Abstract:
A comprehensive multi-mode system for performing ophthalmic laser surgery on selected tissue inside an eye includes a laser unit for generating and focusing a laser beam to perform Laser Induced Optical Breakdown (LIOB) at a focal point in selected tissue. Also included is a selector for defining an operational mode according to characteristics of the tissue to be altered by LIOB. In combination, the operational mode specifies value ranges for configuration parameters for a pulsed femtosecond laser beam, establishes a base reference datum in the eye, and identifies a scanning procedure for the focal point of the laser beam to customize the system for a particular surgical procedure. A computer that is connected to the laser unit is responsive to the selector for implementing the operational mode.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to laser systems for performing ophthalmic laser surgeries. More particularly, the present invention pertains to laser systems that can be customized to perform a particular surgical laser procedure on a specifically identified ophthalmic tissue. The present invention is particularly, but not exclusively, useful as a system and method for customizing a same laser system to selectively perform different ophthalmic surgeries by specifying a laser beam configuration, establishing a base reference datum for the system, and identifying a scanning mode for each particular surgical procedure. 
     BACKGROUND OF THE INVENTION 
     Any ophthalmic laser surgical procedure requires a combination of precision, accuracy and efficacy that must be maintained within the range of the operational capabilities of the laser system that is being used. Thus, the system itself, or a particular subcomponent of the system, can be a limiting factor for a surgical procedure. Moreover, there are many different operational requirements, and many different operational factors that are unique for each ophthalmic laser procedure. Stated differently, the surgical requirements for a laser system will change depending on the particular procedure that is to be followed and on the specific part of the eye where the surgery is to be performed. A consequence of all this is the need for a versatile laser system. 
     With recent improvements in so-called “femtosecond” laser systems, as well as in imaging techniques such as Optical Coherence Tomography (OCT), it is now possible to perform laser surgical procedures deep into the eye. No longer is the cornea the only ophthalmic tissue of interest for laser surgery. Specifically, laser surgical procedures involving the crystalline lens, trabecular meshwork, sclera, vitreous and retina are now being considered for laser surgery. Not surprisingly, each of these different tissues in the eye has its own unique set of operational and anatomical issues. 
     As is well known, the Laser Induced Optical Breakdown (LIOB) of ophthalmic tissue can be efficaciously employed using a pulsed femtosecond laser beam in many different surgical procedures. Alternative tissue interactions with the related effects may use nanosecond or picosecond laser pulses. These procedures include LASIK flap, corneal surgery (e.g. Keretoplasty), refractive corrections, cataract related surgeries, tissue relaxing incisions, glaucoma surgery, and posterior/retinal surgeries. As implied above, each case for LIOB is unique and each procedure has its own particular requirements. Consequently, although similar considerations for the employment of LIOB may be required in each of these different cases/procedures, they will inevitably lead to different operational conclusions. Primarily, the required considerations include: reference datum, laser patient interface, laser beam configuration, focal point placement, and focal point scanning. Importantly, these considerations are interrelated and must be evaluated in the context of other considerations. 
     With the above in mind, the specification for a Maser beam configuration involves the selection of value ranges for operational parameters that will best accomplish the required alteration of a selected target tissue. In particular, based on the specific anatomical features that will be involved, the selection of operational parameters typically includes: 1) choosing an appropriate wavelength for the laser beam; 2) determining “fluence” (energy density) at specific locations along the beam path; 3) selecting a pulse energy; 4) establishing a pulse rate; 5) setting a pulse duration; 6) selecting an appropriate patient interface; and 7) setting a focusing means. 
     Insofar as the focal point placement is concerned, in addition to the anatomical considerations for the type of tissue that is being targeted, it may also be necessary to consider the proximity of the target tissue to a different type of tissue (i.e. the location of a tissue interface). In the event, within permissible cost restraints, the placement of a focal point will preferably be accomplished with the greatest possible precision. In all cases this means that an appropriate, cost effective, base reference datum needs to be established. And, the focal point of the laser beam must be accurately located relative to the base reference datum. For ophthalmic surgeries, such a base reference datum may be a point, a line (e.g. an axis), or a surface. Further, the precision required for establishing the reference datum may need to involve the use of high-level mathematical computations (e.g. expansion series), and/or sophisticated imaging techniques such as OCT. 
     In addition to laser beam configuration and focal point placement, all ophthalmic laser surgeries require the selection of an appropriate scanning operation. Specifically, this selection will generally involve the identification of a focal point path, along with the determinations of the rate of focal point movements and the spacing between adjacent focal points. This may also involve calibration requirements for the entire laser beam generating unit. 
     As an additional consideration for customizing an appropriate laser system for performing an ophthalmic surgery, it is necessary to evaluate the particular patient interface that is to be used. In particular, any distortions of the eye that may be caused when stabilizing the eye with a patient interface (i.e. a contact lens) needs to be accounted for. In some instances the possible adverse effects may be minimal and, therefore, generally acceptable. On the other hand, such distortions may degrade optical qualities of the laser beam to the point where the laser beam becomes ineffective. Suffice to say, the patient interface may be a critical factor for consideration with creating an efficacious surgical laser system. 
     In light of the above, it is an object of the present invention to provide a system and method for performing ophthalmic laser surgery on selected tissue in an eye which allows for customizing the system based on considerations of the specific requirements of a particular surgical procedure. Another object of the present invention is to provide a system and method for performing an ophthalmic laser surgical procedure with a specific patient interface, which allows a user to selectively specify a laser beam configuration, in combination with a selectively established base reference datum, and a selectively identified scanning mode. Yet another object of the present invention is to provide a system and method for performing an ophthalmic laser surgical procedure which is easy to use, is simple to establish and is cost effective. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a multi-mode operable laser system can be customized to perform ophthalmic laser surgery on selected tissue inside an eye. Structurally, the system includes a laser unit, for generating a laser beam, and for focusing the laser beam to a focal point. Preferably, the laser beam is a pulsed femtosecond laser beam that can be configured to perform a Laser Induced Optical Breakdown (LIOB) procedure on the selected target tissue. 
     A mode selector is operationally connected with the laser unit to establish and define an operational mode for the system. This is, done by selecting system functionalities, based on compatibility considerations, that are best suited to perform the required surgical procedure on the selected target tissue. In detail, the operational mode includes: 
     1) a specification of the configuration parameters that are to be used for the laser beam, to include the wavelength of the laser beam, fluence measurements along the laser beam, pulse power, pulse rate and pulse duration; 
     2) a process for establishing a base reference datum in the eye that uses point selection, axis selection, expansion series and/or real-time imaging or detector techniques; and 
     3) a plan for moving the focal point of the laser beam in accordance with a defined scanning procedure, wherein the scanning procedure is based on considerations of the rate of focal spot movement, spacing between focal points, pattern description (e.g. raster or spiral) and calibration points. 
     In addition to the laser unit and the mode selector, the system of the present invention also includes a computer for controlling the laser unit. More specifically, the computer is connected to both the laser unit and to the mode selector. With these connections, the computer is responsive to the mode selector to control the laser unit for the purpose of implementing the operational mode. 
     An additional feature of the system involves considerations for the incorporation of a patient interface. Whenever such an interface is used, its purpose is to stabilize a patient&#39;s eye during ophthalmic surgery. It can happen, however, that the use of an interface can introduce optical distortions into the eye. As a practical consideration, patient interfaces can have different levels of effect, on different areas of the eye, depending on whether they are a planar contact lens, a curved contact lens, a conformable (e.g. water filled) contact lens, or contact free. In the event, they may affect other functional aspects of a customized laser system and, therefore, they must be considered and accounted for in the system set-up and subsequent operations. 
     Due to the plethora of set-up possibilities for different operational modes, and due to the distinct possibility that one particular operational mode may be satisfactory for a a sequence of surgical procedures on respectively different patients, the present invention provides for a so-called default operational mode. Accordingly, the functionalities that constitute the operational mode are preselected. In detail, the configuration parameters for the laser beam are preset, the process for establishing the base reference datum is preset, and the plan for scanning the laser beam&#39;s focal point is also preset. Flexibility for the system, however, is provided by allowing the system user to move from the default status of any functionality, as desired. 
     With the above disclosure in mind, it is to be appreciated that the present invention envisions an operation of the system which includes switching between two different operational modes. For example, consider an integrated operation that requires both a cataract surgery and corneal incisions. In such an integrated operation, the particular procedure that will be deeper in the eye (i.e. the cataract surgery) will likely be done first. In any event, the set-up for both modes of operation can be accomplished prior to starting the integrated operation. 
     In line with earlier disclosure, each procedure (cataract surgery and corneal incisions) will be accomplished separately, and may require different operational modes. In this case, the system set-up initially requires that compatibility considerations be made for an operational mode to perform cataract surgery (i.e. a first operational mode). This involves determining the appropriate operational parameters for the laser beam (e.g. fluence and spot size), establishing a base reference datum, prescribing scanning patterns, and employing a patient interface (e.g. pressure on the eye) for a cataract surgery (e.g. capsulotomy and lens fragmentation). 
     Following the establishment of the first mode of operation (e.g. cataract surgery) a second mode of operation (e.g. corneal incisions) is established by essentially repeating the same compatibility considerations made for the first mode. This requires additional evaluations and appropriate adjustments of the laser beam&#39;s operational parameters and scanning patterns, possibly the selection of a new base reference datum, and a possible modulation of the patient interface. More specifically, insofar as the patient interface is concerned, it can likely happen that only very little pressure needs to be exerted on the eye during the cataract surgery portion of the integrated operation. This minimal pressure is generally preferable in order to minimize posterior and other corneal deformations that could otherwise introduce unwanted distortions of the laser beam. On the other hand, greater pressures are likely required during the corneal incisions portion of the integrated operation. This is so because of the need to stabilize the cornea during corneal incisions, and the fact that, in this portion of the integrated operation, posterior and other corneal deformations will have minimal effect on the procedure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a schematic of the operational components of the present invention; 
         FIG. 2  is a cross section view of an eye identifying possible locations for the performance of surgical procedures envisioned for the present invention; 
         FIG. 3  is a functional flow chart showing the sequence of considerations for the various functionalities involved in a customized set-up of the laser system in accordance with present invention; and 
         FIG. 4  is an operational flow chart to be implemented by a computer for the set-up of a laser system in accordance with the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring initially to  FIG. 1 , a multi-mode system for performing ophthalmic laser surgery in accordance with the present invention is shown and is generally designated  10 . As shown, the system  10  essentially includes a laser unit  12  and a control console  14 . More specifically, the control console  14  includes a computer  16 , an imaging (detector) unit  18  and a mode selector  20 . As intended for the present invention, the control console  14  is used to first set-up and then control the operation of the laser unit  12 . In particular, both set-up and control are directed to the laser beam  22  that is generated by the laser unit  12 . The objective here is to effectively use the laser beam  22  to perform ophthalmic laser surgery on a patient  24 , while the eye  26  is stabilized by a patient interface  28  or eye tracker (not shown). 
     For purposes of the present invention, the laser unit  12  will generate a so-called femtosecond laser that is capable of performing Laser Induced Optical Breakdown (LIOB) on selected tissues inside the eye  26  of the patient  24 . Further, the imaging unit  18  is preferably of a type that is capable of creating three dimensional images of different tissues inside the eye  26  (e.g. an Optical Coherence Tomography (OCT) device). As envisioned for the system  10 , the computer  16  will use input from the imaging unit  18  in its control of the laser unit  12  during laser ophthalmic surgeries in the eye  26 . 
     In  FIG. 2 , the extent to which ophthalmic surgeries can be performed by the system  10  inside the eye  26  will be appreciated. In particular, it will be appreciated that the system  10  envisions using a laser beam  22  to perform LIOB on tissue in the cornea  30 . Further into the eye  26 , it is envisioned that the system  10  can perform ophthalmic surgical procedures in/on the crystalline lens  32  and/or its capsular bag  34 . Still further into the eye  26 , the system  10  can be set-up and controlled to perform ophthalmic surgical procedures in the vitreous  36  of the eye  26  and in/on the retina  38 . Moreover, various references for use in controlling the laser beam  22  can be established. For example, a base reference datum can be a known point in the eye  26  (not specified), a defined axis of the eye  26  (not specified), or a reference surface that is identified by the imaging unit  18 . In the latter case, examples of surfaces being used for a base reference datum include the anterior surface of the cornea  30 , the interface surface  40  between the crystalline lens  32  and the capsular bag  34 , the posterior surface of the patient interface  28  and the interface surface  42  between the vitreous  36  and the retina  38 . Furthermore, with reference to laser beam  22 ′ in  FIG. 2 , it is also to be appreciated that the system  10  envisions performing LIOB surgical procedures inside the sclera  44 , within the trabecular meshwork  46  and on iris tissue  48 . 
     It will be appreciated by the skilled artisan that all tissues in the eye  26 , and specifically including those tissues mentioned above, will have their own unique response to LIOB. Also, depending on the location of the particular tissue in the eye  26  (i.e. the posterior depth of the tissue in the eye  26 ), the laser beam  22  can be operationally affected. Moreover, the operational requirements for particular surgical procedures will differ from one procedure to another. With this in mind, it is clear there is a need to customize the system  10  in a way that will account for all operational requirements (functionalities) each time the system  10  is to be used. 
       FIG. 3  is a functional flow chart that essentially presents the operational compatibility considerations which must be addressed to establish an operational mode during a set-up of the system  10 . Action block  50  shows that the first consideration for the set-up is to identify the particular surgical procedure that is to be performed. As implied above, the procedure may be any of a plethora of procedures that are appropriate for a laser surgical procedure on an eye  26 . Once the procedure has been identified, the next consideration is to identify the patient interface  28  that is to be used (see action block  52 ). As noted above, the selection of the patient interface  28  will depend on how the eye  26  can be best stabilized for the procedure, without introducing unwanted optical distortions in the laser beam  22 . At this point, inquiry block  54  indicates that the system  10  will determine whether a default status is to be used for the configuration of the laser beam  22 . If not, the set-up block  56  requires the user/operator to specify value ranges for configuration parameters of the laser beam  22 . Specifically, these parameters will include the wavelength of the laser beam  22  and its fluence (i.e. energy density) at locations along the beam path of laser beam  22 , as well as the power, pulse rate and pulse duration of the femtosecond pulses in the laser beam  22 . Once the beam configuration has been determined, either by default or set-up, the next consideration concerns whether a default status is to be used for the base reference datum. 
     Inquiry block  58  in  FIG. 3  indicates that if a default status for a base reference datum is not to be used, the user/operator is directed by set-up block  60  to establish an algorithm for such a datum. Essentially this involves selecting a technique that will provide for using a point (not specified here), an axis (not specified here), a line (not specified here), a curve (not specified here), an interface surface (not specified here), or a three dimensional surface (not specified here) as a reference datum. As is well known; this can be accomplished in any of several ways, such as by using a mathematical expansion series. Preferably, however, the present invention envisions the use of an imaging unit  18  that will employ Optical Coherence Tomography (OCT), Scheimpflug, confocal or two-photon imaging techniques. Regardless of the technique that is to be used, however, set-up block  62  requires the selection of a reference datum (e.g. a point, an axis or a surface) that can be subsequently used for control of the laser beam  22 . 
     As a final consideration for the set-up of an operational mode for the system  10 , inquiry block  64  requires identifying a particular scanning procedure for the focal point of the laser beam  22 . In essence, this scanning procedure will establish a path for the focal point of laser beam  22 , and define how it moves along this path. If a preset scanning procedure is not to be used as a default, set-up block  66  requires that settings be made for the rate of focal point movement, and focal point spacing on the focal point path. Additionally, calibration requirements can be attended to. 
     For a final check on the set up of system  10 , action block  68  requires a verification of the operational mode before the particular surgical procedure is to be performed (see action block  70 ). As a practical matter, this verification requires confirmation as to whether the default status is to be used. If the default status is not to be used, the user/operator has the opportunity at this time to recheck and verify that the system  10  has been properly customized for the particular surgical procedure. 
     In accordance with the present invention, the system  10  will be effectively controlled by the computer program product  16  during a surgical procedure. The computer program product  16 , however, will also prompt the user/operator during the set-up of an operational mode, as has been discussed above with reference to  FIG. 3 . For doing this,  FIG. 4  shows a simplified flow chart of the tasks that are to be accomplished by a computer program product, generally designated  72 . Specifically,  FIG. 4  indicates that the first requirement of the computer program product  72  is to select the surgical procedure (action block  74 ). Next, the computer program product  72  determines whether an appropriate patient interface  28  has been approved (inquiry block  76 ). If not, action block  78  requires this be done. Inquiry block  80  then determines whether a preset default status will be used for the selected surgical procedure. If so, action block  82  indicates that the surgical procedure is to be accomplished in accordance with the default operational mode that has been preset in the computer  16 . 
     In the event a default operational mode is not to be followed by the system  10 , action block  84  of the computer program  72  requires that a configuration for the laser beam  22  be specified. Once the laser beam  22  has been properly configured (inquiry block  86 ), the computer program  72  then requires a base reference datum be established (action block  88  and inquiry block  90 ). Next, a scanning plan is identified (action block  92 ). After all of this, inquiry block  94  then effectively determines whether an operational mode has been established for the computer program  72 . If so, the computer program  72  moves to action block  82  and, thereafter, the computer  16  controls the laser unit  12  in its customized operational mode for, performance of the selected surgical procedure. 
     In accordance with the present invention, a computer program product  72  for performing ophthalmic laser surgery on selected tissue in an eye  26  is provided wherein the computer program product  72  comprises program sections for respectively: incorporating a laser unit  12  for generating a laser beam  22 ; defining an operational mode for the system  10 ; specifying, value ranges for configuration parameters for the laser beam  22  for implementation of the operational mode; establishing a base reference datum in the eye  26  for implementation of the operational mode; identifying a scanning procedure for the focal point of the laser beam  22  for implementation of the operational mode; and focusing the laser beam  22  to a focal point, to implement the operational mode by performing Laser Induced Optical Breakdown (LIOB) on the selected tissue. Additionally, the computer program product  72  can include program sections for: choosing a surgical procedure; and selecting a patient interface  28  from a group comprising a planar contact lens, a curved contact lens, a conformable contact lens, a fluid interface, a suction element, or air (no patient interface). 
     While the particular Surgical Laser Unit with Variable Modes of Operation 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.