Abstract:
A system and method are provided for fragmenting a crystalline lens, to facilitate its removal from the lens bag during an ophthalmic laser surgery. First, a predetermined pattern is used to make Laser Induced Optical Breakdown (LIOB) cuts that section the lens into asymmetrical, operational segments. At least one operational segment is then selected and softened with a plurality of compact LIOB cuts. Once softened, the selected segment is aspirated. The remaining operational segments are then subsequently removed. During a procedure, an imaging unit can monitor movements of the lens bag to ensure proper placement of the LIOB cuts on the lens.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/473,044, filed Apr. 7, 2011. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to ophthalmic surgery. More particularly, the present invention pertains to systems and methods for removing the lens from its lens bag during an ophthalmic surgical procedure. The present invention is particularly, but not exclusively, useful as a system and method for facilitating the removal of the lens by performing Laser Induced Optical Breakdown (LIOB) on the lens to fragment the lens prior to its removal from the lens bag. 
       BACKGROUND OF THE INVENTION 
       [0003]    In a typical lens removal procedure (i.e. a capsulotomy), the anterior portion of the lens bag that holds the crystalline lens of an eye is perforated to create a rhexis. The lens is then removed through the rhexis. In place of the removed lens, a prosthetic Intraocular Lens (IOL) is inserted into the lens bag. Two of the primary objectives of a lens removal procedure are that the implanted prosthetic IOL will function in the stead of the removed lens and that damage to the lens bag and other tissue in the eye will be substantially avoided, or at least minimized. 
         [0004]    Heretofore, one method commonly used for removing the lens from its lens bag has involved phacoemulsification of the lens. In such a procedure, ultrasound waves break down lens tissue, and after the tissue has been sufficiently broken down it is aspirated. The intraocular lens (IOL) is then inserted into the lens bag. 
         [0005]    Apart from phacoemulsification, it is also well known that lasers are very useful for altering lens tissue in the eye of a patient. More specifically, it is known that lens tissue can be effectively altered (i.e. photoablated) by a phenomenon that is widely referred to as Laser Induced Optical Breakdown (LIOB). An important result of LIOB is that very fine cuts through the tissue can be accomplished quickly. Moreover, these LIOB cuts can be made with great precision. A consequence of the ability of an LIOB procedure to cut into tissue is that due to the fineness of the cuts, and due to the ability to precisely control their placement, LIOB cuts can be made in compact patterns that will effectively pulverize lens tissue. 
         [0006]    When performing a capsulotomy, it is clearly advantageous to accomplish the procedure as quickly as possible. This requirement then leads to a need for minimizing the time that is necessary to prepare the lens for removal. Actual removal of the lens tissue from the bag will then be dependent on the size and location of the rhexis that is used for the procedure. 
         [0007]    In light of the above, it is an object of the present invention to provide a system and method for performing lens fragmentation with Laser Induced Optical Breakdown (LIOB) techniques that can be accomplished quickly, with great precision. Another object of the present invention is to effectively minimize the size of a rhexis that is required for the removal of a crystalline lens from its bag. Yet another object of the present invention is to provide a system and method for performing lens fragmentation which is simple to use, is easy to implement, and is relatively cost effective. 
       SUMMARY OF THE INVENTION 
       [0008]    In accordance with the present invention, a system and method for preparing the lens of an eye for removal from its lens bag during ophthalmic (cataract) surgery requires a computer controlled laser unit. Functionally, this unit performs Laser Induced Optical Breakdown (LIOB) in two different patterns of cuts that extend through the lens tissue of the eye. These patterns are a predetermined pattern that extends over the entire lens, and a defined pattern that is confined to a selected segment of the lens. 
         [0009]    Preparation of the lens is accomplished by first sectioning the lens tissue into operational segments. This is done by cutting the lens with a plurality of LIOB cuts that are arranged in the predetermined pattern. Typically, the predetermined pattern will be made up of radial cuts, ring cuts or a combination thereof that collectively section the lens into the desired operational segments. The present invention also envisions that the sectioning of the lens with the predetermined pattern can be accomplished by a partial dissection of tissue, such as by perforating the tissue. Importantly, in any case, the predetermined pattern of LIOB cuts does not effectively weaken the lens tissue. 
         [0010]    For the present invention, at least one, but possibly more, of the operational segments is (are) designated as a selected segment. This selected segment includes a targeted surface at which the laser unit is directed. Compact LIOB cuts are then made in the defined pattern within at least a portion of lens tissue in the selected segment. The objective of using this defined pattern of compact cuts is to soften (i.e. pulverize) lens tissue in the selected segment. Preferably, the selected segment will include somewhere between approximately 5% and 40% of the total lens tissue, by volume. Further, as a practical matter, the selected segment is typically a quadrant of the lens that extends generally from a defined axis of the eye to the periphery of the lens, and includes tissue between the anterior and the posterior surfaces of the lens. Thus, relative to the defined axis, the selected segment is asymmetrical. In any event, the consequence of the predetermined pattern and the subsequent defined pattern of cuts is that the lens is prepared to be more easily accessed and manipulated inside the lens bag for removal of the lens from the lens bag. 
         [0011]    Structurally, the system of the present invention includes the above-mentioned laser unit for generating a pulsed laser beam. And, it includes a computer that is electronically connected to the laser unit. Within this structure, a computer program is used for guiding the focal point of the laser beam. Further, the system also preferably includes an aspirator and an irrigator that work together for removing lens tissue from the lens bag, and may be included as parts of the same device. In addition, the lens tissue can be removed from the lens bag with the help of low power phacoemulsification as required. Additionally, an important aspect of the present invention is the use of a probe, or some similar means, for moving the lens in the lens bag during aspiration of the lens. Specifically, this manipulation facilitates the aspiration of lens tissue from the lens bag. As envisioned for the system of the present invention, after the lens has been prepared with the predetermined and defined patterns of LIOB cuts, the actual removal of lens tissue from the lens bag can be accomplished either manually by the surgeon or by using robotics. When the system uses robotics, the surgeon inputs commands into a robotic interface device connected to the computer. These commands are then used to control the aspirator, the irrigator, and the probe. 
         [0012]    In addition to the above, the system may also include an imaging unit for creating an image of the eye. When an imaging unit is used, the resultant image is sent to the computer where it is used for selecting appropriate predetermined and defined patterns for the LIOB cuts. In each case, subject to an override function by the operator, the selections of the predetermined and defined patterns can be accomplished by the computer. Furthermore, these selections are made according to parameters such as: 1) optical characteristics of the lens; 2) the size of the lens; and 3) the shape of the lens. Typically, relative to an axis defined by the lens (e.g. the visual axis or another axis of the eye), the predetermined pattern of LIOB cuts will preferably be either a plurality of radial cuts extending outwardly from the axis, a plurality of ring cuts substantially centered on the axis, or a combination of the two. On the other hand, the defined pattern of compact LIOB cuts will typically be a selection of line cuts, cube cuts, statistically arbitrary cuts, sphere-like cuts, wave cuts, polygonal cuts, radial cuts, arc cuts, combinations of these or any cut that can be described by an expansion series. 
         [0013]    A further purpose for the imaging unit is to detect movement of the lens in the lens bag during the procedure. This is accomplished by using the imaging unit to produce an initial image of the lens bag prior to any type of LIOB cuts being performed. Subsequently, upon the initiation of compact LIOB cuts, an actual image is produced in real-time by the imaging device. The initial image and the actual image are then compared to each other by the computer. Any difference between the initial image and the actual image is indicative of an unwanted movement of the lens in the lens bag. When a difference is detected, the computer will then realign the laser unit to minimize or compensate for the difference. Thus, the system ensures that the focal point of the laser beam follows the path required to produce the predetermined path and the defined path. 
         [0014]    In operation, a method for preparing the lens of an eye for removal from its lens bag requires sectioning the lens with a predetermined pattern of Laser Induced Optical Breakdown (LIOB) cuts. As mentioned above, this sections the lens into a plurality of operational segments. Next, compact LIOB cuts are made in a defined pattern on tissue in a selected segment of the lens. Furthermore, it is envisioned that the defined pattern may not necessarily cover the entire selected segment. As mentioned above, during the creation of the compact LIOB cuts, the computer is constantly monitoring the position of the lens bag to confirm that no displacement of the lens bag has occurred. 
         [0015]    Once lens tissue in the selected segment has been softened, it can then be easily accessed and aspirated to remove the softened lens tissue from the lens bag. Importantly, this aspiration (i.e. removal) can be accomplished while the lens bag is irrigated. As envisioned for the present invention, further aspiration is done in a particular sequence. First, at least a portion of the softened lens tissue in the selected segment is removed from the lens bag. Next, un-softened tissue from outside the selected segment (i.e. remaining operational segments) is removed. Further, as tissue is aspirated from the selected segment, a probe can be inserted into the lens bag and used to turn the lens inside the lens bag to facilitate tissue removal from the bag. Specifically, this is done to reposition the lens for ease in aspirating lens tissue from the lens bag. 
         [0016]    It will be appreciated by the skilled artisan that, in addition to ophthalmic applications, the methodologies disclosed for the present invention are also applicable to procedures involving a wide variety of different transparent materials. In these applications, it is envisioned that a computer-controlled laser unit will be employed. In general, the present invention envisions the use of a computer program product that will control the laser beam during the preparation of a transparent material for removal from a bag. Such a computer program product will typically include program sections for: using the laser beam to create an opening in the bag; sectioning the transparent material, in situ, into a plurality of operational segments, with Laser Induced Optical Breakdown (LIOB) cuts into the transparent material; selecting at least one asymmetrically oriented operational segment of the transparent material; creating compact LIOB cuts into the selected segment to soften transparent material in the selected segment; removing the softened selected segment from the bag; and subsequently removing any remaining operational segments from the bag. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    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: 
           [0018]      FIG. 1  is a schematic diagram of components for the system of the present invention shown in an operational environment; 
           [0019]      FIG. 2A  is a top view of the lens of an eye as seen along the line  2 - 2  in  FIG. 1 ; 
           [0020]      FIG. 2B  is a view of the lens as seen in  FIG. 2A  with a composite of predetermined patterns; 
           [0021]      FIGS. 3A-F  are views of the lens as shown in  FIG. 2A , with different defined patterns of LIOB cuts shown in a selected segment of the lens. Respectively, these defined patterns are: line cuts ( FIG. 3A ), cube cuts ( FIG. 3B ), sphere-like cuts ( FIG. 3C ), statistically arbitrary cuts ( FIG. 3D ), wave cuts ( FIG. 3E ), and polygonal cuts ( FIG. 3F ); 
           [0022]      FIG. 4  is a cross sectional view of the lens as seen along the line  4 - 4  in  FIG. 2B  showing disk layer cuts oriented perpendicular to an axis defined by the lens; 
           [0023]      FIGS. 5A-D  show a sequence of operational steps for aspirating softened lens tissue from a lens bag in accordance with the present invention; and 
           [0024]      FIG. 6  is a flow chart of an operation of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0025]    Referring initially to  FIG. 1 , a system for performing lens fragmentation during ophthalmic laser surgery is shown and is generally designated  10 . As shown, the system  10  includes a laser unit  12  for performing Laser Induced Optical Breakdown (LIOB) on an eye  14  of a patient (not shown). Further, system  10  also includes a computer  16  for controlling the laser unit  12 , and it includes an imaging unit  18  for producing an image of the eye  14  for use in planning and performing the lens fragmentation procedure. 
         [0026]      FIG. 1  also indicates that the computer  16  includes a robotic interface device  20  that is selectively employed to allow the system  10  to be operated robotically. In detail, the robotic interface device  20  provides input commands for the computer  16  to collectively control: an aspirator  22 , an irrigator  24 , and a probe  26 . As shown in  FIG. 1 , these three components are used to manipulate a lens  28  of the eye  14  during the lens fragmentation procedure. 
         [0027]    Referring now to  FIG. 2A , a top view of the lens  28  of the eye  14  is shown as it has been sectioned into a plurality of operational segments  32   a - d . In this exemplary illustration, each operational segment  32   a - d  is essentially a quadrant of the lens  28 . Other configurations for the operational segments  32   a - d  can, however, also be used to accomplish the purposes of the present invention. To section the lens  28  in the manner shown in  FIG. 2A , the laser unit  12  makes a plurality of LIOB cuts through the lens  28  in a predetermined pattern. In this case, illustrated in  FIG. 2A , the predetermined pattern has been created using a plurality of radial cuts  34   a - d  that each extends from an axis  36  to the outer periphery  38  of the lens  28 . In  FIG. 2A , for purposes of disclosure only, the operational segment  32   b  is shown shaded in order to identify it as a selected segment  40 . As a selected segment  40 , it will eventually be cut by a plurality of compact LIOB cuts  41   a - f  (see  FIGS. 3A-3F ). Moreover, as shown, the selected segment  40  is preferably offset, and is therefore an asymmetric portion of the lens  28 . 
         [0028]      FIG. 2B  illustrates alternative methods for sectioning the lens  28 . For example, a predetermined pattern can be used by the laser unit  12  to create both a plurality of ring cuts  42 , of which cuts  42   a - b  are exemplary, and a plurality of radial cuts  43 , of which cuts  43   a - b  are exemplary. In the event, the ring cuts  42 , together with the radial cuts  43 , create a plurality of contiguous operational segments  45  (of which the operational segments  45   a - c  shown in  FIG. 2B  are exemplary). The operational segments  45   a - c  are then chosen to collectively form a selected segment  47 . 
         [0029]    Referring collectively to  FIGS. 3A-3F , six views of the lens  28  of  FIG. 2A  are shown with each having a different defined pattern of compact LIOB cuts  41  in the selected segment  40  of the lens  28 . By way of example, these views show the following types of compact LIOB cuts  41   a - f , respectively: line cuts ( FIG. 3A ), cube cuts ( FIG. 3B ), sphere-like cuts ( FIG. 3C ), statistically arbitrary cuts ( FIG. 3D ), wave cuts ( FIG. 3E ), and polygonal cuts ( FIG. 3F ). It will also be appreciated that a combination of any of the cuts in the defined patterns shown in  FIGS. 3A-3F  can also be used to establish the defined pattern for the system  10 . Further, as shown in  FIG. 4 , a plurality of disk, layer cuts  44   a - c  can be oriented perpendicular to the axis  36  inside the lens  28  to help soften tissue in the lens  28 . These disk layer cuts  44   a - c  can be made in place of, or in conjunction with, a selected compact LIOB cut  41  to create the defined pattern as disclosed above. 
         [0030]    With reference to  FIGS. 5A-5D , a sequence of operational steps for aspirating softened lens tissue from the lens bag  30  in accordance with the present invention is shown. To begin the aspiration of the lens  28 , and as shown in  FIG. 5A , the aspirator  22  is inserted into the lens bag  30 . It should be noted that the aspirator  22  can serve a dual-purpose and can be configured to act as both the aspirator  22  and the irrigator  24  for the system  10  when required. It can be seen that the aspirator  22  in  FIG. 5A  is initially used to aspirate softened tissue from the selected segment  40  of the lens  28 . After the selected segment  40  has been effectively aspirated, tissue of the remaining operational segments  32   a ,  32   c  and  32   d  are then aspirated. During a procedure, the probe  26  is used to rotate the lens  28  in the direction of arrow  46  as shown in  FIGS. 5B and 5C . The purpose of rotating the lens  28  is two-fold. For one, additional tissue is moved closer to the aspirator  22  to facilitate aspiration. For another, moving the lens  28  allows the aspirator  22  to remain stationary, which lessens the chance of the aspirator  22  damaging the lens bag  30  or other tissue in the eye  14 . This process of aspirating and rotating occurs as shown in  FIG. 5C  until the lens  28  is completely removed from the lens bag  30  (see  FIG. 5D ). Throughout the aspiration process detailed here, the lens bag  30  may also be irrigated as required. Also, hydrodissection may or may not be performed prior to turning. 
         [0031]    An operation of the present invention can be described using the flow chart shown in  FIG. 6 . To commence an operation, the imaging unit  18  creates an initial image of the lens bag  30  as shown in action block  48 . This image can serve several purposes. For one, the image can be used to establish the initial position of the lens bag  30 . For another, it can serve to orient the predetermined pattern for sectioning the lens  28 . Also, it can be used to identify the selected segment  40  of the lens  28 . After this initial image is created, the lens  28  is sectioned into operational segments  32  at action block  50 , and a segment is selected to be targeted for compact LIOB cuts as indicated by action block  52 . Next, the laser unit  12  creates the compact LIOB cuts in the selected segment  40  of the lens  28  as shown in action block  54 . 
         [0032]    An important consideration when directing the laser unit  12  to the selected segment  40  is ensuring that the lens bag  30  remains in its initial position. In doing so, the system  10  ensures that a defined pattern of LIOB cuts  41  alters the intended target in the lens tissue. Consequently, immediately upon the commencement of the compact LIOB cuts  41 , the imaging unit  18  begins to monitor the lens bag  30  for the purpose of detecting any displacement or movement thereof as shown in action block  56 . For accomplishing this monitoring step, the imaging unit  18  continuously produces a real-time image of the lens bag  30 . This real-time image and the actual image are then used by the computer  16  to detect movement of the lens bag  30  as shown in inquiry block  58 . At this point, the computer  16  determines whether the lens bag  30  has moved. If the lens bag  30  has moved, the computer  16  realigns the laser unit  12  as shown in action block  60 . Then, once the laser unit  12  is realigned to target the selected segment  40 , compact LIOB cuts  41  are again created in the selected segment  40  at action block  54 . 
         [0033]    In the case where inquiry block  58  determines the lens bag  30  does not move, inquiry block  62  illustrates that a determination is made as to whether additional compact LIOB cuts are required. If additional cuts are required, more cuts are created by the system  10  returning to action block  54 . When additional cuts are not required, the selected segment  40  is aspirated at action block  64 . Once the selected segment  40  is aspirated, the remaining operational segments  32  are aspirated as indicated by action block  66 . During the aspiration of the remaining operational segments  32 , the system  10  determines whether additional compact LIOB cuts  41  are required to continue the aspiration at inquiry block  68 . If additional compact LIOB cuts are required, the system  10  directs the laser unit  12  to create additional cuts with a return to action block  54 . If additional cuts are not required, the system  10  determines whether aspiration of the lens  28  is complete at inquiry block  70 . If aspiration is not complete at inquiry block  70 , then the lens  28  can be turned using the probe  26  at action block  72 . This allows the aspirator  22  to remain stationary and to continue aspirating the lens  28  at action block  74 . 
         [0034]    When the system  10  indicates that the aspiration of the lens  28  is complete at inquiry block  70  after the lens  28  has been turned, the removal of the lens  28  is complete and the operation of the system  10  ends as indicated by action block  76 . 
         [0035]    While the particular System and Method for Performing Lens Fragmentation 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.