Treatment device for the surgical correction of refractive errors in an eye and method for generating control data for it

Abstract

Treatment device for surgical hyperopia correction of the eye (3), wherein the treatment device (1) comprises a laser device (L) controlled by a control unit (12), which separates corneal tissue by emitting laser radiation (2), wherein the control unit (12) is configured to control the laser device (L) to emit the laser radiation (2) into the cornea (5) in such a way that a lenticular volume (18) is isolated in the cornea (5), the removal of which from the cornea (18) effects the desired hyperopia correction, wherein the control unit (12), when controlling the laser device (L), specifies the lenticular volume (18) such that it has a posterior surface (20) and an anterior surface (19) which are connected to each other in a transition zone (24) which has a width of at least 0.1 mm, characterized in that the edge surface (24) has a first,The section (25) opens largely perpendicularly into the anterior surface and has a second section (26) that is more strongly inclined towards the visual axis (OA).

Description

[0001] The invention relates to a treatment device for the surgical correction of refractive errors in the eye, wherein the treatment device has a laser device controlled by a control unit, which separates corneal tissue by emitting laser radiation, wherein the control unit is configured to control the laser device to emit the laser radiation into the cornea in such a way that a lenticule-shaped volume is isolated in the cornea, the removal of which from the cornea effects the desired correction.

[0002] The invention further relates to a method for generating control data for a laser device of a treatment device for the surgical correction of refractive errors in the eye, which separates corneal tissue by irradiating with laser radiation, wherein the control data during operation control the laser device to emit the laser radiation into the cornea in such a way that a lenticule-shaped volume is isolated in the cornea, the removal of which from the cornea effects the desired correction.

[0003] The classic way to correct refractive errors in the human eye is with glasses. However, refractive surgery is increasingly used, which corrects refractive errors by altering the cornea. The aim of these surgical methods is to selectively modify the cornea to influence its refraction of light. Various surgical techniques are available for this purpose. The most widespread currently is laser-assisted in situ keratomileusis, also known as LASIK. In this procedure, a corneal flap is first detached from the corneal surface on one side and folded back. This flap can be detached using a mechanical microkeratome or a laser keratome, such as those distributed by Intralase Corp., Irvine, USA.After the corneal flap is detached and folded back, the LASIK procedure involves the application of an excimer laser, which ablates the exposed corneal tissue. Once the volume of tissue in the cornea has been vaporized in this way, the corneal flap is folded back into its original position.

[0004] The use of a laser keratome to expose the lamella is advantageous because it reduces the risk of infection and improves the cut quality. In particular, the lamella can be produced with a much more consistent thickness. The cut is also potentially smoother, which reduces subsequent optical disturbances caused by this interface remaining even after the operation.

[0005] When creating a corneal cut using laser radiation, pulsed laser radiation is typically introduced into the tissue, with a pulse duration usually less than 1 ps. This limits the power density required to trigger an optical breakthrough for each pulse to a narrow spatial area. US 5,984,916 A clearly demonstrates that the spatial area of ​​the optical breakthrough (in this case, the generated interaction) is strongly dependent on the pulse duration. A high degree of laser beam focus, combined with the aforementioned short pulses, thus allows for pinpoint accuracy in creating the optical breakthrough within the cornea. To create the cut, a series of optical breakthroughs are generated at predetermined locations, forming the cut surface. In the case of the laser keratome mentioned, the cut surface forms the flap that is lifted before laser ablation.

[0006] German patent DE 100 22 995 A1 discloses a method for generating a control program for a device used in corneal surgery of the eye. German patent DE 10 2005 049 281 A1 discloses a device and a method for material processing using laser radiation. Refractive eye surgery is described in the Wikipedia article "Refractive Surgery" at https: / / de.wikipedia.org / wiki / Refraktive_Chirurgie.

[0007] In the conventional LASIK method, exposed corneal tissue is vaporized, a process also known as "resurfacing" the cornea using laser radiation. The volume of tissue removed, necessary for refractive error correction, is adjusted for each area of ​​the exposed cornea by the number and energy of the laser pulses. The amount of material removed varies depending on the number and energy of the laser pulses.

[0008] Recently, the aforementioned surgical procedure was described and investigated in initial trials. Using laser radiation, a volume is isolated within the cornea, and then the tissue forming this volume is removed. Since pulsed laser radiation is typically used here as well, the procedure is called femtosecond lenticule extraction, or FLEx for short. The resulting volume is referred to as a lenticule.

[0009] Experiences gained from using ablation lasers to reshape the cornea cannot be applied to the FLEx procedure in refractive eye surgery. In FLEx, the volume to be removed from the cornea is not ablated from exposed corneal tissue, but rather isolated within the cornea by creating a three-dimensional incision, thus making it removable. This is because the approaches—vaporizing the material to be removed on the one hand and removing an isolated volume on the other—are too different. This is especially true for the choice of the incision that defines the volume to be removed, as such an incision does not exist in conventional LASIK surgery. Furthermore, the postoperative healing processes differ because the surfaces have different structures.

[0010] Manual removal requires a certain mechanical stability of the tissue sample, which, in addition to the intended refractive effect, represents a further constraint. Therefore, the tissue sample should be as thick as the remaining corneal thickness after its removal allows.

[0011] This desire is countered by the need for a shape that allows the refractive effects of the healing processes to be minimized or at least made predictable. If the lenticules are shaped in such a way that healing processes significantly alter the correction directly induced by the refractive therapy, for example, through corneal thickening, this would be perceived as unfavorable by patients. Such negative effects of healing processes are referred to as regression. It is necessary to allow healing processes to proceed as smoothly as possible, i.e., without refractive changes; in other words, the refractive effect should occur as quickly as possible to the desired extent and then remain constant indefinitely. However, this is not always possible, which is why the regression associated with healing processes often has to be factored into the planning of refractive therapy.Due to the physiological properties of the human eye, it is to be expected that hyperopic corrections using the FLEx method are generally more susceptible to such healing processes. Therefore, there is a desire to minimize and make these refractive changes during the healing process as predictable as possible, if they cannot be avoided.

[0012] Here, the current state of the art in hyperopia correction is of no help, since the cut and lenticule shapes known so far relate to myopia correction.

[0013] Overall, refractive correction using FLEX involves different and sometimes new boundary conditions in many areas compared to the conventional LASIK method.

[0014] It is therefore an object of the present invention to design a treatment device or a method of the type mentioned above in such a way that the cut surfaces for the lenticule are favorable for both safe removal and the healing process.

[0015] The invention is defined in claims 1 and 2.

[0016] The device includes, among other things, a treatment device for the surgical correction of hyperopia in the eye, wherein the treatment device comprises a laser device controlled by a control unit, which separates corneal tissue by emitting laser radiation, wherein the control unit is configured to control the laser device for the emission of laser radiation into the cornea in such a way that a lenticule-shaped volume is isolated in the cornea, the removal of which from the cornea effects the desired hyperopia correction, wherein, when controlling the laser device, the control unit defines the lenticule-shaped volume such that it has a posterior surface and an anterior surface, the edges of which are connected by a boundary surface, wherein the intersection curve of the boundary surface and a plane containing the visual axis has a width transverse to the visual axis that is greater than that which would be a straight line in the same projection plane.which stands perpendicular to the edge of the posterior or anterior surface on the respective surface and connects the anterior surface with the posterior surface or with its imaginary continuation.

[0017] It is further provided, among other things, for a method for generating control data for a laser device of a treatment device for the surgical correction of hyperopia in the eye, which separates corneal tissue by emitting laser radiation, wherein the control data during operation control the laser device to deliver the laser radiation into the cornea in such a way that a lenticular volume is isolated in the cornea, the removal of which from the cornea effects the desired hyperopia correction, wherein the control data define the lenticular volume such that it has a posterior surface and an anterior surface, the edges of which are connected by a boundary surface, wherein the intersection curve of the boundary surface and a plane in which the visual axis is contained has a width transverse to the visual axis that is greater than that which would be a straight line in the same projection plane.which stands perpendicular to the edge of the posterior or anterior surface on the respective surface and connects the anterior surface with the posterior surface or with its imaginary continuation.

[0018] The invention is based on the understanding that postoperative (regression) problems in the FLEX procedure arise from the fact that the detached and repositioned corneal flap does not fit unfavorably at the edge of the harvested volume or cannot lie flat. To avoid such regression problems, the invention creates a wide marginal zone, thus providing a transition zone for the corneal flap as it transitions to the posterior cut surface created to isolate the lenticule-shaped volume. This transition zone results in virtually no regression. If this transition zone is preferably also located outside the optically effective area, i.e., outside the dark-adapted pupil of the eye, the risk of further undesirable side effects is reduced even further. Preferably, the transition zone has a width between 0.1 and 1 mm.

[0019] It was further shown that regressions are particularly well reduced when the marginal surface merges as perpendicularly as possible into the anterior surface. Such a shape is initially surprising, since with such a perpendicular opening, the overlying corneal lamella can also have a step leading perpendicularly away from the anterior corneal surface. However, this perpendicular opening proves unproblematic with regard to regression if the marginal surface below this perpendicular opening has a second section that is more inclined towards the visual axis. Due to this structure, the lenticular volume has a marginal thickness that is preferably between 5 and 10 µm. It was found that such a marginal thickness is unproblematic with regard to regression, while at the same time ensuring better removal of the tissue sample, since the marginal thickness reliably prevents particles from tearing off at the edge when the tissue sample is removed.Such particles influence the placement of the corneal flap after tissue removal much more strongly than the comparatively thin edge of the tissue sample and thus the short, perpendicularly terminating section of the edge surface. This embodiment of the invention therefore takes a marginal structure that appears a priori to be negative and consequently achieves less regression, i.e., better ingrowth behavior, than would actually be expected with the narrowest possible margin.

[0020] The second section of the edge surface, which is more inclined towards the visual axis, can be designed in many ways. For example, a straight line at an angle to the first section is possible, lying at an angle of 80° to 100° to the direction of the visual axis. The second section of the edge surface can then be understood as a chamfer. However, curved lines are also possible, for example, a concave line relative to the point where the visual axis intersects the surface, i.e., a curvature of the second section towards the visual axis. In this case, the second section is then, for example, rounded off.

[0021] Within the scope of the invention, a wide variety of geometries are suitable for the boundary, all of which positively influence the regression behavior by providing the described wide transition zone.

[0022] In a further development of the invention, the rim structure is combined with a dimensioning rule for the corneal volume, which defines the radius of curvature that the cornea has after the volume has been removed. This further development of the invention thus allows not only a regression-optimized rim structure, but also an analytical calculation of the posterior and anterior surfaces.

[0023] The description of the corneal curvature after correction is based on refractive error data, which determines the refractive power B. BR specify a pair of glasses suitable for correcting refractive errors, which are positioned at a distance of d HSThe lobe must lie in front of the corneal apex to achieve the desired refractive error correction. Determining these parameters is standard practice in ophthalmology and allows the use of existing measuring instruments. Naturally, the measurement data used can also reflect astigmatism errors or errors of higher aberration orders, so that the equation describing the radius of curvature of the cornea, reduced by the volume, then has corresponding angular parameters (referenced to cylindrical coordinates), as shown in equation (1) of the figure description below.

[0024] Therefore, a further development of the device or method according to the invention is preferred in which the anterior surface is at a constant distance d. F The anterior surface of the cornea lies against the posterior surface, and the posterior surface is curved with a radius of curvature R. L = R CV * - d Fhas, where Rcv* satisfies the following equation: Rcv* = 1 / ((1 / Rcv) + B BR / ((n c -1) · (1 - d HS · B BR ))) + F, and R CV the radius of curvature of the cornea before removal of the volume, n c the refractive power of the corneal material, F is a correction factor, B BR the refractive power of glasses suitable for correcting refractive errors, as well as the HS the distance at which the glasses with refractive power B BR It would have to be located in front of the corneal vertex in order to achieve the desired refractive error correction using glasses.

[0025] The correction factor F represents a measure of the optical effect of the reduction in corneal thickness along the visual axis, which results from the removal of the volume. In a simplified calculation, the factor F can be set to 0. In a more precise calculation, F can be calculated as follows: F = (1 - 1 / n c) · (dc* - dc), where dc and dc* denote the thickness of the cornea before and after removal of the volume, respectively, and the radius R CV * can be calculated iteratively by taking the difference (R) at each iteration step CV * - R CV ) is inferred from a change in thickness (dc* - dc) and the corresponding result obtained for the change in thickness is used in the calculation of R CV * is applied in the next iteration step. The iterative calculation for F can be aborted, for example, if the difference between two iteration steps for F is only smaller than a certain limit.

[0026] The design of the posterior surface, as proposed in the advanced training, with a curvature that corresponds to that of the anterior corneal surface after volume removal, allows for a particularly simple definition of the surfaces bounding the volume. This is because the anterior surface now lies at a constant distance from the anterior corneal surface, and the optical correction is achieved by shaping the posterior surface. Significant computational effort then arises only for defining the posterior sub-surface, not the anterior sub-surface. Furthermore, it is also evident that such an approach simultaneously enables a simple analytical description of the posterior sub-surface.

[0027] The inventive method for preparing the control data can be carried out without human intervention. In particular, it can be executed by a computer that determines the control data from corresponding specifications, for example, from measurement data of the eye. Most importantly, the involvement of a physician is in no way required for determining the control data, since no therapeutic intervention is involved in determining the control data. This only takes place when the previously determined control data is applied.

[0028] Insofar as process steps are described in this description, a control unit is provided in the device according to the invention, which takes care of the execution of the process steps during operation of the device.

[0029] The invention is explained in more detail below with reference to the drawings by way of example. The drawings show: Fig. 1 a schematic representation of a treatment device or appliance for correcting refractive errors, Fig. 1a a schematic representation of the structure of the treatment device of the Fig. 1, Fig. 2. A schematic diagram of the introduction of pulsed laser radiation into the eye during refractive error correction with the treatment device of the Fig. 1, Fig. 3 another schematic representation of the treatment device of the Fig. 1, Fig. 4 in partial figures (a), (b) and (c) schematic sectional views to illustrate the need for correction in the human eye in cases of visual impairment, Fig. 5 a schematic cross-sectional view through the cornea showing a volume to be removed to correct refractive error, Fig. 6. A cut through the cornea after removal of the volume of the Fig. 5, Fig. 7 a sectional view similar to the Fig. 5, Fig. 8 a schematic cross-sectional view through the cornea to illustrate volume removal, Fig. 9a a top view of the cornea to illustrate the cross-sectional surfaces produced during refractive error correction, Fig. 9b a sectional view of the top view of the Fig. 9a, which illustrates the profile of a volume removed for hyperopia correction, Fig. 10a a representation similar to the Fig. 9a, but here for myopia correction, Fig. 10b a representation similar to the Fig. 9a, however, again for myopia correction, Fig. 11a a representation similar to the Fig. 9a, however with a different cutting technique regarding the removal of the volume, Fig. 11b a sectional view similar to the Fig. 9b, however, for the top view of the Fig. 11a, Fig. 12a a sectional view similar to the Fig. 9a, however with a different edge cut to limit the volume removed for refractive error correction, Fig. 12b an enlarged partial view of the edge section of the Fig. 9a and Fig. 12c and Fig. 12d an enlarged edge section representation similar to the Fig. 12b, however, for other geometries of the boundary surface.

[0030] Fig. Figure 1 shows a treatment device 1 for an ophthalmic surgical procedure similar to that described in EP 1 159 986 A1 and US 5 549 632 A. The treatment device 1 uses a treatment laser beam 2 to correct refractive errors in the eye 3 of a patient 4. The refractive error can include hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism with hyperopia in one direction and myopia in a direction perpendicular to it), aspheric aberrations, and higher-order aberrations. In the described embodiment, the treatment laser beam 2 is applied as a pulsed laser beam focused into the eye 3. The pulse duration is, for example, in the femtosecond range, and the laser beam 2 acts on the cornea by means of non-linear optical effects. The laser beam has, for example, short laser pulses of 50 to 800 fs (preferably 100 - 400 fs) with a pulse repetition frequency between 10 and 500 kHz.In the described embodiment, the components of device 1 are controlled by an integrated control unit, which can of course also be designed independently.

[0031] Before the treatment device is used, the refractive error of eye 3 is measured with one or more measuring devices.

[0032] Fig. Figure 1a schematically shows the treatment device 1. In this variant, it has at least two components or modules. A laser unit L emits the laser beam 2 onto the eye 3. The operation of the laser unit L is fully automatic; that is, upon receiving a corresponding start signal, the laser unit L begins deflecting the laser beam 2, thereby creating cut surfaces that are constructed in a manner to be described later and isolate a volume within the cornea. The control data required for operation is received by the laser unit L beforehand from a planning unit P as a control data set via control lines not specified. This transmission takes place before the laser unit L begins operation. Of course, communication can also be wireless.As an alternative to direct communication, it is also possible to arrange the planning unit P spatially separated from the laser unit L and to provide a corresponding data transmission channel.

[0033] Preferably, the control data record is transmitted to the treatment device 1, and further preferably, operation of the laser device L is blocked until a valid control data record is present at the laser device L. A valid control data record can be a control data record that is, in principle, suitable for use with the laser device L of the treatment device 1. In addition, validity can also be contingent upon passing further checks, for example, whether additional information about the treatment device 1, e.g., a device serial number, or the patient, e.g., a patient identification number, stored in the control data record matches other information that was read from the treatment device or entered separately once the patient is in the correct position for operation of the laser device L.

[0034] The planning unit P generates the control data set, which is provided to the laser unit L for executing the operation, from measurement data and refractive error data determined for the eye to be treated. This data is supplied to the planning unit P via an interface S and, in the illustrated embodiment, originates from a measuring device M that previously measured the eye of patient 4. Of course, the measuring device M can transmit the corresponding measurement and refractive error data to the planning unit P in any desired manner.

[0035] Data transfer can be carried out using memory chips (e.g., via USB or memory stick), magnetic storage devices (e.g., floppy disks), wirelessly (e.g., WLAN, UMTS, Bluetooth), or via wired connections (e.g., USB, FireWire, RS232, CAN bus, Ethernet, etc.). The same applies, of course, to data transfer between planning device P and laser device L.

[0036] A direct wireless or wired connection between the measuring device M and the treatment device 1 for data transmission, which can be used in one variant, has the advantage of virtually eliminating the use of incorrect measurement and refractive error data. This is particularly true when the patient is transferred from the measuring device M(s) to the laser device L using a positioning device (not shown in the figure) that interacts with the measuring device M and the laser device L in such a way that the respective devices detect whether the patient 4 is in the correct position for measurement or the application of the laser radiation 2. The transfer of the measurement and refractive error data to the treatment device 1 can also occur simultaneously with the transfer of the patient 4 from the measuring device M to the laser device L.

[0037] It is preferably ensured by suitable means that the planning device P always generates the control data record belonging to patient 4, and the erroneous use of an incorrect control data record for patient 4 is virtually impossible.

[0038] The mode of operation of laser beam 2 is described in Fig. Figure 2 is schematically indicated. The treatment laser beam 2 is focused into the cornea 5 of the eye 6 by means of an unspecified optic. This creates a focus in the cornea 5 that covers a spot 6, and in which the laser radiation energy density is so high that, in combination with the pulse length, a non-linear effect occurs in the eye. For example, each pulse of the pulsed laser radiation 2 can create an optical breakthrough in the cornea 5 at the respective spot 6, which in turn produces a Fig. A plasma bubble, schematically indicated in 2, is initiated. This laser pulse separates tissue in the cornea. When a plasma bubble forms, the tissue layer separation covers a larger area than the spot 6, which is covered by the focus of the laser radiation 2, even though the conditions for generating the breakthrough are only met at the focus. For each laser pulse to generate an optical breakthrough, the energy density, i.e., the fluence of the laser radiation, must be above a certain pulse-length-dependent threshold. This relationship is known to those skilled in the art, for example, from DE 695 00 997 T2.

[0039] Alternatively, a tissue-separating effect can also be generated by pulsed laser radiation by emitting multiple laser pulses in one area, whereby spots 6 overlap for several laser pulses. In this case, several laser pulses work together to achieve a tissue-separating effect.

[0040] The specific type of tissue separation employed by the treatment device 1 is not relevant for the following description; the essential point is that pulsed treatment laser radiation 2 is used. For example, a treatment device 1 as described in WO 2004 / 032 810 A2 can be used. It is also essential that a multitude of laser pulse foci in the tissue form a cut surface, the shape of which depends on the pattern in which the laser pulse foci are arranged in the tissue. This pattern specifies target points for the focus position at which one or more laser pulses are delivered and defines the shape and position of the cut surface. The pattern of target points is important for the procedures and devices described below and will be described in more detail later.

[0041] To correct a refractive error, pulsed laser radiation is used to remove material from a specific area within the cornea 5. This is achieved by separating tissue layers that isolate the material and allow for its removal. The material removal causes a change in the cornea's volume, which in turn alters the cornea's optical imaging power. This change is precisely calibrated to correct the previously determined refractive error as effectively as possible. To isolate the volume to be removed, the laser beam 2 is focused on target points within the cornea 5, typically in an area located below the epithelium and Bowman's membrane, and above Deceme's membrane and the endothelium. The treatment device 1 incorporates a mechanism for adjusting the position of the laser beam 2's focus within the cornea 5. This is shown schematically in Fig. 3 shown.

[0042] In Fig. The elements of the treatment device 1 are shown only to the extent necessary for understanding the focus adjustment. As already mentioned, the laser radiation 2 is focused at a focus 7 in the cornea 5, and the position of the focus 7 in the cornea is adjusted so that energy from laser radiation pulses is focused at various points to create the incision surface and introduced into the tissue of the cornea 5. The laser radiation 2 is provided by a laser 8 as pulsed radiation. An xy-scanner 9, which in one variant is implemented by two essentially orthogonally deflecting galvanometer mirrors, deflects the laser beam coming from the laser 8 two-dimensionally, so that a deflected laser beam 10 is present after the xy-scanner 9. The xy-scanner 9 thus causes an adjustment of the position of the focus 7 essentially perpendicular to the main direction of incidence of the laser radiation 2 into the cornea 5.To adjust the depth of field, a z-scanner 11 is provided in addition to the xy-scanner 9; this z-scanner is designed, for example, as an adjustable telescope. The z-scanner 11 ensures that the z-position of the focus 7, i.e., its position on the optical axis of incidence, is changed. The z-scanner 11 can be positioned upstream or downstream of the xy-scanner 9. The coordinates subsequently designated x, y, and z therefore refer to the deflection of the focus 7.

[0043] For the operating principle of the treatment device 1, the assignment of the individual coordinates to the spatial directions is not essential; however, for the sake of simplicity, z will always denote the coordinate along the optical axis of incidence of the laser radiation 2, and x and y will denote two mutually orthogonal coordinates in a plane perpendicular to the direction of incidence of the laser beam. It is of course known to those skilled in the art that a three-dimensional description of the position of the focus 7 in the cornea 5 can also be achieved using other coordinate systems; in particular, it need not be a rectangular coordinate system. Therefore, it is not mandatory that the xy-scanner 9 deflects about axes perpendicular to each other; rather, any scanner capable of adjusting the focus 7 in a plane in which the axis of incidence of the optical radiation does not lie can be used. Thus, oblique coordinate systems are also possible.

[0044] Furthermore, non-linear coordinate systems can also be used to describe or control the position of focus 7, as will be explained below. Examples of such coordinate systems are spherical coordinates and cylindrical coordinates.

[0045] To control the position of focus 7, the xy-scanner 9 and the z-scanner 11, which together constitute a concrete example of a three-dimensional focus adjustment device, are controlled by a control unit 12 via unspecified lines. The same applies to the laser 8. The control unit 3 ensures suitably synchronous operation of the laser 8 and the three-dimensional focus adjustment device, exemplified by the xy-scanner 9 and the z-scanner 11, so that the position of focus 7 in the cornea 5 is adjusted in such a way that ultimately a material of a certain volume is isolated, the subsequent removal of which achieves the desired refractive error correction.

[0046] The control unit 12 operates according to predefined control data, which specifies the target points for focus adjustment. The control data is generally summarized in a control data set. In one embodiment, this data set specifies the coordinates of the target points as a pattern, whereby the sequence of the target points in the control data set determines the sequence of focus positions and thus ultimately a trajectory (here also referred to simply as a path). In one embodiment, the control data set contains the target points as concrete setpoints for the focus position adjustment mechanism, e.g., for the xy-scanner 9 and the z-scanner 11. To prepare for the ophthalmic surgical procedure, i.e., before the actual surgical procedure can be performed, the target points and preferably also their sequence in the pattern are determined.Pre-planning of the surgical procedure is necessary to determine the control data for the treatment device 1, the application of which then achieves an optimal refractive error correction for the patient 4.

[0047] First, the volume to be isolated from corneal tissue 5 and later removed must be determined. As already discussed in the following... Fig. As described in 1a, this requires a determination of the need for correction. Fig. Figure 4 shows, in sub-figures a), b), and c), the optical conditions at the eye 3 of patient 4. Without refractive error correction, the situation shown in sub-figure a) exists. The cornea 5, together with the lens 13, focuses an object at infinity onto a focus F located on the z-axis behind the retina 14. The imaging effect arises, firstly, from the lens 13, which is relaxed when the eye is not accommodated, and secondly, from the cornea 5, which is essentially defined by an anterior surface 15 and a posterior surface 16 and also has an imaging effect due to its curvature. The optical effect of the cornea 5 is determined by the radius of curvature R. CVThis is due to the anterior surface of the cornea. Partial figure a) only illustrates the refractive error; in reality, the more complex refractive errors mentioned above may be present. The following description also applies to these, however, the equations given may then sometimes include an additional angular dependence, even if this is not explicitly stated.

[0048] As is known, the correction of refractive errors is achieved, as shown in part b) of the Fig. Figure 4 shows a lens attachment 17 in the form of spectacles at a distance d. HS The lens 17 of the spectacles is positioned in front of the eye 3 from the vertex of the cornea 5. Its refractive power is B. BR so adjusted that it shifts the far point of the entire system, i.e., of glasses and eye, from the focal point F to the corrected focal point F*, which lies on the retina 14.

[0049] Regarding the nomenclature used in this description, it should be noted that the addition of an asterisk to quantities clarifies that these are quantities obtained after a correction. The focus F* is therefore the focus that exists after the optical correction shown in subfigure b) of the Fig. 4 is achieved through lens 17 of the glasses.

[0050] Under the justified assumption that a change in corneal thickness 5 essentially modifies the radius of curvature of the anterior corneal surface 15 facing the air, but not the radius of curvature of the posterior corneal surface 16 facing the interior of the eye, the radius of curvature R is changed by the volume removal CVThe anterior corneal surface 15 is modified. The cornea 5, with its reduced volume, has such a changed imaging effect that the corrected focus F* lies on the retina 14. After the correction, the anterior corneal surface 15* is altered, and refractive error correction is achieved even without glasses.

[0051] To determine the pattern of target points, the required curvature of the modified anterior corneal surface 15* is calculated. The starting point is the refractive power of the lens 17 of the spectacles, as determining the corresponding parameters is a standard procedure in optometry. For the refractive power B BR (φ) of lens 17 of the glasses, the following formula applies: BBR(φ)=Sph+Cyl⋅sin2(φ−θ).

[0052] In this equation, Sph and Cyl denote the correction values ​​to be achieved for spherical and astigmatic refractive errors, respectively, and θ denotes the position of the cylinder axis of the cylindrical (astigmatic) refractive error, as known to those skilled in optometry. Finally, the parameter φ refers to a cylindrical coordinate system of the eye and is measured counterclockwise when viewed from the eye, as is customary in ophthalmic optics. With the value B BR The curvature of the modified anterior corneal surface 15* is now set as follows: RCV*=1 / ((1 / RCV)+BBR / ((nc−1)⋅(1−dHS⋅BBR)))+F

[0053] In equation (2) n denotes c The refractive power of the corneal material. The corresponding value is usually 1.376; d HS denotes the distance at which a pair of glasses with refractive power B can be worn. BRmust lie from the corneal apex in order to produce the desired refractive error correction using glasses; B BR denotes the previously mentioned refractive power of the glasses according to equation (1). The value for refractive power B BR It can also detect refractive errors that go beyond normal spherical or cylindrical correction. B BR (and therefore automatically also R) CV *) then have additional coordinate dependencies.

[0054] The correction factor F takes into account the optical effect of changes in corneal thickness and can, to a first approximation, be considered a constant factor. For highly accurate correction, the factor can be calculated according to the following equation: F=(1−1 / nc)⋅(dc*−dc). dc and dc* represent the corneal thickness before and after optical correction, respectively. For precise determination, R is calculated. CV * iteratively, by taking the difference (R) from the i-th calculationCV * - R CV The value (dc* - dc) is inferred, and the resulting value is applied to the thickness change in the (i+1)th calculation. This process can continue until a termination criterion is met, for example, if the difference in the thickness change result between two consecutive iterations falls below a predefined limit. This limit could be defined, for instance, as a constant difference corresponding to a refractive correction accuracy appropriate for the treatment.

[0055] If the change in corneal thickness is neglected, which is perfectly acceptable for a simplified procedure, the correction factor F in equation (2) can also be set to zero for a simplified calculation, i.e., neglected and omitted. Surprisingly, the following simple equation for the refractive power of the modified cornea 5* is obtained: BCV*=BCV+BBR / (1−BBR⋅dHS)

[0056] From this equation, the expert can easily derive the following using equation B. CV * = (n-1) / R CV * the radius R CV * of the anterior corneal surface 15*, which must be present after the modification to obtain the desired refractive error correction, to: R CV * = 1 / ( (1 / R CV ) + B BR / ((n c -1) · (1 - d HS · B BR ))).

[0057] For the volume whose removal causes the above-mentioned change in curvature of the anterior corneal surface 15, the boundary surface is now defined that isolates the volume. It is preferably taken into account that the diameter of the area to be corrected, and thus the diameter of the volume to be removed, should extend as far as possible over the pupil size when the eye is dark-adapted.

[0058] In a first approach, a free surface is defined using numerical methods known to those skilled in the art. This free surface circumscribes a volume whose removal causes the change in curvature. For this purpose, the change in thickness required for the desired curvature modification is determined along the z-axis. From this, the volume is obtained as a function of r and φ (in cylindrical coordinates), and from this, in turn, its boundary area is calculated.

[0059] A simple analytical calculation yields the following second variant, in which the boundary surface of the volume is constructed from two sub-surfaces: an anterior sub-surface facing the corneal surface 15 and an opposing posterior sub-surface. The corresponding ratios are shown. Fig. 5. The volume 18 is bounded towards the anterior corneal surface 15 by an anterior cut surface 19, which is at a constant distance d F This anterior cut surface 19 lies beneath the anterior corneal surface 15. Analogous to laser keratomes, this anterior cut surface 19 is also referred to as the flap surface 19, since it serves, in combination with an opening incision towards the periphery, to lift a lamella in the form of a "flap" from the underlying cornea 5. This method of removing the previously isolated volume 18 is, of course, also possible here.

[0060] The anterior cut surface 19 has a curvature profile that curves around the Funder the anterior corneal surface 15. If this is spherical, a radius of curvature can be specified for the flap surface 19, which is around d F is smaller than the radius of curvature R CV As will be described later for preferred variants, when generating the cut surface 19 using a contact lens, care can be taken to ensure that the anterior corneal surface 15 is spherical at the time of cut surface generation, so that the pattern of target points results in a spherical cut surface. Although the relaxation of the eye 3 after removal of the contact lens may then lead to a non-spherical cut surface 19, it nevertheless maintains a constant distance from the anterior corneal surface 15 or 15*.

[0061] Posteriorly, the volume 18 to be removed from the cornea 5 is bounded by a posterior cutting surface 20, which generally does not have a constant distance to the anterior corneal surface 15. The posterior cutting surface 20 will therefore be shaped such that the volume 18 is in the form of a lenticule, which is why the posterior cutting surface 20 is also referred to as the lenticule surface 20. Fig. In 5, it is an example of a myopia correction, also a spherical surface with a radius of curvature R. L drawn, whereby in general the center of this curvature does not coincide with the center of curvature of the in Fig. 5 also coincides with the spherical anterior corneal surface 15. In hyperopia correction, R L greater than R CV - d F .

[0062] Fig. Figure 6 shows the conditions after removal of volume 18. The radius of the modified anterior corneal surface 15* is now R CV* and can be calculated, for example, according to the equations described above. The central thickness d L The extracted volume 18 is decisive for the change in radius, as Fig. Figure 7 illustrates this. In this figure, the height h is also shown as a further dimension. F the spherical cap defined by the anterior cut surface 19, the height h L the spherical cap defined by the posterior cross-sectional surface 20 and the thickness d L The volume to be removed is shown in 18.

[0063] The posterior cut surface 20, due to the constant distance between the anterior corneal surface 15 and the anterior cut surface 19, determines the curvature profile of the anterior corneal surface 15* after removal of volume 18. Thus, the posterior cut surface 20 will have an angle-dependent radius of curvature, for example, in the case of a refractive error correction that takes cylindrical parameters into account. For the in Fig. The lenticular area shown in Figure 7 (20) applies generally: RL(φ)=RCV*(φ)−dF, or in cylindrical coordinates (z, r, φ) zL(r,φ)=RL(φ)−(RL2(φ)−r2)1 / 2+dL+dF.

[0064] Without considering astigmatism, the dependence on φ is eliminated, and the lenticule surface 20 is spherical. However, assuming the need for cylindrical refractive error correction, the lenticule surface 20 typically has different radii of curvature on different axes, although these usually share the same vertex.

[0065] This automatically makes it clear that in the case of myopic cylinder correction, the theoretical line of intersection between flap surface 19 and lenticule surface 20 does not lie in a plane, i.e., at constant z-coordinates. The smallest radius of curvature of the lenticule surface 20 is at φ = θ + π / 2, the largest naturally on the axis θ of the cylindrical refractive error, i.e., at φ = θ. In the case of farsightedness correction, the representation of the Fig. 7. The vertex of flap surface 19 and lenticular surface 20 theoretically coincides, and lenticular surface 20 is more curved than flap surface 19. The thickness d L The lenticule thickness is determined as the central lenticule thickness in myopia.

[0066] The volume 18, which can be considered a lenticule, theoretically has an intersection line at its edge between the lenticule area 20 and the flap area 19 in the case of myopia correction. In hyperopia correction, there is always a finite edge thickness, since the lenticule area 20 is less curved than the flap area 19. Here, however, the central lenticule density is theoretically zero.

[0067] In addition to the flap surface 20 and the lenticular surface 19, an additional boundary surface is provided, which limits the bounded volume 18 of flap surface 20 and lenticular surface 19 at its edge. The section of this boundary surface is also performed with the pulsed laser beam. The structure of the boundary surface is subsequently described based on the Fig. 12a-c explained.

[0068] The configuration of volume 18 shown in the figures, as bounded by an anterior cut surface 19 at a constant distance to the corneal anterior surface 15 and a posterior cut surface 20, is only one variant for limiting volume 18. However, it has the advantage that the optical correction is essentially determined by only one surface (the lenticule surface 20), so that the analytical description of the other part of the interface is simple.

[0069] Furthermore, optimal safety margins are given with regard to the distance of the volume to the anterior corneal surface 15 and the posterior corneal surface 16. The residual thickness d FThe distance between the anterior section surface 19 and the anterior corneal surface 15 can be constantly set to a value of, for example, 50 to 200 µm. In particular, it can be chosen such that the pain-sensitive epithelium remains within the flap formed by the flap surface 19 beneath the anterior corneal surface 15. Furthermore, the formation of the spherical flap surface 19 is consistent with previous keratometer sections, which is advantageous for the acceptance of the method.

[0070] After creating the cut surfaces 19 and 20, the isolated volume 18 is then removed from the cornea 5. This is shown schematically in Fig. Figure 8 illustrates that the cut surfaces 19 and 20 are generated by the action of the treatment laser beam incident in a focus cone 21, for example by arranging plasma bubbles in succession, so that in a preferred embodiment the flap cut surface 19 and the lenticule cut surface 20 are generated by suitable three-dimensional adjustment of the focus position of the pulsed laser radiation 2.

[0071] Alternatively, in a simplified embodiment, the flap surface 19 can be formed by pulsed laser radiation using target points that define the curved cut surface 19 at a constant distance from the anterior corneal surface 15, and the removal of the volume 18 is achieved by laser ablation, for example, using an excimer laser beam. For this purpose, the lenticule surface 20 can be defined as the ablation boundary, although this is not strictly necessary. The treatment device 1 then operates like a known laser keratome, except that the cut surface 19 is generated on a curved cornea. The features described above and below are also possible in such variants, particularly with regard to the determination of the boundary surface, its geometric definition, and the determination of control parameters.

[0072] If both the lenticule area 20 and the flap area 19 are created using pulsed laser radiation, it is advantageous to form the lenticule area 20 before the flap area 19, since the optical result for the lenticule area 20 is better (if not only achievable) if no change in the cornea 5 has yet occurred above the lenticule area 20.

[0073] The removal of the volume 18 isolated by the pulsed laser radiation can, as in Fig. 8 indicated, can be achieved by a marginal cut 22, which allows the volume 18 to be directed towards a Fig. to pull out the indented arrow 23. Alternatively, the marginal incision 22 can be designed such that it connects the anterior cut surface 19, i.e., the flap surface 19, to the anterior corneal surface 15 in the form of a ring, although the marginal incision does not completely encircle the cornea by a full 360°. The lamella thus isolated remains in contact with the remaining corneal tissue 5 in a narrow area. This connecting bridge then serves as a hinge to allow the otherwise isolated lamella to be folded away from the cornea 5 and the resulting accessible, already isolated volume 18 to be removed from the rest of the cornea 5. The position of the connecting bridge can be specified when generating the control data or the target points. The described procedure orFrom this perspective, the device thus achieves the isolation of volume 19 within the cornea 5 and the creation of a flap connected to the rest of the cornea via a tissue bridge, acting as a lid over the volume. The lid can be folded back and volume 18 removed.

[0074] For generating the section surfaces 19 and 20, the target points can now be arranged in a variety of ways. For example, WO 2005 / 011 546 A1 describes the prior art for generating section surfaces in the cornea, where special spirals can be used that run, for instance, around a principal axis that is essentially perpendicular to the optical axis (z-axis) in a helix-like manner. The use of a scan pattern that arranges the target points row by row is also known (see WO 2005 / 011 545 A1). These methods can, of course, be used to generate the section surfaces defined above.

[0075] The edge surface mentioned above is in the Fig. 9a and Fig. 9b can be viewed in more detail. Elements that have already been explained using other figures are marked with the same reference symbols in these figures, so their explanation may be omitted.

[0076] Fig. Figure 9a shows a top view of the anterior corneal surface 15 with the flap area 19 and the lenticule area 20 (whose edge is shown with a dashed line) as well as the marginal incision 22 in the case of hyperopia correction. Further details are shown in Fig. 9a A transition zone can be seen between the edge of the lenticular surface 20 and the flap surface 19, which is reached by a boundary surface 24. This boundary surface 24 is in Fig. 9b clearly shows a cross-sectional view through the representation of the Fig. 9a along lines AA.

[0077] The edge surface 24 effects the transition from the lenticular surface 20 to the flap surface 19. In the embodiment of Fig. 9b is designed as a conical surface that is more inclined than a (in top view of Fig. 9a) conical surface which would be perpendicular to the anterior corneal surface 15 or to the flap surface 19 running parallel to it. The marginal incision 22, for example, has such a course, lying at an angle α with respect to the visual axis OA, which results in the aforementioned perpendicular course to the anterior corneal surface.

[0078] The edge surface 24, however, is more inclined, so that the width B, which the edge surface 24 has in top view in the direction of the optical axis OA, is larger than, for example, in the edge section 24. The corresponding angle β is therefore also larger than the angle α.

[0079] The Fig. 10a and Fig. Figure 10b shows the corresponding conditions in the case of a myopic lenticule, i.e., in the case of myopia correction. Here, too, the boundary surface 24 is present and leads to a finite edge thickness of the lenticule 18, which would not otherwise be the case due to the greater curvature of the lenticule surface 20 compared to the flap surface 10, since both surfaces would have a line of intersection at least in their continuation, i.e., the edge would end in a line of intersection.

[0080] The minimum thickness of lenticule 18, which in a hyperopic form according to Fig. 9b if the condition is present on or near the optical axis OA, it applies to a myopenlenticel according to Fig. 10b is also at the edge. Accordingly, the minimum thickness d is M in Fig. 10b is also shown at the edge.

[0081] Of course, the sectional views of the Fig. 9b and Fig. 10b is only descriptive for the entire lenticule if no higher-order correction, in particular no astigmatism, is present. If such a correction is present, the lenticule surface 20 is corrected accordingly, deviating from sphericity, which, in a manner obvious to a person skilled in the art, also affects the boundary surface 24.

[0082] The Fig. 11a and Fig. 11b finally show conditions corresponding to those of Fig. 9a and Fig. 9b, however, here the edge cut 22, which is created to expose the lenticel 18, extends over a much larger angular range than in Fig. 9 and Fig. 10.

[0083] The Fig. Figures 9 to 11 show an edge surface 24, which is executed as an oblique section. However, the edge surface 24 can also have a structure that deviates from such a straight course in cross-sectional view. This is exemplified in the Fig. 12a to d shown. Herein is Fig. 12a a sectional view similar to that of the Fig. 9b, Fig. 10b or Fig. 11b again. The Fig. Figures 12b to 12d show the one in the Fig. 12a dotted section enlarged and represent different variants for the structure of the boundary surface 24.

[0084] According to Fig. In section 12b, the edge surface 24 consists of two sections 25 and 26, which are essentially straight in cross-section. The first section 25 runs perpendicularly into the flap surface 19. The height of the first section 25 results in a thickness d Rof the edge. This thickness is preferably selected in the range of 5 to 10 µm and ensures that no fragments break off in the area of ​​the edge surface 24 when the lenticule 18 is removed. Such fragments would have a significantly adverse effect on ingrowth and would lead to undesirable regression. In order to achieve gentle attachment of the corneal lamella 27 isolated by the flap incision 19, despite the first section 25 being perpendicular to the flap surface 19, when the lenticule-shaped volume has been removed, the second section 26 of the edge surface 24 in the embodiment of the Fig. 12b has an oblique course towards the visual axis. This oblique course results in a width B that is significantly larger than would be the case with a continuous edge 24 running perpendicular to the flap surface 19.

[0085] Fig. Figure 12c shows a modification of the structure of the boundary surface 24 of the Fig. 12b, in which a continuously curved second section 26 is formed on the first section 25, which runs perpendicularly into the flap surface 19, by which the edge between the lenticule surface 20 and the flap surface 19 is rounded in the area facing away from the anterior corneal surface 15. The perpendicular insertion of the first section 25 in turn represents a minimum edge thickness d R secure, which prevents the tearing of tissue pieces at the lenticule edge during the removal of the lenticule tissue.

[0086] This is also true for the boundary structure according to Fig. 12d, which is S-shaped, is reached, with the first section 25 again running perpendicularly into the flap surface 19. Due to the S-structure, the cross-sectional view of the edge surface 24 in this embodiment has an inflection point, and the second section 26 preferably also ends at a right angle in the lenticular surface 20.

[0087] The contact lens has the further advantage that, by pressing it against the spherical underside 26, the anterior corneal surface 15 is automatically also spherical. The anterior cut surface 19, located at a constant distance below the anterior corneal surface 15, is thus also spherical when the contact lens is pressed against it, which leads to considerably simplified control. Therefore, completely independent of other features, it is preferable to use a contact lens with a spherical underside and to limit the volume by an anterior cut surface 19 and a posterior cut surface, the anterior cut surface being a spherical surface at a constant distance d. F is generated under the anterior corneal surface 15. The posterior cut surface has a curvature profile which, when the eye is relaxed (i.e., after removing the contact lens), extends to the distance d. FThe target area on the anterior corneal surface corresponds to the desired refractive error correction. The same applies to the definition of the target points and the surgical procedure.

Claims

[1] Treatment device for surgical hyperopia correction of the eye (3), wherein the treatment device (1) comprises a laser device (L) controlled by a control unit (12), which separates corneal tissue by emitting laser radiation (2), wherein the control unit (12) is configured to control the laser device (L) to emit the laser radiation (2) into the cornea (5) in such a way that a lenticular volume (18) is isolated in the cornea (5), the removal of which from the cornea (18) effects the desired hyperopia correction, wherein the control unit (12), when controlling the laser device (L), specifies the lenticular volume (18) such that it has a posterior surface (20) and an anterior surface (19) which are connected to each other in a transition zone (24) which has a width of at least 0.1 mm, characterized by, that the marginal surface (24) has a first section (25) that opens largely perpendicularly into the anterior surface and a second section (26) that is more inclined towards the visual axis (OA). [2] Method for generating control data for a laser device (L) of a treatment device (1) for surgical hyperopia correction of the eye (3), which separates corneal tissue by emitting laser radiation (2), wherein the control data during operation control the laser device (L) to deliver the laser radiation (2) into the cornea (5) in such a way that a lenticule-shaped volume (18) is isolated in the cornea (5), the removal of which from the cornea (18) effects the desired hyperopia correction, characterized by , that the control data specify the lenticular volume (18) such that it has a posterior surface (20) and an anterior surface (19) which are connected in a transition zone (24) which has a width of at least 0.1 mm. [3] Device or method according to any one of the above claims, characterized by , that the edges of the posterior surface (20) and the anterior surface (19) in the transition zone are connected via a ring-shaped boundary surface (24), wherein the boundary surface (24) in projection along the visual axis (OA) has a ring width (B) that is larger than that which in the same projection would be a straight line perpendicular to the edge of the posterior or the anterior surface (20, 19) on the respective surface and connects the anterior surface (19) with the posterior surface (20) or with its imaginary continuation. [4] Device or method according to any one of the above claims, characterized by , that the anterior surface (19) is at a constant distance d F to the anterior corneal surface (15) and the posterior surface is curved and has a radius of curvature R L = R CV * - d F has, where R CV * the following equation suffices RCV*=1 / ((1 / RCV)+BBR / ((nc−1)⋅(1−dHS⋅BBR)))+F, and R CV the radius of curvature of the cornea (5) before removal of volume (18), n c the refractive power of the corneal material (5), F is a correction factor, B BR the refractive power of spectacles suitable for correcting refractive errors (17), as well as d HS the distance at which the glasses (17) with refractive power B BR would have to be located in front of the corneal vertex in order to achieve the desired refractive error correction using the glasses (17). [5] Device or method according to claim 4, characterized by , that F=(1−1 / nc)⋅(dc*−dc) applies, where dc and dc* denote the thickness of the cornea (5, 5*) before and after removal of the volume (18), respectively, and the radius R CV * can be calculated iteratively by taking the difference (R) at each iteration step CV * - R CV) is inferred from a change in thickness (dc* - dc) and the corresponding result obtained for the change in thickness is used in the calculation of R CV * will be applied in the next iteration step. [6] Device or method according to claim 1, characterized by that the first section has a height d R of more than 5 µm, in particular of at least 10 µm. [7] Device or method according to claim 1 or 6, characterized by , that the second section (26) lies at an angle of 80° to 100° to the direction of the visual axis (OA). [8] Device or method according to claim 7, characterized by , that the second section (26) is concave, with respect to the point of passage of the visual axis (OA) through the anterior corneal surface (15). [9] Device or method according to any one of the above claims, characterized by, that the transition zone has a first section which opens into the anterior surface at an angle of 80° to 100° to the visual axis or perpendicularly. [10] Device or method according to any one of the above claims, characterized by that the transition zone has a second section that is curved. [11] Device or method according to claim 10, characterized by that the second section has the form of a rounded shape. [12] Device or method according to any one of the above claims, characterized by that the transition zone lies outside the dark-adapted pupil of the eye. [13] Device or method according to any one of the above claims, characterized by that the edge thickness of the lenticule is less than 10 µm.

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