Treatment device for correcting the refraction of an eye, method for generating control data, and treatment method
Patent Information
- Application Number
- PCT/EP2026/055124
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-02-28
- Filing Date
- 2026-02-25
- Publication Date
- 2026-09-03
Smart Images
Figure EP2026055124_03092026_PF_FP_ABST
Abstract
Description
[0001] patent attorneys
[0002] GEYER, FEHNERS & PARTNER
[0003] Munich - Jena
[0004] Carl Zeiss Meditec AG
[0005] Attorney's file: PAT 9030 / 264-PCT
[0006] Treatment device for correcting the refraction of an eye, method for generating control data and treatment procedure
[0007] The invention relates to a treatment device for correcting the refraction of an eye by creating at least one cross-sectional area within the cornea of the eye, wherein a scanning device adjusts the focus of a laser beam three-dimensionally along a path within the eye. The invention also relates to a method for generating control data for such a treatment device. The invention further relates to a treatment method for correcting the refraction of an eye, in which a cross-sectional area is created within the cornea of the eye, wherein the focus of a laser beam is adjusted three-dimensionally along a path within the eye.
[0008] The shape of the anterior surface of the cornea is crucial for the eye's imaging properties. Therefore, it has long been known to modify the cornea to correct refractive errors, with the aim of altering its anterior surface and thus its refractive properties, thereby compensating for the refractive error. Prior art surgical procedures have been developed for this purpose, which, in many applications, use pulsed laser radiation to isolate and then extract material from within the cornea, i.e., beneath the corneal surface. This material, as a tissue fragment, is typically lenticule-shaped, hence the established term lenticule extraction. The volume of visual clarity to be isolated and extracted is also referred to as a "lenticule," even when, in certain applications, a non-lenticule-shaped volume needs to be isolated and extracted.The incised surfaces inside the cornea that isolate the lenticule determine the correction that is achieved.
[0009] The lenticular-extracting approach, which has become the standard for modern refractive correction with the VISUMAX treatment device from Carl Zeiss Meditec AG, has the advantage that the front surface of the cornea is only very slightly damaged.
[0010] Lenticule-extracting refractive error correction is fundamentally described in WO 2004 / 105660 A1 and WO 2004 / 105661 A1. Further developments are known in the prior art. For example, WO 2005 / 011547 A1 discloses the use of contour lines for rapid lenticule isolation, and WO 2008 / 055697 A1 provides calculation rules for how the lenticule interfaces, i.e., the generating cut surfaces, can be selected.
[0011] GEYER, FEHNERS & PARTNER
[0012] Munich - Jena
[0013] 2 WO 2008 / 055 705 A1 and WO 2008 / 055706 A1 deal with the generation of control data for the treatment device.
[0014] The cut surface is typically generated by focused laser radiation. The laser beam's focus is guided along a trajectory that lies within the cut surface and ultimately defines its shape. WO 2008 / 055698 A1 describes the arrangement of target points for pulsed laser radiation along this trajectory.
[0015] Spiral scans are known for isolating the lenticule, for example from US 5 984916 A and DE 102011 085047 A1 .
[0016] WO 2017 / 005815A1 describes an ophthalmological therapy setup that uses focused radiation to alter tissue. This setup employs multiple scanners, with a scanner pair in each of the three spatial directions x, y, and z. Each pair consists of a slow scanner combined with a fast scanner. The fast scanner in each spatial direction is synchronized with the operation of the slow scanner and can, in particular, perform harmonic oscillations. The aforementioned document utilizes this to construct sections, which are essentially ring-shaped and parallel to the z-axis, by arranging individual, obliquely positioned path segments (referred to as strokes).
[0017] Depending on the patient's condition and the available technology, the shape of the lenticule is individually adapted to achieve the best possible visual result.
[0018] In the context of lenticule extraction treatment, deviations from ideal visual acuity are described by so-called aberrations. These can be mathematically described using Zernike polynomials, as described, for example, in the entry "Zernike polynomials" on the English Wikipedia. Zernike polynomials Z m n The polynomials are essentially distinguished by their two indices, m and n, which are non-negative integers such that n > m. Hereafter, the polynomials will also be denoted as Z(m, n). It can be said that the more pronounced the underlying aberration, the higher the order (m, n) of the Zernike polynomials used for its mathematical description. Alternatively, aberrations can also be described by a Fourier decomposition. This leads to a comparable approach.
[0019] The known methods of lenticule extraction allow only a limited range of treatment options – limited in terms of the correctable aberrations. Essentially, the treatment scope is restricted to spherical, astigmatic, and [patent attorneys']
[0020] GEYER, FEHNERS & PARTNER
[0021] Munich - Jena
[0022] Three coma corrections are limited. Patient-specific treatments intended to compensate for higher-order aberrations are currently not feasible – even though many publications mention such orders in general, despite their beam deflection not being capable of doing so.
[0023] The invention is therefore based on the objective of improving refractive error correction for treatment by means of lenticule extraction and, in particular, making it more patient-specific.
[0024] The invention is characterized in the independent claims. The dependent claims relate to preferred embodiments.
[0025] A treatment device for correcting the refraction of an eye is provided, wherein the refractive correction is achieved by creating at least one incision beneath a corneal surface of the eye, as occurs, for example, in treatment using lenticule extraction. The term "beneath" does not preclude the existence of an opening to the surface. Rather, it clarifies that the incision lies at least partially within the cornea and beneath its anterior surface. It encompasses at least a portion of a tissue sample (sometimes referred to as a volume in the literature on lenticule extraction-based refractive correction).
[0026] Refraction correction corrects refractive errors. These can be refractive errors that are amenable to conventional correction with glasses or contact lenses, but also more complex refractive errors, such as local corneal irregularities that need to be removed or smoothed.
[0027] The treatment device includes a laser that preferably emits pulsed laser radiation. An optical system focuses the laser radiation along an optical axis into a focus located within the eye, for example, during treatment using lenticule extraction in the cornea. A scanning device adjusts the position of the focus three-dimensionally within the eye. It comprises a scanner that adjusts the position of the focus two-dimensionally laterally within the image field and a scanner that adjusts the position of the focus axially. The term "lateral" refers to an axis of incidence of the laser radiation, or alternatively, to the visual axis of the eye. The lateral adjustment of the focus position is perpendicular to the axis and can include a shift of the axis itself. The term "axial" refers to an adjustment of the focus position along the axis.
[0028] GEYER, FEHNERS & PARTNER
[0029] Munich - Jena
[0030] 4. The axially adjustable scanner is constructed in multiple stages, consisting of several independently acting scan stages. Each scan stage can, in principle, effect an axial shift of the focus independently of the others; according to the invention, the effects of the scan stages are complementary. They differ in their scan speeds, so that a first axial scan stage and at least two fast axial scan stages, each with a higher deflection speed than the slow scan stage, are formed. Due to the speed differences, the first scan stage is also referred to as the slow scan stage and the second scan stages as the fast scan stages. The term "stage" emphasizes that the scan stages in the scanner are independent of each other with regard to their optical effect and / or can be controlled independently.The term "axial" refers to the axis along which the optics focus the laser radiation; it is often called the z-axis. In some embodiments, the two fast axial scan stages can share a common optical element that can be driven into two independently adjustable oscillations. Of course, the stages can also be formed by completely different optical elements. In all cases, the oscillations of the two fast axial scan stages can be superimposed.
[0031] The laser, optics, and scanning system are designed such that by shifting the focus along a path, the section can be generated in the eye below the corneal surface. For higher-order correction, the laterally shifting scanner moves the focus along a rotating path at a specific frequency. Simultaneously, at least two secondary (i.e., fast) axial scan stages each adjust the position of the focus axially in a harmonic oscillation at a specific frequency. This frequency is equal to the rotational frequency (ratio 1:1) or an integer multiple of the rotational frequency of the laterally shifting scanner (ratio 1:n). This is subsequently referred to simply as the oscillation of the fast or secondary scan stages. The ratios for the two secondary scanners will differ in most applications; they can also vary during section generation, i.e., assume different values for different sections of the section.
[0032] The invention extends the treatment scope to include the correction of higher-order aberrations. Known approaches generate cross-sectional surfaces that correct lower orders. These are understood here to be spherical, astigmatic, and coma corrections. The invention makes it possible to perform higher-order corrections and thus generate patient-specific lenticels in a technically surprisingly simple manner by extending the axial scanner and using a comparatively simple control system for this scanner. The (slow) first scan stage establishes lower orders. The effect of the different scan stages becomes particularly clear when the geometry of the cross-sectional surface is divided into non-rotationally symmetric components (so-called higher orders) and rotationally symmetric components (so-called lower orders). This can be done, for example, using Zernike polynomials; here patent attorneys
[0033] GEYER, FEHNERS & PARTNER
[0034] Munich - Jena
[0035] Step 5 describes the rotationally symmetric parts using polynomials with m=0. The (fast) second (and possibly subsequent) scan stages determine the non-rotationally symmetric parts of the geometry of the intersection surface; they thus provide the corrections of the higher orders (Zernike polynomials with m>0). The slow first scan stage determines the rotationally symmetric parts of the geometry of the intersection surface; it thus provides Zernike polynomials with m=0 (e.g., spherical Zernike polynomials).
[0036] The scanning device serves to change the position of the focus within the processing volume, which can be described by three spatial directions: Cartesian x, y, and z, or cylindrical r, phi, z. The lateral directions are not parallel to each other and are each perpendicular to the optical axis of the optics. The optical axis of the optics typically coincides with the z-axis. However, special configurations are also possible in which these two axes form an angle to each other that is greater than 0° but significantly less than 90° (e.g., less than 10° or 20°).
[0037] The treatment device can be designed in two different ways with regard to generating the focus and adjusting its position. Either the focus is shifted within the image field, or the image field itself is shifted. A combination of both is possible.
[0038] Focus shifting within the image field is a feature implemented, for example, in the VISUMAX devices from Carl Zeiss Meditec AG. These devices combine a z-scanner, which shifts the laser focus along the z-axis and is referred to below as the slow scan stage, with a lateral 2D scanner comprised of an x- and a y-scanner. The xy-scanners generate a spiral shape. The z-scanner deforms this spiral (typically rotationally symmetric about its center) so that it lies within the surface of a (possibly elliptically elongated) solid of revolution, or in a special case, within the surface of a three-dimensional ellipsoid, thus assuming a helical form. The pulsed laser radiation used in the VISUMAX is emitted along this path.
[0039] This scanner system makes it easy to generate shot patterns corresponding to the Zernike polynomials Z(0, n). The slow scan stage allows higher n values to be achieved for Z(0, n) by varying the z-coordinate of the shot pattern as a function of the radial distance to the spiral center. While this is generally true for all other Zernike polynomials with any value for m, the slow scan stage alone is only sufficient for Zernike polynomials with |m| = 1 and 2, by:
[0040] 1. The firing pattern is shifted laterally; thus, corrections with |m| = 1 can be achieved - with n = 3, a correction of the refractive error coma results; and patent attorneys
[0041] GEYER, FEHNERS & PARTNER
[0042] Munich - Jena
[0043] 6.2. The amplitude of the x- and y-scanners is varied relative to each other; this allows spirals with an elliptical shape to be generated. This extends access to the Zernike polynomials with |m| = 2.
[0044] Further orders with respect to m, namely of magnitude 3 and greater and for different n values, are now made possible by the at least two fast axial scan stages, if the 2D lateral scanner adjusts the position of the focus with a particularly constant rotational frequency on a rotating path, e.g. the spiral, and at the same time the fast scan stages each oscillate harmonically at a frequency that is equal to the rotational frequency or a multiple of the rotational frequency.
[0045] The rotational frequency caused by the lateral scanner can be constant, meaning it does not change with the orbital radius. In this case, the harmonic frequencies are also constant. Alternatively, the rotational frequency can depend on the trajectory radius, for example, by keeping the orbital speed constant or adjusting it in steps. Any combination is possible. For instance, the rotational frequency can be constant in one radius range of the cross-section, while in another radius range of the cross-section, the orbital speed can be kept constant or adjusted in steps.
[0046] However, it is particularly preferred that the conditions be kept constant, as this simplifies scanner control. For certain orders, it is then preferred that the amplitude of the at least two fast axial scan stages depends on the radius of the orbit, especially if the orbit is helical.
[0047] For circulating paths with varying radii, such as concentric path curves and / or spiral path curves, it can also be advantageous that a phase between the adjustment on the circulating path and the fast axial scan stage depends on a radius of the circulating path.
[0048] In the embodiments, the cross-sectional area is a simply connected surface. In the usual mathematical sense, this means that every closed path passing through the surface can be reduced to a point that also lies within the surface. A ring surface, for example, would not be such a point, but a circular disk would. For rapid generation of the cross-sectional area as a simply connected surface, it is preferred that the circumferential path be a non-circular path, in particular a spiral path.
[0049] For easy adjustment of the rotational frequency, it is preferable for the laterally adjusting scanner to have several, e.g., two galvanometer mirrors connected in series. Patent attorneys
[0050] GEYER, FEHNERS & PARTNER
[0051] Munich - Jena
[0052] 7
[0053] The multiple affects the order of the corrected aberration. It is therefore preferred that the multiple depends on the order of the aberration to be corrected, which must be higher than that caused by astigmatism and / or coma. For this purpose, refractive error data for the refractive error to be corrected can be provided / specified, containing information about these aberrations, which must be at least one order higher than astigmatism and / or coma. The multiple, and possibly also the radius-dependent amplitude and / or phase, are / are chosen depending on the order.
[0054] In certain embodiments, the image field shift itself involves moving the lens. The lateral movement is then at least partially realized by the moving, e.g., rotating, lens. This movement is, for example, reduced to uniform circular paths and therefore cannot follow elliptical paths. The change in phi is rapid, while r changes only slowly. With a slow z-scan stage, rotationally symmetric (e.g., spherical) lenticels can be generated (m = 0 for Zernike polynomials). The at least two fast z-scan stages, which follow a multiple of the lens's angular frequency, allow for higher-order corrections with magnitude m greater than zero (e.g., |m| = 1 for coma or |m| = 2 for astigmatism) and also n greater than zero, particularly asymmetric higher-order corrections, such as a Trefoil Z (|m| = 3, 3).
[0055] This makes patient-specific lenticule geometries possible.
[0056] The laser is preferably a short-pulse laser, such as a femtosecond laser (fs laser), for generating a femtosecond or picosecond laser beam. A pulsed laser emits light in time-limited portions, i.e., not continuously. It offers a high energy density. Such a femtosecond or picosecond laser can, for example, have a wavelength in the range of 200 nm to 2000 nm: Water or eye tissue exhibits low linear absorption in this range and is therefore a transparent material to the radiation of a femtosecond or picosecond laser. Non-linear or multiphoton absorption occurs within the material.
[0057] In one embodiment, the optics for focusing the coherent radiation into a focus enable an image field within the processing volume with an image field size determined by the optics. Initially, it is advantageous to be able to work with a large image field, as this allows the entire target field, and thus the entire processing volume, to be reached without moving the optics. The position of the focus is then adjusted laterally within the image field by the lateral scanner. Patent attorneys
[0058] GEYER, FEHNERS & PARTNER
[0059] Munich - Jena
[0060] 8. However, increasing the size of the optics leads to higher manufacturing costs. Therefore, a cost-effective arrangement for processing an area within a processing volume has an image field size that is smaller than the maximum extent of an xy-plane of the processing volume. The lateral scanner then adjusts the image field, in some embodiments by moving the lens. Only through this movement of the image field is the maximum extent of an xy-plane of the processing volume achieved. Hybrid forms are possible. The effect of the two fast scanners is the same in all cases (lateral movement within the image field / movement of the image field / a combination of both).
[0061] The creation of the cut surfaces is achieved by changing the position of the focus within the processing volume. At the location of the focus, an area of effect of this focused radiation is created in the transparent material, which is called the focus area: At and in the immediate vicinity of the focus point, the focused radiation alters the material. For example, when using pulsed laser radiation, focus areas are created at a distance that depends on the pulse rate. Typically, a processing surface contains a multitude of focus areas distributed across the entire surface, which are positioned at a maximum distance from each other such that the intended effect is not interrupted by the influence of the focused radiation. This results in the cut as the processing outcome along the surface being processed.
[0062] The device preferably comprises a control unit configured to control the components, in particular the laser and the scanning device, and optionally also the optics. For this purpose, it is connected to the controlled components via appropriate communication links. The control unit can be designed as a single unit or in multiple units. In a single-unit design, it contains a controller from which all parts of the arrangement are monitored and / or controlled. If it is designed in multiple units, it can contain several control and monitoring units that are interconnected.The control unit may be coded with a control program product or be coded with a control program product which is either located on a data carrier, wherein the data carrier is connected to the control unit for the purpose of coding, or the control program product is made available for download on the Internet or on another external storage location, wherein the control unit may establish a connection to the Internet or to the other external storage location directly or via intermediate stages.
[0063] The optics and the scanning device may, to a certain extent, share common components or be combined, since the axial adjustment of the focus position may involve adjusting optical elements that are also part of the optics that focus the laser radiation. Patent attorneys
[0064] GEYER, FEHNERS & PARTNER
[0065] Munich - Jena
[0066] 9
[0067] The terms "slow" and "fast" are defined in relation to each other and are used to describe the two fundamental scanning movements and scanning systems. The fast scanning movements of the second axial scanner are performed at a maximum speed that, in certain embodiments, is a multiple of the maximum speed of the slow scanning movement. Preferably, the fast axial scanning movements can be ten to one thousand times faster than the slow axial scanning movement. A fast scanning movement that is approximately one hundred times faster than the slow scanning movement is advantageous. Preferably, the travel distance of a fast scanning movement is smaller than that of the slow scanning movement. Typical sizes of the processing volume in which a slow scanning movement takes place can, for example, be between 2 mm and 25 mm in each spatial direction, preferably between 5 mm and 12 mm.This volume can typically be scanned at speeds ranging from 1 to 100 mm / s, preferably around 10 mm / s. A typical stroke for one of the fast scan movements is between 0.5 mm and 4 mm in each spatial direction. Scan movements with frequencies of several hundred Hertz or even up to the kHz range are possible.
[0068] With a small orbital radius, the lateral scanners move particularly fast and, in some embodiments, reach a rotational frequency of up to 2.4 kHz. It is therefore preferred that, due to the multiple of the lateral frequency, a few kHz are used for the harmonic oscillation, typically not more than 20 kHz.
[0069] The described method for generating control data includes preparation for correcting the refraction of an eye by corneal modification and does not require a surgical step. However, it can be supplemented with a surgical step. In this step, a laser device is used to create the incision surface, and the lenticule is removed from the cornea. The method can, in principle, be executed using a computer, specifically a processor. This computer can be configured as a planning station, as is known in the prior art.
[0070] A computing device may be provided for the execution of the generation process, which is configured to execute the corresponding process steps.
[0071] The invention further comprises a treatment method for correcting the refraction of an eye, wherein a cutting surface is generated by means of pulsed laser radiation and the above-explained adjustment of the focus is achieved by means of at least two rapid axial adjustments and patent attorneys.
[0072] GEYER, FEHNERS & PARTNER
[0073] Munich - Jena
[0074] 10 a slow axial adjustment is performed, wherein the fast axial adjustment is performed as a harmonic oscillation of the type described.
[0075] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.
[0076] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying drawings, which also disclose essential features of the invention. These exemplary embodiments serve only for illustration and are not to be interpreted as limiting. For example, a description of an exemplary embodiment with a plurality of elements or components is not to be interpreted as meaning that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components. Elements or components from different exemplary embodiments may be combined with one another unless otherwise specified. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.To avoid repetition, identical or corresponding elements in different figures are designated with the same reference symbols and are not explained multiple times. The figures show:
[0077] Fig. 1 shows a schematic representation of a device for performing lenticular-extracting refractive error correction,
[0078] Fig. 2 shows a simplified cross-sectional view through the cornea to illustrate the lenticule to be isolated and extracted.
[0079] Fig. 3 shows a projection of a section surface bounding the lenticule to illustrate the creation of the section surface.
[0080] Fig. 4 shows a representation of the scan module 8 of the device 1 ,
[0081] Figures 5 and 6 each show a block diagram for a method and
[0082] Fig. 7 shows a schematic scan pattern.
[0083] Fig. 1 schematically shows a device 1 for performing lenticular-extracting refractive error correction. The device 1 has a laser 2 that provides pulsed laser radiation, wherein, in the described embodiment, the laser 2 emits a pulsed raw beam 3 having a wavelength that penetrates the tissue of the cornea, so that patent attorneys
[0084] GEYER, FEHNERS & PARTNER
[0085] Munich - Jena
[0086] 11. Processing can be carried out there using nonlinear effects. The raw beam 3 is shaped by a pulse shaper 4 with respect to the pulse duration, whereby a pre-distortion known from the prior art can be applied, which ensures that after passing through the further optical path of the beam path in the material, i.e. in the cornea of the eye 11, the desired pulse length of, for example, < 1 ps is present. The pulse shaper 4 and the laser 2 together form a laser beam source 5, which emits a pulsed laser beam 6 of the desired pulse length.
[0087] The laser beam 6 is focused by a lens 7 along an optical axis OA into the cornea. The laser beam 6 first passes through a scan module 8, which, via a lateral scanner 8a, causes a two-dimensional beam deflection perpendicular to the direction of propagation of the laser radiation, thus adjusting the position of the focus laterally within the cornea. The scan module 8 also has an axial scanner 8b, which adjusts the position of the focus axially, i.e., along the optical axis OA. Adjustment of the focus position along the main direction of incidence can also be achieved by appropriately controlling the lens 7, provided it is designed for z-adjustment.
[0088] The scan module 8 together with the lens 7 forms a beam shaping device 9, which ensures that the pulsed laser radiation 6 is focused to adjustable locations in the cornea of an eye 11.
[0089] The laser beam source 5, the scan module 8, and the optics are suitably matched so that adjusting the position of the focus produces a cross-sectional area. In the embodiment shown in Fig. 1, the pulse frequency of the pulsed laser beam 6 is preferably between 1.2 MHz and 10 MHz, the frequency being related to those pulses that have a processing effect. The energy of these pulses of the pulsed laser beam 6 is in the range of 1 nJ to 340 nJ, preferably 80 nJ to 160 nJ, particularly preferably 10 nJ to 100 nJ, and most preferably between 20 nJ and 80 nJ. The wavelength of the laser beam 6 is preferably in a range of 1030 nm to 1060 nm or of 300 nm to 400 nm or another spectral range that can penetrate the cornea, for which the cornea has a transmittance of at least 0.8.
[0090] The device 1 optionally further comprises a contact lens 10, which serves to fix the eye 11 and also to give a desired and known shape to the anterior surface of the cornea 12 of the eye 11. The corresponding contact surface of the contact lens 10 has a radius of curvature of 50 mm or less, particularly preferably 20 mm or less. Patent Attorneys
[0091] GEYER, FEHNERS & PARTNER
[0092] Munich - Jena
[0093] Figure 12 shows (dashed lines) that, depending on the effect of the scan module 8, the focus 13 lies at different locations in the cornea 12 of the eye 11. In the configuration shown in Figure 1, the scanner 8a causes a deflection perpendicular to the main direction of incidence of the laser radiation 6.
[0094] The laser beam source 5 (implemented in the design of Fig. 1 by laser 2 and pulse shaper 4) and the beam shaping device 9 (implemented in the design of Fig. 1 by scan module 8 and lens 7) are connected via control lines (not further specified) to a control unit 14, which appropriately controls these elements. The control unit 14 generates a trajectory of the laser beam focus, which lies in the cut surface in the cornea. This cut surface is then formed within the tissue by the action of the laser radiation. With pulsed laser radiation, a series of interaction zones is typically generated in which tissue is separated. This corresponds approximately to a perforation and ultimately forms the separation in the tissue referred to as the cut surface. Fig. 2 shows a cross-sectional view through the cornea 12.
[0095] By adjusting the focus 13 of the pulsed laser beam 6, a lenticule 15 is isolated in the cornea 12. The lenticule 15 is bounded by an anterior surface 16 and a posterior surface 17. To keep the boundaries of the lenticule 15 as simple as possible, the anterior surface 16 is located at a constant distance from the anterior surface 18 of the cornea 12. This differs for the posterior surface 17, whose distance from the anterior surface 18 varies. Without this, the removal of the lenticule 15 would not change the curvature of the anterior surface 18 of the cornea 12. However, the posterior surface 17, which is ultimately curved relative to the anterior surface 18, does change the curvature of the anterior surface 18 of the cornea 12 when the lenticule 15 is removed. This removal is performed by a device shown in the figure.
[0096] 2. A lateral cut (not shown) leads, for example, along the edge of the lenticule 15 from the anterior surface 16 to the front surface 18, allowing the isolated lenticule 15 to be extracted, optionally after prior comminution of the lenticule 15 material. In the representation of Fig. 2, surfaces 16 and 17 are symmetrical about the optical axis OA. This occurs automatically for the anterior surface 16 when it maintains a constant distance from the front surface 18.
[0097] The design of surfaces 16 and 17 according to the principles described above is not strictly necessary for the following explanation and, in particular, for the design of the treatment device 1. Deviations from this are also possible; for example, both surfaces 16 and 17 may have a non-constant distance to the anterior corneal surface 18. Patent Attorneys
[0098] GEYER, FEHNERS & PARTNER
[0099] Munich - Jena
[0100] 13 The interfaces of the lenticule 15 can of course include further surfaces. For example, in a lenticule 15 that is thinner on the optical axis OA than in regions farther from the axis, an additional boundary surface can be provided, which connects the anterior surface 16 with the posterior surface 17, which then has a more strongly curved profile than the anterior surface 16 and the front surface 18.
[0101] The cut surfaces for isolating the lenticule 15 are created by shifting the focus 13 along a path that lies within the corresponding surface. This is illustrated in Fig. 3 using the posterior surface 17, which is shown elliptical in plan view for clarity. When correcting higher aberrations, the lenticule 15 is no longer necessarily rotationally symmetric about the optical axis OA. Fig. 3 shows an unfolding of the posterior surface 17 into the drawing plane. A path 19 is indicated by a dashed line in Fig. 3. The position of the focus 13 is adjusted along this path. Of course, this usually requires not only an adjustment perpendicular to the optical axis OA, but also an adjustment of the focus position along the optical axis OA. This is not apparent in Fig. 3 because this figure shows an unfolding of the posterior surface 17 into the drawing plane, which is why the path 19 is not shown in the representation of Fig.3 lies in a plane. If one considers the section through the lenticule 15 in Fig. 2, it becomes clear that with increasing distance from the optical axis OA, the z-position of the focus is also shifted away from the front surface 18.
[0102] Target points 20 are shown along path 19 in Fig. 3. Each target point represents a point onto which a laser pulse of the pulsed laser radiation 6 is emitted. By arranging the target points 20 along path 19 and by appropriately selecting the path 19, the posterior surface 17 is formed as a cross-sectional area. The distances between the target points 20 are chosen such that as few or as few material bridges as possible remain, thus generating a cross-sectional area that covers as much of the posterior surface 17 as possible.
[0103] Figure 3 clearly illustrates why it is advantageous to make the pulse frequency of the pulsed laser beam 6 variable. If the aim is to arrange the target points 20 as equidistantly as possible, the pulse frequency and the displacement speed of the steel forming device 9 must be adjusted to each other. Since a laser 2 at a high pulse frequency is generally difficult to adjust with respect to its pulse frequency, it is advantageous to first provide a raw beam 3 with the laser 2, which has a pulse frequency greater than or equal to the maximum pulse frequency desired for the laser beam 6. Individual pulses are then reduced from this raw beam using a so-called pulse picker to generate a laser beam with a reduced pulse frequency, which can ultimately be adjusted by adjusting the pulse picker. It may be simpler to implement such a laser 2 and discuss it with the patent attorneys.
[0104] GEYER, FEHNERS & PARTNER
[0105] Munich - Jena
[0106] It is more efficient to combine 14 pulse pickers than to build a laser whose pulse frequency is directly adjustable. This allows the pulse frequency to be adapted to the traversing speed, minimizing the time required to generate the cutting surface, as the pulse frequency is not limited to the maximum traversing speed of the scanners.
[0107] To correct visual defects exhibiting higher-order aberrations—this term, as throughout the description, refers to Zernike polynomials—the scan module 8 is designed in multiple stages with respect to the z-scanner 8b. It comprises at least one first scan stage (hereinafter referred to as slow) and at least two, preferably three or more, second scan stages (hereinafter referred to as fast). The design of the scan module 8 is shown schematically in Fig. 4. The configuration of the lateral scanner 8a is not of further importance, but the higher-order correction achieved by the configuration of the z-scanner 8b is. The slow scan stage is formed by a lens 20 held in a mount 22, which is moved along the z-axis by a drive 23, as indicated by a double arrow in Fig. 4. This slow scan stage is supplemented by at least two fast scan stages.Each rapid scan stage consists of a mirror or lens 24, 28 that can be set into harmonic oscillations (small double arrow) so that the lens 24, 28 oscillates between corresponding end positions. For lens 24, these are end positions 25, 26, and for lens 28, end positions 29 and 30, which are shown as dashed lines in Fig. 4. The drive for the oscillating movement of the lenses 24, 28 is preferably designed such that it can also adjust the amplitude of the oscillation, i.e., the stroke or distance between the end positions 25 and 26 or 29 and 30.
[0108] In a first example of an embodiment in which the two fast axial scan stages have a common optical element, the lens is located on stacked oscillators, each of which can be driven into an independently adjustable oscillation.
[0109] In various embodiments, lenses and mirrors can be used alternatively or in combination. Particularly with fast z-scanners with adjustable frequency, "voice coil"-like implementations are also conceivable. This can be visualized as a kind of loudspeaker with a flat, mirrored diaphragm. Similar to sound, different frequencies can be achieved in this way. This is a second example of an embodiment in which the two fast axial scan stages share a common optical element that can be driven into two independently adjustable oscillations. Another advantage of mirrors is that the actual travel distance is halved, because with a mirror, only half the distance is required for the same z-adjustment compared to what a lens would have to travel. Patent attorneys
[0110] GEYER, FEHNERS & PARTNER
[0111] Munich - Jena
[0112] 15 The z-scanner 8b can thus adjust the axial position of the focus 13 in the cornea 12 both slowly (and then comparatively over a large stroke) (adjustment of lens 20) and with two independently executed (yet coordinated) oscillations by lenses 24 and 28. An adjustment of the focus position along the main direction of incidence is optionally additionally or alternatively for the slow scan stage 20 by suitable control of the lens 7, if it is designed for z-adjustment. This option is indicated in Fig. 1 by a dashed arrow.
[0113] To correct higher-order errors, the control unit 14 now controls the lateral scanner 8a such that the focus 13 is guided along a rotating path, with the rotational frequency W=2TT fo being constant in one embodiment. The control unit 14 thus specifies a constant fundamental frequency for the rotating movement, for example in the form of the spiral 20 (Fig. 3). Understandably, in the case of a spiral such as the spiral 20, the orbital speed increases with decreasing radius as the spiral moves inwards.
[0114] Simultaneously, the control unit 14, which generates an intersection surface, for example the posterior intersection surface 17, corrects higher-order aberrations, and controls the two fast scan stages such that they each oscillate at a multiple of the fundamental frequency fo, which characterizes the rotation in the lateral direction. The two fast scanners are thus also in resonance with each other, i.e., each of these scanners oscillates at a frequency between the end positions 25, 26 and 29, 30, respectively, at an integer multiple of the fundamental frequency.
[0115] This embodiment uses a constant lateral rotational frequency. This corresponds to a constant angular velocity of the lateral deflection. Consequently, the resonant high-speed z-scanners operate at a constant frequency. Such z-scanners are technically easy to implement. Alternatively, in another embodiment, the lateral frequency depends on the radius of the orbit. Preferably, a constant orbital velocity can then be achieved, and the resonant high-speed z-scanners operate at a variable frequency, which offers advantages for the realization of the laser source with regard to uniformly affected interaction zones. Combinations are possible. The following description focuses, purely by way of example, on the variant with a constant rotational frequency.
[0116] In addition to the frequency, the amplitude of the oscillating scan stage 24, 28 also influences the trajectory of the laser focus 17. By preferentially setting the amplitude A(r) of the oscillations of the fast scan stages 24, 28 as a function of the orbital radius of the path 20, the application range is significantly expanded. This opens up a further possibility for realizing Zernike polynomials with larger n.
[0117] GEYER, FEHNERS & PARTNER
[0118] Munich - Jena
[0119] 16
[0120] The application range is also preferably extended by also adjusting phase 4> for circumferential lateral adjustment depending on the circumferential radius r.
[0121] The z-movement of the i-th scan stage can then be described by:
[0122] z_i(r(t)) = A(r(t)) * sin( 2TT foj * t + A<|)(r(t)) )
[0123] with r as the orbital radius, which in the case of a spiral is a function of time t, and foj = n * fo. fo is the orbital frequency of the lateral scanner, and n is greater than or equal to 1 and a natural number.
[0124] Fig. 5 schematically shows the steps for generating control data for the treatment device 1. These steps can be performed in the control unit 14 or, alternatively, in a separate planning unit. Such planning units are known in the prior art.
[0125] In step S1, a need for refractive error correction is determined or corresponding refractive error data is provided, which describes the refractive error to be corrected for the patient.
[0126] In step S2, a corneal tissue sample is determined from the refractive error data, which is then removed to correct the refractive error. This step specifies which refractive errors contained in the data need to be corrected. This is done based on Zernike polynomials. Therefore, step S2 defines the order up to which the Zernike polynomials should be corrected.
[0127] In step S3, control data is generated for the aforementioned treatment device, which, during operation, creates the cut surface 17 by deflecting the focus along a spiral path 20. The control data is defined such that it specifies to the laterally adjusting scanner that the focus is guided along a rotating path with a constant rotational frequency fo. For the at least one fast axial scan stage, the control data specifies that the position of the focus is adjusted axially in a harmonic oscillation with a constant frequency that is an integer multiple of the rotational frequency fo. Furthermore, a radial dependence of the amplitude of the oscillation on the radius of the rotating path in the spiral 20, as well as a phase between the rotating path 20 and the oscillation of the at least one fast scan stage, for example, scan stage 24, are defined.
[0128] GEYER, FEHNERS & PARTNER
[0129] Munich - Jena
[0130] 17 In step S4, the control data is saved and assigned to a specific patient, so that when this patient is treated, the treatment device 1 creates the desired interface 19.
[0131] Figure 6 shows a block diagram of the steps of a treatment procedure that can be performed. In step S5, pulsed laser radiation is supplied. In step S6, this laser radiation is focused into the eye along the optical axis. In step S7, the position of the focus in the field of view is adjusted laterally along a rotating path at a constant rotational frequency, and simultaneously, the position of the focus is adjusted axially by at least two scan stages with different scan speeds. The rapid axial adjustment performed is synchronized with the adjustment of the focus position in the lateral direction such that it is a harmonic oscillation with a constant frequency that is an integer multiple of the constant rotational frequency.
[0132] The following conditions are relevant for the fast axial scan stages:
[0133] In telescopic optics, the telescope ratio of the device influences the required amplitude of the fast axial scan stages. For example, if the telescope ratio is 10, each scan stage must move 10 length units itself to shift the focus by one length unit if it uses lenses, and 5 length units if it uses reflections.
[0134] The maximum required focus shift depends on the lenticule geometry. It increases with the degree of astigmatism to be corrected and with the (lateral) size of the optical zone over which the correction is to be achieved. With lenticule geometries featuring large deflections, a shift of up to 0.2 mm in the eye is possible in some designs. With a telescope ratio of 10, this results in a travel distance of up to 2 mm for lens-based scan stages.
[0135] In a spiral motion, the smaller the radius of the lateral spiral movement, the higher the rotational frequency is if a constant orbital speed is to be maintained. This is advantageous with regard to uniform spacing of the points where laser radiation pulses are introduced. The frequencies of the harmonically oscillating fast axial scan stages increase accordingly. However, their maximum frequency is limited—in many embodiments, it depends on the amplitude. For this reason, in some embodiments, the laser pulse frequency is reduced at or before the maximum frequency of the fast axial scan stages is exceeded. Preferably, a cut-off frequency is defined for the oscillating fast axial scan stages, and the laser pulse frequency is selected so that the cut-off frequency is not exceeded. [Patent attorneys...]
[0136] GEYER, FEHNERS & PARTNER
[0137] Munich - Jena
[0138] The rotational frequency can also be adjusted by considering multiples (1 to n). For large distances to the optical axis, the travel distance of the fast axial scan stages increases. If a technical limit is reached (travel distance not achievable at a given frequency), the laser pulse frequency is reduced for the subsequent path.
[0139] Figure 7 shows a scan pattern that results when one of the two fast scan stages is driven at the lateral rotational frequency and the other at twice the rotational frequency. The z-coordinate is plotted on the vertical axis; the x- and y-axes are plotted perpendicular to it.
[0140] The processing procedure follows on from the procedure for generating the tax data and can also include it. The following configurations are particularly suitable for this purpose:
[0141] A. Treatment procedure for correcting the refraction of an eye, in which an incision is made below a corneal surface of the eye and which comprises the following steps:
[0142] Providing laser radiation,
[0143] Focusing the laser radiation into a focus located inside the eye, adjusting the position of the focus in a lateral direction on a rotating path with a rotational frequency and
[0144] Adjusting the position of the focus axially by several scan stages, combining at least two fast axial adjustments and one slow axial adjustment, wherein the fast axial adjustments are performed as harmonic oscillations with a constant frequency, each equal to the rotational frequency or an integer multiple of the rotational frequency.
[0145] B. Treatment method according to A, characterized in that the amplitude of at least one of the rapid axial adjustments depends on the radius of the circumferential path.
[0146] C. Treatment method according to A or B, characterized in that the integer multiples of the at least two rapid axial adjustments differ from each other.
[0147] D. Treatment method according to one of A, B or C, characterized in that a phase between the rapid axial adjustments and the circumferential path depends on the radius of the circumferential path (209). Patent Attorneys
[0148] GEYER, FEHNERS & PARTNER
[0149] Munich - Jena
[0150] 19 E. Treatment method according to one of A, B, C or D, characterized in that the integer multiple is three or more.
[0151] F. Treatment method according to one of A, B, C, D or E, characterized in that the circumferential path is a non-circular path, in particular a spiral path.
[0152] G. Method according to one of A, B, C, D, E or F, characterized in that refractive error data are provided for a refractive error to be corrected, which contain information on aberrations that contain at least one order higher than astigmatism and / or coma, and that the multiple and - insofar as the method according to claim 10 is carried out, also the radius-dependent amplitude and / or the method according to claim 13 is carried out, also the phase - is selected depending on the order.
Claims
patent attorneys GEYER, FEHNERS & PARTNER Munich - Jena Carl Zeiss Meditec AG Attorney's file: PAT 9030 / 264- PCT Patent claims 1. Treatment device for correcting the refraction of an eye (11) by generating at least one cut surface (17) below a corneal surface (18) of the eye (11), wherein the treatment device (1) comprises: a laser beam source (5) that emits laser radiation (6), an optic (7) which focuses the laser radiation (6) into a focus (13) located inside the eye (11), and a scanning device (8) which adjusts the position of the focus (13) three-dimensionally in the eye (11) and for this purpose comprises a scanner (8a) which adjusts the position of the focus (13) laterally two-dimensionally and a scanner (8b) which adjusts the position of the focus (13) axially, wherein the axially adjusting scanner (8b) is designed in multiple stages with several independent axial scan stages (22, 24, 28), wherein the laser beam source (5), the optics (7) and the scanning device (8) are designed such that by shifting the focus (13) along a path (20) the cross-sectional area (17) in the eye (11) below the corneal surface (18) can be generated, characterized by the fact that the laterally adjusting scanner (8a) guides the focus (13) on a rotating path (20) with a rotational frequency and the axially adjusting scanner (8b) comprises a first scan stage (22) and at least two second scan stages (24, 28), each of which is faster in terms of scan speed than the first scan stage (22), wherein these fast scan stages (24, 28) each adjust the position of the focus (13) axially in a harmonic oscillation with a frequency equal to the rotational frequency or an integer multiple of the rotational frequency.
2. Treatment device according to claim 1, characterized in that the rotational frequency is constant for at least one or more radii and harmonic oscillations each have a constant frequency.
3. Treatment device according to one of the above claims, characterized in that the rotational frequency depends on a radius of the rotating track (20) and the frequency of the harmonic oscillation is dependent on the track radius. Patent attorneys GEYER, FEHNERS & PARTNER Munich - Jena 21 4. Treatment device according to one of the above claims, characterized in that an amplitude of at least one of the second scan stages (24, 28) depends on a radius of the circumferential path (20).
5. Treatment device according to one of the above claims, characterized in that the integer multiples of the second scan stages (24, 28) differ from each other and / or the second scan stages (24, 28) operate at the same frequency but with different amplitudes and / or are out of phase with each other.
6. Treatment device according to one of the above claims, characterized in that a phase between the adjustment on the circumferential track (20) and the second scan stage (24, 28) depends on a radius of the circumferential track (20).
7. Treatment device according to one of the above claims, characterized in that the integer multiple of at least one of the second scan stages (24, 28) is three or more.
8. Treatment device according to one of the above claims, characterized in that the circumferential track is a non-circular track, in particular a spiral track (20).
9. Treatment device according to one of the above claims, characterized in that the laterally adjusting scanner (8a) has several galvanometer scanners connected in series for each adjustment direction.
10. Method for generating control data configured for a treatment device (1), wherein the treatment device (1) for correcting the refraction of an eye (11) by generating at least one cross-sectional area (17) below a corneal surface (18) of the eye (11) focuses laser radiation into a focus (13) located in the eye (11) and comprises a scanning device (8) which includes a scanner (8a) for laterally adjusting the focus (13) and a scanner (8b) for axially adjusting the position of the focus (13), wherein the axially adjusting scanner (8b) is configured as a multi-stage device with several independent axial scan stages (22, 24, 28). characterized by the fact that the control data are generated in such a way that they specify to the laterally adjusting scanner (8a) to guide the focus (13) on a rotating path (20) with a rotational frequency, and for the axial scanner (8b) the control data for a first scan stage (22) and at least two second scan stages (24, 28), each with regard to scan speed faster patent attorneys GEYER, FEHNERS & PARTNER Munich - Jena 22 are specified as the first scan stage (22), wherein the control data for the second axial scan stages (24, 28) specify an adjustment of the axial position of the focus (13) in each case in a harmonic oscillation with a frequency that is an integer multiple of the rotational frequency of the laterally deflecting scanner (8a).
11. Method according to claim 10, characterized in that the rotational frequency is constant for at least one or more radii and harmonic oscillations each have a constant frequency.
12. Method according to one of claims 10 or 11, characterized in that the rotational frequency depends on a radius of the orbit (20) and the frequency of the harmonic oscillation is dependent on the orbit radius.
13. Method according to one of claims 10 to 12, characterized in that the control data are generated in such a way that they specify an amplitude for at least one of the second axial scan stages (24, 28) which depends on the radius of the circumferential path (20).
14. Method according to one of claims 10 to 13, characterized in that the integer multiples of the at least two second scan stages (24, 28) differ from each other and / or the second scan stages (24, 28) operate at the same frequency but with different amplitudes and / or are out of phase with each other.
15. Method according to one of claims 10 to 14, characterized in that a phase between the fast axial scan stage (24, 28) and the circumferential track (20) depends on the radius of the circumferential track (20).
16. Method according to one of claims 10 to 15, characterized in that the integer multiple is three or more.
17. Method according to one of claims 10 to 16, characterized in that the circumferential path is a non-circular path, in particular a spiral path (20).
18. Method according to one of claims 10 to 17, characterized in that refractive error data for a refractive error to be corrected are provided, which contain information on aberrations that are at least one order higher than astigmatism and / or coma, and that the multiple is chosen depending on the order.