METHOD FOR DETERMINING A POSITION OF A LASER FOCUS OF A LASER BEAM OF AN EYE SURGICAL LASER, AS WELL AS TREATMENT APPARATUS

Abstract

A method is disclosed for determining a position of a laser focus of a laser beam of an eye surgical laser of a treatment apparatus by means of a control device of the treatment apparatus, in which the laser beam of the treatment apparatus is emitted into or onto a human or animal eye and in which at least two Purkinje images of the laser beam on the eye are captured by means of an optical capturing device of the treatment apparatus, and in which the position of the laser focus in or on the eye is determined by means of the control device considering the captured Purkinje images and considering an opening angle of the laser beam. Further disclosed are a treatment apparatus, a computer program and a computer-readable medium for carrying out the afore-mentioned method.

Claims

1. A method for determining a position of a laser focus of a laser beam of an eye surgical laser of a treatment apparatus by means of a control device of the treatment apparatus, comprising: emitting into or onto a human or animal eye the laser beam of the treatment apparatus; capturing by means of an optical capturing device of the treatment apparatus at least two Purkinje images of the laser beam on the eye; and determining by means of the control device considering the at least two captured Purkinje images and considering an opening angle of the laser beam, the position of the laser focus of the laser beam in or on the human or animal eye.

2. The method according to claim 1, wherein respective size of the at least two Purkinje images and a relative position of the at least two Purkinje images to each other are taken into account by means of the control device for determining the position of the laser focus.

3. The method according to claim 1, wherein least a first order first Purkinje image and a second order second Purkinje, which are captured at a respective interface of a cornea of the eye, are captured for determining the position of the laser focus.

4. The method according to claim 1, wherein third order third Purkinje image and/or a fourth order fourth Purkinje image, which are each captured at respective interfaces of a lens of the eye, are captured for determining the position of the laser focus.

5. The method according to claim 1, wherein working beam reduced in energy with respect to a treatment beam as the laser beam is emitted onto or into the eye as the laser beam for determining the position of the laser focus.

6. The method according to claim 1, wherein position of the laser focus is determined in regular time intervals during a treatment.

7. The method according to claim 1, wherein control of the laser for a working beam as the laser beam and/or a treatment beam as the laser beam is effected such that the laser emits laser pulses in a wavelength range between 100 nm and 1400 nm, at a respective pulse duration between 1 fs and 20 ns and a repetition frequency of greater than 1 kHz.

8. The method according to claim 1, wherein topographic and/or pachymetric and/or morphologic data of a cornea of the eye and/or of a lens of the eye is taken into account for determining the position of the laser focus.

9. The method according to claim 1, wherein at least two Purkinje images are captured by means of a capturing device formed as a camera.

10. A treatment apparatus with at least one eye surgical laser and with at least one control device for the laser or lasers, which is formed to perform the steps of the method according to claim 1.

11. The treatment apparatus according to claim 10, wherein the control device comprises at least one storage device for at least temporary storage of at least one control dataset, wherein the control dataset or datasets include control data for positioning and/or for focusing a laser beam into the eye; includes at least one beam device for beam guidance and/or beam shaping and/or beam deflection and/or beam focusing of a laser beam of the laser; and includes at least one optical capturing device or capturing at least two Purkinje images on the eye.

12. A computer program including instructions, which cause a treatment apparatus with at least one eye surgical laser and with at least one control device for the at least one eye surgical laser to execute the method steps according to claim 1.

13. A computer-readable medium, on which the computer program according to claim 12 is stored.

14. The method according to claim 7, wherein the wavelength range is between 700 nm and 1200 nm at the respective pulse duration of between 10 fs and 10 ps, and the repetition frequency of between 100 kHz and 10 MHz.

Description

[0027] FIG. 1 shows a schematic representation of a treatment apparatus according to the invention.

[0028] FIG. 2 shows a schematic side view of an eye of a patient.

[0029] In the figures, identical or functionally identical elements are provided with the same reference characters.

[0030] FIG. 1 shows a schematic representation of a treatment apparatus 10 with an eye surgical laser 12 for the treatment of a patient, in particular for the treatment of an eye 14 of a patient. For example, a predefined corneal volume or cornea volume can be removed as a volume body 16 with predefined interfaces for example by means of photodisruption by means of the eye surgical laser 12. One recognizes that a control device 18 for the laser 12 is formed besides the laser 12. This form of configuration with a control device 18 is to be purely exemplarily regarded. It can be provided that the treatment apparatus 10 also comprises a plurality, in particular more than two, of control devices 18. The control device 18 can for example emit pulsed laser pulses in a predefined pattern into a cornea 20 (FIG. 2), wherein the interfaces of the volume body 16 to be separated are generated by the predefined pattern for example by means of photodisruption. In the illustrated embodiment, the interfaces of the volume body 16 form a lenticular volume body 16, wherein the position of the volume body 16 is selected in this embodiment such that a pathological and/or unnaturally altered area within a stroma of the cornea 20 is enclosed.

[0031] Furthermore, one recognizes that the laser beam 22 generated by the laser 12 is deflected towards a surface 26 of the eye 14 by means of a beam deflection device 24, such as for example a scanner, in particular a so-called rotation scanner. The beam deflection device 24 is also controlled by the control device 18 to for example generate the mentioned predefined pattern in the cornea 20. For example, the beam deflection device 24 can comprise one or also two mirrors, which are formed for deflecting the impinging laser beam 22.

[0032] In the present embodiment, the illustrated laser 12 is a so-called photodisruptive laser. Presently, the laser 12 is in particular formed to emit laser pulses in a wavelength range between 100 nanometers and 1400 nanometers, in particular between 700 nanometers and 1200 nanometers, at a respective pulse duration between one femtosecond and 20 nanoseconds, in particular between ten femtoseconds and ten picoseconds, and a repetition frequency of greater than one kilohertz, in particular between 100 kilohertz and 100 megahertz. Alternatively, the laser 12 can also be formed as an ablation laser. Further, the laser beam 22 can be generated both as a working beam with a lower energy than a treatment beam and as a treatment beam itself

[0033] In addition, the control device 18 comprises a storage device 28 for at least temporary storage of at least one control dataset, wherein the control dataset or datasets include control data for positioning and/or for focusing individual laser pulses in or on the eye 14. The position data and/or focusing data of the individual laser pulses are generated based on a previously measured topography and/or pachymetry and/or the morphology of the eye 14 and the pathological and/or unnaturally altered area for example to be removed within the stroma of the eye 14.

[0034] FIG. 2 shows an eye 14 with the laser beam 22 in a purely schematic side view. Presently, the corresponding peripheral beams respectively opposing each other are in particular shown of the laser beam 22. The laser beam 22 has a laser focus 30, the position of which is presently formed in the cornea 20. An incision or a cavitation bubble for generating the volume body 16 is generated in the area of the laser focus 30. Thus, it is of crucial importance to reliably determine the position of the laser focus 30.

[0035] In the method for determining the position of the laser focus 30 of the laser beam 22 of the eye surgical laser 12 of the treatment apparatus 10 by means of the control device 18, the laser beam 22 of the treatment apparatus 10 is emitted onto or into the human or animal eye 14 and at least two Purkinje images 34, 36, 38, 40 of the laser beam 22 on the eye 14 are captured by means of an optical capturing device 32, in particular by means of a camera, of the treatment apparatus 10, and the position of the laser focus 30 in the eye 14, in particular in the cornea 20, is determined by means of the control device 18 considering the captured Purkinje images 34, 36, 38, 40 and considering an opening angle a, which is represented by means of the peripheral beams, of the laser beam 22.

[0036] Presently, a first order first Purkinje image 34 is shown. The first Purkinje image 34 is in particular generated by reflection, which is shown by the arrows 42, on an anterior interface 44 of the cornea 20. A second Purkinje image 36 is in particular a second order Purkinje reflection. The second Purkinje image 36 is generated at a posterior interface 46 of the cornea 20. A third Purkinje image 38 is in particular a third order reflection, wherein this reflection is in particular generated at an anterior interface 48 of a lens 50 of the eye 40. A fourth Purkinje image 40 is in particular a fourth order Purkinje reflection, which is in particular generated at a posterior interface 52 of the lens 50. In the present embodiment, the fourth Purkinje image 40 is in particular not completely reflected. As presently shown, the boundaries of the Purkinje images 34, 36, 38, 40 arise based on the respective peripheral beams of the laser beam 22.

[0037] For determining the position of the laser focus 30, it is in particular provided that a respective size of the at least two Purkinje images 34, 36, 38, 40 and a relative position of the at least two Purkinje images 34, 36, 38, 40 to each other are taken into account by means of the control device 18 for determining the position of the laser focus 30. Preferably, it can be provided that at least the first Purkinje image 34 and the second Purkinje image 36 are captured at the respective interfaces 44, 46 of the cornea 20 to determine the position of the laser focus 30. Additionally, or instead, the third Purkinje image 38 or the fourth Purkinje image 40 of the lens 50 can also be captured to contribute to the determination of the position of the laser focus 30. Any combinations of the Purkinje images 34, 36, 38, 40 are possible for determining the position of the laser focus 30. Preferably, the four Purkinje images 34, 36, 38, 40 are for example captured and the position of the laser focus 30 is determined depending thereon.

[0038] Further, it can for example be provided that a working beam reduced in energy with respect to a treatment beam as the laser beam 22 during a treatment is emitted to the eye 14 as the laser beam 22 for determining the position of the laser focus 30. Thereby, it is in particular allowed that generation of for example cavitation bubbles does not yet occur in the determination of the position of the laser focus 30, whereby a treatment itself is not yet performed in the determination of the position of the laser focus 30, but only the position of the laser focus 30 is determined without invasive intervention. For example, the energy of the working beam can be below the minimum energy for generating a cavitation bubble. Further, it can be provided that the determination of the position of the laser focus 30 is performed in regular time intervals during a treatment. In particular, it can for example be provided that a working beam reduced in energy is emitted in prescribed time intervals during the treatment to determine the position of the laser focus 30. In other words, it is changed between the treatment beam and the working beam with a lower energy such that the position of the laser focus 30 can be determined during the treatment itself

[0039] Further, it is in particular provided that topographic and/or pachymetric and/or morphologic data of the eye 14, in particular of the cornea 20 and/or of the lens 50, is taken into account for determining the position of the laser focus 30.

[0040] For determining the position of the laser focus 30, it can in particular be provided that the control device 18 determines the position of the laser focus 30 based on the law of refraction and the law of reflection as well as based on the Purkinje images 34, 36, 38, 40 and considering the opening angle α. Thereby, it is allowed that the position of the laser focus 30 in the material, in particular within the cornea 20 and/or the lens 50, can be directly determined. Thereby, the risk of an incorrectly positioned treatment can for example be minimized. In particular, non-meeting partial incisions can for example be prevented from being generated. For example, in case of lenticule incisions or in case of laser phacoemulsification or laser capsulotomy, partial incisions can be prevented from not meeting. Further, an injury of the endothelium can be prevented. An incorrect refraction by an incorrectly positioned femto flap or the volume body 16 can also be prevented.

[0041] Thus, by the relative pose and the shape/structure of the Purkinje images 34, 36, 38, 40 to each other, or also further reflections on the eye 14, and considering the opening angle a, the position of the laser focus 30 can in particular be determined, the pose of which is located in the three-dimensional space of the material to be processed, for example in the cornea 20 or the lens 50.

[0042] Overall, the Figs. show a determination of the position of the laser focus 30 based on Purkinje images 34, 36, 38, 40.