Abstract:
An opthalmological device for resolving eye tissue includes a base station with a light source for producing light pulses. Attached to the base station is a supporting arm with an application head that can be placed on an eye. The light pulses are transmitted from the base station through an optical transmission system to the application head. The application head has a light projector for the focused projection of the light pulses for point-by-point resolution of the eye tissue. The supporting arm is rigidly configured and has at one end a rotary joint with a horizontally aligned axis of rotation, wherein the rotary joint is attached in such a way that the application head can be placed on the eye with a rotation about the axis of rotation. The rotary joint makes it possible for the application head or the light projector to be manually docked in a controlled manner onto the eye in the vertical direction by means of a rotational movement that is easy to perform and has low mechanical friction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §371 National Phase conversion of PCT/CH2007/000078, filed Feb. 14, 2007. The PCT International Application was published in the German language. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to an opthalmological apparatus for breakdown of eye tissue. The invention relates in particular to an opthalmological apparatus that comprises a base station with a light source for generating light pulses, an application head that can be mounted on the base station by means of a support arm and can be placed onto the eye, with a light projector for focused projection of the light pulses, and an optical transmission system for transmitting the light pulses from the base station through the support arm to the application head. 
     2. Related Art 
     Instances of ametropia such as myopia (short-sightedness), hyperopia (long-sightedness or far-sightedness) or astigmatism can nowadays be permanently corrected by refractive surgical treatment. Refractive surgical treatments are surgical operations on the eye which change the optical refractive power of the eye with the aim of bringing it as close to a desired value as possible. One of the most important methods in refractive surgery is so-called laser-assisted in situ keratomileusis (LASIK) in which the interior of the cornea is removed with the aid of a computer-controlled excimer laser after a corneal flap has previously been partially severed and folded aside. To produce the corneal flap, use is made of mechanical microkeratomes in which a driven scalpel cuts the corneal flap. Recently, such corneal flaps have also been cut with the aid of strongly focused femtosecond laser pulses, which have pulse widths of typically 100 fs to 1000 fs (1 fs=10 −15  s). In addition to LASIK, there are further procedures for refractive correction that are performed on the cornea with the aid of femtosecond lasers. 
     Such a system is marketed, for example, by IntraLase Corp, in Irvine, Calif., USA under the name of Pulsion FS Laser. In this system, a light source (femto laser) is located in a base station and is connected to an optical application head via an articulated mirror arm. In addition to the optical transmission system, a deflection system (scanner) and the light projector, the application head also comprises viewing means, such as camera or surgical microscope, and therefore has a considerable weight of several kilograms. For orienting and applying the light projector onto an eye of a patient, the entire application head is moved via translatory drives. The patient lies on a bed and does not move. For reasons of weight, the application cannot be done by hand, and motorized drives are necessary. To avoid applying excessive forces to the patient, the laser system comprises force-measuring systems in the vertical application direction. 
     Systems for cutting the corneal flap with focused femtosecond laser pulses are also marketed by Zeiss Meditec AG, with its Visumax, and by 20/10 Perfect Vision Optische Geräte GmbH, with its Femtec. In these systems, the light projector is connected fixedly to the base station. In these systems, the patient is oriented in the horizontal plane and also vertically with respect to the light projector with the aid of a patient bed. Therefore, these systems too cannot be applied manually onto the patient&#39;s eye. In addition, the special patient bed has to be integrated into the safety system of the laser system in order to avoid uncontrolled movements of the bed. The bed is thus part of the laser system and thus increases the system costs and the space required. A suitable choice of bed by the person using the system is not possible. 
     In the aforementioned systems, the docking of the light projector onto the patient&#39;s eye is first effected by orientation in the horizontal plane in the x-direction and y-direction (centering of the eye) and then by lowering in the vertical z-direction. 
     EP 1731120 describes a system in which the application head is mounted flexibly on the base station via an articulated mirror arm composed of several arm elements and joints and permits manual application of the application head and light projector onto the eye of a patient. To permit the weight of the application head for manual application by means of the articulated mirror arm, the light projector has smaller lens systems compared to the previously known systems. In order to ensure that, despite the lens system of smaller dimensions, it is possible to work with focused laser pulses across an extensive work area on the eye, the application head additionally has movement drivers for moving the light projector in an advance direction and in a first scanning direction. An optical deflection to a vertical scanning direction is not possible, however. The limited work area permits only rapid positioning of the laser pulses within the work area. Limits are thus set on flexible positioning of the laser pulses across the entire eye. 
     SUMMARY 
     It is an object of the present invention to propose a novel opthalmological apparatus for breakdown of eye tissue, which apparatus avoids at least some disadvantages of the prior art. A particular object of the present invention is to make available an opthalmological apparatus for breakdown of eye tissue which enables manual application of the light projector onto an eye of a patient but permits a light projector with optics of high numerical aperture, which permits the focused projection of laser pulses in the whole viewable eye area both in the horizontal and also the vertical direction. 
     According to present invention, these objects are achieved in particular by the elements of the independent claims. Further advantageous embodiments are also set forth in the dependent claims and the description. 
     The opthalmological apparatus comprises a base station with a light source for generating light pulses, a support arm mounted on the base station, an application head that is mounted on the support arm and can be placed onto an eye and has a light projector for focused projection of the light pulses for punctiform breakdown of eye tissue, and an optical transmission system for transmitting the light pulses from the base station through the support arm to the application head. 
     The aforementioned objects are achieved in the present invention particularly by virtue of the fact that the support arm is of rigid design and, at one end, has a hinge with a horizontally oriented rotation axis, the hinge being mounted in such a way that the application head can be placed onto the eye with a rotation (rotation movement) extending about the rotation axis. The rigid support arm, i.e. designed in one piece and inherently immovable, permits a stable and simple connection of the application head to the base station. In particular, the rigid support arm makes it possible to design the optical transmission system more simply than is the case, for example, with a multi-part articulated mirror arm. The hinge arranged horizontally on an end of the rigid support arm permits application of the application head or of the light projector onto the eye in the vertical direction via a preferably mechanically executed rotation movement, wherein the application head is guided on a kinematically generated arc, which permits a vertical movement component for placement onto the eye. The advantage of the rotation movement is its simple configuration and minimal mechanical friction. The support arm and the hinge thus permit controlled manual docking, i.e. application of the application head or light projector onto the eye, the user advantageously being able to employ his tactile senses in order to control the force or movement exerted via the tactile force and movement feedback. Because active systems for applying force and limiting force are unnecessary, increased safety is achieved only through the use of passive system elements. On account of the simply designed support arm and the actuators and sensors required only in small numbers, or not at all, a further simplified configuration and therefore lower costs are achieved. Moreover, the overall size of the components located directly over the patient can be reduced. 
     The hinge is preferably arranged on that end of the support arm directed away from the base station, and the application head is connected movably to the support arm via the hinge. By means of the movable arrangement of the application head on the rigid support arm via a hinge, the size and weight of the system part to be applied manually is reduced, which further facilitates the manual application and makes it controllable. 
     In an embodiment variant, the application head is connected fixedly to the support arm and the hinge is arranged on that end of the support arm directed towards the base station, such that the support arm and therefore the application head secured thereon is connected movably to the base station via the hinge. The advantage of a lengthened rotation arm is that the rotation executed during the application has a greater radius and therefore requires a smaller rotation angle for the vertical excursion, which once again means smaller deviations from a vertical application axis. 
     In another embodiment variant, the apparatus comprises positioning means for rotary and/or translatory movement of the support arm parallel to a positioning plane for the positioning of the application head over the eye. The positioning means comprise, for example, guide rails and/or drive means for translatory movements in a horizontal positioning plane and/or hinges that permit a rotation (rotation movement) about a vertically extending rotation axis. 
     In an embodiment variant, the apparatus comprises beam-deflecting means arranged in the support arm and used for deflecting the light pulses in at least two scanning directions, and the light projector is dimensioned such that, without mechanical movement of the light projector, deflected light pulses can be projected in a focused manner across an entire working area of preferably 11 mm in diameter for breakdown of eye tissue. 
     In another embodiment variant, the application head has a viewing window permitting a top view of the eye in the projection direction of the light projector. The viewing window permits a top view of the eye by way of optical viewing or measuring modules, e.g. cameras, microscopes, measuring devices, which are connected movably to the base station and which, oriented in the projection direction of the light projector, can be swivelled over the viewing window, while the application head is placed on or is being placed onto the eye. Moreover, the optical viewing or measuring modules can be swivelled away when not required. The possibility of optical viewing or measuring modules being able to be swivelled into and out of the line of sight above the eye means that the overall size and therefore the weight of the application head can be further reduced and its handling improved. 
     In an embodiment variant, weight compensation means are connected to the application head, in order to partially balance out the application head above the rotation axis in such a way that the application head can be placed onto the eye with an application force reduced by the inherent weight of the application head. By means of the only partially balanced out configuration of the masses involved in the rotation movement (application head and, depending on the design, the support arm), the application force on the eye can be generated by gravity. 
     In another embodiment variant, the light projector comprises a first lens system in a projection part of the application head oriented in the projection direction, and the light projector comprises a second lens system in a feed part of the application head angled away from the projection part and directed towards the support arm, said first and second lens systems being coupled via a deflecting mirror. The arrangement of the lens systems divided up into the projection part and feed part permits a reduction of the structural height of the light projector and thus of the application head. Moreover, external aids such as microscopes or measuring devices can be adapted more easily. 
     In an embodiment variant, the application head comprises a projection part oriented in the projection direction and a feed part angled away from the projection part and directed towards the support arm. The projection part is connected rotatably to the feed part, e.g. axially about a longitudinal axis extending through the feed part and/or about a transverse axis extending perpendicular to the longitudinal axis of the feed part. The rotatable connection of the projection part to the feed part allows light projector and securing means mounted thereon to be oriented precisely with the eye. 
     In another embodiment variant, the apparatus comprises a lock for fixing or releasing a rotation position of the application head about the rotation axis. 
     In one embodiment variant, the apparatus comprises height-defining means for determining a vertical position of the eye, and the base station comprises height-positioning means for setting a vertical basic position of the support arm. By setting a vertical basic position of the support arm, the rotation movement needed for vertical placement of the application head onto the eye can be reduced and thus be kept in an area closer to the vertical movement component, which on the one hand reduces the movement stroke necessary for the docking of the application head and on the other hand facilitates the horizontal orientation of application head and eye (centering). 
     In other embodiment variants, the application head has one or more grips and grip structures for manual handling, a contact body which can be placed onto the eye, is transparent at least in parts and is configured and arranged such that it sets a contacted area of the eye equidistant to a working surface, and securing means for fixing the application head on the eye by underpressure. The light source preferably comprises a femtosecond laser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention is described below by way of example. The illustrative embodiment is depicted in the attached figures, in which: 
         FIG. 1  shows a schematic side view of the opthalmological apparatus, comprising a one-piece design of a base station with a support arm on which an application head is mounted rotatably. 
         FIG. 2  shows a schematic side view of an opthalmological apparatus comprising a support arm which can be moved in translation relative to the base station in a horizontal positioning plane and on which the application head is mounted rotatably. 
         FIG. 3  shows a schematic top view of an opthalmological apparatus comprising a support arm which can be moved in translation relative to the base station in the positioning plane and on which the application head is mounted rotatably. 
         FIG. 4  shows a schematic top view of an opthalmological apparatus comprising a support arm which can be moved in translation and rotation relative to the base station in the positioning plane and on which the application head is mounted rotatably. 
         FIG. 5  shows a schematic top view of an opthalmological apparatus comprising a support arm which can be moved in rotation relative to the base station about two vertical axes of rotation in the positioning plane and on which the application head is mounted rotatably. 
         FIG. 6  shows a schematic top view of another opthalmological apparatus comprising a support arm which can be moved in rotation relative to the base station in the positioning plane about two vertical axes of rotation and on which the application head is mounted rotatably. 
         FIG. 7  shows a schematic side view of the application head, which comprises one lens system in a feed part to the support arm and another lens system in an angled projection part. 
         FIG. 8  shows a schematic side view of the application head, comprising a viewing window over the projection part, to which an optical viewing aid or measuring module is coupled in a releasable manner. 
         FIG. 9  shows a schematic side view of the application head, comprising a projection part connected rotatably to the feed part. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In  FIGS. 1 to 6 , reference number  1  designates an opthalmological apparatus for breakdown of eye tissue. The opthalmological apparatus  1  comprises a base station  2  and an inherently rigid support arm  3  mounted thereon. An application head  4  is mounted on the support arm  3  fixedly or via a horizontally oriented hinge R z .  FIG. 1  also shows an optional optical viewing, imaging and/or measuring module  7  connected fixedly to the support arm  3 , for example a monitor and/or a microscope for observing the application procedure (docking) and the treatment. In the embodiment variants according to  FIGS. 1 to 6 , the application head  4  is connected to the support arm  3  via the hinge R z  so as to rotate about the horizontal rotation axis r z . The hinge R z  is in each case arranged at that end of the support arm  3  directed away from the connection of the support arm  3  to the base station  2 . As is shown schematically in the side views in  FIGS. 1 and 2 , the hinge R z  is arranged and configured such that, by the rotation z rot  of the application head  4  about the rotation axis r z , a vertical movement component can be executed in the z-direction for lowering and placing the application head  4  onto an eye  6 . For manual handling, grips and/or grip structures  46  are mounted on the application head  4 . In order to keep the mass inertia low, and to reduce the number of the moved components, the rotation axis r z  is arranged close to the patient. A person skilled in the art will understand that the rotation of the application head  4  about the rotation axis r z  can also be effected by means of a parallelogram guide, for example, with further hinges R z  being used for this purpose. 
     Although this is only shown schematically in  FIG. 1 , the opthalmological apparatus  1  in each case comprises a light source  21  (laser source) which is arranged in the base station  2  and generates light pulses, in particular a femtosecond laser for generating femtosecond laser pulses, and an optical transmission system  22  for transmitting the light pulses from the base station  2  through the support arm  3  to the application head  4 . The opthalmological apparatus  1  preferably also comprises a lock  32  for fixing or releasing a position of rotation of the application head  4  about the rotation axis r z , for example a friction coupling. 
     Beam-deflecting means  31  are inserted into the optical transmission system  22  and are designed to deflect the light pulses in at least two scanning directions. A scanner suitable for the beam-deflecting means  31  is described in EP 1731120, for example. Galvanoscanners or acousto-optic modulators are also suitable. The beam-deflecting means  31  are preferably arranged in the support arm  3  in order to minimize the distance to the application head  4 . The application head  4  comprises a light projector  41  with a lens system  42 ,  43  for focused projection of the light pulses into and/or onto the eye  6 , in order to effect a punctiform breakdown of the eye tissue. The deflected light pulses are transmitted onwards by the optical transmission system  22  via the beam-deflecting means  31  to the light projector  41 . The beam-deflecting means  31  and the light projector  41  are designed to scan a contiguous work area extending across the entire viewable region of the eye and to work with a focusing effect such that contiguous sections in the eye tissue, in particular in the cornea, can be cut. The beam-deflecting means  31  and the light projector  41  not only permit focused scanning of a plane work region, for example a horizontal work region, but, by targeted vertical positioning of the focus, also three-dimensionally defined work regions, for example vertical and curved sectional surfaces. 
     Although this is not shown in the figures, it should be noted that the application head  4  comprises a contact body which can be placed onto the eye  6 , is transparent to light at least in parts and is configured and arranged such that it sets a contacted area of the eye  6  preferably equidistant to a work surface, and has securing means for fixing the application head  4  to the eye  6  by underpressure. Contact bodies can be plane or spherical, for example. 
     As is shown schematically in  FIG. 7 , the application head  4 , in an embodiment variant that can be combined with  FIGS. 1-6 , has a feed part  4 A connected to the support arm  3 , and a projection part  4 B angled off from the feed part  4 A. In this embodiment variant, the light projector  41  comprises a first lens system  43  in the projection part  4 B and a second lens system  42  in the feed part  4 A. The first lens system  43  and the second lens system  42  are coupled via the deflecting mirror  45 . The application head  4  preferably also has a viewing window  44  permitting a top view of the eye  6  in the projection direction v. The viewing window  44  is designed, for example, such that the deflecting mirror  45  is transparent to light for the viewing wavelength. Reference number  47  designates coupling means, which are described in more detail below. 
     As is shown schematically in  FIG. 8 , the viewing window  44  permits optical coupling of optical viewing, imaging and measuring modules  5 , e.g. a recording camera with optional pivotable monitor, which are mounted, for example by way of a module support  51 , on the base station  2  so as to rotate about a vertically oriented rotation axis. These modules can thus be swivelled in and out over the application head  4 , and their optical axes can be oriented with respect to the optical projection axis v of the light projector  41 . The modules can additionally be mechanically connected to the application head  4  in a releasable manner via the coupling means  47 , for example a detachable snap-fit catch or a bayonet catch. 
     In an optional embodiment variant that can be combined with  FIGS. 1-8  and is shown schematically in  FIG. 9 , the projection part  43  is mounted pivotably on the feed part  42 . In the variant according to  FIG. 9 , the application head  4  has a hinge Rφ and the projection part  43  is rotatably connected with the angle φ about a longitudinal axis r φ  extending through the feed part  42 . The application head  4  additionally has a hinge R β  and the projection part  43  is rotatably connected to the feed part  42  with the angle β about a transverse axis r β  extending perpendicular to the longitudinal axis r φ . 
     In the embodiment variant according to  FIG. 1 , the support arm  3  is fixedly connected to the base station  2 , for example the base station  2  and the support arm  3  are designed in one piece as an overall unit with a common housing. In this variant, the mutual orientation of eye  6  and light projector  41 , i.e. the centering of the light projector  41  to the eye  6 , is effected by moving the patient&#39;s bed or the base station  2  in the x-direction and y-direction of a horizontal positioning plane (generally parallel to the ground surface on which the base station  2  is arranged). 
     In the embodiment variant according to  FIGS. 2 and 3 , the support arm  3  is connected movably to the base station  2  such that the support arm  3 , for orientation of the light projector  41  to the eye  6 , can be moved in translation in the x-direction and y-direction of a horizontal positioning plane relative to the base station  2 . The translatory movement is effected by means of translatory movement drivers or manually via corresponding guides. 
     In the embodiment variant according to  FIG. 4 , the support arm  3  is connected to the base station  2  via the hinge Ry. The hinge Ry permits a rotation y rot  of the support arm  3  about the vertical rotation axis r y . As is shown schematically in  FIG. 4 , the hinge Ry is arranged and configured such that, by the rotation y rot  of the support arm  3  about the rotation axis r y , a horizontal movement is permitted in the y-direction for orienting the light projector  41  to the eye  6 . The orientation of the light projector  41  in the x-direction is effected by means of translatory movement, as in  FIGS. 2 and 3 . 
     In the embodiment variant according to  FIG. 5 , the orientation of the light projector  41  is effected by rotation both in the x-direction and also in the y-direction. In the embodiment variant according to  FIG. 4 , the application head  4  is connected to that end of the support arm  3  directed away from the base station  2 , in particular also via the hinge R x . The hinge R x  permits a rotation x rot  of the application head  4  about the vertical axis r x . As is shown schematically in  FIG. 5 , the hinge R x  is arranged and configured such that, by the rotation x rot  of the application head  4  about the rotation axis r x , a horizontal movement in the x-direction is permitted for orienting the light projector  41  to the eye  6 . The orientation of the light projector  41  in the y-direction is effected by means of a rotary movement, as in  FIG. 4 . 
     In the embodiment variant according to  FIG. 6 , the orientation of the light projector  41  is effected by rotation both in the x-direction and also in the y-direction, as in  FIG. 5 . In the embodiment variant according to  FIG. 6 , however, the hinge R z  or rotation axis r z  is turned through 90° in relation to the arrangement according to  FIG. 5 . The movement in the x-direction is effected by a rotation x rot  of the support arm  3  about the vertical rotation axis r x  of the hinge R x , which connects the support arm  3  to the base station  2 . The movement in the y-direction is effected by a rotation y rot  of the application head  4  about the vertical axis r y  of the hinge Ry which connects the application head  4  to the support arm  3 . 
     The positioning means for the rotatory and/or translatory movement of the support arm  3  for horizontal orientation of the application head  4  and of the light projector  41  with translatory movements in the x-direction and y-direction and/or with rotary movements x rot  and y rot  can be configured for manual movement and/or by means of movement drivers. 
     Although this is only shown schematically in  FIG. 2 , the opthalmological apparatus  1  comprises weight compensation means  33  which are connected to the application head  4 , for example adjustable counter-weights or springs. The weight compensation means  33  are preferably configured such that they only partially balance out the masses rotating about the rotation axis r z , such that the application head  4  can be placed with a defined application force onto the eye  6 . 
     Although the figures and the above observations only concern embodiment variants in which the application head  4  for carrying out the vertical orientation in the z-direction is connected to the support arm  3  via the hinge R z , it should be noted here that the vertical orientation of the application head  4  in the z-direction can also be effected via a rotation movement of the support arm  3  about a horizontal rotation axis r z , if the support arm  3  is connected via a corresponding hinge R z  to the base station  2 , and the application head  4  is mounted fixedly on the support arm  3 . The horizontal orientation of the application head  4  or light projector  41  with translatory movements in the x-direction and y-direction and/or with rotary rotations x rot  and y rot  also takes place through the positioning means for the rotary and/or translatory movement of the support arm  3  in accordance with the above description. Depending on the arrangement of the positioning means for the rotary and/or translatory movement of the support arm  3 , the hinge R z  remains fixedly connected to the base station or moved along with it. 
     Although this is only shown schematically in  FIG. 1 , the opthalmological apparatus  1  additionally comprises a control unit  23  arranged in the base station  2 . The control unit  23  ensures that the beam-deflecting means  31  are not activated when the application head  4  is moved for placement onto the eye  6 . The control unit  23  is also designed for controlling the beam deflection and for controlling and monitoring the movement drivers. The control unit  23  additionally comprises safety functions for monitoring of forces, movements and beam parameters. 
     In one embodiment variant, the opthalmological apparatus  1  moreover comprises height-defining means  22  for determining a vertical position of the eye  6 , for example a camera, and the base station  2  comprises height-positioning means  24 , e.g. translatory movement drivers, for setting a vertical basic position of the base station  2  and of the associated support arm  3 . The height-positioning means  24  are controlled, for example, by the control unit  23  on the basis of a vertical position of the eye  6  determined by the height-defining means  22 . Manual setting of the basic position is also possible. By setting the basic position, the movement stroke required for the application head  4  can be reduced to 10-20 mm, for example.