Devices and methods for detecting the presence of an epithelial layer

Abstract

The present invention relates to devices (1) and computer-implemented methods for detecting the presence of an epithelial layer (101) of an eye (100), which enrich solutions from the prior art. For this purpose, the device (1) for detecting the presence of an epithelial layer (101) of an eye (100) comprises an illumination unit (7), which is designed to radiate illumination light (9) into a treatment region (11), an acquisition unit (13), which is designed to detect secondary light (15) originating from the treatment region (11), and an evaluation unit (17) which is designed to compare at least one parameter (19) of the secondary light (15) detected by the acquisition unit (13) with predefined value ranges (21) of the at least one parameter (19) and to determine the presence of the epithelial layer (101) of the eye (100) on the basis of this comparison.

Description

[0001] Devices and methods for detecting the presence of an epithelial layer

[0002] The present invention relates to devices and computer-implemented methods for detecting the presence of an anterior epithelial layer of an eye.

[0003] There are treatments for a patient's eye that, to improve the outcome or achieve a more precise result, require prior removal of the epithelium or epithelial layer. This is the case, for example, with total resection to achieve a desired stromal ablation or with surface masking of the stroma by the epithelial layer. This is recommended, for instance, in trans-PRK (transepithelial photorefractive keratectomy). In this treatment method, the epithelial layer of the eye is not removed mechanically, but rather by the therapeutic radiation itself. Whenever this disclosure refers to an epithelial layer or the epithelium, it always refers to the anterior corneal epithelium layer.

[0004] Furthermore, it may be necessary to prepare a patient's eye before or for an ophthalmological procedure. This is particularly important if the ocular surface has irregularities, such as those caused by scars or other abnormalities. A scarred stroma is generally covered by a correspondingly compensating epithelial layer, so significant variations in the thickness of this layer can occur in the area of ​​a scar. The stroma may exhibit depressions ("valleys") and elevations ("peaks"), with the epithelial layer being thicker in the area of ​​a depression than in the area of ​​an elevation. In other words, the thicker epithelial layer can "fill" a depression and thus smooth out irregularities in the stromal surface.

[0005] Any type of ophthalmological treatment is risky in an eye exhibiting such irregularities, as the epithelial layer and the stroma have different optical properties, whether during ablation with short-pulse lasers (usually emitting in the ultraviolet range) or by creating incisions within the tissue with femtosecond lasers. Further treatments performed within the tissue of the stroma, or more precisely the cornea, such as LIRIC (laser-induced refractive index change) or crosslinking (a [usually] UV irradiation of the eye that increases corneal cross-linking and / or stability), can also be negatively affected by an irregular epithelial layer.

[0006] In these cases, preparing the eye by restoring a smooth (i.e., free of irregularities) stromal surface is desirable and advantageous before the actual treatment. The preceding explanations merely provide examples where considering the removal of the epithelial layer is advantageous and do not claim to be a complete list of possible applications and uses of the present invention.

[0007] Both trans-PRK and the aforementioned preparation of the patient's eye (e.g., by phototherapeutic keratectomy, or PTK) benefit from precise knowledge of whether the epithelial layer has already been (completely) removed or is still present (and to what extent). This is particularly relevant when considering which areas of the eye are already undergoing tissue removal within the stroma.

[0008] The present disclosure describes devices and methods which improve or enhance known methods or devices for detecting an epithelial layer.

[0009] The present invention solves this problem for the aforementioned device for detecting the presence of an epithelial layer of an eye, comprising: an illumination unit configured to shine illumination light into a processing area; a receiving unit configured to detect secondary light originating from the processing area; and an evaluation unit configured to compare at least one parameter of the secondary light detected by the receiving unit with predefined value ranges of the at least one parameter and, based on this comparison, to determine the presence of the epithelial layer of the eye.

[0010] Furthermore, the present invention solves this problem for the aforementioned computer-implemented method for detecting the presence of an epithelial layer of an eye by comprising the following method steps:

[0011] Reading in recording data that represents spatially and / or temporally resolved secondary light originating from the processing area;

[0012] Reading in lighting unit data that represents at least one lighting parameter of a lighting unit;

[0013] - Evaluating at least one parameter from at least one recording of the detected secondary light from the recording data; and

[0014] The device and method compare at least one parameter with predefined value ranges to determine the presence of the epithelial layer of the eye. This allows for the precise detection of the presence of an epithelial layer. It ensures that, based on prior thickness measurements of the epithelial layer and subsequent processing (i.e., ablation of the epithelial layer), only the necessary amount of tissue needs to be removed, thus avoiding excessive and unnecessary stromal removal. Such excessive, unnecessary stromal removal can currently be selected to ensure that the epithelial layer is completely removed over the entire processed and relevant area, exposing the stroma. According to the invention, it is therefore possible to remove precisely the amount of tissue required, but no more than necessary (i.e., as little tissue as possible).Furthermore, this has the additional advantage that the transepithelial ablation of the stroma corresponds to the planned ablation. Patient-specific factors (e.g., the ratio of epithelium to stroma removed), surgical influences (epithelial hydration, fluid accumulation in the ablation area), or other effects can cause a deviation between the actual and planned ablation. This allows for targeted monitoring and control of the transepithelial ablation.

[0015] The term "secondary light originating from the processing area" can refer to both "illumination light reflected from the processing area" and "secondary light emitted from the processing area by excitation from the illumination light." In the case of reflected illumination light, an elastic or inelastic process can occur within the processing area, varying the direction of propagation of the illumination light depending on the process. If the secondary light is generated by excitation from the illumination light, the incident illumination light, with all its parameters, in conjunction with the optical properties of a tissue or sample within the processing area, can be a necessary condition for the generation of the secondary light.

[0016] The following section will explain in detail optional further developments of the aforementioned methods and devices. Features described in the explanation of the method(s) can be applied to the corresponding device. Likewise, explanations of device features can also be mapped to corresponding method steps.

[0017] For example, if the method is described as performing a process step A, it is implied that the corresponding device is designed to perform precisely this process step A. Conversely, a corresponding embodiment of the method includes process step B if a correspondingly designed device has a feature C for performing process step B, or if feature C is designed to perform process step B. The device for detecting the presence of an epithelial layer can be provided as an optional module with which a laser therapy device can be extended. Alternatively, the device can be part of a laser therapy device.

[0018] Optionally or additionally, a device for data processing of a laser therapy device or a laser therapy device itself can be designed to implement an embodiment of the method presented here. For this purpose, it is conceivable that existing elements and / or components of the laser therapy device are used by the described device, or that these elements and / or components provide the data necessary for the execution of the computer-implemented method.

[0019] The lighting unit can consist of or include at least one light source. Possible light sources include, for example, lasers, laser diodes, or incoherent light sources. The at least one light source can provide the illumination continuously or in a modulated manner. Optionally, the light source can provide the illumination continuously or in a modulated manner, meaning that the device and / or the user can control or adjust the operating mode of the at least one light source. The lighting unit can further include imaging optical elements such as lenses and / or mirrors (optionally mounted on a scanner) or other elements, such as diffusers, to optimally apply the illumination or, for example, to control the direction of illumination.

[0020] The illumination reflected from the processing area can be illumination reflected and / or scattered from the processing area. In particular, the illumination incident on the processing area can be elastically reflected or scattered, so that no change or conversion of the illumination occurs. In other words, the wavelength and / or wavelength composition (spectrum) of the reflected illumination corresponds to the wavelength or wavelength composition of the incident illumination.

[0021] It is also conceivable that a light frequency-shifting process of the epithelium or stroma reflects incident illumination light back from the processing area in a directed and / or undirected manner.

[0022] However, it is also conceivable that the secondary light is fluorescence light generated by the interaction of the incident illumination light with a material in the processing area. In such a case, the recording unit can be adapted to the changed wavelength and / or the changed wavelength composition and / or the generally lower intensity of the fluorescence light. This adaptation can be achieved, for example, by spectral edge filters that block the illumination light, which is generally scattered at a higher intensity, and transmit the fluorescence light, which is generally captured at a lower intensity.

[0023] The recording unit can include or consist of at least one sensor or detector. Furthermore, the at least one sensor or detector can measure at a point, along a line, or two-dimensionally. Thus, the sensor or detector can be a point sensor, a line sensor, or an area sensor with a plurality of pixels.

[0024] The recording unit can further comprise any number and / or any combination of imaging optical elements such as lenses and / or mirrors, which image the secondary light originating from the processing area onto the at least one sensor or detector.

[0025] The secondary light originating from the processing area and detected by the recording unit can be detected with spatial and / or temporal resolution. Optionally or alternatively, the recording unit can be configured to detect the secondary light synchronously with the illumination unit. In this latter case, the illumination light from the illumination unit is preferably time-modulated.

[0026] The recording unit provides a time-resolved and / or spatially resolved representation of the detected secondary light originating from the processing area. This representation can be in the form of image or video data in known formats. At least one parameter of the detected secondary light can be determined from this representation. Particularly preferred is a magnitude, i.e., a value of the investigated parameter of the detected secondary light, depending on whether an epithelial layer is present or not.

[0027] Alternatively or additionally, the recording unit can be controlled synchronously with the lighting. This means that the lighting unit shines modulated or pulsed light into the processing area, and the recording unit, synchronized with the respective times of the light emission, detects the secondary light originating from the processing area.

[0028] This can make it possible to increase the sensitivity of the detection and also has the advantage that the power of the illumination light emitted into the processing area can be reduced in order to comply with, for example, illumination or irradiation limits (cf. MPE: maximum permissible exposure).

[0029] When comparing at least one parameter of the secondary light originating from the processing area with the predefined value ranges of the at least one respective parameter, the evaluation unit can analyze at least one parameter from the following list: a reflectance or scattering power of an object located in the processing area; a contrast power of an object located in the processing area; a transparency of an object located in the processing area; and a fluorescence power of an object located in the processing area.

[0030] The above list of parameters is not exhaustive, and further parameters are conceivable for detecting the presence of an epithelial layer. Furthermore, the above parameters can be interrelated and / or the evaluation can be based on any combination of these parameters. For example, the contrast strength can result from the characteristic scattering strength of various locally differing, but nevertheless preferentially adjacent, areas of the (complete or partial) processing area, where, for instance, high contrast can represent a significant difference in scattering strength between different areas of the processing area.

[0031] The reflectance or scattering power can be represented – under given boundary conditions or lighting conditions – by a brightness value and / or a shape of a bright area of ​​the processing area and / or an extent of a bright area of ​​the processing area or by a combination of these features.

[0032] It was found that when an epithelial layer is present on the eye, the illumination light reflected from that eye is largely reflected back from the working area by specular reflection. In contrast, when the epithelial layer is removed from the eye, i.e., when the stroma is exposed, the illumination light reflected from that eye, or rather from the stroma of the eye, is largely reflected back by diffuse reflection and / or scattering.

[0033] At least one parameter of the secondary light originating from a region of the eye within the processing area can thus fundamentally change its properties once the epithelial layer has been completely removed and the stroma of the eye is exposed. This at least one parameter changes when (preferably: precisely when) the stroma (and no longer the epithelium) contributes to the secondary light or reflects the illumination light alone. For such a parameter, depending on the specific design of the illumination unit and / or the recording unit, at least one value range can be predefined within which it can be assumed that the epithelial layer is still present or that the stroma has already been reached (and the epithelial layer completely removed). Such a predefined value range can preferably be stored in the evaluation unit.It is conceivable, optionally, that the predefined value range is also stored in other devices or a separate storage device. The separate storage device can be permanently connected to the device according to the invention or repeatedly connectable to it (i.e., also portable).

[0034] For example, a high contrast between a defined area of ​​the processing area with high intensity of reflected illumination and its surroundings, in which almost no illumination is reflected, can indicate that the epithelial layer is still present and the stroma has not yet been reached.

[0035] If, on the other hand, no or only a slight contrast between the delimited area of ​​the processing zone and its surroundings is detectable by the evaluation unit, then complete removal of the epithelial layer can be assumed. The size, extent, shape, brightness, symmetry, and / or other properties of the reflected illumination light can vary, particularly depending on the illumination unit and / or the recording unit used, so that predefined value ranges for at least one parameter may differ for different devices used to detect the presence of an epithelial layer in the eye.

[0036] In a preferred embodiment, the evaluation unit can be configured to assume the processing area is spherical. Furthermore, the lighting unit can be configured to provide the illumination light, at least in sections, substantially perpendicular to such a spherically assumed processing area.

[0037] A spherically conceived processing area is understood as an imaginary surface curved convexly towards the receiving unit. Such a convex curvature can preferably correspond to a typical corneal curvature, i.e., a typical corneal radius. This can be assumed to be, in particular, 8 mm. Alternatively, the processing area could be conceived as an aspherical surface. Furthermore, it is conceivable that the assumed curvature of the processing area could be modified by the user, i.e., variably adjustable. Thus, it is conceivable that the assumed curvature (spherical, aspherical, or a freeform surface) could be determined based on the eye being treated. This allows for the accurate detection of the presence or absence of the epithelial layer for any eye shape, radius of curvature, and / or size.The following explanations refer to a spherically assumed machining area, but are also valid for aspherically assumed machining areas, or for machining areas that represent a freeform surface.

[0038] With reference to, or based on, this spherically assumed working area, the lighting device emits the illumination light in such a way that it propagates essentially perpendicular to this spherically assumed working area. In other words, the illumination light is preferably directed perpendicularly into each part of the working area.

[0039] This beam pattern of the lighting device can be independent of whether an object is actually located within the working area or not. However, if an object is located within the working area and this object is a patient's eye, the working area, assumed to be spherical, essentially corresponds to the surface of the patient's eye.

[0040] In order to ensure such a beam pattern, the lighting unit may include at least one device from the list of devices, a dome lighting device, a ring lighting device, a side lighting device or a slit lighting device.

[0041] A side illumination device can, for example, be a dark-field illumination device for directional or non-directional light and, for instance, be designed as a point light source. Such a side illumination device can also be referred to as satellite illumination. The side illumination device can, in particular, be arranged symmetrically on two opposite sides of an optical axis for observing an object, especially an eye, located in the processing area.

[0042] In some configurations, any combination of the aforementioned devices may be provided for supplying, controlling, and / or optimizing the application of the illuminating light. Furthermore, the lighting unit may emit illuminating light with adjustable spectral and / or temporal properties. Spectral properties of the illuminating light can, by way of example, include a spectral distribution, a spectral width, or a spectral composition of the emitted illuminating light.

[0043] For example, it is conceivable to match the wavelength of the illumination light to the color of the iris of an eye in the processing area. In this case, a complementary color or a color similar to the complementary color can be chosen to increase visibility.

[0044] Alternatively, it can be advantageous to determine a characteristic of the illuminating light from the lighting device and, based on this characteristic, adjust the detection, for example. This eliminates the need for an adjustable light source in the lighting device.

[0045] In another possible embodiment, the illumination unit can emit light in the blue spectral range, and the recording unit can have a fluorescence detector designed to detect fluorescence light emitted from the processing area. The blue spectral range can be understood to mean light with wavelengths shorter than approximately 450 nm. It is also conceivable to use ultraviolet light from the laser device. Such high-energy light can generate fluorescence on the eye, which can be detected by a suitably adapted recording unit.

[0046] If the laser (for example, an excimer laser) generates the illumination light, it is advantageous for the acquisition to be synchronized, since the laser generally provides pulsed illumination. Furthermore, the acquisition unit can have at least two different filters, one filter being transmissive for the emission of fluorescence from epithelial tissue and a second filter being transmissive for the emission of fluorescence from stromal tissue. This would make it possible to assign each laser pulse to a tissue ablated by that pulse, and the evaluation unit could also be configured to create a three-dimensional ablation tissue map. Optionally, the use of a third filter, transmissive for fluorescence from Bowman's membrane, would be conceivable.

[0047] In a further advantageous embodiment, the distance between the processing area and the lighting unit, and / or the azimuthal arrangement, and / or the meridional arrangement of the lighting unit relative to the processing area, and / or the radius of an annular lighting unit can be variably adjustable. Particularly when the lighting unit does not include a dome lighting device, this ensures that, due to these adjustment options, substantially perpendicular illumination with the lighting light is possible for different areas of the processing area.

[0048] To ensure such illumination, the device can, in a further embodiment, include a scanner that holds the lighting unit in a movable position. The scanner can be configured to vary the azimuthal and / or meridional arrangement of the lighting unit. Such a movable arrangement ensures that the light can be directed perpendicularly or substantially perpendicular to the processing area at different positions of the lighting unit. To optimize the substantially perpendicular incidence of the illumination light from the lighting unit, an azimuthal and / or meridional scanner can be provided. This allows either meridional scanning, with the azimuth angle varying to scan meridian by meridian, or the reverse process can be used. The position and / or orientation of the scanner can be known, measurable, and / or traceable.

[0049] For example, an arc-shaped lighting element is conceivable, extending along a meridian and rotatable around the eye's optical axis (in the azimuthal direction). A scanner could be provided that is designed to rotate such a lighting element around a rotational axis.

[0050] Furthermore, the evaluation unit can be designed to evaluate, depending on an azimuthal and / or meridional position of the illumination unit, an azimuthal and / or meridional area of ​​the detected illumination light corresponding to this azimuthal and / or meridional position with respect to at least one parameter of the detected secondary light.

[0051] This ensures, for example, that only image data corresponding to the actual azimuthal and / or meridional position of the lighting setup is evaluated. In other words, it guarantees that the evaluation of at least one parameter only occurs for those areas where the condition of substantially perpendicular illumination of the processing area is met.

[0052] Alternatively or additionally, it is conceivable that the position of the recording unit or the position of a detector unit or detector device is variable. Such a design makes it possible to change the detection direction and optionally adapt it to the direction of emission of the illumination light by the illumination device, or to couple the directions of the detector device and the illumination device with each other (preferably synchronized). Furthermore, it is also conceivable that the directions of both the emitted illumination light and the direction of detection are coupled during a scan.

[0053] For these adjustment options, familiar actuating elements can be used, such as incremental stepper motors, stages, linear motor actuators and similar motorized elements whose position and / or orientation and / or angular position can be read and thus measured.

[0054] The computer-implemented method according to the invention processes the image acquisition data and illumination unit data to evaluate at least one parameter of the secondary light from at least one image. As a result of this evaluation, the computer-implemented method can determine whether the epithelial layer of the eye is still present in the area under consideration.

[0055] It is irrelevant whether the recording data and lighting unit data are received or loaded live or with any time delay from a memory.

[0056] The procedure can provide the evaluation result. This result can be superimposed, for example, without limitation, on the field of view displayed by a microscope in a viewing unit such as an operating microscope. Displaying the result on a display device such as a monitor is also conceivable. In this case, too, the preferably used method is to superimpose the captured image of the eye (located in the visible spectral range) and the evaluation result indicating whether the epithelial layer has been removed or is still present. Further ocular or treatment data, such as the area to be treated (ablation zone), pupil, topological parameters (ophthalmic pole), non-topological parameters (vertex), apex, pupil center, or eye registration data (cyclorotation, etc.), can be superimposed on such image data.In particular, the target data for epithelial ablation (planning) can also be superimposed on the image data for comparison of the planned to the actual ablation.

[0057] The evaluation process step can also include the process step of detecting at least one abrupt change in brightness in the recording data.

[0058] Such a sudden change in brightness can be understood as a change in the brightness value of individual pixels under consideration. More precisely, for example, an increase in brightness of X percent across a number of Y pixels can be defined as the minimum brightness change to be detected. In particular, this procedural step can be, resemble, or include edge detection.

[0059] In this case, the abrupt change in brightness is to be understood spatially, whereas in other configurations, where the lighting device and / or the recording device are movable, a temporal change in brightness of individual pixels can also be evaluated. Since this temporal change in brightness occurs during scanning, it can ultimately be converted into a spatial change in brightness, which is detected due to the scanning movement.

[0060] Accordingly, in one embodiment of the computer-implemented method, the reading of azimuthal and / or meridional position information of the lighting unit and the selective evaluation of the image data in an image data area, which corresponds to an illumination area extracted from the illumination data, can take place.

[0061] In other words, only those areas of the processing area where the illumination light shining into the processing area strikes it essentially perpendicularly can be considered in the evaluation. During a scan movement, several adjacent areas of the processing area can then be combined.

[0062] The procedure can therefore include the assemblage of an evaluation result from the sequential determination of the presence of the epithelial layer of the eye in or from different azimuthal and / or meridional image data areas.

[0063] This can be understood as a compositing ("stitching") of various evaluation results (for example, camera images) determined from sequentially detected secondary light states into an overall map of the cornea, which represents the areas with and without epithelium.

[0064] Optionally, such an evaluation result can be determined only for pre-defined regions of interest (ROI).

[0065] In a further embodiment, the method can provide information about the presence or absence of the epithelial layer in the form of output data. This output data can be spatially synchronized with the eye, meaning that this information can be uniquely assigned to a specific position on the eye, a process also known as registration. Furthermore, the output data can also include information about a scope of validity. The scope of validity is understood to be the area within the processing field onto which the processing light is directed essentially perpendicularly. Depending on the type of illumination unit and associated light source used, such a scope of validity can have different shapes and / or sizes.

[0066] It is also conceivable that the output data can be transferred to an optical observation element such as an operating microscope and there artificially, i.e. preferably in digital form, or alternatively by optical superposition, superimposed with the optically recorded image from the processing area.

[0067] For example, it is possible for a user to both view the eye through the operating microscope and simultaneously receive information, via an optional marking that is adapted to the brightness and / or color of the background of the optically recorded image of the eye and defines the scope of validity, indicating in which area of ​​the entire (visible and / or displayed) processing area the illumination by means of illumination light is essentially perpendicular.

[0068] Knowing that directional reflection occurs when the epithelial layer is present and diffuse reflection indicates a distant epithelial layer, the user can, guided by the displayed information of the validity range, check for the presence or removal of the epithelial layer within that area. By manually moving the illumination unit and adjusting the superimposed validity range displayed in the operating microscope, the user can also check other areas of the working field for the removal of the epithelial layer.

[0069] Optionally, the operating microscope can display, in addition to the area of ​​validity, the areas identified by the procedure with a remaining epithelial layer and / or the areas with a removed epithelial layer (i.e., with exposed stroma). Alternatively, only the areas identified by the procedure with a remaining epithelial layer and / or with a removed epithelial layer can be displayed.

[0070] In a further embodiment, the procedure can also include comparing a result regarding the presence of the epithelial layer of the eye with epithelial maps determined in advance in a simulation and identifying a representative of the epithelial maps corresponding to the result.

[0071] To create the pre-determined epithelial maps, a prior measurement of the epithelial layer thickness may be necessary. Such a measurement provides the thickness of the epithelial layer as a function of its position (azimuth and meridional) on the patient's eye. Using this measurement and hypothetical assumptions about the amount of tissue removed (also called ablation) with a laser therapy device after applying a specific number of pulses of therapeutic radiation, it is possible to simulate how much of the epithelial layer and, if applicable, how much of the exposed stroma (in areas of thin epithelial layer) remains and / or has been removed. Different ablation rates for different tissue types can be considered in the simulation. Thus, epithelial maps can be viewed as a set of simulated residual epithelial layer thicknesses after a presumed ablation.The number of representatives in such a set can depend in particular on the resolution at which the removal was simulated.

[0072] According to the invention, a result determined by the computer-implemented method regarding the presence of the epithelial layer of the eye can now be compared with these epithelial maps in such a way that the representative of the epithelial maps is identified which has the smallest deviation from the result determined by the method (resulting from a measurement).

[0073] Such a procedure can be further improved by calculating an actual epithelial removal achieved based on the determined epithelial map and the necessary simulated removal stored for this purpose, and by providing the previously calculated result and the corresponding representative of the epithelial maps.

[0074] This can be considered a calibration, as this design of the procedure allows for a comparison of the ablation set on the laser therapy device with the actual ablation achieved (which results from comparing the determined outcome with the epithelial maps, i.e., the identified representative of the epithelial maps). This comparison makes it possible to determine whether less tissue was ablated than set on the laser therapy device, or even whether more tissue was ablated than set. In either case, a subsequent tissue ablation step can be adjusted to the actual status quo.

[0075] If less tissue was removed than set, the amount of tissue remaining can be increased in the next step. Conversely, if more tissue was removed than initially set, the subsequent amount of tissue removed should be reduced to compensate for this discrepancy between the set and actual amount of tissue removed.

[0076] These designs allow only as much eye tissue to be removed as necessary, without removing more stromal tissue than required.

[0077] For this purpose, the device can be configured to recalculate the set of epithelial maps (preferably partially). In particular, recalculating the set of epithelial maps with the newly calculated epithelial ablation rate is advantageous, wherein a first epithelial map of the newly calculated set can represent the status of epithelial ablation at the time the new epithelial ablation rate is determined. The recalculation is based on the determined epithelial ablation rate or the resulting new epithelial-to-stromal ablation ratio. A corresponding embodiment of the method described herein thus includes recalculating the set of epithelial maps or the correlated PTK ablations after each PTK ablation step. This can preferably be based on the current, i.e., newly calibrated, stromal-to-epithelial ablation ratio (SEAR).

[0078] Optionally, the resolution of the (ablation) steps of the epithelial maps can be varied, thus allowing a limited (preferably smaller) number of epithelial maps to be calculated.

[0079] Furthermore, the device can be designed to support the visual comparison of a result regarding the presence of the epithelial layer of the eye with epithelial maps previously determined in a simulation, using computer-aided and / or automated methods. The identification of a corresponding representative of the epithelial maps can thus be facilitated for a user and / or carried out semi-automatically or fully automatically.

[0080] Optionally, the procedure can include search algorithms that, for example, automatically determine the contour of areas where epithelium is still present (or alternatively, the contour of areas where the epithelium has been completely removed) and compare it with the epithelial maps (or their contours). The procedure can thus automatically determine the epithelial map or calibration that best matches the contour. The procedure can therefore (semi-)automatically determine the epithelial removal rate or the removal ratio between stroma and epithelium and, if necessary, apply this information in a recalculation of the epithelial maps.

[0081] Such a recalculation of the epithelial ablation rate (whether based on a user comparison or (partially) automated is irrelevant) has the advantage that after the initial PTK ablation, only a single further PTK ablation may be required to achieve an optimally planned transepithelial ablation.

[0082] To determine the best-correlated calculated epithelial map (or contour) with the determined epithelial map (or contour), known pattern recognition and image processing methods or search algorithms can be used. For example, a type of "plate solving," similar to astrophysical methods in star pattern matching, could be applied using discrete points (support points) of the contour determined by the treatment system, e.g., based on affine transformations. Furthermore, it is conceivable to vary the simulated epithelial map or contours to select the one that shows the best pattern matching with the support points of the real contour.

[0083] In this procedure, the epithelium does not need to be completely removed in all areas, neither during a smoothing treatment nor for transepithelial phototherapeutic keratectomy (TE-PTK) followed by PRK. However, therapeutic TE-PTK typically utilizes full epithelial masking and achieves complete removal of the epithelial layer. Nevertheless, there are conceivable cases in which reasons argue against complete removal (for example, when remaining epithelium is only present outside the optical zone of the eye in peripheral areas not used for vision).

[0084] In the case of TE-PRK, where the PRK directly follows the removal of the epithelium (the TE-PTK ablation step), this full epithelial masking is typically used, whereby, according to the invention, it can be ensured on the one hand that the epithelial layer is completely removed and on the other hand that no further (precautionary) removal of tissue takes place, as this would mean unnecessary removal of stromal tissue.

[0085] In a further embodiment, the method can also include the artificial coloring of areas of the result, whereby either areas where the epithelial layer is present can be artificially colored and / or areas where the epithelial layer has been removed and stroma detected can be artificially colored. This can be understood as a type of false-color representation. The selectable colors can be adjusted according to user preference.

[0086] This can help a user to quickly recognize when the removal of the epithelial layer has been completed (or sufficiently) and the stroma has been reached, or for comparing the determined result with the epithelial maps (see above).

[0087] One embodiment of the method or devices for detecting an epithelial layer can be used, for example, in pure PTK or in combined, sequential treatments (PTK followed by PRK). For this purpose, ablation profiles are preferably generated separately and applied one after the other. In other words, epithelial layer detection can be used in multi-stage treatments.

[0088] The invention also relates to a computer program product comprising commands which, when loaded into a data processing device, cause the device to execute an embodiment of the previously described computer-implemented method for detecting the presence of an epithelial layer of an eye.

[0089] The provision of the computer program product can also be accomplished through a computer-readable non-volatile storage medium that contains or comprises the computer program product described above.

[0090] A computer-readable non-volatile storage medium according to the invention can be a magnetic storage medium, an optical storage medium, or a storage medium based on RAM, ROM, or EEPROM. The storage medium can be a CD, a DVD, a floppy disk, a magnetic tape, a hard disk (HDD or SSD), or another storage medium.

[0091] The invention further relates to a data signal that transmits the computer program product described above. The computer program product can thus be loaded from a remote PC or from a cloud and transmitted in the form of a data signal to a data processing device.

[0092] The following section will explain the aspects of the present invention in more detail with reference to the accompanying drawings. The drawings merely illustrate possible embodiments of the present invention, and the described features can be combined or omitted as desired. Identical features or features with the same function are further indicated by the same reference numerals. Repetitive descriptions of features are avoided, so explanations of features described in preceding figures are also applicable to other figures unless differences are explicitly indicated.

[0093] Explanations of the computer-implemented method can be applied to the device. Likewise, explanations of the device can be applied to the computer-implemented method.

[0094] They show:

[0095] Fig. 1 - Fig. 7 schematic representations of various designs of the device for detecting the presence of an epithelial layer;

[0096] Fig. 8 shows a schematic representation of the computer-implemented

[0097] Procedure; and

[0098] Fig. 9 and Fig. 10 show a schematic representation of a purely exemplary possibility of evaluation for the detection of the presence of an epithelial layer by the computer-implemented method.

[0099] Figure 1 schematically shows a device 1 for detecting the presence of an epithelial layer 101 of an eye 100. The device 1 comprises a lighting unit 7 which shines illumination 9 into a processing area 11.

[0100] Furthermore, the device 1 comprises a receiving unit 13 which detects and / or stores and / or forwards secondary light 15 originating from the processing area 11. The secondary light originating from the processing area 11 can be reflected illumination light 9 or secondary light produced / generated by the illumination light 9, fluorescence light being a purely exemplary case.

[0101] The recording unit 13 is connected to an evaluation unit 17. The evaluation unit 17 includes and / or stores at least one parameter 19 of the secondary light 15 detected by the recording unit 13, as well as a predefined value range 21 of the at least one parameter 19, and / or is configured to read the parameter 19 and / or the value range from a separate storage module or a separate storage device.

[0102] The device 1 can be a self-contained device or part of a module 23, an extension device 25 or a laser therapy device 27.

[0103] Figure 2 shows a schematic representation of a further embodiment of the device 1. In this embodiment, the machining area 11 is assumed to be a spherical machining area 11a. This is defined by a radius 29, which is ideally assumed to be the radius of the eye, i.e., approximately 8 mm.

[0104] Furthermore, Figure 2 shows that the illumination light 9, which is directed into the processing area 11, 11a, hits this processing area 11a essentially perpendicular to the spherical processing area 11a.

[0105] The term 'essentially' means that a minimum specular angle 31 of the illumination 9 can be defined. A section 33 of the spherical processing area 11a is determined by this minimum specular angle 31, whereby the conditions stored in the evaluation unit 17 for determining the presence of an epithelial layer in this area 33 are valid, whereas an evaluation of a further area of ​​the spherical processing area 11a outside of area 33 may lead to incorrect results.

[0106] Figure 3 shows a further embodiment of the device 1, which is located on or encompasses a scanner 35. The illumination unit 7, the recording unit 13, and, in the embodiment shown, also the evaluation unit 17 (this is not strictly necessary in other embodiments) can be moved and / or tilted relative to the spherical processing area 11a by means of the scanner 35.

[0107] This is schematically represented by a horizontal displacement 37, a vertical displacement 39, and a tilting or rotation 41. Due to these displacements 37, 39, and tilting 41, the device 1 can be moved to a further position 43. This further position 43 is schematically represented by dashed lines. The area 33 is now located at a different point within the spherical machining area 11a when the device is in the further position 43. The resulting new area 33 of the further position 43 of the device 1 is designated with the reference numeral 33a for differentiation. Areas 33 and 33a are distinct and at least dependent on the position of the device 1.

[0108] By means of such a scanning device 35, a statement can thus be made about the presence of the epithelial layer over a larger area of ​​the spherical processing area 11a.

[0109] Figure 4 shows a further embodiment of the device 1. In this embodiment, the lighting unit 7 is designed as an arc-shaped lighting unit 7a, wherein this arc-shaped lighting unit 7a can have a limited azimuthal extent.

[0110] Meridionalally, an arc-shaped area 45 of the assumed spherical processing area 11a is illuminated by the illuminating light 9 in such a way that the entire arc-shaped area 45 is illuminated substantially perpendicularly across the spherical processing area 11a. This means that for all incident rays of the illuminating light 9 in the spherical processing area 11a, the glancing angle is greater than or equal to the minimum glancing angle 31.

[0111] This configuration can also be equipped with a scanner 35, which moves the lighting unit 7 around a rotation axis 47 along an azimuthal scan direction 49.

[0112] Accordingly, in an embodiment not shown, the lighting unit 7 can extend in an azimuthal direction and be movably held in a meridional direction by a further embodiment of the scanner 35.

[0113] It is also conceivable that the configuration of the device 1 of Figure 3 is combined with a scanner 35 of Figure 4, using a lighting unit 7 of Figure 3. Figure 5 schematically illustrates such a movement of the scanner 35, with the lighting unit 7 located at a first position 51, a second position 53, a third position 55, and a fourth position 57. Scanning was performed in the azimuthal direction 49 with the meridian unchanged. It is conceivable that the azimuth of the lighting unit 7 could also be changed, so that the areas 33, 33b, 33c, and 33d (in which the condition of substantially perpendicular incidence of the illumination 9 onto the processing area 11a is met) could be located further away from or closer to an apex 59 by such azimuthal scanning. This is not shown here for the sake of clarity.Figures 6 and 7 show two further possible embodiments of the lighting unit 7. In Figure 6, the lighting unit 7 is designed as a ring light 61, defining a ring-shaped area 63 in which the condition of a substantially perpendicular incidence of the illumination light 9 is met. This embodiment can be combined with a Z scanner 35, which varies the distance of the ring light 61 to the spherical processing area 11a and thus allows the size of the ring-shaped area 63 to be varied.

[0114] In Figure 7, the lighting unit 7 is designed as a dome lighting device 65, which is shown in section for clarity, and the illumination 9 is shown only for some possible rays. The illumination 9 strikes the spherical processing area 11a almost perpendicularly across its entire area. Only in the area of ​​an observation aperture 67, through which the receiving unit 13 detects the spherical processing area 11a and the secondary light 15 emanating from it, is there no perpendicular incidence; however, the glancing angle 69 occurring here is greater than or equal to the minimum glancing angle 31.

[0115] Figure 8 schematically illustrates the computer-implemented method for detecting the presence of an epithelial layer in an eye.

[0116] In a first process step S1, recording data is read in. This recording data represents a spatially and / or temporally resolved secondary light 15 originating from the processing area 11.

[0117] In a second process step S2, data from the lighting unit 7 are read in. This data from the lighting unit 7 represents at least one lighting parameter of the lighting unit 7. A possible lighting parameter could be, for example, the (meridional and / or azimuthal) position of the lighting unit 7.

[0118] In a third process step S3, at least one parameter from at least one image of the detected secondary light 15 is evaluated from the image data. Finally, in a fourth process step S4, the at least one parameter is compared with predefined value ranges of the at least one parameter in order to determine the presence (or absence) of the epithelial layer of the eye.

[0119] Further optional process steps (these are shown with dash lines in Figure 8) are conceivable; for example, the evaluation of process step S3 may also include process step S31 of detecting at least one abrupt change in brightness in the recording data.

[0120] Furthermore, it is conceivable that in a further optional process step S32, azimuthal and / or meridional position information of the illumination unit 7 is read in. In conjunction with this process step S32, process step S33, within process step S3, selectively evaluates the image data in an image data area that corresponds to an illumination area extracted from the illumination data. This can be understood as a kind of stitching of areas 33, 33b, 33c, 33d (see Figure 5) and other areas not shown, in each of which the condition of substantially perpendicular illumination of the processing area 11 with the illumination light 9 is met.

[0121] Figures 9 and 10 will now be used as a purely exemplary illustration of an evaluation.

[0122] Figure 9 shows a photograph of an eye 100 at different stages of ablation of the epithelial layer 101. The elements and schematic drawings shown on the left in Figures 9 and 10 represent a lesser ablation by a laser therapy device than those on the right in Figures 9 and 10.

[0123] Figure 9 shows a relevant area 103 in an magnified view 105. The parameters of the illumination unit 7 can be assumed to be irrelevant for these considerations, but the area 103 under consideration fulfills the condition of substantially perpendicular incidence of the illumination light 9.

[0124] The respective magnification 105, which is designated with the reference symbols 105a and 105b for better differentiation, is detected by the recording unit 13 and stored, at least temporarily, in the form of image data 107a and 107b. For illustrative purposes, the image data 107a and 107b are represented in the form of an 8-bit 5x4 matrix. The evaluation unit 17 can now examine the schematic representations 109a and 109b for any abrupt changes in brightness 111. Such an abrupt change in brightness 111 is discernible in the image data 107a and the corresponding representation 109a, whereas the image data 107b and the corresponding representation 109b show a predominantly homogeneous brightness distribution without abrupt changes in brightness.

[0125] The evaluation unit 17 therefore provides a probability P for the presence of the epithelial layer 101 for these image data 107a and 107b.

[0126] For the case shown on the left, the probability P is in the range between 0.5 and 1, meaning that the epithelial layer 101 is still present, whereas the probability P for the case shown on the right is lower, i.e. less than 0.5, which represents the case of a removed epithelial layer 101.

[0127] Reference symbol list

[0128] I Device for detecting the presence of an epithelial layer

[0129] 7 lighting units

[0130] 7a arc-shaped lighting unit

[0131] 9 Lighting light

[0132] II Processing area

[0133] 11a spherical machining area

[0134] 13 Recording unit

[0135] 15 Secondary light

[0136] 17 evaluation units

[0137] 19 parameters of secondary light

[0138] 21 predefined value range

[0139] Module 23

[0140] 25 Extension device

[0141] 27 Laser therapy device

[0142] 29 radius

[0143] 31 minimum glancing angle

[0144] Section / Area 33, 33b, 33c and 33d

[0145] 35 scanners

[0146] 37 horizontal displacement

[0147] 39 vertical displacement

[0148] 41 Tilting

[0149] 43 more positions

[0150] 45 arc-shaped area

[0151] 47 Rotation axis

[0152] 49 azimuthal scan direction

[0153] 51 first position

[0154] 53 second position

[0155] 55 third position

[0156] 57 fourth position

[0157] 59 Apex

[0158] 61 Ring light

[0159] 63 ring-shaped area 65 dome lighting device

[0160] 67 Observation opening

[0161] 69 glancing angles

[0162] 100 Eye 101 Epithelial layer

[0163] 103 relevant area

[0164] 105, 105a, 105b magnifications

[0165] 107a, 107b Image data

[0166] 109a, 109b schematic representations 111 change in brightness

[0167] S1, S2, S3, S4 Procedure steps

[0168] S31, S32, S33 optional process steps

[0169] P Probability of the presence of the epithelial layer

Claims

1. Device (1) for detecting the presence of an epithelial layer (101) of an eye (100), comprising an illumination unit (7) configured to shine illumination light (9) into a processing area (11); a receiving unit (13) configured to detect secondary light (15) originating from the processing area (11); an evaluation unit (17) configured to compare at least one parameter (19) of the secondary light (15) detected by the receiving unit with predefined value ranges (21) of the at least one parameter (19) and, based on this comparison, to determine the presence of the epithelial layer (101) of the eye (100).

2. Device (1) according to claim 1, wherein the receiving unit (13) is configured to detect the secondary light (15) in a spatially resolved and / or temporally resolved manner and / or synchronized manner with the illumination unit (7) and the evaluation unit (17) is configured to determine the presence of the epithelial layer (101) of the eye (100) in a spatially resolved and / or temporally resolved manner.

3. Device (1) according to claim 1 or 2, wherein the evaluation unit (17) includes at least one parameter (19) from the list of parameters (19), comprising: A spatially resolved reflection or scattering power of a [subject] in Processing area (11) of the arranged object; A spatially resolved contrast capability of an object arranged in the processing area (11); A spatially resolved transparency of an object arranged in the processing area (11); A spatially resolved fluorescence power of an object located in the processing area (11); compared with the predefined value ranges (21) of the respective parameter (19).

4. Device (1) according to one of claims 1 to 3, wherein the evaluation unit (17) is configured to assume the processing area (11) as spherical and wherein the lighting unit (7) is configured to provide the lighting light (9) at least to provide section by section substantially perpendicular to such a spherically assumed processing area (11a).

5. Device (1) according to any one of claims 1 to 4, wherein the lighting unit (7) comprises at least one device from the list of devices comprising: a dome lighting device (65); a ring lighting device (61); a side lighting device; and a slit lighting device.

6. Device (1) according to one of claims 1 to 5, wherein the lighting unit (7) provides lighting light (9) with - adjustable spectral properties and / or spectral composition; and / or - emitted with adjustable temporal properties.

7. Device (1) according to one of claims 1 to 6, wherein the illumination unit (7) emits illumination light (9) in the blue spectral range and the receiving unit (13) has a fluorescence detector configured to detect fluorescence light emitted from the processing area (11).

8. Device (1) according to one of claims 1 to 7, wherein a distance between the processing area (11) and the lighting unit (7) and / or an azimuthal arrangement, and / or a meridional arrangement of the lighting unit (7) to the processing area (11) and / or a radius (29) of an annular lighting unit (61) is variably adjustable.

9. Device (1) according to one of claims 1 to 8, further comprising a scanner (35) movably holding the lighting unit (7), wherein the scanner (35) is configured to vary an azimuthal or meridional or azimuthal plus meridional arrangement of the lighting unit (7).

10. Device (1) according to claim 9, wherein the evaluation unit (17) is configured to provide an azimuthal and / or meridional position corresponding to the azimuthal and / or meridional position of the lighting unit (7). and / or meridional area of ​​the detected secondary light (15) with respect to at least one parameter (19) of the detected secondary light (15).

11. Computer-implemented method for detecting the presence of an epithelial layer (101) of an eye (100), comprising: Reading in recording data (107a, 107b) which represent spatially and / or temporally resolved secondary light (15) originating from the processing area (11); Reading data from the lighting unit (7), which represents at least one lighting parameter of a lighting unit (7); - Evaluating at least one parameter (19) from at least one recording of the detected secondary light (15) from the recording data (107a, 107b); and - Comparing the at least one parameter (19) with predefined value ranges (21) of the at least one parameter (19) to determine the presence of the epithelial layer (101) of the eye (100).

12. Method according to claim 11, wherein the evaluation further comprises the method step of detecting at least one abrupt change in brightness (111) in the recording data (107a, 107b).

13. Method according to claim 11 or 12, wherein the method further comprises: reading in an azimuthal and / or meridional position information of the illumination unit (7); and selectively evaluating the image data (107a, 107b) in an image data area which corresponds to an illumination area extracted from the illumination data.

14. Method according to one of claims 11 to 13, wherein the evaluation further comprises: the assembly of an evaluation result from the sequential determination of the presence of the epithelial layer (101) of the eye (100) in or from different azimuthal and / or meridional image data areas.

15. Method according to one of claims 11 to 14, wherein the evaluation result is determined only for certain regions of interest (ROI).

16. Method according to any one of claims 11 to 15 further comprising comparing a result regarding the presence of the epithelial layer (101) of the eye (100) using epithelial maps determined in advance in a simulation and identifying a representative of the epithelial maps corresponding to the result.

17. Method according to any one of claims 11 to 16, further comprising calculating the actual epithelial removal achieved based on the determined Epithelial map and the necessary simulated ablation stored for this purpose; and providing the previously calculated result and the associated representative of the epithelial maps.

18. A method according to any one of claims 11 to 17 further comprises artificially staining areas (33) of the result, wherein either areas (33) in which the epithelial layer (101) is present are artificially stained and / or areas (33) in which the epithelial layer (101) has been removed and stroma has been detected are artificially stained.

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