DE102006053119A1 - Treatment device for vision correction has control device inserting allowance dependent on target points before correction of focusing position error - Google Patents

Abstract

The treatment device (1) has a control device which, when the target points are predicted for the focusing error of the laser beam (2) leading to a deviation between the preset and actual positions of the target points, inserts an allowance to correct for this, which is dependent on the target points before the correction of the focusing position error.

Description

The invention relates to a treatment device for the operative correction of defective vision of a patient's eye, which has a laser device controlled by a control device, which device is used for isolating one in the cornea ( 5 ) ( 18 ) separates corneal tissue by irradiation of laser radiation, wherein the control device by presetting lying in the cornea target points the laser device for focusing the laser radiation in the cornea ( 5 ).

The invention further relates to a method for generating control data for a laser device of a treatment device for operative correction of the refractive error of a patient's eye, which device is used for isolating one in the cornea ( 5 ) ( 18 ) separates corneal tissue by irradiating focused laser radiation, wherein the control data during operation of the treatment device of the laser device predetermine target points for the focused laser radiation that lie in the cornea.

Finally, the invention relates to a method for the operative correction of defective vision of a patient's eye, wherein a volume ( 18 ) in the cornea ( 5 ) is isolated and this is focused on the separation of corneal tissue laser radiation on in a pattern in the cornea lying target points.

Of the classical way to correct the defective vision of the human Eye is the glasses. Meanwhile, however, is increasingly refractive Surgery used by changing the cornea one Defective vision correction causes. The goal of the surgical methods is It is about to specifically change the cornea, so the refraction of light to influence. Therefor Different operating methods are known. Most common is currently the so-called laser in situ keratomileusis, which is also abbreviated LASIK. At first a corneal lamella becomes one-sided from the surface of the cornea solved and worked to the side. The release of this lamella can be done by means of a mechanical Mikrokeratoms, or also by means of a so-called laser keratome, as e.g. from intralase Corp. Irvine, USA. After the slat is released and to The LASIK operation is the application provided by an excimer laser, the thus exposed corneal tissue by Ablation ablates. Having volume in the cornea in this way has evaporated, the corneal lamella is restored to the original Square folded back.

The Application of a laser keratome to expose the blade is advantageous because the risk of infection is reduced and the quality of cut is increased. In particular, the lamella can be made with a much more constant thickness become. Also, the cut is potentially smoother, resulting in later optical interference this remains even after the operation remaining limit area.

at the creation of a cut surface in the cornea by laser radiation run in the tissue in succession several processes initiated by the pulsed laser radiation become. Is the power density of the radiation above a pulse Threshold, it comes to an optical breakthrough, which in the Cornea e.g. generates a plasma bubble. The plasma bubble grows after emergence the optical breakthrough by expanding gases. Will the optical breakthrough not maintained, it will be in the plasma bubble generated gas absorbed by the surrounding tissue, and the bubble disappears again. There are also tissue separation effects possible without the plasma bubble Act. For the sake of simplicity, all such processes are covered here the term "optical breakthrough", i. This term is not only meant for the optical breakthrough, but also the resulting effects in the cornea.

For tissue separation, the laser radiation is pulsed applied, the pulse length is usually below 1 ps. As a result, the power density necessary for triggering the optical breakthrough is achieved for the respective pulse in a narrow spatial area. The US 5984916 shows in this regard clearly that the spatial range of the optical breakthrough (in this case, the interaction generated) strongly depends on the pulse duration. A high focus of the laser beam in combination with the mentioned short pulses allows it to use the optical breakthrough pinpoint in the cornea.

to Section production is a series of optical breakthroughs at predetermined Make so created by that the cut surface is trained. When mentioned Laserkeratom forms the cut surface before the use of the Laser ablation folding lamella.

Of course, the precision with which the cut surface is produced is ultimately crucial for optical correction. This applies in particular to advanced laser-surgical ametropia correction methods, in which a volume lying in the cornea is isolated by a three-dimensional sectional area and thus made removable. Unlike the laser keratome, the position of the cut surface is directly relevant for optical correction. In the conventional LASIK method, however, is exclusive Lich the precision with which the laser ablation is operated, important for the quality of the optical correction, which is already recognizable that the generation of the corneal flap is also possible with a relatively coarse mechanical knife and is practiced in a large variety of operations or was.

It is therefore an object of the invention to provide a treatment device or a method of the type mentioned in such a way that a Schnittflächenerzeugung with high precision can be done.

The Invention carries the fact that optical Systems are usually not perfect. An error in focusing The laser radiation in the cornea affects the cutting surface production out. This is especially true for a mistake of focus position, supposedly positioned in a plane Focus positions actually not in a plane, but in a curved surface. at the known laser keratoms this aspect does not matter because the generation of the lamella exposing cut for the optical quality the correction is meaningless. But now that's to be isolated and then to remove volumes entirely by focusing the pulsed laser radiation is defined, sees the treatment device according to the invention or the inventive method that focus position error, when focusing the laser radiation, which is preferably pulsed is applied, a deviation between given and actual Position of the target points, by a corresponding opposing Taken into account becomes.

Of the Vorhalt causes a predistortion of the target points such that in combination with the focus position error the target points are back in place, which are desired when using the treatment device.

Of the Vorhalt can conveniently be determined by a correction table or function which the focus position error dependent indicates the location of the respective destination point. This table or Function can for the respective device type uniform prescribed or, for the sake of precision is preferred for the respective device individually be determined, for example by the device manufacturer or after installation of the device User.

With justifiable effort may be the optics used in focusing the Laser radiation used to be formed so that the focus position error is essentially an axial focus position error and rotationally symmetric to the optical axis. It is for this variant then prefers that each lead a shift causes the respective target point parallel to the optical axis and that the Correction table or function of only one axial and one radial coordinate depends if the target points are described in cylindrical coordinates. Conveniently, the origin of the cylindrical coordinate in the puncture point of the optical axis through the anterior surface of the cornea.

to Determining the target points can be an analytical definition of the target point quantity chosen become. This falls especially easy when a track is laid along the Focusing the laser radiation is to adjust the desired cutting surface then isolate the volume isolated. The target points only have to selected from the points of the track become. Since the correction for the focus position error in the Usually not as a transcendental, analytical or even linear function but in most cases at best an interpolation by polynomials or splines possible will be, it is preferable to the target points before the correction to determine from the railway. This procedure has the advantage that a simple, Computing effort used to determine the target points can be.

The Simplicity is further enhanced when the train passes through one or more several functional equation (s) is set, so that the evaluation of Function equation (s) at different nodes that supplies the target points. Until then, that's a transcendent description the beam deflection possible, the naturally one much less computational burden than if one size Amount of destination points is managed. The actual destination coordinates are only available after the evaluation of the function equation (s). They then represent control data that is used in the operation of the treatment device Find application. Of course, these can Control data can still be edited to device-specific Adjustments, e.g. Determination of corresponding voltage levels to the coordinates, previously determined amplitude or phase behavior of galvanometer mirrors etc., to take into account.

As already mentioned, the focus of the generally pulsed laser radiation is adjusted in three dimensions to produce the cut surface. Therefore, as a rule, a two-dimensional deflection of the laser radiation, for example by galvanometer mirrors, combined with simultaneous focus adjustment in the third spatial direction, for example by a telescope, is combined. The adjustment of the position of the focus is of course crucial to the accuracy with which the cut surface can be created by the target points. It has proved to be useful for this purpose to use a contact glass, which is placed on the eye and this fixed. Such Contact glass is also common in the laser keratoms mentioned above. The contact glass also regularly has the function of giving the corneal anterior surface a known shape. In the case of the known laser keratoms, the shape is a plane, ie the eye is flattened in the region of the cornea. Since this is relatively uncomfortable for the patient, approaches that laser-surgically isolate a volume in the cornea have already described a contact lens with a curved contact surface facing the eye. Such a contact lens then gives the corneal anterior surface a known curvature. Of course, the curvature inevitably leads to a deformation of the cornea. This deformation is the greater, the greater the curvature of the contact surface deviates from the actual corneal curvature of the eye of the patient. In order to work as possible with a uniform contact surface curvature, it is therefore advantageous to consider the corneal deformation that occurs in the application of a curved contact glass in the indication of the target points, so regardless of the degree of deformation, the target points ultimately for the free, ie not be deformed by the contact glass eye at the desired locations and thereby ultimately a desired interface for the volume to be removed is established.

The consideration The deformation of the cornea may, on the one hand, be based on the target points, i. if the individual coordinates of the destination points are fixed, take place. On the other hand, the deformation can also be due to a corresponding transformation the path along which the focus is to be adjusted takes into account be worn. It is therefore preferred that for the treatment device the controller in determining the path or the destination points accounted for a deformation of the cornea of the eye during the Irradiation of the pulsed laser radiation occurs, in particular by a contact glass justified is. The same applies to the inventive method.

Especially if the orbit indicated by transcendental equations is, it is computationally particularly favorable, first the course related set on the undeformed eye and then the track to compensate to modify the deformation of the cornea of the eye. In one The last step is the evaluation of the train function (s) certain interpolation points done to the coordinates for to determine the target points, which then in a final step regarding the focus position error can be corrected as described.

A Particularly simple arithmetical treatment is obtained when the target points are arranged along tracks that run in a spiral. For example can the cut surface to be created, which isolate the volume into two sub-areas, one anterior and a posterior surface. The faces can each by adjusting the focus along a spiral path.

The inventive method to prepare the control data can without human involvement accomplished become. In particular, it can be done by a computer from the corresponding specifications, for example from the functional defined trajectories the control data determined by the interpolation point selection matching the adjustment speed of the target system to the application determines the control data representing laser device. Especially is the involvement of a physician in the determination of the tax data in no way required, since with the determination of the control data yet no therapeutic intervention is connected. This one finds only when the previously determined control data is used.

The The invention will be described below with reference to the drawings for example, even closer explained. In the drawings shows:

1 a schematic representation of a treatment device or a treatment device for ametropia correction,

1a a schematic representation of the structure of the treatment device of 1 .

2 a schematic representation of the introduction of pulsed laser radiation into the eye in the refractive error correction with the treatment device of 1 .

3 a further schematic representation of the treatment device of 1 .

4 in sub-figures (a), (b) and (c) are schematic sectional views to illustrate the need for correction in the human eye with defective vision,

5 a schematic sectional view through the cornea showing a volume to be removed for correction of ametropia,

6 a section through the cornea after removal of the volume of the 5 .

7 a sectional view similar to the 5 .

8th a schematic sectional view through the cornea to illustrate the volume removal,

9 a plan view of a spiral Trajectory used to isolate the volume of 5 . 7 and 8th is used,

10 an enlarged view of the trajectory of 9 . 11 an alternative trajectory for the correction of even cylindrical vision defects,

12 a schematic representation for explaining the function of a contact glass in the treatment device of 1 .

13 to 15 schematic representations regarding the effects of the contact lens by deformation of the cornea,

16 and 17 Schematic representation with respect to the approximation of the volume posterior limiting surface in the case of even cylindrical misalignment corrections,

18 a schematic representation of a in the determination of control data for the treatment device of 1 used focus position error correction and

19 a schematic representation of the process in the preparation and implementation of ametropia correction.

1 shows a treatment device 1 for an ophthalmological procedure similar to that in the EP 1159986 A1 or the US 5549632 is similar. The treatment device 1 effected by means of a treatment laser radiation 2 an ametropia correction on one eye 3 a patient 4 , Defective vision may include hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism with hyperopia in one direction and myopia in a direction perpendicular thereto), aspheric errors, and higher order aberrations. The treatment laser radiation 2 is pulsed into the eye in the described embodiment 3 focused laser beam applied. The pulse duration is eg in the femtosecond range, and the laser radiation 2 works by means of non-linear optical effects in the cornea. The laser beam has, for example, 50 to 800 fs short laser pulses (preferably 100-400 fs) with a pulse repetition frequency between 10 and 500 kHz. The modules of the device 1 be controlled in the described embodiment of an integrated control unit, which, however, may of course be designed independently.

Before the use of the treatment device is the refractive error of the eye 3 measured with one or more measuring devices.

1a shows schematically the treatment device 1 , In this variant, it has at least two devices or modules. A laser device L outputs the laser beam 2 on the eye 3 from. The operation of the laser device L takes place fully automatically, ie the laser device L starts the deflection of the laser beam in response to a corresponding start signal 2 and thereby creates cut surfaces, which are constructed in a manner to be described and isolate a volume in the cornea. The control data required for the operation is previously received by the laser device L from a planning device P as a control data record via unspecified control lines. The transmission takes place before the operation of the laser device L. Of course, communication can also be wireless.

alternative For a direct communication it is also possible to use the planning unit P spatially separated from the laser unit L to arrange and a corresponding data transmission channel provided.

Preferably, the control data set becomes the treatment device 1 transmitted and further preferably, an operation of the laser device L is locked until the laser device L is present a valid control data record. A valid control record may be a control record that is principally for use with the laser device L of the treatment device 1 suitable is. In addition, the validity can also be linked to the fact that further tests are passed, for example, if in the control record additionally specified information about the treatment device 1 For example, a device serial number, or the patient, such as a patient identification number to match other information that has been read, for example, at the treatment device or entered separately as soon as the patient is in the correct position for the operation of the laser device L.

The planning unit P generates the control data set that is provided to the laser unit L for performing the operation from measurement data and refractive error data that were determined for the eye to be treated. They are the planning unit P supplied via an interface S and come in the illustrated embodiment of a measuring device M, the patient's eye 4 measured before. Of course, the measuring device M in any way the corresponding measurement and refractive error data to the planning device P transmit.

Transmission can take place by means of memory chips (eg via USB or memory stick), magnetic memories (eg floppy disks), by radio (eg WLAN, UMTS, Bluetooth) or wired (eg USB, Firewire, RS232, CAN bus, Ethernet etc.). The same applies, of course, in terms of data transmission between planning device P and laser device L.

A direct radio or wire connection of the measuring device M with the treatment device 1 In terms of data transmission, which can be used in a variant, has the advantage that the use of false measurement and refractive error data is excluded with the greatest possible certainty. This applies in particular if the transfer of the patient from the measuring device M or the measuring devices to the laser device L takes place by means of a (not shown in the figure) storage device which cooperates with the measuring device M and the laser device L so that the respective devices recognize if the patient 4 in the respective position for measuring or introducing the laser radiation 2 is. With a transfer of the patient 4 from the measuring device M to the laser device L can at the same time also the transmission of measurement and refractive error data to the treatment device 1 respectively.

It is preferably ensured by suitable means that the planning device P is always the patient 4 generated tax record and an erroneous use of an incorrect tax record for a patient 4 is as good as impossible.

The mode of action of the laser beam 2 is in 2 indicated schematically. The treatment laser beam 2 is by means of unspecified optics in the cornea 5 of the eye 6 focused. This results in the cornea 5 a focus, a spot 6 covered 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 at the respective spot 6 an optical breakthrough in the cornea 5 generate, which in turn a in 2 schematically indicated plasma bubble initiated. This will cause this laser pulse in the cornea 5 Tissue isolated. When a plasma bubble is formed, the tissue layer separation comprises a larger area than the spot 6 which the focus of the laser radiation 2 although the conditions for generating the breakthrough are only achieved in focus. So that an optical breakthrough of each laser pulse is generated by each laser pulse, the energy density, ie the fluence of the laser radiation, must be above a certain, pulse length-dependent threshold value. This connection is the expert from the example of DE 695 00 997 T2 known.

Alternatively, a tissue-separating effect by the pulsed laser radiation can also be generated in that a plurality of laser radiation pulses are emitted in one area, wherein for several laser radiation pulses, the spots 6 overlap. It then act together several laser radiation pulses to achieve a tissue-separating effect.

The type of tissue separation that the treatment device 1 However, is not relevant to the following description, it is only essential that pulsed treatment laser radiation 2 is used. For example, a treatment device 1 used as they are in the WO 2004/032810 A2 is described. It is also essential that a multiplicity of laser pulse foci form a cut surface in the tissue, the shape of which depends on the pattern with which the laser pulse foci are arranged in the tissue. The pattern specifies target points for the focal position at which one or more laser pulses are emitted and defines the shape and position of the cut surface. For the methods and devices explained below, the pattern of the target points is of importance and will be described in more detail.

In order to carry out an ametropia correction, the pulsed laser radiation is used to make an area within the cornea 5 Material removed by there tissue layers are separated, which isolate the material and then allow removal of material. The material removal causes a volume change in the cornea, which is a change in the optical imaging effect of the cornea 5 The result is that it is calculated so that the previously determined defective vision is / is corrected as much as possible. To isolate the volume to be removed, the focus of the laser radiation 2 on target points in the cornea 5 directed, usually in an area that lies below the epithelium and the Bowman's membrane and above the Decemet's membrane and the endothelium. The treatment device 1 has a mechanism for adjusting the position of the focus of the laser radiation 2 in the cornea 5 on. This is schematically in 3 shown.

In 3 are elements of the treatment device 1 entered only insofar as they are necessary for understanding the focus adjustment. The laser radiation 2 becomes, as already mentioned, in a focus 7 in the cornea 5 bundled, and the location of the focus 7 in the cornea is adjusted, so that focused on the cutting surface generation at different locations energy from laser radiation pulses into the tissue of the cornea 3 will register. The laser radiation 2 is from a laser 8th provided as pulsed radiation. An xy scanner 9 , which is realized in a variant by two substantially orthogonally deflecting galvanometer, directs the laser 8th coming laser beam from two-dimensional, so that after the xy scanner 9 a deflected laser beam 10 is present. The xy scanner 9 thus causes an adjustment of the position of the focus 7 substantially perpendicular to the main direction of incidence of the laser radiation 2 in the cornea 5 , To adjust the depth position is next to the xy scanner 9 a z scanner 11 provided, which is designed for example as an adjustable telescope. The z scanner 11 ensures that the z position is the location of the focus 7 ie, whose position on the optical axis of incidence is changed. The z scanner 11 can the xy scanner 9 be downstream or upstream. The coordinates designated below by x, y, z thus refer to the deflection of the position of the focus 7 ,

For the functional principle of the treatment device 1 If the assignment of the individual coordinates to the spatial directions is not essential, for the sake of simpler description, however, z is always the coordinate along the optical axis of the incidence of the laser radiation 2 and x and y denote two mutually orthogonal coordinates in a plane perpendicular to the incident direction of the laser beam. The person skilled in the art is of course aware that a three-dimensional description of the position of the focus 7 in the cornea 5 can be done by other coordinate systems, in particular, it does not have to be a rectangular coordinate system. That's the xy scanner 9 To deflect each other at right angles is therefore not mandatory, rather, any scanner can be used, which is able to focus 7 to adjust in a plane in which the axis of incidence of the optical radiation is not. Thus, skewed coordinate systems are possible.

Furthermore, non-Cartesian coordinate systems can also be used to describe or control the position of the focus 7 can be used, as will be explained below. Examples of such coordinate systems are spherical coordinates (also referred to as spherical coordinates) and cylindrical coordinates.

To control the location of the focus 7 become the xy scanner 9 as well as the z-scanner 11 , which together realize a concrete example of a three-dimensional Fokusverstelleinrichtung, from a control unit 12 controlled via unspecified lines. The same applies to the laser 8th , The control unit 3 ensures a suitable synchronous operation of the laser 8th and the three-dimensional Fokusverstelleinrichtung, exemplified by the xy scanner 9 as well as the z-scanner 11 so that the location of the focus 7 in the cornea 5 is adjusted so that ultimately a material of a certain volume is isolated, the subsequent volume removal causes a desired ametropia correction.

The control unit 12 works according to given control data, which specify the target points for the focus adjustment. The control data is usually summarized in a control data record. This is in one embodiment, the coordinates of the target points as a pattern before, the order of the target points in the control record sets the sequence of focus positions and thus ultimately a trajectory (also abbreviated here as a train). In one embodiment, the control data record contains the target points as concrete setting values for the focus position adjustment mechanism, eg for the xy scanner 9 and the z-scanner 11 , For the preparation of the ophthalmological procedure, ie before the actual surgical procedure can be carried out, the target points, and preferably also their sequence, are determined in the pattern. There must be a preliminary planning of the surgical procedure to the effect that the control data for the treatment device 1 their application then one for the patient 4 optimal ametropia correction achieved.

At first, it is the case in the cornea 5 To specify to be isolated and later removed volume. As already shown 1a described requires a determination of the need for correction. 4 shows in subfigures a), b) and c) the optical conditions on the eye 3 of the patient 4 , Without deficiency correction, the situation shown in part a) is present. The cornea 5 works together with the eye lens 13 a focusing of an infinite object in a focus F, on the z-axis behind the retina 14 lies. On the one hand, the imaging effect derives from the relaxed eye lens when the eye is not acclimated 13 as well as the other part of the cornea 5 essentially through a corneal anterior surface 15 and a corneal back 16 is defined and also has an imaging effect due to their curvature. The optical effect of the cornea 5 is due to the radius of curvature R _{CV of} the anterior corneal surface. Sub-figure a) represents the defective vision only as an example, in reality, the above-mentioned more complex refractive errors can be present. However, the description below also applies to them, although the equations given may occasionally include an additional angle dependence, even if not expressly stated.

For vision correction is known manner, as in sub-figure b) the 4 shown, a lens attachment 17 in the form of glasses at a distance d _HS from the vertex of the cornea 5 in front of the eye 3 set. The Lens 17 the spectacles is adapted in their refractive power B _BR so that it shifts the far point of the entire system, ie from glasses and eye, from the focus point F to the corrected focus point F *, on the retina 14 lies.

With regard to the nomenclature used in this description, it should be noted that the addition of a star to quantities makes it clear that they are quantities obtained after correction. The focus F * is thus that focus which is present after the optical correction, which in subfigure b) of FIG 4 through the lens 17 the glasses are reached.

Under the justified assumption that a change in thickness of the cornea 5 essentially the radius of curvature of the air facing cornea front 15 modified, but not the radius of curvature of the inner lining of the cornea 16 , By the volume removal, the radius of curvature R _{CV of} the front _{surface of} the cornea becomes 15 modified. The cornea reduced by the volume 5 has such a modified imaging effect that the then corrected focus F * on the retina 14 lies. After correction, there is an altered corneal anterior surface 15 * before, and it is a vision correction even without glasses achieved.

For determining the pattern of the target points, therefore, the curvature of the modified corneal front surface to be achieved 15 * determined. The starting point is the refractive power of the lens 17 glasses, since the determination of the corresponding parameters is a standard procedure in ophthalmic optics. For the refractive power B _BR (φ) of the lens 17 the glasses have the following formula: B BR (φ) = Sph + Cyl · sin 2 (φ - θ) (1).

In this equation, Sph and Cyl denote the correction values to be realized for astigmatic refractive errors and θ the position of the cylindrical axis of the cylindrical (astigmatic) ametropia, as known to those skilled in optometry. Finally, the parameter φ refers to a cylindrical coordinate system of the eye and is counted counterclockwise looking at the eye, as is common in ophthalmic optics. The value B _BR now changes the curvature of the modified anterior corneal surface 15 * set as follows: R CV * = 1 / ((1 / R CV ) + B BR / ((N c - 1) (1 - d HS · B BR ))) + F (2)

In equation (2), n _c denotes the refractive power of the material of the cornea. The corresponding value is usually 1.376; d _HS denotes the distance at which spectacles with the refractive power B _BR must lie from the corneal vertex to produce the desired refractive error correction by means of spectacles; B _BR denotes the aforementioned refractive power of the spectacles according to equation (1). The indication of the refractive power B _BR can also detect vision defects that go beyond a normal spherical or cylindrical correction. B _BR (and thus automatically also R _CV *) then have additional coordinate dependencies.

The factor F expresses the optical effect of the change in thickness of the cornea and can be considered as a first approximation as a constant factor. For a highly accurate correction, the factor can be calculated according to the following equation: F = (1 - 1 / n c ) * (D C * - d C ) (3).

d _C or d _C * is the corneal thickness before or after the optical correction. For an accurate determination, a calculation of R _CV * is made iteratively, in the ith computation by deducing from the difference (R _CV * - R _CV ) the large (d _C * - d _C ) and the corresponding result obtained therefrom is applied for the thickness change in the (i + 1) -th calculation. This can be done until an abort criterion is met, for example, if the difference in the result for the thickness change in two consecutive iteration steps is below a correspondingly fixed limit. This limit can be set, for example, by a constant difference that corresponds to an accuracy of the refractive correction that is appropriate for the treatment.

Neglecting the change in thickness of the cornea, which is quite permissible for a simplified procedure, F can also be set equal to zero in equation (2) for a simplified calculation, ie neglected and omitted. Surprisingly, the following simple equation for the refractive power of the modified cornea is obtained 5 * : B CV * = B CV + B BR / (1 - B BR · d HS )

From this equation, the radius R _CV * of the front surface of the cornea is easily obtained for the person skilled in the art by means of the equation B _CV * = (n-1) / R _CV * 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 ) ))

For the volume, its removal, the above curvature change of the corneal anterior surface 15 causes, now the volume insulating interface is set. It should preferably be taken into account that the diameter of the region to be corrected and thus the diameter of the volume to be extracted should extend as far as possible over the pupil size in the case of a dark-adjusted eye.

In a first variant, numerical methods known to one skilled in the art are used Open space is defined, which circumscribes a volume whose removal causes the change in curvature. For this purpose, the thickness change is determined along the z-axis, which is necessary for the desired curvature modification. This results in the volume as a function of r, φ (in cylindrical coordinates) and, in turn, its interface.

A simple analytical calculation provides the following second variant, in which the interface of the volume is built up by two partial surfaces, one to the corneal surface 15 underlying anterior partial surface and an opposite posterior partial surface. The corresponding conditions shows 5 , The volume 18 is to the anterior corneal surface 15 through an anterior cut surface 19 bounded at a constant distance d _F below the corneal anterior surface 15 lies. This anterior cut surface 19 becomes in analogy to the laser keratome also as Flap surface 19 referred as it serves there, in combination with a opening section to the edge of the cornea 5 a lamella in the form of a "flap" of the underlying cornea 5 to be able to take off. This type of removal of the previously isolated volume 18 Of course, this is also possible here.

The anterior cut surface 19 has a curvature that is about d _F below the corneal anterior surface 15 lies. If this is spherical, it may be for the flap area 19 a radius of curvature which is smaller by d _F than the radius of curvature R _CV . As will be described later for preferred variants, in the production of the cut surface 19 be ensured by a contact glass, that the cornea front surface 15 is spherical at the time of the cut surface formation, so that the pattern of the target points causes a spherical cut surface. The relaxation of the eye 3 after removal of the contact glass then may indeed to a non-spherical cut surface 19 lead, but it still has constant distance to the corneal front surface 15 respectively. 15 * , This will be explained later.

Posterior is the volume 18 that is from the cornea 5 should be removed through a posterior cut surface 20 limited, which in principle not to the anterior corneal surface 15 can be at a constant distance. The posterior cut surface 20 will therefore be designed so that the volume 18 in the form of a lenticle, which is why the posterior cut surface 20 also as a lenticule area 20 referred to as. In 5 it is exemplarily drawn as also spherical surface with a radius of curvature R _L , whereby of course the center of this curvature does not coincide with the center of curvature of the in 5 also spherical corneal anterior surface 15 coincides.

6 shows the ratios after removal of the volume 18 , The radius of the modified corneal anterior surface 15 * is now R _CV * and can be calculated, for example, according to the equations described above. The thickness d _{L of} the extracted volume 18 is decisive for the radius change, such as 7 clarified. In this figure, as further sizes, the height h _F through the anterior cut surface 19 defined ball cap, the height h _L of the posterior cut surface 20 defined spherical cap and the thickness d _{L of} the volume to be removed 18 located.

The posterior cut surface 20 lays because of the constant distance between corneal anterior surface 15 and anterior cut surface 19 the curvature of the anterior corneal surface 15 * after removal of the volume 18 firmly. Thus, the posterior cut surface becomes 20 For example, in the case of a correction of defective vision taking into account a cylindrical parameter, an angle-dependent radius of curvature can have. For the in 7 shown lenticule area 20 generally applies: R L (φ) = R CV * (φ) - d F . or in cylindrical coordinates (z, r, φ) z L (r, φ) = R L (φ) - (R L 2 (φ) - r 2 ) 1.2 + d L + d F ,

Without regard to astigmatism, the dependence on φ and the lenticule area is eliminated 20 is spherical. The lenticule area 20 However, if one assumes the need for a cylindrical correction of defective vision, as a rule on different axes different radii of curvature, these of course usually having the same vertex.

This is further automatically clear that in the case of a cylinder correction, the theoretical cutting line between flap area 19 and lenticule area 20 not in one plane, ie at constant z-coordinates. The smallest radius of curvature of the lenticule area 20 is at φ = θ + π / 2, the largest, of course, on the axis θ of the cylindrical vision defect, ie at φ = θ. In a clarity correction fall differently in the representation of the 7 the vertex of flap surface 19 and lenticule area 20 together and the lenticule area 20 is more curved than the flap surface 19 , The thickness d _{L of} the lenticule results as edge thickness.

The volume to be handled as a lenticle 18 has at φ = θ = π / 2 the lowest edge thickness, since there is lenticule area 20 and flap area 19 to cut. For all other values of φ, a finite edge thickness is given if a given z-coordinate is the lower limit of the lenticule area 20 is is set.

Alternatively, in addition to the flap surface 20 and the lenticule area 19 additional edge area can be provided, which is the volume 18 in the intersection of flap surface 20 and the lenticule area 19 bordered or connects these areas where they do not converge at a given z-coordinate. The cut of this edge surface is also carried out with the pulsed laser beam. The edge surface may, for example, have a cylindrical shape, but may also have an elliptical shape (in plan view) or else a conical shape (in side view).

The formation of the volume shown in the figures 18 as through an anterior cut surface 19 at a constant distance to the corneal anterior surface 15 and a posterior cut surface 20 limited, is just a variant to limit the volume 18 , However, it has the advantage that the optical correction substantially only by a surface (the lenticule area 20 ), so that the analytical description of the other face of the interface is simply istr.

Next are optimal safety margins in terms of the distance of the volume to the anterior corneal surface 15 and corneal surface 16 offers. The residual thickness d _F between anterior cut surface 19 and corneal anterior surface 15 can be set constant to a value of for example 50 to 200 microns. In particular, it may be chosen so that the pain-sensitive epithelium remains in the lamella, which passes through the flap surface 19 under the corneal anterior surface 15 is formed. Also, the formation of the spherical flap surface is 19 in continuity with previous keratometer sections, which is advantageous for the acceptance of the method.

After creating the cut surfaces 19 and 20 then becomes the volume isolated in this way 18 from the cornea 5 away. This is schematically in 8th shown, which also illustrates that the cut surfaces 19 and 20 by acting in a focus cone 21 incident treatment laser beam are generated, for example, by juxtaposition of plasma bubbles, so that in a preferred embodiment, the flap-cut surface 19 and the lenticule cut surface 20 by suitable three-dimensional adjustment of the focus position of the pulsed laser radiation 2 be generated.

Alternatively, in a simplified embodiment, however, only the flap surface 19 through target points that the curved cut surface 19 at a constant distance from the anterior corneal surface 15 be defined by means of pulsed laser radiation and the removal of the volume 18 is done by laser ablation, for example by using an excimer laser beam. This may be the lenticule area 20 be defined as the interface of the Abtrag, even if that is not absolutely necessary. The treatment device 1 works like a well-known laser keratome, but the cut surface becomes 19 created on a curved cornea. The features described above or below are also possible in such variants, in particular as regards the determination of the boundary surface, its geometric definition and the determination of control parameters.

Produce both the lenticule area 20 as well as the flap surface 19 by means of pulsed laser radiation, it is expedient to use the lenticular surface 20 in front of the flap area 19 form, as the optical result at the lenticule area 20 better (if not reachable) is when above the lenticule area 20 no change in the cornea 5 occurred.

The removal of the volume isolated by the pulsed laser radiation 18 can, as in 8th indicated by an edge cut 22 be reached, which allows the volume 18 towards an in 8th marked arrow 23 pull it out. Alternatively, the edge trim 22 but be formed so that it has the anterior cut surface 19 ie the flap area 19 , in the form of a ring with the corneal anterior surface 15 However, the edge section does not completely rotate around an angle of 360 °. The lamella thus isolated remains in a narrow area with the remaining tissue of the cornea 5 in connection. This connecting bridge then serves as a joint around the otherwise isolated lamella of the cornea 5 fold down and thus accessible, already isolated volume 18 from the rest of the cornea 5 to be able to lose weight. The position of the connection bridge can be specified when generating the control data or the destination points. The procedure or device described implements the isolation of the volume from this point of view 19 within the cornea 5 and creating a lamella connected to the remainder of the cornea via a tissue bridge as a lid over the volume. The lid can be folded down and the volume 18 be removed.

For the production of the cut surfaces 19 and 20 The target points can now be arranged in a variety of ways. In the prior art, for example, in the WO 2005/011546 described for generating cut surfaces in the cornea that special spirals can be used, for example, run around a substantially perpendicular to the optical axis (z-axis) major axis in the manner of a helical line. Also, the use of a scan pattern is known, which arranges the target points line by line (see. WO 2005/011545 ). These possibilities can Of course, used to produce the cut surfaces defined above and become with the transformations explained below.

The adjustment of the position of the focus in the cornea is done by means of in 3 schematically shown three-dimensional deflection, which uses the displacement of lenses or other optically active elements to adjust the focus in the z direction. Now the adjustment of lenses or similar is. usually not as fast as swiveling mirrors as they are usually used in the xy scanner. Therefore, the adjustment speed of the z-scanner is usually limiting for the speed with which the cut surfaces in the cornea can be generated. For the fastest possible production of the cut surfaces 18 and 19 For this reason, in a preferred embodiment, the focus is guided in each case along a spiral-shaped path, wherein one spiral each lies in the spatially curved sectional area. During the writing of the spiral so the z-scanner is adjusted so that the arms of the spiral follow the spatially curved cut surface.

9 shows an example of a trajectory 24 as a spiral, which is formed in the illustration shown as a circular spiral. The radius of the illustrated planar spiral increases in circular coordinates with increasing angle of rotation φ, so that the following applies: r (φ) = φ · d T / (2π) (4)

In this equation, d _T denotes the distance of the spiral arms; he is in 10 shown, the enlarged section of the 9 shows. The distance of the individual spots 6 , is focused on the pulsed laser radiation and at which, for example, a plasma bubble is generated by a laser pulse, is constant in the spiral equal to d _S , so that for the angular distance Δφ of the individual spots 6 in which a laser pulse is introduced into the tissue, the following applies: Δφ = d S / r

Because, as already mentioned, the lenticule area 20 is generally not spherical, is the trajectory 24 , along which the laser focus is adjusted, an elliptical spiral, for which, of course, no constant distance of the spiral arms is given. Along the main axes a and b, however, a respective track distance d _Tb and d _Ta can be defined as 11 shows.

In 10 are the spots 6 shown to indicate the position of the focus for the individual laser pulses. In fact, after introduction of the respective laser pulse, the plasma bubbles naturally expand so far that the cut surface is generated and the trajectory 24 is then no longer visible in the cut surface.

To prepare the surgical procedure must be defined according to the definition of the cut surfaces 19 and 20 now the definition of the trajectories 24 take place, with which the cut surfaces are generated.

When determining the trajectories 24 is of course to take into account that ultimately the volume 18 should be defined in the eye in the normal state. The cut surfaces 19 and 20 , as explained so far, affect the natural eye. However, it should be noted that the treatment device 1 for reasons of fixation of the eye with a contact lens 25 works, like in 12 is shown on the corneal anterior surface 15 the cornea 5 is put on. The contact glass 25 , which is already the subject of several patent publications (for example, refer to the WO 2005/048895 A referenced), is for the present description of the treatment device 1 or the related procedures for preparing and / or performing the surgical procedure, however, only to the extent of interest, as it the anterior corneal surface 15 on the one hand gives a defined curvature and on the other the cornea 5 opposite the treatment device 1 spatially in a predefined position. With regard to the spherical curvature of the contact surface of the contact glass 25 However, the approach described here differs significantly from the approach, such as in the WO 2003/002008 A described using a planar contact lens, which flatten the cornea.

Will the eye touch the contact glass 25 pressed with spherical contact surface, there is a spatial deformation of the eye. Since the cornea is only tangentially compressible on a regular basis, ie does not change its thickness in such a pressing, the pressing of a transformation corresponds to the coordinate system of the eye, as in 13 is shown in the coordinate system of the contact lens, the in 14 is shown. This connection is known to the person skilled in the art from WO 2005/011547 A1 known, the disclosure of which should be fully incorporated in this regard. In the 13 and 14 Coordinates provided with an apostrophe indicate the coordinates of the contact lens 25 or its contact glass underside facing the eye 26 related sizes.

But the contact glass has another advantage. By pressing against the spherical contact glass bottom 26 is automatically the cornea front surface 15 spherical. At a constant distance below the anterior corneal surface 15 lying anterior cut surface 19 is attached to it also pressed spherical glass spherical, which leads to much simplified control. It is therefore completely independent of other features preferred, a contact glass 25 with spherical contact glass base 26 to use and volume through an anterior cut surface 19 and to limit a posterior cut surface, wherein for the anterior cut surface target points are / are given, the this cut surface as a spherical surface at a constant distance d _F below the cornea front surface 15 form. For the posterior cut surface, target points are defined which define a course of curvature which, with the eye relaxed, that is to say after removal of the contact glass, up to the distance d _F to the front surface of the cornea corresponds to that desired for correction of the ametropia. The same applies to the method for the definition of the target points or the surgical procedure.

The representations in the 13 and 14 show the coordinate transformation that occurs on the eye by putting on or taking off the contact glass. They contain both spherical coordinates (R, α, φ) relative to the origin of the curved surface (corneal anterior surface 15 or contact glass base 26 ) as well as cylindrical coordinates (r, z, φ) relative to the vertex of the corneal anterior surface defined by the passage point of the optical axis OA 15 or the contact glass bottom 26 ,

In the coordinate transformation of the eye-related coordinate system as shown in FIG 13 is shown in the related to the contact glass system according to 14 remain the arc length, ie α · R, the radial depth (R _CV - R) and the angle φ obtained. The transformation of the natural eye, ie in the coordinate system of 13 , underlying forms of cut surfaces 19 and 20 is thus an important step in the calculation of the drive variables for the three-dimensional focus adjustment device. It basically runs differently than with a flat contact glass, in which eg the flap surface 19 degenerate to a level. In essence, only the shape for the cut surface 20 to transform, because the cut surface 19 only at a constant distance d _F to the anterior corneal surface 15 is to train. The cut surface 19 So is in the transformed system a sphere with a relation to the contact glass bottom by d _F reduced radius of curvature R _F.

The pressing of the cornea 5 of the eye 3 to the spherically curved contact glass bottom 26 is in 15 illustrated. There, the right representation shows schematically the state when the contact glass bottom 26 only at the apex in contact with the corneal anterior surface 15 is. To clarify the geometric relationships is the cornea front surface 15 schematically in 15 drawn as a circle, although of course the spherical curvature is present only in a smaller circle section. The pressing of the contact glass 25 on the cornea 5 does that by arrow 27 symbolized transition to the state of the left side of the 15 , The removal of the contact glass 25 causes a relaxation of the eye 3 against the direction of the arrow 27

Due to the described framework conditions transform for every point in the cornea 5 the coordinates of the in 13 represented system in the system of 14 , This is now based on the choice of the control values for the focus adjustment to the effect that the cut surfaces 19 and 20 in the transformed contact glass system are to be described, since they only after removing the contact glass 26 ie, after re-transformation into the natural coordinate system of the eye, have the desired shapes. Since the application of the corneal front surface 15 is usually effected by suction by means of negative pressure, the described transformation is also referred to below as Ansaugtransformation.

For cutting the flap surface 19 , which is spherical as mentioned, is now following speed of adjustment of the z-scanner, ie the following feed speed in the z-direction set: v Z (t) = d S · f L · d T / (2π · (R F 2 - t · d S · f L · d T / Π)) ½ (5) where f _{L is} the frequency of the laser pulses of the laser radiation 2 is. Equation (5) assumes that the z-speed v _Z can be set freely and changed continuously.

If one wishes to write a sphere with a velocity v _{Z selected} from a group of discrete velocities, which is usually the case when the z-scanner is driven by a stepping motor, the time dependence of the radial function r (t) is obtained. : r (t) = [d S · f L · d T · T / π - (i S · f L · d T · T) 2 / (2π · R F ) 2 ] 1.2 (6) as well as for the angle function φ (t) = [4π · d S · f L · T / d T - (d S · f L · t 2 / R 2 ] 1.2 (7).

The t ² terms below the root of the radial as well as the angle function show that no ideal archimedean spiral is written anymore, so the orbital and spot bubble distances vary in favor of the z-rate, which can only be changed in steps.

If one wishes a constant z-feed during the focus adjustment, it does not result, as with the velocity according to equation (4), a sphere, but a paraboloid, and the following applies: z (r) = [v Z / (Ds · dr)] [r 2 · Π / f L ] (8th)

Mentioned may be in some treatment devices 1 the speed at which the z-scanner shifts the focus in the z-direction can only be adjusted within a set of discrete speeds. If one then wishes to describe a particular parabola with a given velocity v _Z , then the product d _S · d _{T must} be chosen accordingly, so that the first square bracket of equation (8) assumes the desired value. The distance of the tracks, defined by d _T , as well as the spot distance along the path described by d _S , are thus suitable to vary to write a particular parabola given v _z .

each equations (5), (6) / (7) and (8) may be used in the determination of Target points and thus de driving the focus adjustment used being, of course, then the corresponding spiral shape / surface shape is to be based. When subsequently it is said that the equations is used in the control, including in particular to understand that by means of the equations the target points are determined, which may e.g. by Evaluate the equations of function at equidistant times. The speed equations are used in a variant to To ensure that the determined target points do not cause any adjustment speeds, which are not feasible by the Fokusverstelleinrichtung.

For the above-mentioned and as described determined shapes of the surfaces 19 and 20 Now a spiral is placed in the respective area. Spiral is written by a control of the type described. The calculation of the z-speed as well as the r and φ-speed takes into account which surface shape the surface 19 respectively. 20 Has.

The lenticule area 20 is spherical if no cylinder correction is to be made. It is therefore used in accordance with equations (4) / (5) or (6) / (7) to generate this sphere. However, a sphere can be known to be approximated by a paraboloid. It is therefore provided in a variant that approximate a sphere in a manner known to those skilled in the art by means of a paraboloid and perform the control according to equation (8).

By the intake transformation according to 15 the geometry of the lenticule area changes 20 , The lenticule area 20 must in the coordinate system of the contact glass 25 the curvature of the corrected corneal anterior surface 15 * exhibit. It can not be related to a center of curvature which coincides with the center of curvature of the contact glass. The curvature defined according to equation (2) is thus converted with respect to the intake transformation.

The radius of curvature defined in equation (2) is of course a function of φ. As already mentioned and customary in ophthalmic optics, two radii of curvature r _a and r _{b can be} given: one on the axis θ of the cylindrical refractive error and one axis perpendicular to it. Computationally, it is particularly favorable to approximate the toroidal curvature that thus generally occurs by a parabola, so that the lenticule area 20 is approximated by a paraboloid. This is preferably done before the Anpreßtransformation but can also be done afterwards.

The approach is achieved by searching for each of the two radii of curvature a parabola, which passes both through the vertex of the lenticule area 20 as well as running through a point as close to the edge as possible. The corresponding relationships in the coordinate system of the eye shows 16 , This figure shows the spherical lenticule area 20 before the pressure transformation. In the figure, the sections are the toroidal lenticular surface in the generalized case 20 along the two half-axes a and b superimposed. The corresponding curves are labeled A and B, respectively, and are circular with a radius of curvature r _a and r _{b ,} respectively. On each curve, a boundary point T in cylindrical coordinates is described by the corresponding radius r and the height h, these parameters being related to the vertex S, which is identical for the two half-axis sections. The point T _a is thus characterized by the radius r _a and the height h _a . The same applies to T _b .

Now we are looking for a parabola for which h = k · r ² . The resulting parabola parameters h _a for the parabola along the large semiaxis a and k _b for the parabola along the small semiaxis b define the paraboloid, which is then written with adjustment of the focal point in the z-direction, for example by means of a constant z-feed ( compare Equation (7)) or chosen with a selection of the z-velocity from a set of discrete velocities (modification to equation (7)). In the 16 shown sections of the toriodal lenticule area 20 along the minor major axis b and the major major axis a refer to the representation in the coordinate system of the eye.

Of course, if the approximation was done by parabola equations after the pressure transform, then the transformed values will occur there. One can avoid the explicit calculation of transformed values at this point if the approximation takes place first and the parabola parameters found are subjected to the pressure transformation in the coordinate system of the contact glass, after which the in 17 present ratios shown.

The specification of the parabola parameter is in the coordinate system of the eye according to 16 as follows: k a = (z (t a ) - z (S)) / r (T a ) 2 (9) k b = (z (t b ) - z (S)) / r (T b ) 2 (10).

In equations (9) and (10), z (S) denotes the z coordinate of the point S. When the coordinate system origin is put in the vertex as in the previous figures, the z coordinate is zero. The coordinates z (T _a ) and z (T _b ) and r (T _a ) and r (T _b ) are the z and r coordinates of the corresponding point T _a and T _b in the cylindrical coordinate system.

Are the parabola parameters k _a and k _b not in the coordinate system of the eye according to 16 , but in the coordinate system of the contact glass according to 17 needed, instead of the points S, T _a and T _a then enter the 17 plotted transformed points S ', T _a ', T _b '.

Around the lenticule area 20 now in the pressed eye 3 by a (then usually elliptical) spiral with the main axes r _a 'and r _b ' represent, the spiral of a circular spiral with radius r ₀ 'by stretching in the direction of φ = θ and compression in the direction φ = θ + π / 2 constructed. Due to the simultaneous compression and extension of the average track or spot distance is maintained. If you only compress or stretch in one direction, the average distance would be changed.

The actual radii can be calculated from the radius r _{0 of} the circular spiral, which in 17 dashed line, calculated using the ellipticity as follows: e '= r a '/ R b '= (k B '/ K a ') 1.2 ,

The ellipticity e 'is the ellipticity of the transformed toriodal lenticule area 20 , The parameters k _b 'and k _a ' are given by equations (11) and (12), respectively for the transformed points S ', T _a ' and T _b '. The parabolic parameters result from the fact that here the circular spiral with the radius r ₀ , from which the lenticule area 20 is designed to be an arithmetic or geometric mean of the curvatures of the major and minor axes of the paraboloid, respectively. Because of r ₀ '= (r _a ' * r _b ') ^1/2 , one obtains for the parabola parameter k = (k _a * k _b ) ^1/2 as well as the principal axes of the ellipse: r _a ' = r ₀ '· (e ') ^1/2 and r _b ' = r ₀ '· (e') ^-1/2 .

At this point, the determination of the target points are now two trajectories 24 which are described by functional equations. The pattern of the target points is determined by evaluating the function equations.

However, it still remains to be considered that the focus of the laser beam in the focus 7 subject to focus position error. This focal position error is characteristic of the optical system, ie based on the optical implementation used. It is essentially determined by the optical design. Due to finite manufacturing accuracies within the permitted tolerance, the focus position error is moreover device-specific. It is therefore expediently determined independently for each device.

The focus position error is taken into account by a generally non-linear transformation (also referred to below as NL transformation). It is therefore not possible to carry out the NL transformation by modifying the trajectory parameters. In a preferred embodiment, the focus position error is expressed by a correction table or a correction function. It comes from a survey of the optics of the treatment device 1 , The measurement can be device-type-related or device-specific. The correction function can be obtained from an interpolation of the measurement results, for example by means of polynomials or splines. Most of the focus position error is rotationally symmetric with respect to the optical axis. It then depends only on r and z in cylindrical coordinates.

The points previously calculated using the trajectories will be in NL transformation so distorted that they after the introduction of the laser spots with the optical system, the has the focus position error, exactly at the desired location. The Application of the predistorted coordinates thus compensates for the focal position error occurring optical system.

The NL transformation is based on the idea that for every point with the coordinates (z, r) one finds a contact sphere shifted by z ₀ on which this point lies. The vertex of this sphere is then just at z ₀ (z, r) = z - z _KGL (r). The effect of the predistortion to compensate for the focus position error is in 18 illustrated. It shows the contact glass bottom 26 , which in the present example is spherical, but may also have a different shape. Due to the predistortion, it becomes a transformed contact glass sphere 26 ^ , The parameters that take into account the predistortion of the focus position error are in 18 For a transformed axis point in the cornea then z ₀ ^ = z ₀ , which takes into account the fact that the focus position error is usually rotationally symmetric, but also results in a displacement in the z direction ,

For predistortion, the calculated trajectories are converted to individual target point coordinates for the spots, which are then in the in 18 by K (r, z) symbolized correction transformation, so the NL transformation, be moved. If the focus position error is specified as function K, the coordinate of each target point must be evaluated only with the function in order to obtain the displacement or the transformed coordinate.

The result then lies for the surfaces 19 and 20 in each case a set of target point coordinates, along which the focus is guided. Due to the NL transformation and the pressing transformation, the coordinates are exactly in the desired anterior and posterior cut surfaces with respect to the natural, ie free eye 19 . 20 ,

The so obtained coordinates for the target points must still in drive signals for the three-dimensional deflection unit, e.g. the xy scanner as well as the z scanner can be implemented. For this purpose, a corresponding functional Context or a corresponding map used that for the scanner is known and has been determined in advance if necessary.

Especially for the xy scanner, in the embodiment were implemented as Galvanometer mirror, was previously the response function certainly. Applying the galvanometer mirror with a frequency sweep as well as measuring the actual Galvanometer motion provide an amplitude and phase response function. These are taken into account in the determination of the drive signals.

Furthermore, for simplified control, the scanner is not given a signal for the target to be approached for every point. Instead, the controller causes 12 A specification of support points that characterize the web of the scanner. The score is significantly reduced. This can already be usefully exploited in the case of the NL transformation in that only those target points of the transformation are subjected to the transformation for the trajectories, which are to be nodes in the control. The evaluation of the functional equations is done in one embodiment, ie by means of a time interval which is less than the time interval of the laser pulses.

It Thus, before the NL transformation, a filtering of the trajectory points is done made the mentioned Reference points, i.e. Points in a frequency of the scanner control for transformation provides. equivalent to with such a filtering is an evaluation of the functionally described trajectories at according to the scanner control spaced support points. Here comes another advantage of the function-based described here Approach to light: The decision, which points target points at are the control of the focus adjustment, must only before hit the NL transformation become. Before that you have to only the orbit parameters are converted appropriately. Also lie only then records with a multitude of points in front.

The support points thus define target points that form only a subset of the set of points to which a laser pulse is delivered. This is in 10 illustrates in which ones spots 6 that is a destination point 28 are present in the control data set, are shown as black filled circles.

This approach also has the advantage that the maximum frequency f _S , which occurs during the control of the scanner, are much lower than the laser pulse frequency f _p . For example, it is possible to work with a drive frequency of 20 kHz and a laser pulse frequency of 200 kHz. The result is thus between the target points 28 , which are given when controlling the scanner, one or more spots 6 to which pulsed laser radiation is also emitted.

Thus, not only is pulsed laser radiation delivered while the scanners are in an adjustment process, for example while the galvanometer mirrors are moving, but laser pulses are deflected by the scanners as they move from one given target point to the next. In order to achieve the highest possible deflection speed, this movement represents a vibration which, in the case of perfect circular spirals (as in the case of the anterior cutting surface 19 occur) even a purely sinusoidal oscillation is. As with the lenticule area 20 If the actual spiral shape differs only slightly from ideal circular or elliptical spirals, the scanners can be operated near their cut-off frequency so that the described paths along which the spots are located allow for very fast cut-surface generation.

After determining the control data sets containing the target points from the described point quantities obtained for the trajectories, the pre-process is completed, which was carried out to provide the corresponding control value or parameters. For this pre-trial is not a human involvement and in particular the involvement of a doctor or surgeon conducive. The procedure is carried out by the control unit 12 performed without the activity of a medical professional. Its presence is required only for the subsequent surgical procedure.

The procedure of the procedure for the preparation of the device 1 The use in an ocular surgical ametropia surgery is schematically illustrated in FIG 19 summarized. In a step S1, the measurement of the eye takes place 3 , It will be for the patient 4 present defective vision correction parameters, as are common for example for conventional glasses. The parameters established in step S2 are then used in a step S3 for the correction of the new curvature of the cornea 5 to determine. If this calculation is completed in step S3, the volume is determined in S4, which must be removed from the cornea. This is usually done by determining the lenticule area 20 as well as the flap area 19 in a step S5. Having obtained the corresponding functional descriptions of these surfaces, in step S6, the suction transformation, which affects the contact glass when the eye is sucked in, is taken into account.

When next the coordinates of the trajectories are determined from which the cut surfaces are built become. This is indicated schematically in step S7 by the parameters r, φ, z. At the end of step S7 there is a dot pattern with the coordinates the spots on which a laser radiation pulse is to act. The concentration the destination points can already simplify the computational Expenditure can be reduced by not being exposed to any laser radiation Spot a support point when controlling the scanner is specified.

following the coordinate quantity thus obtained is taken into consideration in step S8 the focus position error again transformed. In a step S11 then the actual drive parameters are determined, wherein a response function is received, in a step S10 from a previous measurement (Step S9) of the amplitude and frequency behavior of the scanners was obtained.

With the drive parameters determined in this way is then in step S12 the actual surgery performed, at which now preferably between the individual support points, which underlie the control of the scanner, additional Spots are exposed to laser radiation pulses.

Claims (15)

Treatment device for operative correction of the refractive error of an eye ( 3 ) of a patient ( 4 ), one of a control device ( 12 ) controlled laser device (L), which for the isolation of one in the cornea ( 5 ) ( 18 ) by irradiation of laser radiation ( 2 ) Corneal tissue, whereby the control device (P, 12 ) by specifying in the cornea ( 5 ) ( 28 ) the laser device (L) for focusing the laser radiation ( 2 ) in the cornea ( 5 ), characterized in that the control device (P, 12 ) when specifying the target points ( 28 ) Focus position errors that occur when focusing the laser radiation ( 2 ) to a deviation between the given and the actual position of the target points ( 28 ), by one of the position of the respective target point ( 28 ) dependent derivative (K) and thus compensates for the focus position error. Treatment device according to claim 1, characterized in that the control device (P, 12 ) for determining the proviso on a correction table or function (K), the focus position error depending on the position of the respective target point ( 28 ) indicates. Treatment device according to claim 2, characterized in that each lead parallel to the optical axis (OA) is a displacement of the respective target point (OA). 28 ) and the correction table or function (K), in cylindrical coordinates (r, φ, z) depends only on the axial and radial coordinates (r, z). Treatment device according to one of the above claims, characterized in that the control device (P, 12 ) a train ( 24 ), along which the focus ( 7 ) of the laser radiation is to be adjusted, on the web ( 24 ) points ( 6 ) as target points ( 28 ) and then corrects them with the allowance for the focus position error. Treatment device according to claim 4, characterized in that the control device (P, 12 ) the train ( 24 ) by one or more functional equations and those on the track ( 24 ) points ( 6 ) by evaluating the one or more functional equations (s) as target points ( 28 ), and thus the destination points ( 28 ) determined as control data. Treatment device according to claim 4 or 5, characterized in that the control device (P, 12 ) in determining the path ( 24 ) or the destination points ( 28 ) a deformation of the cornea ( 5 ) of the eye ( 3 ), which during the irradiation of the pulsed laser radiation ( 2 ) occurs, in particular by a contact glass ( 25 ). Treatment device according to claim 6, characterized in that the control device (P, 12 ) first a train ( 24 ), which is related to the undeformed eye, and then to compensate for the deformation of the cornea ( 5 ) of the eye ( 3 ) modified. Method for generating control data for a laser device (L) of a treatment device ( 1 ) for operative vision correction of an eye ( 3 ) of a patient ( 4 ), which are used to isolate one in the cornea ( 5 ) ( 18 ) by irradiating focused laser radiation ( 2 ) Separates corneal tissue, wherein the control data in the operation of the treatment device ( 1 ) of the laser device (L) target points ( 28 ) for the focused laser radiation ( 2 ) in the cornea ( 5 ), characterized in that when determining the target points ( 28 ) Focus position errors that occur when focusing the laser radiation ( 2 ) to a deviation between the given and the actual position of the target points ( 28 ), by one of the position of the respective target point ( 28 ) dependent derivative (K) and thus the focus position errors are compensated. Method for the operative correction of defective vision of an eye ( 3 ) of a patient ( 4 ), where one volume ( 18 ) in the cornea ( 5 ) is isolated and to the separation of corneal tissue laser radiation ( 2 ) in a pattern in the cornea ( 5 ) target points ( 28 ), characterized in that when specifying the target points ( 28 ) Focus position errors that occur when focusing the laser radiation ( 2 ) to a deviation between the given and the actual position of the target points ( 28 ), by one of the position of the respective target point ( 28 ) dependent derivative (K) and thus the focus position errors are compensated. Method according to one of the above method claims, characterized in that a correction table or function (K) is used to determine the lead, which determines the focus position error as a function of the position of the respective target point ( 28 ) indicates. Method according to one of the above method claims, characterized in that each lead parallel to the optical axis (OA) has a displacement of the respective target point (OA). 28 ) and the correction table or function (K), in cylindrical coordinates (r, φ, z) depends only on the axial and radial coordinates (r, z). Method according to one of the above method claims, characterized in that a web ( 24 ), along which the focus ( 7 ) of the laser radiation is to be adjusted, on the web ( 24 ) points ( 6 ) as target points ( 28 ) and then corrected with the allowance for the focus position error. Method according to claim 12, characterized in that the web ( 24 ) is determined by one or more functional equations (s) and those on the track ( 24 ) points ( 6 ) by evaluating the one or more functional equations (s) as target points ( 28 ), and thus the target points ( 28 ) are determined as control data. Method according to claim 13, characterized in that in determining the path ( 24 ) or the destination points ( 28 ) a deformation of the cornea ( 5 ) of the eye ( 3 ), which during the irradiation of the pulsed laser radiation ( 2 ) occurs, in particular by a contact glass ( 25 ). Method according to claim 14, characterized in that first a web ( 24 ), which is related to the undeformed eye, and then to compensate for the deformation of the cornea ( 5 ) of the eye ( 3 ) is modified.