Method and assembly for refocusing an ophthalmic system for intraocular laser treatment - Patents.com

Abstract

The present invention relates to a solution for refocusing an ophthalmic laser therapy system, which, in addition to a treatment laser unit, an imaging unit, and an optical system for focusing and beam overlapping, also has an OCDR system and a control unit. According to the present invention, a target laser beam of the laser therapy system is focused on at least one target structure ZS1 in the treated eye by changing a distance A between the laser therapy system and the eye until it is detected that the target laser beam of the laser therapy system is focused on the target structure ZS1. Each focus position PF to be adopted of the laser beam of the laser therapy system in the OCDR signal profile is approximately estimated using parameters A1 and PZS1 for any number of selected values ​​of the change in distance ΔA between the laser therapy system and the eye based on the distance A1 of the position of the selected reference structure PRS relative to the reference plane RE and the position of the target structure PZS1 in the OCDR signal profile.

Description

[Technical field]

[0001] The present invention relates to a method and device for refocusing an ophthalmic laser treatment system, which, in addition to a treatment laser unit, an imaging unit, and an optical system for focusing and beam overlapping, also comprises an OCDR system and a control unit.In this context, OCDR is understood to mean one-dimensional OCT, i.e., OCT that can record A-scans (depth profiles).The imaging system can be configured as a camera-based system or as an observation unit ("laser slit lamp") for the operator's eye. [Background technology]

[0002] According to the known prior art, numerous solutions already exist for the surgical, ablative, thermal or other therapeutic laser treatment of ocular tissues, in particular the cornea, sclera, trabecular meshwork, retina, crystalline lens (Lens) or vitreous humor.

[0003] Regardless of the type of treatment, i.e. the tissue to be treated, it is particularly important to observe the appropriate rules during the use of the laser in order to avoid damage to the eye. In addition to the laser power and the overall beam irradiation, in this situation it is particularly important to align the focus of the treatment laser as accurately as possible with the tissue to be treated, since deviations may result in damage to adjacent tissues of the eye or the desired therapeutic effect may not be obtained on the tissue to be treated. This is explained in more detail as an example based on the treatment of the vitreous humor of the eye.

[0004] The vitreous humor usually consists of a clear gel-like substance inside the eye between the lens and the retina. In young people, the vitreous humor is mostly clear and in contact with the retina. Throughout life, the vitreous humor liquefies and gradually detaches from the retina, which is called posterior vitreous detachment. This is a normal aging process that usually occurs after the age of 50. The vitreous humor components may continuously break down inside the eye, and the skeletal material and density of the vitreous humor become increasingly visible in the patient's eye. They are also called "floaters" because they may move across the field of vision. In many cases, the cause of vitreous opacity is the presence of membranous structures behind the vitreous humor after vitreous detachment, and even blood residues if retinal damage occurs during vitreous detachment. In rare cases, when there is a metabolic problem, the vitreous opacity may also be present as crystalline precipitates in the vitreous humor.

[0005] Even if vitreous opacity does not usually have a pathological cause, it is not as harmless as it is generally thought, since it can sometimes very significantly impair the quality of life and work productivity of the affected person. This opacity is especially perceived against a light background, for example, when working at a computer, reading, or looking at blue sky or snow, and interferes with vision. Vitreous opacity that jumps in and out of the central visual field as a result of reading movements when reading is particularly bothersome.

[0006] They are often shaped like "flying mosquitoes" and are therefore referred to using the technical term "Mouches-Volantes", which comes from the French. However, the opacities may have different shapes, for example branches, rings, stars, or may be present as a cloud of points. In the following text, the term "vitreous opacities" is used for the vitreous opacities to be treated, regardless of their type or morphology.

[0007] Generally, vitreous opacity does not disappear without treatment, as the immune system does not recognize it as abnormal and therefore does not destroy it. However, the affected party can hardly ignore or overlook it. Certain types of vitreous opacity, such as those caused by residual blood after retinal hemorrhage, are partially absorbed again by the body, even if it takes weeks or months.

[0008] In what is known as vitrectomy, after opening the eye using a cutting instrument, the vitreous fluid is crushed, aspirated and removed, either partially (core vitrectomy) or completely. Such interventions are routinely performed in cases of retinal detachment or epiretinal membrane detachment, but are usually considered a disproportionate treatment to remove localized vitreous opacities. Moreover, vitrectomy is invasive, requires a stay in the clinic and is subject to the risks associated with surgical interventions, in particular, the risk of frequently causing cataracts, rarely retinal detachment and very rarely endophthalmitis.

[0009] So-called laser vitreolysis is now being offered as a low-risk alternative treatment: it is a conservative, low-risk and painless laser treatment that can vaporize or atomize vitreous opacities without making an incision in the eye.

[0010] In the case of laser vitreolysis, short laser light pulses are directed at the vitreous opacity in order to obtain optical or photodisruption there by means of high laser intensity in the focal area. The vitreous opacity and the vitreous humor surrounding it absorb the laser energy, forming a laser plasma that cuts or expands, so that the floaters can be evaporated and / or shattered and consequently dissolved. This treatment causes little pain and has no risk of infection. Laser vitreolysis offers a safe method for the sparing treatment of troublesome vitreous opacities, provided it is possible to ensure that important and sensitive ocular structures, such as the lens capsule, the lens or the retinal area, especially the macula, are not damaged by the laser.

[0011] For this purpose in particular, it is important to be able to focus the therapeutic laser as accurately as possible on the vitreous opacity to be treated, and to avoid inaccurate alignment of the therapeutic laser focus with adjacent, possibly sensitive, ocular structures, such as the lens capsule, the optic nerve head, the macula, etc. Also, since the vitreous opacity to be treated and the ocular structures to be preserved are generally located at different depths within the eye, alignment of the axial therapeutic laser focus is particularly important in this situation.

[0012] However, the success of the treatment depends on the type of vitreous opacity. This treatment is particularly successful in the case of so-called Weiss rings. The tissue bundles can be cut and the tissue concentration causing the disturbing shadow can be eradicated.

[0013] Vitreous opacities have been treated with YAG lasers (especially Nd:YAG at 1064 nm) for more than 30 years already (Non-Patent Document 1). However, even when current high-end devices are used, only the most anterior area of ​​the vitreous humor can be treated with precise and reliable targeting. These lasers are not precise enough in the deeper vitreous humor areas. However, most vitreous opacities are found there, as they are often the result of posterior vitreous humor detachment. YAG lasers are often used in ophthalmology for iridotomy in glaucoma diseases and for post-cataract treatments or so-called lens polishing, i.e. to remove opacities or even post-cataract membranes on artificial lens implants as a result of cellular overgrowth. Frequency-doubled YAG lasers with laser radiation in the green range (532 nm) are also used for retinal coagulation, for example in cases of hemorrhage or retinal detachment. YAG lasers are also used less frequently for phacoemulsification in cataract surgery, i.e., liquefying the cloudy, hardened natural lens (crystalline lens). However, in this case, this tends to be an Er:YAG laser, which has a high water or tissue absorption rate at a wavelength of 2940 nm and which often has to be laboriously introduced into the eye by endoscopic laser introduction using a mirror guide.

[0014] According to the known prior art, numerous solutions already exist for performing laser surgery on eye tissue, in particular on the vitreous humor. Thus, US Pat. No. 5,399,633 discloses an apparatus and method for femtosecond laser surgery, in particular on tissue in the vitreous humor of the eye. The apparatus consists of an ultrashort pulse laser with a pulse length in the range of about 10 fs to 1 ps, in particular about 300 fs, a pulse energy in the range of about 5 nJ to 5 μJ, in particular about 1 to 2 μJ, and a pulse repetition rate of about 10 kHz to 10 MHz, in particular 500 kHz. The laser system is coupled to a scanning system that allows a spatial variation of the focus in three dimensions. Furthermore, a beam guidance by an optical system is provided, which images a scanner mirror for lateral focus displacement (x, y) in the immediate vicinity of the pupil of the eye to be treated. In order to realize a shift of the focus position in the axial (z) direction, the beam spread can be changed during the process. In addition to this therapeutic laser scanner optical system, the apparatus further comprises a navigation system coupled to it.

[0015] US Patent No. 5,399,633 describes a system and method for making incisions in ocular tissue at various depths. The system and method focus light at different focal points, possibly in a pattern, located at different depths in the ocular tissue. Multiple focal points can be generated simultaneously by segmented lenses. Optimal incisions are obtained by focusing light successively or simultaneously at different depths, generating an extended plasma column and a beam with an extended waist. The techniques described in this case can be used, among others, to perform novel ophthalmic methods or to improve existing methods, including incisions in tissues of the posterior pole, such as vitreous opacities, membranes and retina. This document describes that imaging methods such as OCT or ultrasound can be used to determine the position and thickness of the lens and the lens capsule, so that the laser can be focused with greater precision. Laser focusing can be performed by direct observation of the target laser (this is known) and it is also mentioned that laser focusing is alternatively possible by direct observation of OCT or ultrasound and other medical imaging modalities. This is at least doubtful, precisely because the target laser cannot be directly observed in the OCT or ultrasound output, and because there is no fixed positional relationship between, for example, the laser and the OCT. Thus, no explanation is provided precisely how the laser focal position is intended to be determined by the OCT or ultrasound or any other medical imaging method. However, it is precisely this problem that is addressed by the method described in the present invention for the OCDR underlying OCT.

[0016] US Patent No. 5,999,333 describes a system and method for treating a target tissue in the vitreous humor of the eye, comprising a laser unit for generating a laser beam and a detector for generating an image of the target tissue. The system also comprises a computer for defining a focal path for emulsifying the target tissue. A comparator connected to the computer then controls the laser unit to move the focal point of the laser beam. This focal movement is performed to treat the target tissue while minimizing the deviation of the focus from the defined focal path. To achieve the precision required for the method described herein, the treatment is performed using a computer-controlled laser, and the control criteria are preferably provided by an imaging detector, using a technique such as optical coherence tomography (OCT). It is not described here how the position of the focus of the femtosecond laser relative to the OCT is determined.

[0017] US Patent No. 5,399,633 also relates to a system and method for using a computer-controlled laser system to perform partial vitrectomy of the vitreous humor of the eye. In operation, an optical channel through the vitreous humor is first defined. Vitreous-like and suspended deposits (vitreous opacities) in the optical channel are then ablated and possibly removed (e.g., aspirated) from the optical channel. In some cases, a transparent liquid can be introduced into the optical channel to replace the ablated material, thereby establishing unimpeded transparency in the optical channel. In general, the invention relates to a system and method for ophthalmic laser surgery. In particular, the invention relates to a system and method for removing what is known as vitreous opacities using a pulsed laser beam. In this solution, too, an imaging unit is used that can create a three-dimensional image of the anatomical features of the eye in order to obtain the required accuracy. For this purpose, instruments based on known technology are proposed, such as Scheimpflug instruments, confocal imaging instruments, ultrasound instruments, or other imaging systems based on optical coherence tomography (OCT). However, again, this document does not explain how the position of the laser focus is determined for OCT.

[0018] US Pat. No. 5,399,433 also describes a method and a system for ophthalmic intervention in the eye. Undesirable features are identified based on an image of at least a part of the eye. For this purpose, the use of an image recorded by a camera directed at the pupil or an image showing the volume of the eye recorded by OCT is proposed. Undesirable features in the vitreous cavity are considered to be examples of vision-impairing vitreous opacities, e.g. vitreous opacities. After the vitreous opacities are identified and localized by the image processing system, they are automatically "irradiated" with a laser pulse following confirmation by the physician. The laser energy vaporizes at least a part of the vitreous-like opacity. This procedure is repeated until the vitreous opacity is removed. The entire procedure is repeated each time opacification of the vitreous humor occurs until the vitreous humor is deemed sufficiently clear. This document refers to "automatic targeting" with a laser, but does not mention how this should be performed, and in particular how this should be performed using OCT images.

[0019] Patent Document 6 proposes to first use the treatment laser to perform a microincision near the working zone, detect the position of the microincision, and correct possible deviations between the desired and actual positions, rather than using complex adjustments to fully align the focus of the treatment laser with the tissue structure to be worked on. However, this "trial and error" approach unnecessarily strains the eye (unnecessary tissue damage and exposure to the treatment laser light) and is not universally feasible. For example, it is not possible to create a stable microincision near the treatment zone when the eye is partially or completely filled with fluid, and opacities that are nevertheless suspended in the fluid should be atomized by the treatment laser.

[0020] The method described by ELLEX (Product Brochure by Ellex Medical Pty Ltd.; "Tango Reflex-Laser Floater Treatment"; PB0025B; 2018; (http: / / www.ellex.com)) provides for the use of a pulsed nanosecond laser (YAG) to break down vitreous opacities or to completely remove them by transition to gas. A pilot laser beam (i.e., a target laser in the visible spectrum range, e.g., red) is used to aim the target area (vitreous opacity), which is then "irradiated" using one or more therapeutic laser pulses. In this case, both the pilot laser beam and the therapeutic laser pulses are manually triggered by the user. Such manual laser treatments typically consist of two separate treatments, each of 20-60 minutes in duration.

[0021] US Pat. No. 5,399,633 and US Pat. No. 5,499,663 describe a system for laser vitreolysis of vitreous opacities, which allows a safe and precise atomization of vitreous opacities ("floaters"), based on the combination of a therapeutic laser with an OCT or OCDR system. Here, OCDR (Optical Coherence Domain-Reflectometry) system is understood to mean a system for interferometric acquisition of one-dimensional scattering profiles, and OCT (Optical Coherence Tomography) is understood to mean two- or three-dimensional imaging. In both cases, variants with recording sequences (i.e., films) should also be included. In this process, a minimum distance to sensitive eye structures is ensured, and the activation of the laser is preferably only allowed if the focus of the therapeutic laser and the vitreous opacity to be treated are positioned with sufficient precision relative to each other.

[0022] The drawback of these two approaches is that the physician must constantly combine the available two-dimensional views of the eye with the three-dimensional recordings of the OCT or OCDR system and their spatial visualization, which is extremely difficult in situations of time-critical or rapid interaction with the patient. This drawback is remedied by the solution described in the unpublished German patent application no. 102020212084.6.

[0023] The use of laser energy within the scope of laser vitreolysis is non-invasive and avoids the disadvantages of open eye surgical intervention, but is also associated with disadvantages and risks. For example, it may be difficult to aim the laser, and as the physician views the vitreous humor along the beam path, it may be difficult to determine the depth of the retina location, the depth of the vitreous humor opacity, or other relevant features, resulting in the vitreous humor opacity being missed and / or the eye being at risk of damage.

[0024] In particular, the treatment of nearly transparent vitreous opacities, which change position, are difficult to recognize, and, as phase objects, can generate troublesome shadows on the retina, has proven difficult.

[0025] The application of laser energy may also result in further migration of opacities in the vitreous humor, making the treatment even more difficult. Therefore, the doctor may need to realign the laser after each application of laser energy. This may require a lot of time. Therefore, treatment with laser is complicated and causes stress for both the patient and the doctor.

[0026] A further potential problem relates to incomplete vitreous detachment, which can result in localized vitreous traction leading to retinal detachment. Laser treatment in the vitreous humor can result in a change in the balance of forces in the vitreous due to shock waves propagating as a result of the treatment, thereby creating tension in the retina, for example.

[0027] Finally, the treatment of vitreous opacities located in the vicinity of sensitive structures of the eye has also proven to be particularly difficult: the mechanical and thermal loads, as well as the laser radiation itself, can cause damage to the retina, the lens or the macula and must be appropriately limited in terms of its intensity and / or energy.

[0028] However, with regard to the above-mentioned problem, it is very important to have available the most accurate knowledge of the current position of each of the therapeutic laser foci relative to the ocular structures. For post-cataract treatment or retinal coagulation, the conventional choice in this regard is to use a target laser that is usually aligned with each tissue structure to be treated by the operator by observing the backscattering from the target laser radiation. However, this is practically impossible when the structure to be treated is a very weakly scattering object that can only be practically detected by a very sensitive system such as, for example, OCT or OCDR. For example, conventional OCT and OCDR systems may have a sensitivity of more than 85 dB, 90 dB, 100 dB or 110 dB, which allows the detection of normal vitreous humor backscattering, i.e., the detection of vitreous opacity, to be more than about 90 dB.

[0029] However, when an OCT-based system, rather than a target laser, is used, there is a complex problem of assigning the therapeutic laser focal position to a position in the OCT or OCDR scan with sufficient accuracy. This is due to the fact that the focal position of the axial therapeutic laser may already change significantly in the beam path as a result of changing refractive power (e.g. surface curvature), while the latter has practically no effect within the OCT or OCDR on the position of the signal of the scattering object of the OCT or OCDR. The YAG focal diameter and the axial Rayleigh length in the interior of the eye are of the order of about 20 μm, so small deviations are already problematic if delicate objects with similar spatial dimensions are intended to be treated. In this regard, even small changes resulting, for example, as a result of thermal effects in the laser during a relatively long operation, may have relevant effects and require a realignment of the focal position in relation to the OCDR.

[0030] Some of the solutions known from the prior art using OCT systems assume known focal length, refractive power, distance parameters and sample position, so that a calculation of the focal position for OCT or OCDR is possible in principle. However, this still requires sufficiently accurate knowledge or very accurate determination of these parameters, which is very complex, especially considering the determination of all relevant refractive powers in the eye (e.g. of the corneal and lens surfaces). In addition, data obtained before surgery may be insufficient, since changes in the corneal refractive power depending on the contact pressure may occur during use, for example during the use of hand-held contact glasses (contact lenses). Furthermore, there is a considerable variability in the anatomy of the human eye. For example, the eye length ranges from 14 to 40 mm, and there is a large variability in the depth of the anterior chamber (1.5 to 4 mm) or the thickness of the lens (crystalline lens: about 3 to 4 mm, e.g. when a multipart IOL is used, the IOL is partly thinner or partly thicker).

[0031] In addition to the different focal depths and varying refractive powers of individual eyes, the tolerances of the optics of the laser system can also result in further deviations in the focal position of the therapeutic laser. The concept proposed in US Pat. No. 6,299,226 of varying (i.e., adjusting) the focal positions of the OCDR and treatment laser together and deriving the adjustment between the OCDR and treatment laser focal points from the resulting change in the OCDR signal also requires a sufficiently finely adjustable focal position with simultaneous synchronized OCDR detection, which becomes slightly more complicated, especially if different axial focal positions of the OCDR and treatment laser are intended to be used (i.e., if an offset between the foci must exist). In addition, this approach is made more difficult by the fact that OCDR or OCT recordings have "speckle" due to their coherent characteristics, and therefore the maximum signal point around the focal point may only be determined at a small additional cost (e.g., by speckle suppression as in US Pat. No. 6,299,226 or US Pat. No. 6,299,226). [Prior art documents] [Patent documents]

[0032] [Patent Document 1] DE 102011103181 A1 [Patent Document 2] US Patent Application Publication No. 2006 / 195076 [Patent Document 3] US Patent Application Publication No. 2014 / 257257 [Patent Document 4] US Patent Application Publication No. 2015 / 342782 [Patent Document 5] US Patent Application Publication No. 2018 / 028354 [Patent Document 6] European Patent Application Publication No. 3578148 [Patent Document 7] DE 102019007147 [Patent Document 8] DE 102019007148 A1 [Patent Document 9] U.S. Pat. No. 8,085,408 [Patent Document 10] DE 102008051272 [Non-patent literature]

[0033] [Non-Patent Document 1] Brasse, K., Schmitz-Valckenberg, S., Juenemann, A. et al., Ophthalmologe (2019) 116:73. Internet<URL:https: / / doi.org / 10.1007 / s00347-018-0782-1> Summary of the Invention

[0034] It is therefore particularly important in the case of OCDR or OCT-assisted systems to enable the focal position of the treatment laser to be estimated as accurately as possible with respect to the tissue to be treated and the eye structures to be preserved. In this connection, adjustments carried out so far according to solutions from the prior art, in particular using a test eye or assumed or predefined parameters, have proved to be insufficient or very complicated.

[0035] The present invention is therefore based on the objective of developing a solution for an ophthalmic system for intraocular laser therapy, which remedies the drawbacks of known technical solutions by taking into account the individuality of the treated eye and the tolerances of the optical system by readjusting the focus of the therapy laser. In particular, it should make it possible to adjust the focal position of the therapy laser relative to the OCT or OCDR scan precisely for each new treatment situation, in particular following a change of patient and / or contact glasses, or a modification of the focal length of the therapy laser, the accommodation state of the patient, and / or the sample interval.

[0036] Furthermore, the solution should be easy to implement, economically cost-effective and allow for easier, faster and above all safer eye laser treatment. This object is achieved by the method according to the invention for readjusting the focus of an ophthalmic system for intraocular laser treatment comprising an OCDR system, a control unit, a treatment laser unit, an imaging unit and an optical system for focusing and beam overlap, in which a target laser beam of the laser treatment system is focused on at least one target structure ZS1 of the eye to be treated by changing the distance A of the laser treatment system from the eye until focusing of the target laser beam of the laser treatment system on the target structure ZS1 is detected, a distance A1 from the position of a selected reference structure PRS relative to a reference plane RE and the position of the target structure PZS1 in the OCDR signal profile are respectively determined, and each estimable focus position PF of the laser beam of the laser treatment system in the OCDR signal profile is approximately estimated using the parameters A1 and PZS1 for any selectable value of the change in distance ΔA of the laser treatment system from the eye.

[0037] According to a first advantageous configuration, at a position A1, the laser beam of the laser treatment system (or an alternative to the laser beam, such as a target laser beam or an attenuated treatment laser beam) is focused on at least one first target structure ZS1 of the eye to be treated, for example by changing the distance A of the laser treatment system from the eye between a reference plane RE at a distance ΔE in front of a reference plane BE of the laser system (for example anterior lens apex) and a reference structure RS on the eye (for example the corneal apex) until the focusing of the laser beam on the target structure ZS1 is identifiable based on the strongest backscattering of the laser beam of the laser treatment system or the target beam from the target structure, the (corresponding) position PZS1 of this target structure is determined in the OCDR signal, and the further target structure ZS1 is focused on the target structure ZS2. n(n=2, . . . , N), the respective change in distance ΔA relative to the position A1 of focusing on the first target structure ZS1 required for this purpose n is determined, and the target structure ZS n For each case where the focus is on one of the PZS n is determined, and for other values ​​of change ΔA in the distance of the laser treatment system from the eye, selectable as desired, each possible focal position PF of the laser beam of the laser treatment system is calculated based on the function

[0038]

number

[0039] is approximately determined from Here, "selectable value as desired" refers to a practically achievable distance condition between the eye and the laser system, for example, the anterior and posterior sides of the lens in a phakic eye, and the anterior or posterior sides of the IOL, or to some extent the IOL haptics (preferably extensive plastic haptics) in an aphakic eye, are suitable as target structures.

[0040] Generally, contact glasses (contact lenses) or the anterior and posterior sides of the cornea, as well as the retinal surface, are suitable target structures. If the vitreous opacity scatters the target laser beam sufficiently strongly, it is also suitable as a target structure. Generally, in order to obtain the highest possible accuracy for the assumed focal position PF(ΔA), it is advantageous to use a target structure that is arranged as "close" as possible to the processing area (not only axially but also laterally), for example with a proximity of less than 2 mm, preferably less than 1 mm, and even more preferably less than 100 μm.

[0041] According to the invention, the deviation of the approximate determination of the estimable focal position PF of the laser beam from the actual position is less than 2 Rayleigh lengths of the laser focal point, in particular less than 1 Rayleigh length, or particularly preferably less than 0.5 Rayleigh lengths. The Rayleigh length is z R =n*π*w0 2 / M 2 where n corresponds to the refractive index of the medium, w0 corresponds to the radius of the laser beam at the focus, and 1 / M 2 corresponds to the beam quality (ideally, M=1). In this context, twice the Rayleigh length corresponds to the usual definition of the depth of field of material processing lasers (A. Barth, H. Müller, J. Brietner, "Laser material processing (Lasermaterialbearbeitung)", Hanser Verlag; https: / / www.hanser-fachbuch.de / buch / Lasermaterialbearbeitung / 9783446421684), which in the case of laser applications to the eye is, for example, 9 μm (more likely in the case of near-surface applications with large numerical apertures) to 1 mm. In principle, it is also possible to use methods for multi-segment therapeutic laser focusing as known from the prior art. In this case, however, an individual adjustment of all focal segments with a switchable or multi-segment target laser, or at least an individual adjustment of the selected therapeutic laser focal segment, would be required, so that the readjustment of the selected focal segment can be used as the basis for realizing a position estimation of the other focal segments.

[0042] The dependent claims relate to preferred developments and configurations. According to a second configuration, the intersection point of the multiple target lasers, rather than the laser beam of the laser therapy system, is focused on at least one target structure ZS of the eye to be treated. In particular, as the target laser, a continuous wave laser beam is used, which has the same or similar focal position as the laser beam of the laser therapy system. In this case, the individual target structures ZS nThe focusing of the target laser on can be detected by detecting the maximum backscattering of the target laser radiation from each "focused" target structure by the operator's eye or by a camera with image processing, the latter in particular when it is intended to use invisible target laser radiation, e.g. at 800 nm or 1060 nm in the NIR.

[0043] In the proposed method, the posterior side of the lens (crystalline lens or IOL), the posterior side of the lens capsule, the retinal surface, or other structures of the eye are aligned with the target structure ZS n It functions as: According to a third configuration, at least one target structure ZS having stability at least in the short term is generated by a laser beam of a laser therapy system or by a target laser, e.g. by a laser shot from a laser therapy system or by a modulated target laser, by bringing about at least one modification in the eye whose detectability is sufficient for adjustment and which results in a characteristic measurable signal change in OCDR.

[0044] For example, in this case the modulation of the target laser is performed in an acousto-optical, electro-optical or interferometric manner, or there is a wavelength or polarization modulation. However, it is also possible to modulate the target laser by current modulation or a variable attenuator, such as a filter wheel, chopper, etc. Then, by subjecting the OCDR signal to a filtering adapted to this modulation, in order to determine very precisely the position of the laser focus in the OCDR signal, the characteristic laser modulation applied thereby can be detected again in the speckle fluctuations.

[0045] In alternative forms, for example, an attenuated shot of a laser therapy system can also generate bubbles that are at least short-term detectable in the OCDR (detectable until they rise from the OCDR beam) as a result of plasma expansion, or a modulated target laser beam can also result in locally modulated phase modulation or speckle fluctuations in the OCDR or OCT signal in the focal area as a result of light absorption and local heating. In the latter case, it is advantageous if the target laser intersects the OCDR or OCT beam at an angle in the focal area in order to generate there a maximally transient signal of the target structure. However, in this situation, the modulation frequency should not be too high so that a temperature modulation is still possible by heat dissipation. Possible modulation frequencies are in the range of 0.1-100 Hz, advantageous modulation frequencies are in the range of 5-50 Hz. Advantageous target laser wavelengths are in the NIR, for example 1.2-1.7 μm, in particular 1.3 μm-1.5 μm, at which wavelengths water is well absorbed and the light exposure of the patient's retina is low.

[0046] Compared to prior art techniques, this approach allows repeatable focusing at the desired frequency even in unstable media that have no native target structures, such as the aqueous humor of the anterior chamber, or partially liquefied vitreous humor, or saline that replaces the vitreous humor after vitrectomy.

[0047] In this regard, it is advantageous that the target structure ZS generated by a laser shot of the laser beam of the laser treatment system can be used not only to determine the focal position but also to adjust the laser power.

[0048] According to a fourth configuration, the front or rear side of an existing contact glass KG, a technical structure located in the contact glass or a natural or artificial eye structure, e.g. the cornea, the lens or IOL, the front or rear side of the lens capsule or the retinal surface, serves as a reference structure RS for determining the respective distance A between the eye and the laser system.

[0049] In this case, a reference structure RS realized in the contact glass KG generates a characteristic signal in the OCDR, the realized reference structure RS being preferably variable, in particular switchable or modulatable.

[0050] According to a particularly advantageous fifth configuration, in order to estimate as accurately as possible the respective estimable focal positions PF of the laser beams of the laser treatment system from the function (1) for any selectable value of the change in distance ΔA, the points of intersection of the laser beams of the laser treatment system or of the multiple target lasers are determined by the function (1) for N target structures ZS of the eye to be treated. n The parameters specified as function indices are as follows: A1, ΔA n=2,···,N is the eye distance and its change with respect to A1, in this case the target structure ZS n The focus is on PZS n is the signal position of the target structure in the OCDR confirmed in each case. A1 is the reference distance for all distance changes ΔA, so that ΔA1 is no longer listed here as a parameter, since in practice ΔA1=0 applies. If a different reference distance is chosen for A1, then its distance ΔA1 from the reference distance can of course also be used instead of A1 as a parameter of the function, rather than A1 as a parameter. The function

[0051]

number

[0052] To determine the focal position PF(ΔA) for the point ΔA, a polynomial of preferably from 1st to Nth order (or a different nonlinear function with N degrees of freedom, e.g., a Fourier series) is used, which determines the focal position PF(ΔA) with the smallest possible deviation from the point ΔA n=1,···,N ,PZS n=1,···,N For example, this can be done by fitting a polynomial or a non-linear function to the points, for example by applying a least squares method.

[0053] However, the function (1) for determining the focal position FP can also be a polynomial or nonlinear function of degree higher than N, with additional parameters of the contact glass or eye used to determine the polynomial or nonlinear function.

[0054] According to a sixth configuration, the imaging system, together with a laser beam of the laser treatment system or the target laser, includes a plurality of target structures ZS n The imaging system is additionally focused on the laser beam, for which an autofocus system is used. In particular, in this case, the difference between the numerical aperture (NA) of the imaging system and the numerical aperture of the laser beam of the laser treatment system is less than a factor of two. In this case, it is particularly advantageous if the deviation between the wavelength of the imaging system and the wavelength of the laser beam of the laser treatment system from each other is less than 10%.

[0055] According to a seventh configuration, the method for refocusing a treatment system comprising, in addition to a focusing unit, also an OCDR system and a control unit, is used for laser vitreolysis.

[0056] In this case, the laser beam of the laser treatment system is focused on the first target structure ZS1 and then on each target structure ZS n The distance A of the treatment system for laser vitreolysis is changed starting from the reference plane RE by a change ΔA relative to the eye until the focusing of the laser beam on the treatment laser or the target beam laser becomes identifiable based on the maximized backscattering of the laser beam, thereby obtaining two or more target structures ZS of the eye to be treated. n (n=2, , N) and the change in distance ΔA n is determined for this focusing situation, and for this focusing situation, ΔA n The target structure ZS, on which focusing is just performed n Position of PZS nis determined from the OCDR signal, and for other values ​​of the distance change ΔA, which can be selected as desired, respective possible focal positions PF of the laser beam of the treatment system for laser vitreolysis are approximately determined from the function (1). Preferably, respective structures in the anterior and posterior eye regions, preferably behind the lens and on the retinal surface, are located at the target structure ZS n is selected as.

[0057] Position of the treatment laser focus for any desired distance ΔA of the laser system from the eye

[0058]

number

[0059] The approximate determination of is used in this case to establish the therapeutic laser focus position (at the time of triggering the laser shot) relative to the blocking zone of the treatment system for vitreous opacification and the resulting start or stop of the therapeutic laser. In this connection, it is also possible to detect eye movements, in particular axial eye movements, for example by OCDR, and then to take these into account correctly when estimating the therapeutic laser focus position affected by the latency time.

[0060] It is particularly advantageous if at least one target structure ZS is selected in the vicinity of the ocular structure to be processed, which also provides the option of generating a permanent or temporary target structure using an (attenuated) treatment laser or using a target beam laser.

[0061] In the case of a treatment system for laser vitreolysis, it is necessary to ensure that in each case, depending on the working depth, a sufficiently large pupil diameter is present in order to ensure a sufficiently short depth of field of the treatment laser. To ensure this, preferably an imaging system for the pupil area is used, with which the currently existing pupil diameter is determined. Alternatively, it is also possible to use as a criterion the backscattering of the target laser, which corresponds to the treatment laser beam at the edge of the insufficiently dilated pupil. The favorable pupil diameter is more than 4 mm in the case of laser vitreolysis procedures in the anterior region, more than 5 mm in the case of such procedures in the central region, and more than 6 mm in the case of such procedures in the posterior region. The treatment system prevents the treatment laser from being triggered and provides a warning if these conditions are not met. Optionally, in such cases, the ambient light in the treatment room must be reduced or pupil dilation must be caused by a drug.

[0062] The method according to the invention for refocusing an ophthalmic system for intraocular laser treatment is provided in particular for realizing a treatment system for laser vitreolysis. Other possible intraocular application options that would benefit from the proposed method for refocusing a laser treatment system include, but are not limited to, for example:

[0063] ·Retinal coagulation ·SRT (Selective Retinal Treatment) Vitreous humor dissection, e.g. to treat vitreomacular traction Laser trabeculoplasty (e.g. SLT) or trabeculotomy (e.g. ALT) Post-cataract treatment Femtosecond cataract surgery (open and phacotomy) Corneal incision or ablation The invention is described in more detail below on the basis of exemplary embodiments. [Brief description of the drawings]

[0064] [Figure 1] FIG. 1 shows a treatment system for laser vitreolysis focused on a first target structure ZS1 of the eye to be treated. [Diagram 2] FIG. 2 shows a treatment system for laser vitreolysis focused on a second target structure ZS2 of the treated eye. [Diagram 3] FIG. 3 shows a treatment system for laser vitreolysis using contact glasses having reference structures RS. [Figure 4] FIG. 4 shows a function PF(ΔA) for determining any desired focal position PF of a laser beam of a laser treatment system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] The proposed method for refocusing an ophthalmic system for intraocular laser treatment comprises a treatment laser unit, an imaging unit, an optical system for focusing and beam overlapping, an OCDR system, and a control unit.

[0066] According to the invention, the laser beam of the laser therapy system is focused on at least one first target structure ZS1 of the treated eye by varying the distance A1 of the laser therapy system from the eye until focusing of the laser beam on the target structure ZS1 is achieved. The distance A1 is determined from the position of the selected reference structure PRS and the target structure PZS1 in the OCDR signal profile relative to the reference plane RE. For any selectable value of the change ΔA in the distance of the laser therapy system from the eye, it is possible to provide an approximate estimation of each estimable focus position PF of the laser beam of the laser therapy system in the OCDR signal profile using the parameters A1 and PZS1.

[0067] In this case, the focusing of the target laser on the target structure ZS1 can be detected by detecting the maximum backscattering of the target laser radiation from the "focused" target structure ZS1 by the operator's eye or using a camera with image processing. The position of the OCDR signal PZS1 of the target structure ZS1 is then determined.

[0068] Preferably, the determined values ​​A1 and PZS1 are functions that approximately calculate the respective estimable focal positions PF of the laser beam of the laser treatment system in the OCDR signal profile for any selectable value of the change ΔA in the distance of the laser treatment system from the eye.

[0069]

number

[0070] is used to determine Further target structures Z2 to Z3 are provided for the purpose of increasing the adjustment accuracy over a large depth range. N should be "focused" in the same way, the change in distance ΔA2~ΔA n are the positions PZS2 to PZS of the target structure signal present in the process. n Similarly, for each of these target structures, the laser beam of the laser treatment system or the target laser is focused in the best way. Then, the values ​​A1 and PZS1 thus determined, and optionally ΔA2 to ΔA3 are calculated. n and PZS2 to PZS n Using the function

[0071]

number

[0072] can be determined which approximately determines each possible focal position PF of the laser beam of the laser therapy system for other values ​​of the distance change ΔA, which can be selected as desired.

[0073] As already mentioned above, the parameters designated as indices are A1 as the distance between the eyes, and ΔA as their change with respect to A1. n=2,···,N In this case, the target structure ZS n The focus is on PZS n is the signal position of the target structure in the OCDR identified in each case. Function (1)

[0074]

number

[0075] To determine the focal position of the point ΔA, preferably with as small a shift as possible n=1,···,N ,PZS n=1,···,N Use a polynomial of degree 1 through N, or a different nonlinear function with N degrees of freedom, chosen to pass through . For example, this can be done by fitting a polynomial or nonlinear function to the points, for example by applying a least squares method.

[0076] Preferably, the focusing of the laser beam of the laser therapy system on at least one target structure ZS of the eye to be treated by the therapeutic laser is performed with reduced pulse energy to avoid photodamage. It is also possible to use an additional laser beam as the target laser beam, the parameters of which do not allow permanent tissue changes in the eye.

[0077] According to the invention, the deviation of the approximate determination of the estimable focal position PF of the laser beam from its actual position is less than 2 Rayleigh lengths of the laser focus, in particular less than 1 Rayleigh length, or particularly preferably less than 0.5 of a Rayleigh length.

[0078] In the case where the laser treatment system includes multiple target lasers, the intersection point of the multiple target lasers, rather than the laser beam of the laser treatment system, can be focused on at least one target structure ZS of the eye to be treated. This can indicate the position of the focus of the laser beam of the laser treatment system continuously or quasi-continuously, or optionally in a pulsed manner. For this purpose, a target beam laser in the visible spectral range can be used, but it can also be NIR, for example, if a camera system is used. To indicate the position of the focus of the laser beam of the laser treatment system, the target laser can be, for example, collinearly superimposed on the laser beam of the laser treatment system and have the same focus position. If this is then used to focus on the target structure, it can be identified based on the backscattered target laser spot of the smallest dimension and greatest intensity on the target structure (detectable by eye in VIS or by a camera in NIR). In an alternative, multiple target laser beams that intersect at the position of the focus of the laser beam of the laser treatment system can also be used. In a further alternative, one or more moving, for example rotating, target laser beams can be used, each passing through the position of the focus of the laser beam of the laser treatment system.

[0079] In this case, detection of focusing on the target structure is performed by visual or automatic establishment of one or more of the following conditions: Maximized backscattering of the target laser from the target structure Minimized diameter of the light distribution of the target laser beam on the target structure, or A characteristic state or change in the OCDR signal of the target structure According to the invention, the intersection point of the multiple target lasers is preferably focused on the target structure ZS by minimizing the spacing of the multiple target laser beams by an operator or a camera system, or by maximizing backscattering from at least one target laser beam focus by confocal detection, in which case the target lasers preferably operate in the visible or NIR spectral range.

[0080] According to an advantageous configuration, a continuous wave laser having the same or similar focal position as the laser beam of the laser therapy system is used as the target laser, or the target laser is provided by a continuous wave laser having a known or adjusted limited deviation of the focal position from the laser beam of the laser therapy system that is taken into account during the laser vitreolysis. By way of example, this can be taken into account by a suitably adapted indication of the focal position or by a momentary focal shift of the laser beam of the laser therapy system before the laser is triggered, for example by a change in the beam divergence realized opto-mechanically (e.g. by a movable lens) or electro-optically (e.g. by a liquid crystal lens).

[0081] Preferably, the posterior side of a lens (especially an intraocular lens, IOL) or capsule, the anterior surface of the retina, or other structures of the eye serve as target structure ZS. However, it is also possible to generate the target structure ZS by the laser beam of the laser treatment system itself. For example, the target structure ZS generated by the laser shot of the laser beam of the laser treatment system causes a change in the vitreous humor, which then causes a signal change in the OCDR, for example a change in backscattering or a change in speckle grain.

[0082] In this case, the target structure ZS generated by the laser shots of the laser beam of the laser treatment system is temporary or changeable, for example, a bubble generated by at least one laser shot, or a speckle structure of the OCDR that has changed temporarily as a result of heating. Such changes can also be generated by the target laser beam, for example, when the target laser beam is modulated and, as a result, generates, by optical absorption, local characteristic signal variations (e.g., speckle variations) in the OCDR depth profile that intersects with the OCDR beam.

[0083] However, the advantage of generating the target structure ZS by laser shots of the laser beam of a laser therapy system is that said target structure can be used not only to determine the focal position but also to adjust the laser power, which is also possible indirectly by the absorption behavior of the target laser, but is more difficult, since possible wavelength differences must be taken into account or avoided.

[0084] According to the invention, the front or rear side of existing contact glasses KG, technical structures located within the contact glasses, or eye structures such as the front or rear side of the cornea, lens or lens capsule, or the retinal surface, are used as reference structures RS for the OCDR system.

[0085] If the ophthalmic system for intraocular laser treatment requires contact glasses KG, the technical structure realized as the reference structure RS can be preferably configured such that a characteristic signal in the OCDR is generated, for example a signal with a specific signal level, plateau, curve, position, distance or multiple peaks, or a characteristic polarization dependency. In particular, the reference structure RS realized in the contact glasses KG can be changeable, in particular switchable or modulatable, for example by a change in scattering or polarization. For example, this can be realized by an electrically switched liquid crystal layer.

[0086] According to a further advantageous configuration, the reference structure RS realized in the contact glass KG operates in the non-visible spectral range and is realized, for example, by means of a dielectric reflector layer system. Preferably, this dielectric reflection layer system is configured as a bandpass filter, for example to partially reflect the beam of the NIR target laser at wavelengths between 780 nm and 850 nm, but to mainly transmit the therapeutic laser at wavelengths of 1064 nm and the visible light at wavelengths between 400 nm and 700 nm. However, at the OCDR wavelength, for example 1060 nm, the reference structure RZ realizes a backscattering of less than 3%, preferably less than 0.5%, to avoid saturation in the OCDR signal. Preferably, the reference structure RS is configured to have a signal in the OCDR with a signal-to-noise ratio of more than 10 dB, more than 20 dB or more than 30 dB, but preferably less than 40 dB, especially against a noise background caused by shot noise.

[0087] For example, the position PZS of the target structure nand the location of the reference structure PRS is identified by determining the maximum or centroid value or threshold of the OCDR signal or by fitting a signal model. In this case, the location of the signal in the OCDR thus determined is preferably assigned to the target or reference structure by using the expected signal sequence in the OCDR signal curve (e.g., anterior or posterior side of the contact glass, corneal surface, optionally anterior side of the lens capsule, anterior and posterior side of the IOL, optionally posterior side of the lens capsule, retinal surface). In this process, characteristic signal intensities, for example at the contact glass or IOL, can also be used to automatically include or exclude expected structures in the signal sequence. For this purpose, characteristic signal curves can also be used, for example, sharp reflections at the IOL surface and at the same time backscattering intensity, which is lower compared to the natural lens (crystalline lens), inside the IOL, i.e. between the sharp surface reflections. In this case, the characteristic signal curve can extend axially, but also laterally. For example, the lens capsule curve can have a substantially "welliger" profile laterally than the surface of a conventional IOL. In particular, multifocal IOLs (e.g., Fresnel optics) may even have a typical recognizable pattern. Furthermore, a plausibility check can be made for the range of possible or possible depths of a particular structure, for example with respect to the range of possible corneal thicknesses, anterior chamber depths, or eye lengths. Furthermore, in the special case where, for example, phakic IOLs are used, statements about the eye structure given by the operator can also be used.

[0088] According to an advantageous configuration, the imaging system is focused together with the laser beam of the laser therapy system on a number of target structures ZS, for which an autofocus system is used. Preferably, the NA of the imaging system and the NA of the laser beam of the laser therapy system differ by less than a factor of two.

[0089] In the following, the proposed method for refocusing an ophthalmic system for intraocular laser treatment is explained in more detail on the basis of a treatment system for laser vitreolysis. The treatment system for laser vitreolysis includes, in addition to a focusing unit and a control unit, an OCDR system.

[0090] A sufficiently large pupil diameter depending on the working depth must be ensured for laser vitreolysis, in particular more than 4 mm for laser vitreolysis procedures in the anterior region, more than 5 mm for such procedures in the central region, and more than 6 mm for such procedures in the posterior region. In particular, a verification of the pupil diameter can be used to ensure that the treatment laser can only be activated if a sufficiently large pupil diameter is recognized for the respective desired working depth.

[0091] In this regard, FIG. 1 shows a treatment system 2 for laser vitreolysis focused on a first target structure ZS1 of an eye 1 to be treated. The treatment system 2 for laser vitreolysis comprises a treatment laser 3, an OCDR system 4, an imaging system 5, an optical system 6 and a control unit (not shown here).

[0092] The laser beam 7 of the treatment laser 3 is focused on the target structure ZS1 of the treated eye 1 by changing the distance A of the treatment system 2 for laser vitreolysis relative to the eye 1 represented by the reference structure RS (e.g. the corneal surface) starting from the reference plane RE until the focusing of the laser beam on the target structure ZS1 (in this case the rear side of the lens as an example) at the eye distance A=A1 becomes discernible. In this case, the focusing on ZS1 can be discerned by observing the maximized backscattering of the (attenuated) laser beam 7 or the target laser (not shown here) from the target structure ZS1 by the imaging system 5 or by observing the maximized OCDR signal (grey peak) of the target structure at the position PZS1 in the OCDR signal profile 8 if the focal positions of the OCDR beam (not shown here) and the laser beam 7 are sufficiently coincident with each other. Overall, the OCDR signal profile 8 is a 0 to Z max When focused on the target structure ZS1, the focal position PF1 of the laser beam 7 at the OCDR corresponds exactly to the OCDR position PZS1 of the target structure.

[0093] For example, the front lens surface of the optical system 6 serves here as a further reference plane BE. Since the measurement range of the OCDR system 4 generally only includes a range slightly larger than the entire length of the treated eye 1, in order to perform the measurement, a reference plane RE is set by the reference arm of the OCDR system 4 at a distance ΔE from BE. In the refocusing, without loss of generality, the assumption is made that the reference plane is not changed between the adjustment steps. Even so, the position PZS nshould be adapted accordingly. In this connection, it is noted that the refractive index between BE and RE corresponds to the refractive index of the surrounding medium (generally air with a refractive index of 1). The refractive index between RE and RS can be that of air or, in case contact glasses are used, can include a section with the refractive index of glass or plastic (e.g. n = 1.2,...,1.8). Furthermore, since the refractive indices of the eyes are slightly different (aqueous and vitreous humor are about 1.36, the cornea is about 1.38, and the IOL depends on the material used) and can also differ from patient to patient, in general, the position PZS n It is recommended to approximately determine the focal position PF(ΔA) and the focal position PF(ΔA) as the respective optical path length relative to the reference plane RE. In order to make as few or no adjustments of ΔE during refocusing, the depth range 0-Z covered by the OCDR signal profile 8 is max is selected to cover at least the depth of the posterior eye (>25 mm optical path), but ideally also the entire mean eye length (>34 mm optically), or ideally an extended range of >60 mm or >100 mm (in either case optically). For this purpose, an OCDR system with an appropriate coherence length should be used.

[0094] The distance A1 and the target structure position PZS1 are then determined from the OCDR signal profile 8 as the optical path length relative to the reference plane RE, respectively. By way of example, in this case the anterior surface of the cornea is used as the reference structure RS and the posterior side of the lens is used here as the target structure ZS1.

[0095] For OCDR signal profile 8, from left (0) to right (maximum measurement range Z maxThe signal peaks shown diagrammatically up to 1000 nm correspond to the anterior and posterior corneal surfaces, the anterior and posterior lens surfaces, and the retinal surface of the treated eye 1. For clarity, background noise, signals from deeper retinal or choroidal layers, and the lens capsule signal are not depicted here. Whether the lens capsule signal is distinguishable from the lens surface signal depends, for example, on the particular situation, i.e., whether the lens capsule is stationary relative to the lens, and on the sensitivity and resolution of the OCDR system.

[0096] FIG. 2 shows a treatment system 2 for laser vitreolysis focused on a second target structure ZS2 of the treated eye 1. For this purpose, the laser beam 7 of the treatment laser 3 is focused on the target structure ZS2 of the treated eye 1 by changing (by ΔA) the distance A of the treatment system 2 for laser vitreolysis from the eye 1, starting from the reference plane RE, relative to the initial position A1, until the focusing of the laser beam on the respective target structure ZS2 becomes identifiable again (as described above, for example based on maximizing the backscattering of the treatment or target laser, or optionally on maximizing the local OCDR signal, in case of a coincidence of the beam shapes between the OCDR and treatment laser). For this purpose, the treatment system 2 for laser vitreolysis can be moved (manually or by a motor-movable equipment base (not shown here)) or vice versa (for example by a motor-driven patient head support) relative to the eye 1.

[0097] Subsequently, the distance A=A2 or ΔA2=A1-A2 and the position of the OCDR signal PZS2 of the second target structure ZS2 are determined from the OCDR signal profile 8, where the anterior surface of the cornea continues to serve as the reference structure RS and the retinal surface serves as the second target structure ZS2. Here, the position of the reference structure in the OCDR signal profile 8 is PRS*, which is different from the position of the reference structure PRS when focusing on ZS1.

[0098] By focusing on the second target structure ZS2, the position of the target structure PZS2 also corresponds, in this case as an optical path relative to the reference plane RE, to the position PF2 of the focus of the treatment laser 3.

[0099] From the values ​​A1, ΔA2, PZS1, and PZS2 obtained in this way, at least one function

[0100]

number

[0101] can be derived, which ideally corresponds to PF(ΔA1=0)=PZS1 and PF(ΔA2)=PZS2 which can be used to approximately determine the respective estimable focal position PF of the treatment laser 3 for other values ​​of the distance change ΔA, which can be selected as desired. In this case, the function PF(ΔA) can have a deviation between the approximately determined focal position of the treatment laser and the actual focal position of the treatment laser of less than 2 Rayleigh lengths of the treatment laser focus, in particular less than 1 Rayleigh length, or particularly preferably less than 0.5 of a Rayleigh length.

[0102] The steps of determining the parameters ΔA2 and PZS2 shown in FIG. 2 are finally used to determine an expanded set of parameters A1, ΔA2 . . . ΔA N ,PZS1···PZS N To obtain the target structure ZS3, ,ZS n The same can be repeated for further steps of focusing on the expanded set of parameters A1,ΔA2...ΔA N ,PZS1···PZS N provides a function that provides greater accuracy for estimating the focal position of the treatment laser for any desired eye distance ΔA.

[0103]

number

[0104] Again, the determined function should ideally pass through the measurement points exactly, i.e., PF(ΔA n )=PZS n However, over the entire curve, it should preferably always be possible for the deviation between the approximately determined therapeutic laser focus position and the actual therapeutic laser focus position to be less than 2 Rayleigh lengths of the therapeutic laser focus, in particular less than 1 Rayleigh length, or particularly preferably less than 0.5 Rayleigh lengths.

[0105] Contact glasses are also used in laser vitreolysis procedures, among other things, and are described in more detail below. In this regard, FIG. 3 shows a treatment system for laser vitreolysis using contact glasses KG having a reference structure RS.

[0106] The treatment system 2 for laser vitreolysis comprises a treatment laser 3, an OCDR system 4, an imaging system 5, an optical system 6 and a control unit (not shown here) and provides for the use of contact glasses KG.

[0107] The laser beam 7 of the treatment laser 3 is focused on the target structure ZS1 of the treated eye 1 (in this case the anterior side of the lens capsule) by varying the distance A of the treatment system 2 for laser vitreolysis starting from the reference plane RE, relative to the eye 1, until the focusing of the laser beam 7 on the respective target structure ZS2 becomes recognizable (as described above, for example based on maximizing the backscattering of the treatment or target laser, or optionally maximizing the local OCDR signal, when the beam shape between the OCDR and treatment laser is consistent).

[0108] The distance A=A1 from the reference plane RE to the position of the reference structure PRS and the target structure position PZS1 are then determined from the OCDR signal profile 8 as the optical path length relative to the reference plane RE, respectively. In this case, in the variant of the embodiment shown here, the reference structure RS is located within the contact glasses KG being used. The reference structure is therefore located outside the eye, but has a sufficiently fixed relationship to the eye as a result of the contact.

[0109] By focusing on the target structure ZS1, the position of the target structure PZS1 also corresponds to the position PF1 of the focal point of the treatment laser 3. For OCDR signal profile 8, from left (0) to right (maximum measurement range Z max The illustrated signal peaks up to 1000 nm correspond to the anterior surface of the contact glass, the technical structure RS within the contact glass, the anterior and posterior surfaces of the cornea of ​​the treated eye 1, the anterior surface of the lens capsule, the anterior and posterior surfaces of the lens, the posterior surface of the lens capsule, and the retina.

[0110] As mentioned above, the front or rear side of existing contact glasses KG or a technical structure which can additionally be embodied so as to be individually changeable, in particular switchable or modulatable, can be used as the reference structure RS.

[0111] In Fig. 4, a function PF(ΔA) for determining any desired focal position PF of the laser beam of the laser therapy system is shown as an example. In this case, the target laser beam of the laser therapy system was focused on three target structures ZS1, ZS2, and ZS3 of the eye to be treated by changing the distance A of the laser therapy system from the eye until the focusing of the target laser beam of the laser therapy system on the target structures ZS1, ZS2, and ZS3 was detected and the corresponding distances A1, A2, and A3, or the change in distance ΔA2 and ΔA3 relative to A1, were determined. Using the function PF(ΔA) obtained from these sampling points, it is possible to determine each possible focal position PF of the laser beam of the laser therapy system for any selectable value of the change in distance ΔA of the laser therapy system from the eye.

[0112] According to a further preferred configuration, the imaging system is moved together with the laser of the vitreolysis system, and focusing on the target structure ZS is in each case achieved by an autofocus system. In this case, focusing is performed, for example, by changing the focal length or by changing the distance between the system and the patient's eye, and thus, for example, a motorized head support or a motorized instrument head can also be used.

[0113] In this context, it is advantageous if the numerical aperture (NA) of the imaging system and the numerical aperture of the treatment laser are similar, ie they differ by less than a factor of two. It is also advantageous if the OCDR system and the treatment laser operate at similar wavelengths, i.e., less than 10% offset, preferably with wavelengths around 1060 nm, since in this case a long coherent tunable laser can be used for OCDR (i.e., SS-OCDR) and a 1064 nm YAG laser can be utilized as the treatment laser.

[0114] The proposed device for refocusing an ophthalmic system for intraocular laser treatment comprises a treatment laser unit, an imaging unit, an optical system for focusing and beam overlapping, an OCDR system and a control unit.

[0115] For a description of the function of the device for refocusing an ophthalmic system for intraocular laser treatment, please refer to the method described above. According to the invention, the laser treatment system is configured such that the distance A from the eye is variable and the target laser beam is focusable on at least one target structure ZS1 of the treated eye. The control unit determines the distance A1 from the position of the selected reference structure PRS relative to the reference plane RE and the position of the target structure PZS1 in the OCDR signal profile, respectively, and calculates the function ΔA using the parameters A1 and PZS1 for any selectable value of the change in distance ΔA of the laser treatment system from the eye.

[0116]

number

[0117] and approximately calculating respective possible focal positions PF of the laser beam of the laser therapy system in the OCDR signal profile. Preferably, the laser treatment system is adapted such that in addition to ZS1, the target laser beam is directed to N-1 further target structures ZS2, . . . , ZS n For this purpose, the control unit is configured to determine in the OCDR signal profile the respective positions PZS2, . . . , PZS n and the respective changes ΔA2, . . . , ΔA n Then, the parameters A1, ΔA2...ΔA N ,PZS1···PZSN Using the function

[0118]

number

[0119] from which it is possible to approximately calculate, for any selectable value of the change in distance ΔA of the laser treatment system from the eye, each possible focal position PF of the laser beam of the laser treatment system in the OCDR signal profile.

[0120] The first group of advantageous configurations concerns laser therapy systems. Thus, for example, as target laser beam, a therapeutic laser beam of a laser therapy system can be used, which has a reduced pulse energy that cannot cause photodissection. However, it is also possible to use an additional laser beam as target laser beam, which has parameters that do not allow permanent tissue changes in the eye.

[0121] Furthermore, the laser treatment system may comprise a plurality of target lasers that intersect at a focal point of a treatment laser of the laser treatment system and function to focus on a target structure ZS of the eye to be treated, where the continuous wave laser beam of the target laser preferably has the same or a similar focal point as the laser beam of the laser treatment system.

[0122] According to a further advantageous configuration, the laser treatment system itself is configured to generate target structures ZS in the eye. For example, this can be done by pulsing or modulating the target laser, which brings about a change in the eye and leads to a signal change in the OCDR or a change in the backscattering or a change in the phase or speckle grain in the OCDR signal. These target structures ZS can be temporary or changeable, for example, generated by at least one laser shot, leading to the formation of bubbles, or a temporarily changed speckle structure in the OCDR as a result of a temperature change.

[0123] According to a particularly advantageous configuration, the laser treatment system is configured for laser vitreolysis and generates a target structure ZS in the vicinity of the structure to be processed by means of a laser beam.

[0124] A second group of advantageous configurations relates to a control unit, which is configured to establish detection of focusing on the target structure by automatically establishing one or more of the following conditions:

[0125] Maximized backscattering of the target laser from the target structure Minimized diameter of the target laser beam light distribution on the target structure, and / or A characteristic state or characteristic change in the OCDR signal of the target structure The control unit is configured to determine the focal position as well as adjust the laser power using the target structure ZS generated by a laser shot of the laser beam of the laser treatment system.

[0126] Furthermore, the control unit may identify the positions of the target and reference structures, for example by determining a maximum or centroid value or a threshold value of the OCDR signal in the OCDR signal profile.

[0127] The control unit calculates a function for determining the focal position PF.

[0128]

number

[0129] As, we use polynomials of degree 1 through N, or different nonlinear functions with N degrees of freedom. However, it is also possible to use polynomials or non-linear functions of degree higher than N. To determine the function f, it is possible to additionally take into account parameters of the contact glasses determined elsewhere, such as the radius of curvature, thickness or refractive index, or additional parameters of the eye determined elsewhere, such as the refractive index, thickness or radius of the cornea or lens.

[0130] In particular, the control unit is configured so that the deviation in the approximate determination of the estimable focal position PF of the laser beam is less than 2 Rayleigh lengths of the laser focus, in particular less than 1 Rayleigh length, or particularly preferably less than 0.5 of the Rayleigh length.

[0131] A third group of advantageous configurations relates to an additionally provided camera system which detects the target laser and the target structure ZS. The control unit uses these images to determine the focusing, for example as follows:

[0132] Minimize the distance between target beam laser positions Minimizing the spatial variation of a periodically moving target laser beam, or Maximizing backscatter from at least one target beam laser focus A fourth group of advantageous configurations concerns additionally used contact glasses, the technical structures of which are located on the front or rear side or in the contact glasses themselves, serving as the reference structure RS.

[0133] In this case, the technical structure realized in the contact glass KG as the reference structure RS generates a characteristic signal in the OCDR with a specific level, plateau, curve, position, distance or multiple peaks of the signal or a characteristic polarization dependence. Preferably, the realized reference structure RS is modifiable, in particular switchable or modulatable, for example by a change in scattering or polarization.

[0134] Particularly preferably, the reference structure RS realized in the contact glasses KG operates in the invisible spectral range and is realized, for example, by a dielectric reflecting layer system, in particular configured in such a way that the target laser beam is reflected at wavelengths between 400 nm and 1050 nm and the treatment laser beam of the laser treatment system is mainly transmitted at wavelengths greater than 1050 nm.

[0135] A fifth group of advantageous configurations relates to an existing imaging system which can be focused, for example by means of an autofocus system, together with the laser beam of the laser treatment system on a number of target structures ZS.

[0136] Preferably, the NA of the imaging system and the NA of the laser beam of the laser treatment system differ by less than a factor of two. However, the laser beams of the imaging system and the laser therapy system may have certain focusing differences to compensate for the different wavelengths.

[0137] Preferably, the imaging system is configured to ensure a sufficiently large pupil diameter depending on the working depth. According to a particularly advantageous configuration, the imaging system is adapted to indicate the focal position estimated by the refocusing in relation to the eye structure prior to activation of the treatment laser.

[0138] A final group of advantageous configurations relates to OCDR systems. Preferably, the NA of the OCDR system and the NA of the laser beam of the laser treatment system differ by less than a factor of two.

[0139] Preferably, the wavelength of the OCDR system and the wavelength of the laser beam of the laser treatment system deviate from each other by no more than 10%. However, the laser beams of the OCDR system and the laser therapy system may also have certain focusing differences to compensate for different wavelengths.

[0140] The method and device according to the invention provide a solution for refocusing an ophthalmic laser treatment system, which corrects the shortcomings of known technical solutions and takes into account the individuality of the treated eye and the tolerances of the optical system when refocusing the treatment laser.

[0141] As a result, it is possible to accurately determine the focal position of the treatment laser for each new treatment situation, regardless of changes to the patient and / or contact glasses, or changes to the focal length of the treatment laser, accommodation, and / or especially the position of the patient's eye.

[0142] Furthermore, the proposed solution is easy to implement, cost-effective, and allows for easier, faster and above all safer eye laser treatment. The solution according to the invention makes it possible to reliably and precisely set blocked areas that can exclude laser treatment, which is particularly useful for systems for laser vitreolysis in order to protect and preserve sensitive eye structures.

[0143] The proposed solution is provided specifically for a treatment system for laser vitreolysis, but as mentioned above offers numerous other intraocular application options that would benefit from the proposed solution for refocusing a laser treatment system.

Claims

1. An apparatus for refocusing an ophthalmic system for intraocular laser treatment, comprising a treatment laser unit, an imaging unit, an optical system for focusing and beam overlapping, an OCDR system, and a control unit, wherein the laser treatment system is capable of changing a distance A to the eye, and the target laser beam is focused on at least one target structure ZS of the eye to be treated. １ The control unit is configured to be able to focus on a distance A from the position of the selected reference structure PRS relative to a reference plane RE. １ , and the target structure PZS in the OCDR signal profile １ and the control unit is further configured to determine the position of the parameter A for any selectable value of change in distance ΔA of the laser treatment system from the eye. １ and PZS １ and an apparatus configured to approximately estimate each estimable focal position PF of a laser beam of the laser therapy system in the OCDR signal profile using a signal profile information.

2. The control unit determines the determined value A １ and PZS １ to approximately calculate, for any selectable value of change in distance ΔA of the laser treatment system from the eye, each possible focal position PF of the laser beam of the laser treatment system in the OCDR signal profile using a function [Equation 1] 2. The apparatus of claim 1, configured to determine:

3. The laser treatment system is configured such that the target laser beam is ZS １ In addition to N-1 further target structures ZS ２ , ..., ZS ｎ , and for this purpose, the control unit is configured to detect in the OCDR signal profile the respective positions PZS of the target structure. ２ , ..., PZS ｎ and the first target structure ZS １ The initial position PRS when the focus is set to A １ The respective changes ΔA in the position of the reference structure relative to ２ , ..., ΔA ｎ Then, the parameter A １ , ΔA ２ ...ΔA Ｎ , PZS １ ...PZS Ｎ Using the function [Equation 2] 2. The apparatus of claim 1, wherein the apparatus is configured to determine a function from which each estimable focal position PF of the laser beam of the laser treatment system in the OCDR signal profile can be approximately calculated for any selectable value of change in distance ΔA of the laser treatment system from the eye.

4. 10. The apparatus of claim 1, wherein the laser therapy system is configured to use a treatment laser beam of the laser therapy system having a reduced pulse energy that is incapable of causing photoablation as the target laser beam.

5. The apparatus of any one of claims 1 to 4, characterized in that the control unit is configured to detect focusing on the target structure by visually or automatically detecting one or more of: 1) maximizing backscattering of the target laser from the target structure; 2) minimizing the diameter of the target laser beam light distribution on the target structure; and 3) detecting a characteristic state or characteristic change in the OCDR signal of the target structure.

6. The device of claim 1, wherein the laser treatment system includes multiple target lasers that intersect at the position of the focus of the treatment laser of the laser treatment system and function to focus on a target structure ZS of the eye to be treated, and a camera system is provided to detect the focusing of the multiple target lasers on the target structure ZS by minimizing the spacing of the target beam laser positions.

7. The device of claim 1 , wherein the laser treatment system itself is configured to generate the target structure ZS in the eye.

8. The device of claim 4, wherein the laser treatment system is configured to generate the target structure ZS in the eye by pulsing or modulating a target laser, and the target structure is a change in the eye that causes a signal change in OCDR, or a change in backscattering of the OCDR signal, or a change in phase or speckle grain.

9. 10. The device of claim 1 or 8, wherein the laser treatment system is configured to generate a temporary or changeable target structure ZS in the eye.

10. The device described in claim 9, wherein the temporary or changeable target structure ZS includes at least one of a gas bubble generated by at least one laser shot or a speckle structure of an OCDR that has temporarily changed as a result of a temperature change.

11. The device of claim 1, characterized in that the control unit is configured to use the target structure ZS generated by the laser shot of the laser beam of the laser treatment system to not only determine the focal position but also adjust the laser output.

12. 2. The device of claim 1, wherein the dielectric reflective layer system is configured such that the target laser beam is reflected at wavelengths between 400 nm and 1050 nm and the treatment laser beam of the laser treatment system is primarily transmitted at wavelengths greater than 1050 nm.

13. 10. The apparatus of claim 1, wherein the NA of the imaging system and the NA of the laser beam of the laser therapy system differ by less than a factor of two.

14. 10. The apparatus of claim 1, wherein the NA of the OCDR system and the NA of the laser beam of the laser therapy system differ by less than a factor of two.

15. 2. The device of claim 1, wherein the wavelength of the OCDR system and the wavelength of the laser beam of the laser therapy system deviate from each other by no more than 10%.

16. 4. The device according to claim 1 or 3, characterized in that the control unit is configured so that the deviation of the approximate determination of the estimable focal position PF of the laser beam is less than two Rayleigh lengths of the laser focus.

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