Abstract:
Embodiments of this invention relate to a system and method for performing laser ophthalmic surgery. The surgical laser system configured to deliver a laser pulse to a patient&#39;s eye comprises a laser engine that includes a compressor configured to compress laser light energy received, the compressor comprising a dispersion or spectrum altering component provided on a computer controlled stage connected to a computing device. A user providing an indication of a desired pulse width received by the computing device causes the computing device to reposition the stage and the component provided thereon, resulting in a different pulse length being transmitted by the laser engine.

Description:
RELATED APPLICATION 
       [0001]    This application is a continuation application under 35 USC §120 of U.S. patent application Ser. No. 14/198,409, filed Mar. 5, 2014, now pending, which claims the benefit of priority to U.S. Provisional Patent Application No. 61/794,651, filed on Mar. 15, 2013, the entire disclosures of the above two applications are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    Field 
         [0003]    Embodiments of this present invention generally relate to laser systems, and more specifically, to the application of laser pulses during surgical procedures such as laser-assisted ophthalmic surgery. 
         [0004]    Background 
         [0005]    Eye surgery is now commonplace with some patients pursuing it as an elective procedure to avoid using contact lenses or glasses and others pursuing it to correct adverse conditions such as cataracts. Moreover, with recent developments in laser technology, laser surgery has become the technique of choice for ophthalmic procedures. Laser eye surgery typically uses different types of laser beams, such as ultraviolet lasers, infrared lasers, and near-infrared, ultra-short pulsed lasers, for various procedures and indications. 
         [0006]    A surgical laser beam is preferred over manual tools like microkeratomes as it can be focused accurately on extremely small amounts of ocular tissue, thereby enhancing precision and reliability. For example, in the commonly-known LASIK (Laser Assisted In Situ Keratomileusis) procedure, an ultra-short pulsed laser is used to cut a corneal flap to expose the corneal stroma for photoablation with an excimer laser. Ultra-short pulsed lasers emit radiation with pulse durations as short as 10 femtoseconds and as long as 3 nanoseconds, and a wavelength between 300 nm and 3000 nm. Besides cutting corneal flaps, ultra-short pulsed lasers are used to perform cataract-related surgical procedures, including capsulorhexis, capsulotomy, as well as softening and/or breaking of the cataractous lens. 
         [0007]    In laser surgery performed with an ultra-short pulsed laser, the laser engine is configured to deliver a laser beam with ultra-short pulse durations (which may be as long as a few nanoseconds or as short as a few femtoseconds) to a patient&#39;s eye. Temporal pulse profile and the pulse width are generally static in that they do not change during a procedure or during different phases of a procedure. Nor do they change when different procedures are performed separately, such as, for example, a capsulorhexis, a capsulotomy, lens fragmentation, corneal incisions, and the like. 
         [0008]    Nevertheless, some issues may arise during different surgical procedures. As a specific example, certain types of ophthalmic incisions may require one type of laser profile, while another type of incision may benefit from a profile having a different pulse length. Conventional laser systems have a limited or non-existent ability to change the laser pulse profile. Where the ability is limited, the laser pulse may be changed to a desired profile, but only after one phase of a surgical procedure is completed with the initial profile. To change the laser&#39;s pulse profile, an operator must manually adjust the positions of certain system components, or make time consuming changes to the components themselves. Once this process is completed, the device may be powered on to commence another phase of the procedure. As may be appreciated, time delay is highly undesirable. 
         [0009]    As such, there is a need for an ultra-short pulsed surgical laser system that overcomes the limited pulse profile capabilities available in conventional systems. In particular, it would be beneficial to offer a more robust ability to alter laser pulse profiles during laser-assisted refractive and cataract surgeries. 
         [0010]    Embodiments of this invention include a surgical laser system and method for performing ophthalmic surgery. The laser system includes a laser engine configured to deliver a pulsed beam to a patient&#39;s eye, wherein the engine includes a compressor configured to compress laser light energy received, the compressor comprising a dispersion or spectrum altering component provided on a computer controlled stage connected to a computing device. A user provides an input to a computing device regarding a desired pulse width causes the computing device to reposition the stage and the component provided thereon, which results in a different pulse length to be transmitted by the laser engine. 
         [0011]    This summary and the following detailed description are merely exemplary, illustrative, and explanatory, and are not intended to limit, but to provide further explanation of the invention as claimed. Additional features and advantages of the invention will be set forth in the descriptions that follow, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description, claims and the appended drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a general overview of a non-UV, ultra-short pulse laser arrangement configured to employ the present design. 
           [0013]      FIG. 2  is a general diagram of the components of a non-UV, ultra-short pulse bulk laser engine in an ophthalmic surgical laser system. 
           [0014]      FIG. 3  illustrates a bulk oscillator that may be employed with the present design. 
           [0015]      FIG. 4  is a pulse stretcher/compressor that may be employed with the present design. 
           [0016]      FIG. 5  shows an amplifier that may be employed with the present design. 
           [0017]      FIG. 6  is a conceptual illustration of a stage having a component positioned thereon usable with the present design. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The drawings and related descriptions of the embodiments have been simplified to illustrate elements that are relevant for a clear understanding of these embodiments, while eliminating various other elements found in conventional collagen shields, ophthalmic patient interfaces, and in laser eye surgical systems. Those of ordinary skill in the art may thus recognize that other elements and/or steps are desirable and/or required in implementing the embodiments that are claimed and described. But, because those other elements and steps are well known in the art, and because they do not necessarily facilitate a better understanding of the embodiments, they are not discussed. This disclosure is directed to all applicable variations, modifications, changes, and implementations known to those skilled in the art. As such, the following detailed descriptions are merely illustrative and exemplary in nature and are not intended to limit the embodiments of the subject matter or the uses of such embodiments. As used in this application, the terms “exemplary” and “illustrative” mean “serving as an example, instance, or illustration.” Any implementation described as exemplary or illustrative is not meant to be construed as preferred or advantageous over other implementations. Further, there is no intention to be bound by any expressed or implied theory presented in the preceding background of the invention, brief summary, or the following detailed description. 
         [0019]      FIG. 1  illustrates a general overview of a laser arrangement configured to employ the present design. From  FIG. 1 , laser engine  100  includes laser source  101  and provides laser light to variable attenuator  102  configured to attenuate the beam, then to energy monitors  103  to monitor beam energy level, and first safety shutter  104  serving as a shutoff device if the beam is unacceptable. Beam steering mirror  105  redirects the resultant laser beam to the beam delivery device  110 , through articulated arm  106  to range finding camera  111 . The range finding camera  111  determines the range needed for the desired focus at the eye  120 . Beam delivery device  110  includes second safety shutter  112  and beam monitor  113 , beam pre-expander  114 , X-Y (position) scanner  115 , and zoom beam expander  116 . Zoom beam expander  116  expands the beam toward IR mirror  117  which reflects and transmits the received beam. Mirror  118  reflects the received beam to video camera  119 , which records the surgical procedure on the eye  120 . IR mirror  117  also reflects the laser light energy to objective lens  121 , which focuses laser light energy to eye  120 . 
         [0020]    In ophthalmic surgery using a pulsed laser beam, non-ultraviolet (UV), ultra-short pulsed laser technology can produce pulsed laser beams having pulse durations measured in the femtoseconds and picoseconds range. An exemplary ultra-short pulsed laser system shown in  FIG. 1  can provide an intrastromal photodisruption technique for reshaping the cornea using a non-UV, ultra-short (e.g., femtosecond pulse duration), pulsed laser beam produced by laser source  101  that propagates through corneal tissue and is focused at a point below the surface of the cornea to photodisrupt stromal tissue at the focal point. 
         [0021]    Although the system may be used to photoalter a variety of materials (e.g., organic, inorganic, or a combination thereof), the system is suitable for ophthalmic applications in one embodiment. The focusing optics, such as beam pre-expander  114 , zoom beam expander  116 , IR mirror  117  and objective lens  121 , direct the pulsed laser beam toward an eye  120  (e.g., onto or into a cornea) for plasma mediated (e.g., non-UV) photoablation of superficial tissue, or into the stroma of the cornea for intrastromal photodisruption of tissue. In this embodiment, the system may also include a lens to change the shape (e.g., flatten or curve) of the cornea prior to scanning the pulsed laser beam toward the eye. The system is capable of generating the pulsed laser beam with physical characteristics similar to those of the laser beams generated by a laser system disclosed in U.S. Pat. Nos. 4,764,930 and 5,993,438, which are incorporated herein. 
         [0022]    The ophthalmic laser system can produce an ultra-short pulsed laser beam for use as an incising laser beam. This pulsed laser beam preferably has laser pulses with durations as long as a few nanoseconds or as short as a few femtoseconds. For intrastromal photodisruption of the tissue, the pulsed laser beam has a wavelength that permits the pulsed laser beam to pass through the cornea without absorption by the corneal tissue. The wavelength of the pulsed laser beam is generally in the range of about 300 nm to about 3000 nm, and the irradiance of the pulsed laser beam for accomplishing photodisruption of stromal tissues at the focal point is typically greater than the threshold for optical breakdown of the tissue. Although a non-UV, ultra-short pulsed laser beam is described in this embodiment, the pulsed laser beam may have other pulse durations and different wavelengths in other embodiments. Further examples of devices employed in performing ophthalmic laser surgery are disclosed in, for example, U.S. Pat. Nos. 5,549,632, 5,984,916, and 6,325,792, which are incorporated here by reference. 
         [0023]      FIG. 2  illustrates general diagram of the components of a non-UV, ultra-short pulse laser engine in an ocular laser surgical system including laser engine  101 . From  FIG. 2 , there is provided an oscillator  201 , a beam stretcher/pulse compressor  202 , and an amplifier  203 . Controller  204  may be provided in the embodiments discussed herein. Lasers producing pulses in the femtosecond/picosecond duration range operate and generate pulses at high peak power levels, and if left unaltered can damage the gain medium. To address this issue, chirped pulse amplification (CPA) is employed wherein the length of pulses are extended or stretched to the picosecond range, resulting in a significant reduction in pulse peak power. From  FIG. 2 , the oscillator  201  generates and outputs a beam of femtosecond laser pulses. The pulse stretcher/compressor  202  extends the duration of the received pulses. Amplifier  203  increases amplitude of the pulses. The pulse stretcher/compressor then recompressed pulses to the femtosecond range prior to delivery. 
         [0024]      FIG. 3  illustrates an oscillator  301  used in a femtosecond bulk laser surgical device. Oscillator  301  includes laser pump  302  which directs laser light energy to focusing lens  303 A and a dichroic mirror  303 B, which both transmits the pump beam but reflects the cavity beam. In one path the cavity beam passes to mirror  309 , aperture  310 , mirror  307 , and SESAM “HR” mirror  308 . As used herein, the term “mirror” or “mirrors” is intended broadly to mean any type of reflective surface or surfaces. The other path from the dichroic mirror  303 B is directed to oscillator glass assembly  304 , horizontally polarized at Brewster&#39;s angle, to mirror  305 , mirror  306 , output coupler  311 , and light energy ultimately passes out of oscillator  301  to mirror  312 , beamsplitter  313 , and pulse stretcher/compressor  202 , not shown in this view. 
         [0025]      FIG. 4  illustrates the components of pulse stretcher/compressor  401 , which receives the beam under half mirror  402 , with light passing to half wave plate  403 , and one of a number of mirrors  404 , over half mirror  405 , to grating  406 , stretcher lens  407 , folding mirror  408 , an stretcher mirror  409 . The beam then travels through elements  408 ,  407  and  406  to half mirror  405  that reflects the beam back to another double-pass through the grating  406  and other elements. The beam then goes over half mirror  405  to elements  404  and  403 . The beam is then gets reflected by half mirror  402  to reflective surface  410 , which provides light energy to Faraday (three port) isolator  411 , configured to receive and provide light energy to and from mirrors  412  and  420 . As shown, mirror  412  provides light energy to half wave plate  413  and to an amplifier (not shown in this view). Light from half mirror  420  passes to mirror  419 , grating  406 , and to compressor retro-reflection assembly  415 , including mirrors  416  and  417 , back through grating  406  and to mirror  418 . Light beam then passes through the grating  406 , retro-reflection assembly  415 , grating  406 , to mirror  419 . The light beam travels over half mirror  420  to mirror  421 , to folding mirror  422 , and to energy wheel  423 , to beam splitters  424  and  425 , fast shutter  426 , and folding mirror to articulating arm  427 . Light from beam splitters  424  and  425  are directed to the other components of the surgical system. 
         [0026]      FIG. 5  illustrates one embodiment of an amplifier  501  in accordance with the design of  FIG. 2A , again including a number of mirrors as well as amp out photodiode  503 , polarizer assembly  504 , mirror  505 , Pockels cell  506 , mirror  507 , and Q-switch photo diode  508 . Also shown is a folding mirror  510 , mirror  511 , mirror  512  on a translation device, amplifier glass assembly  513 , focusing lenses  514 , and pump diode  515 . 
         [0027]    One embodiment of the present design employs the arrangement of  FIGS. 3-5 . Lasers may be employed in the ocular surgical environment to perform a variety of different cuts, such as corneal cuts, capsulotomy cuts, and lens fragmentation cuts. Each of these cuts is optimally performed using a different length pulse. For example, a corneal cut may use pulses in the 400-800 femtoseconds range, while lens fragmentation cuts may use pulses in the 1-5 picoseconds range. It would be advantageous to offer a surgeon an ability to achieve different pulse lengths when the surgeon switches from one desired pulse length to another desired pulse length with little effort required, unlike previous devices wherein extensive and/or manual component repositioning was required to alter pulse length. 
         [0028]    The present design employs computer controlled adjustment of pulse length by changing the dispersion of the pulse compressor, pulse stretcher, or other components or assemblies in the beam path. Detuning the compressor from its optimal operating point tends to lengthen output pulses. One change of the design is to change the effective grating separation. This can be achieved by moving a stage  415   a  with mounted roof mirror  416 - 417  along the beam path indicated. In one embodiment, grating  406  may be repositioned, rotated, or otherwise altered to provide pulses of different lengths. Multiple components illustrated in  FIG. 4  may be placed on stages and moved in a relatively short amount of time. As an example, the device may offer two different pulse lengths, and may offer two different positions for the various components. Components including but not limited to each of the reflective surfaces as well as one or more of grating  406 , stretcher lens  407 , folding mirror  408 , and stretcher mirror  409 , Faraday (three port) isolator  411 , half wave plate  413 , compressor retro-reflection assembly  415 , folding mirror  422 , energy wheel  423 , fast shutter  426 , and/or folding mirror to articulating arm  427  may be positioned on a stage or stages and may be translated and/or rotated to a desired second position to effectuate the second pulse length setting. Alternately, an alternate component may be switched in or out for an existing component to effectuate the second mode of operation. More positions and more pulse length options may be achieved by offering variable positioning of components. Alternatively, a pulse spectral shape or width may be altered (for example, by filtering spectral components within the stretcher or compressor) to adjust temporal pulse length. 
         [0029]    Translation and/or rotation or substitution of components may be achieved using computer controlled motorized stages. During manufacturing or service, pulse length can be determined for more than one position or orientation of a given stage and the setting of both the stage and the resultant pulse length stored in computer memory. During surgery, the user may select a particular pulse length to achieve a particular cut, and the computer  204  may command the stage to translate or rotate or otherwise be repositioned to an available position to achieve desired pulse length. 
         [0030]    A further alternative in  FIG. 4  is to lengthen the distance between grating  406  and compressor retro-reflection assembly  415 , which would lengthen the resultant pulses. Again, a computer controlled stage may be employed to effectuate the desired position of the components. A further alternative would be to substitute a second grating for grating  406 , such that a computer controlled stage may substitute in and/or reposition a second grating (not shown) in place of and/or in a position differing from grating  406 . Other components may be reoriented to effectuate a desired change in position. 
         [0031]    While illustrated with respect to a bulk-grating compressor, the present design may be employed in other types of compressors, including prism based compressors wherein components such as mirror(s), prism(s), and so forth may be provided on stages and adjusted, moved, rotated, translated, or substituted to alter pulse length. Alternately, a grism, generally a combination between a grating and a prism, may be employed in the compressor, and grism components and components associated with the grism may be provided on stages and adjusted, moved, rotated, translated, or substituted using computer control to alter pulse length. 
         [0032]    A further implementation may include a separate dispersion adjustment element added to a compressor, stretcher, or elsewhere in the beam path such as assembly  401  in  FIG. 4 , that adjusts dispersion either continuously or in steps. Use of a dispersion element can change the pulse width when employed with a compressor. Alternately, the dispersion adjustment element can provide a fixed level of dispersion when positioned in the beam path or no dispersion when removed from the beam path. 
         [0033]      FIG. 6  is a general representative drawing of a motorized stage that may be used with the design illustrated in  FIG. 4  and includes components illustrated in  FIG. 4 . Mirrors  416  and  417  are root reflectors positioned on a motorized stage  415   a  configured to move toward and away from grating  406 . Such movement tends to stretch or compress the pulses received. In the beam path illustrated, light passes to grating  406 , mirror  416 , mirror  417 , back to grating  406 , and to mirror  418 , where it is reflected as a retro beam. Computer  601  controls the motorized stage to move in the direction shown. 
         [0034]    Thus, the present design comprises offering a set of components in a laser engine compressor configured to be mechanically repositioned or replaced in order to alter pulse length of the resultant laser output. In one embodiment, at least one component is placed on a mechanical stage connected to a controller such that when a different pulse length is selected, the computer provides a command to move the stage and the component located thereon. Such movement alters the pulse width of the resultant pulse delivered to the patient in a surgical procedure such as a femtosecond laser ocular surgical procedure. 
         [0035]    In another embodiment, multiple components may be repositioned, and in another embodiment, certain components may be replaced with other components or removed form or inserted into the beam path using computer control. Mechanical stages may be employed with any components in a pulse stretcher/pulse compressor or elsewhere in the beam path including but not limited to gratings, prisms, grisms, reflective surfaces or mirrors, half wave plates, lens assemblies or focusing lenses, retro-reflect assemblies, Faraday isolators, folding mirrors, half mirrors, energy wheels, and/or dispersion elements. 
         [0036]    Those of skill in the art will recognize that the step of a method described in connection with an embodiment may be interchanged without departing from the scope of the invention. Those of skill in the art would also understand that information and signals may be represented using any of a variety of different technologies and techniques. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention. An apparatus implementing the techniques or components described herein may be a stand-alone device or may be part of a larger device. 
         [0037]    Although embodiments of this invention are described and pictured in an exemplary form with a certain degree of particularity, describing the best mode contemplated of carrying out the invention, and of the manner and process of making and using it, those skilled in the art will understand that various modifications, alternative constructions, changes, and variations can be made in the ophthalmic interface and method without departing from the spirit or scope of the invention. Thus, it is intended that this invention cover all modifications, alternative constructions, changes, variations, as well as the combinations and arrangements of parts, structures, and steps that come within the spirit and scope of the invention as generally expressed by the following claims and their equivalents.