The invention relates to a planning apparatus for generating control data for a treatment device, which produces at least one cut surface in the cornea by application of a laser apparatus. The invention further relates to a treatment device, which has a planning apparatus of the type mentioned.
The invention further relates to a method for generating control data for a treatment device, which produces at least one cut surface in the cornea by application of a laser apparatus.
Various treatment methods with the aim of refraction correction of the human eye are known in the prior art. The aim of the surgical techniques is thereby to selectively alter the cornea in order to thus influence light refraction in the eye. To this end, several surgical techniques are used. The most common is currently so-called laser-assisted in situ keratomileusis, which is also abbreviated as LASIK. Here, a corneal lamella of the corneal surface is first detached on one side and folded aside. Detachment of this lamella can take place by means of a mechanical microkeratome, or also by means of a so-called laser keratome, such as is marketed by Intralase Corp., Irvine, USA, for example. After the lamella is detached and folded aside, the use of an excimer laser is provided during the LASIK operation, which removes the thus exposed corneal tissue under the lamella by means of ablation. After the volume under the corneal surface is vaporized in this manner, the corneal lamella is folded back to its original place.
The use of a laser keratome to lift the lamella is advantageous in comparison with a mechanical knife, as this improves geometric precision and reduces the frequency of clinically relevant complications. In particular, a lamella with a very much more constant thickness can be produced when laser radiation is used. The cut edge is also precisely formed, which reduces the risk for disordered healing by these boundary layers which also remain after the operation. A disadvantage of this method, however, is the fact that two different treatment devices must be used, firstly the laser keratome specifically to separate the lamella, and secondly the corneal tissue vaporizing laser.
These drawbacks have been eliminated in a process recently implemented by Carl Zeiss Meditec AG and designated with the abbreviation FLEx. In this method for lenticular extraction, a cut geometry is formed in the cornea by means of a short-pulse laser, preferably a femtosecond laser, which separates a corneal volume (so-called lenticule) in the cornea. This is then manually removed by the surgeon after the lenticule-covering lamella has been folded aside. The advantage of this method lies firstly in that the cut quality is again improved through use of the femtosecond laser.
Secondly, only one treatment device is necessary; the excimer laser is no longer used.
A further development of the FLEx method is referred to in the literature as the SMILE method, in which no flap is created, but rather only a small opening cut serves as an access to the lenticule harbored under the so-called cap. The separated lenticule is removed through this small opening cut, so that the biomechanical integrity of the anterior cornea is less affected than with LASIK, FLEx or PRK. Additionally, in this way fewer superficial nerve fibers are cut in the cornea, which has a demonstrably favorable effect on the restoration of the original sensitivity of the corneal surface. The symptom of dry eye, often to be treated after LASIK, is thereby reduced in severity and duration. Other complications following LASIK, primarily associated with the flap (for example, wrinkles, epithelial growths in the flap bed), occur more rarely without the flap.
When generating cut surfaces in the cornea by application of laser radiation, the optical radiation effect is typically exploited such that an optical breakthrough is generated by application of individual optical pulses whose duration may be between approximately 100 fs and 100 ns. It is also known to introduce individual pulses, the energy of which is below a threshold for optical breakthrough, into the tissue or material overlaid in such a way that a separation of material or tissue is also thereby achieved. This concept of cut production in the corneal tissue allows a wide variety of cuts.
In the cut geometry of the SMILE method according to the state of the art, it has been found that due to the small opening cuts, the two cuts bounding the lenticule (cap cut and lenticular cut) cannot clearly be identified in every case, which can therefore lead to problems during removal of the lenticule. This is carried out with a spatula-shaped instrument (also called a flap lifter), and it can occur that the doctor encounters the wrong cut surface and therefore does not correctly separate the lenticule.
An aspect of the invention is therefore to provide a planning apparatus for generating control data, a treatment device for refraction-correcting opthalmic surgery and a method for generating control data for such a treatment device, in which an optimal execution of the access cuts to the lenticule is guaranteed.
This aspect is achieved according to the invention with a planning apparatus of the aforementioned type, which is configured to define a corneal cut surface, and configured to determine a first access cut for the cap cut and a second access cut for the lenticular cut, wherein the tissue in the area of the access cuts is completely severed.
The invention is further achieved with a treatment device which has a laser apparatus, which separates at least one cut surface in the cornea by application of laser radiation according to control data, and which has a planning apparatus according to the aforementioned type for generating control data, wherein the planning apparatus determines a first access cut for the cap cut and a second access cut for the lenticular cut, wherein the tissue is completely severed in the area of the access cuts.
Finally, the invention is also achieved with a method for generating control data according to the type mentioned above, having: generation of a control dataset for the corneal cut surface for controlling the laser apparatus, wherein the planning apparatus determines a first access cut for the cap cut and a second access cut for the lenticular cut, such that the tissue is completely severed in the area of the access cuts.
The invention is finally also achieved with a method, comprising: Generation of a control dataset for the corneal cut surface, transmission of the control data to the treatment device and generation of the cutting surfaces through control of the laser apparatus with the control dataset, wherein during generation of the control dataset a first access cut for the cap cut and a second access cut for the lenticular cut are determined such that the tissue in the area of the access cuts is completely severed.
The cap cut, i.e. the anterior cut running largely parallel to the corneal surface, is selected to be greater than the lenticular diameter. In addition, a second access cut is produced according to the invention which renders the lenticular cut accessible from the outside. This access cut can preferably be of a circularly segmented nature or strip-shaped.
It is thereby advantageous if the second access cut lies approximately at the diameter of the lenticular cut. Through the complete severing of the tissue in the area of the access cuts, finding and reaching the respective cuts is made decisively easier for the doctor, additionally the cuts are easier to identify. This complete severing of the tissue can be achieved inter alia by increasing the energy of the laser pulses, or also by a reduction in the track distance and/or spot distance of the individual laser pulses.
Furthermore, it is advantageous if the first and second access cuts are located differently with respect to the axis of the eye. According to an example embodiment, one cut is located temporally and the other cut is located inferiorly, but the combination of nasally inferior and temporally inferior is also an option.
The lenticular cut and cap cut are circular or oval and have a diameter of approximately 4 to 7 mm. The cap thickness is less than 300 μm, preferably between 100 μm and 200 μm. The removal of the lenticule causes a change of refraction, for example, between +10 dpt and −20 dpt, in another example between +5 dpt and −10 dpt. An additional or excludable cylinder correction and/or correction at an alternately high order is possible.
It is understood that the features mentioned above and those yet to be explained can be used not only in the specified combinations but also in other combinations or in isolation without departing from the scope of the present invention.
The invention is hereafter explained in more detail by way of example with reference to the accompanying drawings, which also disclose features essential to the invention.
A treatment device for ophthalmic surgery is shown in
The patient 3 is located on a support 10 which is adjustable in three dimensions in order to align the eye 2 to match the incidence of the laser beam 6. In a preferred construction, the support 10 is adjustable by motor.
The control can especially be carried out by a control unit 11, which generally controls the operation of the treatment device 1, and is connected thereto via suitable data connections, for example connection lines 12, to the treatment device. Of course, this communication can also occur via other means, such as optical fibers or wirelessly. The control unit 11 performs the appropriate settings, time control of the treatment device 1, in particular the laser apparatus 4, and thus accomplishes the relevant functions of the treatment device 1.
The treatment device 1 further comprises an additional fixing apparatus 15 which positionally fixes the cornea of the eye 2 across from the laser device 4. This fixing apparatus 15 can hereby comprise a known contact lens 45, to which the cornea is applied by means of negative pressure and which imparts to the cornea a desired geometric shape. Such contact lenses are well known to those skilled in the art, for example, from DE 102005040338 A1. The disclosure of this document is, as far as the description of a construction of the possible contact lens 45 for the treatment device 1 is concerned, incorporated in full herein.
The treatment device 1 further has a camera, not shown here, which can record an image of the cornea 17 through the contact lens 45. The lighting for the camera can thereby occur both in the visible as well as in the infrared light range.
The control unit 11 of the treatment device 1 yet further has a planning apparatus 16, which will be explained in more detail later.
Alternatively, a tissue-separating effect can also be achieved by means of pulsed laser radiation while a plurality of laser radiation pulses are emitted in an area, wherein the focus spots overlap. A plurality of laser radiation pulses then act together in order to achieve a tissue-separating effect. However, the type of tissue separation which is used by the treatment device 1 is of no further relevance for the following description; it is only essential that generation of a cut surface take place in the cornea 17 of the eye 2.
To perform an ophthalmic surgical correction of refraction, a corneal volume is removed from an area inside the cornea 17 by application of the laser radiation 6, in that the tissue layers are separated there, which isolates the corneal volume and enables the removal thereof. To isolate the corneal volume to be removed, for example, in the case of pulse-introduced laser radiation, the focus 17 of the focused laser radiation 7 is adjusted in the cornea 17. This is shown schematically in
In
The allocation of the individual coordinates to the spacial directions is inessential for the operating principle of the treatment device 1, as is the scanner 8a diverting about mutually perpendicular axes. Rather, any scanner can be used which is able to adjust the focus 19 in a plane in which the axis of incidence of the optical radiation is not located. Furthermore, any non-Cartesian coordinate system can be used to divert or control the position of the focus 19. Examples include spherical coordinates or cylindrical coordinates.
The control of the position of the focus 19 takes place by application of the scanner 8a, 8b under control by the control unit 11, which performs appropriate adjustments to the laser source 5, the (not shown in
The control unit 11 operates in accordance with predetermined control data, which are provided, for instance, by the laser apparatus 4, described herein only by way of example, as target points for the focus adjustment. The control data are normally summarized in a control data set. This results in geometric specifications for the cut surface to be formed, for example the coordinates of the target points as a pattern. The control data set thus also contain in this exemplary embodiment concrete locational values for the focus position adjusting mechanism, for example the scanner 8.
The production of the cut surface with the treatment device 1 is exemplarily shown in
Alternatively, and essential to the present invention, the SMILE method can be used, wherein the corneal volume 21 is removed through a small opening cut, as is described in DE 10 2007 019813 A1. The disclosure of this reference is incorporated herein in full.
The planning apparatus 16 generates a control data set, which is provided to the control unit 11 to perform the ophthalmic correction of refraction. Here, the planning apparatus uses measurement data of the cornea of the eye. This data originates in the embodiment described herein from a measuring apparatus 28, which has previously measured the eye 2 of the patient 2. Of course, the measuring device 28 may be formed in any desired manner and transmit the corresponding data to the interface 29 of the planning apparatus 16.
The planning apparatus now supports the operator of the treatment device 1 in the definition of the cut surface for isolation of the corneal volume 21. This can extend up to a fully automatic determination of the cut surfaces, which can be accomplished, for example, in that the planning apparatus 16 determines from the measured data the corneal volume 21 to be removed, defines the boundary surfaces thereof as cut surfaces and generates corresponding data therefrom for the control unit 11. At the other end of the degree of automation, the planning apparatus 16 may provide input options, where a user enters the cut surfaces in the form of geometric parameters etc. Intermediary levels provide suggestions for the cut surfaces, which the planning apparatus automatically generates and which can then be modified by an operator. In principle, all those concepts that have already been explained in the above general description section, come into use here in the planning apparatus 16.
To carry out a treatment, the planning apparatus 16 generates control data for the cut surface, which are then used in the treatment device 1.
a shows a schematic representation of a corneal cross-section for illustrating the geometric relationships according to the prior art in the SMILE method. The cornea 17 has an anterior cap cut 22 with an opening cut 26. The posterior lenticular cut 23 isolates the lenticular volume 21, which can be removed through the opening cut 26. For this purpose, the lenticule 21 must first be completely separated in that with a spatula-shaped instrument the still-remaining tissue bridge around the cap cut 22 and the lenticular cut 23 are mechanically separated. It may hereby occur that the doctor misses the lenticular side cut forming the crossover from the cap cut 22 to the lenticular cut 23, and therefore the lenticule does not separate properly.
a shows a schematic representation of a cut geometry according to an example embodiment of the invention. Cap cut 22, lenticular cut 23 and opening cut 26 correspond to the relationships already shown in
b shows a top view of the cornea shown in
a shows a schematic representation of a cut geometry according to a further example embodiment of the invention. Cap cut 22, lenticular cut 23 and opening cut 26 correspond to the relationships already shown in
In addition, it should be noted that the treatment device 1 or the planning apparatus 16 can, of course, also be concretely realized through the implementation of the method generally explained above.
A further exemplary embodiment of the planning apparatus 16 comprises a computer program or a corresponding data carrier with a computer program which realizes the planning device on a corresponding computer, such that the input of the measurement data takes place via a suitable data transmission means and the control data from this computer is transferred to the control unit 11, for which in turn data transfer means known to one skilled in the art come into question.
Number | Date | Country | Kind |
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10 2013 004 688.2 | Mar 2013 | DE | national |
This application is a National Phase entry of PCT Application No. PCT/EP2014/054969 filed Mar. 13, 2014, which application claims the benefit of priority to German Application No. 10 2013 004 688.2, filed Mar. 13, 2013, the entire disclosures of which are incorporated herein by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/054969 | 3/13/2014 | WO | 00 |