DE102006053118B4 - Planning device for preparing control data for a treatment device for surgical correction of ametropia, treatment device for surgical correction of ametropia and method for preparing control data therefor - Google Patents

Abstract

Planning device for determining control data for a treatment device (1) for the surgical correction of ametropia in an eye (3) of a patient (4), wherein - the planning device (P) generates the control data for a treatment device (1) which has a contact lens (25) for Placement on the eye (3) and a laser device (L), which separates corneal tissue by irradiating pulsed fs laser radiation (2), the laser radiation (2) passing through the attached contact lens (25) in a pattern within the cornea (5) lying target points (28) is focused, and wherein the planning device (P) has an interface (S) for supplying measurement data on parameters of the eye (3) and ametropia data on the ametropia to be corrected in the eye (3), wherein the ametropia data include the refractive power BBReiner for the glasses (17) suitable for correcting the ametropia, and the distance dHS at which the glasses (17) with the refractive power BB R must lie in front of the apex of the cornea in order to achieve the desired correction of the ametropia by means of the glasses (17), - a volume (18) is defined from supplied measurement and ametropia data, which lies within the cornea (5) and its distance from the cornea (5) causes the desired correction of the ametropia, - defines a boundary surface (19, 20) which delimits the defined volume (18) within the cornea (5), and - generates a control data record for this boundary surface (19, 20) for controlling the laser device (L). , which defines a three-dimensional pattern of the target points (28) in the cornea (5), which lie in the interface (19, 20) in order to separate the corneal tissue in the interface (19, 20).

Description

The invention relates to a planning device for determining control data for a treatment device for the surgical correction of ametropia in a patient's eye, the planning device generating the control data for a treatment device which has a laser device which separates corneal tissue by irradiating pulsed laser radiation, the laser radiation is focused on target points lying in a pattern in the cornea,

The invention further relates to a treatment device for the surgical correction of ametropia in a patient's eye, which has an interface for supplying measurement data on parameters of the eye and ametropia data on the ametropia to be corrected, a laser device that separates corneal tissue by irradiating pulsed laser radiation , whereby the laser radiation is focused on target points lying in a pattern in the cornea.

The invention further relates to a method for preparing control data for a treatment device for the surgical correction of ametropia in a patient's eye, which has a laser device which separates corneal tissue by irradiating pulsed laser radiation, the laser device during operation emitting laser radiation according to the control data to in focuses on target points lying in a pattern in the cornea.

Glasses have been the classic way of correcting ametropia in the human eye for a long time. In the meantime, however, refractive surgery is increasingly being used, which corrects ametropia through changes in the cornea. The aim of all surgical methods is to change the cornea in a targeted manner in order to influence the refraction of light. Various surgical methods are known for this. The most widespread is the so-called laser in-situ keratomileusis, which is also abbreviated to LASIK. First, a corneal flap is detached from the corneal surface on one side and folded to the side. This lamella can be loosened by means of a mechanical microkeratome, or also by means of a so-called laser keratome, such as that sold by Intralase Corp., Irvine, USA.

The latter uses laser radiation to create a cut surface in the cornea. Several processes, which are initiated by the laser radiation, take place in the tissue one after the other. If the power density of the radiation is above a threshold value, an optical breakthrough occurs, which creates a plasma bubble in the cornea. After the optical breakthrough occurs, the plasma bubble grows due to expanding gases. If the optical breakthrough is not maintained, the gas generated in the plasma bubble is absorbed by the surrounding material and the bubble disappears again. Trade-separating effects are also possible that work without a plasma bubble. For the sake of simplicity, all such processes are summarized here under the term "optical breakthrough", i.e. this term should not only include the optical breakthrough but also the resulting effects in the cornea.

To generate the optical breakthrough, the laser radiation is applied in a pulsed manner, with the pulse length being less than 1 ps. As a result, the power density required to trigger an optical breakthrough for the respective pulse is only achieved in a narrow spatial area. the U.S. 5,984,916A shows clearly that the spatial range of the optical breakdown (in this case the generated interaction) depends strongly on the pulse duration. A high focus of the laser beam in combination with the short pulses mentioned allows the optical breakthrough to be used with pinpoint accuracy in the cornea.

To create the thin lamella, the laser keratome is now used to create a series of optical breakthroughs at predetermined points in such a way that a cut surface is formed which detaches the lamella from the underlying cornea.

After the lamella has been loosened and folded to the side, the LASIK operation involves the use of an excimer laser, which ablates the exposed corneal tissue. After the volume in the cornea has been vaporized in this way, the corneal flap is folded back into its original position. The LASIK method already in use, which is also known as fs-LASIK if a laser keratome is used, exposes a cover-shaped corneal flap, folds it down and ablates the exposed tissue with an ablation laser.

the EP 1 719 483 A1 relates to a method for controlling a laser for the ablation of a corneal layer of an eye.

It is also mentioned in the prior art that the correction of the ametropia is produced in that a lens-shaped partial volume in the corneal tissue is isolated by means of the pulsed laser radiation. A corresponding description can be found, for example, in WO 2005/011545 A1 or U.S. 2004/0 243 112 A1 . Corresponding devices are not yet available on the market.

With the LASIK method, the corneal tissue exposed by means of a keratome is ablated using an ablation laser in such a way that the desired volume is removed. The laser beam is focused at different points on the exposed cornea in order to remove the material. The removal of material in the cornea is adjusted by a so-called shot file, which defines the number of ablation laser radiation pulses and their respective coordinates at which the pulses are delivered. The shot file is generated in the devices after the eye has been measured. Due to the different working principle, it cannot be used for the surgical procedures and devices that are currently being scientifically examined, in which a volume in the cornea is isolated.

The invention is therefore based on the object of specifying a planning device, a device and a method of the type mentioned at the outset, so that an operative correction of ametropia can be carried out simply by isolating a volume located in the cornea using laser radiation.

The invention is defined in the independent claims.

A planning device of the type mentioned at the outset is provided which, from supplied measurement and ametropia data, defines a volume which lies within the cornea and the removal of which from the cornea brings about the desired correction of the ametropia, establishes a boundary surface which delimits the defined volume within the cornea, and a control data record for controlling the laser device is generated for this interface, which sets a three-dimensional pattern of the target points in the cornea, which lie in the interface and are arranged in such a way that the interface is formed as a cut surface after irradiation with the pulsed laser radiation according to the control data record, which isolates the defined volume in the cornea and makes it removable.

There is also a treatment device for the surgical correction of ametropia in a patient's eye, which has an interface for supplying measurement data on parameters of the eye and ametropia data on the ametropia to be corrected, a laser device which separates corneal tissue by irradiating pulsed laser radiation, the Laser radiation is focused on target points located in a pattern in the cornea, and has a planning device of the type described in the previous paragraph.

A method of the type mentioned at the outset is also provided, which has the following steps: determining measurement data on parameters of the eye and ametropia data on the ametropia of the eye to be corrected, defining a volume from the measurement data and the ametropia data, the volume lying within the cornea and wherein the removal of the volume from the cornea provided for after operation of the treatment device results in the desired correction of the ametropia, definition of an interface that delimits the defined volume within the cornea, and definition of a three-dimensional pattern of target points in the cornea, the target points in the Lie interface and are arranged so that the interface is formed according to the control data as a cut surface upon irradiation of the pulsed laser radiation, which isolates the defined volume in the cornea and thus makes it removable, generating a control data set containing the three-dimensional pattern for controlling the laser device.

Based on measurement and ametropia data of the eye to be corrected, a volume is first defined that lies within the cornea and the removal of which brings about the desired ametropia correction. The removal can take place, for example, via a cut to the corneal surface that makes the volume accessible, the generation of which is also effected by the planning device or the control data. In order for the correction to be as equal as possible for day and night vision, the volume should cover the pupil of the dark-adapted eye as far as possible. Boundary surfaces are then defined for this volume, which delimit the volume. The boundary surfaces are later formed as cut surfaces with the treatment device or its laser device in order to be able to remove the volume, for example to be able to remove it. A control data record is determined for the boundary surfaces, which specifies target points lying in the boundary surface, at each of which an optical breakthrough is to be produced by means of the laser radiation in order to form the cut surface. The target points are a three-dimensional pattern and all lie within the previously defined interface. The planning device can also be part of the laser device.

As a result of the method or the activity of the planning device, there is a control data record that enables automatic activation of the laser device, so that the generation of the cut surfaces that isolate the volume in the cornea can then take place automatically. The planning device or the one equipped with it Treatment device for the surgical correction of ametropia and the method for providing control data for a treatment device preferably generates the control data set automatically from the measurement data and ametropia data provided. In advantageous configurations, the operator does not need to be involved.

The planning device can be embodied as a computer that works under the control of a program. Optionally, the planning device can be part of the treatment device. A corresponding computer program product with program code, which causes the mentioned method steps, is therefore also a solution to the mentioned task.

The generation of the control data record is based on determined measurement data and ametropia data of the eye. This measurement data can be recorded on an independent measurement device. However, the treatment device is expediently connected directly to the measuring device. For example, an autorefractor, a refractometer, a keratometer, an aberrometer, an OCT or a wavefront measuring device or any combination of such devices or measuring devices can be used as the measuring device.

The refractive error can include hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism in which there is hyperopia in one direction and myopia in a direction perpendicular thereto), aspheric errors, and higher-order aberrations.

A direct connection of the measuring device to the planning device or the treatment device equipped with it with regard to data transmission, which can be used in one variant, has the advantage that the use of incorrect measurement and ametropia data is ruled out with the greatest possible security. This applies in particular if the patient is transferred from the measuring device or the measuring devices to the laser device by means of a positioning device which interacts with the measuring device or the laser device in such a way that the respective devices recognize whether the patient is in the respective position for measurement or introduction of the laser radiation. When the patient is moved from the measuring device to the laser device, the measurement and ametropia data can also be transmitted to the treatment device at the same time.

It is ensured that the planning device always generates the control data record that belongs to the patient, and erroneous use of an incorrect control data record for a patient is virtually impossible.

Another possible embodiment of the invention also takes this aspect into account, according to which the control data record is transmitted to the treatment device and, more preferably, operation of the laser device is blocked until a valid control data record is present at the laser device. In principle, a valid control data set can be a control data set that is suitable for use with the laser device of the treatment device. In addition, the validity can also be linked to the fact that further checks are carried out, for example whether additional information about the patient stored in the control data record, for example a patient identification number, corresponds to other information that was entered separately on the treatment device, for example, as soon as the patient is in the correct position for the operation of the laser device. The transmission can take place using memory chips (e.g. via USB or memory stick), magnetic storage devices (e.g. floppy disks), by radio (e.g. WLAn, UMTS, Bluetooth) or by wire (e.g. USB, Firewire, RS232, CAN bus, Ethernet etc.).

To generate the isolated volume, the focus of the focused, pulsed laser radiation is regularly shifted in three dimensions. Therefore, as a rule, a two-dimensional deflection of the laser radiation, for example using a scanning mirror, is combined with a simultaneous focus adjustment in the third spatial direction, for example using a telescope. The setting of the position of the focus is, of course, decisive for the accuracy with which the cut surface isolating the volume can be generated. A contact glass is placed on the eye to fix it. Such a contact glass is also common in the laser keratomes mentioned at the outset, which are used in the fs-LASIK method. The contact glass regularly also has the function of giving the front surface of the cornea a known shape. In the case of the laser keratomes known to date, this shape is a plane, ie the eye is flattened in the region of the cornea for the operation of the laser keratome. Since this is relatively uncomfortable for the patient, a curved contact lens is used. Such a contact lens then gives the front surface of the cornea a known curvature. The curvature results in a deformation of the cornea. This deformation is greater, the more the curvature of the contact surface of the contact lens facing the eye deviates from the actual curvature of the cornea of the patient's eye. In order to be able to work with a uniform contact glass curvature as far as possible, it is therefore advantageous liable to take into account the corneal deformation that occurs when using a curved contact lens in the control data set, so that the desired boundary surface for the defined volume in the free eye, ie not deformed by the contact lens, is present regardless of the degree of deformation. It is therefore preferable that such a deformation of the cornea of the eye that occurs during irradiation of the pulsed laser radiation, in particular through the mentioned contact lens, is taken into account when generating the control data set that contains the pattern of the target points.

This approach not only makes it possible to use a contact lens curvature that is as uniform as possible, but also achieves a higher quality of the ametropia correction. In the case of the known laser keratomes, such a consideration of the deformation is not necessary, since the eye is pressed flat against the cornea by the contact glass. The lamella required for the LASIK operation is produced there by simply producing optical breakthroughs in a plane parallel to the contact glass.

The generated control data record can be used directly to control the treatment device. However, it is expedient to give the doctor treating you the opportunity to intervene so that on the one hand he can check the control data record and on the other hand he can take special cases or special requests into account. A possible special request is, for example, the position of the incision through which the isolated volume is to be removed from the cornea. Ophthalmologists often have different opinions here. But it can also be desirable for the doctor to be able to intervene for reasons of liability law. It is therefore expedient for the device as a possible configuration that the planning device has a display device for the visual representation of control data of the control data record and an input device for subsequent changing or influencing of the control data record.

Optical systems are usually not perfect. Of course, this also applies to focusing the laser radiation in the cornea. Here, for example, an image field curvature can occur, which has the result that focal positions supposedly positioned in one plane are actually not in one plane at all, but in a curved surface. In the case of the known laser keratomes, this aspect plays no role, since the production of the cut that exposes the lamella has no effect on the optical quality of the correction. The actual correction is solely determined by the volume of the exposed cornea vaporized with the ablation laser. An error correction, for example with regard to an image field curvature, is therefore of no interest in the prior art, in particular with regard to laser keratomes.

Since the volume to be removed is defined entirely by the focusing of the pulsed laser radiation, it is expedient for the planning device to generate the control data set to compensate for optical focal position errors, which lead to a deviation between the specified and actual position of the target points when the pulsed laser radiation is focused, by a dependent on the position of the respective target point is taken into account and thus compensated. This lead can be determined, for example, by the planning device accessing a correction table or function that specifies the focal position error as a function of the position of the respective target point. The correction table or correction function can be prescribed uniformly for the respective device type, or, which is preferred for reasons of precision, can be determined individually for the respective device.

The same applies to the method in which optical focal position errors, which lead to a deviation between the specified and actual position of the target points when focusing the pulsed laser radiation, are now used to determine the boundary surface or the three-dimensional pattern of the target points, by a position-dependent point Reserve can be taken into account and thus compensated.

The interface isolates the volume if it is formed as a cut surface after the application of the pulsed laser radiation. The interface thus automatically has anterior and posterior sections, the terms “anterior” and “posterior” here corresponding to the usual medical nomenclature. In principle, it is possible to design the interface as an open space. However, the generation of the control data set is simplified if the boundary surface is composed of an anterior partial surface and a posterior partial surface. One of the sub-areas can then be formed at a constant distance from the surface of the cornea. The other is then inevitably not at a constant distance from the front surface of the cornea. The partial surface lying at a constant distance from the anterior surface of the cornea, usually the anterior partial surface, is therefore generally spherical. This applies in any case when the cornea is pressed onto a spherical contact glass. The optical correction then takes place through the shape of the other partial surface, usually the posterior partial surface. This considerably simplifies the computational effort.

The procedure according to the invention for specifying the ametropia data consists of determining the refractive power B _BR of spectacles suitable for ametropia correction, which must be at a distance d _HS in front of the corneal vertex in order to achieve the desired ametropia correction. A determination of these parameters is a common standard in ophthalmic optics and enables the use of widespread and long-established measuring devices. In order to generate the control data record, only the ametropia data for a conventional spectacle correction is then used. Of course, such data can also contain astigmatism corrections. A typical formula for the refractive power B _BR of a pair of glasses is, for example, equation (1) given in the following description of the figures. It specifies the spherical refractive error Sph and the cylindrical refractive error Cyl and of course requires knowledge of the cylinder axis 0 for the latter.

To correct the ametropia, a volume is removed from the cornea with the treatment device or using the control data records generated in the method. The ultimate goal is to change the curvature of the cornea in such a way that the ametropia is corrected. A particularly direct, exact and simple calculation of the curvature of the front surface of the cornea to be achieved for the correction is obtained with the following equation: $${\text{R}}_{\text{CV}}*=1/\left(\left(1/{\text{R}}_{\text{CV}}\right)+{\text{B}}_{\text{BR}}/\left(\left({\text{n}}_{\text{c}}-1\right)\left(1-{\text{i.e}}_{\text{HS}}·{\text{B}}_{\text{BR}}\right)\right)\right)+\text{f}.$$

wobei dc bzw. d_C* die Dicke der Hornhaut bzw. nach Entfernung des Volumens bezeichnet. Der Radius R_CV* wird dann iterativ berechnet, indem bei jedem Iterationsschritt aus der Differenz (R_CV* - Rcv) auf die Größe (d_C* - de) geschlossen wird und das entsprechende daraus erhaltene Ergebnis für die Dickenänderung bei der Berechnung von R_CV* im nächsten Iterationsschritt angewendet wird. Die iterative Berechnung kann beispielsweise abgebrochen werden, wenn zwischen zwei Iterationsschritten für F nur noch ein Unterschied besteht, der kleiner als ein Grenzwert ist.In this equation, R _CV * is the radius of curvature of the anterior corneal surface after volume removal, Rcv is the corneal radius of curvature before volume removal (it is included in the measurement data), n _c is the refractive power of the corneal material (usually about 1.376), i _HS the distance at which glasses with the mentioned refractive power must be in front of the corneal vertex and F a factor that is a measure of the optical effect of the decrease in thickness of the cornea on the visual axis due to the distance of the volume. For a simplified calculation, the factor F can be set equal to zero. If you want a more precise calculation, F can be calculated as follows: $$\text{f}=\left(1-1/{\text{n}}_{\text{c}}\right)·\left({\text{i.e}}_{\text{C}}*-{\text{i.e}}_{\text{C}}\right),$$

where dc or d _C * denotes the thickness of the cornea or after removal of the volume. The radius R _CV * is then iteratively calculated by inferring the size (d _C * - de) from the difference (R _CV * - Rcv) in each iteration step and the resulting result for the change in thickness when calculating R _CV * is applied in the next iteration step. For example, the iterative calculation can be aborted if there is only a difference between two iteration steps for F that is smaller than a limit value.

The method or the treatment device with the planning device works particularly easily if, as mentioned, the optical correction to be effected by the removal of the volume is primarily caused by the curvature of a partial surface that is not at a constant distance from the front surface of the cornea and that delimits the volume , is formed. The posterior partial surface is expediently chosen for this purpose, since this partial surface then has the above-mentioned radius of curvature reduced by the constant distance between the anterior partial surface and the front surface of the cornea.

The control data record provides a file that enables a fully automatic sequence of the surgical intervention with regard to the control of the treatment device or a corresponding operation of the treatment device. For this purpose, the control data record specifies the target points for the laser device, to which the focused laser beam must be directed in order to emit laser pulses. The focus of the focused laser radiation is then adjusted in such a way that it runs in a trajectory over the specified target points. In terms of calculation technology or with regard to the adjustment speed, it is particularly favorable if the trajectory is in the form of a spiral. In the case of the anterior or posterior sub-area mentioned, a spiral is then specified for each sub-area. The course of the focus along a spiral enables the corresponding deflection device of the treatment device to be operated close to the cut-off frequency, since, for example, when writing a spiral, two galvanometer scanners can each be operated close to or at their cut-off frequency.

Basically, when defining the path, it must be ensured that the laser pulses are emitted on this path. The target points then define interpolation points in the path. The density with which the target points specify the path can, but does not necessarily have to, correspond to the density with which the points are arranged on the path onto which a pulse of the laser radiation is emitted. On the contrary, it is even preferable that the target points represent only a subset of those points onto which laser pulses are emitted. On the one hand, the amount of data in the control data record is then drastically reduced, and on the other hand, the computing effort is simplified in all those steps in which a functional description of the trajectory in the interface should not or cannot be used, but in which the target points are processed individually have to. An example of this is the aforementioned correction for field curvature.

It is therefore preferred for the device that the laser device displaces the focused laser radiation along a trajectory across the pattern of target points, with pulses of the pulsed laser radiation being emitted into the cornea at points lying on the trajectory between the target points.

The same applies to the method, namely that the control data set is provided for a laser device, which adjusts the focused laser radiation along a path across the pattern of target points, with the control data set being generated in such a way that the target points in the pattern represent a subset of the points on which the laser device emits the pulsed laser radiation. The control data record is thus matched to the possible adjustment speed of the laser device.

As a result, in the laser device for adjusting the focus position, a different frequency of the reference points is specified or used than that which occurs when the laser pulses are generated. Of course, the control data set does not contain any information about the frequency per se, even if this is possible. Due to the maximum adjustment speed or the highest signal frequencies that are used when adjusting the focus of the laser radiation, the specification of the target points naturally corresponds to a path speed or an adjustment speed in the respective coordinates used for the description. The spatial distance of the target point in combination with the web speed and the laser pulse frequency, which can be realized by the laser device, now leads in the preferred embodiment to the fact that laser pulses are also automatically emitted at times at which the adjustment of the focus from one target point to the next he follows. This approach has the advantage that during operation of the treatment device the target points are/are specified with a frequency that is lower than the frequency with which the pulses of the pulsed laser radiation are/are emitted from the laser device into the cornea.

Of course, the specification of target points in the control data set does not mean that an adjustment speed of zero must be present at these target points when the laser pulse is emitted at the target point. In order to quickly generate the cut surface at the specified boundary surface of the defined volume, it is advantageous if the synchronization of the adjustment of the focus position and the emission of the laser pulses is achieved in such a way that a laser pulse is emitted with continuous deflection of the focus and still at the target point in the cornea meets. The pulsed laser radiation is therefore applied with continuous adjustment of the focus position, e.g. with moving scanning mirrors. This configuration causes a systematic difference compared to known shot files for ablation lasers, in which a shot of the ablation laser is only fired when the deflection of the laser beam is aimed at a specific point.

• 1 eine Schemadarstellung einer Behandlungsvorrichtung bzw. eines Behandlungsgerätes zur Fehlsichtigkeitskorrektur,
• 1a eine Schemadarstellung hinsichtlich des Aufbaus des Behandlungsgerätes der 1,
• 2 eine Prinzipdarstellung zur Einbringung gepulster Laserstrahlung in das Auge bei der Fehlsichtigkeitskorrektur mit dem Behandlungsgerät der 1,
• 3 eine weitere Schemadarstellung des Behandlungsgerätes der 1,
• 4 in Teilfiguren (a), (b) und (c) schematische Schnittdarstellungen zur Verdeutlichung des Korrekturbedarfes am menschlichen Auge bei Fehlsichtigkeit,
• 5 eine schematische Schnittdarstellung durch die Augenhornhaut mit Darstellung eines zur Fehlsichtigkeitskorrektur zu entfernenden Volumens,
• 6 ein Schnitt durch die Augenhornhaut nach Entfernung des Volumens der 5,
• 7 eine Schnittdarstellung ähnlich der 5,
• 8 eine schematische Schnittdarstellung durch die Augenhornhaut zur Veranschaulichung der Volumenentnahme,
• 9 eine Draufsicht auf eine spiralförmige Bahnkurve, die zur Isolierung des Volumens der 5, 7 und 8 verwendet wird,
• 10 eine vergrößerte Darstellung der Bahnkurve der 9,
• 11 eine alternative Bahnkurve für die Korrektur auch zylindrischer Fehlsichtigkeiten,
• 12 eine schematische Darstellung zur Erläuterung der Funktion eines Kontaktglases im Behandlungsgerät der 1,
• 13 bis 15 schematische Darstellungen hinsichtlich der Wirkungen des Kontaktglases durch Verformung der Augenhornhaut,
• 16 und 17 Schemadarstellung hinsichtlich der Approximation der das Volumen posterior begrenzenden Fläche im Falle auch zylindrischer Fehldichtigkeitskorrekturen,
• 18 eine schematische Darstellung zu einer bei der Ermittlung von Steuerdaten für das Behandlungsgerät der 1 verwendeten Bildfeldkrümmungskorrektur und
• 19 eine schematische Darstellung des Ablaufes bei der Vorbereitung und Durchführung einer Fehlsichtigkeitskorrektur.

The invention is explained in more detail below by way of example with reference to the drawing. 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 1 ,
• 2 a schematic diagram for introducing pulsed laser radiation into the eye when correcting ametropia with the treatment device 1 ,
• 3 another schematic representation of the treatment device 1 ,
• 4 in partial figures (a), (b) and (c) schematic sectional representations to clarify the need for correction of the human eye in the case of ametropia,
• 5 a schematic sectional view through the cornea showing a volume to be removed to correct ametropia,
• 6 a section through the cornea after removal of the volume of 5 ,
• 7 a sectional view similar to that 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 the 5 , 7 and 8th is used,
• 10 an enlarged representation of the trajectory of the 9 ,
• 11 an alternative trajectory for the correction of cylindrical ametropia,
• 12 a schematic representation to explain the function of a contact lens in the treatment device 1 ,
• 13 until 15 schematic representations of the effects of the contact glass due to deformation of the cornea,
• 16 and 17 Schematic representation with regard to the approximation of the surface delimiting the posterior volume in the case of cylindrical corrections of incorrect sealing,
• 18 a schematic representation of a in the determination of control data for the treatment device 1 used field curvature correction and
• 19 a schematic representation of the process involved in preparing and carrying out a correction of ametropia.

1 shows a treatment device 1 for an ophthalmic surgical procedure that corresponds to that in FIG EP 1159986 A1 or the U.S. 5,549,632 A described. The treatment device 1 uses treatment laser radiation 2 to correct an ametropia in an eye 3 of a patient 4. The ametropia can be hyperopia, myopia, presbyopia, astigmatism, mixed astigmatism (astigmatism in which hyperopia is in one direction and myopia in a direction perpendicular thereto present), aspheric errors and higher order aberrations. In the embodiment described, the treatment laser radiation 2 is applied as a pulsed laser beam focused into the eye 3 . The pulse duration is in the femtosecond range, for example, and the laser radiation 2 acts in the cornea by means of non-linear optical effects. 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. In the exemplary embodiment described, the components of the device 1 are controlled by an integrated control unit, which of course can also be designed independently.

Before the treatment device is used, the ametropia of the eye 3 is measured with one or more measuring devices.

1a FIG. 1 shows the treatment device 1 schematically. In this variant, it has at least two devices or modules. A laser device L emits the laser beam 2 onto the eye 3 . The operation of the laser device L is fully automatic, ie the laser device L starts the deflection of the laser beam 2 in response to a corresponding start signal and thereby produces cut surfaces which are constructed in a manner yet to be described and isolate a volume in the cornea. The laser device L receives the control data required for operation beforehand from a planning device P as a control data record via control lines that are not specified in more detail. The transmission takes place before the laser device L is operated. Of course, communication can also be wireless. As an alternative to direct communication, it is also possible to arrange the planning unit P spatially separate from the laser unit L and to provide a corresponding data transmission channel.

Preferably, the control data record is transmitted to the treatment device 1 and, more preferably, operation of the laser device L is blocked until the laser device L has a valid control data record. 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, the validity can also be linked to the fact that further tests are passed, for example whether information about the treatment device 1, e.g. B. a device serial number, or the patient, z. B. a patient identification number, with other information that has been read out for example on 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, which is made available to the laser unit L to carry out the operation, from measurement data and ametropia data that were determined for the eye to be treated. They are fed to the planning unit P via an interface S and, in the exemplary embodiment shown, come from a measuring device M that measured the eye of the patient 4 beforehand. Of course, the measuring device M can transmit the corresponding measurement data and ametropia data to the planning device P in any desired manner.

Transmission can take place using memory chips (e.g. via USB or memory stick), magnetic storage devices (e.g. floppy disks), by radio (e.g. WLAN, UMTS, Bluetooth) or by wire (e.g. USB, Firewire, RS232, CAN bus, Ethernet etc.). The same applies, of course, with regard to the data transmission between the planning device P and the laser device L.

A direct radio or wire connection of the measuring device M to the treatment device 1 with regard to data transmission, which can be used in one variant, has the advantage that the use of incorrect measurement and ametropia data is ruled out with the greatest possible security. This applies in particular if the patient is transferred from the measuring device M or the measuring devices to the laser device L by means of a positioning device (not shown in the figure), which interacts with the measuring device M or the laser device L in such a way that the respective devices recognize whether the patient 4 is in the respective position for measuring or introducing the laser radiation 2 is When the patient 4 is moved from the measuring device M to the laser device L, the measurement and ametropia data can also be transmitted to the treatment device 1 at the same time.

Suitable means are preferably used to ensure that the planning device P always generates the control data set associated with the patient 4, and erroneous use of an incorrect control data set for a patient 4 is virtually impossible.

The mode of action of the laser beam 2 is in 2 indicated schematically. The treatment laser beam 2 is focused into the cornea 5 of the eye 6 by means of optics, which are not designated in any more detail. This creates a focus in the cornea 5 which 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 produce an optical breakthrough in the cornea 5 at the respective spot 6, which in turn causes an in 2 schematically indicated plasma bubble initiated. As a result, this laser pulse is separated in the cornea 5 tissue. When a plasma bubble develops, the tissue layer separation covers a larger area than the spot 6, which the focus of the laser radiation 2 covers, although the conditions for generating the breakthrough are only achieved in the focus. In order for each laser pulse to produce an optical breakthrough, 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, for example, from DE 69500997 T2 famous.

Alternatively, a tissue-separating effect can also be produced by the pulsed laser radiation in that a number of laser radiation pulses are emitted in one area, with the spots 6 overlapping for a number of laser radiation pulses. Several laser radiation pulses then work together to achieve a tissue-separating effect.

However, the type of tissue separation used by the treatment device 1 is not relevant for the following description; it is only important that pulsed treatment laser radiation 2 is used for this purpose. For example, a treatment device 1 can be used, as in FIG WO 2004/032810 A2 is described. It is also essential that a large number 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/are arranged in the tissue. The pattern specifies target points for the focal position, at which one or more laser pulse(s) is (are) emitted, and defines the shape and position of the cut surface. The pattern of the target points is important for the methods and devices explained below and will be described in more detail later.

In order to correct the ametropia, the pulsed laser radiation is used to remove material from an area within the cornea 5 by separating layers of tissue there that isolate the material and then allow material to be removed. The removal of material causes a change in volume in the cornea, which results in a change in the optical imaging effect of the cornea 5, which is dimensioned precisely such that the previously determined ametropia is/is corrected as far as possible. In order to isolate the volume to be removed, the focus of the laser radiation 2 is directed to target points in the cornea 5, usually in an area lying below the epithelium and Bowman's membrane and above Decemet's membrane and the endothelium. For this purpose, the treatment device 1 has a mechanism for adjusting the position of the focus of the laser radiation 2 in the cornea 5 . This is schematic in 3 shown.

In 3 elements of the treatment device 1 are only entered to the extent that they are necessary for understanding the focus adjustment. As already mentioned, the laser radiation 2 is bundled in a focus 7 in the cornea 5, and the position of the focus 7 in the cornea is adjusted so that focused energy from laser radiation pulses is introduced into the tissue of the cornea 3 at different points to produce cut surfaces . The laser radiation 2 is provided by a laser 8 as pulsed radiation. An xy scanner 9, which is realized in one variant by two essentially orthogonally deflecting galvanometer mirrors, deflects the laser beam coming from the laser 8 two-dimensionally, so that after the xy scanner 9 a deflected laser beam 10 is present. The xy scanner 9 thus effects an adjustment of the position of the focus 7 essentially perpendicular to the main direction of incidence of the laser radiation 2 in the cornea 5 is trained. The z scanner 11 ensures that the z position of the position of the focus 7, ie its position on the optical axis of incidence, is changed. The z scanner 11 can be arranged upstream or downstream of the xy scanner 9 . The coordinates identified below as x, y, z therefore relate to the deflection of the position of the focus 7.

The assignment of the individual coordinates to the spatial directions is not essential for the functional principle of the treatment device 1, but for the sake of a simpler description, z always denotes the coordinate along the optical axis of incidence of the laser radiation 2, and x and y denote two mutually orthogonal coordinates in a plane perpendicular to the direction of incidence 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 also be provided by other coordinate systems; in particular, it does not have to be a right-angled coordinate system. It is therefore not mandatory for the xy scanner 9 to deflect about axes that are perpendicular to one another; rather, any scanner that is able to adjust the focus 7 in a plane in which the axis of incidence of the optical radiation is not located can be used. This means that oblique coordinate systems are also possible.

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

To control the position of the focus 7, the xy scanner 9 and the z scanner 11, which together implement a specific example of a three-dimensional focus adjustment device, are controlled by a control unit 12 via lines that are not designated in any more detail. 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, implemented as an example by the xy scanner 9 and the z scanner 11, so that the position of the focus 7 in the cornea 5 is adjusted in such a way that ultimately a material with a specific volume is isolated, with the subsequent volume removal effecting a desired correction of the ametropia.

The control device 12 works according to predefined control data which specify the target points for the focus adjustment. The control data is usually summarized in a control data record. In one embodiment, this specifies the coordinates of the target points as a pattern, with the order of the target points in the control data record determining the sequence of the focus positions and thus ultimately a trajectory (also referred to here as trajectory for short). In one embodiment, the control data record contains the target points as more specific control values for the focal position adjustment mechanism, e.g. for the xy scanner 9 and the z scanner 11. In preparation for the ophthalmic surgical procedure, i.e. before the actual surgical procedure can be carried out, the target points and preferably also determines their order in the pattern. The surgical intervention must be pre-planned in such a way that the control data for the treatment device 1 are determined, the use of which then achieves an optimal correction of the ametropia for the patient 4 .

First of all, the volume to be isolated from the cornea 5 and later to be removed must be determined. As already based 1a described, it requires a determination of the need for correction. 4 shows in sub-figures a), b) and c) the optical conditions on the eye 3 of the patient 4. The situation shown in sub-figure a) is present without correction of ametropia. The cornea 5, together with the eye lens 13, causes an object lying in infinity to be focused into a focus F, which lies behind the retina 14 on the z-axis. The imaging effect comes from the relaxed eye lens 13 in the non-accommodated eye and from the cornea 5, which is essentially defined by a front surface 15 and a back side 16 of the cornea and also has an imaging effect due to its curvature. The optical effect of the cornea 5 is determined by the radius of curvature Rcv of the front surface of the cornea. Subfigure a) only shows the ametropia as an example; in reality, the more complex ametropia mentioned above can be present. However, the following description also applies to them, although the equations given can then sometimes contain an additional angle dependency, even if this is not expressly pointed out.

For ametropia correction is known manner, as in sub-figure b) of 4 shown, an attachment lens 17 in the form of glasses at a distance d _HS from the apex of the cornea 5 in front of the eye 3. The lens 17 of the glasses is adjusted in its refractive power B _BR such that it shifts the far point of the entire system, ie the glasses and the eye, from the focal point F to the corrected focal point F*, which lies on the retina 14 .

With regard to the nomenclature used in this description, it should be noted that the addition of an asterisk to quantities makes it clear that they are quantities that are obtained after a correction. The focus F* is therefore that focus which is present after the optical correction which is shown in sub-figure b). 4 is achieved through the lens 17 of the glasses.

Under the justified assumption that a change in thickness of the cornea 5 essentially faces the radius of curvature of the air The radius of curvature Rcv of the front cornea 15 is modified by the volume removal. The reduced volume of the cornea 5 has such a modified imaging effect that the then corrected focus F* lies on the retina 14 . After the correction, there is a changed front surface 15* of the cornea, and a correction of ametropia is achieved even without glasses.

In order to determine the pattern of the target points, the curvature of the modified front surface 15* of the cornea that is to be achieved is therefore determined. In this case, the starting point is the refractive power of the lens 17 of the spectacles, since the determination of the corresponding parameters is a standard method in ophthalmic optics. The following formula applies to the refractive power B _BR (φ) of the lens 17 of the glasses: $${\text{B}}_{\text{BR}}\left(\mathrm{\phi }\right)=\text{sph}+\text{cyl}·{\text{sin}}^2\left(\mathrm{\phi }-\mathrm{\theta }\right).$$

In this equation, Sph and Cyl designate the correction values to be implemented for spherical or astigmatic refractive errors, and 0 the position of the cylinder 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 usual in ophthalmic optics. The curvature of the modified anterior corneal surface 15* is now set as follows with the value B _BR : $${\text{R}}_{\text{CV}}*=1/\left(\left(1/{\text{R}}_{\text{CV}}\right)+{\text{B}}_{\text{BR}}/\left(\left({\text{n}}_{\text{c}}-1\right)\left(1-{\text{i.e}}_{\text{HS}}·{\text{B}}_{\text{BR}}\right)\right)\right)+\text{f}$$

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 glasses with the refractive power B _BR must be from the corneal vertex in order to produce the desired correction of the ametropia by means of glasses; B _BR denotes the aforementioned refractive power of the glasses according to Equation (1). The specification for the refractive power B _BR can also record ametropia that go beyond a normal spherical or cylindrical correction. B _BR (and thus automatically also R _CV *) then have additional coordinate dependencies.

dc bzw. d_C* ist dabei die Hornhautdicke vor bzw. nach der optischen Korrektur. Für eine genaue Bestimmung erfolgt eine Berechnung von R_CV* iterativ, indem bei der i-ten Berechnung aus der Differenz (R_CV* - Rcv) auf die Größe (d_C* - de) geschlossen wird und das entsprechende daraus erhaltene Ergebnis für die Dickenänderung bei der (i+1)-ten Berechnung angewendet wird. Dies kann man so lange durchführen, bis ein Abbruchkriterium erfüllt wird, beispielsweise wenn die Differenz des Ergebnisses für die Dickenänderung bei zwei aufeinanderfolgenden Iterationsschritten unter einer entsprechend festgelegten Grenze liegt. Diese Grenze kann beispielsweise über eine konstante Differenz festgelegt werden, die einer für die Behandlung angemessene Genauigkeit der Refraktionskorrektur entspricht.The factor F expresses the optical effect of the change in thickness of the cornea and can be regarded as a constant factor as a first approximation. For a highly accurate correction, the factor can be calculated according to the following equation: $$\text{f}=\left(1-1/{\text{n}}_{\text{c}}\right)·\left({\text{i.e}}_{\text{C}}*-{\text{i.e}}_{\text{C}}\right).$$

dc or d _C * is the thickness of the cornea before or after the optical correction. For a precise determination, R _CV * is calculated iteratively, by inferring the size (d _C * - de) from the i-th calculation from the difference (R _CV * - Rcv) and the corresponding result obtained therefrom for the Thickness change is applied at the (i+1)th calculation. This can be carried out until a termination criterion is met, for example if the difference in the result for the change in thickness in two consecutive iteration steps is below a correspondingly defined limit. This limit can be set, for example, via a constant difference that corresponds to an accuracy of the refraction correction that is appropriate for the treatment.

If one neglects the change in thickness of the cornea, which is entirely permissible for a simplified method, F in equation (2) can also be set equal to zero for a simplified calculation, i.e. it can be neglected and omitted. Surprisingly, the following simple equation for the refractive power of the modified cornea 5* is obtained: $${\text{B}}_{\text{CV}}*={\text{B}}_{\text{CV}}+{\text{B}}_{\text{BR}}/\left(1-{\text{B}}_{\text{BR}}·{\text{i.e}}_{\text{HS}}\right)$$

From this equation, the radius R _CV * of the front surface of the cornea 15*, which must be present after the modification in order to correct the ametropia as desired, is obtained in a simple manner by means of the equation B _CV *=(n−1)/R _CV * for the person skilled in the art to get, to: R _CV * = 1 / ( (1/Rcv) + BBR / ((n _c -1) (1 - d _HS • B _BR )))

For the volume whose removal brings about the above change in curvature of the front surface 15 of the cornea, the interface isolating the volume is now defined. It should preferably be 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 in the dark-adapted eye.

In a first variant, numerical methods known to those skilled in the art are used to define an open area that circumscribes a volume whose removal brings about the change in curvature. For this purpose, the change in thickness that is necessary for the desired modification of the curvature is determined along the z-axis. This results in the volume as a function of r, φ (in cylindrical coordinates) and from this in turn its boundary surface.

The following second variant provides a simple analytical calculation, in which the boundary surface of the volume is built up by two partial surfaces an anterior facet facing the corneal surface 15 and an opposite posterior facet. The corresponding ratios are shown 5 . The volume 18 is bounded towards the front surface 15 of the cornea by an anterior cut surface 19 which lies at a constant distance _dF below the front surface 15 of the cornea. In analogy to laser keratomes, this anterior cut surface 19 is also referred to as the flap surface 19, since it serves there, in combination with an opening cut towards the edge, to be able to lift the cornea 5 a lamella in the form of a “flap” from the cornea 5 underneath . This type of removal of the previously isolated volume 18 is of course also possible here.

The anterior cut surface 19 has a curvature that lies below the front surface 15 of the cornea by _dF . If this is spherical, a radius of curvature that is smaller by dF than the radius of curvature _Rcv can be specified for the flap surface 19 . As will be described later for preferred variants, when the cut surface 19 is produced using a contact glass, it can be ensured that the front surface 15 of the cornea is spherical at the time the cut surface is produced, so that the pattern of the target points produces a spherical cut surface. The relaxation of the eye 3 after the removal of the contact glass may lead to a non-spherical cut surface 19, but it is still at a constant distance from the front surface 15 or 15* of the cornea. This will be explained later.

The volume 18 that is to be removed from the cornea 5 is bounded posteriorly by a posterior cut surface 20 which, in principle, cannot be at a constant distance from the front surface 15 of the cornea. The posterior cut surface 20 is therefore formed in such a way that the volume 18 is in the form of a lenticle, which is why the posterior cut surface 20 is also referred to as a lenticle surface 20 . In 5 it is drawn in as an example as a likewise 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 in 5 also spherical corneal front surface 15 coincides.

6 shows the conditions after the volume 18 has been removed. 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 thickness d _L of the removed volume 18 is decisive for the change in radius, such as 7 clarified. In this figure, the height h _F of the spherical cap defined by the anterior cut surface 19 , the height h _L of the spherical cap defined by the posterior cut surface 20 and the thickness d _L of the volume 18 to be removed are plotted as additional variables.

bzw. in Zylinderkoordinaten (z, r, φ) $${\text{z}}_{\text{L}}\left(\text{r},\mathrm{\phi }\right)={\text{R}}_{\text{L}}\left(\mathrm{\phi }\right)-{\left({\text{R}}_{\text{L}}{}^2\left(\mathrm{\phi }\right)-{\text{r}}^2\right)}^{1/2}+{\text{d}}_{\text{L}}+{\text{d}}_{\text{F}}.$$

Due to the constant distance between the front surface 15 of the cornea and the anterior cut surface 19, the posterior cut surface 20 defines the curvature of the front surface 15* of the cornea after the volume 18 has been removed. Thus, the posterior cut surface 20 will have an angle-dependent radius of curvature, for example in the case of a correction of ametropia that takes into account cylindrical parameters. for the inside 7 Lenticle surface 20 shown applies in general: $${\text{R}}_{\text{L}}\left(\mathrm{\phi }\right)={\text{R}}_{\text{CV}}*\left(\mathrm{\phi }\right)-{\text{i.e}}_{\text{f}},$$

or in cylindrical coordinates (z, r, φ) $${\text{e.g}}_{\text{L}}\left(\text{right},\mathrm{\phi }\right)={\text{R}}_{\text{L}}\left(\mathrm{\phi }\right)-{\left({\text{R}}_{\text{L}}{}^2\left(\mathrm{\phi }\right)-{\text{right}}^2\right)}^{1/2}+{\text{i.e}}_{\text{L}}+{\text{i.e}}_{\text{f}}.$$

If astigmatism is not taken into account, there is no dependency on φ and the lenticle surface 20 is spherical. However, assuming the need for a cylindrical correction of ametropia, the lenticle surface 20 generally has different radii of curvature on different axes, these naturally usually having the same vertex.

This automatically makes it clear that in the case of a cylinder correction, the theoretical line of intersection between the flap surface 19 and the lenticle surface 20 does not lie in one plane, ie at constant z coordinates. The smallest radius of curvature of the lenticle surface 20 is at φ=0+π/2, the largest of course on the 0 axis of the cylindrical ametropia, ie at φ=θ. In the case of a clarity correction, the presentation of the 7 the apex of flap surface 19 and lenticle surface 20 together and the lenticle surface 20 is more strongly curved than the flap surface 19. The thickness d _L of the lenticle results in the edge thickness.

The volume 18 to be considered as a lenticle has the smallest edge thickness at φ=θ=π/2, since the lenticle surface 20 and the flap surface 19 intersect there. For all other values for φ, if a given z-coordinate is taken as the lower limit of the lenticle surface 20, then a finite edge thickness is given.

Alternatively, in addition to the flap surface 20 and the lenticle surface 19, an additional edge surface can be provided, which borders the volume 18 in the intersection area of the flap surface 20 and the lenticle surface 19 or connects these surfaces where they are at a given z-coordinate do not converge. The cut of this edge surface is also made with the pulsed laser beam leads. The edge surface can have a cylindrical shape, for example, which can also have an elliptical shape (in top view) or a conical shape (in side view).

The formation of the volume 18 shown in the figures as delimited by an anterior cut surface 19 at a constant distance from the front surface 15 of the cornea and a posterior cut surface 20 is only one variant for delimiting the volume 18. However, it has the advantage that the optical correction is only significantly is defined by a surface (the lenticule surface 20) so that the analytical description of the other partial surface of the interface is easy.

Furthermore, optimum safety margins are offered with regard to the distance of the volume from the front surface 15 and the rear surface 16 of the cornea. The residual thickness d _F between the anterior cut surface 19 and the front surface 15 of the cornea can be set to a constant value of, for example, 50 to 200 μm. In particular, it can be selected in such a way that the pain-sensitive epithelium remains in the lamella formed by the flap surface 19 under the front surface 15 of the cornea. The formation of the spherical flap surface 19 is also in continuity with previous keratometer sections, which is advantageous for the acceptance of the method.

After the cut surfaces 19 and 20 have been produced, the volume 18 isolated in this way is then removed from the cornea 5 . This is schematic in 8th shown, which also makes it clear 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 a row, so that in a preferred embodiment the flap cut surface 19 and the lenticle cut surface 20 are formed by suitable three-dimensional Adjustment of the focal position of the pulsed laser radiation 2 are generated.

Alternatively, in a simplified embodiment, only the flap surface 19 can be formed by target points that define the curved cut surface 19 at a constant distance from the front surface 15 of the cornea by means of pulsed laser radiation, and the volume 18 is removed by laser ablation, for example by using an excimer laser beam. For this purpose, the lenticle surface 20 can be defined as the boundary surface of the ablation, even if this is not absolutely necessary. The treatment device 1 works like a known laser keratome, but the cut surface 19 is produced on a curved cornea. The features described above and below are also possible in such variants, in particular with regard to the determination of the boundary surface, its geometric definition and the determination of control parameters.

If both the lenticle surface 20 and the flap surface 19 are generated by means of pulsed laser radiation, it is advisable to form the lenticle surface 20 in front of the flap surface 19, since the optical result is better with the lenticle surface 20 (if not can only be achieved at all) when no change in the cornea 5 has occurred above the lenticle surface 20.

The volume 18 isolated by the pulsed laser radiation can be removed, as in 8th indicated, be achieved by an edge cut 22, which allows the volume 18 in the direction of an in 8th Drawn arrow 23 pull out. Alternatively, the edge cut 22 can be formed in such a way that it connects the anterior cut surface 19, ie the flap surface 19, to the front surface 15 of the cornea in the form of a ring, although the edge cut does not completely encircle an angle of 360°. The lamella isolated in this way remains connected to the remaining tissue of the cornea 5 in a narrow area. This connecting bridge then serves as a hinge in order to be able to fold down the otherwise isolated lamella from the cornea 5 and to be able to remove the already isolated volume 18 that is accessible as a result 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. From this point of view, the procedure and device described thus realizes the isolation of the volume 19 within the cornea 5 and the generation of a lamella connected to the rest of the cornea via a tissue bridge as a cover over the volume. The cover can be folded down and the volume 18 can be removed.

For the production of the cut surfaces 19 and 20, the target points can now be arranged in a wide variety of ways. In the prior art, for example, in the WO 2005/011546 described for the production of cut surfaces in the cornea that special spirals can be used which, for example, run around a main axis lying essentially perpendicular to the optical axis (z-axis) in the manner of a helical line. The use of a scan pattern that arranges the target points in rows is also known (cf. WO 2005/011545 ). Of course, these possibilities can be used to generate the cut surfaces defined above and with the transformations explained below.

The position of the focus in the cornea is adjusted using the in 3 schematically illustrated three-dimensional Ablenkeinrich tion that uses the displacement of lenses or other optically effective elements to adjust the focus in the z-direction. Now the adjustment of lenses or similar is usually not possible as quickly as the swiveling of mirrors, which are usually used in xy scanners. Therefore, the adjustment speed of the z-scanner is usually limiting for the speed with which the cut surfaces can be generated in the cornea. In order to produce the cut surfaces 18 and 19 as quickly as possible, in a preferred embodiment the focus is guided along a spiral path in each case, with one spiral each lying in the three-dimensionally curved cut surface. During the writing of the spiral, the z-scanner is adjusted in such a way that the arms of the spiral follow the spatially curved cutting surface.

9 shows an example of a trajectory 24 as a spiral, which is designed as a circular spiral in the illustration shown. The radius of the planar spiral shown increases in circular coordinates with increasing angle of rotation φ, so that: $$\text{right}\left(\mathrm{\phi }\right)=\mathrm{\phi }·{\text{i.e}}_{\text{T}}/\left(2\mathrm{\pi }\right)$$

In this equation, d _T denotes the spacing of the spiral arms; he is in 10 shown showing an enlarged section of the 9 displays. The distance between the individual spots 6, onto which pulsed laser radiation is focused and at which a plasma bubble is generated by a laser pulse, for example, is constantly equal to ds in the spiral, so that for the angular distance Δφ of the individual spots 6, at which a laser pulse enters the tissue is introduced, the following applies: $$\mathrm{\Delta \phi }={\text{i.e}}_{\text{S}}/\text{right}$$

Since, as already mentioned, the lenticle surface 20 is generally non-spherical, the trajectory 24 along which the laser focus is adjusted is an elliptical spiral, for which there is of course no longer a constant distance between the spiral arms. However, a respective path distance d _Tb and d _Ta can be defined along the main axes a and b, as 11 displays.

In 10 the spots 6 are shown in order to show the position of the focus for the individual laser pulses. In fact, after the introduction of the respective laser pulse, the plasma bubbles naturally widen to such an extent that the cut surface is produced and the path curve 24 can then no longer be recognized in the cut surface.

In preparation for the surgical procedure, once the cut surfaces 19 and 20 have been defined, the trajectories 24 with which the cut surfaces are produced must now be defined.

When determining the trajectories 24, it must of course be taken into account that ultimately the volume 18 in the eye should be defined in the normal state. The cut surfaces 19 and 20, as explained so far, relate to the natural eye. However, it must now be taken into account that the treatment device 1 works with a contact glass 25 for reasons of fixation of the eye, which as in 12 is shown, is placed on the corneal front surface 15 of the cornea 5 . The contact glass 25, which is already the subject of several patent publications (for example, refer to WO 2005/048895 A1 referenced), is only of interest for the present description of the treatment device 1 and the associated methods for preparing and/or performing the surgical intervention insofar as it gives the front surface 15 of the cornea a defined curvature on the one hand and the Cornea 5 against the treatment device 1 holds 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 as it is used, for example, in FIG WO 2003/002008 A1 is described which uses a planar contact lens which flattens the cornea.

If the eye is pressed against the contact glass 25 with a spherical contact surface, a spatial deformation of the eye occurs. Since the cornea is usually only tangentially compressible, i.e. its thickness does not change when it is pressed in this way, the pressing corresponds to a transformation of the coordinate system of the eye, as shown in 13 is shown, into the coordinate system of the contact glass, which is shown in 14 is shown. This connection is the expert from the WO 2005/011547 A1 known, the disclosure content of which should be fully integrated in this regard. In the 13 and 14 Coordinates provided with an apostrophe denote the coordinates of the quantities related to the contact glass 25 or its underside 26 of the contact glass facing the eye.

But the contact glass has another advantage. By pressing against the spherical underside 26 of the contact glass, the front surface 15 of the cornea is also automatically spherical. The anterior cut surface 19 lying at a constant distance below the front surface 15 of the cornea is therefore also spherical when the contact glass is pressed on, which leads to considerably simplified control. It is therefore preferred, completely independently of other features, to use a contact glass 25 with a spherical contact glass underside 26 and to limit the volume by an anterior cut surface 19 and a posterior cut surface, where target points are/are specified for the anterior cut surface, which form this cut surface as a spherical surface at a constant distance d _F below the front surface 15 of the cornea. Target points are/are specified for the posterior cut surface, which define a course of curvature which, when the eye is relaxed, i.e. after removing the contact glass, corresponds to the distance d _F to the front surface of the cornea that is desired for correcting ametropia. The same applies to the method for defining the target points or the surgical method.

The depictions in the 13 and 14 show the coordinate transformation that occurs in the eye when the contact glass is put on or taken off. They contain both spherical coordinates (R, α, φ) related to the origin of the curved surface (corneal front surface 15 or contact lens underside 26) and cylindrical coordinates (r, z, φ) related to the apex of the corneal front surface defined by the point of passage of the optical axis OA 15 or the underside of the contact glass 26.

In the case of the coordinate transformation from the coordinate system related to the eye, as described in 13 is shown into the system related to the contact glass according to FIG 14 the arc length, ie α•R, the radial depth (Rcv - R) and the angle φ are conserved. The transformation of the for the natural eye, ie in the coordinate system of 13 , underlying forms of the cut surfaces 19 and 20 is therefore an important step in the calculation of the control variables for the three-dimensional focus adjustment device. It runs fundamentally differently than in the case of a flat contact glass, in which, for example, the flap surface 19 degenerates into a plane. Essentially, only the shape for the cut surface 20 has to be transformed, since the cut surface 19 only has to be formed at a constant distance d _F from the front surface 15 of the cornea. In the transformed system, the cut surface 19 is therefore a sphere with a radius of curvature R _F reduced by d _F compared to the underside of the contact glass.

The pressing of the cornea 5 of the eye 3 against the spherically curved contact lens underside 26 is in 15 illustrated. There, the illustration on the right schematically shows the state when the underside of the contact lens 26 is only in contact with the front surface 15 of the cornea at the vertex. To clarify the geometric relationships, the front surface of the cornea 15 is shown schematically in 15 drawn as a circle, although of course the spherical curvature is only present in a smaller section of the circle. The pressing of the contact glass 25 on the cornea 5 causes the transition to the state of the left side of the symbolized by arrow 27 15 . The removal of the contact lens 25 causes the eye 3 to relax in the opposite direction of the arrow 27

Due to the framework conditions described, the coordinates of each point in the cornea 5 are transformed from the in 13 illustrated system into the system of 14 . This is now taken as a basis when selecting the control values for the focus adjustment in such a way that the cut surfaces 19 and 20 are to be described in the transformed contact lens system, since they only have the desired have shapes. Since the anterior surface 15 of the cornea is generally applied by suction using negative pressure, the transformation described is also referred to below as suction transformation.

wobei f_L die Frequenz der Laserpulse der Laserstrahlung 2 ist. Gleichung (5) setzt voraus, dass die z-Geschwindigkeit vz frei eingestellt und kontinuierlich verändert werden kann.To cut the flap surface 19, which as mentioned is spherical, the following speed of adjustment of the z scanner, ie the following feed speed in the z direction, is set: $${\text{v}}_{\text{Z}}\left(\text{t}\right)={\text{i.e}}_{\text{S}}·{\text{f}}_{\text{L}}·{\text{i.e}}_{\text{T}}/{\left(2\mathrm{\pi }·\left({\text{R}}_{\text{f}}{}^2-\text{t}·{\text{i.e}}_{\text{S}}·{\text{f}}_{\text{L}}·{\text{i.e}}_{\text{T}}/\mathrm{\pi }\right)\right)}^{\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.},$$

where f _L is the frequency of the laser pulses of the laser radiation 2 . Equation (5) assumes that the z speed vz can be freely set and continuously changed.

sowie für die Winkelfunktion $$\mathrm{\phi }\left(\text{t}\right)={\left[4\mathrm{\pi }·{\text{d}}_{\text{S}}·{\text{f}}_{\text{L}}·\text{t}/{\text{d}}_{\text{T}}-({\text{d}}_{\text{S}}·{\text{f}}_{\text{L}}·{\text{t}}^2/{\text{R}}^2\right]}^{1/2}.$$

If one wants to write a sphere with a velocity vz, which is selected from a group of discrete velocities, which is usually the case when the z-scanner is driven by a stepping motor, one obtains the time dependence of the radial function r(t): $$\text{right}\left(\text{t}\right)={\left[{\text{i.e}}_{\text{S}}·{\text{f}}_{\text{L}}·{\text{i.e}}_{\text{T}}·\text{t}/\mathrm{\pi }-{\left({\text{i.e}}_{\text{S}}·{\text{f}}_{\text{L}}·{\text{i.e}}_{\text{T}}·\text{t}\right)}^2/{\left(2\mathrm{\pi }·{\text{R}}_{\text{f}}\right)}^2\right]}^{1/2}$$

and for the angle function $$\mathrm{\phi }\left(\text{t}\right)={\left[4\mathrm{\pi }·{\text{i.e}}_{\text{S}}·{\text{f}}_{\text{L}}·\text{t}/{\text{i.e}}_{\text{T}}-({\text{i.e}}_{\text{S}}·{\text{f}}_{\text{L}}·{\text{<figure-callout id="2" label="t" filenames="DE102006053118B4\_0022.png,DE102006053118B4\_0025.png" state="{{state}}">t</figure-callout>}}^2/{\text{R}}^2\right]}^{1/2}.$$

The t ² terms under the root of the radial and angle functions show that an ideal Archimedean spiral is no longer written, so the orbit and spot bubble distances vary in favor of the z-velocity, which can only be changed in steps.

If you want a constant z-feed when adjusting the focus, this is not the case with the velocity according to equation (4) is a sphere, but a paraboloid, and the following applies: $$\text{e.g}\left(\text{right}\right)=\left[{\text{v}}_{\text{Z}}/\left(\text{ds}·\text{dr}\right)\right]\left[{\text{right}}^2·\mathrm{\pi }/{\text{f}}_{\text{L}}\right]$$

As mentioned, 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 wants to describe a specific parabola with a given velocity vz, the product _dS • _dT must be chosen accordingly, so that the first square brackets of equation (8) assume the desired value. The spacing of the trajectories, defined by d _T , and the spot spacing along the trajectory, described by ds, are thus suitable to vary in order to write a given parabola with given vz.

Each of the equations (5), (6)/(7) and (8) can be used to determine the target points and thus to control the focus adjustment, in which case the corresponding spiral shape/area shape is of course to be used as a basis. When it is mentioned below that the equations are used for the control, this means in particular that the target points are determined by means of the equations, which can be done, for example, by evaluating the function equations at equidistant points in time. In one variant, the speed equations are used to ensure that the determined target points do not require any adjustment speeds that cannot be achieved by the focus adjustment device.

For the shapes of the surfaces 19 and 20 that were mentioned at the beginning and were determined as described, a spiral is now placed in the respective surface. You spiral is written by a control of the type described. The calculation of the z-speed and the r- and φ-speed takes into account the surface shape of the surface 19 or 20.

The lenticle surface 20 is spherical if no cylinder correction is to be made. Therefore, the control according to equations (4)/(5) or (6)/(7) is used to generate this sphere. However, as is known, a sphere can also be approximated by a paraboloid. It is therefore provided in a variant that a sphere is approximated by a paraboloid in a manner known to those skilled in the art and the control is carried out according to equation (8).

By the intake transformation according to 15 the geometry of the lenticle surface 20 changes. In the coordinate system of the contact glass 25, the lenticle surface 20 must have the course of curvature of the corrected corneal front surface 15*. It cannot be related to a center of curvature that coincides with the center of curvature of the contact lens. The curvature defined according to equation (2) is therefore converted with regard to the intake transformation.

The radius of curvature defined in equation (2) is of course a function of φ. As already mentioned and as is customary in ophthalmic optics, two radii of curvature r _a and r _b can be specified: one on the axis θ of the cylindrical ametropia and one for an axis perpendicular to it. In terms of computation, it is particularly favorable to approximate the toroidal curvature that occurs in the general case with a parabola, so that the lenticle surface 20 is approximated with a paraboloid. This is preferably done before the compression transformation, but it can also be done afterwards.

The approximation is carried out by looking for a parabola for each of the two radii of curvature, which runs both through the vertex of the lenticle surface 20 and through a point located 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 surface 20 prior to compression transformation. In the figure, the sections through the lenticle surface 20, which is toroidal in the generalized case, are superimposed along the two semi-axes a and b. The corresponding curves are labeled R _a and R _b , respectively, and are circular with radius of curvature r _a and r _b , respectively. On each curve, an edge point T is described in cylindrical coordinates by the corresponding radius r and the height h, these parameters being related to the vertex S, which is identical for the two semi-intercepts. The point T _a is thus characterized by the radius r _a and the height h _a . The same applies to T _b .

A parabola is now sought for which h = k - r ² . The thus obtained parabola parameters h _a for the parabola along the major semi-axis a and k _b for the parabola along the minor semi-axis b define the paraboloid, which is then written in the z-direction by adjusting the focal point, for example by means of a constant z-feed ( cf. Equation (7)) or which is selected with a selection of the z-velocity from a set of discrete velocities (modification of equation (7)). In the 16 The illustrated sections of the toroidal lenticle surface 20 along the minor main axis b and the major main axis a relate to the representation in the coordinate system of the eye.

If the approximation was carried out using parabola equations after the compression transformation, the transformed values naturally appear there. The explicit calculation of transformed values can be avoided at this point if the approximation is carried out first and the parabola parameters found are subjected to the contact pressure transformation into the coordinate system of the contact lens, after which the in 17 conditions shown are present.

$${\text{k}}_{\text{b}}=\left(\text{z}\left({\text{T}}_{\text{b}}\right)-\text{z}\left(\text{S}\right)\right)/\text{r}{\left({\text{T}}_{\text{b}}\right)}^2.$$

The specification of the parabola parameters is in the coordinate system of the eye according to 16 as follows: $${\text{k}}_{\text{a}}=\left(\text{e.g}\left({\text{T}}_{\text{a}}\right)-\text{e.g}\left(\text{S}\right)\right)/\text{right}{\left({\text{T}}_{\text{a}}\right)}^2,$$

$${\text{k}}_{\text{b}}=\left(\text{e.g}\left({\text{T}}_{\text{b}}\right)-\text{e.g}\left(\text{S}\right)\right)/\text{right}{\left({\text{T}}_{\text{b}}\right)}^2.$$

In equations (9) and (10), z(S) designates the z-coordinate of point S. If the origin of the coordinate system is placed at the vertex, as in the previous figures, the z-coordinate is zero. The coordinate z(T _a ) or z(T _b ) and r(T _a ) or r(T _b ) are the z or r coordinates of the corresponding point T _a or T _b in the cylindrical coordinate system.

If the parabola parameters k _a and k _b are not in accordance with the coordinate system of the eye 16 , but according to the coordinate system of the contact glass 17 required, instead of the points S, Ta and Ta the in 17 drawn transformed points S', Ta', T _b '.

In order to represent the lenticle surface 20 in the pressed-on eye 3 by a (then usually elliptical) spiral with the main axes r _a ' and r _b ', the spiral becomes a circular spiral with radius ro' by stretching in the direction φ = 0 and compression in direction φ = θ + π/2. Due to the simultaneous compression and stretching, the average track or spot distance is retained. If you only compress or stretch in one direction, the average distance would change.

The actual radii can be calculated from the radius ro of the circular spiral, which is 17 is drawn in dashed lines, calculated with the help of ellipticity as follows: $$\text{e}\text{'}={\text{right}}_{\text{a}}\text{'}/{\text{right}}_{\text{b}}\text{'}={\left({\text{k}}_{\text{B}}\text{'}/{\text{k}}_{\text{a}}\text{'}\right)}^{1/2}.$$

The ellipticity e' is the ellipticity of the transformed toroidal lenticle surface 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 ' given. The parabola parameters result from the fact that the circular spiral with the radius ro, from which the lenticle surface 20 is constructed, should be an arithmetic or geometric mean of the curvatures of the major or minor semi-axis of the paraboloid. Because ro' = (r _a ' • r _b ') ^1/2 one obtains for the parabola parameter k = (k _a • k _b ) ^1/2 and the main axes of the ellipse: r _a ' = r ₀ ' • (e' ) ^1/2 and r _b ' = r ₀ •(e')- ^1/2 .

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

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

The focal position error is taken into account by means of a generally non-linear transformation (hereinafter also referred to as NL transformation). It is therefore not possible to perform the NL transformation by modifying the trajectory parameters. In a preferred embodiment, the focal position error is expressed by a correction table or a correction function. It comes from a measurement 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, e.g. B. can be obtained by means of polynomials or splines. The focal position error is usually rotationally symmetrical in relation to the optical axis. It then depends only on r and z in cylindrical coordinates.

The points previously calculated using the trajectories are predistorted in the NL transformation in such a way that, after the laser spots have been introduced, they are exactly at the desired point using the optical system that has the focal position error. The use of the pre-distorted coordinates thus compensates for the focal position error occurring in the optical system.

The NL transformation is based on the consideration that for every point with the coordinates (z, r) one finds a contact glass sphere shifted by zo on which this point lies. The vertex of this sphere is then just at zo(z, r) = z - z _KGL (r). The effect of the pre-distortion to compensate for the focal position error is in 18 arrange insight. It shows the contact glass underside 26, which is spherical in the present example, but can also have a different shape. Because of the predistortion, it becomes a transformed contact glass sphere 26^. The parameters considering the predistortion of the focal position error are in 18 symbolized by an added roof "^". For a transformed axis point in the cornea, z ₀ ^=zo then applies. This takes into account the fact that although the focus position error is mostly rotationally symmetrical, it also results in a shift in the z-direction.

For pre-distortion, the calculated trajectories are converted into individual target point coordinates for the spots, which are then displayed in the in 18 correction transformation symbolized by K(r, z), i.e. the NL transformation. If the focus position error is specified as a function K, the coordinates of each target point only have to be evaluated with the function in order to obtain the shift or the transformed coordinates.

As a result, there is then a set of target point coordinates for the surfaces 19 and 20 along which the focus is guided. Due to the NL transformation and the contact pressure transformation, the coordinates, based on the natural, i.e. free eye, lie exactly in the desired anterior and posterior cut surfaces 19, 20.

The coordinates for the target points obtained in this way still have to be converted into control signals for the three-dimensional deflection unit, e.g. the xy scanner and the z scanner. For this purpose, a corresponding functional relationship or a corresponding characteristic diagram is used, which is known for the scanner and may have been determined beforehand.

The response function was previously determined in particular for the xy scanners, which are implemented as galvanometer mirrors in the exemplary embodiment. Frequency sweeping the galvanometer mirrors and measuring the actual galvanometer movement provides an amplitude and phase response function. These are taken into account when determining the control signals.

Furthermore, for simplified control, a signal for the target to be approached is not given to the scanner for each point. Instead, the control device 12 causes a specification of reference points that characterize the path of the scanner. This significantly reduces the number of points. This can already be used to advantage in the NL transformation, in that for the trajectories only those target points are subjected to the transformation which are intended to be interpolation points in the control. In one embodiment, the functional equations are evaluated by means of a time interval that is less than the time interval of the laser pulses.

Thus, before the NL transformation, the trajectory points are filtered, which provides the support points mentioned, i.e. points at a frequency of the scanner control for the transformation. Equivalent to such filtering is an evaluation of the functionally described trajectories at interpolation points spaced apart according to the scanner control. This is where another advantage of the function-based approach described here comes to light: the decision as to which points are target points when controlling the focus adjustment device only has to be made before the NL transformation. Beforehand, only the path parameters have to be suitably converted. Only then are data sets with a large number of points available.

The interpolation points thus define target points that form only a subset of the set of points to which a laser pulse is emitted. this is in 10 illustrated, in which those spots 6 which are a target point 28 in the control data set are drawn in as black, filled-in circles.

This procedure also has the advantage that the maximum frequency fs that occurs when the scanner is controlled is much lower than the laser pulse frequency _fp . For example, a control frequency of 20 kHz and a laser pulse frequency of 200 kHz can be used. As a result, there are one or more spots 6 between the target points 28, which are specified when the scanner is actuated, onto which pulsed laser radiation is also emitted.

Thus, not only is pulsed laser radiation emitted while the scanners are in an adjustment process, for example while the galvanometer mirrors are moving, but laser pulses are deflected by the scanners while they are moving from one predetermined target point to the next. In order to achieve as high a deflection speed as possible, this movement represents an oscillation which, in the case of perfect circular spirals (as occur in the case of the anterior cut surface 19), is even a purely sinusoidal oscillation. Since the actual spiral shape of the lenticle surface 20 also deviates only slightly from ideal circular or elliptical spirals, the scanners can be operated close to their cut-off frequency, so that the paths described along which the spots are arranged allow very rapid generation of cut surfaces.

After the determination of the control data sets containing the target points from the sets of points described, which were obtained for the trajectories, the pre-process that was carried out to provide the corresponding control values or parameters is completed. Human participation and in particular the participation of a doctor or surgeon is not required for this preliminary procedure. The method is carried out by the control unit 12 without the intervention of a doctor. Its presence is only required for the subsequent surgical intervention.

The sequence of the method for preparing the device 1 for use in an ophthalmic operation for ametropia is shown schematically in 19 summarized. In a step S1, the measurement of the eye 3 takes place. In the process, correction parameters are obtained for the ametropia present in the patient 4, such as are customary, for example, for conventional spectacles. The parameters set up in step S2 are then used in step S3 to determine the new curvature of the cornea 5 required for the correction. If this calculation is completed in step S3, the volume that has to be removed from the cornea is determined in S4. This usually takes place by determining the lenticle area 20 and the flap area 19 in a step S5. Once the corresponding functional descriptions of these surfaces have been obtained, the suction transformation, which has an effect when the eye is sucked onto the contact glass, is taken into account in step S6.

Next, the coordinates of the trajectories are determined, from which the cut surfaces are built. This is indicated schematically in step S7 by the parameters r, φ, z. At the end of step S7 there is a point pattern with the coordinates of the spots on which a laser radiation pulse is intended to act. In this case, the density of the target points can already be reduced in order to simplify the computational effort by not specifying a support point for each spot to which laser radiation is applied when controlling the scanner.

The set of coordinates obtained in this way is then transformed again in step S8 to take account of the focal position error. The actual control parameters are then determined in a step S11, with a response function being included, which was obtained in a step S10 from a previous measurement (step S9) of the amplitude and frequency behavior of the scanner.

The actual operation is then carried out in step S12 with the control parameters determined in this way, in which additional spots with laser radiation pulses are now preferably applied between the individual support points on which the control of the scanner is based.

Claims (28)

Planning device for determining control data for a treatment device (1) for the surgical correction of ametropia in an eye (3) of a patient (4), wherein - the planning device (P) generates the control data for a treatment device (1), which has a contact lens (25) for Placement on the eye (3) and a laser device (L), which separates corneal tissue by irradiating pulsed fs laser radiation (2), the laser radiation (2) passing through the attached contact glass (25) in a pattern within the cornea (5) lying target points (28) is focused, and wherein the planning device (P) - has an interface (S) for supplying measurement data on parameters of the eye (3) and ametropia data on the ametropia of the eye (3) to be corrected, wherein the ametropia data include the refractive power B _BR of glasses (17) suitable for ametropia correction, and the distance d _HS at which the glasses (17) with the refractive power aft B _BR must lie in front of the corneal vertex in order to achieve the desired correction of the ametropia by means of the glasses (17), - a volume (18) is defined from supplied measurement and ametropia data, which lies within the cornea (5) and its distance from the cornea (5) brings about the desired correction of the ametropia, - defines a boundary surface (19, 20) which delimits the defined volume (18) within the cornea (5), and - for this boundary surface (19, 20) a control data record for controlling the laser device ( L) that defines a three-dimensional pattern of the target points (28) in the cornea (5) that lie in the interface (19, 20) in order to separate the corneal tissue in the interface (19, 20). setup after claim 1 , characterized in that an OCT is connected to the interface (S), which generates the measurement data and the ametropia data from a measurement of the eye and feeds them to the planning device (P). Device according to one of the above claims, characterized in that the planning device (P) defines the boundary surface (19, 20) in such a way that a lamella, which is separated from the anterior part (19) of the boundary surface (19, 20) and the front side of the cornea (15 ) is limited, is formed and that this lamella has a thickness of 50 µm to 200 µm. setup after claim 3 , characterized in that the planning device (P) defines the interface (19, 20) in such a way that the epithelium of the cornea (5) lies in the lamella. Device according to one of the above claims, characterized in that the planning device (P) for removing the volume (18) after formation of the cut surface defines a cut (22) leading from the volume (18) to the front side (15) of the cornea and in that the planning device ( P) has a display device for the visual representation of control data of the control data record and an input device for subsequently changing the position of the section (22). Device according to one of the above claims, characterized in that the contact glass (25) when placed on the eye (3) deforms the cornea (5) and that the planning device (P) volume (18) and the interface (19, 20) for defines the free eye, i.e. the eye not deformed by the contact lens (25), and when generating the control data set containing the pattern of the target points (28), the deformation of the cornea (5) of the eye (3) that occurs during irradiation of the pulsed laser radiation through the contact glass (25) is present. Device according to one of the above claims, characterized in that the planning device (P) optical focal position errors, which lead to a deviation between the specified and actual position of the target points (28) in the cornea (5) when focusing the pulsed laser radiation (2). the generation of the control data set is taken into account by a lead (K) dependent on the position of the respective target point (28) and is thus compensated. setup after claim 6 , characterized in that the planning device (P) accesses a correction table or function (K) which indicates the focal position error as a function of the position of the respective target point (28). Device according to one of the above claims, characterized in that the planning device (P) when defining the volume (18) uses a radius of curvature R _CV * which satisfies the following equation $${\text{R}}_{\text{CV}}*=1/\left(\left(1/{\text{R}}_{\text{CV}}\right)+{\text{B}}_{\text{BR}}/\left(\left({\text{n}}_{\text{c}}-1\right)\left(1-{\text{i.e}}_{\text{HS}}·{\text{B}}_{\text{BR}}\right)\right)\right)+\text{f},$$

where Rcv is the radius of curvature of the cornea (5) before removal of the volume (18), R _CV * is the radius of curvature of the cornea (5) after removal of the volume (18), _nc is the refractive power of the cornea (5) material and F is a factor is. setup after claim 9 , characterized in that $$\text{f}=\left(1-1/{\text{n}}_{\text{c}}\right)·\left({\text{i.e}}_{\text{C}}*-{\text{i.e}}_{\text{C}}\right)$$

applies, where dc or d _C * denotes the thickness of the cornea (5, 5*) or after removal of the volume (18) and the planning module (P) calculates the radius R _CV * iteratively by using the difference at each iteration step (R _CV * - Rcv) is deduced from the quantity (d _C * - de) and the corresponding result obtained therefrom for the change in thickness is used in the calculation of R _CV * in the next iteration step. setup after claim 10 or 9 , characterized in that the planning device (P) divides the boundary surface into an anterior and a posterior partial surface (19, 20), wherein at least one of the partial surfaces (20) is not at a constant distance from the front side of the cornea (15) and that the not at a constant The partial surface (20) lying at a distance from the front of the cornea has the radius of curvature R _CV *, but reduced by the constant distance that the other partial surface (19) has from the front of the cornea (15). Treatment device for the surgical correction of ametropia of an eye (3) of a patient (4), the - an interface (S) for supplying measurement data on parameters of the eye (3) and ametropia data on the ametropia to be corrected in the eye (3), - a laser device (L), which separates corneal tissue by irradiating pulsed laser radiation (2), the laser radiation (2) being focused on target points (28) lying in a pattern in the cornea (5), and - comprises a planning device according to any one of the above claims. device after claim 12 , characterized in that the laser device (L) adjusts the focused laser radiation (2) along a path (24) over the pattern of the target points (28) and pulses of the pulsed laser radiation (2) into the cornea (5) also to points (6 ) that are on the path (24) between the target points (28). device after Claim 13 , characterized in that the laser device emits the pulses of the pulsed laser radiation (2) into the cornea (5) at a frequency f _P and in that the control data record contains the pattern of the target points (28) in such a way that the target points (28) have a frequency fs are specified, which is smaller than the frequency f _P. Method for preparing control data for a treatment device (1) for the surgical correction of ametropia in a patient's eye, which has a laser device (L) which separates corneal tissue by irradiating pulsed laser radiation (2), the laser device (L) having a contact glass (25 ) for placing on the eye (3) and during operation the laser radiation (2) through the contact glass (25) according to the control data in a pattern in the cornea (5) lying target points (28), wherein the method by the following Steps is marked: - Determining measurement data on parameters of the eye (3) and ametropia data on the ametropia to be corrected in the eye (3), the ametropia data being the refractive power B _BR of glasses (17) suitable for ametropia correction, and the distance d _HS include, in which the glasses (17) with the refractive power B _BR must be in front of the corneal vertex to the desired ametropia t correction by means of the glasses (17), - defining a volume (18) from the measurement data and the ametropia data, the volume (18) lying within the cornea (5) and the distance of the Volume (18) from the cornea (5) results in the desired correction of the ametropia, - definition of a boundary surface (19, 20) which delimits the defined volume (18) within the cornea (5), and - definition of a three-dimensional pattern of target points (28) in the cornea (5), wherein the target points (28) are in the interface (19, 20) and are arranged in such a way that the interface (19, 20) when irradiated with the pulsed laser radiation (2) according to the control data as cutting surface is formed, - generating a control data set containing the three-dimensional pattern for controlling the laser device (2). procedure after claim 15 , characterized in that the measurement data and the ametropia data are generated from a measurement of the eye (3) by means of OCT. Method according to one of the above method claims, characterized in that the planning device (P) defines the boundary surface (19, 20) in such a way that a lamella, which extends from the anterior part (19) of the boundary surface (19, 20) and the front side of the cornea (15 ) is limited, is formed and that this lamella has a thickness of 50 µm to 200 µm. Method according to one of the above method claims, characterized in that the interface (19, 20) is defined in such a way that the epithelium of the cornea (5) lies in the lamella. Method according to one of the above method claims, characterized in that the contact glass (25) deforms the cornea (5) when it is placed on the eye (3) and that when the boundary surface (19, 20) or the three-dimensional pattern of the target points (28 ) a deformation of the eye (3) is taken into account, which occurs during irradiation of the pulsed laser radiation (2) through the contact glass (25). Method according to one of the above method claims, characterized in that optical focal position errors, which lead to a deviation between the specified and actual position of the target points (28) in the cornea (5) when the pulsed laser radiation (2) is focused, are taken into account when determining the boundary surface ( 19, 20) or the three-dimensional pattern of the target points (28) are taken into account by a lead (K) dependent on the position of the respective target point (28). procedure after claim 20 , characterized in that a correction table or function (K) is used to determine the lead, which indicates the focal position error as a function of the position of the respective target point (28). Method according to one of the above method claims, characterized in that when defining the volume (18), the following equation is used for a radius of curvature R _CV * that the front cornea (15*) of the eye (3) assumes after the volume (18) has been removed : $${\text{R}}_{\text{CV}}*=1/\left(\left(1/{\text{R}}_{\text{CV}}\right)+{\text{B}}_{\text{BR}}/\left(\left({\text{n}}_{\text{c}}-1\right)\left(1-{\text{i.e}}_{\text{HS}}·{\text{B}}_{\text{BR}}\right)\right)\right)+\text{f},$$

where Rcv is the radius of curvature of the cornea (5) before removal of the volume, n _c is the refractive power of the cornea (5) material and F is a factor. procedure after Claim 22 , characterized in that $$\text{f}=\left(1-1/{\text{n}}_{\text{c}}\right)·\left({\text{i.e}}_{\text{C}}*-{\text{i.e}}_{\text{C}}\right)$$

applies, where dc or d _C * denotes the thickness of the cornea (5, 5*) before or after removal of the volume (18) and the radius R _CV * is calculated iteratively by taking the difference (R _CV * - Rcv) on the quantity (d _C * - de) is deduced and the corresponding result obtained from this for the change in thickness is used in the calculation of R _CV * in the next iteration step. procedure after Claim 22 or 23 , characterized in that the interface in an anterior and a posterior partial surface (19, 20) which intersect, wherein at least one of the partial surfaces (20) is not at a constant distance from the front side of the cornea (15) and that the partial surface is not at a constant distance from the front side of the cornea (15). (20) is curved with a radius of curvature equal to R _CV *, but reduced by the constant distance between the anterior partial surface (20) and the front side of the cornea (15). Method according to one of the above method claims, characterized in that the control data record is provided for a laser device (L) which adjusts the focused laser radiation (2) along a path (24) over the pattern of the target points (28), and that the control data record is such is generated that the target points (28) in the pattern represent a subset of the points (6) on which the laser device (L) emits the pulsed laser radiation (2). procedure after Claim 25 , characterized in that the control data record is provided for a laser device (L) which emits the pulses of the pulsed laser radiation (2) into the cornea (5) at a frequency f _P , and in that the control data record defines the pattern of the target points (28) in such a way includes that during operation of the treatment device, the target points (28) are specified with a frequency f _S that is lower than the frequency f _P . Computer program with program code which, when executed on a computer, carries out the method according to one of the above method claims. data medium with a computer program Claim 27 .

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