Method for providing control data for an ophthalmic surgical laser of a treatment device, control device and treatment device

Abstract

Method for providing control data for an ophthalmic surgical laser (12) of a treatment device (10) for the removal of a tissue (14), the method comprising the following steps carried out by a control device (18): - determining (S10) a wavefront of a cornea of ​​a human or animal eye (16) from predetermined examination data; - determining (S12) Zernike polynomials from the determined wavefront, wherein the Zernike polynomials describe imaging errors; - calculating (S14) a respective tissue geometry for each Zernike polynomial, wherein the respective tissue geometry indicates a change in the cornea to correct the imaging errors and wherein a combination of a selection of the Zernike polynomials describes a tissue removal geometry; - determining (S16) a subgroup of the determined Zernike polynomials by means of an optimization calculation, by means of which one or more Zernike polynomials are selected for the subgroup if they satisfy a predetermined optimization condition, wherein the optimization condition is predetermined by a maximized target corneal geometry and an imaging correction to be achieved, wherein the target corneal geometry is determined from a difference between a corneal geometry and the tissue removal geometry; - determining (S18) an optimized tissue removal geometry of the tissue to be removed by means of the determined subgroup of Zernike polynomials, wherein the optimized tissue removal geometry is determined by means of a combination of the tissue geometries of the Zernike polynomials of the subgroup; - Providing (S20) the control data for controlling the ophthalmic surgical laser (12) which uses the optimized tissue removal geometry to separate the tissue (14); - where the Zernike polynomials are assigned to the subgroup with a factor determined by the optimization calculation, where a value between 0 and 1 is calculated for the factor, where a respective Zernike polynomial with factor 0 is not assigned to the subgroup and a Zernike polynomial with factor 1 is fully assigned to the subgroup.

Description

[0001] The present invention relates to a method for providing control data for an ophthalmic surgical laser of a treatment device for removing tissue. The invention also relates to a treatment device comprising at least one ophthalmic surgical laser and at least one control device for carrying out the method, a computer program, and a computer-readable medium.

[0002] Treatment devices and methods for controlling ophthalmic lasers to correct optical refractive errors and / or pathologically or abnormally altered areas of the cornea are known in the art. For example, pulsed lasers and a beam focusing device can be configured such that laser pulses in a focus located within the organic tissue cause photodisruption and / or photoablation in order to remove tissue, particularly a tissue lenticle, from the cornea. Treatments for compensating optical refractive errors are becoming increasingly precise. For example, the LASIK procedure (laser in situ keratomileusis) can correct a variety of refractive errors, such as myopia, hyperopia, and astigmatism.

[0003] A disadvantage of previous LASIK procedures was the creation of spherical aberrations, such as halos, and reduced contrast sensitivity. To avoid these aberrations and also correct existing aberrations of the eye, it is known to incorporate wavefront measurements of the eye into treatment planning. In particular, a wavefront from a wavefront analysis can be decomposed into Zernike polynomials of several orders, where each of the Zernike polynomials can describe a refractive or aberration effect of the eye. In other words, Zernike polynomials can be used to represent wavefronts, which in turn describe aberrations of optical systems.

[0004] The problem with current treatment procedures is that, while attempts are made to correct aberrations, this sometimes results in the removal of more tissue than necessary. The disadvantage is that once removed, tissue from the eye is either impossible or very difficult to reconstruct, which can be detrimental to the patient.

[0005] US 2012 / 0035598 A1 discloses a device for generating control data for a laser device for surgically correcting refractive errors. The device calculates a radius of curvature to determine the control data. The cornea, which is reduced by a volume, has this radius of curvature. The radius of curvature is location-specific and is calculated using a predefined formula.

[0006] US 2016 / 0161764 A1 discloses lenses, devices, methods, and / or systems that take refractive errors into account. Embodiments are directed toward modifying or controlling the wavefront of light entering the human eye.

[0007] The invention is based on the object of providing control data for controlling an ophthalmic surgical laser for correcting a visual defect, in which the tissue of the resulting target cornea can be maximized.

[0008] This object is achieved by the method according to the invention, the devices according to the invention, the computer program according to the invention, and the computer-readable medium according to the invention. Advantageous embodiments with expedient refinements of the invention are specified in the respective subclaims, wherein advantageous embodiments of the method are to be regarded as advantageous embodiments of the treatment device, the control device, the computer program, and the computer-readable medium, and vice versa.

[0009] A first aspect of the invention relates to a method for providing control data for an ophthalmic laser of a treatment device for removing tissue, wherein the method comprises the following steps performed by a control device. A control device is understood to be a device, a device component, or a device group configured to receive and evaluate signals and to provide, for example, generate, control data. The control device can be configured, for example, as a control chip, computer program, computer program product, or control unit.The control device determines a wavefront of a cornea of ​​a human or animal eye from predetermined examination data, determines Zernike polynomials from the determined wavefront, wherein the Zernike polynomials describe imaging errors, and calculates a respective tissue geometry for each Zernike polynomial, wherein the respective tissue geometry indicates a change in the cornea to correct the imaging errors and wherein a combination of a selection of the Zernike polynomials describes a tissue removal geometry. In other words, a wavefront of a cornea of ​​the eye is first determined from previously determined examination data. The examination data can be obtained, for example, by retrieving the examination data from a data storage device or data server, or the examination data can be measured, for example, using the treatment device.For example, the wavefront can be determined from aberrometry, which can also be referred to as wavefront analysis and which can be performed, for example, using a Hartmann-Shack sensor. This wavefront can be decomposed into Zernike polynomials using known methods, whereby each Zernike polynomial can describe an aberration or a component of an aberration. For each Zernike polynomial, a respective tissue removal geometry can then be determined using known methods, in particular using the concept of equivalent defocus, where equivalent defocus is defined as the amount of defocus required to produce the same wavefront variance that can be found in one or more higher-order aberrations. In particular, a dioptric equivalent can be calculated that each Zernike polynomial has.A combination of one or more Zernike polynomials can describe a tissue removal geometry that specifies the geometry of the tissue that can be removed to correct the aberrations.

[0010] Furthermore, the control device determines a subgroup of the determined Zernike polynomials through an optimization calculation, by which one or more Zernike polynomials are selected for the subgroup if they satisfy a predetermined optimization condition. The optimization condition is predetermined by a maximized target corneal geometry and a to-be-achieved imaging correction, the target corneal geometry being determined from a difference between a corneal geometry and the tissue removal geometry. Furthermore, the control device determines an optimized tissue removal geometry of the tissue to be removed using the determined subgroup of Zernike polynomials, the optimized tissue removal geometry being determined using a combination of the tissue geometries of the Zernike polynomials of the subgroup.Finally, the control device can provide control data for controlling the ophthalmic laser, which uses the optimized tissue removal geometry to separate the tissue. In other words, one or more Zernike polynomials can be assigned to a subgroup through an optimization calculation if the corresponding Zernike polynomials satisfy a predefined optimization condition. The optimization condition can include achieving a desired image correction, i.e., correcting the refractive error, and maximizing a target corneal geometry, the geometry the cornea is expected to have after treatment.A maximized target corneal geometry is obtained by iteratively testing, through optimization, which combination of Zernike polynomials achieves the planned image correction for the treatment while simultaneously leaving a maximum amount of corneal tissue. Those Zernike polynomials that achieve this are assigned to the subgroup. This can always be done with an eye on the desired postoperative cornea, i.e., the target corneal geometry.Once the corresponding Zernike polynomials that achieve a maximum target corneal geometry have been determined and assigned to the subgroup, an optimized tissue removal geometry for removing the tissue can be determined from the Zernike polynomial of the subgroup by combining the tissue geometries of the Zernike polynomials of the subgroup, and the optimized tissue removal geometry can be provided to the ophthalmic laser for separating the tissue using control data.

[0011] The invention offers the advantage of further increasing safety during treatment with the device and also improving the degree of improvement for highly irregular corneas, as attention is no longer focused solely on the tissue to be removed, but rather on the target corneal geometry. Overall, the method minimizes the amount of tissue to be removed and maximizes the cornea after treatment, which can be gentler for the patient.

[0012] Furthermore, the invention provides that the Zernike polynomials are assigned to the subgroup with a factor determined by the optimization calculation, wherein a value between 0 and 1 is calculated for the factor, whereby a respective Zernike polynomial with a factor of 0 is not assigned to the subgroup, and a Zernike polynomial with a factor of 1 is fully assigned to the subgroup. In other words, it is provided that the Zernike polynomials are not only assigned to the subgroup in full or not at all, but also with a proportion assigned by the factor. This means that, for example, Zernike polynomials can only have a 50 percent share of the original value and are thus not fully included in the tissue removal geometry.Preferably, the factor can also assume the values ​​0 and 1, meaning that a respective Zernike polynomial with a factor of 0 is not assigned to the subgroup, and a Zernike polynomial with a factor of 1 is fully assigned to the subgroup. The factor can, in particular, be any real number between 0 and 1 and thus specify the proportion of the Zernike polynomial to the subgroup. This has the advantage that the target corneal geometry and the desired image correction can be determined even more precisely.

[0013] The invention also includes embodiments which provide additional advantages.

[0014] According to an advantageous embodiment, the imaging correction of the optimization condition specifies a refractive correction to be achieved. Those Zernike polynomials that achieve the refractive correction are permanently assigned to the subgroup. The remaining Zernike polynomials that are not permanently assigned to the subgroup are checked for the presence of the maximized target corneal geometry of the optimization condition. In particular, Zernike polynomials can describe a refractive correction and an aberration correction as imaging correction. In this embodiment, the Zernike polynomials specified for the refractive correction are permanently assigned to the subgroup, i.e., are not influenced by the optimization calculation.However, all other Zernike polynomials not responsible for the refractive correction can be checked for the fulfillment of the optimization condition by the optimization calculation in order to obtain a maximized target corneal geometry. For refractive correction, it is preferable that Zernike polynomials up to the second order are specified. This means that Zernike polynomials of the zeroth, first, and second orders, which describe the refractive correction, are permanently assigned to the subgroup. This design offers the advantage that a refraction can be reliably corrected during eye treatment, while simultaneously maximizing the target corneal geometry using the remaining Zernike polynomials.

[0015] In a further advantageous embodiment, it is provided that an aberration correction to be achieved is specified by the imaging correction of the optimization condition, wherein those Zernike polynomials by which the aberration correction is achieved are permanently assigned to the subgroup, and the remaining Zernike polynomials that are not permanently assigned to the subgroup are checked for the presence of the maximized target corneal geometry of the optimization condition. This means that in this embodiment, the aberration correction to be achieved is permanently specified by assigning the responsible Zernike polynomials to the subgroup, whereby the Zernike polynomials responsible for the refraction correction can consequently be checked for the presence of the maximized target corneal geometry. Preferably, it is provided that Zernike polynomials from the third order onwards are specified for the aberration correction.

[0016] It is advantageous that the optimization condition is specified by a resulting geometry and / or morphology and / or thickness of the target corneal geometry. In other words, the morphology of a patient's eye can be taken into account, and the optimization condition of the target corneal geometry can be adjusted accordingly. The geometry or thickness of the cornea can also be considered and specified, allowing attention to be paid to where more tissue is available for removal and where less. Thus, the target corneal geometry can be individually adapted for each patient, thereby improving safety and treatment outcomes.

[0017] According to a further advantageous embodiment, the optimization condition is met if a thickness or volume of the target corneal geometry is maximized. This means that either a thickness of the cornea can be maximized in the direction of an optical axis of the eye, or the total volume of the cornea is to be maximized for determining the target corneal geometry. Thus, a parameter for the optimization condition can advantageously be provided, which is to be iteratively improved.

[0018] According to a further advantageous embodiment, it is provided that a refractive power value, in particular a dioptric equivalent value, is determined for respective regions of the respective Zernike polynomials, wherein an assignment of the one or more Zernike polynomials to the subclass is carried out depending on at least one predetermined refractive power value range. In other words, regions of the Zernike polynomials have refractive power values ​​that can be present in particular as dioptric equivalent values. This means that each region of a respective Zernike polynomial represents a refractive power value, wherein the refractive power value can preferably be obtained by means of a calculation from a dioptric equivalent value. In particular, the Zernike polynomials can be represented with a radius-dependent part and an angle-dependent part, for example, like a wavefront map with contour lines, wherein the respective height can indicate the refractive power value.A dioptric equivalent value is the optical blur of the individual Zernike polynomial, which can be calculated in diopters. In this embodiment, a refractive power range can be specified as an optimization condition for the desired image correction. Zernike polynomials with refractive power values ​​within this refractive power range can be permanently assigned to the subgroup. The assignment of the Zernike polynomials to the subclass depending on the refractive power range represents a portion of the desired image correction. This means that the refractive power range can be considered a parameter of the desired image correction to verify the optimization condition.The refractive power value can preferably be given in diopters, and the refractive power range can represent a range with diopter values ​​that are to be fixedly corrected, for example, from less than -0.5 diopters to greater than 0.5 diopters. In particular, the refractive power range can have high diopter values, through which a high proportion of the correction of the refractive error can be taken into account. Particularly preferably, the respective Zernike polynomial assigned to the subclass can only be assigned to the respective range that has the refractive power value within the specified refractive power range. Thus, other ranges / portions of the Zernike polynomials can be disregarded and / or the other ranges can be optimized separately.

[0019] It is advantageous to specify a separate range of refractive power values ​​for each Zernike polynomial and / or for each order of Zernike polynomials. This allows for greater customization and allows different Zernike polynomials to be weighted differently when considering the refractive power values.

[0020] According to a further advantageous embodiment, it is provided that value range classes are specified with respective refractive power value ranges, wherein the respective ranges of the respective Zernike polynomials are classified into the specified value range classes depending on the refractive power value. The value range classes classify the importance of the respective range for the desired image correction. The assignment of one or more Zernike polynomials to the subclass is carried out depending on the value range classes. This means that ranges of the respective Zernike polynomials can have refractive power values ​​that can be assigned to value range classes. This can be done based on specified refractive power value ranges.The value range classes can specifically indicate how important the respective range is for the desired image correction, for example, how high the refractive power value is in this range. The assignment of the Zernike polynomials can then be performed based on these value range classes. For example, it can be specified that only Zernike polynomials with clinically relevant value ranges may be assigned to the subgroup. This allows for a simple and quick assignment of the most important Zernike polynomials to the subclass.

[0021] Preferably, at least one of the value range classes is selected, wherein Zernike polynomials with refractive power values ​​outside the selected value range class are permanently assigned to the subgroup, wherein, in addition, those refractive power values ​​that lie within the refractive power value range of the selected value range class are optimized by the optimization calculation within the refractive power value ranges of the selected value range classes to maximize the target corneal geometry. In other words, a value range class can be selected that is not permanently assigned to the subgroup. The refractive power values ​​that lie within the selected value range class can then be changed, preferably optimized, by the optimization calculation to maximize the target corneal geometry by changing the refractive power values ​​within the selected refractive power value range.This means that the contour lines of the Zernike polynomials may be modified by the optimization calculation if they lie within the selected refractive power range. Preferably, the refractive power values ​​within the refractive power range are modified to ultimately achieve the maximized target corneal geometry. This will be explained below using an example. For example, a value range class with clinically irrelevant refractive power values ​​can be selected, for example, refractive power values ​​between -0.25 diopters and +0.25 diopters. This means that all Zernike polynomials with refractive power values ​​above 0.25 diopters can be permanently assigned to the subgroup.However, the Zernike polynomials of the selected value range class can be modified by the optimization calculation, and a respective refractive power value within the selected value range class can be optimized between -0.25 diopters and +0.25 diopters to ultimately achieve a maximized target corneal geometry. Alternatively, multiple value range classes can be selected, whose refractive power values ​​are optimized within the refractive power range of the selected value range classes. For example, in addition to the value range class with a value of 0.25 diopters, the value range class with a value of up to 0.5 diopters can be selected, whereby the refractive power values ​​of these two value range classes can then be modified within the value of 0.5 diopters to achieve the maximized target corneal geometry.

[0022] Preferably, it is provided that at least one of the value range classes is selected, wherein the refractive power values ​​of all value range classes are optimized by the optimization calculation to maximize the target corneal geometry, wherein the refractive power values ​​are increased or reduced for optimization by a respective optimization value, wherein the respective optimization value lies within the refractive power value ranges of the selected value range classes. This means that at least one of the value range classes can initially be selected, by means of which a refractive power value range can be specified. The refractive power values ​​of all value range classes can then be increased or reduced based on the selected refractive power value range, wherein the optimization value with which the refractive power values ​​of all value range classes can be increased or reduced must lie within the refractive power value range of the selected value range class.This will be illustrated below using an example. For example, a value range class can again be selected that has refractive power values ​​up to 0.25 diopters. In another value range class, a Zernike polynomial in one range can have a value of 0.7 diopters, whereby this refractive power value can be changed by the selected 0.25 diopters in the optimization calculation. This means that the refractive power value of the Zernike polynomial can be changed between 0.45 diopters and 0.95 diopters, i.e. 0.7 diopters + -0.25 diopters. Accordingly, all other refractive power values ​​of each value range class can be adjusted by the optimization value specified by the selected value range class. Thus, all refractive power values ​​can preferably be minimally optimized to achieve a maximized target corneal geometry.The optimization value can preferably be selected so that the image correction is still sufficient, but tissue can be saved.

[0023] It is particularly preferred that the ranges of the Zernike polynomials are divided into three value range classes, wherein the first value range class comprises refractive power values ​​of less than 0.25 diopters and is classified as clinically irrelevant, the second value range class comprises refractive power values ​​between 0.25 diopters and 0.5 diopters and is classified as possibly clinically relevant, and the third value range class has refractive power values ​​above 0.5 diopters and is classified as clinically relevant, wherein Zernike polynomials that have the third value range class or a combination of the second and third value range classes are permanently assigned to the subgroup, wherein the remaining Zernike polynomials that are not permanently assigned to the subgroup are checked for the presence of the maximized target corneal geometry of the optimization condition.The previously specified diopter values ​​are to be understood as absolute values, meaning that the first value range class runs from -0.25 to 0.25 diopters, the second value range class from -0.5 to -0.25 and 0.25 to 0.5 diopters, and the third value range class from refractive power values ​​above 0.5 diopters and below -0.5 diopters. In particular, it is thus easy to specify whether only clinically relevant or potentially clinically relevant Zernike polynomials are permanently assigned, and the remaining Zernike polynomials are checked for the maximized target corneal geometry according to the optimization condition and may not be assigned to the subgroup.

[0024] A second aspect of the present invention relates to a control device that is configured to carry out one of the methods described above. This results in the advantages listed above. The control device can be designed, for example, as a control chip, control unit, or user program (“app”). The control device can preferably have a processor device and / or a data memory. A processor device is understood to be a device or device component for electronic data processing. The processor device can, for example, have at least one microcontroller and / or at least one microprocessor. A program code for carrying out the method according to the invention can preferably be stored on the optional data memory.The program code can then be designed, when executed by the processor device, to cause the control device to carry out one of the above-described embodiments of one or both of the methods according to the invention.

[0025] A third aspect of the present invention relates to a treatment device comprising at least one ophthalmic surgical laser for separating a tissue predefined by the control data, in particular a corneal volume with predefined interfaces of a human or animal eye by means of photodisruption and / or photoablation, and at least one control device for the laser(s) configured to carry out the steps of the method according to the first aspect of the invention. The treatment device according to the invention makes it possible to reliably reduce or even avoid the disadvantages that occur when using conventional ablative treatment devices.

[0026] In a further advantageous embodiment of the treatment device according to the invention, the laser can be suitable for emitting laser pulses in a wavelength range between 300 nm and 1400 nm, preferably between 700 nm and 1200 nm, with a respective pulse duration between 1 fs and 1 ns, preferably between 10 fs and 10 ps, ​​and a repetition frequency greater than 10 kilohertz (kHz), preferably between 100 kHz and 100 megahertz (MHz). Such a femtosecond laser is particularly well suited for removing tissue within the cornea. The use of photodisruptive and / or photoablative lasers in the method according to the invention also has the advantage that the cornea does not have to be irradiated in a wavelength range below 300 nm. In laser technology, this range is referred to as "deep ultraviolet."This advantageously prevents unintentional damage to the cornea caused by these very short-wave and high-energy beams. Photodisruptive lasers of the type used here typically deliver pulsed laser radiation with a pulse duration between 1 fs and 1 ns into the corneal tissue. This allows the power density of the respective laser pulse required for optical breakthrough to be spatially limited, enabling high cutting precision when creating the interfaces. The wavelength range between 700 nm and 780 nm can also be selected.

[0027] In further advantageous embodiments of the treatment device according to the invention, the control device can have at least one storage device for at least temporarily storing at least one control data set, wherein the control data set(s) comprise control data for positioning and / or focusing individual laser pulses in the cornea; and can have at least one beam device for beam guidance and / or beam shaping and / or beam deflection and / or beam focusing of a laser beam of the laser. Said control data set comprises the control data for tissue removal determined in the method.

[0028] Further features and their advantages can be found in the descriptions of the first aspect of the invention, wherein advantageous embodiments of each aspect of the invention are to be regarded as advantageous embodiments of the other aspect of the invention.

[0029] A fourth aspect of the invention relates to a computer program comprising instructions which cause the treatment device according to the fourth aspect of the invention to carry out the method steps according to the first aspect of the invention and / or the method steps according to the second aspect of the invention.

[0030] A fifth aspect of the invention relates to a computer-readable medium on which the computer program according to the fourth aspect of the invention is stored. Further features and their advantages can be found in the descriptions of the first to fourth aspects of the invention, with advantageous embodiments of each aspect of the invention being regarded as advantageous embodiments of the other aspect of the invention.

[0031] Further features of the invention emerge from the claims, the figures and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the respective combination specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments are to be regarded as encompassed and disclosed by the invention that are not explicitly shown and explained in the figures, but which emerge and can be produced by separate combinations of features from the explained embodiments. Embodiments and combinations of features are also to be regarded as disclosed that therefore do not have all the features of an originally formulated independent claim.Furthermore, embodiments and combinations of features are to be considered disclosed, in particular by the embodiments presented above, which go beyond or deviate from the combinations of features presented in the claims. This shows: Fig. 1 a schematic representation of a treatment device according to the invention according to an exemplary embodiment; Fig. 2 is a schematic process diagram according to an exemplary embodiment; Fig. 3 a schematic representation of a Zernike pyramid.

[0032] In the figures, identical or functionally identical elements are provided with the same reference numerals.

[0033] The Fig. 1 shows a schematic representation of a treatment device 10 with an ophthalmic laser 12 for removing tissue 14 from a human or animal eye 16 by means of photodisruption and / or photoablation. The tissue 14 can, for example, represent a lenticule or solid body that can be severed from a cornea of ​​the eye 16 with the ophthalmic laser 12 to correct a visual impairment. A geometry of the tissue 14 to be removed, i.e., a tissue removal geometry 14, can be provided by a control device 18, in particular in the form of control data, so that the laser 12 emits pulsed laser pulses into the cornea of ​​the eye 16 in a pattern predefined by the control data in order to remove the tissue 14. Alternatively, the control device 18 can be a control device 18 external to the treatment device 10.

[0034] Furthermore, the Fig. 1, the laser beam 20 generated by the laser 12 can be deflected toward the eye 16 by means of a beam deflection device 22, namely a beam deflection apparatus such as a rotary scanner, in order to remove the tissue 14. The beam deflection device 22 can also be controlled by the control device 18 to remove the tissue 14.

[0035] The laser 12 shown can preferably be a photodisruptive and / or photoablative laser configured to emit laser pulses in a wavelength range between 300 nanometers and 1400 nanometers, preferably between 700 nanometers and 1200 nanometers, with a respective pulse duration between 1 femtosecond and 1 nanosecond, preferably between 10 femtoseconds and 10 picoseconds, and a repetition frequency greater than 10 kilohertz, preferably between 100 kilohertz and 100 megahertz. The control device 18 optionally also has a memory device (not shown) for at least temporarily storing at least one control data set, wherein the control data set(s) comprise control data for positioning and / or focusing individual laser pulses in the cornea.The position data and / or focusing data of the individual laser pulses, i.e. the tissue removal geometry 14, is determined using the method described below.

[0036] In Fig. Figure 2 shows a schematic process diagram for providing control data for the ophthalmic laser 12 of the treatment device 10 for the removal of the tissue 14. In a step S10, a wavefront of a cornea of ​​a human or animal eye 16 is determined from predetermined examination data. The wavefront can be determined, for example, by means of a wavefront analysis. Subsequently, in a step S12, Zernike polynomials can be determined from the determined wavefront, wherein the Zernike polynomials can describe imaging errors of the eye 16. A so-called Zernike pyramid 24 is shown, for example, in Fig. 3, where the Zernike polynomials from the zeroth order O0 to the eighth order O8 are schematically illustrated. Using the Zernike polynomials, a respective tissue geometry can then be calculated for each Zernike polynomial in a step S14. The tissue geometry can indicate a change in the cornea to correct an aberration, and a selection of the Zernike polynomials can describe a tissue removal geometry. This means that the appearance of the tissue described by one or more Zernike polynomials, which is to be removed to correct the aberration, is determined.

[0037] In a step S16, a subgroup of Zernike polynomials can then preferably be determined iteratively, which can provide a maximized target corneal geometry and a to-be-achieved imaging correction. This means that, on the one hand, a predetermined imaging correction is to be achieved that corrects the imaging aberration(s), and, on the other hand, the residual corneal tissue, i.e., the target corneal geometry, is to be maximized. To achieve this, an optimization calculation can be performed in which one or more Zernike polynomials are selected for the subgroup if they satisfy a predetermined optimization condition. The optimization condition can be predetermined by the maximized target corneal geometry and the to-be-achieved imaging correction.In particular, the target corneal geometry can be determined from a difference between an original corneal geometry and the tissue removal geometry, which can be determined by combining the selection of the Zernike polynomials.

[0038] Step S16 is to be carried out using the Fig. 3. As previously described, a respective Zernike polynomial with the respective order O0 to O8 is shown here, which were determined from the corneal wavefront. From the division into the individual Zernike polynomials, it can be seen that not all Zernike polynomials have the same correction component to correct the imaging error, but by applying some of the Zernike polynomials, only tissue is removed that does not contribute a large part to the imaging correction. In particular, the optimization calculation can determine which of the Zernike polynomials are primarily responsible for the imaging correction to be achieved and simultaneously result in the maximized target corneal geometry, whereby these can be assigned to the subgroup, which in Fig. 3, for example, is illustrated by the hatched Zernike polynomials.

[0039] Preferably, it can be provided that the image correction to be achieved can be specified as to whether a refraction correction or an aberration correction is to be achieved. Fig.In the exemplary embodiment illustrated in Figure 3, for example, a refraction correction can be specified, wherein the Zernike polynomials up to the second order O2 are specified for the refraction correction and are permanently assigned to the subgroup. This means that the Zernike polynomials up to the second order O2 are not taken into account by the optimization calculation, but belong directly to the subgroup. However, the Zernike polynomials 26 responsible for the aberration correction can be checked by the optimization calculation for the existence of the optimization condition and thus be assigned to the subgroup or not. Preferably, it can be provided that the Zernike polynomials 26 to be optimized are assigned to the subgroup with a factor determined by the optimization calculation, wherein the factor can have a value between 0 and 1.In other words, a Zernike polynomial assigned to the subgroup with a factor of 0 can be deactivated, meaning no assignment to the subgroup is possible, and a Zernike polynomial assigned to the subgroup with a factor of 1 is fully considered. Additionally, a Zernike polynomial of the 26 Zernike polynomials to be optimized can also be partially considered, meaning that the factor can assume an intermediate value between 0 and 1, for example, 0.75. In this case, the respective Zernike polynomial is only considered at 75 percent and has a correspondingly smaller tissue removal geometry and also a lower image correction.

[0040] Particularly preferably, it can be provided that refractive power values ​​are determined for respective ranges of the Zernike polynomials, wherein the assignment of the Zernike polynomials to the subclass is carried out depending on a predetermined refractive power range value. In particular, value range classes can be predetermined, with each value range class having its own refractive power value range. This means that a refractive power value that lies within a respective refractive power value range is assigned to a value range class. In particular, a first value range class can have refractive power values ​​of less than 0.25 diopters, a second value range class can have refractive power values ​​between 0.25 diopters and 0.5 diopters, and a third value range class can have refractive power values ​​above 0.5 diopters.For example, the first value range class can be classified as clinically irrelevant, and the optimization calculation can specify that Zernike polynomials that only have refractive power values ​​from the first value range class are not assigned to the subgroup. The second value range class can be classified as potentially clinically relevant and checked for the fulfillment of the optimization condition, and the third value range class can be classified as clinically relevant, whereby, for example, Zernike polynomials that have refractive power values ​​from the third value range class can be firmly assigned to the subgroup. Alternatively, the Zernike polynomials of the first and second value range classes can also be checked for the fulfillment of the optimization condition, in particular to determine which combination results in the maximized target corneal geometry.

[0041] Particularly preferably, at least one of the value range classes can also be selected, whereby the Zernike polynomials with refractive power values ​​outside the selected value range class can be permanently assigned to the subgroup. The refractive power values ​​within the value range class can, however, be varied by the optimization calculation such that they achieve a maximized target corneal geometry. For this purpose, it can be specified that the refractive power values ​​may only be varied within the refractive power value range specified by the value range class. This means that for a refractive power value range of up to 0.25 diopters, whereby this is to be understood as an absolute value and the refractive power value range therefore extends from -0.25 diopters to 0.25 diopters, the values ​​may be varied within this range such that the maximized target corneal geometry can ultimately be found.

[0042] After determining the subgroup through the optimization calculation, an optimized tissue removal geometry for removing the tissue can be determined in a step S18 by combining the Zernike polynomials of the subgroup. This tissue removal geometry, optimized by combining the Zernike polynomials of the subgroup, can finally be provided in a step S20 as control data for controlling the ophthalmic laser 12. This allows the desired treatment outcome to be achieved for a patient, while also increasing safety, since less corneal tissue needs to be removed, or the target corneal geometry can be better adapted to an individual patient's cornea, thus preserving a larger residual corneal volume.

[0043] Overall, the examples show how the invention can achieve maximum residual tissue for a cornea after treatment by the treatment device 10.

Claims

[1] Method for providing control data for an ophthalmic surgical laser (12) of a treatment device (10) for the removal of a tissue (14), the method comprising the following steps carried out by a control device (18): - determining (S10) a wavefront of a cornea of ​​a human or animal eye (16) from predetermined examination data; - determining (S12) Zernike polynomials from the determined wavefront, wherein the Zernike polynomials describe imaging errors; - calculating (S14) a respective tissue geometry for each Zernike polynomial, wherein the respective tissue geometry indicates a change in the cornea to correct the imaging errors and wherein a combination of a selection of the Zernike polynomials describes a tissue removal geometry; - determining (S16) a subgroup of the determined Zernike polynomials by means of an optimization calculation, by means of which one or more Zernike polynomials are selected for the subgroup if they satisfy a predetermined optimization condition, wherein the optimization condition is predetermined by a maximized target corneal geometry and an imaging correction to be achieved, wherein the target corneal geometry is determined from a difference between a corneal geometry and the tissue removal geometry; - determining (S18) an optimized tissue removal geometry of the tissue to be removed by means of the determined subgroup of Zernike polynomials, wherein the optimized tissue removal geometry is determined by means of a combination of the tissue geometries of the Zernike polynomials of the subgroup; - Providing (S20) the control data for controlling the ophthalmic surgical laser (12) which uses the optimized tissue removal geometry to separate the tissue (14); - where the Zernike polynomials are assigned to the subgroup with a factor determined by the optimization calculation, where a value between 0 and 1 is calculated for the factor, where a respective Zernike polynomial with factor 0 is not assigned to the subgroup and a Zernike polynomial with factor 1 is fully assigned to the subgroup. [2] Method according to claim 1, characterized bythat a refractive correction to be achieved is specified by the imaging correction of the optimization condition, whereby those Zernike polynomials by which the refractive correction is achieved are permanently assigned to the subgroup, whereby the remaining Zernike polynomials which are not permanently assigned to the subgroup are checked for the presence of the maximized target corneal geometry of the optimization condition. [3] Method according to claim 2, characterized by that Zernike polynomials up to the second order are specified for the refraction correction. [4] Method according to claim 1, characterized bythat an aberration correction to be achieved is specified by the imaging correction of the optimization condition, whereby those Zernike polynomials by which the aberration correction is achieved are permanently assigned to the subgroup, whereby the remaining Zernike polynomials which are not permanently assigned to the subgroup are checked for the presence of the maximized target corneal geometry of the optimization condition. [5] Method according to claim 4, characterized by that Zernike polynomials from the third order onwards are specified for the aberration correction. [6] Method according to one of the preceding claims, characterized by that the optimization condition is specified by a resulting geometry and / or morphology and / or thickness of the target corneal geometry. [7] Method according to one of the preceding claims, characterized bythat the optimization condition is met if a thickness or volume of the target corneal geometry is maximized. [8] Method according to one of the preceding claims, characterized by that a refractive power value, in particular a dioptric equivalent value, is determined for respective ranges of the respective Zernike polynomials, wherein an assignment of the one or more Zernike polynomials to the subclass is carried out depending on at least one predetermined refractive power value range. [9] Method according to claim 8, characterized by that a separate refractive power value range is specified for each Zernike polynomial and / or for each order of the Zernike polynomials. [10] Method according to claim 8 or 9, characterized bythat value range classes are specified with respective refractive power value ranges, whereby the respective ranges of the respective Zernike polynomials are classified into the specified value range classes depending on the refractive power value, whereby the value range classes classify how important the respective range is for the image correction to be achieved, whereby the assignment of the one or more Zernike polynomials to the subclass is carried out depending on the value range classes. [11] Method according to claim 10, characterized bythat at least one of the value range classes is selected, whereby Zernike polynomials with refractive power values ​​outside the selected value range class are permanently assigned to the subgroup, whereby in addition those refractive power values ​​which lie within the refractive power value range of the selected value range class are optimized by the optimization calculation within the refractive power value ranges of the selected value range classes in order to maximize the target corneal geometry. [12] Method according to claim 10; characterized by that at least one of the value range classes is selected, wherein the refractive power values ​​of all value range classes are optimized by the optimization calculation to maximize the target corneal geometry, wherein the refractive power values ​​are increased or reduced for optimization by a respective optimization value, wherein the respective optimization value lies within the refractive power value ranges of the selected value range classes. [13] Method according to one of claims 10 to 12, characterized by that the ranges of the Zernike polynomials are divided into three value range classes, whereby the first value range class comprises refractive power values ​​of less than 0.25 diopters and is classified as clinically irrelevant, the second value range class comprises refractive power values ​​between 0.25 diopters and 0.5 diopters and is classified as possibly clinically relevant, and the third value range class has refractive power values ​​above 0.5 diopters and is classified as clinically relevant, whereby Zernike polynomials which have the third value range class or a combination of the second and third value range classes are permanently assigned to the subgroup, whereby the remaining Zernike polynomials which are not permanently assigned to the subgroup are checked for the presence of the maximized target corneal geometry of the optimization condition. [14] Control device (18) which is designed to carry out a method according to one of the preceding claims. [15] Treatment device (10) with at least one ophthalmic surgical laser (12) for the removal of a tissue (14) of a human or animal eye (16), in particular a lenticule, by means of photodisruption and / or photoablation and at least one control device (18) according to claim 14. [16] Treatment device (10) according to claim 15, characterized by that the laser (12) is designed to emit laser pulses (20) in a wavelength range between 300 nm and 1400 nm, preferably between 700 nm and 1200 nm, with a respective pulse duration between 1 fs and 1 ns, preferably between 10 fs and 10 ps, ​​and a repetition frequency greater than 10 kHz, preferably between 100 kHz and 100 MHz. [17] Treatment device (10) according to one of claims 15 or 16, characterized bythat the control device (18) - at least one storage device for at least temporarily storing at least one control data set, wherein the control data set(s) comprise control data for positioning and / or focusing individual laser pulses in the cornea; and - at least one beam device (22) for beam guidance and / or beam shaping and / or beam deflection and / or beam focusing of a laser beam (20) of the laser (12). [18] Computer program comprising instructions causing the treatment device (10) according to any one of claims 15 to 17 to carry out a method according to any one of claims 1 to 13. [19] A computer-readable medium on which the computer program according to claim 18 is stored.

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