Irradiation parameter determination method and irradiation device

Abstract

The invention relates to a method for determining irradiation parameters for the operation of a laser (2) for irradiating one or more target areas of a retina (16) of an eye (4) with an irradiation beam (11), in which the whole or part of the retina is illuminated by an illumination device (5, 5') under defined illumination parameters, at least one recording (particularly at least one camera image) of at least one target area of ​​the retina is captured during and / or immediately after the illumination, and in which the recording or the camera image is used to determine at least starting values ​​of the irradiation parameters for the irradiation of one or more target areas of the retina. The invention also relates to a corresponding device in the form of an extended ophthalmoscope, which allows an objectified determination of starting values ​​of irradiation parameters during a laser treatment of the retina with as little complexity as possible.

Description

[Technical field]

[0001] The present invention is in the field of medical measurement technology, and in particular relates to a method for determining illumination parameters for irradiating a target area on the retina of an eye. [Background technology]

[0002] It is known how laser therapy of the retina can cause tissue changes by so-called laser coagulation for the treatment of various eye diseases. In any type of tissue treatment using a laser, it is important to know as much as possible in advance regarding the interaction of the laser beam used with the tissue of the individual patient.

[0003] For this purpose, it is known in the prior art to carry out so-called titration shots using a laser, i.e. to expose certain tissue sites of the retina to the laser beam under certain conditions in order to experimentally evaluate the effect of a laser treatment of a certain intensity on the tissue. The disadvantage of this method is that, on the one hand, several sites of the retina are exposed without sufficient prior information on the stress caused by the laser treatment, and, on the other hand, to evaluate such experiments, one must wait for the reaction of the tissue to the experimental laser treatment, which takes a certain amount of time. This takes only a few seconds for one titration shot, but to evaluate the reaction of the tissue to various laser intensities, it is common to carry out multiple titration shots, especially at different intensities. The effect of titration may also be evaluated with other examination methods, provided that they remain below the visibility threshold in the color image.

[0004] In one method known, for example from WO 2011 / 038935 A1, in conjunction with the titration shots for each site of the retina, images of the retina are captured by a camera, from which it is possible to detect discolouration of the tissue site hit by the laser. Furthermore, difference images of the camera images taken before and after titration are generated, whereby it is possible to extract the effect of the titration from the difference values. Summary of the Invention [Problem to be solved by the invention]

[0005] Against the background of the prior art, the present invention is based on the objective of creating a method and apparatus for determining irradiation parameters for the operation of a laser to irradiate one or more target areas of the retina of an eye, which method and apparatus make it possible to determine the irradiation parameters with minimal waste of time, minimal complexity and maximum reliability. [Means for solving the problem]

[0006] According to the invention, this object is solved by a method having the features of claim 1.

[0007] According to this, the present 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 an irradiation beam, in which all or a part of the retina is illuminated by an illumination device under defined illumination parameters, at least one optical recording (particularly at least one camera image) of at least one target area of ​​the retina is captured during and / or immediately after the illumination, and in which the recording or camera image is used to determine at least starting values ​​of the irradiation parameters for irradiating the one or more target areas of the retina.

[0008] The aim of the method is to enable the irradiation parameters for the operation of the laser to be determined as quickly as possible, automatically and reproducibly before the treatment. According to the prior art, it is often common to experimentally apply laser shots (titration shots) to different parts of the retina in order to determine the reaction of the tissue of an individual patient. The doctor then often assesses the degree of tissue discoloration as a result of the laser effect according to his personal impression and adjusts the laser parameters for irradiation in the actual treatment.

[0009] The method according to the invention makes it possible to completely dispense with or greatly reduce the trial operation of the laser before the treatment.By using real-time acquired tissue recordings or camera images, the assessment of the individual retinal tissue becomes objective, transparent, understandable, reproducible and verifiable.

[0010] According to the method of the present invention, it may be sufficient to finalize the irradiation parameters for the subsequent operation of the laser to irradiate the retina so that it is exposed to laser irradiation only for therapeutic purposes, and to experimentally determine the required laser intensity during the titration process.

[0011] The illumination device may be a visible light source, for example a light-emitting diode or a laser (e.g. the treatment laser itself), a surface illumination (e.g. by an illuminated reflective surface), a ground glass pane illuminated from behind, or a light-emitting diode matrix or another broadband light source. Illumination outside the visible range of the light spectrum, in the infrared or ultraviolet range, may also be considered. In this context, the prescribed illumination parameters may be understood to mean, for example, the luminous intensity and the wavelength or wavelength distribution of the emitted radiation. These may, for example, be set to specific values ​​or characteristics. The illumination parameters (e.g. illuminance, illumination intensity distribution and spectrum / wavelength distribution) may alternatively or additionally be measured, and the measurements may be used during the evaluation of the recording. It should also be noted that radiation in the non-visible range (e.g. in the infrared range) may also be used. The recording or camera image captured in this case is also an infrared image recorded with a corresponding detector. For example, hyperspectral sensors may also be used for these recordings. The selection of several areas of the retina (e.g. target areas) to be illuminated may be automatic or manual. During the automatic selection, a specific geometrical illumination pattern may be specified and selected. The method may also use a raster / scan method of illumination and scanning, for example, the target site or the entire retina is illuminated with a focused light source covering only a narrowly defined area, and reflections are detected by a light-sensitive, non-positionally resolved sensor (e.g., a photodiode). In this manner, entire areas of the retina may be optically scanned continuously, and an optical image of the reflectance and / or absorption intensity may be created. Conversely, the entire retina may be simultaneously illuminated, and light reflected from limited areas of the retina may be detected with a spatially resolved optical sensor, either in all areas of the retina or at the target site, thereby creating an optical image of the reflectance and / or absorption intensity of the retina.

[0012] In the context of the present invention, optical recording may be understood to mean, for example, an optical imaging recording of the retina.

[0013] As imaging methods for capturing retinal recording or camera images, methods such as fundus photography, fundus reflectometry, autofluorescence imaging, photoacoustic imaging, and functional optical coherence tomography with corresponding illumination devices and methods may also be used. These methods may be used, for example, to determine the pigmentation intensity of the retina, which determines the absorption intensity of the illumination beam to be used later. However, the pigmentation intensity can also be roughly determined from the retinal brightness recorded with the image or camera image.

[0014] In many cases, only certain individual or several target areas of the retina are treated with the laser beam. In this case, it may be sufficient to illuminate the target area and capture a recording or camera image of the target area. However, it may also be useful to capture a recording / camera image of the entire retina. This is because the required irradiation intensity of the laser during treatment can also be extrapolated in other areas of the retina that are not the treatment target, taking into account the pigmentation intensity. It is also possible to take into account other further non-local characteristics of the patient to be treated when determining the required radiation intensity. More information on this topic is provided below.

[0015] In one particular implementation of the above-described method, the pigmentation intensity of one or more target areas of the retina and / or the pigmentation intensity distribution on the retina can also be identified using recorded or camera images to determine starting values ​​for the illumination parameters.

[0016] It may also be realized that in order to determine starting values ​​of the irradiation parameters for one or more target areas of the retina, an additional correction value is determined for the expected and / or scattering of the treatment beam in the vitreous of the eye on the way to the target area to be irradiated, which correction value is determined in particular from the optical quality of the optical recording, more particularly from the image sharpness or the image contrast.

[0017] The sharpness or contrast of the image may be assessed based on the imaged inhomogeneities of the retina (e.g., blood vessels or ganglia). Sharpness / contrast information obtained from various parts of the retina may be compared to each other and / or to stored reference images in order to assess the effect of scattering / absorption within the vitreous of the eye on the sharpness of the image en route to the retinal site of interest and to determine this parameter roughly for the eye or even as a function of location on the retina.

[0018] For example, it may be advantageous to detect melanin pigmentation of the retina, and for this purpose it may be advantageous to illuminate the retina with light in the visible range having wavelengths, or even only wavelengths, that are particularly well absorbed by melanin pigmentation.

[0019] Illumination and / or detection wavelengths in the range of 450-1064 nm may be advantageous for the measurements. In other words, measurements at 514 nm, 532 nm or 577 nm may be advantageous in particular. In this region, scattering and absorption of radiation by melanin are strong. Furthermore, wavelengths at which the difference in absorption intensity between melanin and blood is significant may also be advantageous. It may be useful to compare recordings taken at a wavelength of 480 nm (local minimum absorption in blood) with recordings taken at 550 nm (local maximum absorption in blood). Reference values ​​for reflectance measurements may be, for example, the papilla, a ganglion (which shows a strong reflection in a healthy state) or a site with blood vessels, where the presence of oxygen-rich or oxygen-poor blood can be selectively detected, and using suitable wavelengths that can detect these different blood types, useful comparison values ​​can be generated.

[0020] During the subsequent laser treatment of the retina, the radiation beam is partially absorbed or scattered. This is due to the fact that the vitreous of the eye is not 100% transparent. This effect must be taken into account when determining the irradiation parameters of the laser, whereby the laser intensity is selected to compensate for it a little higher than the intensity directly required for the treatment of the retina. The absorption of the radiation beam depends on the individual properties of the vitreous of the patient to be treated. With the method according to the invention, it is possible to estimate the absorption, since the irradiance illuminating the retina is known and the intensity of the backscattered signal (e.g. reflected light) depends both on the pigmentation intensity of the retina and on the absorption of light in the vitreous. In order to be able to separate the two effects that influence the backscattering, it is possible to carry out several measurements under different optical conditions. This is explained in more detail below.

[0021] In many cases, it may be useful to illuminate the retina with radiation having a known wavelength distribution to generate a camera image, the radiation in particular including infrared radiation and / or light in a wavelength range absorbed by melanin, and further the luminous intensity of the illumination device and / or the total optical power incident on a unit area of ​​the retina and / or the optical power incident on a unit area of ​​the retina within a defined wavelength range is determined, and the brightness values ​​and / or color of the camera image are used to determine starting values ​​of the parameters for irradiating the retina.

[0022] By relating the experimental value of the required intensity of the irradiation beam to the already measured brightness value of the retina, it is possible to determine starting values ​​of the irradiation parameters for each individual case; for example, the absorption of the irradiation beam by the vitreous body may be represented by a constant assumed value (which may depend, for example, on the patient's age).

[0023] Further, advantageously, the retinal thickness may be identified for one or more target sites and taken into consideration when determining starting values ​​of the irradiation parameters, and the retinal thickness may be determined, in particular by creating an OCT thickness map of the retina, and / or the starting values ​​of the irradiation parameters may be determined using the type and intensity of pigmentation in various parts of the body other than the retina of the patient to be treated (in particular the type and intensity of pigmentation in the iris of the eye, or in the skin or hair).

[0024] OCT (Optical Coherence Tomography) measurements can be used to determine spatially-varying retinal thickness, for example to detect retinal edema, which often absorbs part of the laser radiation itself, preventing certain parts of the illumination beam from reaching the pigment layer. OCT thickness maps can therefore be used to determine spatially-varying correction variables for illumination parameters over the entire or partial extent of the retina.

[0025] In another implementation of the described method, it may also be realized that starting values ​​for the irradiation parameters are determined using one or more predefined or specifiable reference images or reference recordings in addition to the captured recording or camera image.

[0026] The reference record or reference image may, for example, represent the target state of the retina and may be compared with the captured image / camera image in order to perform a difference value analysis to determine the required irradiation intensity or the required irradiation parameters or their starting values ​​from the difference between the captured image and the reference image. The irradiation parameters that determine the treatment intensity or irradiation intensity may typically include the intensity of the laser beam (i.e. its energy) and the cross-sectional area of ​​the impact area / target site or the size of the laser beam spot, as well as the duration and number of emitted laser pulses and pauses between laser pulses. Finally, the reference record may, for example, be obtained from a database or from an already recorded record / camera image of the same patient.

[0027] In a further implementation of the above-mentioned method, it can also be realised that in order to determine the illumination parameters or at least the starting values ​​of the illumination parameters for one or more target areas of the retina to be illuminated, the pigmentation intensity of the target areas, on the one hand, and the expected absorption of the treatment beam in the eye lens on the way to the target areas, on the other hand, are determined independently of one another, by carrying out at least two measurements under various illumination conditions, in particular varying in said two or more measurements at least one of the following parameters: the size of the light focus on the retina (in each case the deviation from the expected light intensity distribution in the area of ​​the focus is measured), the direction of incidence of the illumination beam of the illumination device through the optic optic and the vitreous for the illumination of the respective target area, the direction of incidence on the target area and / or the direction of emission of the detected reflected illumination beam of the illumination device, the wavelength range or wavelength distribution of the illumination beam of the illumination device.

[0028] This method allows to determine the distribution of pigmentation intensity on the retina on the one hand, and the absorption of the laser beam by the vitreous body as a function of the laser target point on the retina and the light path on the other hand, independently of each other. In the case of such measurements, for example, the light path for illuminating the target area of ​​the retina may be changed for various successive individual measurements, but the same target area may be illuminated and recorded in each case. On the other hand, the target area of ​​the retina may be illuminated by the illumination device in different ways in several measurements, while keeping the same light path, so that the influence of the reflectance of the retina can be changed by illumination of different spectra or by light of different wavelength ranges.

[0029] Alternatively or additionally, it may also be realised that, in order to determine irradiation parameters for one or more target areas of the retina to be irradiated, the pigmentation intensity of the target area and / or the expected absorption of the treatment beam in the crystalline lens of the eye on the way to the target area is determined on the one hand by carrying out at least two measurements, one of which is directed to the absorption and / or reflection properties of the optic disc and / or at least one blood vessel or a sub-area of ​​a blood vessel in the retina, the other of which is directed to the absorption and / or reflection properties of the optic disc and / or at least one blood vessel or a sub-area of ​​a blood vessel in the retina, and a second measurement is directed to the absorption and / or reflection properties of any other areas of the retina to be irradiated.

[0030] The described method may also realize that in order to determine illumination parameters for one or more target areas of the retina to be illuminated, at least two locations of the retina are respectively illuminated successively or simultaneously with different illumination characteristics (specifically different illumination intensities), the intensity of the reflected signal is recorded in each case, a functional relationship between the illumination characteristic (specifically illuminance) and the intensity of the reflected signal is determined in each case for the locations thus measured, the inclination angle of the functional curve is determined by comparing the functional relationship (specifically the inclination angle of the functional curve in the case of a linear relationship) at each measurement location, and a reflectance ratio is determined for each measurement location by comparing the functional relationship (specifically the inclination angle of the functional curve) at each measurement location, in particular one of the locations being on the surface of the optic disc or a blood vessel or at least a part of one of the locations containing a blood vessel.

[0031] The optic nerve head (optic optic disk) is normally unpigmented and reflects light much more strongly than the pigmented parts of the retina. Moreover, the reflectance of the optic disk depends only to a small extent on the retinal characteristics of an individual patient. Thus, the optic disk can serve as a "reflection standard" or standard against which to compare and measure the intensity of pigmentation.

[0032] Retinal veins can also be detected and used for comparative measurements in the areas of the retina defined by the veins. Passing blood has somewhat different absorption properties than melanin.

[0033] The absorption also depends on whether the blood is saturated with oxygen or not, i.e. on which type of blood vessel is used. In order to be able to measure and evaluate these properties of absorption and reflectance of blood vessels in a differentiated way, it may be useful to carry out the measurement of reflectance or absorption at a wavelength of illumination light that is particularly strongly influenced by oxygen-saturated light or deoxygenated blood. As an alternative to a corresponding selection of the illumination light, a corresponding effective wavelength may be selected on the detection side.

[0034] It has been found that the functional relationship between the illumination characteristics (specifically illuminance) on the one hand and the intensity of the reflected radiation on the other hand at a location on the retina allows a good determination of a value representative of the reflectance of the retina at this location. If the relationship between illuminance and reflected radiation is linear, a linear regression method may be used, whereby it is possible to determine the slope of the lines forming a functional graph for several measured values, for example to compensate for measurement errors. The inclination angles of these lines may then be assigned to each measurement location on the retina and form a relative measure of the reflectance. The reflectance values ​​assigned to these measurement locations may then be calibrated by comparison with the corresponding correlations (specifically the slopes of the lines) at locations where the reflectance is known or can be well estimated. The reflectance at a location on the retina may then be used to determine the absorption strength for the illuminating beam.

[0035] The wavelength of the radiation illuminating each measurement location can also act as a variable illumination characteristic, whereby two locations are alternately illuminated with radiation of different wavelengths, the intensity of the reflected radiation is measured in each case, and a functional relationship is determined and compared for the two locations.

[0036] Differentiation of reflectance at different wavelengths can be achieved by sequential illumination at different wavelengths with simultaneous broadband detection (or detection adapted by wavelength windows), or by broadband illumination covering a continuous spectrum, or by illumination with a laser array containing multiple individual wavelengths. In the latter case of broadband excitation / illumination, wavelength-selective detection of the reflected radiation is performed, for example, using wavelength-selective filters or by defining color channels using a spectrometer or a multispectral camera.

[0037] Since the reflectance of the optic disc area varies only slightly, any deviations of the identified characteristics in the first step and the reflectance values ​​determined therefrom from the reference values ​​are likely due to the effects of absorption and / or scattering of radiation on the measurement path through the eye of each individual patient.

[0038] Thus, the deviation of a measurement from a reference value of reflectance at a reference location, such as the optic disc or blood vessels, can be used to characterize attenuation due to absorption and / or scattering within the body of the eye.

[0039] By taking several measurements at different locations on the retina, the influence of pigmentation on the captured recording or the captured camera image, on the one hand, and the influence of vitreous absorption on the other hand, can be determined independently of one another in the evaluation and taken into account when determining the illumination parameters. It should also be noted that the incidence direction and the emission direction of the illumination beam also refer to the optical path that the laser beam travels through the vitreous.

[0040] The type of linking between the illumination parameters and the detected variables / signals of the respective captured recording or the respective captured camera image on the one hand, and the irradiation parameters for the operation of the laser on the other hand, can take various forms. It can be a mapping table in the simplest case, which can exist as a multidimensional matrix and can be stored, for example, in a computer or in a non-local or distributed data processing system. The linking 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.

[0041] Against this background, the present invention may also relate to a method for training an algorithm or neural network for determining starting values ​​of irradiation parameters according to the above-mentioned method, in which a data set of the target area to be irradiated determined from images for a number of individual treatments, and the associated illumination parameters, and (in particular) secondary information additionally obtained in each case as input information, and (on the other hand) the irradiation parameters set as result variables during each subsequent laser treatment are linked together as training data.

[0042] Training data may be initially obtained, for example, by parallel operation of conventional methods and the methods described herein, where recordings or camera images are captured under defined lighting conditions as described above, and the required treatment intensity, i.e., the intensity of the treatment laser beam (e.g., expressed as laser power, pulse duration, number of pulses, and repetition rate), is determined in a conventional manner using a titration method, which may then be linked with previously recorded recordings / camera images of the target area of ​​the retina to be treated, whereby the learning system is trained on this data.

[0043] The individual treatments used to train the algorithm may be performed according to the method of the invention described above, whereby the starting values ​​of the irradiation parameters are first determined, then the treatment is started, the success of the treatment is assessed by checking the discolouration of the target area, and, if necessary, the irradiation parameters are corrected. The algorithm can be further trained and improved by inputting correction values ​​or by linking correction values ​​to the originally determined starting values ​​for the irradiance parameters and the irradiation parameters.

[0044] Additional secondary information may be input as variables that prove to have a significant influence on determining the irradiation parameters. Such secondary information may be, for example, the patient's age and some parameters of the patient's health condition, as well as specific parameters of the patient's retina to be treated. For example, the measured integral pigmentation intensity of the skin or iris of the eye, or the measured pigmentation intensity of the patient's hair, eyebrows or skin, as well as the color of the skin pigmentation, the color of the iris, and the color of the hair may be taken into account.

[0045] When determining the starting values ​​of the irradiation parameters for all target sites, it is also possible to perform calibration, for example, with one or more of the following calibration parameters of the patient to be treated: the measured integral pigmentation intensity of the skin, the measured integral pigmentation intensity of the iris of the eye, the measured pigmentation intensity of the hair (hair, eyebrows), the skin pigmentation color, the iris color, and the hair color. Such calibration can also achieve, for example: the listed variables are not included in the algorithm for determining the irradiation parameters, but after the determination of the irradiation intensity, the result is calibrated with the specified variables, for example, by multiplying the irradiation intensity given by the laser energy and the length of the laser pulse by a certain calibration factor.

[0046] The present invention may also relate to a method for determining irradiation parameters for operation of a laser for irradiating one or more target areas of a retina of an eye with an irradiation beam, in which a starting value of the irradiation parameter is first determined according to the above-described method, then at least one target area is irradiated with a titration beam or irradiation beam according to the starting parameters, then at least one continuous recording or continuous camera image of the target area of ​​the retina irradiated with the treatment beam is obtained, and using the continuous recording and / or continuous camera images and the starting value of the irradiation parameter, at least continuous values ​​of the irradiation parameter for irradiating the one or more target areas of the retina are determined.

[0047] In this way, it is possible to check the initially determined starting values ​​of the irradiation parameters as soon as possible after their application whether success has been achieved and, if necessary, to adjust them or to determine successive irradiation parameters therefrom. The corresponding corrections can also be used, for example, to provide the algorithm with further training data to improve it.

[0048] Finally, in addition to the above-mentioned method, the present invention also relates to an apparatus for irradiating one or more target areas of the retina of an eye with an irradiation beam, the apparatus comprising a laser for generating an irradiation beam, an illumination device for illuminating at least one or more target areas of the retina with prescribed illumination parameters, an optical recording device (specifically a camera) for capturing at least one recording or image of the at least one target area of ​​the retina, and a processing device configured to use the illumination parameters and the optical recording or camera image to determine at least initial values ​​of the irradiation parameters for irradiating the one or more target areas of the retina with the irradiation beam.

[0049] This device can be used to carry out various implementations of the above-mentioned method. The processing device can be designed as a data processing device that includes an algorithm that assigns starting values ​​of the illumination parameters to the lighting parameters and to the variables recorded by the recording or camera images. This algorithm can be modified or trained by training data as part of a learning system with artificial intelligence, as described above. The processing device can also include a neural network that can learn in the described manner, for example by forming its links through a training process.

[0050] The above-mentioned device may be completely independent of the treatment device, for example with a treatment laser, or may be connected to or integrated in the treatment device. For example, the device according to the invention may be partially centralized, in which case the processing device may be located non-locally in a server or another type of remote data processing system, receiving the determined data by a suitable communication method. In this way, the processing device may be fed with measurement data from many different locations, trained thereby, and remotely control a local treatment device. In this way, optimal training of the processing device with real data from one or more patients may be ensured.

[0051] The invention will now be illustrated in the embodiments described below with reference to the drawings, in which: [Brief description of the drawings]

[0052] [Figure 1] 1 shows an ophthalmoscope having a device for illuminating the retina of the eye. [Diagram 2] 4 shows a flow chart of a method for determining starting values ​​of irradiation parameters. [Diagram 3] 4 shows images of the retinal target area. [Figure 4] 1 shows a close-up of the path of light through the vitreous of the eye to the retina. [Diagram 5]1 shows an example of illumination parameters, measurements representing recordings of retinal target areas, and assigned starting values ​​for the illumination parameters. [Figure 6] 4 shows a second flow chart of the method, in which starting values ​​of the exposure parameters are first determined and then checked. [Figure 7] A third flow chart is shown, which illustrates a method for training an algorithm that is improved in a self-learning process and assigns starting values ​​of illumination parameters to illumination parameters and other correction variables. [Figure 8] 1 illustrates a schematic diagram of linking input and output variables to train an algorithm. [Figure 9] ~ [Figure 11] 1 shows the functional relationship between illuminance and reflected radiation intensity for three different cases, relative to the retinal papilla / optic nerve and at another location. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] FIG. 1 shows a device according to the invention or a device for implementing the method according to the invention in the form of an ophthalmoscope or a device combining the functions of ophthalmoscope and of retinal laser therapy.

[0054] The apparatus comprises an illumination device 5 with a radiation source 5', which is arranged to direct an illumination beam 14 towards the patient's eye 4 and retina 16, whereby the retina 16 can be suitably illuminated for recording or camera images to be captured. The illumination device may for example comprise a light emitting diode or an infrared diode as a light source, or may comprise another type of light source providing a defined wavelength spectrum. The light source may for example be a UV light source.

[0055] The ophthalmoscope also comprises a camera 6 with a sensor 7. This sensor may for example be a CCD or CMOS sensor. Instead of the camera 6, any other type of device suitable for detecting radiation reflected or scattered from the retina may also be provided, for example a scanning device.

[0056] The purpose of operating the illumination device 5 and camera 6 (or equivalent device) is to obtain the most accurate spatially resolved measurement data possible from the retina 16 under defined lighting conditions by recording images of reflected radiation, thereby recording or identifying the characteristics of the target area to be treated.

[0057] The illumination beam 14 and the reflected radiation 15 are suitably collimated or focused by a suitable optical system 13 with mirrors and lenses in a manner known per se. The optical system 13 also comprises a beam splitter 12, which allows the laser beam from the treatment laser 2 to be directed onto the retina 16. Alternatively, the laser beams may be combined without a beam splitter, for example by guiding the laser beam to be slightly offset laterally with respect to the illumination light. A control unit 8 for controlling the laser 2 may be provided, which on the one hand controls the illumination device 5 (for example by triggering it) and on the other hand captures camera images from the camera 6 and directly controls the laser 2. The control unit 8 may also control a deflection mirror 3, which directs the beam path of the illumination beam 11 so that treatment of individual target sites on the retina 16 is possible.

[0058] For improved control of the laser 2, a processing device 19 according to the invention may be provided, which allows accurate processing of the recording / camera images from the camera 6 and links these with known or defined parameters of the illumination of the retina 16.

[0059] For example, the ophthalmoscope also comprises a sensor 100 (eg in the form of a camera) which allows the measurement of the colour and intensity of pigmentation of the patient's skin, hair and / or iris.

[0060] An input device may also be provided by which such parameters can be entered. In any case, these parameters are passed to the processing unit 19 where they are taken into account when determining starting values ​​for the exposure parameters.

[0061] In the past, the intensity of the laser treatment, i.e. the intensity and / or duration of the laser pulse when the laser 2 was activated, was performed by the operator according to his own assessment after evaluation of the retinal recordings: first titrating pulses were directed onto the retina and adjustments of the laser intensity were made by assessing their effect.

[0062] By illuminating the retina with known illumination parameters and linking these parameters with the retinal recordings, it is possible to assign, in an objective manner by the laser treatment processing device 19, for each target site on the retina, a laser treatment intensity to these partially specified and partially measured values ​​for each target site on the retina, the intensity being given by the energy of the laser, the size and number of the laser spots on the retina, the repetition rate and duration of one or more pulses, and the length of the pauses between the pulses. The method according to the invention makes it possible to determine at least the starting value of such irradiation by the irradiation beam 11, and thereby to perform a treatment of the retina.

[0063] 2 shows a flow chart of the method according to the invention, in which a first step 20 is to specify the lighting parameters of the lighting device 5. However, the lighting parameters may already be present and specified in the lighting device. Alternatively, the individual lighting parameters can be specified, for example, by the processing device 19 and sent to the lighting device 5. Lighting parameters such as illuminance, lighting intensity distribution and spectrum / wavelength distribution may be measured and the measured values ​​used in the evaluation.

[0064] Then in a second step 21, the illumination device 5 or light source 5' is operated to illuminate the retina continuously or in a pulsed manner. At the same time, the reflected radiation may be recorded by the camera 6 in a further step 22. Step 22 may be performed simultaneously with the illumination step 21 or with a time delay relative to the illumination step. The latter is the case, for example, when recording fluorescent radiation that is known to be emitted after the excitation radiation.

[0065] In step 23, the illumination parameters and the measured values ​​recorded by the camera are then linked together in the processing device 19 by an assignment function (e.g. an assignment algorithm) which determines from these variables the starting values ​​of the irradiation parameters, which are converted into irradiation by the action of the laser 2. Only after the determination of the starting values ​​can the subsequent step, treatment step 24, be started. Step 24, the actual treatment, is separated in the figure by a dashed line 25 from the step of determining the starting values ​​of the irradiation parameters.

[0066] FIG. 3 shows a schematic image of the retina 16 of the eye with various target sites. A target site 28 is shown at the edge of the retina, which is less important in terms of the actual visual function of the eye than the target sites 25, 26, 27 in the center of the retina 16. The individual target sites are shaded differently to represent different pigmentation intensities or other variable parameters of the individual target sites. It will be apparent that different target sites for treatment with the laser 2 will require different irradiation parameters. The target sites 25, 26, 27, 28 may vary in size and may be small enough to allow spatially resolved treatment with the laser 2. FIGS. 3 and 4 also show the optic 40. This area remains untreated and may serve as a reflectance reference to be compared with melanin-containing areas of the retina.

[0067] FIG. 4 shows a cross section of the vitreous body of the eye 4 together with the lens 29 and the retina 16. A point or target area 32 is shown on the retina, which may alternatively be clearly illuminated with two different illumination beams 30, 31. Depending on where the illumination beams 30, 31 enter the lens of the eye, the light beams follow different paths through the lens and the vitreous body to the point 32. By comparing the measurements of the reflected light recorded by the camera 6 in terms of intensity, it is possible to record in a differentiated manner the scattering or attenuation of light on the various light paths through the vitreous body. By varying the illumination beam, it is possible to gradually measure the entire vitreous body of the eye 4, so that the influence of the vitreous body by attenuation and scattering on the illumination and illumination beams of the retina can be investigated over all areas of the eye.

[0068] Alternatively, it is also possible to allow two different illumination beams 30 to reach a point 32 on the retina 16 through the same optical path, but with varying wavelengths of illumination light, so that for example both beams can use the same optical path through the vitreous body, but for example in one case a wavelength corresponding to the optimal absorption wavelength of melanin on the retina is selected, and in another case a different wavelength is selected. This makes it possible to measure in a first approximation the pigmentation by melanin on the retina, independent of the inhomogeneity of the vitreous body of the eye, if the wavelength-dependent attenuation of the vitreous body is ignored in a first step. Alternatively, the illumination beam may have a broad spectrum and may include several wavelength ranges simultaneously. In this case, the sensor can differentiate over a wide wavelength range (even beyond the optically visible range) by wavelength-selective evaluation. For example, a hyperspectral sensor can be used for this purpose. Bayer filters can also be used for imaging the retina.

[0069] It is then possible to carry out a combined measurement varying both the optical path and the wavelength, thereby determining the wavelength-dependent attenuation value of the vitreous as a function of position. Thus, knowing the parameters of the light source 5', it is possible to take into account the attenuation of both the incident light or radiation on the retina and the influence of the optical path on the backscattered radiation, thereby making it possible to objectively determine, for example, the intensity of melanin pigmentation on the retina.

[0070] FIG. 5 shows a schematic structure of linking the lighting parameters, the measurements of the recording / camera images and the starting values ​​of the exposure parameters. The lighting parameters 33 are x 1 ~x n where the individual parameters represent, for example, the irradiance level in each case of a particular target site, i.e. the radiant energy or radiant power emitted from the illumination source, or alternatively the distribution of power over the individual wavelength ranges of the emitted radiation, i.e. the shape of the wavelength spectrum with the corresponding intensity. 35 represents a mapping or linking function, which may be designed, for example, as a self-learning algorithm.

[0071] 34 is a parameter y of the measurement captured by camera 6 for a particular target site. 1 ~y m If these are linked to lighting parameters, this gives the starting values ​​of the n-tuples of illumination parameters 36, which are z 1 ~z o and represents, for example, 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 to one or more target sites.

[0072] One goal of the present invention is to determine optimized starting values ​​of the irradiation parameters for each target site. This result is first achieved by determining these starting values, which is indicated in FIG. 5 by the dashed dividing line 25. The actual laser operation of the laser 2 and the treatment of the retina therewith can then be performed, and then the effect of the laser treatment on the retina can be carried out by repeating the process already described, i.e. illuminating the retina with the defined parameters and examining the camera images or recordings. The result of the re-recorded camera images can be compared with the initially recorded camera images, and differences can be identified that indicate the effect of the treatment with the laser 2. If the effect of the laser during the treatment does not correspond to the goal of the treatment, the algorithm 35 can be corrected or trained, and a new set of irradiation parameters can be determined from the illumination parameters during the second illumination and the measurement data recorded together with the second camera images.

[0073] Figure 6 first shows the sequence of process steps 20-24 as shown in Figure 2, then following the treatment step 24 there is a further step 21' of illuminating the retina with defined illumination parameters, simultaneously or offset with the recording of a camera image in step 22', then in a further step 23' the illumination parameters and the measurement data recorded together with the camera image are combined to form new exposure parameters.

[0074] FIG. 7 shows a flowchart in which the structure of the flowchart of FIG. 6 is repeated, with a renewed linking step 23′ followed by a further laser treatment step 24′, in which the illumination parameters and the camera measurement data are taken into account after the first laser effect step 24. Furthermore, 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 implemented in process steps 23 and 23′. This feedback from the correction variables can be used to continuously improve the linking algorithm on which the link between the illumination parameters, the camera measurement data and the starting values ​​of the irradiation parameters is based. For this purpose, the treatment of the same individual or the treatment of a group of individuals (e.g. with a similar clinical picture) may be taken into account for the algorithm improvement. For this purpose, the algorithm may be stored centrally (e.g. on a server or in the cloud) and retrieved for each individual treatment, with the correction variables being fed back to the server or the cloud. This is to make it possible to train the algorithm using as much training data as possible from different treatment processes at different locations.

[0075] 7 also shows that in a further process step 37, additional parameters are measured for the individual patient or the eye or retina of the individual patient, which are fed to the linking step 23 for calibration. For this purpose, in step 37, for example, integral quantities of the retina (e.g. the average pigmentation, or the intensity of the iris shade of the eye, or the color of the iris, or the intensity of the individual's skin pigmentation, or the color of the skin pigmentation, and / or the color and intensity of the individual's hair pigmentation) may be measured by a sensor (in particular a camera) and fed to the linking step 23. The influence of these variables may be taken into account during the training of the allocation algorithm and may be fed as calibration parameters during the individual treatments.

[0076] FIG. 8 shows the corrected illumination parameters 36′ in relation to the original illumination parameters x 1 ~x nand the measurement data y measured by the camera image 1 ~y m 3 shows the development of the assignment algorithms A, A' by linking the input parameters z 1 '~z o ', which are interpreted as optimized result data to refine the algorithm.

[0077] This method optimizes the linking algorithm after a required number of training runs, thereby also optimizing the starting values ​​of the exposure parameters in the first step.

[0078] Figures 9, 10, and 11 show the functional relationship between illuminance and reflected radiance in three different cases for the papilla / optic nerve and another location on the retina. In each case, the graph representing the papilla is labeled "50" and in each case the graph representing the location in the treatment target area is labeled "51."

[0079] In principle, the method for determining the absorption intensity allows to draw direct conclusions about the pigmentation intensity of the retina and involves illuminating with several different irradiances locations different from the target site, which are in the region of the optic disc, or on the blood vessels or on the blood vessels, or on another special location on the retina, and simultaneously measuring the reflected radiation intensity. The functional relationship between the irradiance and the reflected radiation intensity is linear, resulting in an approximately straight line. At least, as shown in figures 9, 10 and 11, a straight line is obtained by using linear regression through the measurement points. The same procedure is carried out for one or more locations in the target site of the retina that will be treated later by radiation. The slope of the determined line represents the reflectance at the various locations. The reflectance in the region of the blood vessels and the reflectance of the optic disc can be well estimated and are almost independent of other conditions of the individual retina, so that the values ​​determined there can be used to calibrate the measurements of the reflectance values ​​at other locations. For this reason, it is also possible to use measurements of the reflected radiation intensity in the region of the optic disc or blood vessels to estimate the scattering and absorption losses of the radiation on its way to the respective location (optic disc or blood vessel or another location with known reflectance) and on its way back to the sensor that measures the reflected radiation intensity after reflection. These scattering and absorption values ​​may then be assumed for the illumination of other regions of the retina as well, since they characterize the light path through the vitreous of the eye.

[0080] In detail, FIG. 9 shows an example where the reflectance and absorption intensity of the macular region correspond to the standard case.

[0081] FIG. 10 shows a case where the slope of the line representing the macula is lower and therefore the reflectance measured relative to the slope of the second line representing the papilla is lower and therefore the absorption intensity and pigmentation intensity are higher than in the normal case.

[0082] FIG. 11 shows a case in which the inclination angle of the line representing the macula is greater than the inclination angle of the line representing the papilla in the case shown in FIGS. 9 and 10. This measurement therefore represents a case in which the reflectance of the macula is greater and, accordingly, the absorption intensity and pigmentation are less. Since the inclination angle of the line 50 representing the measurement at the papilla is significantly smaller than that of the graphs in FIGS. 9 and 10, it can be concluded that, if the reflectance of the papilla is the same as in the cases in FIGS. 9 and 10, the absorption and / or scattering of the eye body is significantly stronger in the case shown in FIG. 11. From the difference in the inclination angles of the lines 50 in FIGS. 9, 10 and 11, it is possible to calculate an attenuation coefficient, which represents the scattering and absorption in the case of the eye measured according to FIG. 11 and which may be taken into account in the irradiation during treatment.

Claims

1. A method for determining irradiation parameters for the operation of a laser (2) for irradiating one or more target areas of a retina (16) of an eye (4) with an irradiation beam (11), the method comprising: illuminating all or a part of the retina by an illumination device (5, 5') under defined illumination parameters; capturing at least one optical recording (specifically at least one camera image) of at least one target area of ​​the retina during and / or immediately after said illumination; and using said recording or camera image, determining at least starting values ​​of the irradiation parameters for irradiation of one or more target areas of the retina.

2. 2. The method of claim 1, characterized in that to determine the starting value of the irradiation parameter, the pigmentation intensity of one or more target areas of the retina and / or the pigmentation intensity distribution on the retina are identified using the recordings or the camera images.

3. 3. The method according to claim 1 or 2, characterized in that in order to determine the starting values ​​of the irradiation parameters for one or more target sites of the retina, correction values ​​are determined for the expected and / or scattering of the treatment beam in the vitreous of the eye on the way to the target sites to be irradiated, the correction values ​​being determined in particular from the optical quality of the optical recording, more in particular from image sharpness or image contrast.

4. 4. A 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, the radiation in particular comprising infrared radiation and / or light in a wavelength range absorbed by melanin, the luminous intensity of the illumination device and / or the total light power impinging on a unit area of ​​the retina and / or the light power impinging on a unit area of ​​the retina are additionally determined within a defined wavelength range, and the brightness values ​​and / or the color of the camera image are used to determine the starting values ​​of the parameters for the illumination of the retina.

5. The method according to claim 1, 2, 3 or 4, characterized in that the thickness of the retina is identified for one or more target sites and taken into account when determining the starting values ​​of the irradiation parameters, and the thickness of the retina is determined, in particular by creating an OCT thickness map of the retina, and / or the starting values ​​of the irradiation parameters are determined using the type and intensity of pigmentation of various sites of the patient's body other than the retina 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.

6. The method according to any one of claims 1 to 5, characterized in that in addition to the captured image or camera image, one or more predefined or specifiable reference records or reference images are used to determine the starting values ​​of the irradiation parameters.

7. 7. The method according to claim 1 , characterized in that, to determine the illumination parameters for one or more target sites of the retina to be illuminated, the intensity of pigmentation of the target sites on the one hand and the expected absorption of the treatment beam in the lens of the eye on the way to the target sites on the other hand are determined independently of one another, by carrying out at least two measurements under various illumination conditions, in particular varying in the two or more measurements at least one of the following parameters: the size of the light focus on the retina (whereby in each case a deviation from the expected light intensity distribution in the area of ​​the focus is measured), the direction of incidence of the illumination beam of the illumination device through the optic disc and the vitreous body for the illumination of the respective target site, the direction of incidence on the target site and / or the direction of emission of the detected reflected illumination beam of the illumination device, the wavelength range or wavelength distribution of the illumination beam of the illumination device.

8. 8. The method according to claim 1, characterized in that, to determine the irradiation parameters for one or more target areas of the retina to be irradiated, the pigmentation intensity of the target areas and / or the expected absorption of the treatment beam in the lens of the eye on the way to the target areas is determined by carrying out at least two measurements, one of which is directed to the absorption and / or reflection properties of the optic disc and / or at least one blood vessel or a part of a blood vessel area in the retina, and a second measurement is directed to the absorption and / or reflection properties of any other areas of the retina to be irradiated.

9. 9. A method according to any one of claims 1 to 8, characterized in that, in order to determine the illumination parameters for one or more target areas of the retina to be illuminated, at least two locations of the retina are in each case illuminated, successively or simultaneously, with different illumination characteristics (in particular different illumination intensities) and in each case the intensity of the reflected signal is recorded, and for the locations thus measured, in each case a functional relationship between the illumination characteristic (in particular the illuminance) and the intensity of the reflected signal (in particular the slope of the function curve in the case of a linear relationship) is determined, and by comparing the functional relationship (in particular the slope of the function curve) at the measurement locations a reflectance ratio is determined, in particular one of the locations being on the surface of the optic disc or a blood vessel or at least a part of one of the locations containing a blood vessel.

10. A method for training an algorithm or a neural network for determining the starting values ​​of irradiation parameters according to any one of claims 1 to 9, characterized in that for a number of individual treatments, a data set of the target area to be irradiated, determined from an image, and the associated illumination parameters, and (in particular) secondary information additionally obtained in each case as input information, and (on the other hand) the irradiation parameters set as result variables during each subsequent laser treatment are linked together as training data.

11. 11. Method according to any one of claims 1 to 10, characterized in that when determining the starting parameters for all target sites, a calibration is carried out in each case with one or more of the following calibration parameters of the patient to be treated: the measured integral pigmentation intensity of the skin, the measured integral pigmentation intensity of the iris of the eye, the measured pigmentation intensity of the hair, the skin pigmentation colour, the iris colour and the hair colour.

12. A method for determining irradiation parameters for operation of a laser for irradiating one or more target areas of a retina of an eye with a treatment beam, comprising: determining an initial starting value of the irradiation parameter according to the method of any one of claims 1 to 11; then irradiating at least one target area with a titration beam or treatment beam with the starting parameters; then obtaining at least one continuous recording or continuous camera image of the target area of ​​the retina irradiated with the treatment beam; and using the continuous recording or continuous camera images and the starting value of the irradiation parameter to determine at least continuous values ​​of the irradiation parameter for the irradiation of one or more target areas of the retina.

13. An apparatus for irradiating one or more target areas of a retina of an eye with a treatment beam, the apparatus comprising: a laser for generating the treatment beam; an illumination device for illuminating at least one or more target areas of the retina with prescribed illumination parameters; an optical recording device (specifically a camera) for capturing at least one optical recording or image of the at least one target area of ​​the retina; and a processing device configured to use the illumination parameters and the recording or camera image to determine at least initial values ​​of the irradiation parameters for irradiating the one or more target areas of the retina with the treatment beam.

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