Method for providing control data for ophthalmic laser of treatment device

Abstract

The invention relates to a method for providing control data for an ophthalmic laser (12) of a treatment device (10). By means of the control device (18), it is achieved that: corneal parameters of an anterior surface (24) of the cornea (16) are determined (S10) as a function of predetermined examination data; determining (S12) an epithelium map of an epithelium layer (26) of the cornea (16) on the basis of the predetermined examination data, wherein a thickness of the epithelium layer (26) is provided in the epithelium map; calculating (S14) a stromal wavefront map from the determined corneal parameters of the anterior surface (24) of the cornea and the determined epithelium map; determining (S16) correction data for correcting the visual impairment based on the matrix wavefront map; and providing (S18) control data comprising correction data determined based on the matrix wavefront map.

Description

Technical Field

[0001] The invention relates to a method for providing control data for an ophthalmic laser of a treatment device. Furthermore, the invention relates to a control device formed to carry out the method, a treatment device having such a control device, a computer program comprising commands for causing the treatment device to carry out the method, and a computer-readable medium on which the computer program is stored. Background Art

[0002] Therapeutic devices and methods for controlling ophthalmic lasers to correct optical visual disorders or pathological and / or unnaturally altered areas of the cornea are known in the prior art, wherein the pulsed laser and the beam focusing device can, for example, be formed such that the laser pulses achieve photodisruption and / or ablation in a focus located within the organic tissue to remove tissue, in particular tissue lenticules, from the cornea.

[0003] One treatment method for correcting visual impairment is transepithelial photorefractive keratectomy (Trans-PRK), in which superficial corneal layers are removed, in particular the epithelium, but the epithelium can regenerate. Therefore, only tissue removal in the corneal stroma is continuous. Therefore, the additional removal of the epithelium should be taken into account in treatment planning, in which only standardized epithelial layers with constant thickness have been planned so far, and in particular the individual epithelial shape of the patient, who may have an irregular epithelial shape, has not been taken into account so far. SUMMARY OF THE INVENTION

[0005] The object of the present invention is to provide control data for treatment with an ophthalmic laser, by means of which better corneal correction results can be achieved.

[0006] This object is solved by the independent claims. Advantageous embodiments of the invention are disclosed in the dependent claims, the description and the drawings.

[0007] The invention is based on the idea that by subtracting the epithelial part, the stromal component of the visual impairment can be determined independently of the corneal surface. Thus, treatment planning can be directed directly to the non-regenerating stroma and therefore only to the areas that remain corrected after treatment.

[0008] One 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 performed by a control device. The control device is understood to be an apparatus or an apparatus component, in particular a computer or a processor, which can automatically or semi-automatically perform the following steps.

[0009] In this method, the following are achieved: determining corneal parameters of the anterior surface of the cornea according to predetermined inspection data; determining an epithelial map of the corneal epithelial layer according to predetermined inspection data, wherein the thickness of the epithelial layer is provided in the epithelial map; calculating a stromal wavefront map according to the determined corneal parameters of the anterior surface of the cornea and the corneal parameters of the determined epithelial map; determining correction data for correcting visual impairment based on the stromal wavefront map and providing control data, wherein the control data includes the correction data determined based on the stromal wavefront map.

[0010] In other words, inspection data of the eye, in particular inspection data of the cornea of ​​the eye, can be predetermined, from which corneal parameters of the front surface can be determined. For example, topographic measurements and / or wavefront measurements can be performed, and the corneal parameters can, for example, include an anterior corneal wavefront map and / or an anterior corneal surface map. The wavefront error of the eye or cornea is represented by a wavefront or a wavefront map, which represents the relationship between the wavefront deformation and the position. The anterior corneal surface map can, for example, include height data or contour data of the anterior corneal surface. For example, the anterior corneal surface map can be determined by topographic measurements. In addition, an epithelial map of the epithelial layer can be determined based on the inspection data, wherein the epithelial map can indicate the thickness of the epithelial layer, which depends on the position in the cornea.

[0011] With the aid of the corneal parameters and the epithelial map, a stromal wavefront map can be determined, which provides a wavefront deformation of the stroma. In particular, the effect of the epithelial layer that can be determined from the epithelial map can be subtracted from the corneal parameters that provide the overall corneal characteristics to obtain a stromal wavefront map from the difference.

[0012] The correction can then be planned by means of the stromal wavefront map, which correction can be provided as correction data. This means that it is possible to determine which changes must be made to the stroma, for example to correct visual impairment. These corrections can then be provided in the form of control data, which can be used to control the treatment device and / or the laser. The control data may include a corresponding data set for positioning and / or focusing each laser pulse in the cornea. In addition or alternatively, the control data may include a corresponding data set for adjusting at least one beam device, for beam guiding and / or beam shaping and / or beam deflection and / or beam focusing of the laser beams of each laser.

[0013] The invention has the advantage that changes can be planned only for the permanently remaining corneal tissue, in particular the stroma, since the epithelium will re-grow and thus changes in the epithelium will not remain permanently. Furthermore, the influence of an irregular epithelium can thus be taken into account since it is not necessary to assume a simplified or average model for the epithelium. Thus, the correction of visual impairments can be improved overall, in particular for Trans-PRK.

[0014] The invention also includes embodiments that produce additional advantages.

[0015] In one embodiment, the epithelial map indicates the thickness of the epithelial layer in the z direction for each x / y position. In other words, therefore, one obtains a map in Cartesian coordinates, in which the corresponding thickness values ​​or height values ​​of the epithelial layer at each x / y position of the cornea (in particular each x / y position) are indicated on the z axis or in the direction of the corneal optical axis and are parallel to each other. Wherein, the x / y plane is the plane in the top view of the eye / cornea. In particular, it is also possible to indicate r / phi positions instead of x / y positions for the map, so that the map can be provided in cylindrical coordinates.

[0016] In other embodiments, corneal parameters provide anterior corneal surface map, which includes height data of the anterior corneal surface, wherein the anterior stroma surface map is determined by subtracting the epithelial map from the anterior corneal surface map, and the stroma wavefront map is determined from the anterior stroma surface map. In other words, corneal parameters can at least include anterior corneal surface map, wherein there is a height profile or height data of the anterior corneal surface. Alternatively or additionally, a corneal wavefront map of the anterior corneal surface can also be provided as a corneal parameter, from which the height data of the anterior corneal surface can be determined. By the anterior corneal surface map, a difference with the epithelial map can then be formed, thereby obtaining a stroma surface map. In other words, the profile of the epithelial layer can be subtracted from the height profile of the corneal surface to obtain the profile of the stroma. The stroma profile in the form of anterior stroma surface map can then be converted into a stroma wavefront map, specifically using the following formula:

[0017] stromaWF(x,y)=(stromaTH(x,y)–avg(Stroma))*(n_Stroma–1), where stromaWF(x,y) represents the stroma wavefront map, stromaTH(x,y) represents the anterior stroma surface map, avg(Stroma) represents the average height value (average value) of the stroma, and n_Stroma represents the refractive index of the stroma. In other words, the topology of the stroma can be determined from the topology of the corneal surface and the topology of the epithelium, where the wavefront used for treatment planning can be determined by the topology of the stroma.

[0018] In another embodiment, the corneal parameters provide an anterior corneal wavefront map, wherein the epithelial wavefront map is calculated from the epithelial map to calculate the stromal wavefront map, wherein the stromal wavefront map is determined by subtracting the epithelial wavefront map from the anterior corneal wavefront map. In other words, the corneal wavefront measurements providing the anterior corneal wavefront map can be calculated by subtracting the epithelial wavefront map. Here, the epithelial wavefront map can be obtained by calculating from the epithelial map, thereby converting the topology into the wavefront, in particular using the following formula:

[0019] epiWF(x,y)=(epiTh(x,y)–avg(epi))*(n_epi–1), where epiWF(x,y) represents the epithelial wavefront map, epiTH(x,y) represents the epithelial map, avg(epi) represents the average thickness value (average value) of the epithelial layer, and n_epi represents the refractive index of the epithelium. In other words, the wavefront of the stroma can be determined by the wavefront of the corneal surface and the wavefront of the epithelial layer, wherein the wavefront of the epithelial layer can be determined by the topology of the epithelial layer. By this embodiment, compared with the aforementioned variant of calculating the stroma wavefront map based on the topological structure, it has the advantage that the error propagation is lower, thereby improving the determination.

[0020] In another embodiment, appropriate tissue removal is planned on the matrix for the correction data, thereby compensating for the changes in the epithelial layer after epithelial recovery. In other words, the epithelial layer can grow again after treatment, wherein it will not present the original shape due to treatment, but for example has irregularities, which can produce visual impairment, especially high-order aberrations. This means that the epithelial layer is no longer completely restored as before treatment, but has differences, wherein these differences can be estimated and compensated. This changed epithelial layer can also be considered in the treatment plan on the matrix, because the changes in the epithelial layer are planned by removing the adapted tissue in the matrix. This means that additional tissue can be removed from the matrix, which can compensate for the influence of the changed epithelial layer. In order to estimate the changes in the epithelial layer after epithelial recovery, for example, it can be assumed that the preoperative epithelial layer is equal to the epithelial layer after postoperative epithelial recovery, but has different curvatures due to the removal of tissue on the matrix. Another alternative is to assume the average epithelial layer shape of the postoperative epithelial layer from the statistical data of a predetermined population, thereby providing the changes in the epithelial layer after treatment. For example, the average epithelial layer and the average value of the preoperative epithelial layer can also be formed to simulate the postoperative epithelial layer. By means of these embodiments, an advantage is that additional damaging effects can be corrected in an improved manner.

[0021] In other embodiments, different laser interactions with epithelial and stromal tissues are considered in the control data. In other words, epithelial tissue and stromal tissue may have different responses to the laser pulses of radiation. For example, different energy densities may be required to separate each tissue, wherein they can be taken into account in the control data. Therefore, the laser pulse energy and / or the number of laser pulses per surface or volume unit depending on the tissue can be adjusted, for example. Thus, the advantage is that the treatment of the cornea can be improved.

[0022] Another possibility is that the epithelial map is determined by optical coherence tomography and / or ultrasound, in particular ultra-high frequency ultrasound (UHF ultrasound). In other words, the thickness of the epithelial layer can be directly measured to provide the epithelial map. In this case, optical coherence tomography and / or corneal ultrasound are particularly suitable.

[0023] Another aspect relates to a method for controlling a therapeutic device. The method comprises the method steps of at least one embodiment of the method as described above. In addition, the method for controlling a therapeutic device comprises the steps of transmitting the provided control data to at least one ophthalmic laser of the therapeutic device and controlling the therapeutic device and / or the laser using the control data.

[0024] The corresponding method may include at least one additional step, which is performed if and only if an application case or application situation occurs, which application case or application situation is not explicitly described here. For example, this step may include outputting an error message and / or outputting a request for input user feedback. Additionally or alternatively, it may be provided that a default setting and / or a predetermined initial state are adjusted.

[0025] Another aspect of the present invention relates to a control device, which is formed to perform the steps of at least one embodiment of one or both of the aforementioned methods. In addition, the control device may include a computing unit, such as a processor, for electronic data processing. The computing unit may include at least one microcontroller and / or at least one microprocessor. The computing unit may be configured as an integrated circuit and / or a microchip. In addition, the control device may include an (electronic) data memory or a storage unit. A program code may be stored on a data memory, by which the steps of the corresponding embodiments of the corresponding method are encoded. The program code may include control data for the corresponding laser. The program code may be executed by a computing unit, thereby causing the control device to perform the corresponding embodiment. The control device may be formed as a control chip or a control unit. The control device may, for example, be included in a computer or a computer cluster.

[0026] Another aspect of the invention relates to a treatment device having at least one eye surgery or ophthalmic laser and a control device, which is formed to perform the steps of at least one embodiment of one or both of the above-mentioned methods. The corresponding laser can be formed to at least partially separate a predetermined corneal volume of a human or animal eye with a predetermined interface by optical decomposition, in particular by photodisruption and / or by ablating corneal layers by means of (photo)ablation and / or achieving a laser-induced refractive index change in the cornea and / or the eye lens and / or increasing cross-linking of the cornea.

[0027] In another embodiment of the treatment device according to the invention, the laser can be suitable for emitting laser pulses with a wavelength range between 300nm and 1400nm, for example between 900nm and 1200nm, and a repetition frequency greater than 10 kilohertz (kHz), for example between 100kHz and 100 megahertz (MHz), with a corresponding pulse duration between 1fs and 1ns, for example between 10fs and 10ps. The use of such a laser in the method according to the invention also has the advantage that the irradiation of the cornea does not have to be carried out in a wavelength range below 300nm. This range is included in the term "deep ultraviolet" in laser technology. As a result, accidental damage to the cornea caused by these extremely short wavelength and high-energy beams is advantageously avoided. Photodisruptive and / or ablative lasers of the type used here usually input pulsed laser radiation with a pulse duration between 1fs and 1ns into the corneal tissue. As a result, the power density of the corresponding laser pulses required for optical breakdown can be narrowly limited spatially, so that high cutting accuracy can be achieved in the generation of the interface. In particular, the range between 700 nm and 780 nm may also be selected as the wavelength range.

[0028] In another embodiment of the therapeutic device according to the invention, the control device may include at least one storage device for at least temporarily storing at least one control data set, wherein one or more control data sets include control data for positioning and / or for focusing individual laser pulses in the cornea; and may include at least one beam device for beam guiding and / or beam shaping and / or beam deflection and / or beam focusing of the laser beam of the laser.

[0029] Another aspect of the invention relates to a computer program. The computer program includes, for example, commands forming a program code. The program code may include at least one control data set having corresponding control data for a corresponding laser. When the program code is executed by a computer or a computer cluster, the previously described method or at least one embodiment thereof is performed.

[0030] Another aspect of the present invention relates to a computer-readable medium (storage medium) on which the above-mentioned computer program and its commands are stored respectively. In order to execute the computer program, a computer or a computer cluster can access the computer-readable medium and read out its content. For example, the storage medium is formed as a data memory, in particular at least partially formed as a volatile or non-volatile data memory. The non-volatile data memory can be a flash memory and / or an SSD (solid state drive) and / or a hard disk. The volatile data memory can be a RAM (random access memory). For example, the command can exist as a source code of a programming language and / or as an assembler and / or as a binary code.

[0031] Further features and advantages of one of the aspects described herein may result from the embodiments of another aspect of the invention. Therefore, if the features of the embodiments of the invention are not explicitly described as mutually exclusive, they may exist in any combination with each other. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Below, additional features and advantages of the present invention are described in the form of advantageous implementation examples based on the accompanying drawings. The features or feature combinations of the implementation examples described below may exist in any combination in combination with each other and / or with the feature combinations of the implementation examples. This means that the features of the implementation examples may supplement and / or replace the features of the implementation examples, and vice versa. Therefore, configurations are also considered to be covered and disclosed by the present invention, which are not explicitly shown or explained in the drawings, but are produced and can be generated by separate feature combinations from the implementation examples and / or implementation examples. Therefore, configurations are also considered to be disclosed, which do not include all the features of the originally proposed claims or extend beyond or deviate from the feature combinations set forth in the relationship of the claims. For the implementation examples, it is shown:

[0033] Figure 1 is a schematic diagram of a therapeutic device according to an exemplary embodiment;

[0034] Figure 2 It is a schematic diagram of the structure of the corneal layer of the cornea;

[0035] Figure 3 is a diagram of a schematic method of providing control data according to an exemplary embodiment.

[0036] In the figures, identical or functionally identical elements are provided with the same reference symbols. DETAILED DESCRIPTION OF THE INVENTION

[0038] Figure 1 A schematic diagram of a treatment device 10 is shown, which is provided with an ophthalmic laser 12 for removing tissue 14 from a human or animal cornea 16 by photodestruction and / or ablation. For example, tissue 14 can be separated from the cornea 16 by ablating corneal layers by the ophthalmic surgical laser 12 to correct visual disorders. The corrective contour or geometry of the tissue 14 to be removed can be set by corrective data, which can be determined by the control device 18. In particular, control data can be provided, which includes the corrective data, wherein the control device 18 can control the laser 12 and / or the treatment device 10 by the control data so that pulsed laser pulses are emitted into the cornea 16 of the eye in a pattern predefined by the control data to remove the tissue 14. Alternatively, the control device 18 can be a control device 18 that is external to the treatment device 10.

[0039] also, Figure 1It is shown that a laser beam 20 generated by a laser 12 can be deflected toward a cornea 16 by a beam deflection device 22 (eg, a rotary scanner) to remove tissue 14. The beam deflection device 22 can also be controlled by a control device 18 to remove tissue 14.

[0040] Furthermore, the control device 18 optionally comprises storage means (not shown) for at least temporarily storing at least one control data set, wherein one or more control data sets comprise control data for positioning in the cornea and / or for focusing individual laser pulses.

[0041] Typically, the treatment planning for determining the correction data for the removal of tissue 14 is based on a corneal wavefront map. However, a disadvantage here is that the influence of the epithelial layer is also present in the corneal wavefront map and cannot be compensated by the treatment because the epithelial layer will grow again. In order to perform improved treatments, in particular in transmitted light refractive keratectomy, provision can be made to perform the treatment planning not on the corneal wavefront map but directly on the stromal wavefront map in order to exclude the influence of the epithelial layer in the treatment planning.

[0042] exist Figure 2 , a schematic and simplified structure of a cornea 16 is shown, wherein the layers of the cornea are shown. Anterior surface 24 forms the surface of cornea 16. Here, curvature and height may be provided, for example, in the form of anterior corneal surface map, and / or wavefront deformation on anterior surface 24 may be provided in the form of anterior corneal wavefront map.

[0043] In depth, the epithelial layer 26 follows from the corneal surface 24. The epithelial layer or epithelium comprises epithelial cells and has a thickness of about 40 to 60 μm, wherein the epithelial layer 26 can re-grow after damage and / or removal. The thickness of the epithelial layer 26 can be determined by measurement, in particular by optical coherence tomography and / or ultrasound, and can be provided, for example, in the form of an epithelial map.

[0044] The epithelial layer 26 is bounded by a Bowman's membrane 28, which separates the epithelial layer 26 from the stroma 30. The stroma 30 constitutes the majority of the corneal thickness, wherein the stroma 30 thickness is approximately 400 μm to 500 μm. In contrast to the epithelial layer 26, the stroma 30 cannot regenerate. Therefore, visual impairments can be corrected by ophthalmic lasers in the stroma 30, thereby providing a continuous change in the optical properties of the cornea 16. In particular, due to the tissue structure, the stroma 30 may have other laser interaction properties than the epithelial layer 26, so optimized or different laser parameters can be planned for the individual layers 26, 30. Finally, the stroma 30 is terminated by the Descemet's membrane 32. For the sake of clarity, Figure 2 Additional membranes and / or layers of the cornea are not shown.

[0045] To improve treatment planning, particularly in Trans-PRK treatments, the control unit 18 may perform Figure 3 The method shown in .

[0046] exist Figure 3 , a schematic diagram of a method for providing control data for an ophthalmic laser 12 of a treatment device 10 is shown, wherein the method can be executed by a control device 18 .

[0047] In step S10, corneal parameters of the anterior surface 24 of the cornea 16 may be determined based on predetermined examination data. For example, topographic measurements may be performed to provide an anterior corneal surface map, and / or wavefront measurements may be performed to provide an anterior corneal wavefront map.

[0048] In step S12, an epithelial map of the epithelial layer 26 of the cornea 16 may be determined according to predetermined examination data, wherein the epithelial map may indicate the thickness of the epithelial layer 26 in the z direction for each x / y position. Specifically, the epithelial map may be determined by optical coherence tomography and / or ultrasound.

[0049] In step S14, a stromal wavefront map may be calculated based on the corneal parameters and the epithelial map, wherein the stromal wavefront map indicates a wavefront deformation that is entirely due to the stroma 30. To calculate the stromal wavefront map, a difference in the corresponding topography may be performed on the one hand, or a difference in the wavefront may be performed on the other hand.

[0050] Among the differences in topography, corneal parameters that can be provided include an anterior surface map, which includes height data or elevation of the anterior surface 24 of the cornea 16. An epithelial map also exists as a topographic map and can be subtracted from the anterior stromal surface map to model the surface of the stroma 30, which can be provided as an anterior stromal surface map. The anterior stromal surface map can in turn be converted into a stromal wavefront map, from which correction data for correcting visual impairments, such as refractive data for spherical, cylindrical and / or astigmatism correction, can be determined in step S16.

[0051] When determining a stromal wavefront map based on the wavefront, the corneal parameters may include an anterior corneal wavefront map of the corneal surface 24. An epithelial map of the epithelial layer 26 may be converted into a wavefront, thereby providing an epithelial wavefront map. Thus, a wavefront of the stroma 30 may be provided by the difference between the epithelial wavefront map and the anterior corneal wavefront map, wherein the stromal wavefront map may then be provided to determine the correction data in step S16.

[0052] Finally, in step S18 , control data for controlling the ophthalmic laser 12 and / or the treatment device 10 can be provided, by means of which laser pulses for removing tissue 14 can be radiated into the cornea 16 according to correction data for correcting the visual disorder.

[0053] In particular, adaptive tissue removal for removing tissue 14 in the stroma 30 can also be taken into account in the correction data, by which the effects caused by the altered epithelial restoration are compensated. Thus, the curvature of the epithelial layer before and after treatment is different, for example, due to tissue removal, wherein the altered curvature can be estimated in advance. Thus, effects such as aberrations caused by the altered curvature of the epithelial layer 26 can be planned in advance and taken into account by adaptive tissue removal.

[0054] Overall, these embodiments demonstrate how the shape of the substrate 30 can be virtually determined and used for treatment planning.

Claims

1. 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 device (18): - determining (S10) corneal parameters of the front surface (24) of the cornea (16) based on predetermined examination data; - determining (S12) an epithelial map of the epithelial layer (26) of the cornea (16) based on predetermined examination data, wherein the thickness of the epithelial layer (26) is provided in the epithelial map; - calculating (S14) a stromal wavefront map based on the determined corneal parameters of the anterior surface (24) of the cornea and the determined epithelial map; - determining (S16) correction data for correcting visual impairment based on the stromal wavefront map; - providing (S18) control data, said control data comprising correction data determined based on said stromal wavefront map.

2. The method according to claim 1, wherein: The epithelial map indicates the thickness of the epithelial layer (26) in the z-direction at various x / y locations.

3. A method according to any one of the preceding claims, wherein: An anterior corneal surface map is provided by the corneal parameters, which include height data of the anterior surface (24) of the cornea (16), wherein an anterior stromal surface map is determined by subtracting the epithelial map from the anterior corneal surface map, and the stromal wavefront map is determined from the anterior stromal surface map.

4. The method according to any one of claims 1 or 2, wherein: An anterior corneal wavefront map is provided from the corneal parameters, wherein an epithelial wavefront map is calculated from the epithelial map for use in calculating the stromal wavefront map, wherein the stromal wavefront map is determined by subtracting the epithelial wavefront map from the anterior corneal wavefront map.

5. A method according to any one of the preceding claims, wherein: Adaptive tissue removal is planned in the matrix (30) based on the correction data, thereby compensating for changes in the epithelial layer (26) after epithelial restoration.

6. A method according to any one of the preceding claims, wherein: Different laser interactions with the tissue of the epithelium (26) and the stroma (30) are taken into account in the control data.

7. A method according to any one of the preceding claims, wherein: The epithelial map is determined by optical coherence tomography and / or ultrasound, in particular ultra-high frequency ultrasound.

8. A control device (18) configured to carry out a respective method according to any of the preceding claims.

9. Treatment device (10) comprising: at least one ophthalmic surgical laser for removing tissue (14) from the cornea (16) of a human or animal eye by optical decomposition, in particular by photodestruction and / or photoablation, and at least one control device (18) according to claim 8.

10. Computer program comprising instructions causing a therapeutic device (10) according to claim 9 to perform a method according to any one of claims 1 to 7.

11. Computer readable medium having stored thereon a computer program according to claim 10.

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