Method for providing control data for an ophthalmic laser treatment device, method for controlling a treatment device, control device, treatment device computer program, and computer-readable medium

Abstract

The invention relates to a method for providing control data for an ophthalmic laser (12) of a treatment device (10), wherein the method comprises the following steps performed by a control unit (18): determining a geometry of a preoperative cornea (30); receiving a predetermined refractive power change ΔD Soll , concerning a change in total corneal breakaway force D CT of the preoperative cornea (30); determining a preoperative cornea (30) to provide the specified refractive power change ΔD Soll , the volume of material to be removed (44).

Description

[0001] The invention relates to a method for providing control data for an ophthalmic laser of a treatment device according to the features of the preamble of claim 1. Furthermore, the invention relates to a method for controlling a treatment device according to the features of the preamble of claim 14, a control device according to the features of the preamble of claim 15, which is configured to carry out the respective method, a treatment device with such a control device according to the features of the preamble of claim 16, a computer program according to the features of the preamble of claim 17, comprising instructions that cause the treatment device to execute the method, and a computer-readable medium according to the features of the preamble of claim 18, on which the computer program is stored.

[0002] Treatment devices and methods for controlling ophthalmic lasers to correct refractive errors and / or pathologically or abnormally altered areas of the cornea are known in the prior art. For example, pulsed lasers and a beam focusing device can be configured such that laser pulses cause photodisruption and / or ablation in a focus located within the organic tissue in order to remove tissue, in particular a tissue lenticel, from the cornea.

[0003] To correct a refractive error of one eye, it is common practice in ophthalmological laser treatment procedures to determine the current refractive power D. 0,T a cornea of ​​the eye into a target refractive power D 2,Tto modify the cornea. Tissue is removed using laser pulses to alter the radius of curvature of an anterior corneal surface. The underlying principle is to change the actual radius of curvature of the anterior corneal surface to a desired radius of curvature, thereby altering the actual refractive power D. 0,CA the anterior surface of the cornea to a target refractive power D 2,CA the anterior surface of the cornea changes, thus compensating for the optical refractive error of the eye.

[0004] This simple approach alone, however, is insufficient to compensate for the eye's refractive error. The reason for this is that the total refractive power of the cornea is derived from the refractive power D 0,CA the anterior surface of the cornea, the refractive power D 0,CL the thickness of the cornea as well as the refractive power D 0,CP the posterior surface of the cornea is composed of: D0,CT=D0,CA+D0,CL+D0,CP

[0005] The tissue removal required to change the radius of curvature of the anterior surface also results in a change in the actual refractive power D. 0,CA changes in other components of the anterior surface of the cornea, which contribute to the actual refractive power D 0,T of the cornea. Other components can include a change in refractive power caused by a change in corneal thickness between the anterior and posterior corneal surfaces. To account for these additional changes in refractive power, it is common practice, according to current technology, to perform simple corrections to the tissue removal and / or to adjust the target refractive power change ΔD0.

[0006] These adjustments are not tailored to the individual laser treatment, but are based on statistics which offer sufficient accuracy, but have room for improvement.

[0007] Aspheric corrections incorporate induced aberrations, particularly spherical aberration, into the correction. However, most aspheric corrections on the market are either user-selectable, requiring a predefined initial corneal asphericity and a target asphericity. The resulting correction may not be neutral with respect to spherical aberrations, and the aberrations induced by the correction are not pre-compensated. So-called wavefront-optimized corrections on the market are based solely on the statistical induction of spherical aberrations measured across a sample population. The resulting correction may work on average, but not on an individual basis, and the aberrations induced by the correction are also not pre-compensated.

[0008] The invention is based on the objective of providing a method that enables a more precise change in the refractive power of a cornea.

[0009] This problem is solved by the inventive method for providing control data according to the features of claim 1, the inventive method for controlling a treatment device according to the features of claim 14, the inventive control device according to the features of claim 15, the inventive treatment device control device according to the features of claim 16, the inventive computer program according to the features of claim 17, and the inventive computer-readable medium according to the features of claim 18. Advantageous embodiments with expedient further developments of the invention are specified in the respective dependent claims, 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.

[0010] The method according to the invention is designed to perform corrections that effectively pre-compensate for the effects of removing an ablation volume from the tissue. According to the invention, the ablation volume removed from the tissue is described by a thick lens in order to determine the effects of the tissue removal. By describing the ablation volume as a thick lens, the depth of tissue ablation is taken into account when determining the resulting changes. In particular, this allows a focus shift caused by the tissue ablation to be determined and consequently compensated for.

[0011] One approach to theoretically compensating for the focus shift due to tissue removal is based on maintaining the position of the optical focus on an anterior corneal surface after tissue removal. In the context of refractive surgery, considering only the amount of tissue removed, but not corneal biomechanics or wound healing, and assuming the refractive index of the preoperative and postoperative corneas is identical, the approximate refractive shift attributable solely to tissue removal corresponds to the combination of both effects.

[0012] Several models can be applied, such as the described consideration of the ablated volume as a thick lens. These models yield very similar, though not identical, results, and all provide smaller corrections than when considering the ablated volume and / or the cornea as a thin lens.

[0013] A first aspect of the invention relates to a method for providing control data for an ophthalmic laser of a treatment device, wherein the method comprises the following steps, which are carried out by means of a control device. A control device is understood to be a device or device component, in particular a computer or processor, which can perform the following steps automatically or semi-automatically.

[0014] A first step involves determining the geometry of a preoperative cornea.

[0015] The procedure involves receiving a predetermined change in refractive power ΔD0 relating to a change in the actual total corneal refractive power D. 0,CT of the preoperative cornea to a target total corneal rupture force D 2,CT a postoperative cornea. In other words, the control unit receives instructions to change the total corneal billing force D. CTThe change in refractive power ΔD0 can, for example, be used to correct a refractive error.

[0016] The procedure involves identifying at least one temporary ablation volume to be removed from the preoperative cornea to provide the specified refractive power change ΔD0. In other words, the control unit identifies the tissue to be removed, described by the at least one temporary ablation volume, in order to achieve the specified refractive power change ΔD0 of the cornea by removing the at least one temporary ablation volume.

[0017] At least one of the preliminary ablation volume bodies shares a common surface with the cornea. In other words, the preliminary anterior body surface of the preliminary ablation volume body is identical to the anterior corneal surface of the cornea, or the preliminary posterior body surface of the preliminary ablation volume body is identical to the posterior corneal surface of the cornea. Consequently, the preliminary posterior body radius of curvature is identical to the posterior corneal radius of curvature, or the preliminary anterior body radius of curvature is identical to the anterior corneal radius of curvature.

[0018] In a subsequent step, an effective refractive power D is determined. KT,eff the removal volume is determined by the control unit. In other words, the effective breaking force D is obtained. KT,eff of the ablation volume body not only from the refractive force D 1,KAthe anterior body surface of the preliminary ablation volume body and the refractive power D 1,KP the posterior surface of the ablation volume. This results in an effective refractive power D KT,eff the ablation volume body may differ from the specified refractive force change ΔD0.

[0019] So that the one deviation of the effective refractive power D KT,eff Since the refractive power change ΔD0 of the preliminary ablation volume is reduced, it is necessary to take this deviation into account. This is done by using the specified refractive power change ΔD0 to determine the posterior body curvature radius R. KP a compensated refractive power change ΔD on the posterior surface of the ablation volume body Comp is used.

[0020] The compensated refractive power change ΔD Compis a value based on the given refractive power change ΔD0, which serves as an input for a recalculation of the posterior body radius of curvature R KP the posterior body surface of the ablation volume body is used, where the compensated refractive power change ΔD Comp is parameterized in such a way that a deviation of the effective refractive power D KT,eff the reduction of the ablation volume body from the specified refractive force change ΔD0 compared to using the specified refractive force change ΔD0.

[0021] In a further step, the ablation volume is determined again as a function of the compensated refractive power change ΔD. Comp , in order to effect the specified change in refractive power ΔD0. The resulting effective total body refractive power D KT,effThe ablation volume body exhibits a smaller deviation from the refractive power change ΔD0 to be set than the total body refractive power D. KT,eff of the ablation volume body, which was determined for the specified change in refractive index ΔD0.

[0022] A further step involves generating control data to direct the laser for ablating the ablation volume from the preoperative cornea. This control data can be configured to direct the laser's removal of the ablation volume from the cornea. The ablation volume can be positioned on the cornea such that its anterior surface lies within the anterior corneal surface of the preoperative cornea, and its posterior surface lies within the cornea, specifically between the anterior and posterior corneal surfaces of the preoperative cornea. Following ablation of the ablation volume, the postoperative cornea has an anterior corneal surface that corresponds to the posterior surface of the ablation volume.Thus, the anterior corneal surface of the postoperative cornea has a corneal radius of curvature that corresponds to the posterior body radius of curvature R. KP The control data can include a data set for positioning and / or focusing individual laser pulses in the cornea. Additionally or alternatively, the control data can include a data set for setting 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 respective laser.

[0023] The invention offers the advantage that by determining the refractive power of the ablation volume, the effects of tissue ablation can be determined and compensated for. At the same time, this approach requires less computational effort than wavefront-based methods.

[0024] The invention also includes further developments that result in additional advantages.

[0025] A further development of the invention provides that the first step involves determining at least one anterior actual corneal curvature radius R. 0,CA an anterior corneal surface of a preoperative cornea, a posterior actual corneal radius R 0,CP The control unit determines the anterior corneal curvature radius of the anterior corneal surface, the posterior corneal curvature radius of the posterior corneal surface, and the actual corneal thickness d0 as it appears before surgery. This determination can be based on measurement results provided to the control unit.

[0026] The at least one preliminary ablation volume body comprises a preliminary anterior body surface, which has a preliminary anterior body radius of curvature R. 1,KA exhibits. The at least one preliminary ablation volume body comprises a preliminary posterior body surface, which has a preliminary posterior body radius of curvature R. 1,KP The preliminary posterior body surface of the preliminary ablation volume can be a surface located posterior to, or behind, the anterior body surface of the ablation volume and may be situated within the corneal tissue. For example, the preliminary posterior body surface of the ablation volume may be located between the anterior corneal surface and the posterior corneal surface of the preoperative cornea.

[0027] The preliminary posterior radius of curvature R 1,KPas well as the preliminary anterior radius of curvature R 1,KA the preliminary anterior body surface of the preliminary ablation volume body as well as the preliminary thickness d 1,K The preliminary ablation volume is determined by the control unit as a function of the specified refractive force change ΔD0. The control unit determines the preliminary posterior body radius of curvature R. 1,KP as well as the preliminary anterior radius of curvature R 1,KA of the preliminary ablation volume body and the preliminary thickness d 1,K of the preliminary ablation volume body to provide the preliminary ablation volume body of the specified refractive force change ΔD0.

[0028] A further development of the invention provides that the at least one preliminary ablation volume body comprises the preliminary anterior body surface with the preliminary anterior body radius of curvature, wherein the preliminary anterior body radius of curvature has the anterior corneal radius of curvature of the anterior corneal surface of the preoperative cornea.

[0029] The ablation volume exhibits the preliminary posterior body surface with the preliminary posterior body radius of curvature R. 0,KP exhibits, where the preliminary posterior body radius of curvature R 0,KP depending on the preliminary anterior radius of curvature R 0,KA the anterior surface area of ​​the preliminary ablation volume and the predetermined refractive power change ΔD0, is determined to achieve a refractive power D 0,KPto provide the preliminary posterior body surface of the preliminary ablation volume body, which changes by the specified refractive power change ΔD0, from a refractive power D KA the preliminary anterior body surface of the preliminary ablation volume body differs.

[0030] In other words, the refractive power D is calculated 0,KA the preliminary anterior body surface of the preliminary ablation volume body from the known anterior body radius of curvature R 0,KA of the anterior body surface. The control unit determines the refractive power D. 0,KA the anterior body surface. From the refractive power D 0,KA The control unit determines the required refractive power D based on the anterior surface area of ​​the ablation volume body and the specified refractive power change ΔD0. 0,KPthe posterior body surface area required to provide the specified refractive power change ΔD0. From the determined refractive power D 0,KP The control unit determines the posterior body curvature radius R from the posterior body surface. 0,KP the posterior surface of the ablation volume body, which corresponds to a posterior surface of refractive power D 0,KP leads.

[0031] In a further step, the ablation volume is determined again as a function of the compensated refractive power change ΔD. Comp , in order to effect the specified change in refractive power ΔD0. The resulting effective total body refractive power D KT,eff The ablation volume body exhibits a smaller deviation from the refractive power change ΔD0 to be set than the total body refractive power D. KT,eff of the ablation volume body, which was determined for the specified change in refractive index ΔD0.

[0032] A further development of the invention provides that the at least one preliminary ablation volume body comprises the posterior body surface with a preliminary posterior body radius of curvature, wherein the preliminary posterior body radius of curvature R 1,KP the posterior corneal radius of curvature R 0,CP the posterior corneal surface of the preoperative cornea. The at least one preliminary ablation volume exhibits the anterior body surface with a preliminary anterior body radius of curvature R. 1,KA on, where the preliminary anterior radius of curvature R 1,KA depending on the preliminary posterior radius of curvature R 0,KP the posterior surface area of ​​the preliminary ablation volume and the specified refractive power change ΔD0, is determined in order to achieve a refractive power D KAto provide the anterior body surface of the preliminary ablation volume body, which is shaped by the predetermined refractive power change ΔD0, from a refractive power D KP the posterior surface of the ablation volume differs.

[0033] A further development of the invention provides that the compensated refractive power change is determined from the refractive power change to be set and the effective refractive power D. KT,eff of the ablation volume body according to the formula: ΔDComp=ΔDSoll2 / DKT,eff This is done. In other words, the plan is to square the change in refractive power ΔD0 to be set and divide it by the effective total body refractive power D. KT,eff to divide the ablation volume body to obtain the compensated refractive power change ΔD Comp to determine.

[0034] A further development of the invention provides that the compensated refractive power change is determined from the refractive power change to be set and the effective refractive power D. KT,eff of the preliminary removal volume body according to the formula: ΔDComp=2∗ΔD0−DKT,eff This is done. In other words, it is planned to double the refractive power change ΔD0 to be set and the effective total body refractive power D. KT,eff to subtract the volume of the ablation body from this in order to calculate the compensated change in refractive power ΔD Comp to determine.

[0035] A further development of the invention provides that the determination of the effective refractive power D KT,eff The removal of the volume body comprises the following steps.

[0036] One of the steps involves determining an effective refractive power D. KA,eff the anterior body surface of the preliminary ablation volume body for the corneal interior from the refractive power DKA of the anterior body surface of the preliminary ablation volume body. In other words, the refractive power D is used to determine the refractive power. KA the effective refractive power D of the anterior body surface of the preliminary ablation volume body KA,eff The refractive power of the anterior surface of the preliminary ablation volume is calculated, which describes the refractive power in a medium of the corneal interior. The medium of the corneal interior can be described by a refractive index of the corneal tissue. DKA,eff=nCorneafKA,eff

[0037] The effective focal length f KA,eff The anterior surface area of ​​the preliminary ablation volume is determined by the focal length f. KA the anterior body surface of the preliminary ablation volume body: fKA,eff=fKA=nCorneaDKA

[0038] In one step, an effective refractive power D is determined. KP,effthe posterior surface of the preliminary ablation volume body for the intraocular space from the refractive power D KP of the posterior surface of the preliminary ablation volume body for the ocular interior. In other words, the effective refractive power D is determined. KP,eff the posterior surface area of ​​the preliminary ablation volume. This is calculated according to the formula given below. DKP,eff=nWasserfKP,eff

[0039] The effective focal length of the posterior surface of the preliminary ablation volume body is determined by the following formula. fKP,eff=fKP=nWaterDKP

[0040] In a subsequent step, the effective total refractive power D is determined. KT,eff of the preliminary ablation volume body from a difference in the effective refractive power D KA,effthe anterior body surface of the preliminary ablation volume body to the effective refractive power D KP,eff the posterior surface area of ​​the preliminary ablation volume body was determined.

[0041] A further development of the invention provides that the determination of the effective total body refractive power D KT,eff The preliminary removal volume comprises the following steps.

[0042] One of the steps involves determining the total refractive power D of the body. KT of the preliminary ablation volume body. The total body refractive force D KT The preliminary ablation volume can be determined from the refractive force D. KA the anterior body surface of the preliminary ablation volume body, the refractive power D KL the thickness of the preliminary ablation volume body and the refractive force D KP the posterior surface of the preliminary ablation volume body: DKT=DKA+DKL+DKP

[0043] From the refractive power D KT The effective total body refractive force D is determined by the thickness of the preliminary ablation volume and the thickness of the preliminary ablation volume. KT,eff of the preliminary ablation volume body for the corneal interior determined

[0044] In other words, the total refractive power D is derived from the total body refractive power D. KT of the preliminary ablation volume body the effective total body refractive power D KT,eff of the preliminary ablation volume body, which describes the refractive power in a medium of the corneal interior. DKT,eff=nCorneafKT,eff

[0045] The effective focal length of the preliminary ablation volume body is determined by the following formula, which takes into account the central width of the preliminary ablation volume body d. fKT,eff=fKT+d fKT=nCorneaDKT

[0046] A further development of the invention provides that the method includes carrying out at least one iteration step, which comprises the following steps.

[0047] One step involves re-determining the compensated refractive power change ΔD. Comp from the refractive power change to be set ΔD0 and the effective total body refractive power D KT,eff of the preliminary ablation volume body. In other words, the compensated refractive power change ΔD Comp The iteration step is recalculated. The compensated refractive power change ΔD is then determined. Comp from the refractive power change ΔD to be set Soll and the effective total refractive power D KT,eff of the preliminary ablation volume body, which for the newly determined posterior body radius of curvature D KP,0 the posterior surface area of ​​the preliminary ablation volume body is determined.

[0048] A further step involves re-determining the final posterior body curvature radius D. KP,0 the posterior surface area of ​​the preliminary ablation volume body as a function of the body's radius of curvature R A0 the anterior body surface of the preliminary ablation volume body and the compensated refractive power change ΔD Comp , in order to effect the specified change in refractive power ΔD0. In other words, the posterior radius of curvature D of the body is changed. KP,0 the posterior surface area of ​​the preliminary ablation volume body is determined again, whereby the determination is based on the body's radius of curvature R. KA the anterior body surface of the preliminary ablation volume body and the newly determined, compensated refractive power change ΔD Comp This has been done.

[0049] The further training offers the advantage that the posterior body curvature radius D KP,0the posterior body surface of the preliminary ablation volume body can be iteratively improved to reduce a deviation in the effective total body refractive power D KT,eff to reduce the preliminary ablation volume body from the specified refractive force change ΔD0.

[0050] A further development of the invention provides that the compensated refractive power change AD is re-determined Comp from the refractive power change to be set ΔD0 and the effective total body refractive power D KT,eff of the preliminary ablation volume body (44) and the preceding compensated refractive power change ΔD Comp according to the formula: ΔDComp=ΔD0ΔDComp / DKT,eff followed.

[0051] A further development of the invention provides that the compensated refractive power change ΔD is re-determined. Comp from the refractive power change to be set ΔD0 and the effective total body refractive power D KT,effof the preliminary ablation volume body (44) and the preceding compensated refractive power change ΔD Comp according to the formula: ΔDComp=ΔDComp∗ΔD0−DKT,eff This has been done.

[0052] A further development of the invention provides that the method includes repeating the iteration step until a predetermined termination criterion is met. In other words, the posterior body radius of curvature R is determined. KP,0 The posterior surface area of ​​the preliminary ablation volume is determined iteratively in a process that includes the iteration step, repeatedly until the predefined termination criterion is met. The termination criterion could, for example, be a difference between the posterior body curvature radius D and the surface area of ​​the preliminary ablation volume. KP,0 one of the preceding iteration steps and the posterior body radius of curvature D KP,0 one of the following iteration steps.

[0053] A further development of the invention provides that the specified termination criterion is a difference between the effective total body refractive force D that falls below a certain threshold. KT,eff of the preliminary ablation volume and the specified refractive force change ΔD0. In other words, the specified termination criterion is met when the difference between the total body refractive force D KT,eff of the preliminary ablation volume body and the specified refractive force change ΔD0 is smaller than a specified difference value.

[0054] A second aspect of the invention relates to a method for controlling a treatment device. This method comprises the steps of at least one embodiment of a method as previously described. Furthermore, the method for controlling the treatment device includes the step of transmitting the provided control data to at least one ophthalmic laser of the treatment device.

[0055] The respective procedure may include at least one additional step that is executed precisely when a use case or application situation occurs that is not explicitly described here. This step may, for example, include the output of an error message and / or a prompt for user feedback. Additionally or alternatively, it may be provided that a default setting and / or a predetermined initial state is set.

[0056] A third aspect of the invention relates to a control device configured to perform the steps of at least one embodiment of one or both of the methods described above. For this purpose, the control device may include a computing unit for electronic data processing, such as a processor. The computing unit may comprise at least one microcontroller and / or at least one microprocessor. The computing unit may be implemented as an integrated circuit and / or microchip. Furthermore, the control device may include an (electronic) data storage device or a storage unit. Program code, which encodes the steps of the respective embodiment of the respective method, may be stored on the data storage device. The program code may include the control data for the respective laser.The program code can be executed by the processing unit, which then causes the control unit to execute the respective configuration. The control unit can be designed as a control chip or control device. The control unit can, for example, be part of a computer or computer network.

[0057] A fourth aspect of the invention relates to a treatment device comprising at least one ophthalmic or surgical laser and a control unit configured to perform the steps of at least one embodiment of one or both of the methods described above. The respective laser may be configured to at least partially separate a predefined corneal volume with predefined interfaces of a human or animal eye by means of optical breakthrough, in particular to at least partially separate it by means of photodisruption, and / or to ablate corneal layers by means of (photo)ablation, and / or to cause a laser-induced change in the refractive index of the cornea and / or the lens of the eye.

[0058] A fifth aspect of the invention relates to a computer program. The computer program comprises instructions that, for example, constitute program code. The program code can include at least one control data set with the respective control data for the respective laser. When the program code is executed by a computer or a computer network, it is caused to execute the method described above, or at least one embodiment thereof.

[0059] A sixth aspect of the invention relates to a computer-readable medium (storage medium) on which the aforementioned computer program or its instructions are stored. To execute the computer program, a computer or a computer network can access the computer-readable medium and read its contents. The storage medium is, for example, configured as a data storage device, in particular at least partially as a volatile or non-volatile data storage device. A non-volatile data storage device can be flash memory and / or an SSD (solid-state drive) and / or a hard drive. A volatile data storage device can be RAM (random access memory). The instructions can be, for example, in the form of source code of a programming language and / or as assembly language and / or as binary code.

[0060] Further features and advantages of one of the described aspects of the invention may arise from further developments of another aspect of the invention. The features of the embodiments of the invention can therefore exist in any combination with one another, unless they have been explicitly described as mutually exclusive.

[0061] Additional features and advantages of the invention are described below with reference to the figures in the form of advantageous embodiments. The features or combinations of features of the embodiments described below can be present in any combination with one another and / or with the features of the embodiments. That is, the features of the embodiments can complement and / or replace the features of the embodiments, and vice versa. Thus, embodiments that are not explicitly shown or explained in the figures, but which can be derived and generated from separate combinations of features in the embodiments and / or embodiments, are also to be considered as encompassed and disclosed by the invention.Thus, embodiments that do not exhibit all the features of an originally formulated claim, or that go beyond or deviate from the combinations of features set forth in the cross-references of the claims, are also to be considered disclosed. For exemplary embodiments, see: Fig. 1 a schematic representation of a treatment device with an ophthalmic surgical laser for the treatment of the cornea of ​​an eye by means of photodisruption and / or, for example, ablation; Fig. 2. A schematic representation of a preoperative cornea and a postoperative cornea; and Fig. 3 A schematic representation of a method for controlling a treatment device.

[0062] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0063] Fig.Figure 1 shows a schematic representation of a treatment device 10 with an ophthalmic surgical laser 12 for treating the cornea of ​​an eye 16 by photodisruption and / or, for example, ablation. For corneal treatment, treatment positions within the treatment area 14 are specified in the control data, where, for example, tissue to be cauterized or ablated is present. In addition to the laser 12, a control unit 18 for the laser 12 can be provided, enabling it to emit pulsed laser pulses, for example, in a predefined pattern. Alternatively, the control unit 18 can be an external control unit 18 with respect to the treatment device 10.

[0064] Furthermore, the Fig.1. The laser beam 20 generated by the laser 12 is deflected towards the eye 16 by means of a beam deflection device 22, such as a rotary scanner. The beam deflection device 22 is also controlled by the control unit 18 to treat the eye 16.

[0065] The laser 12 shown is preferably a photodisruptive and / or ablative laser configured to emit laser pulses in a wavelength range between 300 nm and 1400 nm, preferably between 700 nm and 1200 nm, with a 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. The control unit 18 also includes a storage device for 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 area 14 to be treated. The storage device can be part of the control unit 18, or the storage device can be provided as external storage, in particular in the form of a computer network (cloud).The position data and / or focusing data of the individual laser pulses, especially for laser treatment, can be generated based on predetermined measurements, for example from a previously measured topography and / or pachymetry and / or the morphology of the cornea or the optical refractive error correction to be produced.

[0066] Fig. Figure 2 shows a schematic representation of an ablation volume in a cornea.

[0067] Fig.Figure 2 shows a schematic representation of a preoperative cornea 30 to be treated. The preoperative cornea 30 may have an anterior corneal surface 32, which may define its boundary with the extraocular space 34. The anterior corneal surface 32 of the preoperative cornea 30 may exhibit an anterior corneal curvature, which may be described by an anterior corneal curvature radius. On the side of the preoperative cornea 30 opposite the anterior corneal surface 32, the cornea 32 may have a posterior corneal surface 36, which may define its boundary with the extraocular space 38. The posterior corneal surface 36 of the preoperative cornea 30 may exhibit a posterior corneal curvature, which may be described by a posterior corneal curvature radius.The anterior corneal surface 32 and the posterior corneal surface 36 can have a distance between them which can describe a thickness d of a corneal volume 40 of the preoperative cornea 30. The preoperative cornea 30 can be optically described as a thick lens. Incident light rays 42 can be refracted by the preoperative cornea 30. A total refractive power D. CT the preoperative cornea 30 can consist of a refractive power D CA the anterior corneal surface 32 of the preoperative cornea 30, a thickness-dependent refractive power D CL of the preoperative cornea 30 and a refractive power D CP to the posterior surface of the preoperative cornea 30. DCT = DCA + DCL + DCP

[0068] The refractive power D CA the anterior corneal surface 32 of the preoperative cornea 30 can increase the refractive power D CAdescribe which form the boundary between the outer eye space 34 of the refractive index of the air n Air and the corneal volume 40 of the refractive index of the cornea n Cornea exhibits an effective anterior corneal surface 32. DCA=NCornea−nAirRCA

[0069] The thickness-dependent refractive power D CL can the refractive power D CL describe which is caused by guiding the light rays 42 within the corneal volume 40 over the thickness d. DCL=dRCARCP(nCornea−nAir)(nCornea−nAqua)nCornea

[0070] The refractive power D CP the posterior corneal surface 36 of the preoperative cornea 30 can increase the refractive power D CP describe which form the interface between the corneal volume 40 of the refractive index of the cornea n Cornea and the interior of the eye 38 of the refractive index of water n Aqua exhibits an effective posterior corneal surface 36. DCP=nAqua−nCorneaRCP

[0071] The refractive power D CA the anterior corneal surface 32 can account for a major part of the total refractive power D CT of the preoperative cornea 30.

[0072] To treat refractive errors, it may be necessary to adjust the total refractive power D. CT the cornea 30 by a predetermined change in refractive power ΔD Soll to change. To change the total refractive power D CT The cornea may be designed to distinguish the corneal radius of curvature of the anterior corneal surface 32 of the cornea 30 from the anterior corneal radius of curvature of the anterior radius R. CA to alter by removing tissue from the cornea 30.

[0073] According to the state of the art, it is common to determine the achievement of the specified change in refractive power ΔD. Soll by a change in refractive power D CAto effect the anterior corneal surface 32 of the cornea 30. It is intended that the anterior radius R be affected. CA to determine at which the anterior corneal surface 32 of the cornea 30 provides a refractive power D CA exhibits the change in the anterior radius R. CA The anterior corneal surface 32 of the cornea 30 can be treated by removing tissue from the anterior corneal surface 32 of the cornea 30.

[0074] In this process, a preliminary ablation volume 44, to be determined, is removed from the cornea 30. This changes the thickness d of the cornea by a thickness change value Δd from an actual thickness d0 of the preoperative cornea 30 to a target thickness d1 of a postoperative cornea 30.

[0075] However, due to the change in the thickness d of the cornea 30, the refractive power D can also change. CL The corneal volume changes by 40. This is due to the change in refractive power D. CLof the corneal volume 40, therefore, in addition to the change in refractive power D, a change in the refractive power D occurs. CA change in refractive power acting on the anterior corneal surface 32 D CL of the cornea 30. This additional change in refractive power can lead to a deviation from the set refractive power change ΔD. Soll of the cornea 30. According to the current state of the art, only simple modifications to the described procedure are made to compensate for the described deviation. However, these compensations are relatively inaccurate and / or complex. One objective of this disclosure is to provide a method for determining the anterior radius R to be provided. CA to provide the anterior corneal surface 32. The described procedure follows an iterative approach.

[0076] The approach is to describe the changes in the refractive power of the cornea 30 caused by tissue removal using the preliminary ablation volume 44. In other words, the aim is to determine the preliminary ablation volume 44 whose refractive power corresponds to the desired change in refractive power.

[0077] Since the tissue is to be removed from the anterior corneal surface 32 of the preoperative cornea 30, the preliminary ablation volume body 44 has an anterior body surface 46 which has the same radius of curvature as the anterior corneal surface 32 of the preoperative cornea.

[0078] The preliminary ablation volume 44 has a posterior surface area 48 that corresponds to the anterior corneal surface 32 of the postoperative cornea 30. The posterior surface area 48 of the preliminary ablation volume 44 has a curvature that corresponds to the corneal radius of curvature of the anterior corneal surface 32 of the postoperative cornea 30.

[0079] The first step of the procedure involves determining the posterior radius of curvature R. KP the posterior corneal surface 32. The posterior radius of curvature R KP is determined from the specified change in refractive power: RKP=(nCornea−nAir)(nCornea−nAir)RKA+ΔDset

[0080] What is relevant is an effective refractive power D. eff of the preliminary ablation volume body 44. The effective refractive force D eff The preliminary ablation volume body 44 can, for example, be subjected to an effective refractive force D.A,eff the anterior corneal surface 32 of the preliminary ablation volume body 44 and an effective refractive power D CP,eff the posterior corneal surface 32 of the preliminary ablation volume 44 can be approximated, or by the refractive power change ΔD KT,eff the effective refractive power D KT,eff a total system of the preliminary removal volume body 44 will be determined.

[0081] A subsequent step can involve a re-determination of the posterior body radius of curvature R. KP to provide for a deviation in the effective total body refractive force D KT,eff of the preliminary ablation volume body 44 from the specified refractive force change ΔD Soll to reduce.

[0082] The posterior radius of curvature R KP can be determined as in the previous step. However, to reduce the deviation, it may be possible to use the posterior radius of curvature R. KPfor a compensated change in refractive power ΔD Comp to determine which are responsible for the posterior radius of curvature R KP The identified deviation was taken into account. RKP=(nCornea−nAir)(nCornea−nAir)RKP+ΔDComp

[0083] The procedure may therefore provide for the use of a different refractive index ΔD instead of the required refractive index. Soll the compensated refractive index ΔD Comp to use which results from the given change in refractive power ΔD Soll and the determined effective total refractive power D KT,eff of the preliminary removal volume body 44. ΔDComp=ΔDSoll2 / DKT,eff

[0084] Is the effective total refractive power D KT,eff of the preliminary ablation volume body by which the effective refractive force D KA,eff the anterior surface of the preliminary ablation volume body 44 and the effective refractive power D KP,effapproximating the posterior body surface 48 of the preliminary ablation volume body 44, the following applies: Deff=DKA,eff−DKP,eff

[0085] The effective refractive power D KA„eff the anterior body surface 46 of the preliminary ablation volume body 44 results from: DKA,eff=nWasserfKA,eff

[0086] The effective focal length f KA,eff the anterior body surface 46 of the preliminary ablation volume body 44 results from the focal length f KA of the anterior body surface 46 of the preliminary ablation volume body 44: fKA,eff=fKA=nWaterDKA

[0087] The effective focal length f Kp,eff the posterior body surface 48 of the preliminary ablation volume 44 results from the width d of the preliminary ablation volume 44: fKP,eff=fKP+d where fKP=nWaterDKP

[0088] Will the effective refractive power D KT,eff of the preliminary ablation volume body 44 by which the refractive force D KT , approximating the preliminary removal volume body 44, the following applies: Deff=DKT,eff

[0089] The effective total refractive power D KT,eff The preliminary removal volume body 44 results from: DKT,eff=nWasserfKT,eff

[0090] The effective focal length f KT,eff The size of the preliminary ablation volume is determined by the focal length f. KT of the preliminary removal volume body 44 : fKT,eff=fKT=nWaterDKT

[0091] The compensated refractive index ΔD Comp re-determined posterior body radius of curvature R KP results in an effective total refractive power D KT,effof the preliminary ablation volume body 44, which exhibits a smaller deviation from the refractive index ΔD to be provided Soll exhibits, as the refractive index ΔD to be provided Soll determined posterior body radius of curvature R KP

[0092] Possible values ​​that result from a procedure based on determining the effective refractive power D KA,eff the anterior body surface 46 and the effective refractive power D KP,eff The values ​​for the posterior body surface area 48 are shown in Table 1. Possible values ​​resulting from a method based on the determination of the effective refractive power ΔD eff from the refractive power ΔD T,\eff The results of the preliminary removal volume can be found in Table 2. Table 1 Unit Ablation volume body (initial) Ablation volume body (final) n Luft 1,0001 1,0001 n Cornea 1,3763 1,3763 n Wasser 1,3371 1,3371 R KA m 7,81E-03 7,81E-03 R KP m 8,68E-03 8,65E-03 d m 9,54E-05 9,27E-05 D m -1 -4,820 -4,681 D KA m -1 48,153 48,153 D KP m -1 -43,333 -43,472 D KL m -1 0,145 0,141 D KT m -1 -4,965 -4,822 f Cornea m -0,2772 -0,2854 f K,eff m -0,2773 -0,2855 D KT,eff m -1 -4,963 -4,821

[0093] Fig. Figure 3 shows a schematic representation of a method for controlling a treatment device.

[0094] The procedure for controlling the treatment device 10 may include the following steps to be carried out by a control unit 18.

[0095] The procedure can include process steps S1 to S10 for providing control data for a laser 12 of the treatment device 10.

[0096] A first step S1 can be the receipt of a predetermined change in refractive power ΔD. Soll , concerning a change in total corneal breakaway force D CT a preoperative cornea to a total corneal fracture force D CT a postoperative cornea comprise 30.

[0097] A second step S2 can involve determining a preoperative cornea 30 to provide the specified refractive power change ΔD. Soll, comprising a preliminary ablation volume body 44 to be ablated. The preliminary ablation volume body 44 may comprise an anterior body surface 46 with a preliminary anterior body curvature, wherein the anterior body curvature radius R KA the curvature R A the anterior corneal surface 32 of the preoperative cornea may exhibit.

[0098] The preliminary ablation volume body 44 can have a posterior body surface 48 with a posterior body radius of curvature R KP exhibit.

[0099] The posterior radius of curvature R KP depending on the preliminary anterior body curvature radius R KA the anterior body surface 46 of the preliminary ablation volume body and the predetermined refractive power change ΔD Soll , can be determined. The posterior radius of curvature R KP can be determined by the control device 18 in such a way that a refractive force DKP the posterior body surface 48 of the preliminary ablation volume body 44 is provided, which is distributed around the specified refractive power change ΔD Soll , of a refractive power D KA the anterior body surface 46 of the preliminary ablation volume body 44 differs.

[0100] A third step, S3, can be used to determine an effective total body refractive power D. KT,eff of the preliminary removal volume body 44.

[0101] A fourth step, S4, can be used to determine a compensated refractive power change ΔD. Comp from the refractive power change ΔD to be set Soll and the effective total refractive power D KT,eff of the preliminary removal volume body 44.

[0102] A fifth step, S5, can determine a final posterior body radius of curvature D. KP,Sollthe posterior body surface 48 of the preliminary ablation volume body 44 as a function of the posterior body radius of curvature R KP and the compensated refractive power change ΔD Comp , encompass in order to achieve the specified change in refractive power ΔD Soll to effect.

[0103] A sixth step S6 may include generating the control data to control the laser 12 to ablate the preliminary ablation volume 44 of the tissue of the preoperative cornea 30.

[0104] A seventh step S7 can include transferring the provided control data to a respective ophthalmic surgical laser 12 of the treatment device 10.

[0105] Overall, the examples show how a method for determining a target radius of curvature can be provided. Reference sign 10 Treatment device 12 lasers 14 area 16 Eye 18 Control unit 20 laser beam 22 Beam deflection device 30 Cornea 32 anterior corneal surface 34 Outer eye space 36 posterior corneal surface 38 Eye interior 40 corneal volume 42 Light beam 44 Ablation volume bodies 46 anterior body surface 48 posterior body surface D CT Refractive power of the cornea ΔD0 predetermined change in refractive power of the cornea R CP Radius of the posterior corneal surface R CA radius of the anterior corneal surface R KP Radius of the posterior body surface R KA radius of the anterior body surface D KA Refractive power of the anterior body surface D KP Refractive power of the posterior body surface D CARefractive power of the anterior corneal surface D CP Refractive power of the posterior corneal surface D CL Refractive power of the cornea volume D KT Total refractive power D KT,eff effective total body refractive power d central thickness of the cornea ΔD comp compensated refractive power change D CA Refractive power of the anterior corneal surface D KA,eff effective refractive power of the anterior body surface D KP,eff effective refractive power of the posterior body surface f KA,eff effective focal length of the anterior body surface f KT,eff effective focal length of the ablation volume n Wasser Refractive index of water n Cornea Refractive index of the cornea n Luft Refractive index of air f KA Focal length of the anterior body surface f KT Focal length of the ablation volume D T0,eff Effective actual refractive power of the cornea D T0 Actual refractive power of the cornea

Images