DE102024203961A1 - Devices and methods for generating control data with an optimized cutting geometry for marginal zone cuts during a correction of the refraction of an eye - Google Patents

Abstract

The present invention relates to a planning unit and a planning method, as well as to an ophthalmic laser therapy device for generating control data with an optimized cutting geometry for marginal zone cuts when correcting the refraction of an eye with a main optical axis and a cornea through corneal modification. The method comprises receiving data representing a refraction correction requirement, calculating a corneal tissue volume to be removed, and calculating cutting surface data, wherein the cutting surface data includes cap cutting data, lenticule cutting data, optionally lateral cutting data, and access cutting data. The present invention further relates to a computer program product, a data signal, a computer-readable non-volatile storage medium, and a therapeutic method for correcting the refraction of an eye.

Description

The present invention relates to a planning unit, an ophthalmological laser therapy device and a planning method for generating control data with an optimized cutting geometry for marginal zone cuts when correcting the refraction of an eye with a main optical axis and a cornea by corneal modification within the tissue.

The planning unit comprises a data processing device configured to receive data representing a need for refraction correction, to calculate a corneal tissue volume to be removed, the calculation being based on the need for refraction correction, and to calculate cutting surface data representing at least one cutting surface completely delimiting the tissue volume. The cutting surface data includes cap cutting data representing a cap cutting that delimits the tissue volume anteriorly, lenticule cutting data representing a lenticule cutting with a lenticule radius that delimits the tissue volume posteriorly, optionally lateral cutting data representing a lateral cutting that radially delimits the tissue volume circumferentially with respect to the main optical axis and that extends at least as far as the cap cutting and at least as far as the lenticule cutting, and access cutting data representing at least one access cutting. The present invention further relates to a computer program product, a data signal, a computer-readable non-volatile storage medium, and a therapeutic method for correcting the refraction of an eye.

Refractive errors in the human eye have long been corrected with supplementary lenses in the form of glasses or contact lenses. However, for more than 20 years, various approaches have been developed to correct refractive errors through modification of the cornea. The modification alters the curvature of the cornea and thus corrects the refractive power of the eye. This is achieved either by ablating a predetermined volume of a specific shape from the cornea or by removing tissue from the cornea. This alters the refractive power of the cornea in such a way that – taking into account the overall imaging properties of the eye – the refractive error is reduced or even completely eliminated.

To create the flat incisions in the cornea, pulsed laser radiation for treating the eye is focused within the tissue—i.e., below the surface of the tissue—in such a way that optical breakthroughs are created. This effect, known as photodisruption, is observed particularly with picosecond and femtosecond lasers, but also with nanosecond lasers (with shorter pulses, lower fluences [in mW/ ^cm² ] are necessary at the focus to create optical breakthroughs). Optical breakthroughs are also achieved in media transparent to the laser radiation. Typical (central) wavelengths of picosecond and femtosecond lasers can be around 800 nm, around 1030–1060 nm, around 1300 nm, around 1500 nm, or around 1900–2000 nm. Furthermore, the corresponding wavelength ranges at half, third, quarter, etc. wavelengths are accessible through frequency multiplication through nonlinear effects. For example, with an Nd:YAG laser at 1064 nm, pulsed laser light with a central wavelength of 532 nm can be achieved by frequency doubling, 355 nm by frequency tripling, and 266 nm by frequency quadrupling.

Various processes initiated by the laser radiation take place sequentially in the tissue. Multiphoton absorption generates a plasma, which expands through the absorption of further photons in an avalanche effect. If the power density of the radiation exceeds a threshold, an optical breakthrough occurs, creating a plasma bubble in the material. This plasma bubble grows after the optical breakthrough occurs 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. However, this process takes much longer than the formation of the bubble itself. For the sake of simplicity, the processes mentioned are summarized here under the term optical breakthrough, i.e., this term includes not only the actual optical breakthrough, but also the resulting effects in the material. If a large number of optical breakthroughs are created next to one another in the tissue, a flat cut (cut surface) can be created.

Laser-assisted refractive treatments have two major disadvantages: a) Damage to or severance of nerve fibers in the cornea and the associated, frequently occurring symptoms of dry eyes. b) The weakening of the stroma due to tissue removal or ablation and the treatment-specific incisions in the cornea, which can lead to ectasia or keratoconus.

Depending on the type of treatment, both points can be expressed to varying degrees.

When cutting a corneal flap with a specific thickness (typically 100 µm), the flap incision consists of a circular area with a lateral cut to the surface, which remains connected to the cornea only by a small arc (hinge, typically 3 mm). This severes nerve fibers along the entire circumferential lateral cut (a) and effectively weakens the tissue toward the surface in most of the flap (b).

An incision that defines a lenticule in the cornea of an eye (typically at a depth of 120 µm) typically has a cap incision (typically 8 mm diameter), a lenticule incision (typically 6 mm diameter), optionally a lateral incision, and an access incision (typically 2 mm). The cap incision is usually larger in diameter than the lenticule incision to ensure orientation for access to both incision planes and easier separation, but here the access incision is only made over the small arc area of the incision. This means fewer nerve fibers are severed (a) A remaining disadvantage of SMILE is the (slightly) weakened corneal tissue around the lenticule due to the larger cap incision. The cap incision is therefore comparable to a flap. The cap cut (also called cap cut or flap cut) limits the lenticule - the volume of tissue to be isolated from the cornea for removal - anteriorly, towards the front of the cornea. The lenticule cut limits the lenticule posteriorly - towards the retina of the eye. The lenticule cut can, for example, be created in a partial incision with a decreasing path radius (i.e. from the outside in) or with a increasing path radius (i.e. from the inside out). The optional side cut (also called side cut or lenticule side cut) limits the lenticule laterally opposite a main optical axis of the eye and extends both to the cap cut and to the lenticule cut. The access incision extends both to the cap cut and to the front of the cornea. The access incision can be used to remove the (isolated) tissue volume delimited in the cornea from the cornea.

It is also possible for the cap cut to taper towards the lenticule cut, or for the lenticule cut to taper towards the cap cut. It is therefore conceivable for the lenticule to have no edge cut, or alternatively, for a transition zone to be formed at the edge of the lenticule instead of a side cut.

Furthermore, the access incision serves as an access point for separating the lenticule, which is usually still connected to the surrounding corneal tissue by material bridges, from the areas of the cornea anterior to the lenticule and from the remaining area of corneal tissue posterior to the lenticule. This can be achieved, for example, using a spatula-shaped tool curved similar to the curve of an eye, which is inserted through the access incision and used to remove the material bridges.

Corneal nerves are damaged during all eye surgery.

The object of the present invention is therefore to provide devices and methods which make it possible to damage as few corneal nerves as possible during operations on the human eye.

According to the invention, the object is achieved by the features of the independent claims. Preferred developments and refinements are the subject of the dependent claims.

The cap section data, which are part of the cutting surface data calculated by the data processing device of the planning unit according to the invention, comprise cover surface section data representing a cover surface section with a cover surface radius, edge zone section data representing at least one edge zone section that borders the cover surface section in a predetermined azimuth angle range and has an edge zone radius that is greater than the cover surface radius, and edge zone segment section data representing at least one edge zone segment section for each edge zone section. The at least one edge zone segment section is arranged in a further azimuth angle range bordering the azimuth angle range of the edge zone section and, at an azimuth angle present both in the azimuth angle range and in the further azimuth angle range, merges into the edge zone section or borders it.

Furthermore, the data processing device is designed to provide control data representing the cutting surface, wherein the planning unit further comprises at least one input and/or output interface for receiving the data representing the refraction correction requirement and for providing the control data generated by the data processing device.

In addition, the invention relates to an ophthalmological laser therapy device as mentioned above, comprising a previously or subsequently described embodiment of the planning unit, a laser device for providing therapy radiation, a focusing device for focusing the therapy radiation in a focus for severing the cornea, a scanning device for shifting the focus of the therapy radiation within the tissue of the cornea of the eye to produce the cutting surface, and a control unit which is connected to the planning unit via the at least one input and/or output interface for receiving the control data, wherein the control unit is further connected to control the laser device and/or to control the focusing device and/or to control the scanning device.

The planning method according to the invention for generating control data is carried out in particular before and independently of an eye surgery to be performed. During this planning phase, no treatment or therapy of a patient is yet taking place. The control data represents where and/or in what order and/or with what parameters a laser pulse is to be applied to a patient's eye in order to correct the patient's refraction through corneal modification.

The planning method according to the invention for generating control data for correcting the refraction of a cornea of an eye having a main optical axis by corneal modification within the tissue by means of an ophthalmological laser therapy device comprises the steps of receiving correction data representing a refraction correction requirement, calculating a tissue volume of the cornea to be removed, wherein the calculation is carried out on the basis of the refraction correction requirement, calculating cutting surface data representing at least one cutting surface completely delimiting the tissue volume, wherein the cutting surface data comprise cap cutting data, lenticule cutting data, optionally lateral cutting data, and access cutting data.

Here, the cap cut data represent a cap cut that limits the tissue volume anteriorly, the lenticule cut data represent a lenticule cut with a lenticule radius, wherein the lenticule cut limits the tissue volume posteriorly, the optional side cut data represent an optional side cut that limits the tissue volume radially all the way around the main optical axis and that extends at least to the cap cut and at least to the lenticule cut, and the access cut data represent at least one access cut to the cap cut and to the lenticule cut.

• - Deckflächenschnittdaten, welche einen Deckflächenschnitt mit einem Deckflächenradius repräsentieren,
• - Randzonenschnittdaten, welche wenigstens einen Randzonenschnitt repräsentieren, welcher in einem vorbestimmten Azimut-Winkelbereich an den Deckflächenschnitt angrenzt, und einen Randzonenradius aufweist, der größer ist als der Deckflächenradius, und
• - Randzonensegmenschnittdaten, welche für jeden Randzonenschnitt wenigstens einen Randzonensegmentschnitt repräsentieren, wobei der wenigstens eine Randzonensegmentschnitt in einem an den Azimut-Winkelbereich des Randzonenschnittes angrenzenden weiteren Azimut-Winkelbereich angeordnet ist und bei einem sowohl im Azimut-Winkelbereich als auch im weiteren Azimut-Winkelbereich vorhandenen Azimutwinkel in den Randzonenschnitt übergeht oder an diesen angrenzt.

The cap cutting data also includes:

• - Cover surface section data, which represent a cover surface section with a cover surface radius,
• - edge zone section data representing at least one edge zone section which adjoins the cover surface section in a predetermined azimuth angle range and has an edge zone radius which is greater than the cover surface radius, and
• - Edge zone segment section data, which represent at least one edge zone segment section for each edge zone section, wherein the at least one edge zone segment section is arranged in a further azimuth angle range adjacent to the azimuth angle range of the edge zone section and merges into the edge zone section or borders on it at an azimuth angle present both in the azimuth angle range and in the further azimuth angle range.

Ultimately, the planning process generates control data representing the cutting surface.

In the following description, the optional enhancements to the control data are based on the patient's eye or cornea. This is to be understood as the theoretical location of the planned but not yet performed incisions in the patient's eye.

The need for refractive correction can be determined through previous measurements of the patient's eye and represented by correction data. This correction data is used to calculate the volume of corneal tissue to be removed using the planning procedure. Various objective and subjective measurements are known to determine the need for refractive correction, and these can be combined. Measurements of the structure of the eye, for example, via an OCT measurement, as well as measurements of intraocular pressure and the topography of the eye, can also be incorporated into the refractive correction requirement.

The tissue volume is delimited or defined by cutting surfaces. These cutting surfaces are represented by the calculated cutting surface data.

As previously described, the tissue volume (i.e., the lenticule) is composed of different cut surfaces. Each of these cut surfaces is represented by corresponding cut surface data, for example, the cap cut data, which represents a cap cut that delimits the tissue volume anteriorly, the lenticule cut data, which represents a Represent a lenticule cut that delimits the tissue volume posteriorly, the optional lateral cut data that represent an optional lateral cut that delimits the tissue volume radially at least in sections with respect to the main optical axis and that extends in sections at least as far as the cap cut and at least as far as the lenticule cut, and the access cut data that represent at least one access cut.

The cap incision is thus adapted and its area reduced compared to a conventional SMILE operation in order to minimize damage to the nerve fibers and weakening of the corneal tissue. For this purpose, the previously circular cap incision with a diameter that can, for example, correspond to twice the marginal zone radius) is significantly larger than the underlying lenticule incision, is divided into several partial incision areas. Furthermore, the area of the cap incision that extends beyond the lenticule incision can be referred to as the clearance. The cap incision can extend beyond the lenticule incision by a clearance distance. According to the invention, areas of the clearance can be masked in the control data, whereby masking is understood to mean "no cutting" or is implemented when the control data is executed. In this way, incision areas can be omitted.

It is advantageous if the cover surface cut is arranged along the main optical axis essentially concentrically above the lenticule cut.

Such an adapted geometry of the cap incision minimizes the area of the cap incision without sacrificing the advantage of easier orientation/separability provided by an existing transition zone of the marginal zone incision. The cap incision is aligned to the position of the access incision by the marginal zone incision.

Due to the reduced surface area, fewer nerves are severed and the biomechanical stability of the cornea after treatment is improved due to a comparatively smaller weakening of the tissue (the biomechanical stability is less reduced by the procedure).

It is also advantageous if the edge zone cut extends in the direction of the access cut in the form of a circular segment, wherein the edge zone cut can have an edge zone radius which is substantially 0.5 to 1.3 mm larger than the lenticule radius, preferably substantially 0.6 to 1.2 mm larger than the lenticule radius, more preferably substantially 0.7 to 1.1 mm larger than the lenticule radius and even more preferably substantially 0.9 mm larger than the lenticule radius.

For each access incision (there is at least one), there is a circular ring segment adjacent to the top surface incision in the direction of the access incision with a specific radial length D (also parameter D), which corresponds to the difference between the marginal zone radius and the lenticule radius. This radial length D can, in particular, correspond to a clearance length of a known SMILE procedure. However, according to the invention, such a marginal zone incision or such a clearance region with radial length D is only provided within the azimuth angle range.

Furthermore, it is advantageous if the access incision and the marginal zone incision have different inclination angles relative to the main optical axis in the radial direction. The access incision represents a cut surface or surface incision that extends from the marginal zone incision to the anterior surface of the cornea or that is applied to the anterior surface of the cornea.

Furthermore, the edge zone section can essentially be continuously adjacent to the cover surface section or can continuously merge into it.

Preferably, the cover surface radius is greater than the lenticule radius by a clearance distance, wherein the clearance distance is <0.5 mm, preferably <0.4 mm, more preferably <0.3 mm, even more preferably <0.2 mm, and even more preferably less than or equal to 0.1 mm. The clearance distance can also be referred to as parameter A.

The cover surface radius can be larger than the lenticule radius by the clearance distance, particularly in an angular range outside the azimuth angle range of the edge zone cut. This angular range can thus essentially be (360° - azimuth angle range). In the azimuth angle range, the cover surface radius can be larger than the lenticule radius by the parameter D due to the edge zone cut.

The clearance can be understood in particular as a safety feature, since it ensures an overlap or abutment of the lenticule surfaces perforated by the laser even in the case of a slight offset between the lenticule cut and the cap cut, and thus separation is always possible along the surfaces processed by the laser, even in the case of such an offset.

In an advantageous embodiment, the access incision and the at least one marginal zone incision can have substantially the same azimuth angle range, whereby the access incision can extend from the anterior surface of the cornea to the marginal zone incision, and the marginal zone incision can extend to the top surface incision. One access incision can be provided for each marginal zone incision.

The additional azimuth angle range of the at least one edge zone segment cut can be referred to as parameter C and increases the azimuth angle range of the edge zone cut. The resulting higher angle range can provide greater freedom of movement when separating the cutting planes using the typically performed wiping motion.

A marginal zone segment incision preferably borders on or merges with the marginal zone incision at an azimuth angle. The marginal zone segment incision thus enlarges the marginal zone incision, but not the access incision. In other words, an access opening is smaller (i.e., an incision is shorter) than a subsequent access tunnel, allowing for increased mobility within the access tunnel.

The improvement in the incision geometry thus particularly affects the cap incision. The lenticule incision remains essentially unchanged, whereas the cap incision has a second clearance distance (also: parameter A) of the clearance area, which is significantly reduced. Only in the azimuth angle range (also: parameter B) of the access incision is the original clearance distance (also: parameter D) retained. Access via the access incision to the cap incision is thus unchanged, whereas in a recessed angular range of 360° minus the azimuth angle range, a significantly smaller area must be incised.

It may be advantageous if two edge zone segment cuts are provided symmetrically for increasing and decreasing azimuth angles, i.e. both in and against an azimuthal direction at the edge zone cut.

This means that a marginal zone segment cut is provided on both sides of the at least one marginal zone cut. This increases the physician's freedom of movement when separating the planes in both directions.

A marginal zone segment incision can be essentially triangular, essentially rectangular, or essentially triangular with a curved triangular side. This facilitates access with the tool to any point of the lenticule marginal incision. A curved triangular side, in particular, can contribute to increased stability of the incision, as it is less susceptible to stretching and the cornea is less likely to be overstretched at this location. Tensions in the tissue during stretching or compression are thus better distributed into the surrounding tissue.

In some embodiments of the at least one edge zone segment cut, the original clearance distance (parameter D) can be retained. This can be the case, in particular, with substantially rectangular edge zone segment cuts. Furthermore, the clearance distance prevailing in the at least one edge zone segment cut can vary depending on the azimuth angle between the original clearance distance (parameter D) and the second clearance distance (parameter A). In particular, the clearance distance prevailing in the at least one edge zone segment cut can change continuously depending on the azimuth angle. An edge cut delimiting the at least one edge zone segment cut can thus particularly preferably be continuously curved and/or transition continuously into the remaining clearance outside the azimuth angle range and outside the further azimuth angle range. Such a continuous transition can reduce the risk of unwanted and uncontrolled tearing of corneal tissue, since tensions in the tissue can be better distributed by a curved incision or a curved cutting edge that limits a marginal zone segment incision.

The device for data processing of the planning unit can thus be designed to calculate the access intersection data in such a way that the aforementioned at least one edge zone segment intersection, as well as further configurations of the edge zone segment intersection(s), are represented by the access intersection data.

It is further advantageous if the two edge zone segment cuts have boundary cutting lines arranged parallel to each other.

In a further embodiment, the azimuth angle range of the marginal zone incision can be between 20° and 40°, preferably between 25° and 35°, more preferably essentially approximately 30°. Depending on the surgeon's experience or the expected difficulty of lenticule extraction, the width of the access to the lenticule can thus be adjusted.

Furthermore, it is advantageous if a central azimuth angle of the azimuth angle range between 0° and 360° can be set.

The position of the access incision must also be adjusted accordingly. For example, the position of the access for plane separation and/or lenticule extraction can be adjusted based on operating room conditions, the surgeon's handedness (left-handed, right-handed), or the surgeon's preference. Optionally, the cap section data can include two marginal zone sections with correspondingly identical or different marginal zone element sections. If, for example, separation or extraction through the first marginal zone section leads to complications, this can be performed through the second marginal zone section.

The planning unit and the planning process can be further improved by increasing the azimuth angle range to between 1.5° and 15°, preferably between 0.75° and 7.5°. This wider angle range also allows for greater freedom of movement when separating the section planes using the typically performed swiping motion.

• - das Einlesen oder Berechnen von Start-Steuerdaten, welche wenigstens eine Schnittfläche sowie deren dreidimensionale Lage und Orientierung in der Kornea des Auges repräsentieren;
• - das Einlesen von Nervendaten, welche eine dreidimensionale Anordnung und einen dreidimensionalen Verlauf und eine Dicke von Nerven in der Kornea eines Auges repräsentieren;
• - das Erzeugen eines Gewichtungswertes aus den Start-Steuerdaten und aus den Nervendaten durch Anwenden einer Penalty- und/oder Merit-Funktion auf die Anzahl und/oder Art und/oder Abschnittlänge der mit der wenigstens einen Schnittfläche überlappenden, durch die Nervendaten repräsentierten Nerven, wobei der Gewichtungswert einen Schweregrad der Überlappung repräsentiert; und
• - das Bereitstellen des Gewichtungswertes.

In a further embodiment of the planning method, this may further comprise method steps of a computer-implemented method for optimising control data, wherein the computer-implemented method comprises:

• - reading in or calculating start control data which represent at least one cutting surface and its three-dimensional position and orientation in the cornea of the eye;
• - reading nerve data representing a three-dimensional arrangement, course and thickness of nerves in the cornea of an eye;
• - generating a weighting value from the starting control data and from the nerve data by applying a penalty and/or merit function to the number and/or type and/or section length of the nerves represented by the nerve data overlapping with the at least one section surface, wherein the weighting value represents a degree of severity of the overlap; and
• - providing the weighting value.

The weighting value can be understood as a factor for the severity of the overlap between the structure to be created in the cornea (cut surface) and the corneal nerves. It is conceivable that the weighting value will be further processed and/or prepared and/or, in particular, transmitted to a user, thus enabling an assessment of the severity of nerve damage to the corneal nerves during the planned procedure.

The weighting value can be provided optically, e.g., via a display device, or acoustically. One possible solution is a light source that changes the displayed color depending on a comparison of the determined weighting value with a predetermined ideal weighting value. A specific display of the weighting value, possibly coupled with a color coding as described above, on a display device is also conceivable. Thus, the provided weighting value can be used to estimate how invasive—i.e., how damaging—the planned procedure will be for the corneal nerves right from the planning stage.

In a further embodiment, the planning unit therefore allows at least one start parameter stored in the start control data to be modified by means of at least one user input. Following a modification, a recalculated weighting value can be displayed. The user input can be made via keyboard, mouse, touchscreen, voice input, or otherwise. Furthermore, a modification of multiple parameters is conceivable. Furthermore, in such a modification, parameters can be linked to one another, so that an increase in a first parameter causes a decrease in a second parameter. The provision of the weighting value allows a user to reduce the severity of the overlap, i.e., the invasiveness of the procedure, and to protect the corneal nerves of the eye being treated by modifying at least one parameter during the planning stage. This reduces the likelihood of complications and increases patient satisfaction.

The data processing device of the aforementioned embodiments can also be configured to provide the start control data as control data without changing the parameters. Likewise, the data processing device can provide control data based on the start control data and the parameters set by the user.

In a further embodiment of the computer-implemented method, the weighting value is optimized in a further method step by repeatedly generating it from the nerve data and from subsequent control data, which in a first iteration starting from from the initial control data and, in subsequent iterations, from previously generated follow-up control data by modifying at least one start parameter stored in the initial control data. Furthermore, the follow-up control data that results in the optimized weighting value are provided as optimized control data.

A previously described manual or semi-automatic or automatic optimization of the control data by modifying the at least one start parameter can be carried out following a modification of at least one parameter by means of user input.

Even with automatic optimization of the control data, the decision as to whether the procedure is performed using the optimized control data obtained remains with the physician. The method and the devices presented are designed to enable verification of the optimized control data, for example by visualizing the changed parameter sets and/or purely by way of example by comparing the position of the incisions to be performed with the start control data and the optimized control data. With this visualization, a property of the visualization can also be dependent on the determined weighting value or depending on a standardized weighting value. Purely by way of example and not by way of limitation, elements inside or outside the visualized position of the incisions can be color-coded or highlighted using a type of traffic light system.

In this optimized planning method, the start control data can comprise at least one predetermined parameter set of start parameters, a position of the access cut and/or a cover surface radius and/or an edge zone radius and/or an azimuth angle range and/or a further azimuth angle range and/or a clearance distance.

For example, a physician can vary the azimuthal position of the marginal zone incision and/or the position and/or shape and/or number of marginal zone segment incisions, for example, within a quadrant favorable for the procedure, and specify/set an azimuth angle in the planning phase that has a lower weighting value. It is also conceivable that a range of values (e.g., the quadrant mentioned above) can be specified as the limits of the azimuth angle to be set, and (automatic) optimization should only occur within this quadrant.

Furthermore, it is conceivable that a lenticule depth and/or a lenticule height and/or a position of the access cut and/or a course of the cap cut and/or a course of the lenticule cut and/or a course of the edge cut and/or a course of a transition zone and/or a lenticule radius and/or a cover surface radius are also manually or semi-automatically or fully automatically variable as parameters.

It is possible that each start parameter can only be modified within a parameter interval specific to each parameter stored in the start control data.

Furthermore, it is advantageous if at least one start parameter can be set invariably as a fixed value.

A further improvement of the planning procedure is achieved when the nerve data represents a measurement from a high-resolution OCT and/or a measurement from a confocal microscope.

In particular, the measurement represented by the nerve data may have a resolution of 5 µm or less.

The nerve data can represent the nerves of the eye for which the control data for the intervention is being generated. It is also conceivable that general nerve data, e.g., from measurements on patients and/or test subjects, could be used. This nerve data then does not exactly represent the nerves of the eye to be treated, for which the control data is to be generated, but can serve as an aid in determining how damaging the planned intervention will be to the nerves. Furthermore, it is also possible that the nerve data merely comprises model data, which may be simulated and not based on a real measurement on an eye.

• - ein Verästelungsindex einzelner von den Nervendaten repräsentierter Nerven berücksichtigt wird, wobei der Verästelungsindex wenigstens eine Anzahl an Verzweigungen nach dem Schnitt von Nerven repräsentiert; und/oder
• - eine Dickeninformationen einzelner von den Nervendaten repräsentierter Nerven berücksichtigt wird, wobei die Dickeninformation wenigstens eine Dicke der Nerven repräsentiert; und/oder
• - eine Restlängeninformation berücksichtigt wird, wobei die Restlängeninformation wenigstens eine gesamte Länge der von den Nervendaten repräsentierten, abgeschnittenen Nerven repräsentiert.

Furthermore, it is advantageous if, when generating the weighting value

• - a branching index of individual nerves represented by the nerve data is taken into account, wherein the branching index represents at least a number of branches after the cutting of nerves; and/or
• - thickness information of individual nerves represented by the nerve data is taken into account, wherein the thickness information represents at least one thickness of the nerves; and/or
• - residual length information is taken into account, wherein the residual length information represents at least a total length of the cut nerves represented by the nerve data.

The planning unit according to the invention but also the ophthalmological laser therapy device according to the invention can be designed to carry out an embodiment of the planning method which comprises method steps of the computer-implemented method described above.

The invention further relates to a computer program product comprising instructions which, when loaded into a data processing device, cause the device to carry out an embodiment of the planning method described above.

The invention further relates to a data signal which transmits the aforementioned computer program product.

Furthermore, the invention relates to a computer-readable non-volatile storage medium comprising the computer program product described above.

• - Durchführen einer Ausgestaltung des vorab beschriebenen Planungsverfahrens;
• - Schneiden der Hornhaut des Auges gemäß den bereitgestellten Steuerdaten;
• - Lösen des Gewebevolumens entlang des Kappenschnittes durch den Zugangsschnitt;
• - Lösen des Gewebevolumens entlang des Lentikelschnittes durch den Zugangsschnitt;
• - Lösen des Gewebevolumens entlang des Seitenschnittes; und
• - entnehmen des Gewebevolumens aus der Hornhaut des Auges durch den Zugangsschnitt.

Finally, the invention relates to a method for correcting the refraction of an eye by corneal modification within the tissue, comprising

• - Implementation of the planning procedure described above;
• - Cutting the cornea of the eye according to the provided control data;
• - Release of the tissue volume along the cap incision through the access incision;
• - Release of the tissue volume along the lenticule incision through the access incision;
• - Release of the tissue volume along the lateral incision; and
• - removing the tissue volume from the cornea of the eye through the access incision.

Below, some computational examples and advantages of the invention are presented. These are purely exemplary and not limiting.

The cap incision is adapted to the position of the incision, thus minimizing the effective area. Typically, the optical zone (OZ) has a diameter of approximately 6 mm, which, with a transition zone of 0.1 mm, results in a lenticule diameter of 6.2 mm. This corresponds to a projected area of 30.2 ^mm² . A cap incision typically has a diameter of 8 mm with an access incision that has an azimuth angle range of 29° (or 2 mm). The clearance (clearance distance) is thus 0.9 mm and the projected cap area is 50.3 ^mm² . The cap incision is therefore approximately 20.1 ^mm² larger than the lenticule incision (approximately 66%).

In the adapted cutting geometry, the cap cut is extended by only 0.1 mm radially beyond the lenticule diameter (parameter A or clearance distance). In addition, a circular ring segment (the marginal zone cut) with a radial length D of 0.8 mm is created (to effectively place the access cut back to a diameter of 8 mm). The angular range of the marginal zone cut corresponds to the access cut (parameter B; 29° or 2 mm) extended (by one or two marginal zone segment cuts) by 1.5° (or 0.1 mm) angular extension each (parameter C). The area of the ring segment is thus approximately 1.6 ^mm² and the total cap area 33.8 ^mm² . This corresponds to an area saving of 16.5 ^mm² or 33% compared to the total area of the cap in a regular SMILE. If one considers only the area that exceeds the lenticule area of 30.2 mm ² , the saving is even 82%.

With the same access incision length (2 mm) and an (effective) cap diameter of 7.5 mm, the savings decrease to approximately 25% (78% outside the lenticule area). With an (effective) cap diameter of 8.5 mm, the savings increase to approximately 40% (85% outside the lenticule area).

The function of the suggested adjustable geometry can be deactivated in the ophthalmic therapy device to return to the regular SMILE. For example, the parameters relevant for an adjusted cap cut are grayed out in the planning software, and the cap cut is displayed as normal, circular and concentric to the lenticule. A planning screen allows easy switching between the adjusted cap cut ("masked clearance") and the regular cap cut. A display can show the area difference or the saved area between the adjusted and regular cap cut (relative, e.g., in %, or absolute, e.g., in ^mm² ).

The new cut design can be displayed as a sketch to facilitate adjustment of the parameters (A, B, C, D). In addition to selecting the cut geometry, additional relevant adjustment parameters can be displayed or irrelevant parameters can be grayed out, as described above.

Through additional diagnostics (e.g. confocal microscopy or OCT) and the associated knowledge about the position and course of the nerve fibers The position and width of the ring segment and the access incision can be adjusted to minimize nerve damage as much as possible. This is described above in the computer-implemented procedure.

If diagnostic data on the course of the nerve fibers or the position of other tissue regions to be protected are available, the planning unit or the ophthalmic therapy device can optionally automatically make and/or visualize a suggestion for a specific incision geometry with correspondingly preselected parameters in order to support the physician in planning with the least possible nerve damage.

Since the area of the cap incision is limited to the width of the access incision (parameter C ∼ 0), the tissue on both sides of the access incision remains uncut within the clearance zone. This contributes to increased stability. The cap incision can be stretched less, and the cornea at this position can be overstretched less.

In addition, the stability of the access incision itself is increased. By eliminating the cap incision (since the clearance distance is preferably only 0.1 mm) on either side of the access incision (parameter C ∼ 0), the risk of tearing of the access incision is reduced.

By reducing the amount of cut tissue, the effective length of the access tunnel (parameter D) can be increased compared to regular SMILE. This facilitates plane identification during manual lenticule extraction, as the edge of the cap cut and the edge of the lenticule cut are clearly distinguishable. Furthermore, within a long and laterally limited access tunnel, the separating tool can be guided along the natural curvature of the cornea. The probability of initially penetrating the anterior cap cut plane at the edge of the lenticule cut as desired is increased, and the risk of inadvertently separating the lenticule cut plane is reduced.

By maintaining only a slight difference in the diameter of the cap cut and the lenticule (low clearance, parameter A), the stability of a cap area above (i.e., anterior to) the lenticule is increased and offset of the two curves is reduced. This can reduce the risk of wrinkle formation ("microfolds" or "Bowman wrinkles"), which can have a positive effect on the patient's visual recovery.

The aspects of the present invention will be explained in more detail below with reference to the accompanying drawings. The drawings show possible exemplary embodiments of the present invention purely by way of example, whereby the described features can be combined with one another or omitted as desired. Identical features or features with the same function are also identified by the same reference numerals. Repetitive descriptions of features are omitted, so that explanations of features described in previous drawings can also be applied to other drawings, unless differences are explicitly pointed out.

• 1 eine schematische Darstellung der ophthalmologischen Lasertherapievorrichtung;
• 2 und 3 schematische Darstellungen des Effektes durchgeführter Schnitte auf Nervenfasern;
• 4 eine schematische Darstellung einer bekannten Schnittgeometrie bei einer SMILE Operation;
• 5 eine schematische Darstellung einer verbesserten Schnittgeometrie;
• 6-9 schematische Darstellungen verbesserter Schnittgeometrie mit unterschiedlichen Randzonensegmentschnitten; und
• 10eine schematische Darstellung einer ophthalmologischen Lasertherapievorrichtung.

They show:

• 1 a schematic representation of the ophthalmic laser therapy device;
• 2 and 3 schematic representations of the effect of cuts on nerve fibers;
• 4 a schematic representation of a known incision geometry in a SMILE operation;
• 5 a schematic representation of an improved cutting geometry;
• 6-9 schematic representations of improved cutting geometry with different edge zone segment cuts; and
• 10one schematic representation of an ophthalmic laser therapy device.

In the 1 An ophthalmological laser therapy device 1 and a focusing device 3 of the ophthalmological therapy device 1 are shown schematically. The ophthalmological laser therapy device 1 generates therapy radiation 5, which is generated by a laser device not shown (see 11 ). The therapeutic radiation 5 is focused by the focusing device 3 into a focus 7, where photodisruption 9 occurs. An eye 13 is schematically shown in a treatment area 11. The eye 13 has a cornea 15, which is shown here in a highly simplified manner. The cornea is bounded anteriorly by a surface 17 and posteriorly by a rear surface 19.

Furthermore, a tissue volume 21 to be removed from the cornea 15 is shown schematically, which can also be referred to as a lenticule 23. The indicated tissue volume 21 has not yet been removed from the cornea 15, but is present as a tissue volume 21 represented by planning data. The following explanations of the tissue volume 21 and Sections or sections forming these are shown merely to illustrate a schematic position on or in the eye. The drawn sections or the area surrounding the drawn tissue volume 21 are represented by the control data 90 before the actual treatment of the eye 13.

The tissue volume 21 is defined by several cut surfaces 25 (only one is shown here). Furthermore, the eye 13 has a main optical axis 27.

In the 2 and 3 is schematically the cornea 15 of an eye 13 in the case of cutting a flap 29 ( 2 ) or for a SMILE operation ( 3 ) are shown. Also shown are nerves 50, where in 2 Both nerves 50 shown are cut by the cap incision 29 as well as the edge incision 33 and thus damaged. In the case of a 3 In the SMILE operation shown, only one nerve fiber 50 is cut and damaged. 3 Likewise, a clearance area 51 of a conventional SMILE operation cuts the second nerve fiber 50.

In the 4 A top view of the incisions to be made in eye 13 is shown schematically. A cutting pattern familiar from conventional SMILE surgery is shown.

The cap cut 29 has a cap radius 53 (also edge zone radius 53) which is significantly larger than a lenticule radius 55 of the lenticule cut 31. The difference between the two radii 53, 55 is referred to as clearance distance 57.

An access cut 35 extends over an azimuth angle range 59, whereby access to the cap cut 29 is possible via the access cut 35 via the clearance area 51.

In the 5 The inventive improvement in the cutting geometry is shown. It can be seen that the lenticule cut 31 is unchanged, but the cap cut 29 has a second clearance distance 57a (also: parameter A) of the clearance area 51, which is significantly reduced. Only in the azimuth angle range 59 (also: parameter B) of the access cut 35 is the original clearance distance 57 (also: parameter D) retained. Access via the access cut 35 to the cap cut 29 is thus possible without any changes, whereas in a recessed angle range 61, a significantly smaller area must be cut.

With reference to 3 Thus, the nerve fibers 50 cut in the clearance area 51 can be kept intact if necessary.

The lenticule radius 55 and the clearance distance A together result in a cover surface radius 63 which is smaller than an edge zone radius 65, which corresponds to the cap radius 53.

Furthermore, two hatched edge zone segment sections 67 are shown. The two edge zone segment sections 67 are identical in the example shown and extend into a first further azimuth angle range 69 and a second further azimuth angle range 71, respectively. The further azimuth angle ranges 69, 71 directly adjoin the azimuth angle range 59, but the access section 35 does not extend into them.

The azimuth angle range 59 has a first azimuth angle 69A in common with the first further azimuth angle range 69 and a second azimuth angle 71A in common with the second further azimuth angle range 71.

The 6 to 9 each schematically show different designs of the edge zone segment cuts 67. For the sake of clarity, only the most necessary reference symbols are shown.

In the 6 the edge zone segment cuts 67 are rectangular 73, in the 7 and 8 These are triangular 75 and in the 9 These are essentially triangular 75 with a curved side surface 77. The different geometries of the marginal zone segment cuts 67 allow unhindered access to both the cap cut 29 and the lenticule cut 31, whereby the access should generally allow a wiping motion to sever the remaining material bridges of the corresponding cuts.

In 10 An embodiment of an ophthalmic laser therapy device 1 is schematically shown. During operation of the ophthalmic laser therapy device 1, a laser device 110 emits therapy light 5 in the form of a pulsed laser beam 115. The laser beam 115 is deflected laterally (in the x and y directions) by a scanning device 130 and axially (z direction) by another scanning device 135. In other embodiments, the laser beam 115 can first be adjusted in the z direction by the other scanning device 135 and subsequently deflected laterally in the x and y directions by the scanning device 130.

A focusing device 3 focuses the pulsed laser beam 115 in a focus 7 in the Cornea 15. In 6 Focus 7 is shown as an example for two positions in the cornea 15 for different settings of the lateral scanning device 130 and the axial scanning device 135. A potentially advantageous fixation of the eye by means of a patient interface relative to the ophthalmic laser therapy device 1 is not shown.

During operation, the laser device 110, the scanning devices 130, 135, and the focusing device 3 are controlled fully automatically via signal data transmitted from a control unit 140 to the respective devices 110, 113, 130, 135. This is indicated by arrows pointing from the control unit 140 to the devices 110, 113, 130, and 135, respectively. The control unit 140 ensures suitably synchronous operation of the laser device 110, the three-dimensional scanning devices 130, 135, and, if applicable, the focusing device 3. The signal data can be transmitted via signal data lines 80 or wirelessly. The signal data required during operation is determined in the control unit 140 based on the control data 90. The control data 90 is received by the control unit 140 beforehand from the planning unit P as a control data set 92 via unspecified communication paths such as control lines 94 (in 6 shown as a solid line between the planning unit P and the control unit 140). The control data 90 can also be transmitted using memory chips 96 (e.g., via USB or memory stick), magnetic storage devices 98 (e.g., floppy disks), wirelessly via radio (e.g., WLAN, UMTS, Bluetooth), or wired (e.g., USB, Firewire, RS232, CAN bus, Ethernet, etc.). As an alternative to direct communication, it is also possible to arrange the planning device P spatially separate from the control unit 140 and to provide a corresponding data transmission channel. The transmission preferably takes place before the operation of the ophthalmological laser therapy device 1, i.e., before control signals are transmitted to the laser device 110, the scanning devices 130, 135, and, if applicable, to the focusing device 3.

The control data set 92 is transmitted to the control unit 140 of the ophthalmic laser therapy device 100 via an input and/or output interface S2 of the planning device P.

The control data 90 represents, on the one hand, the various cuts, such as the cap cut 29, the lenticule cut 31, the optional edge cut 33, as well as the first access cut 35, the second access cut 41, and (the side surface segment 71) or (in another embodiment, the first side surface segment 71 and the second side surface segment 73), as well as the modifications of the processing parameters P to be applied in these side surface segments. Preferably, operation of the ophthalmic laser therapy device 1 is blocked until a valid control data set 92 is present at the control unit 140. A valid control data set 92 can be a control data set 92 that is, in principle, suitable for use with the control unit 140 of the ophthalmic laser therapy device 1. In addition, validity can also be linked to the passing of further tests. For this purpose, it can be checked, for example, whether additional information stored in the control data record 92 about the ophthalmic laser therapy device 100, e.g., a device serial number 90a, or about the patient, e.g., a patient identification number 90b, matches other information that was, for example, read out on the ophthalmic laser therapy device 1 or entered separately as soon as the patient is in the correct position for operation of the ophthalmic laser therapy device 1.

The planning device P generates the control data 90 or the control data set 92, which is provided to the control unit 140 of the ophthalmic laser therapy device 1 for carrying out the surgical procedure. In the embodiment shown here, the refraction correction requirement R is input via an input device (not shown) and provided to the planning unit P via a first interface S1. In other embodiments, the refraction correction requirement R can also be input via the input and/or output interface S2. Furthermore, the start control data 200 and the nerve data 210 can also be input via these interfaces.

The input device can be part of the ophthalmological laser therapy device 1 or can be designed independently.

The planning unit P comprises a calculation device C. This is connected to the first interface S1 and receives the refraction correction requirement R of the eye and, if applicable, the start control data 200 and the nerve data 210. In the calculation device C, control data 90 for correcting the refraction of the eye 13 by means of corneal modification are then calculated.

Alternatively, in the calculation device C, subsequent control data 201 are calculated by optimization and those subsequent control data 201 are output as optimized control data 203, which result in the optimized weighting value W.

The control data 90 are transmitted to the control unit via the input and/or output interface S2. unit 140. Using the transmitted control data 90, the control unit 140 can generate signal data S1, S2, S3 and transmit them to the devices 110, 113, 130, 135, so that a cut surface can be created in the cornea 15 of the eye 13.

Optionally, the optimized control data 203 are transmitted to the control unit 140 via the input and/or output interface S2. Using the transmitted optimized control data 203, the control unit 140 can generate signal data S1, S2, S3 and transmit them to the devices 110, 113, 130, 135, so that a cut surface can be created in the cornea 15 of the eye 13 according to the optimized control data 203. With this cut surface, it may be possible for fewer nerves to be damaged than when using the control data 90 without optimization.

It should be noted again that the planning unit P can generate the control data 90 or the optimized control data 203 regardless of whether the eye 13 is connected to the ophthalmic laser therapy device 1 or not.

Claims (18)

A planning unit for generating control data for correcting the refraction of a cornea of an eye having a main optical axis by corneal modification within the tissue using an ophthalmic laser therapy device, wherein the planning unit comprises: - a data processing device configured to: ◯ receive correction data representing a refractive correction requirement; ◯ calculate a corneal tissue volume to be removed, wherein the calculation is based on the refractive correction requirement; ◯ calculate cutting surface data representing at least one cutting surface completely surrounding the tissue volume, wherein the cutting surface data comprises cap cutting data, lenticule cutting data, optionally lateral cutting data, and access cutting data, wherein the cap cutting data comprises: ▪ top cutting data representing a top cutting surface with a top cutting surface radius; ▪ marginal zone cutting data representing at least one marginal zone cutting that borders the top cutting surface within a predetermined azimuth angle range; and has an edge zone radius that is greater than the cover surface radius, and ▪ comprise edge zone segment section data that represent at least one edge zone segment section for each edge zone section, wherein the at least one edge zone segment section is arranged in a further azimuth angle range adjacent to the azimuth angle range of the edge zone section and merges into the edge zone section or borders it at an azimuth angle present both in the azimuth angle range and in the further azimuth angle range, and ◯ provide control data representing the cut surface, wherein the planning unit further comprises at least one input and/or output interface for receiving the data representing the refraction correction requirement and for providing the control data generated by the data processing device. Planning unit according to Claim 1 , wherein the data processing device is designed to calculate the access cut data in such a way that two edge zone segment cuts are provided symmetrically for increasing and for decreasing azimuth angles, ie both in and against an azimuthal direction adjacent to the edge zone cut. Planning unit according to Claim 1 or 2 , wherein the data processing device is designed to calculate the access cut data such that at least one edge zone segment cut has a shape which is - substantially triangular; - substantially rectangular; or - substantially triangular with a curved triangular side. Planning unit according to Claim 2 , wherein the data processing device is designed to calculate the access cutting data in such a way that the two edge zone segment cuts have boundary cutting lines arranged parallel to one another. Planning unit according to one of the Claims 1 until 4 , wherein the data processing device is designed to calculate the access cut data in such a way that - the azimuth angle range of the edge zone cut is between 20° and 40°, preferably between 25° and 35°, more preferably substantially approximately 30°; and/or - that a central azimuth angle of the azimuth angle range can be set between 0° and 360°. Planning unit according to one of the Claims 1 until 5 , wherein the data processing device is designed to calculate the access cutting data such that the further azimuth angle range is between 1.5° and 15°, preferably between 0.75° and 7.5°. Ophthalmological laser therapy device, comprising - a planning unit according to one of the Claims 1 until 6 , - a laser device for providing therapeutic radiation, - a focusing device for focusing the therapeutic radiation in a focus for severing the cornea within the tissue of the cornea, - a scanning device for shifting the focus of the therapeutic radiation in the cornea of the eye to create the cutting surface, and - a control unit which is connected to the planning unit via the at least one input and/or output interface for receiving the control data, wherein the control unit is further connected to control the laser device and/or to control the focusing device and/or to control the scanning device. Ophthalmological laser therapy device according to Claim 7 , comprising a femtosecond laser or a picosecond laser for providing pulsed therapeutic radiation. A planning method for generating control data for correcting the refraction of a cornea of an eye having a main optical axis by corneal modification within the corneal tissue using an ophthalmic laser therapy device, comprising: - receiving correction data representing a refractive correction requirement, - calculating a corneal tissue volume to be removed, wherein the calculation is based on the refractive correction requirement, - calculating cut surface data representing at least one cut surface completely delimiting the tissue volume, wherein the cut surface data comprises: ◯ cap cut data representing a cap cut that delimits the tissue volume anteriorly, ◯ lenticule cut data representing a lenticule cut with a lenticule radius, wherein the lenticule cut delimits the tissue volume posteriorly, ◯ optional lateral cut data representing an optional lateral cut that radially delimits the tissue volume circumferentially with respect to the main optical axis and that extends at least to the cap cut and at least to the lenticule cut extends, and ◯ access section data representing at least one access section to the cap section and the lenticule section, wherein the cap section data comprises: - cover surface section data representing a cover surface section with a cover surface radius, - edge zone section data representing at least one edge zone section that borders the cover surface section in a predetermined azimuth angle range and has an edge zone radius that is greater than the cover surface radius, and - edge zone segment section data representing at least one edge zone segment section for each edge zone section, wherein the at least one edge zone segment section is arranged in a further azimuth angle range bordering the azimuth angle range of the edge zone section and merges into the edge zone section or borders it at an azimuth angle present in both the azimuth angle range and the further azimuth angle range, and - generating control data representing the cut surface. Planning procedures according to Claim 9 , further comprising method steps of a computer-implemented method for optimizing control data, comprising - reading in or calculating start control data which represent at least one cutting surface and its three-dimensional position and/or orientation in the cornea of the eye; - reading in nerve data which represent a three-dimensional arrangement and/or a three-dimensional course and/or a thickness of nerves in the cornea of an eye; - generating a weighting value from the start control data and from the nerve data by applying a penalty and/or merit function to the number and/or type and/or section length of the nerves represented by the nerve data which overlap with the at least one cutting surface, wherein the weighting value represents a degree of severity of the overlap; and - providing the weighting value. Planning procedures according to Claim 10 , further comprising: - optimizing the weighting value by repeatedly generating it from the neural data and from follow-up control data, which are generated in a first iteration starting from the start control data and in subsequent iterations starting from previously generated follow-up control data by modifying at least one start parameter stored in the start control data; - providing those follow-up control data as optimized control data, which result in the optimized weighting value. Planning procedures according to Claim 10 or 11 , wherein the start control data comprises at least one predetermined set of start parameters comprising a position of the access cut and/or a cover surface radius and/or an edge zone radius and/or an azimuth angle range and/or a further azimuth angle range and/or a clearance distance and/or parameters of at least one edge zone segment cut. Planning procedure according to one of the Claims 10 until 12 , wherein each start parameter can only be modified within a parameter interval specific to each parameter stored in the start control data and/or at least one start parameter can be set invariably as a fixed value. Planning procedure according to one of the Claims 10 until 13 , wherein the nerve data represent a measurement of a high-resolution OCT and/or a measurement of a confocal microscope, wherein the measurement preferably has a resolution of 5 µm or less. Planning procedure according to one of the Claims 10 until 14 , wherein when generating the weighting value - a branching index of individual nerves represented by the nerve data is taken into account, wherein the branching index represents at least a number of branches after the cutting of nerves; and/or - thickness information of individual nerves represented by the nerve data is taken into account, wherein the thickness information represents at least a thickness of the nerves; and/or - residual length information is taken into account, wherein the residual length information represents at least a total length of the cut nerves represented by the nerve data. Planning unit according to one of the Claims 1 until 6 or ophthalmological laser therapy device according to Claim 7 or 8 , which or which is designed a planning procedure according to one of the Claims 9 until 15 to carry out. A computer program product comprising instructions which, when loaded into a data processing device, cause the device to carry out a planning method according to one of the Claims 9 until 15 to execute. Computer-readable non-volatile storage medium comprising the computer program product according to Claim 17 .