Abstract:
A system for performing a corneal transplantation includes a laser source for generating a laser beam and a chair for positioning a patient relative to the laser source. A stabilizing element, engageable with the laser source, is fixated on the anterior surface of the patient&#39;s cornea to hold the cornea in alignment with the laser source. The laser source is then used to remove diseased tissue from the cornea of the patient, thereby creating a corneal cavity of known dimensions. In a subsequent step, a donor graft that was previously photoaltered to have substantially the same dimensions as the corneal cavity, is transplanted into the corneal cavity.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention pertains generally to systems and methods for performing ophthalmic laser surgery. More particularly, the present invention pertains to surgical procedures for performing a corneal transplantation wherein a donor graft and the cavity in the cornea of a patient for receiving the graft have the same dimensions. The present invention is particularly, but not exclusively, useful as a system for using a laser source to create a corneal cavity and a donor graft having a same geometry.  
       BACKGROUND OF THE INVENTION  
       [0002]     A corneal transplantation procedure (keratoplasty) involves replacing the diseased or damaged tissue of a patient&#39;s cornea with a graft of healthy tissue that is taken from a donor cornea. In such a procedure, it is obviously desirable that the donor graft be as near the same size and shape as the volume of tissue that is being replaced. It happens, however, that corneal transplantation procedures do not routinely achieve this objective.  
         [0003]     Corneal transplantation procedures have been generally performed using either a knife or some form of laser procedure to prepare the patient&#39;s cornea and create a donor graft. Heretofore, regardless how the procedure has been performed, several factors have conspired to complicate matters. In particular, for procedures wherein a knife (e.g. a trephine) has been used to prepare a patient&#39;s cornea for a corneal transplantation, two issues commonly arise. First, the proper positioning and stabilization of the patient&#39;s eye during the procedure has always been difficult. Indeed, in such procedures it is typically necessary for the eye to be physically grasped (e.g. use of forceps) in order to achieve the required stabilization. Second, during the cutting of the cornea with a knife, pressures induced by the cutting can cause decentration of the eye to occur. The resultant irregular or poorly defined cutting edges can then adversely affect the subsequent healing process and the resultant quality of vision. On the other hand, although the use of laser systems may obviate the adverse effects otherwise caused by unwanted pressures on the eye, the problems of positioning and stabilizing the eye still persist. Thus, in either case, the geometry of the corneal cavity that is prepared to receive the donor graft may be imprecise.  
         [0004]     In addition to the difficulties noted above that are encountered while creating a cavity in the cornea of a patient, there is also the problem of creating a donor graft that will have the precise dimensions required to match those of the cavity. In an effort to address this issue for laser procedures, it has been proposed that complimentary masks be made for use with an excimer laser. Specifically, in this case, one mask can be used to create the cavity in the recipient cornea, while its compliment is used to create the graft in the donor cornea. A problem here, however, is the two different mechanical contrivances are used in two separate operations. Further, the stabilization and positioning issues that are inevitably encountered, are not adequately addressed.  
         [0005]     In light of the above, it is an objective of the present invention to provide a system and method for performing a corneal transplantation wherein a cavity in the cornea of the patient and the graft from a donor cornea are created using a same laser surgical unit and a same cutting geometry. Another object of the present invention is to provide a system and method for performing a corneal transplantation wherein the cornea of the patient and the donor cornea are each aligned with the surgical laser unit, in the same way during a laser cutting procedure. Still another object of the present invention is to provide a system and method for performing a corneal transplantation that is easy to use, relatively simple to manufacture, and comparatively cost effective.  
       SUMMARY OF THE INVENTION  
       [0006]     A system for performing a corneal transplantation includes a stationary surgical laser unit having a laser source for directing a laser beam along a beam path. Preferably, the laser beam is an ultra-short pulse laser beam. Additionally, the system of the present invention includes a motorized chair for separately positioning the cornea of a patient and a donor cornea, relative to the laser source. Further, a computer controller is in electronic communication with the motorized chair for moving and reconfiguring the chair.  
         [0007]     As contemplated by the present invention, the system includes a mount for holding the donor cornea secure during the corneal transplantation procedure. In one embodiment of the present invention, the mount is configured to hold an entire donor eye, which includes the donor cornea. Alternatively, the mount holds only the donor cornea and the scleral rim of the donor eye. In this alternate embodiment, an artificial anterior chamber is attached to the mount and used to hold the donor cornea and scleral rim secure in the mount. Structurally, the mount is attached to a platform adapter which, in turn, may be mounted on the motorized chair.  
         [0008]     In addition to the mount disclosed above, the system includes a stabilizing element of a type as disclosed in co-pending U.S. patent application Ser. No. 10/790,625, which is assigned to the same assignee as the present invention. Importantly, depending on the application, the stabilizing element includes a lens having either an applanating surface or a surface that substantially conforms with the anterior surface of the cornea of the patient. Additionally, the stabilizing element is formed with a vacuum fitting for fixating the stabilizing element to either the cornea of the patient or to the cornea of the donor eye. Along with the stabilizing element, the system of the present invention may include an alignment device which is mounted on the surgical laser unit and is engageable with the stabilizing element. With this interconnection the stabilizing element is aligned with the laser source.  
         [0009]     In an alternate embodiment of the present invention, instead of the alignment device and stabilizing element, the system can include an optical assembly for measuring an x-y and a z-position of the donor cornea. Again, the purpose is to align the donor cornea with the surgical laser unit. Structurally, the optical assembly includes an eye tracker for measuring the x-y position of the donor cornea, in accordance with a predetermined orthogonal coordinate system. Additionally, the optical assembly also includes any device, well known in the pertinent art, for measuring the z-position of the donor cornea. For example, the device for measuring the z-position of the cornea may be either a Hartmann-Shack sensor or a confocal microscope.  
         [0010]     Preferably, in the operation of the present invention, a donor graft is prepared first and then a cavity for receipt of a donor graft is cut into the cornea of the patient. The dimensions and shape of the cavity are essentially the same as for the donor graft and are well defined. To facilitate the laser cutting of the cornea of the patient, the patient is seated in the chair. Further, the alignment device is mounted or positioned on the surgical laser unit. After the patient is seated in the chair, the motorized chair is moved to generally align the eye of the patient with the surgical laser unit. Once the eye has been generally aligned with the surgical laser unit, the stabilizing element is placed on the anterior surface of the patient&#39;s cornea. With the stabilizing element in place, the vacuum device is connected to the stabilizing element, after which the vacuum device is activated. In particular, a vacuum pump is used to create a suction force between the surface of the lens of the stabilizing element and the anterior surface of the cornea. As contemplated by the present invention, the suction force holds the stabilizing element immovable against the eye of the patient.  
         [0011]     With the stabilizing element held on the eye of the patient, the chair is reconfigured to move the stabilizing element into an engagement with the alignment device. Once the stabilizing element and alignment device are properly engaged, the eye of the patient is aligned with the laser source. Preferably, the second vacuum device is then activated to create a suction force that maintains the engagement of the stabilizing element with the alignment device. Following the engagement of the stabilizing element and the alignment device, the laser beam is used to remove diseased tissue from the patient&#39;s cornea, thereby creating a corneal cavity according to a pre-determined cutting pattern. Specifically, in this operation, the focal point of the laser beam is moved along a predetermined path in the cornea to create a cavity having a specific dimensional configuration. Once the cavity has been created, the engagement between the stabilizing element and the alignment device is terminated, and the patient is moved away from the laser source. The stabilizing element is then removed from the eye of the patient.  
         [0012]     Prior to, and in preparation for creating the cavity as disclosed above, the mount is attached to the platform adapter, and the adapter is mounted on the motorized chair. Further, a donor cornea is secured in the mount. As contemplated by the present invention, a stabilizing element is placed on the anterior surface of the donor cornea. Subsequently, the vacuum device is used to fixate the stabilizing element to the donor cornea. It can be appreciated that by using a stabilizing element of the same shape for both the donor cornea and the cornea of the patient, the conformed shapes of the two corneas during photoalteration can be made nearly or substantially the same. In this way, it is possible to ensure that the size and shape of the donor graft precisely matches the size and shape of the corneal cavity.  
         [0013]     According to commands sent by the computer controller, the motorized chair is moved to once again engage the stabilizing element with the alignment device. When the eye stabilizing element and alignment device are properly engaged, the donor cornea is aligned with the laser source and a donor graft is cut. Importantly, the cutting pattern for the donor graft generates a graft having a dimensional configuration with dimensions and a shape that will match that of the corneal cavity. Once the donor graft has been cut, the motorized chair is moved away from the laser source, and the stabilizing element is removed from the donor cornea. After the stabilizing element is removed, the donor graft is subsequently placed in an apparatus for transferring the donor graft to the cornea of the patient.  
         [0014]     In an alternate embodiment of the present invention, the optical assembly is used to measure the x-y and z-position of the donor cornea prior to creating the donor graft. In this embodiment, neither the stabilizing element nor the alignment device are required. Specifically, the mount is attached to the chair, and the donor cornea is secured in the mount as described above. The motorized chair is then moved to generally align the donor cornea with the laser source. During the alignment procedure, a system operator views the donor cornea through a microscope mounted on the surgical laser unit. Once the system operator determines that the eye is generally aligned with the laser source, the eye tracker is used to measure the x-y position of the donor cornea, according to the predefined orthogonal coordinate system. Additionally, the Hartmann-Shack sensor, or a confocal microscope, measures the z-position of the donor cornea. Once all of the measurements have been taken, the x-y and z-position data is transmitted to the computer controller for processing. Once processed, the data is used by the computer controller to precisely align the laser source with the donor cornea prior to the cutting of the donor graft. Once again, a donor graft having dimensions and a shape precisely matching that of the corneal cavity is cut using a predefined cutting pattern. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0016]      FIG. 1  is a schematic view of a system, in accordance with the present invention, for performing a corneal transplantation;  
         [0017]      FIG. 2  is a schematic view of a donor eye positioned in a mount, for presentation of a donor cornea for photoalteration;  
         [0018]      FIG. 3  is schematic view of an alternate embodiment of the present invention, for measuring the x-y and z-position of a donor cornea prior to photoalteration of the donor cornea;  
         [0019]      FIG. 4A  is a perspective view of a cavity in a recipient cornea; and  
         [0020]      FIG. 4B  is a perspective view of a donor graft cut from a donor cornea for placement in the corneal cavity cut in the cornea of the patient and shown in  FIG. 4A .  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     A system for performing corneal transplantations, in accordance with the present invention, is shown in  FIG. 1  and is generally designated  10 . As shown, the system  10  includes a stationary surgical laser unit  12 , which further comprises a laser source  14  for directing a laser beam  16  along a beam path  18 . Preferably, the laser beam  16  is an ultra-short pulse laser beam  16  having a wavelength in the range of about 400 nm to 10 μm. Further, the laser beam  16  has a pulse duration in the range of 1 femtosecond to 100 picoseconds, a pulse repetition rate of about 1 to 1000 kHz, and a pulse energy between about 0.1 microjoule and 1 millijoule. Also, it is to be appreciated that an oscillator laser without an additional amplifier can be used. If so, pulse repetition rates of up to 100 MHz can be achieved with pulse energies in a range of 0.1 nanojoule to 10 microjoules.  
         [0022]     In addition to the laser source  14 , the system  10  includes a platform  20  for supporting a patient  22 , and for positioning an eye  24  of the patient  22  relative to the laser source  14 . As contemplated by the present invention, the platform  20  may also be used to position a donor cornea  26  ( FIG. 2 ) relative to the laser source  14 . In the preferred embodiment of the present invention, the platform  20  is a chair that includes a motorized control assembly  28  which can be selectively activated to move and reconfigure the chair  20 . A computer controller  30 , which has a graphical user interface  32 , is in electronic communication with the motorized control assembly  28  for directing the movement of the chair  20 . Specifically, an electrical cable  34  interconnects the computer controller  30  and the motorized control assembly  28 . Additionally, the computer controller  30  is in electronic communication with the surgical laser unit  12  for controlling the settings, timing and functioning of the unit  12 . As shown, an electrical cable  36  connects the computer controller  30  to the surgical laser unit  12 .  
         [0023]     As can be seen in  FIG. 1 , the system  10  includes a mount  38  for holding the donor cornea  26 . The mount  38 , in turn, is affixed to a platform adapter  39 , which can be mounted on the chair  20 . As can be seen in  FIG. 2 , the mount  38  can be configured to hold an entire donor eye  40  which includes the donor cornea  26 . Additionally, the mount  38  may include an artificial anterior chamber (not shown). Operationally, the artificial anterior chamber is used to secure only the donor cornea  26  and the scleral rim (not shown) of the donor eye  40  in the mount  38 .  
         [0024]     Cross-referencing  FIGS. 1 and 2 , it can be seen that the system  10  of the present invention includes a stabilizing element  42 . As can be seen in  FIG. 2 , the stabilizing element  42  includes a lens  44 . Importantly, the surface  43  of the lens  44  conforms substantially with the anterior surface of the donor cornea  26  and the cornea  45  of the patient  22 . As contemplated by the present invention, the system  10  further includes a vacuum device  46  in fluid communication with a vacuum fitting  47  formed in the stabilizing element  42 . More specifically, a vacuum pump  48  is connected to the vacuum fitting  47  via a vacuum line  50 .  
         [0025]     Still cross referencing  FIGS. 1 and 2 , the system  10  of the present invention includes an alignment device  52  that is mounted or positioned on the surgical laser unit  12  for engagement with the stabilizing element  42 . Specifically, the alignment device  52  may be mounted on the surgical laser unit  12 , or the alignment device  52  may be integral to the surgical laser unit  12 . Further, as shown, the system  10  includes a vacuum device  54  for maintaining an engagement between the stabilizing element  42  and the alignment device  52 , once the two are engaged. Specifically, the vacuum device  54  includes a vacuum pump  56  in fluid communication with a vacuum line  58 , which in turn is connected to a vacuum fitting  59  formed in the alignment device  52 .  
         [0026]     In an alternate embodiment of the present invention, as shown in  FIG. 3 , the system  10  of the present invention includes an optical assembly  60  for measuring the x-y and z-position of the donor cornea  26 . Specifically, the optical assembly  60  includes an eye tracker  62 , of a type well known in the pertinent art, for measuring the x-y position of the donor cornea  26 . Additionally, the z-position of the donor cornea  26  is measured using a Hartmann-Shack sensor  64  or a confocal detector (not shown).  
         [0027]     In the operation of the present invention, a donor graft  68  is prepared and the patient  22  is then positioned in the chair  20  and the stabilizing element  42  is placed on the eye  24  of the patient  22 . More specifically, the surface  43  of the lens  44  of the stabilizing element  42  interfaces with the anterior surface of the cornea  45  of the eye  24  of the patient  22 . Following commands from the system operator (not shown), the computer controller  30  then directs the motorized control assembly  28  to move and reconfigure the chair  20 . Specifically, the chair  20  is moved to generally align the eye  24  of the patient  22  with the stationary surgical laser unit  12 . If not already connected, the vacuum line  50  is then connected to both the vacuum fitting  47  of the stabilizing element  42  and to the vacuum pump  48 . When activated, the vacuum pump  48  evacuates air from the stabilizing element  42 . Consequently, a suction force is created at the interface of the surface  43  of the lens  44  and the anterior surface of the cornea  45  of the eye  24 . As envisioned by the present invention, the suction force holds the stabilizing element  42  immovable against the eye  24 .  
         [0028]     Along with the stabilizing element  42  being placed and held on the eye  24  of the patient  22 , the alignment device  52  is mounted, as necessary, on the surgical laser unit  12 . Once the alignment device  52  is mounted on the surgical laser unit  12 , the chair  20  is moved through a “docking” procedure whereby the stabilizing element  42  is moved to engage with the alignment device  52 . When the stabilizing element  42  is properly engaged with the alignment device  52 , the eye  24  of the patient  22  is aligned with the surgical laser unit  12 . In addition, the eye  24  is positioned at a known distance from the surgical laser unit  12 . Thus, when the stabilizing element  42  is engaged with the alignment device  52 , the lens  44  and cornea  45  of the eye  24  are a known distance from the cutting lenses (not shown) of the surgical laser unit  12 . To ensure that the stabilizing element  42  remains fixedly engaged with the alignment device  52 , the vacuum pump  56  is activated to create a suction force whereby the stabilizing element  42  is drawn against the alignment device  52 . Once the cornea  45  of the eye  24  of the patient  22  is properly aligned with the laser source  14 , the cornea  45  of the eye  24  can be photoaltered to remove diseased tissue from the cornea  45 . As can be appreciated by the skilled artisan, removal of diseased tissue creates a cavity for receipt of a donor graft. Referring now to  FIG. 4A , it can be seen that a cavity  66  of precise dimensions, of which l 1 , d 1 , h 1  and θ 1  are only exemplary, is cut by the laser beam  16 . The donor graft  68  can now be positioned in the cavity  66  in the cornea  45  of the patient  22 .  
         [0029]     To create the donor graft  68 , for subsequent insertion into the cavity  66 , a donor eye  40  is positioned in the mount  38  and the mount  38  is attached to the platform adapter  39 , as shown in  FIG. 2 . The platform adapter  39  is then mounted on the chair  20 . Once the mount  38  is attached to the adapter  39 , the stabilizing element  42  is placed on the anterior surface of the donor cornea  26 . By using a stabilizing element  42  having a same shape with both the donor cornea  26  and the cornea  45  of the patient  22 , the anterior surfaces of both corneas  26  and  45  are similarly shaped by the respective lens  44  during photoalteration of the corneas  26  and  45 . As such, it is possible to ensure that the size and shape of the donor graft  68  can precisely match the size and shape of the corneal cavity  66 . On the other hand, it may be desirable for the donor graft  68  to be customized by the laser (e.g. a slightly larger donor graft  68 ). In any event, once the stabilizing element  42  is positioned, the vacuum device  46  is employed once again to fixate the stabilizing element  42  to the donor cornea  26 .  
         [0030]     According to commands sent by the computer controller  30 , the motorized chair  20  is moved to once again engage the stabilizing element  42  with the alignment device  52 . When the stabilizing element  42  and alignment device  52  are properly engaged, as shown in  FIG. 2 , the donor cornea  26  is aligned with the laser source  14 . Consistent with the procedure that will be subsequently used to create the cavity  66  in the cornea  45  of the patient  22 , the vacuum device  54  is employed to maintain the engagement between the stabilizing element  42  and the alignment device  52 . Once the donor cornea  26  is properly aligned with the laser source  14 , a donor graft  68  is cut from the donor cornea  26  (see  FIG. 4B ). After the donor graft  68  is cut, the graft  68  is placed in an apparatus (not shown) for transferring the donor graft  68  into the corneal cavity  66 . It is an important aspect of the present invention that the dimensions of the donor graft  68  can be substantially the same as the dimensions of the cavity  66  created in the cornea  45  of the patient  22 . As indicated above, however, there is flexibility here for the surgeon to customize the size of the donor graft  68 . Referring once again to  FIG. 4A , it can be appreciated, for example, that l 1 =l 2 , w 1 =w 2 , d 1 =d 2  and θ 1 =θ 2 . It should be understood that all of the critical dimensions of the cavity  66  ( FIG. 4A ) can be substantially the same or slightly smaller than the critical dimensions of the donor graft  68  ( FIG. 4B ). In this way, the donor graft  68  will fit snugly and precisely within the volume of the cavity  66 , thereby aiding the healing process and improving the refractive outcome of the surgery.  
         [0031]     Once the cutting of the donor graft  68  is complete, the motorized chair  20  is moved away from the laser source  14 , and the stabilizing element  42  is removed from the donor cornea  26 . In a subsequent surgical procedure, the donor graft  68  is positioned in the cavity  66  created in the cornea  45  of the patient  22 .  
         [0032]     In an alternate embodiment of the present invention, the donor cornea  26  is secured in the mount  38  as disclosed above. The chair  20  is then moved and reconfigured to generally align the donor cornea  26  with the laser source  14 . As the chair  20  is moving to align the donor cornea  26 , the system operator observes the donor cornea  26  through a microscope  70  ( FIG. 3 ) mounted on the surgical laser unit  12 . During this procedure, the image of the donor cornea  26  is presented to the system operator on the graphical user interface  32 . Using the images presented, the system operator generally aligns the donor cornea  26  with the laser source  14 . Once the donor cornea  26  is generally aligned, the optical assembly  60  measures the x-y and z-position of the donor cornea  26 , relative to a predefined orthogonal coordinate system  72  ( FIG. 3 ). More specifically, the x-y position of the donor cornea  26  is measured along an x-y plane  74  which is substantially perpendicular to the beam path  18 . Additionally, the z-position of the donor cornea  26  is measured along a z-axis  76  which is coincident with the beam path  18 . The eye tracker  62  measures the x-y position of the donor cornea  26 , and a device such as a Hartmann-Shack sensor  64  or a confocal detector (not shown) measures the z-position of the cornea  26 . At the completion of all measurements, the measurement data is communicated electronically to the computer controller  30  via the electrical cable  36 , wherein the data is used to align the laser beam  16  with the donor cornea  26 . Following this alignment, the donor graft  68  is cut. As described above, the donor graft  68  is then positioned in the cavity  66  previously created in the cornea  45  of the patient  22 .  
         [0033]     While the particular System for Performing a Corneal Transplantation as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.