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) for treating a cornea (16) that has been treated with a cross-linking process.A control device (18) sets conventional laser parameters for removing a predetermined correction volume (14) from the cornea (16), wherein the laser parameters include at least a laser pulse energy and a number of laser pulses of the laser (12); provides enhanced laser parameters in areas of the correction volume (14) where a cornea (16) altered by the cross-linking process is expected, wherein the enhanced laser parameters have a higher laser pulse energy and / or a higher number of laser pulses compared to the conventional laser parameters; and provides the control data, which includes the enhanced laser parameters in the areas of the correction volume (14) with altered cornea and the conventional laser parameters in the remaining areas of the correction volume (14).

Description

[0001] The invention relates to a method for providing control data for an ophthalmic laser of a treatment device for treating a cornea treated with a cross-linking method. Furthermore, the invention relates to a control device configured to carry out the method, a treatment device having such a control device, a computer program comprising instructions that cause the treatment device to carry out the method, and a computer-readable medium on which the computer program is stored.

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

[0003] Furthermore, it is known to perform so-called crosslinking (CXL) procedures for the cornea. In this procedure, the cornea is irradiated with UV light, particularly with the help of riboflavin (vitamin B2), which leads to crosslinking of the connective tissue fibers and thus strengthens the structure of the cornea, for example, to stabilize keratoconus.

[0004] However, treatment with such a cross-linking procedure also influences laser pulse interaction with the treated corneal tissue, thereby influencing subsequent treatments with ophthalmic lasers and potentially influencing tissue separation.

[0005] Therefore, it is an object of the present invention to improve the provision of control data for corneas in which a cross-linking process has already been carried out.

[0006] This object is achieved by the independent patent claims. Advantageous developments of the invention are disclosed in the dependent patent claims, the following description, and the figures.

[0007] One aspect of the invention relates to a method for providing control data for an ophthalmic laser of a treatment device for treating a cornea that has been treated with a cross-linking method, wherein the method comprises the following steps performed by a control device. A control device is understood to mean a device or device component, in particular a computer or processor, that can perform the following steps automatically or semi-automatically.

[0008] The method comprises setting conventional laser parameters for removing a predetermined correction volume from the cornea, wherein the laser parameters comprise at least a laser pulse energy and a number of laser pulses of the laser, providing power-increased laser parameters in regions of the correction volume in which a cornea altered by the cross-linking process is expected, wherein the power-increased laser parameters have a higher laser pulse energy and / or higher number of laser pulses compared to the conventional laser parameters, and providing the control data which comprise the power-increased laser parameters in the regions of the correction volume with the altered cornea and the conventional laser parameters in the remaining regions of the correction volume.

[0009] In other words, it may be intended that a cornea be treated on which a cross-linking procedure has already been performed, and thus the cornea exhibits altered areas. For planning the treatment with the treatment device, a predetermined correction volume can be defined, which is to be treated with conventional laser parameters. It can be checked whether there are areas within the predetermined correction volume where the cornea has been altered by the cross-linking procedure. If this is the case, higher-power laser parameters can be planned for these areas compared to the areas where no altered cornea is present in the correction volume.

[0010] The increase in the power of the laser parameters is preferably achieved by increasing the laser pulse energy and / or by increasing the number of laser pulses in these ranges. The increased number of laser pulses can be achieved by increasing the repetition rate and / or by reducing the pulse spacing of the laser pulses in these ranges. Preferably, the increased-power laser parameters provide at least 10% more power than conventional laser parameters.

[0011] In particular, the cornea may exhibit greater stability in areas altered by the cross-linking procedure, requiring higher energy to separate corneal layers. The enhanced laser parameters do not need to be set to a constant value, but can be adjusted depending on the assumed size or thickness of the cornea altered by the cross-linking procedure. Conventional laser parameters can be used for all other areas of the cornea, whereby the conventional laser parameters can be optimized for (photo)ablation and / or photodisruption of the unaltered corneal tissue.

[0012] The areas where corneal changes are expected due to the cross-linking procedure can be estimated, for example, using riboflavin diffusion models in the cornea and / or UV light absorption gradients in the cornea. Alternatively or additionally, the location of the altered cornea can also be determined by pre-treatment measurements of the cornea.

[0013] Finally, control data can be provided, which defines the areas that are irradiated with increased laser power and the areas where conventional laser parameters are used. The control data can include a respective data set for positioning and / or focusing individual laser pulses in the cornea. Additionally or alternatively, the control data can include a respective data set for adjusting 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.

[0014] The invention has the advantage of improving the treatment of corneas that have already been treated with a cross-linking process.

[0015] The invention also includes further developments which result in additional advantages.

[0016] A further development provides that the cornea modified by the cross-linking process is expected to extend from a surface of a corneal stroma to a predetermined depth within the cornea. This means that the cross-linked regions are assumed to extend from an anterior boundary surface of the stroma in the depth direction or z-direction to a predetermined depth within the cornea, which may also be located within the stroma. The predetermined depth can preferably be specified to a depth value of 100 µm, particularly preferably 50 µm, within the corneal stroma.

[0017] These values ​​represent preferred depths at which the cornea is still altered by the cross-linking procedure, with 50 µm being assumed for a conventional cross-linking procedure in which no additional riboflavin is applied and 100 µm for an accelerated cross-linking procedure in which riboflavin is applied. The epithelial layer above the stroma is preferably treated using conventional laser parameters rather than the enhanced laser parameters.

[0018] In an advantageous further development, a gradient of the altered cornea is assumed up to the predetermined depth in the cornea, with the increased power laser parameters being provided depending on the gradient. This means that in the upper corneal layers, the cornea is highly cross-linked and thus altered, with the cross-linking decreasing with increasing depth. Consequently, increased power laser parameters with a high laser pulse power can be provided at positions in the upper corneal layer, with the laser pulse power being able to be reduced with increasing depth in the cornea in accordance with the gradient until it finally reaches the conventional laser parameters at the predetermined depth. This means that the laser power can decrease with increasing depth along the gradient of the cross-linking.This has the advantage that suitable laser parameters can be provided for each degree of cross-linking.

[0019] A further development provides that the cornea altered by the cross-linking process is assumed to be a gradient in the radial direction, with a higher degree of cross-linking being assumed in the center of the cornea than in the periphery of the cornea, with the power-enhanced laser parameters being provided depending on the gradient in the radial direction. For example, with the cross-linking process, diffusion of riboflavin can occur from the inside to the outside, resulting in a higher degree of cross-linking in the center of the cornea than in the periphery. The laser parameters can be adjusted accordingly, so that the power-enhanced laser parameters with the highest power are provided in the center, which are reduced outwards along the radial direction until they finally reach the laser pulse power of the conventional laser parameters.Particularly preferably, the aforementioned gradient in the direction of the depth of the cornea can be combined with the gradient in the radial direction in order to provide the optimized laser parameters depending on the z-direction and depending on the radial direction in order to irradiate the cornea modified by the cross-linking process.

[0020] A further development provides that the areas in which the cornea is expected to be altered by the cross-linking process are determined from predetermined measurement data, in particular by Brillouin spectroscopy. In other words, the areas in which the power-enhanced laser parameters are to be provided can be predetermined by measurements. In these areas, which are determined by measurement, constant power-enhanced laser parameters can be provided, for example, increased by 10% compared to the conventional laser parameters, or the power-enhanced laser parameters can be provided depending on the degree of cross-linking. A preferred way to determine the degree of cross-linking is Brillouin spectroscopy, by means of which the elastic moduli of materials can be determined by examining the inelastic scattering of light by acoustic phonons.This advanced training has the advantage that the areas with altered or cross-linked cornea can be localized most precisely.

[0021] A further development provides that a warning signal is generated if it is determined that the creation of the correction volume will result in the removal of the cornea altered by the cross-linking process exceeding a predetermined threshold. In other words, a warning signal can be provided if it is determined that the removal of the correction volume will result in too much cross-linked tissue being removed from the cornea. The warning signal can, for example, be output to a user via a user interface, for example via a display device or an acoustic device. The control device can compare the size of the correction volume and the percentage of the cornea altered by the cross-linking process that is located in the correction volume.This training can provide a precautionary measure to ensure that not too much of the cross-linked cornea is removed, as this could compromise the stability of the entire cornea.

[0022] A further development provides that the areas exhibiting corneal alteration by the cross-linking procedure are determined based on a previously known duration of the cross-linking procedure and / or a previously known treatment implementation of the cross-linking procedure. In other words, it is possible to estimate the areas of the cornea where cross-linking is occurring and / or the extent to which the cornea is cross-linked in certain areas, if the parameters of the cross-linking procedure used are known. In particular, the duration of the cross-linking procedure can be decisive for the extent to which the riboflavin has penetrated the cornea and thus the depth to which the cross-linked cornea can be expected. For example, depending on the cross-linking procedure used, the duration can range from 5 to 45 minutes.It is also possible to distinguish whether a conventional cross-linking procedure, an accelerated cross-linking procedure, in which additional drugs are administered to accelerate diffusion or osmosis, or a cross-linking procedure in which an epithelial layer remains in place, was used. This advanced technique offers the advantage of allowing for improved localization of the cross-linked cornea.

[0023] A further aspect relates to a method for controlling a treatment device. The method comprises the method steps of at least one embodiment of a method as described above. Furthermore, the method for controlling the treatment device also comprises the step of transmitting the provided control data to at least one ophthalmic laser of the treatment device and controlling the treatment device and / or the laser with the control data.

[0024] The respective method may include at least one additional step that is executed precisely when a use case or application situation occurs that has not been explicitly described here. This step may, for example, include outputting an error message and / or a request for user feedback. Additionally or alternatively, it may be provided that a default setting and / or a predetermined initial state is set.

[0025] A further aspect of the invention relates to a control device which is designed to carry out the steps of at least one embodiment of one or both of the methods described above. For this purpose, the control device can have a computing unit for electronic data processing, such as a processor. The computing unit can comprise at least one microcontroller and / or at least one microprocessor. The computing unit can be embodied as an integrated circuit and / or microchip. Furthermore, the control device can comprise an (electronic) data memory or a memory unit. Program code which encodes the steps of the respective embodiment of the respective method can be stored on the data memory. The program code can comprise the control data for the respective laser.The program code can be executed by the computing unit, causing the control device to execute the respective embodiment. The control device can be embodied as a control chip or control unit. The control device can be comprised, for example, of a computer or computer network.

[0026] A further aspect of the invention relates to a treatment device comprising at least one ophthalmic or ophthalmic laser and a control device configured to perform the steps of at least one embodiment of one or both of the previously described methods. The respective laser can be configured to at least partially separate a predefined corneal volume with predefined interfaces of a human or animal eye by means of optical disruption, 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 refractive index change in the cornea and / or the lens of the eye.

[0027] In a further advantageous development 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 respective pulse duration between 1 fs and 1 ns, preferably between 10 fs and 10 ps, ​​and a repetition frequency greater than 10 kilohertz (kHz), preferably between 100 kHz and 100 megahertz (MHz). 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. In laser technology, this range is subsumed under the term "deep ultraviolet". This advantageously prevents unintentional damage to the cornea from these very short-wave and high-energy rays.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 required for optical breakthrough to be spatially limited, enabling high cutting precision when creating the interfaces. The wavelength range between 700 nm and 780 nm can also be selected.

[0028] In a further advantageous development of the treatment device according to the invention, the control device can have at least one storage device for at least temporarily storing at least one control data set, wherein the control data set(s) comprise control data for positioning and / or focusing individual laser pulses in the cornea; and can have at least one beam device for beam guidance and / or beam shaping and / or beam deflection and / or beam focusing of a laser beam of the laser.

[0029] A further aspect of the invention relates to a computer program. The computer program comprises instructions that, for example, form a program code. The program code can comprise 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, the computer is prompted to execute the previously described method or at least one embodiment thereof.

[0030] A further 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 designed, for example, as a data memory, in particular at least partially as a volatile or non-volatile data memory. A non-volatile data memory can be a flash memory and / or an SSD (solid state drive) and / or a hard disk. A volatile data memory can be a RAM (random access memory). The instructions can be present, for example, as source code of a programming language and / or as assembler and / or as binary code.

[0031] Further features and advantages of one of the described aspects of the invention may arise from the further development of another aspect of the invention. The features of the embodiments of the invention may thus be present in any combination with one another, unless explicitly described as mutually exclusive.

[0032] Additional features and advantages of the invention are described below with reference to the figure(s) in the form of advantageous exemplary embodiments. The features or combinations of features of the exemplary embodiments described below can be present in any combination with one another and / or with the features of the embodiments. This means that the features of the exemplary embodiments can supplement and / or replace the features of the embodiments, and vice versa. Thus, the invention also encompasses and discloses configurations that are not explicitly shown or explained in the figures, but which emerge and can be produced from the exemplary embodiments and / or embodiments through separate combinations of features.Thus, embodiments are also considered to be disclosed that do not have all the features of an originally formulated claim or that go beyond or deviate from the combinations of features set forth in the claims' references. The embodiments are shown in: Fig. 1 a schematic representation of a treatment device according to an exemplary embodiment; Fig. 2 a schematic process diagram for providing control data according to an exemplary embodiment.

[0033] In the figures, identical or functionally identical elements are provided with the same reference numerals.

[0034] The Fig. 1 shows a schematic representation of a treatment device 10 with an ophthalmic laser 12 for removing a correction volume 14 from a human or animal cornea 16 by means of photodisruption and / or ablation. The correction volume 14 can, for example, represent a lenticule or solid body that can be separated from the cornea 16 with the ophthalmic laser 12 to correct a visual impairment. The correction volume 14 or a geometry of the correction volume 14 to be removed can be specified to a control device 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 correction volume 14. Alternatively, the control device 18 can be a control device 18 external to the treatment device 10.

[0035] Furthermore, the Fig. 1, the laser beam 20 generated by the laser 12 can be deflected toward the cornea 16 by means of a beam deflection device 22, such as a rotary scanner, in order to remove the correction volume 14. The beam deflection device 22 can also be controlled by the control device 18 to remove the correction volume 14.

[0036] The laser 12 shown can preferably be a photodisruptive and / or photoablative laser configured to emit laser pulses in a wavelength range between 300 nanometers and 1400 nanometers, preferably between 700 nanometers and 1200 nanometers, with a respective pulse duration between 1 femtosecond and 1 nanosecond, preferably between 10 femtoseconds and 10 picoseconds, and a repetition frequency greater than 10 kilohertz, preferably between 100 kilohertz and 100 megahertz. The control device 18 optionally also has a memory device (not shown) for at least temporarily storing at least one control data set, wherein the control data set(s) comprise control data for positioning and / or focusing individual laser pulses in the cornea.

[0037] If the cornea 16 was treated with a cross-linking process in a pretreatment, areas of the cornea 16 may be altered by the cross-linking and thus have a more rigid structure than untreated areas. This also changes the properties of the cornea 16 with regard to the separation of the correction volume 14, so that the generation of the correction volume 14 with conventional laser parameters is impaired. To take into account the effect of a previous cross-linking process, the control device 18 may Fig. 2 Perform the procedures shown.

[0038] In Fig. 2 is a schematic process diagram for providing control data for an ophthalmic laser 12 of a treatment device 10 for treating a cornea 16, wherein the cornea 16 has previously been treated with a cross-linking process.

[0039] In a step S10, conventional laser parameters can be provided for removing a predetermined correction volume 14 from the cornea 16. The correction volume can be defined, for example, for correcting a visual impairment and / or unnaturally or pathologically altered tissue of the cornea 16 based on predetermined examination data. For this purpose, conventional laser parameters, which in particular include a laser pulse energy and a number of laser pulses per tissue volume, can be planned that are optimized for normal corneal tissue. This means that, with the conventional laser parameters, corneal tissue can be ablated and / or incisions can be made in the corneal tissue without the development of adverse effects, such as an opaque blistering layer or black spots.

[0040] In a step S12, increased-power laser parameters can be planned in regions of the correction volume 14 in which a cornea altered by the cross-linking process is expected. The increased-power laser parameters can have a higher laser pulse power than the conventional laser parameters; for this purpose, in particular, the laser pulse energy can be increased and / or a higher number of laser pulses per volume can be planned. To increase the number of laser pulses, for example, a repetition rate of the laser and / or a laser pulse spacing in the corresponding regions can be changed. The increased-power laser parameters can either be constantly increased compared to the conventional laser parameters, preferably by 10%, or the increased-power laser parameters can be adjusted depending on the degree of the altered cornea.This means that the more cross-linked the cornea is, the higher the laser pulse power can be set, whereby the degree of cross-linking and thus the set laser pulse power can vary depending on the position in the cornea 16.

[0041] Preferably, in step S12, the location of the areas with cornea altered by the cross-linking process can be determined beforehand. Furthermore, the degree of the alteration can be determined. To determine the areas with increased cross-linking, either a measurement can be performed, in particular using Brillouin spectroscopy, or the areas can be estimated using a model.

[0042] When estimating using the model, a previously known treatment execution of the cross-linking method, in particular with a known duration, can be used to determine the areas with altered cornea. In this case, it can be assumed that the cornea 16 has a higher cross-linking on a surface, i.e. in the direction of the treatment device 10, than at a depth, wherein in particular a gradient, i.e. a decrease from the surface to the depth, is present. Thus, for example, the power-increased laser parameters can be selected to be higher on a surface than in a depth direction, wherein the power-increased laser parameters can decrease depending on the depth gradient, preferably down to a predetermined depth of, for example, 100 µm, preferably 50 µm, of the stroma, at which an effect of the cross-linking is no longer expected.

[0043] Similarly, a gradient of cross-linking can be planned in the radial direction, so that a higher degree of cross-linking is assumed in central regions than in the periphery. In other words, with the increased laser parameters, a laser power can decrease from a surface to depth and from a center to a periphery.

[0044] In a step S14, control data can then be generated that includes the increased-power laser parameters in the areas of the correction volume 14 that were modified by the cross-linking process, while the conventional laser parameters can be used in the remaining areas of the correction volume 14. Preferably, the increased-power laser pulse parameters can be planned only in the stroma of the cornea 16, whereby it can be provided that the conventional laser parameters are determined during incisions or ablation in the epithelium of the cornea 16.

[0045] Overall, the examples demonstrate how improved treatment planning can be provided for a cornea 16 that has been pretreated with a cross-linking procedure.

Claims

[1] Method for providing control data for an ophthalmic laser (12) of a treatment device (10) for treating a cornea (16) which has been treated with a cross-linking method, the method comprising the following steps carried out by a control device (18): - Setting conventional laser parameters for removing a predetermined correction volume (14) from the cornea (16), wherein the laser parameters comprise at least a laser pulse energy and a number of laser pulses of the laser (12); - Providing power-enhanced laser parameters in areas of the correction volume (14) in which a cornea (16) altered by the cross-linking process is expected, wherein the power-enhanced laser parameters have a higher laser pulse energy and / or a higher number of laser pulses compared to the conventional laser parameters; - Providing the control data comprising the power-increased laser parameters in the areas of the correction volume (14) with altered cornea and the conventional laser parameters in the remaining areas of the correction volume (14). [2] The method according to claim 1, wherein the cornea (16) altered by the cross-linking process is expected from a surface of a stroma of the cornea (16) to a predetermined depth in the cornea (16). [3] Method according to claim 2, wherein a gradient of the altered cornea is assumed up to the predetermined depth in the cornea (16), wherein the power-enhanced laser parameters are provided as a function of the gradient. [4] Method according to one of claims 2 or 3, wherein the predetermined depth is predetermined up to a depth value of 100 µm, preferably 50 µm, in the stroma of the cornea (16). [5] Method according to one of the preceding claims, wherein the cornea altered by the cross-linking method is assumed to be a gradient in the radial direction, wherein a higher degree of cross-linking is assumed in a center of the cornea (16) than in a periphery of the cornea (16), wherein the power-enhanced laser parameters are provided as a function of the gradient in the radial direction. [6] Method according to one of the preceding claims, wherein the areas in which the cornea is expected to be altered by the cross-linking process are determined from predetermined measurement data, in particular by Brillouin spectroscopy. [7] Method according to one of the preceding claims, wherein a warning signal is generated if it is determined that the generation of the correction volume causes a removal of the cornea altered by the cross-linking process to exceed a predetermined threshold value. [8] Method according to one of the preceding claims, wherein the areas which have the cornea altered by the cross-linking process are determined as a function of a previously known duration of the cross-linking process and / or a previously known treatment implementation of the cross-linking process. [9] Control device (18) which is designed to carry out a respective method according to one of the preceding claims. [10] Treatment device (10) with at least one ophthalmic surgical laser (12) for the separation of a corneal volume (14) of a human or animal eye by means of optical disruption, in particular by means of photodisruption and / or photoablation and at least one control device (18) according to claim 9. [11] A computer program comprising instructions causing the treatment device (10) according to claim 10 to carry out a method according to any one of claims 1 to 8. [12] A computer-readable medium on which a computer program according to claim 11 is stored.

Images