DE102011116760A1 - Ophthalmic laser system and method for the laser surgical treatment of the cornea - Google Patents

Abstract

Ophthalmic laser system and method for the laser surgical treatment of the cornea Known ophthalmic laser systems (1) with a detection beam path (D) comprising an optoelectronic detector (12) for detecting light, and a treatment beam path (B) comprising an ultrashort pulse laser (4) includes limited accuracy in the treatment of the cornea. This can be increased by a detector (12) for detecting light of exactly one variably adjustable state of polarization and in each case an adjustable beam deflection unit (7/7 ') in the two beam paths by recording stray light intensities of different polarization states from the same direction before treating the cornea and a model of a cornea is adapted to determine a cut geometry to be generated and to adapt it to a deformation predicted from the model. This allows surgical treatment of the cornea with high accuracy, taking into account the biomechanical state of the cornea, including its internal mechanical stresses in the incision. Ametropia correction

Description

The invention relates to an ophthalmic laser system having a treatment beam path comprising a pulse laser, and a detection beam path comprising an optoelectronic detector, and a method for laser surgical treatment of the cornea, in particular for the purpose of a refractive correction.

The cornea of the human eye has internal mechanical stresses. This tension structure can co-determine the shape of the cornea and thus cause, for example, defective vision.

Out WO 2009/127921 A2 For example, a system and method is known for altering the shape of the cornea by altering a voltage distribution of the cornea by cutting the tissue, first measuring the topography of the cornea. However, this way of altering the shape of the cornea has limited accuracy.

Optically, tension in the cornea is caused by birefringence of incident light. It was proposed to include these tensions in a refractive correction by means of an excimer laser in the calculation of the ablation profile (Alexander Bösecke: "In vivo optical stress analysis of the human cornea", Diploma thesis TU Ilmenau, 2007). This procedure has only a limited accuracy.

In DE 10 2006 016 968 A1 a reflective polariscope is indicated, which evaluates the backscattered light from the iris. However, this does not permit a depth-resolved analysis of birefringence in the cornea and is problematic for the pupil, as there is no backscattering of light.

The invention has for its object to provide an ophthalmic laser system of the type mentioned above, which allows a laser surgical treatment of the cornea with high accuracy, especially taking into account internal mechanical stresses of the cornea.

The object is achieved by an ophthalmic laser system having the features specified in claim 1, and by a method having the features specified in claim 12.

Advantageous embodiments of the invention are specified in the subclaims.

• – die Auswerteeinheit zur Durchführung folgender Schritte eingerichtet ist: 1. Einstellen des Detektors auf einen ersten Polarisationszustand und Ermitteln mindestens einer ersten Streulichtintensität mittels des Detektors, 2. Einstellen des Detektors auf einen zweiten Polarisationszustand, der von dem ersten Polarisationszustand verschieden ist und Ermitteln mindestens einer zweiten Streulichtintensität mittels des Detektors bei identischer Stellung der ersten Ablenkeinheit, 3. Ermitteln eines mathematischen Modells einer Cornea, welches eine Topographie und innere mechanische Spannungen beschreibt, und Anpassen an die ermittelten Streulichtintensitäten anhand unterschiedlicher Lichtausbreitungsgeschwindigkeiten für die zwei Polarisationszustände,
• – die Berechnungseinheit zur Durchführung folgender Schritte eingerichtet ist: 1. Ermitteln einer in der Cornea zu erzeugenden Schnittgeometrie und Anpassen durch Prognostizieren einer Verformung der Cornea anhand des angepassten Modells und 2. Ermitteln von Steuerdaten für einen Laserschnitt anhand der angepassten Schnittgeometrie und
• – die Steuereinheit zur Steuerung des Lasers, der ersten Ablenkeinheit und der Fokussieroptik anhand der Steuerdaten eingerichtet ist.

According to the invention, an ophthalmic laser system is provided with a detection beam path which comprises an optoelectronic detector for (depth-selective) detection of light of precisely a variably adjustable polarization state, a first variably adjustable beam deflection unit and a transfer optic, and a treatment beam path comprising an ultrashort laser second variably adjustable beam deflection unit and a focusing optics, as well as a control unit, a calculation unit and an evaluation unit, wherein

• - the evaluation unit is set up to carry out the following steps: 1. setting the detector to a first polarization state and determining at least a first scattered light intensity by means of the detector, 2. setting the detector to a second polarization state which is different from the first polarization state and determining at least one 3. determining a mathematical model of a cornea which describes a topography and internal mechanical stresses, and adapting to the determined scattered light intensities using different light propagation velocities for the two polarization states; second scattered light intensity by means of the detector;
• - the calculation unit is set up to: 1. determine a corneal geometry to be cut and adjust by predicting cornea deformation using the fitted model; and 2. determine laser cut control data based on the fitted cut geometry and
• - The control unit for controlling the laser, the first deflecting unit and the focusing optics is set up based on the control data.

Expediently, first and second scattered light intensities are determined from different directions by the cornea by setting the first deflection unit differently and determining, for each position, first and second scattered light intensities having different polarization states. As a result, a three-dimensional model can be determined and adapted, which allows a higher accuracy.

For the purposes of the invention, an ultrashort pulse laser is a laser capable of emitting radiation pulses with a duration in the fs or ps range. Mechanical stresses are preferably internal stresses in the corneal tissue.

• 1. tiefenselektives Ermitteln mindestens einer ersten Streulichtintensität mit einem ersten Polarisationszustand aus einer ersten Richtung von der Cornea,
• 2. tiefenselektives Ermitteln mindestens einer zweiten Streulichtintensität mit einem zweiten Polarisationszustand, der von dem ersten Polarisationszustand verschieden ist, aus derselben Richtung,
• 3. Ermitteln eines mathematischen Modells einer Cornea, welches eine Topographie und innere mechanische Spannungen beschreibt, und Anpassen an die ermittelten Streulichtintensitäten anhand unterschiedlicher Lichtausbreitungsgeschwindigkeiten für die zwei Polarisationszustände,
• 4. Ermitteln einer in der Cornea zu erzeugenden Schnittgeometrie und Anpassen durch Prognostizieren einer Verformung der Cornea anhand des angepassten Modells und
• 5. Ermitteln von Steuerdaten für einen Laserschnitt anhand der angepassten Schnittgeometrie und
• 6. Steuern des Lasers, der ersten Ablenkeinheit und der Fokussieroptik anhand der Steuerdaten.

Accordingly, for the inventive method for laser surgery a Cornea by means of an ultrashort pulse laser intended to perform the following steps:

• 1. deep-selective determination of at least one first scattered light intensity having a first polarization state from a first direction of the cornea,
• 2. depth-selective determination of at least one second scattered light intensity having a second polarization state, which is different from the first polarization state, from the same direction,
• 3. Determining a mathematical model of a cornea, which describes a topography and internal mechanical stresses, and adapting to the determined scattered light intensities using different light propagation velocities for the two polarization states,
• 4. Determine a cut geometry to be created in the cornea and adjust by predicting a corneal deformation based on the fitted model and
• 5. Determine control data for a laser cut based on the adjusted cutting geometry and
• 6. Controlling the laser, the first deflection unit and the focusing optics based on the control data.

A determination of scattered light intensities is highly selective in the sense of the invention if scattered light intensities from different depths of the cornea can be recorded with depth resolution either simultaneously or sequentially.

The invention allows surgical treatment of the cornea with high accuracy by taking into account the biomechanical state of the cornea, including its internal mechanical stresses in the incision. As a result, both the spatial control parameters (position of the irradiated target volumes) and energetic control parameters (pulse intensities) can be determined with high accuracy. The evaluation unit, the calculation unit or the control unit can output the voltages determined on the basis of the model such that they can be visually perceived by an operator. In particular, the unit in question may receive instructions from the operator to modify the model.

The mechanical model can, for example, according to US 2009/0187386 A1 be composed of finite elements whose position and mechanical stresses, starting from a standard cornea model by a compensation calculation to the topography data of the concretely measured cornea and the intensities of the birefringence differently refracted scattered light are adjusted.

The direction from the cornea, from which the scattered light intensities are determined, defines from which location in the cornea the detected scattered light is recorded. Thus, at least one first scattered light intensity, which (exclusively) has the first polarization state, and at least one second scattered light intensity, which (exclusively) has the second polarization state, is determined from a location. Preferably, first and second scattered light intensities can be determined from a plurality of different locations of the cornea. For this purpose, the direction from the cornea, from which the scattered light intensities are determined, can be adjusted, for example, by means of an adjustable beam deflection unit. In turn, first and second scattered light intensities can then be recorded by the new location. By measuring multiple locations, a three-dimensional model can be identified and adjusted, allowing greater accuracy. In addition, third and further scattered light intensities can be determined for additional polarization states and used in the adaptation.

In an advantageous embodiment, the evaluation unit determines a topography of the cornea from the scattered light intensities in order to adapt the model to the light intensities. This improves the accuracy of the model and eliminates the need to separately survey the topography.

In an alternative embodiment, the laser system comprises a topography measuring device, wherein the evaluation unit is set up to adapt the model to topographical data of the cornea determined or predefined by means of a topography measuring device before adaptation to the light intensities. Also in this way the accuracy of the model can be improved.

• – Beleuchten einer in einem Untersuchungsbereich angeordneten Cornea mittels der Lichtquelle und
• – Fokussieren des Detektionsstrahlengangs auf die Cornea.

Dadurch kann die Genauigkeit der Messung der Streulichtintensitäten verbessert werden, insbesondere durch eine konfokale Beleuchtung.Expediently, an illumination beam path can be coupled into the detection beam path with a light source and the evaluation unit can be set up to carry out the following steps before determining the first scattered light intensity:

• Illuminating a cornea arranged in an examination area by means of the light source and
• - Focusing the detection beam path on the cornea.

Thereby, the accuracy of the measurement of the scattered light intensities can be improved, in particular by a confocal illumination.

Particularly advantageous embodiments are those in which the detection beam path has a (intentional) optics, which light of the light source, the is directed by the first deflection on the cornea, regardless of a position of the first deflector perpendicular to the cornea directs, in particular with the arrangement of the optics on a side facing away from the laser side of the transfer optics. Such an attachment optics can be, for example, a diffractive or refractive element and consist of a lens or a lens combination. Their focal length preferably corresponds to their distance from the cornea plus about 8 mm, so for example 20 mm. The vertical incidence of the illumination light and the vertical detection at each location of the cornea simplify the adaptation of the model, since the birefringence thus takes place only along a minimum path length through the cornea.

• – Aktivieren einer Fixiervorrichtung an der Cornea vor dem Steuern des Lasers und
• – Desaktivieren der Fixiervorrichtung nach dem Steuern des Lasers.

So kann die Gefahr von Fehlbehandlungen durch Augenbewegungen minimiert werden.The control unit is expediently designed to carry out the following steps:

• - Activating a fixation device on the cornea before controlling the laser and
• Deactivate the fixing device after controlling the laser.

Thus, the risk of mistreatment by eye movements can be minimized.

• – Aktivieren einer verformenden Fixiervorrichtung in Kontakt mit der Cornea vor dem Ermitteln der Streulichtintensitäten und
• – Desaktivieren der Fixiervorrichtung nach dem Ermitteln der Streulichtintensitäten.

Dadurch können die Spannungszustände der Cornea in einem definiert verformten Zustand der Cornea gemessen werden. Die Verformung kann beispielsweise ein Applanation durch ein planes Kontaktglas sein. Vorteilhafterweise kann eine Messung von Lichtintensitäten mit unterschiedlichen Polarisationszuständen ohne äußere Verformung und vorher oder hinterher eine entsprechende Messung mit äußerer Verformung durchgeführt werden und die Lichtintensitäten aus beiden Messungen bei der Anpassung des Modells verwendet werden. Zu diesem Zweck kann beispielsweise in dem Modell dieselbe definierte Verformung simuliert werden. Durch Berücksichtigung einer definierten Verformung kann die Festigkeit der Cornea mit höherer Genauigkeit ermittelt werden.Embodiments in which the evaluation unit is set up to carry out the following steps are particularly advantageous:

• - Activating a deforming fixing device in contact with the cornea before determining the scattered light intensities and
• Deactivate the fixing device after determining the scattered light intensities.

Thereby, the stress states of the cornea can be measured in a defined deformed state of the cornea. The deformation may be, for example, a applanation through a plane contact glass. Advantageously, a measurement of light intensities with different states of polarization without external deformation and before or after a corresponding measurement with external deformation can be carried out and the light intensities from both measurements can be used in the adaptation of the model. For this purpose, for example, the same defined deformation can be simulated in the model. By taking into account a defined deformation, the strength of the cornea can be determined with higher accuracy.

• – das Anpassen des mathematischen Modells an die ermittelten Streulichtintensitäten von der Berechnungseinheit oder der Steuereinheit durchgeführt wird und/oder
• – das Ermitteln und Anpassen der Schnittgeometrie von der Auswerteeinheit oder der Steuereinheit durchgeführt wird.

The invention includes embodiments in which

• The adaptation of the mathematical model to the determined scattered light intensities is carried out by the calculation unit or the control unit and / or
• - The determination and adjustment of the cutting geometry is performed by the evaluation unit or the control unit.

Preferably, the detector is an optical coherence tomograph (OCT) or designed to confocal with the second focusing optic detection. These detectors allow depth discrimination with high axial resolution. A system with a confocal detector can, for example, according to 3 of the WO 2010/07020 A2 be formed with other programming of the local control unit, the disclosure of which is incorporated here in full. A system with an OCT as a detector can, for example, according to 5 or 6 of the WO 2009/033111 A2 be formed with other programming of the local control units.

The evaluation unit can advantageously determine a length of the eye and a thickness of the lens on the basis of the determined scattered light intensities. Based on these data, a cataract operation can be performed in the same treatment, for example in the form of an anterior or posterior capsulorhexis by means of the ultra-short pulse laser, the destruction of the biological lens or irradiation of the epithelial cells arranged equatorially in the capsular bag.

• – die Auswerteeinheit, die Berechnungseinheit und die Steuereinheit dieselbe Einheit sind und/oder
• – die erste und zweite Ablenkeinheiten dieselbe Ablenkeinheit sind und/oder
• – die Transferoptik und die Fokussieroptik dieselbe Optik sind.

The invention includes embodiments in which

• The evaluation unit, the calculation unit and the control unit are the same unit and / or
• The first and second deflection units are the same deflection unit and / or
• - The transfer optics and the focusing optics are the same look.

The invention also encompasses an OCT which determines a topography of the cornea, either by means of topographical data measured by means of an integrated topography measuring device (for example using Placidoringen) or by means of topographical data determined from the measured OCT intensities. In embodiments with or without topography determination, an OCT according to the invention can determine the stresses within a cornea on the basis of scattered light intensities of different polarization states. Such an OCT can be used in particular in the abovementioned applications in preliminary and / or follow-up examinations.

In addition, the invention comprises an ophthalmological measuring device for recording scattered light from a cornea, having an illumination beam path comprising a light source, and a detection beam path coupled to the illumination beam path, comprising an optoelectronic detector for (depth-selective) detection of light of precisely a variably adjustable polarization state, a variably adjustable jet Deflection unit and a transfer optics comprises, wherein the common behind the coupling point beam path is characterized by an optics, which directs light from the light source, which is directed by means of the deflection on the cornea, regardless of a position of the deflection perpendicular to the cornea, in particular with arrangement of Optic between the coupling point and a closing element to the outside, for example, a glass.

• – Bei biomechanikabhängige Behandlungen der Cornea, insbesondere innerhalb einer Katarakt-Operation (für limbale Relaxationsschnitte oder transparente Corneaschnitte).
• – Bei der Extraktion eines refraktiven Lentikels (ReLEx) zur Verbesserung der Behandlungsgenauigkeit (Vermeidung von Unterschieden bei der Korrektur höhere Ordnungen von Abbildungsfehlern durch unterschiedliche Spannungszustände zwischen fixiertem und unfixiertem Zustand der Cornea) und -effizienz und auch vorab zu Patientenauswahl insbesondere durch Ermittlung eines Eignungswertes anhand der ermittelten mechanischen Spannungen oder weiterer biomechanischer Eigenschaften.
• – Zur Behandlungsplanung bei einer Keratoplastik, beispielsweise zur Festlegung der Keratoplastie-Zone.
• – Bei refraktiven Behandlungen wie Femtosekunden-LASIK oder innerhalb einer Katarakt-Operation (jeweils für limbale Relaxationsschnitte, transparente Corneaschnitte und/oder zur Reduktion von kornealem Astigmatismus).
• – Zur Vermeidung oder Behandlung von Keratokonus.
• – ICR-Implantation: Zur Auswahl der ICR und/oder Optimierung der ICR-Position.

The invention can be used in particular in the following applications:

• - For biomechanically dependent treatments of the cornea, especially within a cataract operation (for limbal relaxation incisions or transparent corneal incisions).
• - In the extraction of a refractive lenticle (ReLEx) to improve the accuracy of treatment (avoiding differences in the correction of higher orders of aberrations due to different voltage states between fixed and unfixed state of the cornea) and efficiency and also in advance to patient selection in particular by determining a fitness value the determined mechanical stresses or other biomechanical properties.
• - For treatment planning in a keratoplasty, for example, to determine the keratoplasty zone.
• - For refractive treatments such as femtosecond LASIK or cataract surgery (for limbal relaxation incisions, transparent corneal incisions and / or to reduce corneal astigmatism).
• - To prevent or treat keratoconus.
• - ICR implantation: To select the ICR and / or optimize the ICR position.

The invention will be explained in more detail by means of exemplary embodiments.

In the drawings show:

1 a first laser system consisting of a measuring device, a calculating device and an irradiation device,

2 a second laser system in which the three devices are combined in one and

3 a flowchart of a method for laser surgical treatment of the cornea.

In all drawings, like parts bear like reference numerals.

1 shows a schematic representation of an ophthalmic laser system 1 consisting of separate devices, namely a measuring device 1.1 , a calculation device 1.2 and an irradiation device 1.3 , which are interconnectable via interfaces for data transmission. They can also stay connected permanently. For carrying out the method according to the invention, the patient's eye 2 first to measure the cornea 3 in the examination area in front of the measuring device 1.1 placed and later for irradiation in the treatment area in front of the irradiation device 1.3 ,

The measuring device 1.1 includes a detector 12 For example, spectral space OCT (OCT) associated with a polarization beam splitter 5 and one, for example, motor defined around the optical axis of the system 1 rotatable λ / 2 plate 15 is adjustable polarization discriminating, a scanning optics 6 , an xy deflector 7 ("scanner unit"), an example z-focusable transfer optics 8th and a graduation glass 9 which together form a detection beam path D leading to the examination area. In the detection beam D is by means of the beam splitter 5 a lighting beam C coupled, in which a light source 10 is arranged, which emits unpolarized IR light. Between the laser system 1 and the eye 2 is an attachment optics 13 All arranged on the cornea 3 focused rays, regardless of their angle of incidence perpendicular to the cornea 3 directs. The detector 12 accordingly receives in the reverse direction stray light from the cornea 3 and converts its intensity into a digital size that is sent to the evaluation unit 11.1 is issued. By means of the deflection unit 7 and the transfer optics 8th can the evaluation unit 11.1 the direction from which light from the cornea 3 is set, adjust. It can also be the light source 10 in terms of emitted intensity and wave plate 15 in terms of the only one to the detector 12 transmit polarization state (here: the polarization direction).

As soon as the practitioner has triggered the measurement, the evaluation unit switches 11.1 the light source 10 and sets the detector 12 to a first state of polarization by the wave plate 15 rotates accordingly and by means of the deflection unit 7 a first direction of incidence for light from the cornea 3 established. Then it simultaneously determines first intensities of in different Depths in the cornea backscattered illumination light from the first direction. In alternative embodiments, for example with a confocal detector or with space-time OCT as the detector, the determination can be performed sequentially from different depths. Then she sets the deflection unit 7 to another direction of incidence of the cornea 3 backscattered light. Then, it simultaneously detects further first intensities of illumination light backscattered at different depths in the cornea from the second direction. This scanning is repeated for a variety of incident directions. No stray light is scattered by the retina into the detection beam path D because it lies outside the coherence range of the OCT. In alternative embodiments (not shown) with confocal detection, the retina is outside the confocal area.

Then the evaluation unit stops 11.1 the detector 12 to a second polarization state, which is different from the first polarization state, by the wave plate 15 rotates to another position, for example, 90 °, and provides the deflection unit 7 For example, again in the first (incidence) direction. It then simultaneously detects second intensities of illumination light backscattered at different depths in the cornea from the first direction of the cornea.

Then she sets the deflection unit 7 for example, on the second direction of incidence of the cornea 3 one. Then, it simultaneously detects further second intensities of illuminating light backscattered at different depths in the cornea from the second direction. This scanning is repeated, for example, for all previously set directions of incidence.

Once all first and second scattered light intensities have been determined, the evaluation unit determines 11.1 a mathematical (standard) model of a cornea 3 which describes a topography and mechanical stresses, for example, by taking it from the calculation unit 112 answers. It adjusts the model to the detected scattered light intensities using different light propagation velocities for the two polarization states. For this purpose, for example, it can simulate the birefringence of light under the measured directions of incidence by means of ray tracing ("ray tracing") and perform a compensation calculation with ray tracing parameters.

The calculation device 1.2 is as a calculation unit 11.2 For example, a commercial computer with a central processing unit, a working memory and a display, via two interfaces on the one hand with the evaluation 11.1 and on the other hand with the control unit 11.3 connected is. The calculation unit 11.2 can the evaluation unit 11.1 For example, data for adjusting the patient-customized model of the cornea 3 specify, for example, an intraocular pressure and general mechanical properties of the cornea 3 , This data can be the calculation unit 11.2 for example, by a practitioner via an input device to receive or read from a database.

From the evaluation unit 11.1 takes the calculation unit 11.2 the patient-customized model contrary. It first determines a cut geometry to be generated in the cornea, for example by receiving it from the practitioner or from a database, and adapts it on the basis of this model by predicting a deformation of the cornea on the basis of the customized model of the cornea 3 iteratively until a predetermined target criterion, for example a predetermined refractive effect or a given topography, is reached. The calculation unit then determines 11.2 Control data for a laser cut based on the previously adapted cutting geometry and passes this to the control unit 11.3 out.

The irradiation device 1.3 includes next to the control unit 11.3 an ultrashort pulse laser 4 For example, a Yb fiber laser scanning optics 6 , a second xy deflection unit 7 ' ("scanner unit"), a z-focusing optics 8th' and a graduation glass 9 , which together form a treatment beam path B, which is the treatment area of the device 1.3 leads. Between the laser system 1 and the eye 2 is a fixing device 14 with a contact lens for the eye 2 arranged. The contact glass can be at his the eye 2 facing side have a spherical, a plane, an eye-like curved or another about the optical axis rotationally symmetric surface. For example, it is a spherical curvature in which the cornea 3 is applanated in the fixed (eg aspirated) state.

The control unit 11.3 takes the control data from the calculation unit 11.2 contrary, fixed on a signal from the practitioner's eye 2 in the fixing device 14 and controls the laser 4 , the deflection unit 7 ' and the focusing optics 8th' based on this control data so that the adjusted laser cut in the cornea 3 is produced. Then it releases the fixing device 14 , Finally, the practitioner removes the separated by means of the radiation pulses tissue.

Instead of the combination of polarization beam splitter 5 and wave plate 15 Any other adjustable polarization-selective element can be used. For example, it is possible to determine the first scattered light intensities in a linear polarization state and the second scattered light intensities to determine a circular polarization state. In alternative embodiments (not shown), the detection beam path can be designed fiber-optically. The setting of the respectively to be detected polarization state can then be done for example via variable fiber optic elements.

In alternative embodiments (not shown), the attachment optics 13 within the measuring device 1.1 be arranged, for example between the transfer optics 8th and the graduation glass 9 ,

In 2 is schematically an alternative laser system 1 represented in which all three devices are combined in one. The mode of operation corresponds to that too 1 described so far nothing else is described below. The detection beam D is by means of the polarization beam splitter 5 coupled into the treatment beam path B, which serves as the illumination beam C at the same time by a Strahlabschwächer 17 in the treatment beam B can be pivoted. In the swung-in state, the laser can 4 as a light source 10 Serve in the swung out state, it serves to edit the cornea 3 , The control unit 11 is at the same time evaluation calculation unit. This can for example be realized by appropriate software modules that interact with each other via interfaces.

3 shows the sequence of a method according to the invention in the form of a flow chart. It is divided by the individual units 11.1 . 11.2 and 11.3 executed, but may for example also by the combined control unit 11 be executed.

First, the first and second scattered light intensities for different polarization states and by means of the deflection unit 7 from different directions of the cornea, ie from different locations of the cornea, determined. Optionally, in alternative embodiments (not shown), the topography of the cornea can be measured by means of a topography measuring device, which is coupled into the detection beam path, for example, and provided in the form of topographical data. Alternatively, topography data can be obtained, for example, from the means of the detector 12 determined scattered light intensities are determined. Appropriately, in this way, a thickness of the cornea 3 (Pachymetry).

A predefined mechanical model of a general cornea is determined according to the thickness of the cornea and adapted to the topography on the basis of the topographical data and based on the determined scattered light intensities due to birefringence to the mechanical stresses, for example by means of a finite element method (FEM) and a simulation of ray tracing in the model with different light propagation velocities for the two polarization states. To adapt the model, for example, a predetermined intraocular pressure and given general mechanical properties are used.

The FEM model comprising the topography and the mechanical stresses is then used to iteratively optimize a given cutting geometry by means of a compensation calculation. For this purpose, the cut is simulated in the patient-specific adapted model and a deformation of the model is simulated in accordance with the determined mechanical stresses. Then a deviation of the model from a given target criterion (refractive effect or topography) is determined. If the deviation is greater than a predefined threshold value, the cutting geometry is modified and simulated in the original patient-specific adapted model and a deformation is determined. These iterations continue until the threshold is exceeded. If this goal is not achieved, the procedure is aborted.

If an optimized cutting geometry could be determined, appropriate control data is determined, the spatial control data for a deflection unit 7 ' and a focusing unit 8th' include, for example, to generate gas bubble fields by means of optical breakthroughs as cut surfaces. The patient must have his eye 2 then place in the treatment area. By means of an ultrashort pulse laser 4 and the deflection unit 7 ' and the focusing unit 8th' Radiation pulses are entered into target volumes V, which cause the precalculated optical breakthroughs in the target volumes V.

LIST OF REFERENCE NUMBERS

1

Ophthalmic laser system

1.1

measuring device

1.2

calculator

1.3

irradiator

2

eye

3

cornea

4

Ultra short pulse laser

5

Polarization beam splitter

6

scan optics

7 ( ')

scanning

8th

transfer optics

8th'

focusing optics

9

cover glass

10

light source

11

Evaluation, calculation and control unit

11.1

evaluation

11.2

calculation unit

11.3

control unit

12

detector

13

optical head

14

fixing

15

λ / 2 plate with drive

16

Optical delay element

17

Beam attenuator with drive

B

Treatment beam path

C

Illumination beam path

D

Detection beam path

R

OCT reference beam path

V

target volume

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2009/127921 A2 [0003]
• DE 102006016968 A1 [0005]
• US 2009/0187386 A1 [0015]
• WO 2010/07020 A2 [0024]
• WO 2009/033111 A2 [0024]

Claims (14)

Ophthalmic laser system ( 1 ) with a detection beam path (D) which has an optoelectronic detector ( 12 ) for detecting light of exactly one variably adjustable polarization state, a first variably adjustable beam deflection unit ( 7 ) and a transfer optics ( 8th ) and a treatment beam path (B), which is an ultrashort pulse laser ( 4 ), a second variably adjustable beam deflection unit ( 7 ' ) and a focusing optics ( 8th' ) and a control unit ( 11 [.3] ), a calculation unit ( 11 [.2] ) and an evaluation unit ( 11 [.1] ), where - the evaluation unit ( 11 [.1] ) is set up to carry out the following steps: 1. Setting the detector ( 12 ) to a first polarization state and determining at least a first scattered light intensity by means of the detector ( 12 ), 2. Setting the detector ( 12 ) to a second polarization state, which is different from the first polarization state, and determining at least a second scattered light intensity by means of the detector ( 12 ) and 3. determining a mathematical model of a cornea which describes a topography and mechanical stresses, and adapting to the determined scattered light intensities using different light propagation velocities for the two polarization states, - the calculation unit ( 11 [.2] ) for the following steps: 1. determining a corneal geometry to be cut and fitting by predicting corneal deformation based on the fitted model; and 2. determining laser cut control data based on the adjusted geometry of the cut and - the control unit ( 11 [.3] ) for controlling the laser ( 4 ), the second deflection unit ( 7 ' ) and the focusing optics ( 8th' ) is set up based on the control data. Laser system ( 1 ) according to claim 1, wherein the evaluation unit ( 11 [.1] ) to adapt the model to the light intensities a topography of the cornea from the scattered light intensities determined. Laser system ( 1 ) according to claim 1, comprising a topography measuring device, wherein the evaluation unit ( 11 [.1] ), the model, before adaptation to the light intensities, is determined by means of a topography measurement device or predetermined topography data of the cornea (FIG. 3 ). Laser system ( 1 ) according to one of the preceding claims, wherein in the detection beam path (D) an illumination beam path (C) with a light source ( 10 ) and the evaluation unit ( 11 [.1] ) is set up to carry out the following steps before determining the first scattered light intensity: illuminating a cornea arranged in an examination area ( 3 ) by means of the light source ( 10 ) and - focusing the detection beam path (D) on the cornea ( 3 ). Laser system ( 1 ) according to the preceding claim, wherein the detection beam path (D) is optics ( 13 ), which light of the light source ( 10 ), which by means of the first deflection unit ( 7 ) on the cornea ( 3 ), regardless of a position of the first deflection unit ( 7 ) perpendicular to the cornea ( 3 ), in particular with arrangement of the optics on one of the laser ( 4 ) facing away from the transfer optics ( 8th ). Laser system ( 1 ) according to one of the preceding claims, wherein the control unit ( 11 [.3] ) is arranged to carry out the following steps: activating a fixing device ( 14 ) on the cornea before controlling the laser ( 4 ) and - deactivating the fixing device ( 14 ) after controlling the laser ( 4 ). Laser system ( 1 ) according to one of the preceding claims, wherein the evaluation unit ( 11 [.1] ) is arranged to carry out the following steps: activating a deforming fixing device ( 14 ) in contact with the cornea before determining the scattered light intensities and - deactivating the fixing device ( 14 ) after determining the scattered light intensities. Laser system ( 1 ) according to one of the preceding claims, wherein - the adaptation of the mathematical model to the determined scattered light intensities by the calculation unit ( 11.2 ) or the control unit ( 11.3 ) is carried out and / or - the determination and adaptation of the cutting geometry of the evaluation unit ( 11.1 ) or the control unit ( 11.3 ) is carried out. Laser system ( 1 ) according to one of the preceding claims, wherein the detector ( 12 ) is an optical coherence tomograph or with the focusing optics ( 8th' ) Confocal detection is formed. Laser system ( 1 ) according to one of the preceding claims, wherein the evaluation unit ( 11 [.3] ) on the basis of the determined scattered light intensities a depth of an anterior chamber of the eye ( 2 ), a length of the eye ( 2 ) and a thickness of the lens of the eye ( 2 ). Laser system ( 1 ) according to one of the preceding claims, wherein the evaluation unit ( 11.1 ), the calculation unit ( 11.2 ) and the control unit ( 11.3 ) the same unit ( 11 ) and / or wherein the first and second deflection units ( 7 . 7 ' ) the same deflection unit ( 7 ) and / or wherein the transfer optics ( 8th ) and the focusing optics ( 8th' ) the same look ( 8th ) are. Method for laser-surgical processing of a cornea, in particular for the purpose of a refractive correction, by means of an ultrashort pulse laser, comprising the following steps: 1. deep-selective determination of at least a first scattered light intensity with a first polarization state from a first direction of the cornea, 2. depth-selective determination of at least one 3. Determining a mathematical model of a cornea, which describes a topography and mechanical stresses, and adapting to the determined scattered light intensities by means of different light propagation velocities for the two polarization states. The second scattered light intensity has a second polarization state, which is different from the first polarization state, from the same direction. 4. Determine a cut geometry to be created in the cornea and adjust by predicting a cornea deformation based on the fitted model and determining control data for a laser cut based on the adjusted cutting geometry and 6. controlling the laser ( 4 ), the first deflection unit ( 9 ) and the focusing optics ( 8th ) is set up based on the control data. Method according to the preceding claim, wherein - to adapt the model to the light intensities, a topography of the cornea is determined from the scattered light intensities, or - before the model is adapted to the light intensities, the model is adjusted to predetermined or topographical data of the cornea ( 3 ) is adjusted. Method according to one of the preceding method claims, wherein the cornea ( 3 ) before determining the scattered light intensities by means of a fixing device ( 14 ) is deformed, in particular with additional determination of first and second scattered light intensities before the deformation of the cornea and / or after an end of the deformation.

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