (70) having a main optical axis (A) and a cornea (80) by corneal modification, comprising - Receiving data representing a need for refraction correction, - Calculating a tissue volume (60) of the cornea (80) to be removed, the calculation being based on the refractive correction requirement, - Calculating a cut surface (10) that completely delimits the tissue volume (60), wherein the cut surface (10) comprises o a cap cut (20) that delimits the tissue volume (60) anteriorly at least in sections, o a lenticule cut (40) that delimits the tissue volume (60) posteriorly, o a self-contained lateral cut (30) that delimits the tissue volume (60) radially with respect to the optical main axis (A) and that extends at least to the Cap cut (20) and extends at least to the lenticule cut (40), and o an access cut (50) extending from a front side (85) of the cornea (80) at least to the cap cut (20), wherein the cap cut (20) comprises o an outer cap cut (22) extending radially from a maximum distance to the main optical axis (A) at least to the side cut (30), and o an inner cap cut (24) extending radially from the main optical axis (A) at least to the side cut (30), and - generating control data describing the cutting surface (10), wherein the control data further represent a schedule in which o the outer cap cut (22) is made before the side cut (30), o the side cut (30) is made before the lenticule cut (40) and o the lenticule cut (40) is made before the inner cap cut (24).
2. Planning method according to claim 1, characterized in that the flow chart additionally represents that the inner cap cut (24) is made before the access cut (50).
3. Planning method according to claim 1, characterized in that the flow chart additionally represents that the access cut (50) takes place before the outer cap cut (22).
4. Planning method according to one of the preceding claims, characterized in that the lenticule cut (40) has a central zone (44) and a transition zone (42), wherein the central zone (44) intersects the main optical axis (A), and wherein the transition zone (42) radially adjoins the central zone (44) and extends at least as far as the lateral cut (30).
5. Planning method according to claim 4, characterized in that the schedule additionally represents that the transition zone (42) occurs before the central zone (44).
6. Planning method according to one of the preceding claims, characterized in that the control data further represent an execution of the lenticule cut (40) in which the cut is carried out with a decreasing distance from the main optical axis (A).
7. Planning method according to one of the preceding claims, characterized in that the control data further represent an execution of the lateral cut (30) in which the lateral cut (30) is executed in the direction of a retina of the eye (70).
8. Planning method according to one of the preceding claims, characterized in that the lateral cut (30) is calculated such that an imaginary extension of the lateral cut (30) beyond the front side (85) of the cornea (80) encloses an angle a > 90°, preferably a > 105, particularly preferably a > 120°, with a tangent to the front side (85) at the intersection point with the imaginary extension, wherein the angle is measured outside the cornea (80) in the direction of the main optical axis A.
9. Planning method according to one of the preceding claims, characterized in that the control data further represent an execution of the outer cap cut (22), in which the outer cap cut (22) is executed in the direction of the main optical axis (A).
10. Planning method according to one of the preceding claims, characterized in that the control data further represent an execution of the inner cap cut (24) in which the inner cap cut (24) is executed away from the main optical axis (A).
11. Planning method according to one of the preceding claims, characterized in that the cap cut (20) is calculated such that - the outer cap cut (22) extends radially in the direction of the main optical axis (A) beyond the side cut (30), and / or the inner cap cut (24) extends radially beyond the side cut (30) when viewed from the main optical axis (A).
12. Planning method according to claim 11, characterized in that the inner cap cut (24) and the outer cap cut (22) at least partially overlap.
13. Planning method according to one of claims 1 to 11, characterized in that the cap cut (20) is calculated such that a distance of the outer cap cut (22) from the front side (85) of the cornea (80) is greater than a distance of the inner cap cut (24) from the front side (85) of the cornea (80).
14. Planning method according to one of the preceding claims, characterized in that the access cut (50) is calculated such that it extends to the outer cap cut (22).
15. Planning unit (P) for generating control data for correcting the refraction of an eye (70) by corneal modification, comprising - a calculation device (C) which is designed to o carry out a planning method according to one of the preceding claims, o receive the data representing the refraction correction requirement, and o provide the generated control data, - a first interface (S1) for receiving the data representing the refraction correction requirement and for forwarding it to the calculation device (C), and - a second interface (S2) for providing the generated control data.
16. Ophthalmic laser therapy device (100), comprising - a planning unit (P) according to claim 15, - a control unit (140) connected to the planning unit (P) via the second interface (S2) for receiving the control data for controlling the ophthalmological laser therapy device (100), - a laser device (110) for providing a laser beam (115), - a focusing device (120) for focusing the laser beam (115) in a focus (125) for severing the cornea (80), and - a scanning device (130, 135) for shifting the focus (125) of the laser beam (115) in the cornea (80) of the eye to produce the cutting surface (10).
17. A computer program product comprising program code which, when loaded into a computer, executes a method according to any one of claims 1 to 14.
18. A method for correcting the refraction of an eye (70) by corneal modification, comprising - Carrying out a planning method according to one of claims 1 to 14, - cutting the cornea (80) of the eye (70) according to the calculated control data, and - Removing the tissue volume (60) from the cornea (80) of the eye (70) through the access incision (50).