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

Abstract

The invention relates to a method for providing control data for an ophthalmic laser (12) of a treatment device (10). The method comprises, as steps: determining parameters of an epithelial layer and a stroma of a cornea (16); determining a correction profile (14) for correcting a refractive error of the cornea (16); determining data of a virtual postoperative cornea expected by treating the cornea (16) with the correction profile (14), wherein the data of the virtual postoperative cornea are determined as a function of an epithelial layer model in which epithelial regrowth of the cornea is modeled, wherein model parameters of the epithelial layer model are provided from statistics of epithelial regrowth processes of a given population group;a determination of a correction difference between an originally planned correction and a virtually achieved correction; an adjustment of the correction profile (14) depending on the correction difference; and a provision of the control data for the ophthalmic laser (12) that includes the adjusted correction profile.;

Description

The invention relates to a method for providing control data for an ophthalmic laser of a treatment device. The invention further relates to a treatment device comprising at least one ophthalmic laser and at least one control unit for carrying out the method, a computer program, and a computer-readable medium. 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 photoablation in a focus located within the organic tissue in order to remove tissue from the cornea. However, it can happen that the actual corneal correction achieved differs from the planned correction and / or that the treatment produces undesirable aberrations. These effects can be attributed in particular to corneal regeneration processes. From DE 10 2023 106 466 A1, a method for providing control data for an ophthalmic laser is known. The method comprises determining an initial correction value for correcting a corneal refractive error from predetermined examination data, determining epithelial layer parameters from the predetermined examination data and providing an epithelial layer regeneration model that describes the regeneration of an epithelial layer with the determined epithelial layer parameters, determining an adapted correction value depending on the initial correction value and the epithelial layer regeneration model, and providing the control data for the ophthalmic laser, which includes the adapted correction value. WO 2009 / 124268 A3 discloses methods for designing corneal implants to compensate for corneal reactions, such as epithelial changes in an epithelial layer, when the implant is present. Additionally, methods for performing alternative procedures to correct corneal vision are disclosed to compensate for an epithelial reaction to the procedure. The object of the present invention is to improve a correction profile for the treatment of a cornea. This problem is solved by the independent patent claims. Advantageous developments are disclosed in the dependent patent claims, the following description, and the figures. The invention is based on the idea of ​​modeling corneal regeneration processes, in particular the regrowth of an epithelial layer, in order to obtain a tailored correction profile for treatment planning to achieve the desired correction. The model parameters of the epithelial layer model used for this purpose can be derived from statistics on other individuals or other patients. 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 performed by a control unit. A control unit is understood to be a device or device component, in particular a processor or microprocessor, configured to perform the following method steps: determining parameters of an epithelial layer and a stroma of the cornea from predetermined examination data; determining a correction profile for correcting a corneal refractive error from the parameters of the epithelial layer and the stroma; and determining data of a virtual postoperative cornea expected from the treatment of the cornea with the correction profile, wherein the data of the postoperative cornea are determined as a function of an epithelial layer model.in which the regrowth of the corneal epithelial layer is modeled so that the effect of treatment with the correction profile on the parameters of the epithelial layer and the stroma can be predicted, whereby model parameters of the epithelial layer model are provided from a statistic of epithelial layer regrowth processes of a given population group. Furthermore, a correction difference is determined between an originally planned correction using the correction profile and a virtually achieved correction, which is determined from the data obtained of the virtual postoperative cornea, the correction profile is adjusted depending on the correction difference, and the control data for the ophthalmic laser, which includes the adjusted correction profile, is provided. In other words, parameters of an existing epithelial layer and stroma of a patient's cornea can first be determined from predetermined examination data, from which a correction profile for refractive error correction can be derived. These parameters can include, for example, thickness and / or curvature at a specific location. Subsequently, it can be simulated what a postoperative cornea treated with the determined correction profile will look like, exhibiting the determined parameters of the epithelial layer and stroma. An epithelial layer model can be used for the simulation, allowing the regeneration of the corneal epithelium to be determined, so that the virtual postoperative cornea can represent the corneal condition after treatment and following a regeneration process. The epithelial layer model can incorporate several assumptions about epithelial layer regeneration, in particular the rate at which the epithelial layer regenerates, the rate at which it is shed, the displacement of the epithelial layer within the cornea, and / or the location of epithelial layer regeneration. These model parameters can be derived from statistics of a population. This means that the model parameters are measured in previously treated patients or in untreated individuals from multiple studies, preferably conducted over an extended period, and can then be applied to the epithelial layer model for treatment purposes. After the virtual postoperative cornea has been modeled with a regenerated epithelial layer, a correction difference can be determined between the originally planned correction, which was intended to be generated by the initially determined correction profile, and the correction that can be obtained from the data obtained from the virtual postoperative cornea. If such a correction difference is detected, particularly if it exceeds a predefined threshold, the originally planned correction profile can be adjusted accordingly. For example, the correction difference may reveal that an originally planned correction is too small, and this difference can then be compensated for by adjusting the correction profile. Finally, control data for the ophthalmic laser can be provided, encompassing the customized correction profile. Specifically, this can include determining the positioning and / or sequence of the laser pulses to generate the customized correction profile, for example, using a further algorithm. The control data can include the respective 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 adjusting at least one beam device for beam guidance, shaping, deflection, and / or focusing of the ophthalmic laser beam. Thus, the epithelial layer model can be used to estimate how the cornea will look after treatment, allowing for the prediction of topography, refraction, and / or aberrations. Furthermore, it can be determined when, after treatment, the different model parameters need to stabilize, i.e., converge, thereby enabling an estimation of the completion of the healing process. The invention offers the advantage that the planning of correction profiles can be improved, since a desired treatment result can be taken into account during the planning by considering regeneration processes of the epithelial layer. Furthermore, according to the invention, model parameters for the epithelial layer model are selected from a population with comparable parameters of the epithelial layer and the stroma. This means that a subset of model parameters can be used whose parameters for the epithelial layer and the stroma are comparable. The parameters can be considered comparable, for example, if they deviate from the determined parameters of the cornea to be treated by no more than a predetermined value, for example, by no more than 25%, preferably 10%. This has the advantage that the epithelial layer model can be better adapted to the cornea to be treated, which improves the correction results. The invention also includes embodiments that offer additional advantages. One embodiment provides that the model parameters for the epithelial layer model are selected from a population group with comparable patient ages. In particular, model parameters, such as the epithelial layer regeneration rate, can be age-dependent, with older patients, for example, exhibiting a lower regeneration rate. Therefore, when determining the virtual postoperative cornea, an epithelial layer model can be used that only includes the model parameters of the population group with comparable ages. For this purpose, several age ranges can be predefined for which model parameters are available, and the age range corresponding to the patient with the cornea to be treated can be selected.This embodiment offers the advantage of increasing the accuracy of the epithelial layer model, which improves treatment. Another embodiment provides that the model parameters of the epithelial layer model include a regrowth rate, epithelial layer migration, and / or epithelial layer loss. This means that not only can the regrowth of the epithelial layer be taken into account, but also, for example, that an upper layer of the epithelium is removed and that the epithelial layer shifts within the cornea during regrowth. In particular, an equilibrium of these processes can be established, which can be incorporated into the epithelial layer model. This offers the advantage of achieving an improved simulation of the virtual postoperative cornea. Another embodiment involves determining corneal topography and / or refractive values ​​and / or higher-order aberrations as the correction difference between the originally planned treatment and the virtually achieved correction. If differences exist between the aforementioned values ​​and the virtually achieved values, the initially planned correction profile can be adjusted based on this difference to ensure treatment success. Another embodiment involves using the epithelial layer model to model the virtual postoperative cornea for predetermined future time points. For example, the epithelial layer model can be used to model how the cornea will look at specific points in time after treatment. Here, the virtual postoperative cornea can be simulated for a time point one month or 12 months after treatment. Within this period, the corneal regeneration process is typically complete. Another embodiment provides that the epithelial layer model is used to additionally estimate when the healing process of the cornea treated with the correction profile is complete. For example, it can be verified when the model parameters of the epithelial layer model converge, thus indicating that the epithelial layer no longer changes. This point in time can then be defined as the completion of the corneal healing process. In particular, it can be provided that the initially planned correction profile is adjusted to achieve a faster healing process. For example, the thickness and / or diameter of the planned correction profile can be adjusted so that the same correction is achieved, but the healing process is potentially shortened, and this can be verified using the epithelial layer model. Alternatively, it can be estimated when further treatment of the cornea is possible.For example, if it is determined that the healing process is not yet complete during a planned follow-up treatment, a warning message can be generated. Another embodiment provides that the parameters of the epithelial layer and / or the stroma are determined by corneal tomography. This means that the examination data includes at least one corneal tomography scan, which can, for example, indicate thickness at a given location. The 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 include setting a default value and / or a predetermined initial state.Another aspect of the invention relates to a control device configured to perform the steps of at least one embodiment of the previously described method. 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 a 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 method, may be stored in the data storage device. The program code may include the control data for the respective laser. The program code can be executed by means of the computing unit, thereby causing the control device to execute the respective embodiment.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. A further 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 the method described above. The respective laser can be configured to at least partially separate a predefined corneal volume 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, and / or to increase corneal crosslinking. 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 900 nm and 1200 nm, with a pulse duration of 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). The use of such lasers in the method according to the invention also has the advantage that the irradiation of the cornea does not have to take place in a wavelength range below 300 nm. This range is referred to in laser technology as "deep ultraviolet." This advantageously avoids unintentional damage to the cornea caused by these very short-wavelength and high-energy beams.Photodisruptive and / or ablative 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, necessary for optical breakthrough, to be spatially tightly limited, thus enabling high cutting accuracy in the generation of interfaces. The wavelength range between 700 nm and 780 nm can also be selected. 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 150 nm and 300 nm, preferably between 180 nm and 230 nm, with a pulse duration between 10 fs and 100 ns, preferably between 100 fs and 1 ns, and a repetition frequency greater than 100 Hz, preferably between 1 kHz and 1 MHz. These parameter ranges are commonly used for photoablation with an excimer laser, in which corneal tissue is removed by ablation. This is performed, for example, in photoablative refractive keratectomy (PRK), laser-assisted epithelial keratomileusis (LASEK), or laser-assisted in situ keratomileusis (LASIK). 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 temporary storage of 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. Another 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. Another 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, designed 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. 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. Additional features and advantages of the invention are described below with reference to the figure(s) in the form of advantageous embodiments. The features or combinations of features of the embodiments described below can be combined with each other 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. Therefore, 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 out in the cross-references of the claims, are also to be considered disclosed. Regarding exemplary embodiments: Fig. 1 shows a treatment device according to an exemplary embodiment; Fig. 2 shows a process diagram for a process according to an exemplary embodiment. In the figures, identical or functionally equivalent elements are provided with the same reference symbols. Figure 1 shows a schematic representation of a treatment device 10 with an ophthalmic laser 12 for removing tissue from a human or animal cornea 16 by means of photodisruption and / or photoablation. The tissue to be removed can be defined, for example, by a correction profile 14, by which a volume can be separated or ablated from the cornea 16 with the ophthalmic laser 12 to correct a refractive error. That is, a geometry of the tissue to be removed can be provided by the correction profile 14, wherein the correction profile 14 can be specified to a control unit 18, in particular in the form of control data, so that the laser 12 emits pulsed laser pulses into the cornea 16 of the eye in a pattern predefined by the control data in order to remove the tissue.Alternatively, the control device 18 can be an external control device 18 with respect to the treatment device 10. Furthermore, Fig. 1 shows that the laser beam 20 generated by the laser 12 can be deflected towards the cornea 16 by means of a beam deflection device 22, such as a rotary scanner, in order to remove the tissue. The beam deflection device 22 can also be controlled by the control unit 18. The laser 12 shown is preferably 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 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 includes a storage 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. After creating the correction profile 14 in the cornea 16, a follow-up examination may reveal that the actual correction achieved differs from the originally planned correction. This can be attributed to a regeneration process of an epithelial layer of the cornea 16, which can regrow, resulting in more residual tissue than intended by the treatment. To account for this effect, the procedure shown in Fig. 2 can be performed. Figure 2 shows a method for providing control data for the ophthalmic laser 12 of the treatment device 10, wherein the steps can be performed by the control unit 18 of the treatment device 10 or an external control unit. In step S10, parameters of an epithelial layer and a stroma of the cornea to be treated 16 can first be determined from predetermined examination data. For example, the thickness of the respective layer can be determined from a tomography of the cornea 16. Furthermore, a refractive error that is to be corrected by the treatment can be determined. In step S12, a correction profile 14 for correcting the refractive error of the cornea 16 can be determined from the ascertained parameters. The correction profile 14 can, for example, be an ablation profile or an ablation map. Thus, the correction profile 14 provides a previously planned correction of the cornea 16. The correction profile 14 can preferably be planned in such a way that it corresponds to an optical zone. In particular, the correction profile 14 can specify the desired change of the cornea 16 or the corneal surface. In step S14, data for a virtual postoperative cornea expected after correction using correction profile 14 can be determined. The virtual postoperative cornea can be determined using an epithelial layer model, which can, in particular, simulate the regrowth of the corneal epithelial layer 16. Preferably, the epithelial layer model can simulate epithelial layer regrowth, epithelial layer displacement within the cornea 16, and epithelial layer loss through the removal of epithelial layer cells from the corneal surface 16. Model parameters for the epithelial layer model can be predetermined from statistics of a population group. In particular, typical epithelial layer regrowth rates in other individuals, especially previously treated patients, who have been monitored by multiple measurements, can be determined using these statistics.The statistics can, for example, include a mean or median of the determined values, which can be provided as model parameters. Furthermore, model parameters for epithelial layer migration and / or epithelial layer loss can be determined in this way. Preferably, the model parameters used to determine the virtual postoperative cornea in the epithelial layer model can be derived from a comparable population and are most similar to the initially determined parameters of the epithelial layer and corneal stroma 16. Furthermore, preferably, the model parameters can be derived from a population of comparable age. After the virtual postoperative cornea has been simulated for a point in time after treatment, for example, within a period of 1 to 12 months post-treatment, it can be determined in step S16 whether there is a difference (correction difference) between the originally planned correction and a virtually achieved correction, which is determined from the data obtained for the virtual postoperative cornea. In other words, it can be determined whether the virtual postoperative cornea looks like the originally planned cornea, with any deviation representing a correction difference. If no correction difference is found, the originally planned correction profile 14 can be used to treat the cornea 16. However, if a correction difference is detected, particularly one that exceeds a predefined threshold, which could, for example, be specified as the maximum tolerable deviation, the originally planned correction profile 14 can be adjusted in step S18 depending on the determined correction difference. Finally, in one step, S20 control data for the ophthalmic laser 12 can be provided, which includes the adapted correction profile. This means that the adapted correction profile can be converted into global coordinates for calculating the positioning and laser pulse sequence. Overall, the examples show how the regrowth of an epithelial layer can be taken into account for treatment with an ophthalmic laser.

Claims

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 parameters of an epithelial layer and a stroma of a cornea (16) from predetermined examination data; - Determining a correction profile (14) for correcting a refractive error of the cornea (16) from the parameters of the epithelial layer and the stroma;- Determining data of a virtual postoperative cornea expected by treating the cornea (16) with the correction profile (14), wherein the data of the virtual postoperative cornea are determined as a function of an epithelial layer model in which corneal epithelial layer regrowth is modeled, so that an effect of the treatment with the correction profile (14) on the parameters of the epithelial layer and the stroma is predicted, wherein model parameters of the epithelial layer model are provided from statistics of epithelial layer regrowth processes of a given population; - Determining a correction difference between an originally planned correction using the correction profile (14) and a virtually achieved correction, which is determined from the determined data of the virtual postoperative cornea; - Adjusting the correction profile (14) as a function of the correction difference;- Providing the control data for the ophthalmic laser (12) which includes the adapted correction profile;- wherein, for the epithelial layer model, model parameters are selected from a population group with comparable parameters of the epithelial layer and the stroma.; Method according to claim 1, wherein the model parameters for the epithelial layer model are selected from a population group with comparable patient age. Method according to one of the preceding claims, wherein the model parameters of the epithelial layer model provide a regrowth rate, an epithelial layer migration and / or an epithelial layer loss. Method according to one of the preceding claims, wherein the correction difference between the originally planned treatment and the virtually achieved correction is determined to be a corneal topography and / or refraction values ​​and / or higher order aberrations. Method according to one of the preceding claims, wherein the virtual postoperative cornea is modeled for predetermined future time points using the epithelial layer model. Method according to claim 5, wherein the time points are within a time frame between 1 month and 12 months. Method according to one of the preceding claims, wherein the epithelial layer model additionally estimates when a healing process of the cornea (16) treated with the correction profile (14) is completed. Method according to one of the preceding claims, wherein the parameters of the epithelial layer and / or the stroma are determined by tomography of the cornea (16). Control device (18) which is configured to carry out a procedure according to any of the preceding claims. Treatment device (10) comprising at least one ophthalmic laser (12) for the treatment of a cornea (16) of a human or animal eye by means of optical breakthrough, in particular by means of photodisruption and / or photoablation and at least one control device according to claim 9. Computer program comprising commands that cause the treatment device (10) according to claim 10 to perform a method according to any one of claims 1 to 8. Computer-readable medium on which a computer program according to claim 11 is stored.

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