Method for determining irradiation parameters, and apparatus for irradiation

Abstract

The invention relates to a method for determining irradiation parameters for operating a laser (2) for irradiating one or more target regions of the retina (16) of an eye (4) by means of an irradiation beam (11), in which method the retina is fully or partly illuminated by an illumination device (5, 5') under defined illumination parameters, and, during and / or shortly after the illumination, at least one recording, in particular at least one camera image, is captured at least of a target region of the retina, and in which method at least starting values of the irradiation parameters are determined for the irradiation of one or more target regions of the retina using the recording(s) or camera image(s). The invention also relates to a corresponding apparatus in the form of an expanded ophthalmoscope and allows, with the lowest possible complexity, objectified determination of starting values for irradiation parameters during laser treatment of a retina.

Description

[0001] Method for determining irradiation parameters and device for irradiation

[0002] The invention lies in the field of medical measurement technology and specifically relates to a method for determining irradiation parameters for irradiating target areas of the retina of an eye.

[0003] There are known procedures for treating various eye diseases in which laser treatment of the retina can induce tissue changes through so-called laser coagulation. For all types of tissue treatment using a laser, it is important to learn as much as possible in advance about the interaction of the laser beam used with the individual patient's tissue.

[0004] For this purpose, it is known from the prior art to fire so-called titration shots with a laser. This means exposing certain areas of the retina to a laser beam under certain conditions in order to experimentally determine the effect of a certain intensity of laser treatment on the tissue. The disadvantage of this method is that, on the one hand, certain areas of the retina are exposed to the stress of laser treatment without sufficient prior knowledge, and on the other hand, that a certain amount of time is required to evaluate such experiments because the tissue's reaction to the experimental laser treatment must be awaited. Although this only takes a few seconds for each titration shot, it is common practice to use several titration shots, particularly with variable intensity, to determine the tissue's reaction to different laser intensities.The effect of the titration can also be determined by other testing methods if it remains below the visibility threshold in the color image.

[0005] For example, WO 2011 / 038935 A1 discloses a method in which, in conjunction with titration shots on areas of a retina, images of the retina are captured using a camera, from which discoloration of the tissue areas hit by the laser can be detected. In addition, a difference image is generated between the camera images taken before and after the titration, so that the effect of the titration can be derived from the difference values.

[0006] Against the background of the prior art, the object of the present invention is to provide a method and a device for determining irradiation parameters for the operation of a laser for irradiating one or more target areas of the retina of an eye, with which the irradiation parameters can be determined as reliably as possible with the least possible loss of time and the least possible effort.

[0007] According to the invention, the object is achieved by a method having the features of patent claim 1.

[0008] Accordingly, the invention relates to a method for determining irradiation parameters for the operation of a laser for irradiating one or more target areas of the retina of an eye with a treatment beam I, in which the retina is illuminated wholly or partially with an illumination device under defined illumination parameters and during and / or shortly after the illumination at least one optical image, in particular at least one camera image, of at least one target area of ​​the retina is captured and in which at least starting values ​​of the irradiation parameters for the irradiation of one or more target areas of the retina are determined using the image(s) or camera image(s).

[0009] The procedure is intended to enable the pre-treatment determination of irradiation parameters for laser operation as quickly, as fully automated, and as reproducibly as possible. According to the current state of the art, it is often common practice to experimentally apply laser shots (titration shots) to areas of the retina to determine the tissue response in the individual patient. The surgeon often then assesses the degree of tissue discoloration resulting from the laser effect based on their personal impression and adjusts the laser parameters for the irradiation during the actual treatment.

[0010] The method according to the invention makes it possible to completely eliminate or significantly reduce the need for a test run of the laser before treatment. By using timely acquired images or camera images of the retina, an assessment of the individual retinal tissue is objective, transparent, comprehensible, reproducible, and verifiable.

[0011] With the method according to the invention, it may be sufficient to conclusively determine the irradiation parameters for subsequent laser operation for irradiation using the method described, so that the retina only needs to be exposed to laser radiation for treatment and for experimentally determining the necessary laser intensity as part of a titration process. The illumination device can be a visible light source, for example a light-emitting diode or a laser, for example the treatment laser itself, area illumination, for example by means of an illuminated reflective surface, a frosted glass panel illuminated from the back, an LED matrix, or another broadband light source. Illumination beyond the visible regions of the optical spectrum into the infrared or ultraviolet range can also be considered.In this context, defined lighting parameters can include, for example, luminous intensity and wavelength or a wavelength distribution of the emitted radiation. These can, for example, be set to specific values ​​or characteristics. The lighting parameters, such as illuminance, distribution of illuminance, and spectrum / wavelength distribution, can be measured alternatively or additionally, and the measured values ​​can then be used to evaluate the images. It should also be noted that radiation in the non-visible range, such as the infrared range, can also be used. In this case, a captured image or camera image is also an infrared image recorded with appropriate detectors. Hyperspectral sensors, for example, can also be used for the images.Specific areas of the retina, such as target areas, can also be selected automatically or manually for illumination. With automatic selection, specific geometric illumination patterns can be predefined and selectable. The procedure can also utilize raster / scanning methods of illumination and scanning, in which, for example, the target areas or the entire retina are illuminated with a focused light source that covers only a narrowly defined area, and the reflection is recorded using a light-sensitive, non-spatially resolving sensor, such as a photodiode. In this way, the entire area of ​​the retina can be continuously optically scanned, and an optical image of the reflectivity and / or absorption strength can be created.Conversely, the entire retina can be illuminated simultaneously and, using a spatially resolving optical sensor, the light reflected from a limited area of ​​the retina can be continuously / scanned in all areas of the retina or in the target areas, thus creating an optical image of the reflectivity and / or absorption strength of the retina.

[0012] In the context of the present invention, an optical recording can also be understood as an optical imaging capture of the retina.

[0013] Imaging techniques for capturing a retinal image or camera image include fundus photography, fundus reflectometry, autofluorescence imaging, photoacoustic imaging, and functional optical coherence tomography with appropriate illumination devices and techniques. These techniques can be used, for example, to determine the retinal pigmentation intensity, which is crucial for the absorption strength of the treatment beam subsequently used. However, the pigmentation intensity can also be generally determined from the brightness of the retina, which is captured by the image or camera image.

[0014] Often, only specific individual or multiple target areas of the retina are to be treated with a laser beam. In this case, it may be sufficient to illuminate the target areas and capture a photograph or camera image of the target areas. However, it can also be useful to capture photographs / camera images of the entire retina, as the necessary laser irradiation intensity during treatment can be estimated by taking into account the pigmentation intensity in other areas of the retina not intended for treatment. Other, additional non-local characteristics of the person being treated can also be considered when determining the necessary irradiation intensity. Further details on this topic will be provided below.

[0015] A particular implementation of the method described above can also provide that, in order to determine the starting values ​​of the irradiation parameters, the intensity of the pigmentation for one or more target areas of the retina and / or the intensity distribution of the pigmentation on the retina are determined using the recording(s) or the camera image(s). It can also be provided that, in order to determine the starting values ​​of the irradiation parameters for one or more target areas of the retina, additional correction values ​​are determined with regard to the expected absorption and / or scattering of the treatment beam in the vitreous body of the eye on the way to the target areas to be irradiated. The correction values ​​are determined in particular from the optical quality of the optical recording, further in particular from image sharpness or image contrast.

[0016] The sharpness or contrast of the image can be assessed based on imaged retinal inhomogeneities, such as blood vessels or nerve nodes. The sharpness / contrast information obtained from different retinal regions can be compared with each other and / or with stored reference images to assess the influence of scattering / absorption in the vitreous body on the path to the relevant retinal region on image sharpness. This parameter can be determined generally for an eye or depending on the location on the retina.

[0017] For example, it may be advantageous to detect the melanin pigmentation of the retina and, for this purpose, to irradiate the retina with light in the visible range at wavelengths or even exclusively at wavelengths that are particularly well absorbed by the melanin pigmentation.

[0018] For a measurement, wavelengths of illumination and / or detection in the range between 450 nm and 1064 nm can be advantageous. Measurements at wavelengths of 514 nm, 532 nm, or 577 nm can be particularly advantageous. The scattering and absorption of radiation by melanin is strong in this range. Furthermore, wavelengths at which the differences between the absorption strengths of melanin and blood are significant can also be advantageous. It may be useful to compare images taken with radiation at a wavelength of 480 nm (local minimum of absorption in blood) with images taken at 550 nm (local maximum of absorption in blood).Reference values ​​for reflection measurements can be used, for example, in the form of a nerve node, which shows a strong reflection in a healthy state, or areas with blood vessels in which the presence of oxygen-rich or oxygen-poor blood can be selectively detected and, when using suitable wavelengths that can detect these blood variants, useful comparison values ​​can be generated.

[0019] During the subsequent laser treatment of the retina, the treatment beam is partially absorbed or scattered due to the imperfect transparency of the vitreous body of the eye. This effect should be taken into account when determining the laser irradiation parameters, so that the laser intensity is selected somewhat higher than is directly necessary for the treatment of the retina to compensate. The absorption of the treatment beam depends on the individual characteristics of the vitreous body in the patient being treated. Within the scope of the method according to the invention, the absorption can be estimated because the illuminance with which the retina is illuminated is known and the intensity of the backscattered signal, for example the reflected light, depends on both the pigmentation intensity of the retina and the absorption of the light in the vitreous body.To separate the two effects influencing backscattering, multiple measurements can be performed under different optical conditions. Further details will be provided below.

[0020] In many cases it may be useful to illuminate the retina with radiation having a known wavelength distribution in order to generate a camera image, which radiation in particular comprises infrared radiation and / or light in a wavelength range absorbed by melanin, wherein the luminous intensity of the illumination device and / or the total light power incident on a unit area of ​​the retina and / or the light power incident on a unit area of ​​the retina in a defined wavelength range is additionally determined and wherein the brightness values ​​and / or colors of the camera image are used to determine the starting values ​​of the parameters for the irradiation of the retina.

[0021] Starting values ​​for the irradiation parameters can be determined for each individual case from empirical values ​​for the necessary intensity of the treatment beam in conjunction with previously measured brightness values ​​of the retina, whereby, for example, the absorption of the treatment beam by the vitreous body can be represented by an assumed constant value, which can depend, for example, on the age of the patient, among other things.

[0022] In addition, it can advantageously be provided that the thickness of the retina is determined for one or more target areas and taken into account when determining the starting values ​​of the irradiation parameters, wherein the determination of the thickness of the retina is carried out in particular by creating an OCT thickness map of the retina, and / or that the type and intensity of the pigmentation of the body regions of the person to be treated, different from the retina, in particular the type and intensity of the pigmentation of the iris of the eye or the skin or the hair, are used to determine the starting values ​​of the irradiation parameters.

[0023] Using an OCT (optical coherence tomography) measurement, the thickness of the retina can be determined location-dependently. This can be used, for example, to detect retinal edema, which often absorbs part of the laser radiation itself, preventing certain portions of the treatment beam from reaching the pigment layer during the actual treatment. Thus, the OCT thickness map can be used to determine a location-dependent correction value for the irradiation parameters across the entire area or partial areas of the retina.

[0024] In another implementation of the described method, it may also be provided that, in addition to the acquired recording(s) or camera images, one or more predetermined or predefinable reference recordings or reference images are used to determine the starting values ​​of the irradiation parameters.

[0025] The reference images can, for example, represent desired states of the retina, which can be compared with the acquired images / camera images in order to perform a difference value analysis and, from the differences between the acquired image and the reference image, determine the necessary irradiation intensity or the necessary irradiation parameters or their starting values. The irradiation parameters that determine the treatment intensity or irradiation intensity can typically include the strength of the laser beam, i.e., its energy, and its cross-sectional area in the impact area / target area or the size of the laser beam spot, as well as the duration and number of emitted laser pulses and pauses between the laser pulses. Finally, reference images can also be taken from databases, for example, or obtained from previously acquired images / camera images of the same patient.

[0026] In a further implementation of the method described above, it can also be provided that, in order to determine the irradiation parameters or at least starting values ​​of the irradiation parameters for one or more target areas of the retina to be irradiated, on the one hand the intensity of the pigmentation of the target area(s) and, on the other hand, the expected absorption of the treatment beam in the eye lens on the way to the target areas are determined independently of one another by carrying out at least two measurements under different illumination conditions, wherein in the two or more measurements, in particular at least one of the following parameters is varied: size of the focused light spot on the retina, wherein in each case the deviation from an expected light intensity distribution on the area of ​​the focus spot is measured,Direction of incidence of an illumination beam of the illumination device through the pupil and the vitreous body for illuminating the respective target area, direction of incidence to the target area and / or direction of reflection of a detected reflected illumination beam of the illumination device, wavelength range or wavelength distribution of an illumination beam of the illumination device.

[0027] This method allows the distribution of pigmentation intensity on the retina, on the one hand, and the absorption of a laser beam by the vitreous body to be determined independently of one another as a function of the laser target point on the retina and the light path, on the other. For such a measurement, for example, the light path for illuminating a target area of ​​the retina can be changed in several consecutive individual measurements, but the same target area can be illuminated and recorded each time. On the other hand, a target area of ​​the retina can be illuminated in different ways by the illumination device in several measurements while maintaining the same light path, so that the influence of the reflectivity of the retina can be varied by illuminating it with different spectra or by light in different wavelength ranges.

[0028] Alternatively or additionally, it can also be provided that, in order to determine the irradiation parameters for one or more target areas of the retina to be irradiated, on the one hand the intensity of the pigmentation of the target area(s) and / or the expected absorption of the treatment beam in the lens of the eye on the way to the target areas are determined by carrying out at least two measurements, one of the measurements being directed at the absorption and / or reflection characteristics in the area of ​​the papilla and / or at least one blood vessel or part of a blood vessel in the retina, while a second measurement is directed at the absorption and / or reflection characteristics in one of the other areas of the retina to be irradiated.

[0029] The described method can also provide that, in order to determine the irradiation parameters for one or more target areas of the retina to be irradiated, at least two locations on the retina are illuminated one after the other or simultaneously with different illumination characteristics, in particular different illumination intensities, and the intensity of the reflected signal is recorded in each case, that for the locations measured in this way, the functional relationship between the illumination characteristic, in particular the illuminance, and the intensity of the reflected signal, in particular the gradient of the functional curve in the case of a linear relationship, is determined, and that by comparing the functional relationships at the measured locations, in particular the gradients of the functional curves, the ratio of the reflectivities at the measured locations is determined,In particular, one of the sites lies on the surface of a papilla or a blood vessel or at least partially encompasses it. The optic nerve head (papilla) is usually unpigmented and reflects light much more strongly than the pigmented parts of the retina. Furthermore, the reflectivity in the area of ​​the papilla depends only slightly on the characteristics of an individual patient's retina. The papilla can thus serve as a "reflection standard" or reference for a comparative measurement of the intensity of pigmentation.

[0030] The retinal veins can also be detected and used for comparative measurements in the areas of the retina they define. The blood flow has a different absorption characteristic than melanin.

[0031] Absorption also depends on whether the blood is saturated with oxygen or not, i.e., on the type of vessels being used. To be able to measure and evaluate these absorption and reflectivity properties in blood vessels in a differentiated manner, it may be useful to perform a reflectivity or absorption measurement at wavelengths of the illuminating light that are particularly strongly absorbed by the oxygen-saturated or deoxygenated blood. As an alternative to selecting the appropriate illuminating light, the corresponding meaningful wavelengths can also be selected on the detection side.

[0032] It has been shown that the functional relationship between an illumination characteristic, in particular the illuminance on the one hand, and the intensity of the reflected radiation on the other, at a location on the retina allows a reliable determination of a value that represents the reflectivity of the retina at that location. For example, with a linear relationship between the illuminance and the intensity of the reflected radiation, the method of linear regression can be used to determine the gradient of the straight line forming the function graph for a plurality of measurements in order to compensate for measurement errors. The gradients of the straight lines, which can then be assigned to the respective measured locations on the retina, can form a relative measure of reflectivity.By comparing the reflectivity values ​​assigned to the measurement locations with a corresponding relationship, particularly a straight line gradient, at a location where the reflectivity is known or can be easily estimated, the reflectivity values ​​assigned to the measurement locations can then be calibrated. The absorption strength for a treatment beam can then be determined from the reflectivity at a specific location on the retina.

[0033] The wavelength of the radiation illuminating the respective measuring location can also serve as a variable illumination characteristic, so that two locations are then illuminated one after the other with radiation of different wavelengths, the intensity of the reflected radiation is measured in each case and the functional relationship is determined and compared for the two locations.

[0034] The differentiation of reflectivity at different wavelengths can be achieved by sequential illumination with different wavelengths and simultaneous broadband detection (or by a wavelength window), by broadband illumination covering a continuous spectrum, or by illumination by a laser array comprising a plurality of individual wavelengths. In the latter case of broadband excitation / irradiation, wavelength-selective detection of the reflected radiation is then provided, for example, by defining color channels, using wavelength-selective filters, or by using a spectrometer or a multispectral camera.

[0035] Because reflectivity varies only slightly in the optic disc region, any deviation from a reference value between the measured characteristic and the reflectivity value determined from it in a first step can be attributed to the influence of absorption and / or scattering of the radiation on the measurement path through the individual patient's eye. Deviations of the measured values ​​from the reference reflectivity value at a reference location such as the optic disc or the blood vessels can thus be used to determine the attenuation due to absorption and / or scattering in the ocular body.

[0036] By performing multiple measurements at various locations on the retina, the influence of pigmentation on the captured image or camera image, on the one hand, and the influence of vitreous absorption, on the other, can be independently determined and taken into account when determining the irradiation parameters. It should also be noted that the direction of incidence and the direction of reflection of the illumination beam also refer to the light path the laser radiation travels through the vitreous body.

[0037] The way in which illumination parameters and the detected variables / signals of the respective captured image or camera image are linked, on the one hand, to the irradiation parameters for laser operation, on the other, can take many forms. In the simplest case, this can be an assignment table, which can be presented as a multidimensional matrix and stored, for example, in a computer or a non-local or distributed data processing system. The link can also be in the form of an algorithm or a neural network, which can be trained, for example, using self-learning or guided learning methods.

[0038] Against this background, the present invention can also relate to a method for training an algorithm or a neural network for determining the starting values ​​of irradiation parameters according to the method described above, wherein for a plurality of individual treatments, on the one hand, data sets of target areas to be irradiated determined from images and the associated illumination parameters and, in particular, additionally recorded secondary information are linked as input information as training data and, on the other hand, the irradiation parameters set during the respective subsequent laser treatment are linked as result variables.

[0039] The training data can, for example, initially be obtained through parallel operation of a conventional method and the method described here. In each case, as described above, a photograph or camera image is captured under defined lighting conditions. The required treatment intensity, i.e., the intensity of the treatment laser beam, represented, for example, by laser power, pulse duration, pulse number, and repetition rate, is then determined in a conventional manner using titration methods. This can then be linked to the previously recorded photographs / camera images for the target areas of the retina to be treated, so that the learning system is trained with this data.

[0040] The individual treatments used to train the algorithm can also be carried out using the method according to the invention described above. Initially, the starting values ​​for the irradiation parameters are determined, and then the treatment is initiated. The success of the treatment is then assessed by monitoring the discoloration of the target areas, and the irradiation parameters are corrected if necessary. By entering the correction values ​​or linking the correction values ​​with the illuminance parameters and the initially determined starting values ​​for the irradiation parameters, the algorithm can be further trained for improvement.

[0041] Additionally recorded secondary information can include variables that prove to be influential in determining the irradiation parameters. Such secondary information can include, for example, the patient's age and certain parameters of their health status, as well as specific parameters of the patient's retina to be treated. For example, a measured integral pigmentation intensity of the skin or the iris of the eye, or a measured pigmentation intensity of the patient's scalp hair, eyebrow hair, or skin, as well as the color of the skin pigmentation, the color of the iris, and the color of the hair, can be taken into account.

[0042] For example, it may also be provided that when determining the starting values ​​of the irradiation parameters for all target areas, a calibration is carried out using one or more of the following calibration parameters for the respective person to be treated: measured integral pigmentation intensity of the skin, measured integral pigmentation intensity of the iris of the eye, measured pigmentation intensity of the hair (head hair, eyebrows), color of skin pigmentation, color of the iris, color of the hair. Such a calibration may, for example, also provide that the listed variables are not included in the algorithm for determining the irradiation parameters, but that after determining an irradiation intensity, a calibration of the results is carried out using the aforementioned variables, for example by multiplying the irradiation intensity, given by the laser energy and the length of the laser pulse, by a specific calibration factor.

[0043] The invention can also relate to a method for determining irradiation parameters for the operation of a laser for irradiating one or more target areas of the retina of an eye with a treatment beam, in which starting values ​​of the irradiation parameters are first determined according to the method described above, in which at least one target area is then irradiated with a titration beam or a treatment beam with the starting parameters, in which at least one continuation image or one continuation camera image of the target area(s) of the retina irradiated with the treatment beam is then acquired, and in which at least continuation values ​​of the irradiation parameters for the irradiation of one or more target areas of the retina are determined using the continuation image(s) and / or the continuation camera image(s) and the starting values ​​of the irradiation parameters.

[0044] This makes it possible to check the initial values ​​of the irradiation parameters for success as soon as possible after their application and, if necessary, to adjust them or to determine follow-up irradiation parameters from them. The corresponding corrections can also be used, for example, to provide the algorithm with additional training data and thus improve it.

[0045] Finally, in addition to the method described above, the invention also relates to a device for irradiating one or more target areas of the retina of an eye with a treatment beam, with a laser for generating the treatment beam, with an illumination device for illuminating at least one or more target areas of the retina with defined illumination parameters and with an optical recording device, in particular a camera, for capturing at least one recording or an image of at least one target area of ​​the retina and with a processing device which is set up to determine at least starting values ​​of the irradiation parameters for irradiating one or more target areas of the retina with a treatment beam using the illumination parameters and the optical recording(s) or camera image(s).

[0046] This device can be used to carry out the various implementations of the method described above. The processing device can be configured as a data processing device containing an algorithm that assigns the starting values ​​for irradiation parameters to the illumination parameters and the variables captured with the recording or camera image. This algorithm can either be fixed or trained with training data as part of a learning system with artificial intelligence, as already described above. The processing device can, for example, also contain a neural network capable of learning in the manner described by forming its connections through the training process.

[0047] The device can, for example, be completely independent of the treatment device with the treatment laser, or it can be connected to or integrated into the treatment device. For example, the device according to the invention can also be partially centralized, wherein the processing device can be arranged non-locally in a server or a remote data processing system of another type and receives the determined data via a suitable communication method. In this way, the processing device can be fed and trained with measurement data from many different locations, and it can control local treatment devices remotely. In this way, optimal training of the processing device with actual data from one or more patients can be ensured.

[0048] In the following, the invention is shown in exemplary embodiments using figures and is explained below.

[0049] Fig. 1 shows an ophthalmoscope with a device for irradiating the retina of an eye, Fig. 2 shows a flow chart for a method for determining starting values ​​for irradiation parameters,

[0050] Fig. 3 shows an image of target areas of a retina,

[0051] Fig. 4 an enlarged view of the light path through the vitreous body of an eye to the retina,

[0052] Fig. 5 shows an example of illumination parameters, measured values ​​representing a recording of the target areas of a retina, as well as assigned starting values ​​for irradiation parameters,

[0053] Fig. 6 a second flow diagram of a method in which initial values ​​for irradiation parameters are initially determined and these are subsequently checked,

[0054] Fig. 7 is a third flowchart illustrating a method for training an algorithm that is perfected in a self-learning process and assigns the starting values ​​of irradiation parameters to the illumination parameters and other correction variables,

[0055] Fig. 8 schematically shows the connection of input variables and output variables for training the algorithm, as well as

[0056] Figs. 9, 10, 11 show for three different cases the functional relationship between the illuminance and the intensity of the reflected radiation for the papilla / optic nerve and other areas of the retina.

[0057] Figure 1 shows a device according to the invention or a device for carrying out the method according to the invention in the form of an ophthalmoscope or a device that combines the functions of an ophthalmoscope with the functions of laser treatment of the retina. The device has an illumination device 5 with a radiation source 5', which is configured to direct an illumination beam 14 onto the eye 4 and the retina 16 of a patient. This allows the retina 16 to be suitably illuminated for capturing a recording or a camera image. The illumination can be equipped, for example, with a light-emitting diode or an infrared diode as the light source, or with another type of light source that provides a defined wavelength spectrum. The light source can also be a UV light source, for example.

[0058] The ophthalmoscope also has a camera 6, with a sensor designated 7. The sensor can be, for example, a CCD or CMOS sensor. Instead of the camera 6, any other type of device can be provided, for example, a scanning device suitable for detecting radiation reflected or scattered by the retina.

[0059] The aim of operating the illumination device 5 and the camera 6 or an equivalent device is to obtain the most accurate, spatially resolved measurement data possible from the retina 16 under defined illumination conditions by capturing an image of reflected radiation and thus to be able to capture or determine the properties of target areas to be treated.

[0060] The illumination beam 14 and the reflected radiation 15 are collimated and focused in a conventional manner by a suitable optical system 13 comprising mirrors and lenses. The optical system 13 also has a beam splitter 12, which enables a laser beam from the treatment laser 2 to be directed onto the retina 16. Alternatively, the laser beam can also be coupled in without a beam splitter, for example by being guided slightly offset laterally relative to the illumination light. To control the laser 2, a control unit 8 can be provided, which on the one hand controls the illumination device 5, for example, triggers it, and on the other hand captures a camera image from the camera 6 and directly controls the laser 2. The control unit 8 can also control deflecting mirrors 3, which direct the beam path of the treatment beam 11 and thus enable the targeted treatment of individual target areas on the retina 16.For improved control of the laser 2, according to the present invention, a processing device 19 is provided which allows precise processing of recordings / camera images from the camera 6 and links them to the known and defined parameters of the illumination of the retina 16.

[0061] The ophthalmoscope also includes, for example, a sensor 100, for example in the form of a camera, which allows the measurement of the pigmentation color and intensity of the patient's skin, hair, and / or iris. An input device can also be provided with which such a parameter can be entered. In any case, these parameters are sent to the processing device 19 and taken into account there when determining the starting values ​​for the irradiation parameters.

[0062] In the past, the intensity of the laser treatment—that is, the strength and / or duration of the laser pulses used to operate Laser 2—was determined by a surgeon's own assessment after evaluating a retinal image. Titration pulses were first directed at the retina and their effect assessed to scale the laser intensity.

[0063] By illuminating the retina with known illumination parameters and linking them to the retinal image, it is possible for the processing device 19 to objectively assign a laser treatment intensity for each target area on the retina to these partially predetermined, partially measured values. The intensity is determined by the energy of the laser, the size of the laser spot on the retina, and the number, repetition rate, and duration of the pulse(s), as well as the length of the pauses between the pulses. The method according to the invention makes it possible to determine at least starting values ​​for such irradiation by the treatment beam 11, with which the treatment of the retina can be carried out. Figure 2 shows a flow diagram of the method according to the invention, in which, in a first step 20, parameters of the illumination of the illumination device 5 are predetermined.However, the lighting parameters can also already be present and predefined in the lighting device. Alternatively, individual lighting parameters can be specified, for example, by the processing device 19 and sent to the lighting device 5. The lighting parameters, such as the illuminance, distribution of the illuminance intensity, and the spectrum / wavelength distribution, can also be measured, and the measured values ​​can then be used in the evaluation.

[0064] Then, in a second step 21, the illumination device 5 or the light source 5' is operated, and the retina is illuminated accordingly, either continuously or in pulsed form. At the same time, the reflected radiation can be recorded by a camera 6 in a further step 22. Step 22 can be performed simultaneously with the illumination 21 or at a different time than the illumination, for example, if fluorescent radiation is recorded that is known to persist after the excitation radiation.

[0065] The illumination parameters and the measured values ​​recorded by a camera are then linked together in a processing device 19 in a step 23 using an allocation function, for example, an allocation algorithm. Starting values ​​for the irradiation parameters are determined from these variables through the linkage, which are to be converted into irradiation by the operation of the laser 2. Only after the starting values ​​have been determined can a treatment 24 begin, which represents a further step. Step 24 of the actual treatment is separated from the determination of the starting values ​​of the irradiation parameters by the dashed line 25 in the illustration.

[0066] Figure 3 shows a schematic image of the retina 16 of an eye with various target areas. A target area 28 is shown at the edge of the retina, which is not as important for the actual visual performance of the eye as the target areas 25, 26, 27 in the center of the retina 16. The different hatching of the individual target areas is intended to represent different pigmentation intensities or other varying parameters of the individual target areas. This is intended to make it clear that the different target areas require different irradiation parameters for treatment with the laser 2. The size of the target areas 25, 26, 27, 28 can vary and can also be as small as a spatially resolved treatment with a laser 2 allows. The papilla is also shown in Figures 3 and 4 and is designated 40.The optic disc area remains untreated and can serve as a reference for reflectivity compared to the melanin-bearing areas of the retina.

[0067] Figure 4 shows a cross-section through the vitreous body of an eye 4 with an eye lens 29 and a retina 16. A point or target area 32 is indicated on the retina, which can be alternatively illuminated with two different illumination beams 30, 31. Depending on the point of entry of the illumination beam 30, 31 into the eye lens, the light beam takes different paths through the lens and the vitreous body to point 32. If the measured values ​​of the reflected light, which are recorded by the camera 6, are compared with each other in terms of their intensity, the scattering or attenuation of the light on the various light paths through the vitreous body can be recorded in a differentiated manner.By varying the illumination beams, the entire vitreous body of the eye 4 can be measured gradually, so that the influence of the vitreous body through attenuation and scattering on the illumination of the retina as well as the treatment beam for all areas of the eye can be determined.

[0068] Alternatively, it is also possible to allow two different illumination beams 30 to reach the point 32 on the retina 16 along the same light path, but to vary the wavelength of the incident light, for example, so that the same light path through the vitreous body is present for both beams, but for example, in one case a wavelength is selected that corresponds to the optimal absorption wavelength of melanin on the retina, and in another case a wavelength different from this is selected. Thus, the pigmentation with melanin on the retina can be measured, to a first approximation, independently of inhomogeneities in the vitreous body of the eye if the wavelength-dependent attenuation of the vitreous body is neglected in a first step. Alternatively, the illumination beam can also have a broad spectrum or contain several wavelength ranges simultaneously.In this case, the sensor can perform differentiation through wavelength-selective analysis across a wide wavelength range, even beyond the optically visible range. A hyperspectral sensor, for example, can be used for this purpose. Bayer filters can also be used to capture images of the retina.

[0069] Through combined measurements in which both the light path and the wavelength are varied, the wavelength-dependent attenuation values ​​of the vitreous body can then be determined location-dependently. In this way, once the parameters of the light source 5' are known, it is possible to consider the attenuation of both the incident light or radiation on the retina and the influence of the light path on the reflected radiation. This allows, for example, the intensity of melanin pigmentation on the retina to be determined objectively.

[0070] Figure 5 schematically shows the structure of the link between illumination parameters, measured values ​​of the recording / camera image, and the starting values ​​for irradiation parameters. The illumination parameters 33 are designated xi to x n where the individual parameters, for example, represent illuminances—that is, the radiant energy or power emitted by the illumination source—for specific target areas, or the distribution of power across individual wavelength ranges of the emitted radiation, that is, the shape of a wavelength spectrum with corresponding intensities. 35 denotes the mapping function or combination function, which can be designed, for example, as a self-learning algorithm.

[0071] With 34 the parameters yi to y mof the measured values ​​recorded by camera 6 for a specific target area. When these are combined with the illumination parameters, an n-tuple of starting values ​​for irradiation parameters 36 results, which are designated zi to z0 and which, for example, designate the size of the laser's focal spot on the retina, the laser's radiation intensity, the pulse duration, and / or the number of pulses delivered for one or more target areas.

[0072] One aim of the invention is to determine optimized starting values ​​for irradiation parameters for each target area. This result is initially achieved by determining the starting values, which is represented by the dashed dividing line 25 in Figure 5. Actual laser operation of the laser 2 and thus a treatment of the retina can then take place. The influence of the laser treatment on the retina can then be determined by repeating the described process, i.e., illuminating the retina with defined parameters and determining a camera image or recording. The result of the re-recorded camera image can be compared with the originally recorded camera image, and a difference can be determined that shows the effect of the treatment by the laser 2.If the effect of the laser during the treatment does not correspond to the treatment goal to be achieved, on the one hand the algorithm 35 can be corrected or trained, and on the other hand a new set of irradiation parameters can be determined from the illumination parameters during the second illumination and the measurement data recorded with the second camera image.

[0073] Figure 6 initially shows the sequence of method steps 20 to 24 according to Figure 2, whereupon the treatment step 24 is followed by a further step 21' of illuminating the retina with defined illumination parameters and, simultaneously or offset, the recording of a camera image in a step 22', whereupon the illumination parameters and the measurement data recorded with the camera image are linked together to form new irradiation parameters in a further step 23'.

[0074] Figure 7 shows a flowchart in which the structure of the flowchart from Figure 6 is repeated, with the renewed linking 23' of the illumination parameters and camera measurement data taken into account after a first laser action 24 being followed by a further laser treatment 24'. Furthermore, the information from the irradiation parameters determined in the correction process from step 23' is used in a loop to improve the linking algorithm, which is carried out in process steps 23 and 23'. This feedback of correction variables allows the linking algorithm underlying the linking between the illumination parameters, the camera measurement data, and the starting values ​​for irradiation parameters to be successively improved.For this purpose, treatments of one and the same individual or groups of individuals, for example, with similar clinical pictures, can be taken into account to improve the algorithm. The algorithm can also be stored centrally, for example, on a server or in a cloud, and retrieved for individual treatments. Correction values ​​are then fed back to the server or cloud to ensure that as much training data as possible from different treatment processes at different locations can be used to train the algorithm.

[0075] Figure 7 also indicates that in a further method step 37, additional parameters are measured on the individual patient, or rather their eye or retina, which are then fed into the linking step 23 for calibration. For this purpose, in step 37, for example, integral variables of the retina, e.g., an average pigmentation or the intensity of the coloration of the iris of the eye or the color of the iris or the intensity of the skin pigmentation of the individual or the color of the skin pigmentation and / or the color and intensity of the pigmentation of the individual's hair, can be measured with a sensor, in particular a camera, and fed into the linking step 23. The influence of these variables can also be taken into account when training the assignment algorithm or fed into the linking step 23 as calibration parameters for individual treatments.

[0076] Figure 8 shows schematically the development of the assignment algorithm A, A' by linking corrected irradiation parameters 36' with the original illumination parameters xi to x n and the measurement data yi to y determined by the camera image m Before each training step, the initial values ​​36 for irradiation parameters were assigned to the input parameters mentioned above, and the algorithm receives corresponding correction data 36' with irradiation parameters zi' to z0', which are interpreted as optimized result data and sharpen the algorithm. This procedure, after the required number of training runs, optimizes the combination algorithm and thus also optimizes the initial values ​​for irradiation parameters in a first step.

[0077] Figures 9, 10, and 11 show the functional relationship between illuminance and reflected radiation intensity for three different cases, each for the optic disc / optic nerve and a different location on the retina. The graph representing the optic disc is labeled 50, while the graph representing a location in a treatment target area is labeled 51.

[0078] Basically, the method for determining the absorption intensity, which allows direct conclusions to be drawn about the pigmentation intensity of the retina, involves illuminating a location with several different illuminances, either in the region of the optic disc, or on or near a blood vessel, or at another specific location on the retina that is different from the target areas, and simultaneously measuring the intensity of the reflected radiation. The functional relationship between the illuminance and the intensity of the reflected radiation is linear, so that a straight line is approximately obtained. At least, a straight line can be drawn through the measurement points using linear regression, as shown in Figures 9, 10, and 11. The same procedure is carried out for one or more locations in the target areas of the retina that are to be treated later with radiation.The gradients of the determined straight lines represent the reflectivity at the various locations. Since reflectivity in the area of ​​blood vessels and at the optic disc is easy to estimate and largely independent of other conditions of the individual retina, the values ​​determined there can be used to calibrate the measured reflectivity values ​​at the other locations. For this reason, the measured value of the intensity of the reflected radiation in the area of ​​the optic disc or blood vessels can also be used to estimate the scattering and absorption losses of the radiation on the way to the respective location (optic disc or blood vessels or another location where the reflectivity is known) and on the return path after reflection to the sensor with which the intensity of the reflected radiation is measured.This value of scattering and absorption can then also be assumed for the irradiation of the other areas of the retina, since it characterizes the light path through the vitreous body of the eye.

[0079] In detail, Figure 9 shows an example in which the reflectivity and absorption strength in the area of ​​the macula correspond to a normal case.

[0080] Figure 10 shows a case in which the slope of the straight line representing the macula is lower and thus the reflectivity, measured by the slope of the second straight line representing the papilla, is lower and thus the absorption and pigmentation intensity are higher compared to the normal case.

[0081] Figure 11 shows a case in which the slope of the straight line representing the macula is greater than in the cases of Figures 9 and 10 compared to the slope of the straight line representing the optic disc. This measurement therefore represents the case of greater reflectivity at the location of the macula and correspondingly lower absorption intensity and pigmentation. Since the slope of the straight line 50 representing the measurement on the optic disc is significantly lower than in the graphs of Figures 9 and 10, it can be concluded that, assuming the same reflectivity in the optic disc region as in the cases of Figures 9 and 10, the absorption and / or scattering of the ocular body is significantly stronger in the case shown in Figure 11.From the differences in the gradients of the straight lines designated 50 in Figures 9, 10 and 11, an attenuation coefficient can be calculated which represents the scattering and absorption in the case of the eye measured according to Figure 11 and which can be taken into account in the irradiation during treatment.

Claims

OF Claims: Method for determining irradiation parameters for the operation of a laser (2) for irradiating one or more target areas of the retina (16) of an eye (4) with a treatment beam (11), wherein the retina is illuminated wholly or partially with an illumination device (5, 5') under defined illumination parameters and during and / or shortly after illumination at least one optical image, in particular at least one camera image, of at least one target area of ​​the retina is captured and wherein, using the image(s) or camera images, at least starting values ​​of the irradiation parameters for the irradiation of one or more target areas of the retina are determined.A method according to claim 1, characterized in that, to determine the initial values ​​of the irradiation parameters, the intensity of the pigmentation for one or more target areas of the retina and / or the intensity distribution of the pigmentation on the retina are determined using the image^) or the camera image(s). A method according to claim 1 or 2, characterized in that, to determine the initial values ​​of the irradiation parameters for one or more target areas of the retina, correction values ​​are determined with respect to the expected absorption and / or scattering of the treatment beam in the vitreous body of the eye on its way to the target areas to be irradiated, wherein the correction values ​​are determined in particular from the optical quality of the optical image, and further in particular from the image sharpness or image contrast.Method according to claim 1, 2 or 3, characterized in that, to generate a camera image, the retina is illuminated with radiation having a known wavelength distribution, which in particular. comprising infrared radiation and / or light in a wavelength range absorbed by melanin, wherein additionally the luminous intensity of the illumination device and / or the total luminous power incident on a unit area of ​​the retina and / or the luminous power incident on a unit area of ​​the retina in a defined wavelength range is determined, and wherein the brightness values ​​and / or colors of the camera image are used to determine the starting values ​​of the parameters for the irradiation of the retina.

5. Method according to claim 1, 2, 3 or 4, characterized in that the thickness of the retina is determined for one or more target areas and taken into account when determining the initial values ​​of the irradiation parameters, wherein the determination of the thickness of the retina is carried out in particular by creating an OCT thickness map of the retina, and / or that the type and intensity of pigmentation of different body regions of the person to be treated, in particular the type and intensity of pigmentation of the iris of the eye or of the skin or of the hair, are used to determine the initial values ​​of the irradiation parameters.

6. Method according to one of claims 1 to 5, characterized in that, in addition to the recorded images or camera images, one or more predetermined or predefinable reference images or reference pictures are used to determine the starting values ​​of the irradiation parameters.

7. A method according to any one of claims 1 to 6, characterized in that, to determine the irradiation parameters for one or more target areas of the retina to be irradiated, the intensity of the pigmentation of the target area(s) and the expected absorption of the treatment beam in the lens of the eye on the way to the target areas are determined independently of one another by carrying out at least two measurements under different illumination conditions, wherein, in the two or more measurements, in particular at least one of the following The following parameters are varied: size of the focused light spot on the retina, whereby the deviation from an expected light intensity distribution on the area of ​​the focus spot is measured in each case; direction of incidence of an illumination beam from the lighting device through the pupil and the vitreous body to illuminate the respective target area; direction of incidence to the target area and / or direction of reflection of a detected reflected illumination beam from the lighting device; wavelength range or wavelength distribution of an illumination beam from the lighting device.A method according to any one of claims 1 to 7, characterized in that, in order to determine the irradiation parameters for one or more target areas of the retina to be irradiated, the intensity of the pigmentation of the target area(s) and / or the expected absorption of the treatment beam in the lens of the eye on the way to the target areas are determined by carrying out at least two measurements, characterized in that one of the measurements is directed to the absorption and / or reflection characteristics in the area of ​​the optic disc and / or at least one blood vessel or part of a blood vessel in the retina, while a second measurement is directed to the absorption and / or reflection characteristics in one of the other areas of the retina to be irradiated.Method according to one of claims 1 to 8, characterized in that, in order to determine the irradiation parameters for one or more target areas of the retina to be irradiated, at least two locations of the retina are illuminated successively or simultaneously with different illumination characteristics, in particular different illumination intensities, and the intensity of the reflected signal is recorded in each case, that for the locations measured in this way the functional relationship between the illumination characteristic, in particular the illuminance and the intensity of the reflected signal, in particular in the case of a linear relationship the slope of the function curve, is determined, and that by. A comparison of the functional relationships at the measured locations, in particular the slopes of the functional curves, and the ratio of the reflectivities at the measured locations are determined, wherein, in particular, one of the locations lies on the surface of a papilla or a blood vessel or at least partially comprises it. A method for training an algorithm or a neural network to determine the initial values ​​of irradiation parameters according to any one of claims 1 to 9, characterized in that, for a plurality of individual treatments, the training data consists, on the one hand, of data sets of target areas to be irradiated and the associated illumination parameters, and in particular, additionally acquired secondary information, as input information, and, on the other hand, of the irradiation parameters set during the subsequent laser treatment as output variables.Method according to one of claims 1 to 10, characterized in that, when determining the starting parameters for all target areas, a calibration is performed with one or more of the following calibration parameters of the person to be treated: measured integral pigmentation strength of the skin, measured integral pigmentation strength of the iris of the eye, measured pigmentation strength of the hair, color of the skin pigmentation, color of the iris, color of the hair.Method for determining irradiation parameters for the operation of a laser for irradiating one or more target areas of the retina of an eye with a treatment beam, in which initial values ​​of the irradiation parameters are determined according to a method according to one of claims 1 to 11, in which at least one target area is irradiated with a titration beam or a treatment beam with the initial parameters, in which at least one continuation image or a continuation camera image of the target area(s) of the retina irradiated with the treatment beam is acquired, and in which using of the continuation recording(s) or the continuation camera image(s) and the initial values ​​of the irradiation parameters, at least continuation values ​​of the irradiation parameters for the irradiation of one or more target areas of the retina are determined.Device for irradiating one or more target areas of the retina of an eye with a treatment beam, with a laser for generating the treatment beam, with an illumination device for illuminating at least one or more target areas of the retina with defined illumination parameters, and with an optical recording device, in particular a camera, for capturing at least one optical recording or image of at least one target area of ​​the retina, and with a processing device that is configured to determine at least starting values ​​of the irradiation parameters for irradiating one or more target areas of the retina with a treatment beam using the illumination parameters and the recording(s) or camera images.

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