Patent Publication Number: US-2021169693-A1

Title: Method for controlling an eye surgical laser with a transition zone at the volume body

Description:
The invention relates to a method for controlling an eye surgical laser of a treatment apparatus for the separation of a volume body with an anterior interface and with a posterior interface, wherein the anterior interface and the posterior interface contact each other at an edge of the volume body, in particular from a human or animal cornea. Further, the invention relates to a treatment apparatus, to a computer program as well as to a computer-readable medium. 
     Opacities and scars within the cornea, which can arise by inflammations, injuries or congenital diseases, impair the sight. In particular in case that these pathological and/or unnaturally altered areas of the cornea are located in the axis of vision of the eye, clear sight is considerably disturbed. In known manner, the thus altered areas are eliminated by so-called phototherapeutic keratectomy (PTK) by means of an ablatively effective laser, for example an excimer laser. However, this is only possible if the pathological and/or unnaturally altered areas of the cornea are located in the superficial layers of the cornea. Subjacent areas, in particular within the stroma, are not reachable by means of ablative laser methods. Here, additional measures such as for example the exposure of the subjacent areas have to be taken by means of an additional corneal incision. By the additional measures, the treatment duration is disadvantageously considerably increased. In addition, there is the risk that further complications such as for example the occurrence of inflammations at the incision locations occur by the additional corneal incisions. 
     It is the object of the present invention to provide a method, a treatment apparatus, a computer program as well as a computer-readable medium, by means of which an improved control of an eye surgical laser can be performed. 
     This object is solved by a method, a treatment apparatus, a computer program as well as a computer-readable medium according to the independent claims. Advantageous forms of configuration are specified in the dependent claims. 
     An aspect of the invention relates to a method for controlling an eye surgical laser of a treatment apparatus for the separation of a volume body with an anterior interface and with a posterior interface, wherein the anterior interface and the posterior interface contact each other at an edge of the volume body, in particular from a human or animal cornea. Determining a target position of a pupil of the eye to a laser beam of the laser in a neutral pose of a beam deflection device of the treatment apparatus depending on patient information and determining an optical zone with a treatment center on at least one of the interfaces relative to an optical axis of the laser beam in the neutral pose of the beam deflection device depending on patient information are effected. A transition zone at the volume body is determined as an extension of the interface with the optical zone. A current actual position of the pupil is captured by means of the optical capturing device of the treatment apparatus. Determining a deviation between the target position and the actual position is effected. Decentration of the determined optical zone relative to the optical axis of the laser beam in the neutral pose of the beam deflection device is performed depending on the determined deviation such that the edge of the volume body is generated concentrically to the optical axis of the laser beam in the neutral pose of the beam deflection device and the optical zone is generated concentrically to the determined treatment center and within the transition zone. 
     In other words, if a deviation of the actual position from the target position should be present, it is provided that the volume body can nevertheless be reliably separated based on the transition zone and the treatment can be performed on the patient. In particular, this method can be performed, for example if a perfect centering of the eye should not have been accomplished. A new setup from the eye and from the laser, respectively, does not have to be performed, but the treatment can be continued based on the transition zone. Thus, a progression of the transition zone can in particular occur and an optical correction can nevertheless be realized at the correct location. 
     In other words, it is provided that a decentration of the optical zone of the volume body, which can also be referred to as lenticule, can be performed without displacement of the laser. However, the edge of the lenticule additionally remains concentric to the rotational axis of the beam deflection device, which can also be referred to as scanner. In particular, based on a difference vector between the actual position and the target position, the optical zone is applied within the lenticule. The optical zone becomes narrower in the direction of the decentration and wider in the opposite direction. Thus, an asymmetric transition zone can in particular be provided. 
     In particular, the beam deflection device has a neutral pose. For example, the beam deflection device can have two mirrors for deflecting the laser beam. Then, the neutral pose is given with a so-called 0/0 pose of the mirrors to each other. With a rotation of the mirrors, the incident laser beam experiences a deflection and thus can for example be positioned on the cornea. Thus, the beam deflection device has a rotational axis, around which the incident laser beam can be rotated depending on the mirror positions. 
     According to an advantageous form of configuration, the optical zone and transition zone are determined on the posterior interface. Alternatively or additionally, the optical zone and the transition zone can be determined on the anterior interface. Thereby, it is allowed that the transition zone can be formed on both interfaces. Thus, the control of the laser can in particular be effected such that a decentration can be performed and the optical zone can nevertheless be reliably generated concentrically to the determined treatment center within the transition zone. 
     It is also advantageous if the transition zone of the volume body is generated as a non-centered crescent. In other words, the volume body is in particular lenticularly formed. Thereby, a reliable separation of the volume body can be realized. 
     It is further advantageous if the volume body is generated asymmetrically and concentrically to the optical axis of the laser beam in the neutral pose of the beam deflection device. Thereby, it is allowed that the optical zone is generated concentrically to the determined treatment center within the transition zone. Thereby, a treatment can be reliably performed even without reorientation of the laser. 
     It is further advantageous if the optical zone is decentered and/or displaced by a distance as the deviation between the target position and the actual position of the pupil. This deviation can in particular be referred to as difference vector. Thereby, the transition zone can be reliably determined based on the difference vector. Then, the difference vector is applied to the optical zone within the lenticule such that the transition zone becomes narrower in the direction of decentration and in particular wider in the opposite direction. Thereby, an asymmetric transition zone can in particular be provided. 
     Further, it has proven advantageous if the optical zone is decentered and/or displaced such that an asymmetric transition zone is generated. Based on the asymmetric transition zone, the optical zone can nevertheless be reliably generated concentrically to the determined treatment center within the transition zone. Thus, an improved treatment of the patient is allowed. 
     It is further advantageous if the control of the laser is effected such that topographic and/or tachymetric and/or morphologic data of the cornea is taken into account. Thus, topographic and/or tachymetric measurements of the cornea to be treated as well as of the type, the position and the extent of the for example pathological and/or unnaturally altered area within the stroma of the cornea can in particular be taken into account. In particular, control datasets are generated at least by providing topographic and/or tachymetric and/or morphologic data of the untreated cornea and providing topographic and/or tachymetric and/or morphologic data of the pathological and/or unnaturally altered area to be removed within the cornea. 
     A further aspect of the invention relates to a treatment apparatus with at least one surgical laser for the separation of a volume body with predefined interfaces of a human or animal eye for example by means of photodisruption and with at least one control device for the laser or lasers, which is formed to execute the steps of the method according to the preceding aspect. The treatment apparatus according to the invention allows that disadvantages arising in the use of usual ablative treatment apparatuses, namely relatively long treatment times and relatively high energy input by the laser into the cornea, are reliably avoided. These advantages are in particular achieved by the formation of the eye surgical laser as a photodisruptive laser. 
     Therein, the laser is suitable to emit laser pulses in a wavelength range between 300 nm and 1,400 nm, preferably between 700 nm and 1,200 nm, at a respective pulse duration between 1 fs and 1 ns, preferably between 10 fs and 10 ps, and a repetition frequency of greater than 10 kHz, preferably between 100 kHz and 100 MHz. 
     In an advantageous form of configuration of the treatment apparatus, the treatment apparatus comprises a storage device for at least temporarily storing at least one control dataset, wherein the control dataset or datasets include(s) control data for positioning and/or focusing individual laser pulses in the cornea, and includes at least one beam device for beam guidance and/or beam shaping and/or beam deflection and/or beam focusing of a laser beam of the laser. Therein, the mentioned control datasets are usually generated based on a measured topography and/or tachymetry and/or morphology of the cornea to be treated and the type of the pathologically and/or unnaturally altered area to be removed within the cornea. 
     Further features and the advantages thereof can be taken from the descriptions of the first inventive aspect, wherein advantageous configurations of each inventive aspect are to be regarded as advantageous configurations of the respectively other inventive aspect. 
     A third aspect of the invention relates to a computer program including commands, which cause the treatment apparatus according to the second inventive aspect to execute the method steps according to the first inventive aspect. A fourth aspect of the invention relates to a computer-readable medium, on which the computer program according to the third inventive aspect is stored. Further features and the advantages thereof can be taken from the descriptions of the first and the second inventive aspect, wherein advantageous configurations of each inventive aspect are to be regarded as advantageous configurations of the respectively other inventive aspect. 
     Further features are apparent from the claims, the figures and the description of figures. The features and feature combinations mentioned above in the description as well as the features and feature combinations mentioned below in the description of figures and/or shown in the figures alone are usable not only in the respectively specified combination, but also in other combinations without departing from the scope of the invention. Thus, implementations are also to be considered as encompassed and disclosed by the invention, which are not explicitly shown in the figures and explained, but arise from and can be generated by separated feature combinations from the explained implementations. Implementations and feature combinations are also to be considered as disclosed, which thus do not comprise all of the features of an originally formulated independent claim. Moreover, implementations and feature combinations are to be considered as disclosed, in particular by the implementations set out above, which extend beyond or deviate from the feature combinations set out in the relations of the claims. 
    
    
     
       The figures show the following. 
         FIG. 1  is a schematic side view of an embodiment of a treatment apparatus. 
         FIG. 2  is a further schematic side view of an embodiment of the treatment apparatus. 
         FIG. 3  is a schematic sectional view of an eye of a patient. 
         FIG. 4  is a further schematic sectional view of an eye of a patient. 
         FIG. 5  is a still further schematic sectional view of an eye of a patient. 
     
    
    
     In the figures, identical or functionally identical elements are provided with the same reference characters. 
       FIG. 1  shows a schematic representation of a treatment apparatus  10  with an eye surgical laser  18  for the separation of a predefined corneal volume or volume body  12  with predefined interfaces  14 ,  16  of a cornea of a human or animal eye  40  ( FIG. 3 ) by means of photodisruption as presently shown. One recognizes that a control device  20  for the laser  18  is formed besides the laser  18 , such that it emits pulsed laser pulses in a predefined pattern into the cornea, wherein the interfaces  14 ,  16  of the volume body  12  to be separated are generated by the predefined pattern by means of photodisruption. In the illustrated embodiment, the interfaces  14 ,  16  form a lenticular volume body  12 , wherein the position of the volume body  12  is selected in this embodiment such that a pathological and/or unnaturally altered area  32  (see  FIG. 2 ) within a stroma  36  of the cornea is enclosed. Furthermore, it is apparent from  FIG. 1  that the so-called Bowman&#39;s membrane  38  is formed between the stroma  36  and an epithelium  28 . 
     Furthermore, one recognizes that the laser beam  24  generated by the laser  18  is deflected towards a surface  26  of the cornea by means of a beam deflection device  22  such as for example a scanner. The beam deflection device  22  is also controlled by the control device  20  to generate the mentioned predefined pattern in the cornea. The beam deflection device  22  for example comprises two mirrors. The incident laser beam  24  can be rotated by rotation around a rotational axis. In a neutral pose of the mirrors, a so-called optical axis  30  ( FIG. 3 ) of the laser beam  24  is in particular formed. 
     The illustrated laser  18  is a photodisruptive laser, which is formed to emit laser pulses in a wavelength range between 300 nm and 1400 nm, preferably between 700 nm and 1200 nm, at a respective pulse duration between 1 fs and 1 ns, preferably between 10 fs and 10 ps, and a repetition frequency of greater than 10 kHz, preferably between 100 kHz and 100 MHz. 
     In addition, the control device  20  comprises a storage device (not illustrated) for at least temporarily storing at least one control dataset, wherein the control dataset or datasets include(s) control data for positioning and/or for focusing individual laser pulses in the cornea. The position data and/or focusing data of the individual laser pulses are generated based on a previously measured topography and/or pachymetry and/or the morphology of the cornea and the pathological and/or unnaturally altered area  32  for example to be removed within the stroma  36  of the eye. 
       FIG. 2  shows a schematic diagram of the generation of the volume body  12  to be separated according to an embodiment of the present method. One recognizes that the interfaces  14 ,  16  are generated by means of the pulsed laser beam  24 , which is directed towards the cornea or towards the surface  26  of the cornea via the beam deflection device  22 . Therein, the interfaces  14 ,  16  form a lenticular volume body  12 , which for example encloses the pathological and/or unnaturally altered area  32  within the stroma  36 . Furthermore, the laser  18  generates a further incision  34  in the illustrated embodiment, which intersects the volume body  12  at a predefined angle and with a predefined geometry and is formed up to the surface  26  of the cornea. The volume body  12  defined by the interfaces  14 ,  16  can then be removed from the cornea via the incision  34 . In the illustrated embodiment, the pathological and/or unnaturally altered area  32  is formed within the stroma  36 . 
     In the illustrated embodiment, the interface  14 , that is the interface located deeper in the eye or the stroma  36 , is first formed by means of the laser beam  24 , wherein it then corresponds to the posterior interface  14 . This can be effected by at least partially circularly and/or spirally guiding the laser beam  24  according to the predefined pattern. Subsequently, the interface  16  is generated in comparable manner, which then corresponds to the anterior interface  16 , such that the interfaces  14 ,  16  form the lenticular volume body  12  (see also  FIG. 1 ). Subsequently, the incision  34  is also generated by the laser  18 . However, the order of the generation of the interfaces  14 ,  16  and of the incision  34  can also be changed. 
       FIG. 3  shows an eye  40  of a patient in a first situation in a schematic sectional view. Presently, it can in particular be seen how a patient interface  42  of the treatment apparatus  10  rests on the eye  40 . In particular, the volume body  12  is formed by the anterior interface  16  as well as by the posterior interface  14 . In the present embodiment, the posterior interface  14  is to be regarded as an optical zone  44 . At an edge  46  of the interfaces  14 ,  16 , a transition zone  48  is in particular formed. In the present embodiment, the transition zone  48  is identically formed on both sides. In other words, the transition zone  48  is centered and symmetric. 
       FIG. 4  shows the eye  40  in a further situation in a schematic sectional view. In particular, a non-optimum eye position relative to the patient interface  42  is shown in  FIG. 4  in contrast to  FIG. 3 . 
     In particular, it is shown in  FIG. 4  that the anterior interface  16  and the posterior interface  14  contact each other at the edge  46  of the volume body  12 . Determining a target position of a pupil of the eye  40  to the laser beam  24  in the neutral pose of the beam deflection device  22  depending on patient information and determining the optical zone  44  with a treatment center  52  on at least one of the interfaces  14 ,  16  relative to the optical axis  30  of the laser beam  24  depending on patient information can be performed. Determining the transition zone  48  at the volume body  12  as an extension of the interfaces  14 ,  16  with the optical zone  44  is effected. A current actual position of the pupil is captured by means of an optical capturing device  50  ( FIG. 1 ) of the treatment apparatus  10 . Further, a deviation between the target position and the actual position is determined and decentration of the determined optical zone  44  relative to the optical axis  30  of the laser  18  is effected depending on the determined deviation such that the edge  46  of the volume body  12  is generated concentrically to the optical axis  30  and the optical zone  44  is generated concentrically to the determined treatment center  52  and within the transition zone  48 . 
     In particular,  FIG. 4  shows that the optical zone  44  and the transition zone  48  can be determined on the posterior interface  14 . Alternatively or additionally, the optical zone  44  and the transition zone  48  can also be determined on the anterior interface  16 . 
       FIG. 5  shows an eye  40  of the patient in a further schematic sectional view. In  FIG. 5 , the treatment center  52  is in particular displaced such that the transition zone  48  is only formed on the left side shown in  FIG. 5 . 
     In particular, the transition zone  48  of the volume body  12  can be generated as a non-centered crescent. Furthermore, it can in particular be provided that the volume body  12  is generated asymmetrically and concentrically to the optical axis  30 . In particular, it can be provided that the optical zone  44  is decentered and/or displaced by a distance as the deviation between the target position and the actual position of the pupil. In particular, the optical zone  44  can be decentered and/or displaced such that an asymmetric transition zone  48  is generated.